WorldWideScience

Sample records for high-frequency broadband signals

  1. Photonics-based real-time ultra-high-range-resolution radar with broadband signal generation and processing.

    Science.gov (United States)

    Zhang, Fangzheng; Guo, Qingshui; Pan, Shilong

    2017-10-23

    Real-time and high-resolution target detection is highly desirable in modern radar applications. Electronic techniques have encountered grave difficulties in the development of such radars, which strictly rely on a large instantaneous bandwidth. In this article, a photonics-based real-time high-range-resolution radar is proposed with optical generation and processing of broadband linear frequency modulation (LFM) signals. A broadband LFM signal is generated in the transmitter by photonic frequency quadrupling, and the received echo is de-chirped to a low frequency signal by photonic frequency mixing. The system can operate at a high frequency and a large bandwidth while enabling real-time processing by low-speed analog-to-digital conversion and digital signal processing. A conceptual radar is established. Real-time processing of an 8-GHz LFM signal is achieved with a sampling rate of 500 MSa/s. Accurate distance measurement is implemented with a maximum error of 4 mm within a range of ~3.5 meters. Detection of two targets is demonstrated with a range-resolution as high as 1.875 cm. We believe the proposed radar architecture is a reliable solution to overcome the limitations of current radar on operation bandwidth and processing speed, and it is hopefully to be used in future radars for real-time and high-resolution target detection and imaging.

  2. System and method for detection of dispersed broadband signals

    Science.gov (United States)

    Qian, S.; Dunham, M.E.

    1999-06-08

    A system and method for detecting the presence of dispersed broadband signals in real time are disclosed. The present invention utilizes a bank of matched filters for detecting the received dispersed broadband signals. Each matched filter uses a respective robust time template that has been designed to approximate the dispersed broadband signals of interest, and each time template varies across a spectrum of possible dispersed broadband signal time templates. The received dispersed broadband signal x(t) is received by each of the matched filters, and if one or more matches occurs, then the received data is determined to have signal data of interest. This signal data can then be analyzed and/or transmitted to Earth for analysis, as desired. The system and method of the present invention will prove extremely useful in many fields, including satellite communications, plasma physics, and interstellar research. The varying time templates used in the bank of matched filters are determined as follows. The robust time domain template is assumed to take the form w(t)=A(t)cos[l brace]2[phi](t)[r brace]. Since the instantaneous frequency f(t) is known to be equal to the derivative of the phase [phi](t), the trajectory of a joint time-frequency representation of x(t) is used as an approximation of [phi][prime](t). 10 figs.

  3. Atlantic bottlenose dolphin (Tursiops truncatus) hearing threshold for brief broadband signals.

    Science.gov (United States)

    Au, Whitlow W L; Lemonds, David W; Vlachos, Stephanie; Nachtigall, Paul E; Roitblat, Herbert L

    2002-06-01

    The hearing sensitivity of an Atlantic bottlenose dolphin (Tursiops truncatus) to both pure tones and broadband signals simulating echoes from a 7.62-cm water-filled sphere was measured. Pure tones with frequencies between 40 and 140 kHz in increments of 20 kHz were measured along with broadband thresholds using a stimulus with a center frequency of 97.3 kHz and 88.2 kHz. The pure-tone thresholds were compared with the broadband thresholds by converting the pure-tone threshold intensity to energy flux density. The results indicated that dolphins can detect broadband signals slightly better than a pure-tone signal. The broadband results suggest that an echolocating bottlenose dolphin should be able to detect a 7.62-cm diameter water-filled sphere out to a range of 178 m in a quiet environment.

  4. Signal enhancement by spectral equalization of high frequency broadband signals transmitted through optical fibers

    International Nuclear Information System (INIS)

    Lyons, P.B.; Ogle, J.W.; Holzman, M.A.

    1980-01-01

    A new technique is discussed for enhancing the bandwidth and intensity of high frequency (> 1 GHz) analog, spectrally broad (40 nm) signals transmitted through one kilometer of optical fiber. The existing method for bandwidth enhancement of such a signal uses a very narrow (approx. 1 nm) filter between the fiber and detector to limit bandwidth degradation due to material dispersion. Using this method, most of the available optical intensity is rejected and lost. This new technique replaces the narrow-band filter with a spectral equalizer device which uses a reflection grating to disperse the input signal spectrum and direct it onto a linear array of fibers

  5. Determining of the electric field strength using high frequency broadband measurements

    Directory of Open Access Journals (Sweden)

    Vulević Branislav D.

    2017-01-01

    Full Text Available Exposure of humans to electromagnetic fields of high frequency (above 100 kHz, i.e. radiofrequency radiation from the modern wireless systems, today inevitable is. The purpose of this paper is to highlight the importance of broadband measurements of the electric field of high frequency in order to fast and reliable assessment of human exposure. A practical method of ‘in situ’ measurement the electric field intensity which is related to the frequency range of 3 MHz to 18 GHz, is provided.

  6. Precision and broadband frequency swept laser source based on high-order modulation-sideband injection-locking.

    Science.gov (United States)

    Wei, Fang; Lu, Bin; Wang, Jian; Xu, Dan; Pan, Zhengqing; Chen, Dijun; Cai, Haiwen; Qu, Ronghui

    2015-02-23

    A precision and broadband laser frequency swept technique is experimentally demonstrated. Using synchronous current compensation, a slave diode laser is dynamically injection-locked to a specific high-order modulation-sideband of a narrow-linewidth master laser modulated by an electro-optic modulator (EOM), whose driven radio frequency (RF) signal can be agilely, precisely controlled by a frequency synthesizer, and the high-order modulation-sideband enables multiplied sweep range and tuning rate. By using 5th order sideband injection-locking, the original tuning range of 3 GHz and tuning rate of 0.5 THz/s is multiplied by 5 times to 15 GHz and 2.5 THz/s respectively. The slave laser has a 3 dB-linewidth of 2.5 kHz which is the same to the master laser. The settling time response of a 10 MHz frequency switching is 2.5 µs. By using higher-order modulation-sideband and optimized experiment parameters, an extended sweep range and rate could be expected.

  7. Effects of cations and cholesterol with sphingomyelin membranes investigated by high-resolution broadband sum frequency vibrational spectroscopy

    Science.gov (United States)

    Zhang, Zhen; Feng, Rong-juan; Li, Yi-yi; Liu, Ming-hua; Guo, Yuan

    2017-08-01

    Sphingomyelin(SM) is specifically enriched in the plasma membrane of mammalian cells. Its molecular structure is compose by N-acyl-Derythro-sphingosylphosphorylcholine. The function of the SM related to membrane signaling and protein trafficking are relied on the interactions of the SM, cations, cholesterol and proteins. In this report, the interaction of three different nature SMs, cations and cholesterol at air/aqueous interfaces studied by high-resolution broadband sum frequency vibrational spectroscopy, respectively. Our results shed lights on understanding the relationship between SMs monolayer, cholesterol and Cations.

  8. On the relationship between microbubble fragmentation, deflation and broadband superharmonic signal production.

    Science.gov (United States)

    Lindsey, Brooks D; Rojas, Juan D; Dayton, Paul A

    2015-06-01

    Acoustic angiography imaging of microbubble contrast agents uses the superharmonic energy produced from excited microbubbles and enables high-contrast, high-resolution imaging. However, the exact mechanism by which broadband harmonic energy is produced is not fully understood. To elucidate the role of microbubble shell fragmentation in superharmonic signal production, simultaneous optical and acoustic measurements were performed on individual microbubbles at transmit frequencies from 1.75 to 3.75 MHz and pressures near the shell fragmentation threshold for microbubbles of varying diameter. High-amplitude, broadband superharmonic signals were produced with shell fragmentation, whereas weaker signals (approximately 25% of peak amplitude) were observed in the presence of shrinking bubbles. Furthermore, when populations of stationary microbubbles were imaged with a dual-frequency ultrasound imaging system, a sharper decline in image intensity with respect to frame number was observed for 1-μm bubbles than for 4-μm bubbles. Finally, in a study of two rodents, increasing frame rate from 4 to 7 Hz resulted in decreases in mean steady-state image intensity of 27% at 1000 kPa and 29% at 1300 kPa. Although the existence of superharmonic signals when bubbles shrink has the potential to prolong the imaging efficacy of microbubbles, parameters such as frame rate and peak pressure must be balanced with expected re-perfusion rate to maintain adequate contrast during in vivo imaging. Copyright © 2015. Published by Elsevier Inc.

  9. Prediction of broadband ground-motion time histories: Hybrid low/high-frequency method with correlated random source parameters

    Science.gov (United States)

    Liu, P.; Archuleta, R.J.; Hartzell, S.H.

    2006-01-01

    We present a new method for calculating broadband time histories of ground motion based on a hybrid low-frequency/high-frequency approach with correlated source parameters. Using a finite-difference method we calculate low- frequency synthetics (structure. We also compute broadband synthetics in a 1D velocity model using a frequency-wavenumber method. The low frequencies from the 3D calculation are combined with the high frequencies from the 1D calculation by using matched filtering at a crossover frequency of 1 Hz. The source description, common to both the 1D and 3D synthetics, is based on correlated random distributions for the slip amplitude, rupture velocity, and rise time on the fault. This source description allows for the specification of source parameters independent of any a priori inversion results. In our broadband modeling we include correlation between slip amplitude, rupture velocity, and rise time, as suggested by dynamic fault modeling. The method of using correlated random source parameters is flexible and can be easily modified to adjust to our changing understanding of earthquake ruptures. A realistic attenuation model is common to both the 3D and 1D calculations that form the low- and high-frequency components of the broadband synthetics. The value of Q is a function of the local shear-wave velocity. To produce more accurate high-frequency amplitudes and durations, the 1D synthetics are corrected with a randomized, frequency-dependent radiation pattern. The 1D synthetics are further corrected for local site and nonlinear soil effects by using a 1D nonlinear propagation code and generic velocity structure appropriate for the site’s National Earthquake Hazards Reduction Program (NEHRP) site classification. The entire procedure is validated by comparison with the 1994 Northridge, California, strong ground motion data set. The bias and error found here for response spectral acceleration are similar to the best results that have been published by

  10. High Frequency Components Recovery in Music Signals

    Directory of Open Access Journals (Sweden)

    V. Sebesta

    1999-04-01

    Full Text Available A new technique is presented which improves the subjective quality of band-limited music by recovery of high frequency components. Sequences of harmonics are found in the band-limited signal and these sequences are expanded to the high frequency band to estimate the lost part of spectrum. High frequency signal is generated to match this estimation and is added to the band-limited signal.

  11. Enhanced detection of a low-frequency signal by using broad squeezed light and a bichromatic local oscillator

    Science.gov (United States)

    Li, Wei; Jin, Yuanbin; Yu, Xudong; Zhang, Jing

    2017-08-01

    We experimentally study a protocol of using the broadband high-frequency squeezed vacuum to detect the low-frequency signal. In this scheme, the lower sideband field of the squeezed light carries the low-frequency modulation signal, and the two strong coherent light fields are applied as the bichromatic local oscillator in the homodyne detection to measure the quantum entanglement of the upper and lower sideband for the broadband squeezed light. The power of one of the local oscillators for detecting the upper sideband can be adjusted to optimize the conditional variance in the low-frequency regime by subtracting the photocurrent of the upper sideband field of the squeezed light from that of the lower sideband field. By means of the quantum correlation of the upper and lower sideband for the broadband squeezed light, the low-frequency signal beyond the standard quantum limit is measured. This scheme is appropriate for enhancing the sensitivity of the low-frequency signal by the aid of the broad squeezed light, such as gravitational waves detection, and does not need to directly produce the low-frequency squeezing in an optical parametric process.

  12. Small-signal analysis and particle-in-cell simulations of planar dielectric Cherenkov masers for use as high-frequency, moderate-power broadband amplifiers

    International Nuclear Information System (INIS)

    Carlsten, Bruce E.

    2002-01-01

    A small-signal gain analysis of the planar dielectric Cherenkov maser is presented. The analysis results in a Pierce gain solution, with three traveling-wave modes. The analysis shows that the dielectric Cherenkov maser has a remarkable broadband tuning ability near cutoff, while maintaining reasonable gain rates. Numerical simulations verifying the small-signal gain results are presented, using a particle-in-cell code adapted specifically for planar traveling-wave tubes. An instantaneous bandwidth is numerically shown to be very large, and saturated efficiency for a nominal high-power design is shown to be in the range of standard untapered traveling-wave tubes

  13. Broadband low-frequency sound isolation by lightweight adaptive metamaterials

    Science.gov (United States)

    Liao, Yunhong; Chen, Yangyang; Huang, Guoliang; Zhou, Xiaoming

    2018-03-01

    Blocking broadband low-frequency airborne noises is highly desirable in lots of engineering applications, while it is extremely difficult to be realized with lightweight materials and/or structures. Recently, a new class of lightweight adaptive metamaterials with hybrid shunting circuits has been proposed, demonstrating super broadband structure-borne bandgaps. In this study, we aim at examining their potentials in broadband sound isolation by establishing an analytical model that rigorously combines the piezoelectric dynamic couplings between adaptive metamaterials and acoustics. Sound transmission loss of the adaptive metamaterial is investigated with respect to both the frequency and angular spectrum to demonstrate their sound-insulation effects. We find that efficient sound isolation can indeed be pursued in the broadband bi-spectrum for not only the case of the small resonator's periodicity where only one mode relevant to the mass-spring resonance exists, but also for the large-periodicity scenario, so that the total weight can be even lighter, in which the multiple plate-resonator coupling modes appear. In the latter case, the negative spring stiffness provided by the piezoelectric stack has been utilized to suppress the resonance-induced high acoustic transmission. Such kinds of adaptive metamaterials could open a new approach for broadband noise isolation with extremely lightweight structures.

  14. Broadband measurements of high-frequency electric field levels and exposure ratios determination

    Directory of Open Access Journals (Sweden)

    Vulević Branislav

    2017-01-01

    Full Text Available The exposure of people to high-frequency electromagnetic fields (over 100 kHz that emanate from modern wireless information transmission systems is inevitable in modern times. Due to the rapid development of new technologies, measuring devices and their connection to measuring systems, the first fifteen years of the 21st century are characterized by the appearance of different approaches to measurements. This prompts the need for the assessment of the exposure of people to these fields. The main purpose of this paper is to show how to determine the exposure ratios based on the results of broadband measurements of the high-frequency electric field in the range of 3 MHz to 18 GHz in the environment.

  15. Broadband Signal Enhancement of Seismic Array Data: Application to Long-Period Surface Waves & High Frequency Wavefields

    National Research Council Canada - National Science Library

    Vernon, Frank

    1998-01-01

    .... "Dual-frequency" coherence is useful in identifying overtones and frequency shifts between signals, features which are undetectable by standard coherence measures. We construct a filter to extract only the coherent frequencies from a waveform and show that it significantly increases the signal-noise-ratio for dispersive waveforms.

  16. Hybrid Broadband Ground-Motion Simulations: Combining Long-Period Deterministic Synthetics with High-Frequency Multiple S-to-S Backscattering

    KAUST Repository

    Mai, Paul Martin; Imperatori, W.; Olsen, K. B.

    2010-01-01

    We present a new approach for computing broadband (0-10 Hz) synthetic seismograms by combining high-frequency (HF) scattering with low-frequency (LF) deterministic seismograms, considering finite-fault earthquake rupture models embedded in 3D earth structure. Site-specific HF-scattering Green's functions for a heterogeneous medium with uniformly distributed random isotropic scatterers are convolved with a source-time function that characterizes the temporal evolution of the rupture process. These scatterograms are then reconciled with the LF-deterministic waveforms using a frequency-domain optimization to match both amplitude and phase spectra around the target intersection frequency. The scattering parameters of the medium, scattering attenuation ηs, intrinsic attenuation ηi, and site-kappa, as well as frequency-dependent attenuation, determine waveform and spectral character of the HF-synthetics and thus affect the hybrid broadband seismograms. Applying our methodology to the 1994 Northridge earthquake and validating against near-field recordings at 24 sites, we find that our technique provides realistic broadband waveforms and consistently reproduces LF ground-motion intensities for two independent source descriptions. The least biased results, compared to recorded strong-motion data, are obtained after applying a frequency-dependent site-amplification factor to the broadband simulations. This innovative hybrid ground-motion simulation approach, applicable to any arbitrarily complex earthquake source model, is well suited for seismic hazard analysis and ground-motion estimation.

  17. Hybrid Broadband Ground-Motion Simulations: Combining Long-Period Deterministic Synthetics with High-Frequency Multiple S-to-S Backscattering

    KAUST Repository

    Mai, Paul Martin

    2010-09-20

    We present a new approach for computing broadband (0-10 Hz) synthetic seismograms by combining high-frequency (HF) scattering with low-frequency (LF) deterministic seismograms, considering finite-fault earthquake rupture models embedded in 3D earth structure. Site-specific HF-scattering Green\\'s functions for a heterogeneous medium with uniformly distributed random isotropic scatterers are convolved with a source-time function that characterizes the temporal evolution of the rupture process. These scatterograms are then reconciled with the LF-deterministic waveforms using a frequency-domain optimization to match both amplitude and phase spectra around the target intersection frequency. The scattering parameters of the medium, scattering attenuation ηs, intrinsic attenuation ηi, and site-kappa, as well as frequency-dependent attenuation, determine waveform and spectral character of the HF-synthetics and thus affect the hybrid broadband seismograms. Applying our methodology to the 1994 Northridge earthquake and validating against near-field recordings at 24 sites, we find that our technique provides realistic broadband waveforms and consistently reproduces LF ground-motion intensities for two independent source descriptions. The least biased results, compared to recorded strong-motion data, are obtained after applying a frequency-dependent site-amplification factor to the broadband simulations. This innovative hybrid ground-motion simulation approach, applicable to any arbitrarily complex earthquake source model, is well suited for seismic hazard analysis and ground-motion estimation.

  18. Low frequency phase signal measurement with high frequency squeezing

    OpenAIRE

    Zhai, Zehui; Gao, Jiangrui

    2011-01-01

    We calculate the utility of high-frequency squeezed-state enhanced two-frequency interferometry for low-frequency phase measurement. To use the high-frequency sidebands of the squeezed light, a two-frequency intense laser is used in the interferometry instead of a single-frequency laser as usual. We find that the readout signal can be contaminated by the high-frequency phase vibration, but this is easy to check and avoid. A proof-of-principle experiment is in the reach of modern quantum optic...

  19. Broadband squeezing of quantum noise in a Michelson interferometer with Twin-Signal-Recycling.

    Science.gov (United States)

    Thüring, André; Gräf, Christian; Vahlbruch, Henning; Mehmet, Moritz; Danzmann, Karsten; Schnabel, Roman

    2009-03-15

    Twin-Signal-Recycling (TSR) builds on the resonance doublet of two optically coupled cavities and efficiently enhances the sensitivity of an interferometer at a dedicated signal frequency. We report on what we believe to be the first experimental realization of a TSR Michelson interferometer and also its broadband enhancement by squeezed light injection. The complete setup was stably locked, and a broadband quantum noise reduction of the interferometers shot noise by a factor of up to 4 dB was demonstrated. The system was characterized by measuring its quantum noise spectra for several tunings of the TSR cavities. We found good agreement between the experimental results and numerical simulations.

  20. Ultraflat and broadband optical frequency comb generator based on cascaded two dual-electrode Mach-Zehnder modulators

    Science.gov (United States)

    Qu, Kun; Zhao, Shanghong; Li, Xuan; Tan, Qinggui; Zhu, Zihang

    2018-04-01

    A novel scheme for the generation of ultraflat and broadband optical frequency comb (OFC) is proposed based on cascaded two dual-electrode Mach-Zehnder modulators (DE-MZM). The first DE-MZM can generate a four-comb-line OFC, then the OFC is injected into the second DE-MZM as a carrier, which can increase the number of comb lines. Our modified scheme finally can generate a broadband OFC with high flatness by simply modifying the electrical power and the bias voltage of the DE-MZM. Theoretical analysis and simulation results reveal that a 16-comb-line OFC with a frequency spacing that two times the frequency of the RF signal can be obtained. The power fluctuation of the OFC lines is 0.48 dB and the unwanted-mode suppression ratio (UMSR) can reach 16.5 dB. Additionally, whether the bias drift of the DE-MZMs has little influence on the power fluctuation is also analyzed. These results demonstrate the robustness of our scheme and verify its good accuracy and high stability with perfect flatness.

  1. Broadband unidirectional ultrasound propagation

    Science.gov (United States)

    Sinha, Dipen N.; Pantea, Cristian

    2017-12-12

    A passive, linear arrangement of a sonic crystal-based apparatus and method including a 1D sonic crystal, a nonlinear medium, and an acoustic low-pass filter, for permitting unidirectional broadband ultrasound propagation as a collimated beam for underwater, air or other fluid communication, are described. The signal to be transmitted is first used to modulate a high-frequency ultrasonic carrier wave which is directed into the sonic crystal side of the apparatus. The apparatus processes the modulated signal, whereby the original low-frequency signal exits the apparatus as a collimated beam on the side of the apparatus opposite the sonic crystal. The sonic crystal provides a bandpass acoustic filter through which the modulated high-frequency ultrasonic signal passes, and the nonlinear medium demodulates the modulated signal and recovers the low-frequency sound beam. The low-pass filter removes remaining high-frequency components, and contributes to the unidirectional property of the apparatus.

  2. High frequency electric field levels: An example of determination of measurement uncertainty for broadband measurements

    Directory of Open Access Journals (Sweden)

    Vulević Branislav

    2016-01-01

    Full Text Available Determining high frequency electromagnetic field levels in urban areas represents a very complex task, having in mind the exponential growth of the number of sources embodied in public cellular telephony systems in the past twenty years. The main goal of this paper is a representation of a practical solution in the evaluation of measurement uncertainty for in-situ measurements in the case of spatial averaging. An example of the estimation of the uncertainty for electric field strength broadband measurements in the frequency range from 3 MHz to 18 GHz is presented.

  3. Error Analysis of Clay-Rock Water Content Estimation with Broadband High-Frequency Electromagnetic Sensors—Air Gap Effect

    Science.gov (United States)

    Bore, Thierry; Wagner, Norman; Delepine Lesoille, Sylvie; Taillade, Frederic; Six, Gonzague; Daout, Franck; Placko, Dominique

    2016-01-01

    Broadband electromagnetic frequency or time domain sensor techniques present high potential for quantitative water content monitoring in porous media. Prior to in situ application, the impact of the relationship between the broadband electromagnetic properties of the porous material (clay-rock) and the water content on the frequency or time domain sensor response is required. For this purpose, dielectric properties of intact clay rock samples experimental determined in the frequency range from 1 MHz to 10 GHz were used as input data in 3-D numerical frequency domain finite element field calculations to model the one port broadband frequency or time domain transfer function for a three rods based sensor embedded in the clay-rock. The sensor response in terms of the reflection factor was analyzed in time domain with classical travel time analysis in combination with an empirical model according to Topp equation, as well as the theoretical Lichtenecker and Rother model (LRM) to estimate the volumetric water content. The mixture equation considering the appropriate porosity of the investigated material provide a practical and efficient approach for water content estimation based on classical travel time analysis with the onset-method. The inflection method is not recommended for water content estimation in electrical dispersive and absorptive material. Moreover, the results clearly indicate that effects due to coupling of the sensor to the material cannot be neglected. Coupling problems caused by an air gap lead to dramatic effects on water content estimation, even for submillimeter gaps. Thus, the quantitative determination of the in situ water content requires careful sensor installation in order to reach a perfect probe clay rock coupling. PMID:27096865

  4. Error Analysis of Clay-Rock Water Content Estimation with Broadband High-Frequency Electromagnetic Sensors—Air Gap Effect

    Directory of Open Access Journals (Sweden)

    Thierry Bore

    2016-04-01

    Full Text Available Broadband electromagnetic frequency or time domain sensor techniques present high potential for quantitative water content monitoring in porous media. Prior to in situ application, the impact of the relationship between the broadband electromagnetic properties of the porous material (clay-rock and the water content on the frequency or time domain sensor response is required. For this purpose, dielectric properties of intact clay rock samples experimental determined in the frequency range from 1 MHz to 10 GHz were used as input data in 3-D numerical frequency domain finite element field calculations to model the one port broadband frequency or time domain transfer function for a three rods based sensor embedded in the clay-rock. The sensor response in terms of the reflection factor was analyzed in time domain with classical travel time analysis in combination with an empirical model according to Topp equation, as well as the theoretical Lichtenecker and Rother model (LRM to estimate the volumetric water content. The mixture equation considering the appropriate porosity of the investigated material provide a practical and efficient approach for water content estimation based on classical travel time analysis with the onset-method. The inflection method is not recommended for water content estimation in electrical dispersive and absorptive material. Moreover, the results clearly indicate that effects due to coupling of the sensor to the material cannot be neglected. Coupling problems caused by an air gap lead to dramatic effects on water content estimation, even for submillimeter gaps. Thus, the quantitative determination of the in situ water content requires careful sensor installation in order to reach a perfect probe clay rock coupling.

  5. Error Analysis of Clay-Rock Water Content Estimation with Broadband High-Frequency Electromagnetic Sensors--Air Gap Effect.

    Science.gov (United States)

    Bore, Thierry; Wagner, Norman; Lesoille, Sylvie Delepine; Taillade, Frederic; Six, Gonzague; Daout, Franck; Placko, Dominique

    2016-04-18

    Broadband electromagnetic frequency or time domain sensor techniques present high potential for quantitative water content monitoring in porous media. Prior to in situ application, the impact of the relationship between the broadband electromagnetic properties of the porous material (clay-rock) and the water content on the frequency or time domain sensor response is required. For this purpose, dielectric properties of intact clay rock samples experimental determined in the frequency range from 1 MHz to 10 GHz were used as input data in 3-D numerical frequency domain finite element field calculations to model the one port broadband frequency or time domain transfer function for a three rods based sensor embedded in the clay-rock. The sensor response in terms of the reflection factor was analyzed in time domain with classical travel time analysis in combination with an empirical model according to Topp equation, as well as the theoretical Lichtenecker and Rother model (LRM) to estimate the volumetric water content. The mixture equation considering the appropriate porosity of the investigated material provide a practical and efficient approach for water content estimation based on classical travel time analysis with the onset-method. The inflection method is not recommended for water content estimation in electrical dispersive and absorptive material. Moreover, the results clearly indicate that effects due to coupling of the sensor to the material cannot be neglected. Coupling problems caused by an air gap lead to dramatic effects on water content estimation, even for submillimeter gaps. Thus, the quantitative determination of the in situ water content requires careful sensor installation in order to reach a perfect probe clay rock coupling.

  6. Frequency Doubling Broadband Light in Multiple Crystals

    International Nuclear Information System (INIS)

    Alford, William J.; Smith, Arlee V.

    2000-01-01

    The authors compare frequency doubling of broadband light in a single nonlinear crystal with doubling in five crystals with intercrystal temporal walk off compensation, and with doubling in five crystals adjusted for offset phase matching frequencies. Using a plane-wave, dispersive numerical model of frequency doubling they study the bandwidth of the second harmonic and the conversion efficiency as functions of crystal length and fundamental irradiance. For low irradiance the offset phase matching arrangement has lower efficiency than a single crystal of the same total length but gives a broader second harmonic bandwidth. The walk off compensated arrangement gives both higher conversion efficiency and broader bandwidth than a single crystal. At high irradiance, both multicrystal arrangements improve on the single crystal efficiency while maintaining broad bandwidth

  7. High-frequency signal and noise estimates of CSR GRACE RL04

    Science.gov (United States)

    Bonin, Jennifer A.; Bettadpur, Srinivas; Tapley, Byron D.

    2012-12-01

    A sliding window technique is used to create daily-sampled Gravity Recovery and Climate Experiment (GRACE) solutions with the same background processing as the official CSR RL04 monthly series. By estimating over shorter time spans, more frequent solutions are made using uncorrelated data, allowing for higher frequency resolution in addition to daily sampling. Using these data sets, high-frequency GRACE errors are computed using two different techniques: assuming the GRACE high-frequency signal in a quiet area of the ocean is the true error, and computing the variance of differences between multiple high-frequency GRACE series from different centers. While the signal-to-noise ratios prove to be sufficiently high for confidence at annual and lower frequencies, at frequencies above 3 cycles/year the signal-to-noise ratios in the large hydrological basins looked at here are near 1.0. Comparisons with the GLDAS hydrological model and high frequency GRACE series developed at other centers confirm CSR GRACE RL04's poor ability to accurately and reliably measure hydrological signal above 3-9 cycles/year, due to the low power of the large-scale hydrological signal typical at those frequencies compared to the GRACE errors.

  8. HERA Broadband Feed Design for Low-Frequency Radio Astronomy

    Science.gov (United States)

    Garza, Sierra; Trung, Vincent; Ewall-Wice, Aaron Michael; Li, Jianshu; Hewitt, Jacqueline; Riley, Daniel; Bradley, Richard F.; Makhija, Krishna

    2018-01-01

    As part of the Hydrogen Epoch of Reionization Array (HERA) project, we are designing a broadband low-frequency radio feed to extend the bandwidth from 100-200 MHz to 50-220 MHz. By extending the lower-limit to 50 MHz, we hope to detect the signatures of the first black holes heating the hydrogen gas in the intergalactic medium.The isolation of a very faint signal from vastly brighter foregrounds sets strict requirements on antenna spectral smoothness, polarization purity, forward gain, and internal reflections. We are currently working to meet these requirements with a broad-band sinuous antenna feed suspended over the 14-m parabolic HERA dish, using a combination of measurements and simulations to verify the performance of our design.A sinuous feed has been designed and simulated with Computer Simulation Technology (CST) software. We will present the construction of a prototype sinuous antenna and measurements of its reflection coefficient, S11, including laboratory characterization of baluns. Our measurements agree well with the CST simulations of the antenna’s performance, giving us confidence in our ability to model the feed and ensure that it meets the requirements of a 21cm cosmology measurement.

  9. An 8–18 GHz broadband high power amplifier

    International Nuclear Information System (INIS)

    Wang Lifa; Yang Ruixia; Li Yanlei; Wu Jingfeng

    2011-01-01

    An 8–18 GHz broadband high power amplifier (HPA) with a hybrid integrated circuit (HIC) is designed and fabricated. This HPA is achieved with the use of a 4-fingered micro-strip Lange coupler in a GaAs MMIC process. In order to decrease electromagnetic interference, a multilayer AlN material with good heat dissipation is adopted as the carrier of the power amplifier. When the input power is 25 dBm, the saturated power of the continuous wave (CW) outputted by the power amplifier is more than 39 dBm within the frequency range of 8–13 GHz, while it is more than 38.6 dBm within other frequency ranges. We obtain the peak power output, 39.4 dBm, at the frequency of 11.9 GHz. In the whole frequency band, the power-added efficiency is more than 18%. When the input power is 18 dBm, the small signal gain is 15.7 ± 0.7 dB. The dimensions of the HPA are 25 × 15 × 1.5 mm 3 . (semiconductor integrated circuits)

  10. Radiative cooling and broadband phenomenon in low-frequency waves

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In this paper, we analyze the effects of radiative cooling on the pure baroclinic low-frequency waves under the approximation of equatorial -plane and semi-geostrophic condition. The results show that radiative cooling does not, exclusively, provide the damping effects on the development of low-frequency waves. Under the delicate radiative-convective equilibrium, radiative effects will alter the phase speed and wave period, and bring about the broadband of phase velocity and wave period by adjusting the vertical profiles of diabatic heating. when the intensity of diabatic heating is moderate and appropriate, it is conductive to the development and sustaining of the low-frequency waves and their broadband phenomena, not the larger, the better. The radiative cooling cannot be neglected in order to reach the moderate and appropriate intensity of diabatic heating.

  11. Nanohertz frequency determination for the gravity probe B high frequency superconducting quantum interference device signal.

    Science.gov (United States)

    Salomon, M; Conklin, J W; Kozaczuk, J; Berberian, J E; Keiser, G M; Silbergleit, A S; Worden, P; Santiago, D I

    2011-12-01

    In this paper, we present a method to measure the frequency and the frequency change rate of a digital signal. This method consists of three consecutive algorithms: frequency interpolation, phase differencing, and a third algorithm specifically designed and tested by the authors. The succession of these three algorithms allowed a 5 parts in 10(10) resolution in frequency determination. The algorithm developed by the authors can be applied to a sampled scalar signal such that a model linking the harmonics of its main frequency to the underlying physical phenomenon is available. This method was developed in the framework of the gravity probe B (GP-B) mission. It was applied to the high frequency (HF) component of GP-B's superconducting quantum interference device signal, whose main frequency f(z) is close to the spin frequency of the gyroscopes used in the experiment. A 30 nHz resolution in signal frequency and a 0.1 pHz/s resolution in its decay rate were achieved out of a succession of 1.86 s-long stretches of signal sampled at 2200 Hz. This paper describes the underlying theory of the frequency measurement method as well as its application to GP-B's HF science signal.

  12. Spectrally resolved, broadband frequency response characterization of photodetectors using continuous-wave supercontinuum sources

    Science.gov (United States)

    Choudhury, Vishal; Prakash, Roopa; Nagarjun, K. P.; Supradeepa, V. R.

    2018-02-01

    A simple and powerful method using continuous wave supercontinuum lasers is demonstrated to perform spectrally resolved, broadband frequency response characterization of photodetectors in the NIR Band. In contrast to existing techniques, this method allows for a simple system to achieve the goal, requiring just a standard continuous wave(CW) high-power fiber laser source and an RF spectrum analyzer. From our recent work, we summarize methods to easily convert any high-power fiber laser into a CW supercontinuum. These sources in the time domain exhibit interesting properties all the way down to the femtosecond time scale. This enables measurement of broadband frequency response of photodetectors while the wide optical spectrum of the supercontinuum can be spectrally filtered to obtain this information in a spectrally resolved fashion. The method involves looking at the RF spectrum of the output of a photodetector under test when incident with the supercontinuum. By using prior knowledge of the RF spectrum of the source, the frequency response can be calculated. We utilize two techniques for calibration of the source spectrum, one using a prior measurement and the other relying on a fitted model. Here, we characterize multiple photodetectors from 150MHz bandwidth to >20GHz bandwidth at multiple bands in the NIR region. We utilize a supercontinuum source spanning over 700nm bandwidth from 1300nm to 2000nm. For spectrally resolved measurement, we utilize multiple wavelength bands such as around 1400nm and 1600nm. Interesting behavior was observed in the frequency response of the photodetectors when comparing broadband spectral excitation versus narrower band excitation.

  13. Study and fabrication of a broadband receiver with frequency change for a spectrometer by Nuclear Magnetic Resonance based on pulse in liquids

    International Nuclear Information System (INIS)

    Avril, Robert

    1974-01-01

    The objective of this work has been, by using the pulsed NMR technique, to study and produce a set for the reception of the nuclear precession signal for a broadband (1-60 MHz) spectrometer. In a first part, the author recalls some fundamental elements of pulsed NMR, and discusses the assessment of the precession signal amplitude which can be expected. Then, he gives a detailed description of the various components of the reception chain (modulator, amplifiers, broadband pre-amplifiers, diode gate, frequency changer, synchronous detection), and, through experimentation and measurements, outlines the ease of implementation and adaptation to measurement conditions

  14. Detailed Analysis of Torque Ripple in High Frequency Signal Injection based Sensor less PMSM Drives

    Directory of Open Access Journals (Sweden)

    Ravikumar Setty A.

    2017-01-01

    Full Text Available High Frequency Signal Injection based techniques are robust and well proven to estimate the rotor position from stand still to low speed. However, Injected high frequency signal introduces, high frequency harmonics in the motor phase currents and results in significant Output Torque ripple. There is no detailed analysis exist in the literature, to study the effect of injected signal frequency on Torque ripple. Objective of this work is to study the Torque Ripple resulting from High Frequency signal injection in PMSM motor drives. Detailed MATLAB/Simulink simulations are carried to quantify the Torque ripple at different Signal frequencies.

  15. Real-time and high accuracy frequency measurements for intermediate frequency narrowband signals

    Science.gov (United States)

    Tian, Jing; Meng, Xiaofeng; Nie, Jing; Lin, Liwei

    2018-01-01

    Real-time and accurate measurements of intermediate frequency signals based on microprocessors are difficult due to the computational complexity and limited time constraints. In this paper, a fast and precise methodology based on the sigma-delta modulator is designed and implemented by first generating the twiddle factors using the designed recursive scheme. This scheme requires zero times of multiplications and only half amounts of addition operations by using the discrete Fourier transform (DFT) and the combination of the Rife algorithm and Fourier coefficient interpolation as compared with conventional methods such as DFT and Fast Fourier Transform. Experimentally, when the sampling frequency is 10 MHz, the real-time frequency measurements with intermediate frequency and narrowband signals have a measurement mean squared error of ±2.4 Hz. Furthermore, a single measurement of the whole system only requires approximately 0.3 s to achieve fast iteration, high precision, and less calculation time.

  16. Broadband and high-efficiency vortex beam generator based on a hybrid helix array.

    Science.gov (United States)

    Fang, Chaoqun; Wu, Chao; Gong, Zhijie; Zhao, Song; Sun, Anqi; Wei, Zeyong; Li, Hongqiang

    2018-04-01

    The vortex beam which carries the orbital angular momentum has versatile applications, such as high-resolution imaging, optical communications, and particle manipulation. Generating vortex beams with the Pancharatnam-Berry (PB) phase has drawn considerable attention for its unique spin-to-orbital conversion features. Despite the PB phase being frequency independent, an optical element with broadband high-efficiency circular polarization conversion feature is still needed for the broadband high-efficiency vortex beam generation. In this work, a broadband and high-efficiency vortex beam generator based on the PB phase is built with a hybrid helix array. Such devices can generate vortex beams with arbitrary topological charge. Moreover, vortex beams with opposite topological charge can be generated with an opposite handedness incident beam that propagates backward. The measured efficiency of our device is above 65% for a wide frequency range, with the relative bandwidth of 46.5%.

  17. Time-frequency representation of a highly nonstationary signal via the modified Wigner distribution

    Science.gov (United States)

    Zoladz, T. F.; Jones, J. H.; Jong, J.

    1992-01-01

    A new signal analysis technique called the modified Wigner distribution (MWD) is presented. The new signal processing tool has been very successful in determining time frequency representations of highly non-stationary multicomponent signals in both simulations and trials involving actual Space Shuttle Main Engine (SSME) high frequency data. The MWD departs from the classic Wigner distribution (WD) in that it effectively eliminates the cross coupling among positive frequency components in a multiple component signal. This attribute of the MWD, which prevents the generation of 'phantom' spectral peaks, will undoubtedly increase the utility of the WD for real world signal analysis applications which more often than not involve multicomponent signals.

  18. A non-invasive, quantitative study of broadband spectral responses in human visual cortex.

    Directory of Open Access Journals (Sweden)

    Eline R Kupers

    Full Text Available Currently, non-invasive methods for studying the human brain do not routinely and reliably measure spike-rate-dependent signals, independent of responses such as hemodynamic coupling (fMRI and subthreshold neuronal synchrony (oscillations and event-related potentials. In contrast, invasive methods-microelectrode recordings and electrocorticography (ECoG-have recently measured broadband power elevation in field potentials (~50-200 Hz as a proxy for locally averaged spike rates. Here, we sought to detect and quantify stimulus-related broadband responses using magnetoencephalography (MEG. Extracranial measurements like MEG and EEG have multiple global noise sources and relatively low signal-to-noise ratios; moreover high frequency artifacts from eye movements can be confounded with stimulus design and mistaken for signals originating from brain activity. For these reasons, we developed an automated denoising technique that helps reveal the broadband signal of interest. Subjects viewed 12-Hz contrast-reversing patterns in the left, right, or bilateral visual field. Sensor time series were separated into evoked (12-Hz amplitude and broadband components (60-150 Hz. In all subjects, denoised broadband responses were reliably measured in sensors over occipital cortex, even in trials without microsaccades. The broadband pattern was stimulus-dependent, with greater power contralateral to the stimulus. Because we obtain reliable broadband estimates with short experiments (~20 minutes, and with sufficient signal-to-noise to distinguish responses to different stimuli, we conclude that MEG broadband signals, denoised with our method, offer a practical, non-invasive means for characterizing spike-rate-dependent neural activity for addressing scientific questions about human brain function.

  19. Theory of sum-frequency generation spectroscopy of adsorbed molecules using the density matrix method-broadband vibrational sum-frequency generation and applications

    International Nuclear Information System (INIS)

    Bonn, M; Ueba, H; Wolf, M

    2005-01-01

    A generalized theory of frequency- and time-resolved vibrational sum-frequency generation (SFG) spectroscopy of adsorbates at surfaces is presented using the density matrix formalism. Our theoretical treatment is specifically aimed at addressing issues that accompany the relatively novel SFG approach using broadband infrared pulses. The ultrashort duration of these pulses makes them ideally suited for time-resolved investigations, for which we present a complete theoretical treatment. A second key characteristic of these pulses is their large bandwidth and high intensity, which allow for highly non-linear effects, including vibrational ladder climbing of surface vibrations. We derive general expressions relating the density matrix to SFG spectra, and apply these expressions to specific experimental results by solving the coupled optical Bloch equations of the density matrix elements. Thus, we can theoretically reproduce recent experimentally demonstrated hot band SFG spectra using femtosecond broadband infrared excitation of carbon monoxide (CO) on a Ru(001) surface

  20. Broadband analog to digital conversion with spatial-spectral holography

    International Nuclear Information System (INIS)

    Babbitt, W. Randall; Neifeld, Mark A.; Merkel, Kristian D.

    2007-01-01

    A new approach to broadband photonic-assisted analog-to-digital converter (ADC) technology is proposed and analyzed. The core of the device is a spatial spectral holographic (SSH) material, which can directly record the signals of interest in the frequency domain. An SSH-ADC acts as a frequency-domain stretch processor, which leverages the high performance of conventional ADCs by converting high bandwidth input signals to low bandwidth output signals without loss of information. Analysis of a 10 GHz bandwidth SSH-ADC predicts that 10-bit performance can be achieved with currently available materials and components. SSH-ADC technology is scalable to bandwidths over 100 GHz with recently developed SSH materials. While the SSH-ADC is a transient digitizer, the spatial parallelism of SSH materials can be utilized to enable continuous digitization

  1. Broadband analog to digital conversion with spatial-spectral holography

    Energy Technology Data Exchange (ETDEWEB)

    Babbitt, W. Randall [Spectrum Lab, Montana State University, Bozeman, MT 59717-3510 (United States)]. E-mail: babbitt@physics.montana.edu; Neifeld, Mark A. [Spectrum Lab, Montana State University, Bozeman, MT 59717-3510 (United States); Merkel, Kristian D. [Spectrum Lab, Montana State University, Bozeman, MT 59717-3510 (United States)

    2007-11-15

    A new approach to broadband photonic-assisted analog-to-digital converter (ADC) technology is proposed and analyzed. The core of the device is a spatial spectral holographic (SSH) material, which can directly record the signals of interest in the frequency domain. An SSH-ADC acts as a frequency-domain stretch processor, which leverages the high performance of conventional ADCs by converting high bandwidth input signals to low bandwidth output signals without loss of information. Analysis of a 10 GHz bandwidth SSH-ADC predicts that 10-bit performance can be achieved with currently available materials and components. SSH-ADC technology is scalable to bandwidths over 100 GHz with recently developed SSH materials. While the SSH-ADC is a transient digitizer, the spatial parallelism of SSH materials can be utilized to enable continuous digitization.

  2. High-Frequency Neuromuscular Electrical Stimulation Increases Anabolic Signaling.

    Science.gov (United States)

    Mettler, Joni A; Magee, Dillon M; Doucet, Barbara M

    2018-03-16

    Neuromuscular electrical stimulation (NMES) is commonly used in rehabilitation settings to increase muscle mass and strength. However, the effects of NMES on muscle growth are not clear and no human studies have compared anabolic signaling between low-frequency (LF-) and high-frequency (HF-) NMES. The purpose of this study was to determine the skeletal muscle anabolic signaling response to an acute bout of LF- and HF-NMES. Eleven young healthy volunteers (6 men; 5 women) received an acute bout of LF- (20 Hz) and HF- (60 Hz) NMES. Muscle biopsies were obtained from the vastus lateralis muscle prior to the first NMES treatment and 30-mins following each NMES treatment. Phosphorylation of the following key anabolic signaling proteins was measured by Western blot and proteins are expressed as a ratio of phosphorylated to total: mammalian target of rapamycin (mTOR), p70-S6 kinase 1 (S6K1), and eukaryotic initiation factor 4E binding protein 1 (4E-BP1). Compared to Pre-NMES, phosphorylation of mTOR was upregulated 40.2% for LF-NMES (P = 0.018) and 68.4% for HF-NMES (P 0.05). There were no differences between treatment conditions for 4E-BP1 phosphorylation (P > 0.05). An acute bout of LF- and HF-NMES upregulated anabolic signaling with HF-NMES producing a greater anabolic response compared to LF-NMES, suggesting that HF-stimulation may provide a stronger stimulus for processes that initiate muscle hypertrophy. Additionally, the stimulation frequency parameter should be considered by clinicians in the design of optimal NMES treatment protocols.

  3. Multimodal Broadband Vibrational Sum Frequency Generation (MM-BB-V-SFG) Spectrometer and Microscope.

    Science.gov (United States)

    Lee, Christopher M; Kafle, Kabindra; Huang, Shixin; Kim, Seong H

    2016-01-14

    A broadband sum frequency generation (BB-SFG) spectrometer with multimodal (MM) capabilities was constructed, which could be routinely reconfigured for tabletop experiments in reflection, transmission, and total internal reflection (TIR) geometries, as well as microscopic imaging. The system was constructed using a Ti:sapphire amplifier (800 nm, pulse width = 85 fs, repetition rate = 2 kHz), an optical parameter amplification (OPA) system for production of broadband IR pulses tunable between 1000 and 4000 cm(-1), and two Fabry-Pérot etalons arranged in series for production of narrowband 800 nm pulses. The key feature allowing the MM operation was the nearly collinear alignment of the visible (fixed, 800 nm) and infrared (tunable, 1000-4000 cm(-1)) pulses which were spatially separated. Physical insights discussed in this paper include the comparison of spectral bandwidth produced with 40 and 85 fs pump beams, the improvement of spectral resolution using etalons, the SFG probe volume in bulk analysis, the normalization of SFG signals, the stitching of multiple spectral segments, and the operation in different modes for air/liquid and adsorbate/solid interfaces, bulk samples, as well as spectral imaging combined with principle component analysis (PCA). The SFG spectral features obtained with the MM-BB-SFG system were compared with those obtained with picosecond-scanning-SFG system and high-resolution BB-SFG system (HR-BB-SFG) for dimethyl sulfoxide, α-pinene, and various samples containing cellulose (purified commercial products, Cladophora cell wall, cotton and flax fibers, and onion epidermis cell wall).

  4. High efficiency and broadband acoustic diodes

    Science.gov (United States)

    Fu, Congyi; Wang, Bohan; Zhao, Tianfei; Chen, C. Q.

    2018-01-01

    Energy transmission efficiency and working bandwidth are the two major factors limiting the application of current acoustic diodes (ADs). This letter presents a design of high efficiency and broadband acoustic diodes composed of a nonlinear frequency converter and a linear wave filter. The converter consists of two masses connected by a bilinear spring with asymmetric tension and compression stiffness. The wave filter is a linear mass-spring lattice (sonic crystal). Both numerical simulation and experiment show that the energy transmission efficiency of the acoustic diode can be improved by as much as two orders of magnitude, reaching about 61%. Moreover, the primary working band width of the AD is about two times of the cut-off frequency of the sonic crystal filter. The cut-off frequency dependent working band of the AD implies that the developed AD can be scaled up or down from macro-scale to micro- and nano-scale.

  5. Broadband sub-THz spectroscopy modules integrated in 65-nm CMOS technology

    NARCIS (Netherlands)

    Matters-Kammerer, M.K.; van Goor, D.; Tripodi, L.

    2017-01-01

    The design and characterization of a broadband 20-480 GHz continuously tuneable on-chip spectrometer based on non-linear transmission lines in 65-nm CMOS technology is presented. The design procedure of the sampler that detects the ultra-broadband signal from the transmitter in time and frequency

  6. Exposure estimates based on broadband elf magnetic field measurements versus the ICNIRP multiple frequency rule

    International Nuclear Information System (INIS)

    Paniagua, Jesus M.; Rufo, Montana; Jimenez, Antonio; Pachon, Fernando T.; Carrero, Julian

    2015-01-01

    The evaluation of exposure to extremely low-frequency (ELF) magnetic fields using broadband measurement techniques gives satisfactory results when the field has essentially a single frequency. Nevertheless, magnetic fields are in most cases distorted by harmonic components. This work analyses the harmonic components of the ELF magnetic field in an outdoor urban context and compares the evaluation of the exposure based on broadband measurements with that based on spectral analysis. The multiple frequency rule of the International Commission on Non-ionizing Radiation Protection (ICNIRP) regulatory guidelines was applied. With the 1998 ICNIRP guideline, harmonics dominated the exposure with a 55 % contribution. With the 2010 ICNIRP guideline, however, the primary frequency dominated the exposure with a 78 % contribution. Values of the exposure based on spectral analysis were significantly higher than those based on broadband measurements. Hence, it is clearly necessary to determine the harmonic components of the ELF magnetic field to assess exposure in urban contexts. (authors)

  7. Spectral integration of broadband signals in diotoc and dichotic masking experiments

    NARCIS (Netherlands)

    Langhans, A.; Kohlrausch, A.G.

    1992-01-01

    The method of Gässler [Acustica 4, 408–414 (1954)] was used to measure the audibility of multicomponent signals as a function of their bandwidth against a broadband, white-noise masker. Test signals were composed of 1 to 41 sinusoids with a spectral spacing of 10 Hz and were always spectrally

  8. Discrete-time nonlinear damping backstepping control with observers for rejection of low and high frequency disturbances

    Science.gov (United States)

    Kim, Wonhee; Chen, Xu; Lee, Youngwoo; Chung, Chung Choo; Tomizuka, Masayoshi

    2018-05-01

    A discrete-time backstepping control algorithm is proposed for reference tracking of systems affected by both broadband disturbances at low frequencies and narrow band disturbances at high frequencies. A discrete time DOB, which is constructed based on infinite impulse response filters is applied to compensate for narrow band disturbances at high frequencies. A discrete-time nonlinear damping backstepping controller with an augmented observer is proposed to track the desired output and to compensate for low frequency broadband disturbances along with a disturbance observer, for rejecting narrow band high frequency disturbances. This combination has the merit of simultaneously compensating both broadband disturbances at low frequencies and narrow band disturbances at high frequencies. The performance of the proposed method is validated via experiments.

  9. Frequency-comb-assisted broadband precision spectroscopy with cascaded diode lasers

    DEFF Research Database (Denmark)

    Liu, Junqiu; Brasch, Victor; Pfeiffer, Martin H. P.

    2016-01-01

    Frequency-comb-assisted diode laser spectroscopy, employing both the accuracy of an optical frequency comb and the broad wavelength tuning range of a tunable diode laser, has been widely used in many applications. In this Letter, we present a novel method using cascaded frequency agile diode lasers......, which allows us to extend the measurement bandwidth to 37.4 THz (1355-1630 nm) at megahertz resolution with scanning speeds above 1 THz/s. It is demonstrated as a useful tool to characterize a broadband spectrum for molecular spectroscopy, and in particular it enables us to characterize the dispersion...

  10. Piezoelectric Nanotube Array for Broadband High-Frequency Ultrasonic Transducer.

    Science.gov (United States)

    Liew, Weng Heng; Yao, Kui; Chen, Shuting; Tay, Francis Eng Hock

    2018-03-01

    Piezoelectric materials are vital in determining ultrasonic transducer and imaging performance as they offer the function for conversion between mechanical and electrical energy. Ultrasonic transducers with high-frequency operation suffer from performance degradation and fabrication difficulty of the demanded piezoelectric materials. Hence, we propose 1-D polymeric piezoelectric nanostructure with controlled nanoscale features to overcome the technical limitations of high-frequency ultrasonic transducers. For the first time, we demonstrate the integration of a well-aligned piezoelectric nanotube array to produce a high-frequency ultrasonic transducer with outstanding performance. We find that nanoconfinement-induced polarization orientation and unique nanotube structure lead to significantly improved piezoelectric and ultrasonic transducing performance over the conventional piezoelectric thin film. A large bandwidth, 126% (-6 dB), is achieved at high center frequency, 108 MHz. Transmission sensitivity of nanotube array is found to be 46% higher than that of the monolithic thin film transducer attributed to the improved electromechanical coupling effectiveness and impedance match. We further demonstrate high-resolution scanning, ultrasonic imaging, and photoacoustic imaging using the obtained nanotube array transducers, which is valuable for biomedical imaging applications in the future.

  11. Broadband photonic single sideband frequency up-converter based on the cross polarization modulation effect in a semiconductor optical amplifier for radio-over-fiber systems.

    Science.gov (United States)

    Lee, Seung-Hun; Kim, Hyoung-Jun; Song, Jong-In

    2014-01-13

    A broadband photonic single sideband (SSB) frequency up-converter based on the cross polarization modulation (XPolM) effect in a semiconductor optical amplifier (SOA) is proposed and experimentally demonstrated. An optical radio frequency (RF) signal in the form of an optical single sideband (OSSB) is generated by the photonic SSB frequency up-converter to solve the power fading problem caused by fiber chromatic dispersion. The generated OSSB RF signal has almost identical optical carrier power and optical sideband power. This SSB frequency up-conversion scheme shows an almost flat electrical RF power response as a function of the RF frequency in a range from 31 GHz to 75 GHz after 40 km single mode fiber (SMF) transmission. The photonic SSB frequency up-conversion technique shows negligible phase noise degradation. The phase noise of the up-converted RF signal at 49 GHz for an offset of 10 kHz is -93.17 dBc/Hz. Linearity analysis shows that the photonic SSB frequency up-converter has a spurious free dynamic range (SFDR) value of 79.51 dB · Hz(2/3).

  12. An improved phase-locked loop method for automatic resonance frequency tracing based on static capacitance broadband compensation for a high-power ultrasonic transducer.

    Science.gov (United States)

    Dong, Hui-juan; Wu, Jian; Zhang, Guang-yu; Wu, Han-fu

    2012-02-01

    The phase-locked loop (PLL) method is widely used for automatic resonance frequency tracing (ARFT) of high-power ultrasonic transducers, which are usually vibrating systems with high mechanical quality factor (Qm). However, a heavily-loaded transducer usually has a low Qm because the load has a large mechanical loss. In this paper, a series of theoretical analyses is carried out to detail why the traditional PLL method could cause serious frequency tracing problems, including loss of lock, antiresonance frequency tracing, and large tracing errors. The authors propose an improved ARFT method based on static capacitance broadband compensation (SCBC), which is able to address these problems. Experiments using a generator based on the novel method were carried out using crude oil as the transducer load. The results obtained have demonstrated the effectiveness of the novel method, compared with the conventional PLL method, in terms of improved tracing accuracy (±9 Hz) and immunity to antiresonance frequency tracing and loss of lock.

  13. ULF wave effects on high frequency signal propagation through the ionosphere

    Directory of Open Access Journals (Sweden)

    C. L. Waters

    2009-07-01

    Full Text Available Variations in the total electron content (TEC of the ionosphere alter the propagation characteristics of EM radiation for frequencies above a few megahertz (MHz. Spatial and temporal variations of the ionosphere TEC influence highly sensitive, ground based spatial measurements such as those used in radio astronomy and Global Positioning System (GPS applications. In this paper we estimate the magnitudes of the changes in TEC and the time delays of high frequency signals introduced by variations in the ionosphere electron density caused by the natural spectrum of ultra-low frequency (ULF wave activity that originates in near-Earth space. The time delays and associated phase shifts depend on the frequency, spatial structure and amplitude of the ULF waves.

  14. An articulated predictive model for fluid-free artificial basilar membrane as broadband frequency sensor

    Science.gov (United States)

    Ahmed, Riaz; Banerjee, Sourav

    2018-02-01

    In this article, an extremely versatile predictive model for a newly developed Basilar meta-Membrane (BM2) sensors is reported with variable engineering parameters that contribute to it's frequency selection capabilities. The predictive model reported herein is for advancement over existing method by incorporating versatile and nonhomogeneous (e.g. functionally graded) model parameters that could not only exploit the possibilities of creating complex combinations of broadband frequency sensors but also explain the unique unexplained physical phenomenon that prevails in BM2, e.g. tailgating waves. In recent years, few notable attempts were made to fabricate the artificial basilar membrane, mimicking the mechanics of the human cochlea within a very short range of frequencies. To explain the operation of these sensors a few models were proposed. But, we fundamentally argue the "fabrication to explanation" approach and proposed the model driven predictive design process for the design any (BM2) as broadband sensors. Inspired by the physics of basilar membrane, frequency domain predictive model is proposed where both the material and geometrical parameters can be arbitrarily varied. Broadband frequency is applicable in many fields of science, engineering and technology, such as, sensors for chemical, biological and acoustic applications. With the proposed model, which is three times faster than its FEM counterpart, it is possible to alter the attributes of the selected length of the designed sensor using complex combinations of model parameters, based on target frequency applications. Finally, the tailgating wave peaks in the artificial basilar membranes that prevails in the previously reported experimental studies are also explained using the proposed model.

  15. Demonstration of the frequency modulation of optical signals with a high frequency deviation parameter

    International Nuclear Information System (INIS)

    Shamray, A V; Kozlov, A S; Il'ichev, I V; Petrov, M P

    2008-01-01

    A new type of an integrated optical modulator for the frequency coding of optical signals is developed and fabricated. The modulator operation is based on the original technology of the electric control of a Bragg grating. The frequency modulation of an optical signal with the frequency deviation of 25 GHz is demonstrated experimentally. The modular was used to transfer the ASCII code through an optical fibre. (optical communication)

  16. Broadband true time delay for microwave signal processing, using slow light based on stimulated Brillouin scattering in optical fibers.

    Science.gov (United States)

    Chin, Sanghoon; Thévenaz, Luc; Sancho, Juan; Sales, Salvador; Capmany, José; Berger, Perrine; Bourderionnet, Jérôme; Dolfi, Daniel

    2010-10-11

    We experimentally demonstrate a novel technique to process broadband microwave signals, using all-optically tunable true time delay in optical fibers. The configuration to achieve true time delay basically consists of two main stages: photonic RF phase shifter and slow light, based on stimulated Brillouin scattering in fibers. Dispersion properties of fibers are controlled, separately at optical carrier frequency and in the vicinity of microwave signal bandwidth. This way time delay induced within the signal bandwidth can be manipulated to correctly act as true time delay with a proper phase compensation introduced to the optical carrier. We completely analyzed the generated true time delay as a promising solution to feed phased array antenna for radar systems and to develop dynamically reconfigurable microwave photonic filters.

  17. A broadband high-efficiency Doherty power amplifier using symmetrical devices

    Science.gov (United States)

    Cheng, Zhiqun; Zhang, Ming; Li, Jiangzhou; Liu, Guohua

    2018-04-01

    This paper proposes a method for broadband and high-efficiency amplification of Doherty power amplifier (DPA) using symmetric devices. In order to achieve the perfect load modulation, the carrier amplifier output circuit total power length is designed to odd multiple of 90°, and the peak amplifier output total power length is designed to even multiple of 180°. The proposed method is demonstrated by designing a broadband high-efficiency DPA using identical 10-W packaged GaN HEMT devices. Measurement results show that over 51% drain efficiency is achieved at 6-dB back-off power, over the frequency band of 1.9–2.4 GHz. Project supported by the National Natural Science Foundation of China (No. 60123456), the Zhejiang Provincial Natural Science Foundation of China (No. LZ16F010001), and the Zhejiang Provincial Public Technology Research Project (No. 2016C31070).

  18. The effect of extending high-frequency bandwidth on the acceptable noise level (ANL) of hearing-impaired listeners.

    Science.gov (United States)

    Johnson, Earl; Ricketts, Todd; Hornsby, Benjamin

    2009-01-01

    This study examined the effects of extending high-frequency bandwidth, for both a speech signal and a background noise, on the acceptable signal-to-noise ratio (SNR) of listeners with mild sensorineural hearing loss through utilization of the Acceptable Noise Level (ANL) procedure. In addition to extending high-frequency bandwidth, the effects of reverberation time and background noise type and shape were also examined. The study results showed a significant increase in the mean ANL (i.e. participants requested a better SNR for an acceptable listening situation) when high-frequency bandwidth was extended from 3 to 9 kHz and from 6 to 9 kHz. No change in the ANL of study participants was observed as a result of isolated modification to reverberation time or background noise stimulus. An interaction effect, however, of reverberation time and background noise stimulus was demonstrated. These findings may have implications for future design of hearing aid memory programs for listening to speech in the presence of broadband background noise.

  19. MONITORING HIGH-FREQUENCY OCEAN SIGNALS USING LOW-COST GNSS/IMU BUOYS

    Directory of Open Access Journals (Sweden)

    Y.-L. Huang

    2016-06-01

    Full Text Available In oceans there are different ocean signals covering the multi-frequencies including tsunami, meteotsunami, storm surge, as sea level change, and currents. These signals have the direct and significant impact on the economy and life of human-beings. Therefore, measuring ocean signals accurately becomes more and more important and necessary. Nowadays, there are many techniques and methods commonly used for monitoring oceans, but each has its limitation. For example, tide gauges only measure sea level relative to benchmarks and are disturbed unevenly, and satellite altimeter measurements are not continuous and inaccurate near coastal oceans. In addition, high-frequency ocean signals such as tsunami and meteotsunami cannot be sufficiently detected by 6-minutes tide gauge measurements or 10-day sampled altimetry data. Moreover, traditional accelerometer buoy is heavy, expensive and the low-frequency noise caused by the instrument is unavoidable. In this study, a small, low-cost and self-assembly autonomous Inertial Measurement Unit (IMU that independently collects continuous acceleration and angular velocity data is mounted on a GNSS buoy to provide the positions and tilts of the moving buoy. The main idea is to integrate the Differential GNSS (DGNSS or Precise Point Positioning (PPP solutions with IMU data, and then evaluate the performance by comparing with in situ tide gauges. The validation experiments conducted in the NCKU Tainan Hydraulics Laboratory showed that GNSS and IMU both can detect the simulated regular wave frequency and height, and the field experiments in the Anping Harbor, Tainan, Taiwan showed that the low-cost GNSS buoy has an excellent ability to observe significant wave heights in amplitude and frequency.

  20. Broadband Electrophysiological Dynamics Contribute to Global Resting-State fMRI Signal.

    Science.gov (United States)

    Wen, Haiguang; Liu, Zhongming

    2016-06-01

    Spontaneous activity observed with resting-state fMRI is used widely to uncover the brain's intrinsic functional networks in health and disease. Although many networks appear modular and specific, global and nonspecific fMRI fluctuations also exist and both pose a challenge and present an opportunity for characterizing and understanding brain networks. Here, we used a multimodal approach to investigate the neural correlates to the global fMRI signal in the resting state. Like fMRI, resting-state power fluctuations of broadband and arrhythmic, or scale-free, macaque electrocorticography and human magnetoencephalography activity were correlated globally. The power fluctuations of scale-free human electroencephalography (EEG) were coupled with the global component of simultaneously acquired resting-state fMRI, with the global hemodynamic change lagging the broadband spectral change of EEG by ∼5 s. The levels of global and nonspecific fluctuation and synchronization in scale-free population activity also varied across and depended on arousal states. Together, these results suggest that the neural origin of global resting-state fMRI activity is the broadband power fluctuation in scale-free population activity observable with macroscopic electrical or magnetic recordings. Moreover, the global fluctuation in neurophysiological and hemodynamic activity is likely modulated through diffuse neuromodulation pathways that govern arousal states and vigilance levels. This study provides new insights into the neural origin of resting-state fMRI. Results demonstrate that the broadband power fluctuation of scale-free electrophysiology is globally synchronized and directly coupled with the global component of spontaneous fMRI signals, in contrast to modularly synchronized fluctuations in oscillatory neural activity. These findings lead to a new hypothesis that scale-free and oscillatory neural processes account for global and modular patterns of functional connectivity observed

  1. Frequency-domain method for separating signal and noise

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new method for separation of signal and noise (SSN) is put forward. Frequency is redefined according to the features of signal and its derivative in the sampl ing time interval, thus double orthogonal basis (DOB) is constructed so that a signal can be precisely signified with a linear combination of low-frequency DOB . Under joint consideration in time domain (TD) and frequency domain (FD), a method on SSN with high accuracy is derived and a matched algorithm is designed and analyzed. This method is applicable to SSN in multiple frequency bands, and convenient in applying signal characteristics in TD and FD synthetically with highe raccuracy.

  2. High-resolution broadband terahertz spectroscopy via electronic heterodyne detection of photonically generated terahertz frequency comb.

    Science.gov (United States)

    Pavelyev, D G; Skryl, A S; Bakunov, M I

    2014-10-01

    We report an alternative approach to the terahertz frequency-comb spectroscopy (TFCS) based on nonlinear mixing of a photonically generated terahertz pulse train with a continuous wave signal from an electronic synthesizer. A superlattice is used as a nonlinear mixer. Unlike the standard TFCS technique, this approach does not require a complex double-laser system but retains the advantages of TFCS-high spectral resolution and wide bandwidth.

  3. Broadband frequency ECR ion source concepts with large resonant plasma volumes

    International Nuclear Information System (INIS)

    Alton, G.D.

    1995-01-01

    New techniques are proposed for enhancing the performances of ECR ion sources. The techniques are based on the use of high-power, variable-frequency, multiple-discrete-frequency, or broadband microwave radiation, derived from standard TWT technology, to effect large resonant ''volume'' ECR sources. The creation of a large ECR plasma ''volume'' permits coupling of more power into the plasma, resulting in the heating of a much larger electron population to higher energies, the effect of which is to produce higher charge state distributions and much higher intensities within a particular charge state than possible in present forms of the ECR ion source. If successful, these developments could significantly impact future accelerator designs and accelerator-based, heavy-ion-research programs by providing multiply-charged ion beams with the energies and intensities required for nuclear physics research from existing ECR ion sources. The methods described in this article can be used to retrofit any ECR ion source predicated on B-minimum plasma confinement techniques

  4. Magnetically levitated autoparametric broadband vibration energy harvesting

    International Nuclear Information System (INIS)

    Kurmann, L.; Jia, Y.; Manoli, Y.; Woias, P.

    2016-01-01

    Some of the lingering challenges within the current paradigm of vibration energy harvesting (VEH) involve narrow operational frequency range and the inevitable non-resonant response from broadband noise excitations. Such VEHs are only suitable for limited applications with fixed sinusoidal vibration, and fail to capture a large spectrum of the real world vibration. Various arraying designs, frequency tuning schemes and nonlinear vibratory approaches have only yielded modest enhancements. To fundamentally address this, the paper proposes and explores the potentials in using highly nonlinear magnetic spring force to activate an autoparametric oscillator, in order to realize an inherently broadband resonant system. Analytical and numerical modelling illustrate that high spring nonlinearity derived from magnetic levitation helps to promote the 2:1 internal frequency matching required to activate parametric resonance. At the right internal parameters, the resulting system can intrinsically exhibit semi-resonant response regardless of the bandwidth of the input vibration, including broadband white noise excitation. (paper)

  5. Towards convergence of wireless and wireline signal transport in broadband access networks

    DEFF Research Database (Denmark)

    Yu, Xianbin; Prince, Kamau; Tafur Monroy, Idelfonso

    2010-01-01

    Hybrid optical wireless access networks are to play an important role in the realization of the vision of delivery of broadband services to the end-user any time, anywhere and at affordable costs. We present results of experiments conducted over a field deployed optical fibre links we successfull...... demonstrated converged wireless and wireline signal transport over a common fibre infrastructure. The type of signal used in this field deployed experiments cover WiMax, Impulse-radio ultra-wideband (UWB) and coherent transmission of baseband QPSK and radio-over-fibre signals....

  6. Broadband Amplification of Low-Terahertz Signals Using Axis-Encircling Electrons in a Helically Corrugated Interaction Region

    Science.gov (United States)

    He, W.; Donaldson, C. R.; Zhang, L.; Ronald, K.; Phelps, A. D. R.; Cross, A. W.

    2017-11-01

    Experimental results are presented of a broadband, high power, gyrotron traveling wave amplifier (gyro-TWA) operating in the (75-110)-GHz frequency band and based on a helically corrugated interaction region. The second harmonic cyclotron mode of a 55-keV, 1.5-A, axis-encircling electron beam is used to resonantly interact with a traveling TE21 -like eigenwave achieving broadband amplification. The gyro-TWA demonstrates a 3-dB gain bandwidth of at least 5.5 GHz in the experimental measurement with 9 GHz predicted for a wideband drive source with a measured unsaturated output power of 3.4 kW and gain of 36-38 dB. The approach may allow a gyro-TWA to operate at 1 THz.

  7. Experimental study of a high-current FEM with a broadband microwave system

    Energy Technology Data Exchange (ETDEWEB)

    Denisov, G.G.; Bratman, V.L.; Ginzburg, N.S. [Institute of Applied Physics, Nizhny Novgorod (Russian Federation)] [and others

    1995-12-31

    One of the main features of FELs and FEMs is the possibility of fast and wideband tuning of the resonant frequency of active media, which can be provided by changing the particle energy. For a frequency adjustable FEM-oscillator, a broadband microwave system, which is simply combined with an electron-optical FEM system and consists of an oversized waveguide and reflectors based on the microwave beams multiplication effect has been proposed and studied successfully in {open_quotes}cold{close_quotes} measurements. Here, the operating ability of a cavity, that includes some key elements of the broadband microwave system, was tested in the presence of an electron beam. To provide large particle oscillation velocities in a moderate undulator field and the presence of a guide magnetic field, the FEM operating regime of double resonance was chosen. In this regime the cyclotron as well as undulator resonance conditions were satisfied. The FEM-oscillator was investigated experimentally on a high-current accelerator {open_quotes}Sinus-6{close_quotes} that forms an electron beam with particle energy 500keV and pulse duration 25ns. The aperture with a diameter 2.5mm at the center of the anode allows to pass through only the central fraction of the electron beam with a current about 100A and a small spread of longitudinal velocities of the particles. Operating transverse velocity was pumped into the electron beam in the pulse plane undulator of a 2.4cm period. The cavity with a frequency near 45GHz consists of a square waveguide and two reflectors. The broadband up-stream reflector based on the multiplication effect had the power reflectivity coefficient more than 90% in the frequency band 10% for the H{sup 10} wave of the square waveguide with the maximum about 100% at a frequency 45GHz. The down-stream narrow-band Bragg reflector had the power reflection coefficient approximately 80% in the frequency band of 4% near 45GHz for the operating mode.

  8. Broadband Microwave Wireless Power Transfer for Weak-Signal and Multipath Environments

    Science.gov (United States)

    Barton, Richard J.

    2014-01-01

    In this paper, we study the potential benefits of using relatively broadband wireless power transmission WPT strategies in both weak-signal and multipath environments where traditional narrowband strategies can be very inefficient. The paper is primarily a theoretical and analytical treatment of the problem that attempts to derive results that are widely applicable to many different WPT applications, including space solar power SSP.

  9. Dissemination of optical-comb-based ultra-broadband frequency reference through a fiber network.

    Science.gov (United States)

    Nagano, Shigeo; Kumagai, Motohiro; Li, Ying; Ido, Tetsuya; Ishii, Shoken; Mizutani, Kohei; Aoki, Makoto; Otsuka, Ryohei; Hanado, Yuko

    2016-08-22

    We disseminated an ultra-broadband optical frequency reference based on a femtosecond (fs)-laser optical comb through a kilometer-scale fiber link. Its spectrum ranged from 1160 nm to 2180 nm without additional fs-laser combs at the end of the link. By employing a fiber-induced phase noise cancellation technique, the linewidth and fractional frequency instability attained for all disseminated comb modes were of order 1 Hz and 10-18 in a 5000 s averaging time. The ultra-broad optical frequency reference, for which absolute frequency is traceable to Japan Standard Time, was applied in the frequency stabilization of an injection-seeded Q-switched 2051 nm pulse laser for a coherent light detection and ranging LIDAR system.

  10. High intensity signal of the posterior pituitary. A study with horizontal direction of frequency-encoding and fat suppression MR techniques

    International Nuclear Information System (INIS)

    Arslan, A.

    1999-01-01

    Purpose: To evaluate the consistency of fat in the high intensity signals of the normal neurohypophysis and to differentiate the high signal of posterior pituitary from that of dorsum sella. Sagittal SE T1-weighted images with frequency encoding in the horizontal direction were used in order to differentiate the high signal of posterior pituitary and dorsum sella by the vertically-oriented chemical shift artifact. Material and methods: The sellae of 46 normal volunteers were imaged with a commercially available fat suppression technique and SE sequences with frequency encoding in vertical (25 cases) and horizontal (21 cases) axes. Results: The high signal intensity was absent in 9% of the normal volunteers with no predilection to any specific age group. None of the cases with posterior pituitary high intensity signals showed suppression of the signal with fat suppression technique. A fat suppression technique was helpful in documenting the hyperintensity in 7% of normal volunteers. Nineteen of the 21 (90%) cases with high signal intensity were detected by routine SE T1-weighted images, whereas 18 of the 19 (95%) cases were detected by imaging with frequency encoding in the horizontal direction. Conclusion: The high signal does not indicate the presence of fat. Fat suppression technique and a horizontal direction of frequency encoding help in differentiating the high signal of the neurohypophysis from that of dorsum sella. (orig.)

  11. A Simple Semaphore Signaling Technique for Ultra-High Frequency Spacecraft Communications

    Science.gov (United States)

    Butman, S.; Satorius, E.; Illott, P.

    2005-11-01

    For planetary lander missions such as the upcoming Phoenix mission to Mars, the most challenging phase of the spacecraft-to-ground communications is during the critical phase termed entry, descent, and landing (EDL). At 8.4 GHz (X-band), the signals received by the largest Deep Space Network (DSN) antennas can be too weak for even 1 bit per second (bps) and therefore not able to communicate critical information to Earth. Fortunately, the lander's ultra-high frequency (UHF) link to an orbiting relay can meet the EDL requirements, but the data rate needs to be low enough to fit the capability of the UHF link during some or all of EDL. On Phoenix, the minimum data rate of the as-built UHF radio is 8 kbps and requires a signal level at the Odyssey orbiter of at least minus 120 dBm. For lower signaling levels, the effective data rate needs to be reduced, but without incurring the cost of rebuilding and requalifying the equipment. To address this scenario, a simple form of frequency-shift keying (FSK) has been devised by appropriately programming the data stream that is input to the UHF transceiver. This article describes this technique and provides performance estimates. Laboratory testing reveals that input signal levels at minus 140 dBm and lower can routinely be demodulated with the proposed signaling scheme, thereby providing a 20-dB and greater margin over the 8-kbps threshold.

  12. Frequency-domain method for separating signal and noise

    Institute of Scientific and Technical Information of China (English)

    王正明; 段晓君

    2000-01-01

    A new method for separation of signal and noise (SSN) is put forward. Frequency is redefined according to the features of signal and its derivative in the sampling time interval, thus double orthogonal basis (DOB) is constructed so that a signal can be precisely signified with a linear combination of low-frequency DOB. Under joint consideration in time domain (TD) and frequency domain (FD), a method on SSN with high accuracy is derived and a matched algorithm is designed and analyzed. This method is applicable to SSN in multiple frequency bands, and convenient in applying signal characteristics in TD and FD synthetically with higher accuracy.

  13. A broadband frequency-tunable dynamic absorber for the vibration control of structures

    International Nuclear Information System (INIS)

    Komatsuzaki, T; Inoue, T; Terashima, O

    2016-01-01

    A passive-type dynamic vibration absorber (DVA) is basically a mass-spring system that suppresses the vibration of a structure at a particular frequency. Since the natural frequency of the DVA is usually tuned to a frequency of particular excitation, the DVA is especially effective when the excitation frequency is close to the natural frequency of the structure. Fixing the physical properties of the DVA limits the application to a narrowband, harmonically excited vibration problem. A frequency-tunable DVA that can modulate its stiffness provides adaptability to the vibration control device against non-stationary disturbances. In this paper, we suggest a broadband frequency-tunable DVA whose natural frequency can be extended by 300% to the nominal value using the magnetorheological elastomers (MREs). The frequency adjustability of the proposed absorber is first shown. The real-time vibration control performance of the frequency-tunable absorber for an acoustically excited plate having multiple resonant peaks is then evaluated. Investigations show that the vibration of the structure can be effectively reduced with an improved performance by the DVA in comparison to the conventional passive- type absorber. (paper)

  14. Spatial and object-based attention modulates broadband high-frequency responses across the human visual cortical hierarchy.

    Science.gov (United States)

    Davidesco, Ido; Harel, Michal; Ramot, Michal; Kramer, Uri; Kipervasser, Svetlana; Andelman, Fani; Neufeld, Miri Y; Goelman, Gadi; Fried, Itzhak; Malach, Rafael

    2013-01-16

    One of the puzzling aspects in the visual attention literature is the discrepancy between electrophysiological and fMRI findings: whereas fMRI studies reveal strong attentional modulation in the earliest visual areas, single-unit and local field potential studies yielded mixed results. In addition, it is not clear to what extent spatial attention effects extend from early to high-order visual areas. Here we addressed these issues using electrocorticography recordings in epileptic patients. The patients performed a task that allowed simultaneous manipulation of both spatial and object-based attention. They were presented with composite stimuli, consisting of a small object (face or house) superimposed on a large one, and in separate blocks, were instructed to attend one of the objects. We found a consistent increase in broadband high-frequency (30-90 Hz) power, but not in visual evoked potentials, associated with spatial attention starting with V1/V2 and continuing throughout the visual hierarchy. The magnitude of the attentional modulation was correlated with the spatial selectivity of each electrode and its distance from the occipital pole. Interestingly, the latency of the attentional modulation showed a significant decrease along the visual hierarchy. In addition, electrodes placed over high-order visual areas (e.g., fusiform gyrus) showed both effects of spatial and object-based attention. Overall, our results help to reconcile previous observations of discrepancy between fMRI and electrophysiology. They also imply that spatial attention effects can be found both in early and high-order visual cortical areas, in parallel with their stimulus tuning properties.

  15. Detection of Fatigue Damage by Using High Frequency Nonlinear Laser Ultrasonic Signals

    International Nuclear Information System (INIS)

    Park, Seung Kyu; Park, Nak Kyu; Baik, Sung Hoon; Cheong, Yong Moo; Cha, Byung Heon

    2012-01-01

    The detection of fatigue damage for the components of a nuclear power plant is one of key techniques to prevent a catastrophic accident and the subsequent severe losses. Specifically, it is preferred to detect at an early stage of the fatigue damage. If the fatigue damage that is in danger of growing into a fracture is accurately detected, an appropriate treatment could be carried out to improve the condition. Although most engineers and designers take precautions against fatigue, some breakdowns of nuclear power plant components still occur due to fatigue damage. It is considered that ultrasound testing technique is the most promising method to detect the fatigue damage in many nondestructive testing methods. Laser ultrasound has attracted attention as a noncontact testing technique. Especially, laser ultrasonic signal has wide band frequency spectrum which can provide more accurate information for a testing material. The conventional linear ultrasonic technique is sensitive to gross defects or opened cracks whereas it is less sensitive to evenly distributed micro-cracks or degradation. An alternative technique to overcome this limitation is nonlinear ultrasound. The principal difference between linear and nonlinear technique is that in the latter the existence and characteristics of defects are often related to an acoustic signal whose frequency differs from that of the input signal. This is related to the radiation and propagation of finite amplitude, especially high power, ultrasound and its interaction with discontinuities, such as cracks, interfaces and voids. Since material failure or degradation is usually preceded by some kind of nonlinear mechanical behavior before significant plastic deformation or material damage occurs. The presence of nonlinear terms in the wave equation causes intense acoustic waves to generate new waves at frequencies which are multiples of the initial sound wave frequency. The nonlinear effect can exert a strong effect on the

  16. Signal-Characteristic analysis with respect to backing material of PVDF-based high-frequency ultrasound for photoacoustic microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jun Su; Chang, Jin Ho [Dept. of Electronic Engineering, Sogang University, Seoul (Korea, Republic of)

    2015-04-15

    Photoacoustic microscopy is capable of providing high-resolution molecular images, and its spatial resolution is typically determined by ultrasonic transducers used to receive the photoacoustic signals. Therefore, ultrasonic transducers for photoacoustic microscopy (PAM) should have a high operating frequency, broad bandwidth, and high signal-reception efficiency. Polyvinylidene fluoride (PVDF) is a suitable material. To take full advantage of this material, the selection of the backing material is crucial, as it influences the center frequency and bandwidth of the transducer. Therefore, we experimentally determined the most suitable backing material among EPO-TEK 301, E-Solder 3022, and RTV. For this, three PVDF high-frequency single-element transducers were fabricated with each backing material. The center frequency and -6 dB bandwidth of each transducer were ascertained by a pulse-echo test. The spatial resolution of each transducer was examined using wire-target images. The experimental results indicated that EPO-TEK 301 is the most suitable backing material for a PAM transducer. This material provides the highest signal magnitude and a reasonable bandwidth because a large portion of the energy propagates toward the front medium, and the PVDF resonates in the half-wave mode.

  17. Parametric Amplification Protocol for Frequency-Modulated Magnetic Resonance Force Microscopy Signals

    Science.gov (United States)

    Harrell, Lee; Moore, Eric; Lee, Sanggap; Hickman, Steven; Marohn, John

    2011-03-01

    We present data and theoretical signal and noise calculations for a protocol using parametric amplification to evade the inherent tradeoff between signal and detector frequency noise in force-gradient magnetic resonance force microscopy signals, which are manifested as a modulated frequency shift of a high- Q microcantilever. Substrate-induced frequency noise has a 1 / f frequency dependence, while detector noise exhibits an f2 dependence on modulation frequency f . Modulation of sample spins at a frequency that minimizes these two contributions typically results in a surface frequency noise power an order of magnitude or more above the thermal limit and may prove incompatible with sample spin relaxation times as well. We show that the frequency modulated force-gradient signal can be used to excite the fundamental resonant mode of the cantilever, resulting in an audio frequency amplitude signal that is readily detected with a low-noise fiber optic interferometer. This technique allows us to modulate the force-gradient signal at a sufficiently high frequency so that substrate-induced frequency noise is evaded without subjecting the signal to the normal f2 detector noise of conventional demodulation.

  18. Underwater Acoustic Signal Processing

    National Research Council Canada - National Science Library

    Culver, Richard L; Sibul, Leon H; Bradley, David L

    2007-01-01

    .... The research is directed toward passive sonar detection and classification, continuous wave (CW) and broadband signals, shallow water operation, both platform-mounted and distributed systems, and frequencies below 1 kHz...

  19. A Design of Dual Broadband Antenna in Mobile Communication System

    Directory of Open Access Journals (Sweden)

    Jianming Zhou

    2015-01-01

    Full Text Available A design of dual broadband antenna is proposed in this paper; it consists of one low frequency unit and two high frequency units. The low frequency unit consists of a pair of printing vibrators; the high frequency unit consists of a pair of printing oscillators, which is bent at its end, and high frequency unit and low frequency unit are set on the same dielectric substrate. Through adding a parasitic unit on antenna, it can enhance frequency bandwidth without affecting the bandwidth. In the high frequency unit, it adopts gap-coupled microstrip line feeding method in order to get enough bandwidth. Through the test of dual broadband antenna, it can be found that, in the low frequency part, the antenna covers 20% bandwidth of the total bandwidth, and it covers the frequency from 800 MHz to 980 MHz. In the high frequency, the antenna covers 60% of total bandwidth and its frequency is from 1540 MHz to 2860 MHz, so the designed antenna can satisfy the frequency requirements of 2G/3G/LTE (4G communication system.

  20. A portable, differential amplifier for recording high frequency EEG signals and evoked potentials

    International Nuclear Information System (INIS)

    Donos, Cristian; Giurgiu, Liviu; Popescu, Aurel; Mocanu, Marian

    2010-01-01

    In a clinical context, EEG refers to recording the brain's spontaneous electric activity, using small electrodes placed on the scalp. The signals collected are electric 'potentials' measured between two electrodes. Usually, for a healthy adult, these signals have small voltage (10 μV to 100 μV) and frequencies in the 0-40 Hz range. In the scientific literature, there are mentioned EEG signals and evoked potentials that have higher frequencies (up to 600 Hz) and amplitudes lower than 500 ηV. For this reason, building an amplifier capable of recording EEG signals in the ηV range and with frequencies up to couple of kHz is necessary to continue research beyond 600 Hz. We designed a very low noise amplifier that is able to measure/record EEG signals in the ηV range over a very large frequency bandwidth (0.09 Hz -385 kHz).(Author)

  1. Broadband demonstrations of true-time delay using linear sideband chirped programming and optical coherent transients

    International Nuclear Information System (INIS)

    Reibel, R.R.; Barber, Z.W.; Fischer, J.A.; Tian, M.; Babbitt, W.R.

    2004-01-01

    Linear sideband chirped (LSC) programming is introduced as a means of configuring spatial-spectral holographic gratings for optical coherent transient processors. Similar to linear frequency chirped programming, LSC programming allows the use of broadband integrated electro-optic phase modulators to produce chirps instead of using elaborate broadband chirped lasers. This approach has several advantages including the ability to use a stabilized laser for the optical carrier as well as stable, reproducible chirped optical signals when the modulator is driven digitally. Using LSC programming, we experimentally demonstrate broadband true-time delay as a proof of principle for the optical control of phased array radars. Here both cw phase modulated and binary phase shift keyed probe signals are true-time delayed with bandwidths of 1 GHz and delay resolutions better than 60 ps

  2. Broadband and High power Reactive Jamming Resilient Wireless Communication

    Science.gov (United States)

    2017-10-21

    Broadband and High -power Reactive Jamming Resilient Wireless Communication The views, opinions and/or findings contained in this report are those of... available in extremely hostile environments, where FHSS and DSSS are completely defeated by a broadband and high -power reactive jammer. b. Wireless...SECURITY CLASSIFICATION OF: 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13. SUPPLEMENTARY NOTES 12. DISTRIBUTION AVAILIBILITY STATEMENT 6. AUTHORS

  3. Synthesis of High-Frequency Ground Motion Using Information Extracted from Low-Frequency Ground Motion

    Science.gov (United States)

    Iwaki, A.; Fujiwara, H.

    2012-12-01

    Broadband ground motion computations of scenario earthquakes are often based on hybrid methods that are the combinations of deterministic approach in lower frequency band and stochastic approach in higher frequency band. Typical computation methods for low-frequency and high-frequency (LF and HF, respectively) ground motions are the numerical simulations, such as finite-difference and finite-element methods based on three-dimensional velocity structure model, and the stochastic Green's function method, respectively. In such hybrid methods, LF and HF wave fields are generated through two different methods that are completely independent of each other, and are combined at the matching frequency. However, LF and HF wave fields are essentially not independent as long as they are from the same event. In this study, we focus on the relation among acceleration envelopes at different frequency bands, and attempt to synthesize HF ground motion using the information extracted from LF ground motion, aiming to propose a new method for broad-band strong motion prediction. Our study area is Kanto area, Japan. We use the K-NET and KiK-net surface acceleration data and compute RMS envelope at four frequency bands: 0.5-1.0 Hz, 1.0-2.0 Hz, 2.0-4.0 Hz, .0-8.0 Hz, and 8.0-16.0 Hz. Taking the ratio of the envelopes of adjacent bands, we find that the envelope ratios have stable shapes at each site. The empirical envelope-ratio characteristics are combined with low-frequency envelope of the target earthquake to synthesize HF ground motion. We have applied the method to M5-class earthquakes and a M7 target earthquake that occurred in the vicinity of Kanto area, and successfully reproduced the observed HF ground motion of the target earthquake. The method can be applied to a broad band ground motion simulation for a scenario earthquake by combining numerically-computed low-frequency (~1 Hz) ground motion with the empirical envelope ratio characteristics to generate broadband ground motion

  4. Laser generated ultrasound sources using polymer nanocomposites for high frequency metrology

    KAUST Repository

    Rajagopal, Srinath

    2017-11-22

    Accurate characterization of ultrasound fields generated by diagnostic and therapeutic transducers is critical for patient safety. This requires hydrophones calibrated to a traceable standard and currently the upper calibration frequency range available to the user community is limited to a frequency of 40 MHz. However, the increasing use of high frequencies for both imaging and therapy necessitates calibrations to frequencies well beyond this range. For this to be possible, a source of high amplitude, broadband, quasi-planar and stable ultrasound fields is required. This is difficult to achieve using conventional piezoelectric sources, but laser generated ultrasound is a promising technique in this regard. In this study, various polymer-carbon nanotube nanocomposites (PNC) were fabricated and tested for their suitability for such an application by varying the polymer type, carbon nanotubes weight content in the polymer, and PNC thickness. A broadband hydrophone was used to measure the peak pressure and bandwidth of the laser generated ultrasound pulse. Peak-positive pressures of up to 8 MPa and −6dB bandwidths of up to 40 MHz were recorded. There is a nonlinear dependence of the peak pressure on the laser fluence and the bandwidth scales inversely proportionally to the peak pressure. The high-pressure plane waves generated from this preliminary investigation has demonstrated that laser generated ultrasound sources are a promising technique for high frequency calibration of hydrophones.

  5. Broadband set-top box using MAP-CA processor

    Science.gov (United States)

    Bush, John E.; Lee, Woobin; Basoglu, Chris

    2001-12-01

    Advances in broadband access are expected to exert a profound impact in our everyday life. It will be the key to the digital convergence of communication, computer and consumer equipment. A common thread that facilitates this convergence comprises digital media and Internet. To address this market, Equator Technologies, Inc., is developing the Dolphin broadband set-top box reference platform using its MAP-CA Broadband Signal ProcessorT chip. The Dolphin reference platform is a universal media platform for display and presentation of digital contents on end-user entertainment systems. The objective of the Dolphin reference platform is to provide a complete set-top box system based on the MAP-CA processor. It includes all the necessary hardware and software components for the emerging broadcast and the broadband digital media market based on IP protocols. Such reference design requires a broadband Internet access and high-performance digital signal processing. By using the MAP-CA processor, the Dolphin reference platform is completely programmable, allowing various codecs to be implemented in software, such as MPEG-2, MPEG-4, H.263 and proprietary codecs. The software implementation also enables field upgrades to keep pace with evolving technology and industry demands.

  6. An ultra-efficient nonlinear planar integrated platform for optical signal processing and generation

    DEFF Research Database (Denmark)

    Pu, Minhao; Ottaviano, Luisa; Semenova, Elizaveta

    2017-01-01

    This paper will discuss the recently developed integrated platform: AlGaAs-oninsulator and its broad range of nonlinear applications. Recent demonstrations of broadband optical signal processing and efficient frequency comb generations in this platform will be reviewed.......This paper will discuss the recently developed integrated platform: AlGaAs-oninsulator and its broad range of nonlinear applications. Recent demonstrations of broadband optical signal processing and efficient frequency comb generations in this platform will be reviewed....

  7. Calibration of semi-stochastic procedure for simulating high-frequency ground motions

    Science.gov (United States)

    Seyhan, Emel; Stewart, Jonathan P.; Graves, Robert

    2013-01-01

    Broadband ground motion simulation procedures typically utilize physics-based modeling at low frequencies, coupled with semi-stochastic procedures at high frequencies. The high-frequency procedure considered here combines deterministic Fourier amplitude spectra (dependent on source, path, and site models) with random phase. Previous work showed that high-frequency intensity measures from this simulation methodology attenuate faster with distance and have lower intra-event dispersion than in empirical equations. We address these issues by increasing crustal damping (Q) to reduce distance attenuation bias and by introducing random site-to-site variations to Fourier amplitudes using a lognormal standard deviation ranging from 0.45 for Mw  100 km).

  8. High accuracy microwave frequency measurement based on single-drive dual-parallel Mach-Zehnder modulator

    DEFF Research Database (Denmark)

    Zhao, Ying; Pang, Xiaodan; Deng, Lei

    2011-01-01

    A novel approach for broadband microwave frequency measurement by employing a single-drive dual-parallel Mach-Zehnder modulator is proposed and experimentally demonstrated. Based on bias manipulations of the modulator, conventional frequency-to-power mapping technique is developed by performing a...... 10−3 relative error. This high accuracy frequency measurement technique is a promising candidate for high-speed electronic warfare and defense applications....

  9. Comparative study of broadband electrodynamic properties of single-crystal and thin-film strontium titanate

    International Nuclear Information System (INIS)

    Findikoglu, A. T.; Jia, Q. X.; Kwon, C.; Reagor, D. W.; Kaduchak, G.; Rasmussen, K. Oe.; Bishop, A. R.

    1999-01-01

    We have used a coplanar waveguide structure to study broadband electrodynamic properties of single-crystal and thin-film strontium titanate. We have incorporated both time- and frequency-domain measurements to determine small-signal effective refractive index and loss tangent as functions of frequency (up to 4 GHz), dc bias (up to 10 6 V/m), and cryogenic temperature (17 and 60 K). The large-signal impulse response of the devices and the associated phenomenological nonlinear wave equation illustrate how dissipation and nonlinearity combine to produce the overall response in the large-signal regime. (c) 1999 American Institute of Physics

  10. Observations involving broadband impedance modelling

    Energy Technology Data Exchange (ETDEWEB)

    Berg, J S [Stanford Linear Accelerator Center, Menlo Park, CA (United States)

    1996-08-01

    Results for single- and multi-bunch instabilities can be significantly affected by the precise model that is used for the broadband impedance. This paper discusses three aspects of broadband impedance modelling. The first is an observation of the effect that a seemingly minor change in an impedance model has on the single-bunch mode coupling threshold. The second is a successful attempt to construct a model for the high-frequency tails of an r.f. cavity. The last is a discussion of requirements for the mathematical form of an impedance which follow from the general properties of impedances. (author)

  11. Observations involving broadband impedance modelling

    International Nuclear Information System (INIS)

    Berg, J.S.

    1995-08-01

    Results for single- and multi-bunch instabilities can be significantly affected by the precise model that is used for the broadband impendance. This paper discusses three aspects of broadband impendance modeling. The first is an observation of the effect that a seemingly minor change in an impedance model has on the single-bunch mode coupling threshold. The second is a successful attempt to construct a model for the high-frequency tails of an r.f cavity. The last is a discussion of requirements for the mathematical form of an impendance which follow from the general properties of impendances

  12. Numerical simulation of ultrasound-thermotherapy combining nonlinear wave propagation with broadband soft-tissue absorption.

    Science.gov (United States)

    Ginter, S

    2000-07-01

    Ultrasound (US) thermotherapy is used to treat tumours, located deep in human tissue, by heat. It features by the application of high intensity focused ultrasound (HIFU), high local temperatures of about 90 degrees C and short treating time of a few seconds. Dosage of the therapy remains a problem. To get it under control, one has to know the heat source, i.e. the amount of absorbed US power, which shows nonlinear influences. Therefore, accurate simulations are essential. In this paper, an improved simulation model is introduced which enables accurate investigations of US thermotherapy. It combines nonlinear US propagation effects, which lead to generation of higher harmonics, with a broadband frequency-power law absorption typical for soft tissue. Only the combination of both provides a reliable calculation of the generated heat. Simulations show the influence of nonlinearities and broadband damping for different source signals on the absorbed US power density distribution.

  13. Broadband direct RF digitization receivers

    CERN Document Server

    Jamin, Olivier

    2014-01-01

    This book discusses the trade-offs involved in designing direct RF digitization receivers for the radio frequency and digital signal processing domains.  A system-level framework is developed, quantifying the relevant impairments of the signal processing chain, through a comprehensive system-level analysis.  Special focus is given to noise analysis (thermal noise, quantization noise, saturation noise, signal-dependent noise), broadband non-linear distortion analysis, including the impact of the sampling strategy (low-pass, band-pass), analysis of time-interleaved ADC channel mismatches, sampling clock purity and digital channel selection. The system-level framework described is applied to the design of a cable multi-channel RF direct digitization receiver. An optimum RF signal conditioning, and some algorithms (automatic gain control loop, RF front-end amplitude equalization control loop) are used to relax the requirements of a 2.7GHz 11-bit ADC. A two-chip implementation is presented, using BiCMOS and 65nm...

  14. Broadband quantitative NQR for authentication of vitamins and dietary supplements

    Science.gov (United States)

    Chen, Cheng; Zhang, Fengchao; Bhunia, Swarup; Mandal, Soumyajit

    2017-05-01

    We describe hardware, pulse sequences, and algorithms for nuclear quadrupole resonance (NQR) spectroscopy of medicines and dietary supplements. Medicine and food safety is a pressing problem that has drawn more and more attention. NQR is an ideal technique for authenticating these substances because it is a non-invasive method for chemical identification. We have recently developed a broadband NQR front-end that can excite and detect 14N NQR signals over a wide frequency range; its operating frequency can be rapidly set by software, while sensitivity is comparable to conventional narrowband front-ends over the entire range. This front-end improves the accuracy of authentication by enabling multiple-frequency experiments. We have also developed calibration and signal processing techniques to convert measured NQR signal amplitudes into nuclear spin densities, thus enabling its use as a quantitative technique. Experimental results from several samples are used to illustrate the proposed methods.

  15. Application of multiple signal classification algorithm to frequency estimation in coherent dual-frequency lidar

    Science.gov (United States)

    Li, Ruixiao; Li, Kun; Zhao, Changming

    2018-01-01

    Coherent dual-frequency Lidar (CDFL) is a new development of Lidar which dramatically enhances the ability to decrease the influence of atmospheric interference by using dual-frequency laser to measure the range and velocity with high precision. Based on the nature of CDFL signals, we propose to apply the multiple signal classification (MUSIC) algorithm in place of the fast Fourier transform (FFT) to estimate the phase differences in dual-frequency Lidar. In the presence of Gaussian white noise, the simulation results show that the signal peaks are more evident when using MUSIC algorithm instead of FFT in condition of low signal-noise-ratio (SNR), which helps to improve the precision of detection on range and velocity, especially for the long distance measurement systems.

  16. Printed silver nanowire antennas with low signal loss at high-frequency radio

    Science.gov (United States)

    Komoda, Natsuki; Nogi, Masaya; Suganuma, Katsuaki; Kohno, Kazuo; Akiyama, Yutaka; Otsuka, Kanji

    2012-05-01

    Silver nanowires are printable and conductive, and are believed to be promising materials in the field of printed electronics. However, the resistivity of silver nanowire printed lines is higher than that of metallic particles or flakes even when sintered at high temperatures of 100-400 °C. Therefore, their applications have been limited to the replacement of transparent electrodes made from high-resistivity materials, such as doped metallic oxides, conductive polymers, carbon nanotubes, or graphenes. Here we report that using printed silver nanowire lines, signal losses obtained in the high-frequency radio were lower than those obtained using etched copper foil antennas, because their surfaces were much smoother than those of etched copper foil antennas. This was the case even though the resistivity of silver nanowire lines was 43-71 μΩ cm, which is much higher than that of etched copper foil (2 μΩ cm). When printed silver nanowire antennas were heated at 100 °C, they achieved signal losses that were much lower than those of silver paste antennas comprising microparticles, nanoparticles, and flakes. Furthermore, using a low temperature process, we succeeded in remotely controlling a commercialized radio-controlled car by transmitting a 2.45 GHz signal via a silver nanowire antenna printed on a polyethylene terephthalate film.Silver nanowires are printable and conductive, and are believed to be promising materials in the field of printed electronics. However, the resistivity of silver nanowire printed lines is higher than that of metallic particles or flakes even when sintered at high temperatures of 100-400 °C. Therefore, their applications have been limited to the replacement of transparent electrodes made from high-resistivity materials, such as doped metallic oxides, conductive polymers, carbon nanotubes, or graphenes. Here we report that using printed silver nanowire lines, signal losses obtained in the high-frequency radio were lower than those

  17. Broadband Reflectionless Metasheets: Frequency-Selective Transmission and Perfect Absorption

    Directory of Open Access Journals (Sweden)

    V. S. Asadchy

    2015-07-01

    Full Text Available Energy of propagating electromagnetic waves can be fully absorbed in a thin lossy layer, but only in a narrow frequency band, as follows from the causality principle. On the other hand, it appears that there are no fundamental limitations on broadband matching of thin resonant absorbing layers. However, known thin absorbers produce significant reflections outside of the resonant absorption band. In this paper, we explore possibilities to realize a thin absorbing layer that produces no reflected waves in a very wide frequency range, while the transmission coefficient has a narrow peak of full absorption. Here we show, both theoretically and experimentally, that a thin resonant absorber, invisible in reflection in a very wide frequency range, can be realized if one and the same resonant mode of the absorbing array unit cells is utilized to create both electric and magnetic responses. We test this concept using chiral particles in each unit cell, arranged in a periodic planar racemic array, utilizing chirality coupling in each unit cell but compensating the field coupling at the macroscopic level. We prove that the concept and the proposed realization approach also can be used to create nonreflecting layers for full control of transmitted fields. Our results can have a broad range of potential applications over the entire electromagnetic spectrum including, for example, perfect ultracompact wave filters and selective multifrequency sensors.

  18. High-frequency signal paths in the TMR-86.1 experimental tomography apparatus

    International Nuclear Information System (INIS)

    Obrcian, J.; Jellus, V.; Weis, J.; Frollo, I.

    1990-01-01

    The NMR-based TMR-86.1 tomography apparatus, developed at the Institute of Measurement and Measuring Instrumentation, Slovak Academy of Sciences in Bratislava, Czechoslovakia, enables imaging of the inner structure of biological samples and human limbs no more than 110 mm in diameter, using a measuring matrix containing at most 128x128 elements. The imaged matrix can possess a maximum of 256x256 image elements with 256 brightness steps. The signal paths of the high-frequency excitation-imaging complex of the apparatus are described. Some functional blocks of the apparatus can be used without substantial modifications for the imaging of larger objects such as the human body. From the point of view of the high-frequency pulses for nonselective excitation (so-called 180deg-pulses), the excitation pulse power will have to be increased to at least 1 kW. (author). 5 figs, 7 refs

  19. Broadband seismic : case study modeling and data processing

    Science.gov (United States)

    Cahyaningtyas, M. B.; Bahar, A.

    2018-03-01

    Seismic data with wide range of frequency is needed due to its close relation to resolution and the depth of the target. Low frequency provides deeper penetration for the imaging of deep target. In addition, the wider the frequency bandwidth, the sharper the wavelet. Sharp wavelet is responsible for high-resolution imaging and is very helpful to resolve thin bed. As a result, the demand for broadband seismic data is rising and it spurs the technology development of broadband seismic in oil and gas industry. An obstacle that is frequently found on marine seismic data is the existence of ghost that affects the frequency bandwidth contained on the seismic data. Ghost alters bandwidth to bandlimited. To reduce ghost effect and to acquire broadband seismic data, lots of attempts are used, both on the acquisition and on the processing of seismic data. One of the acquisition technique applied is the multi-level streamer, where some streamers are towed on some levels of depth. Multi-level streamer will yield data with varied ghost notch shown on frequency domain. If the ghost notches are not overlapping, the summation of multi-level streamer data will reduce the ghost effect. The result of the multi-level streamer data processing shows that reduction of ghost notch on frequency domain indeed takes place.

  20. Low Computational Signal Acquisition for GNSS Receivers Using a Resampling Strategy and Variable Circular Correlation Time

    Directory of Open Access Journals (Sweden)

    Yeqing Zhang

    2018-02-01

    Full Text Available For the objective of essentially decreasing computational complexity and time consumption of signal acquisition, this paper explores a resampling strategy and variable circular correlation time strategy specific to broadband multi-frequency GNSS receivers. In broadband GNSS receivers, the resampling strategy is established to work on conventional acquisition algorithms by resampling the main lobe of received broadband signals with a much lower frequency. Variable circular correlation time is designed to adapt to different signal strength conditions and thereby increase the operation flexibility of GNSS signal acquisition. The acquisition threshold is defined as the ratio of the highest and second highest correlation results in the search space of carrier frequency and code phase. Moreover, computational complexity of signal acquisition is formulated by amounts of multiplication and summation operations in the acquisition process. Comparative experiments and performance analysis are conducted on four sets of real GPS L2C signals with different sampling frequencies. The results indicate that the resampling strategy can effectively decrease computation and time cost by nearly 90–94% with just slight loss of acquisition sensitivity. With circular correlation time varying from 10 ms to 20 ms, the time cost of signal acquisition has increased by about 2.7–5.6% per millisecond, with most satellites acquired successfully.

  1. Low Computational Signal Acquisition for GNSS Receivers Using a Resampling Strategy and Variable Circular Correlation Time

    Science.gov (United States)

    Zhang, Yeqing; Wang, Meiling; Li, Yafeng

    2018-01-01

    For the objective of essentially decreasing computational complexity and time consumption of signal acquisition, this paper explores a resampling strategy and variable circular correlation time strategy specific to broadband multi-frequency GNSS receivers. In broadband GNSS receivers, the resampling strategy is established to work on conventional acquisition algorithms by resampling the main lobe of received broadband signals with a much lower frequency. Variable circular correlation time is designed to adapt to different signal strength conditions and thereby increase the operation flexibility of GNSS signal acquisition. The acquisition threshold is defined as the ratio of the highest and second highest correlation results in the search space of carrier frequency and code phase. Moreover, computational complexity of signal acquisition is formulated by amounts of multiplication and summation operations in the acquisition process. Comparative experiments and performance analysis are conducted on four sets of real GPS L2C signals with different sampling frequencies. The results indicate that the resampling strategy can effectively decrease computation and time cost by nearly 90–94% with just slight loss of acquisition sensitivity. With circular correlation time varying from 10 ms to 20 ms, the time cost of signal acquisition has increased by about 2.7–5.6% per millisecond, with most satellites acquired successfully. PMID:29495301

  2. Broadband Terahertz Refraction Index Dispersion and Loss of Polymeric Dielectric Substrate and Packaging Materials

    Science.gov (United States)

    Motaharifar, E.; Pierce, R. G.; Islam, R.; Henderson, R.; Hsu, J. W. P.; Lee, Mark

    2018-01-01

    In the effort to push the high-frequency performance of electronic circuits and signal interconnects from millimeter waves to beyond 1 THz, a quantitative knowledge of complex refraction index values and dispersion in potential dielectric substrate, encapsulation, waveguide, and packaging materials becomes critical. Here we present very broadband measurements of the real and imaginary index spectra of four polymeric dielectric materials considered for use in high-frequency electronics: benzocyclobutene (BCB), polyethylene naphthalate (PEN), the photoresist SU-8, and polydimethylsiloxane (PDMS). Reflectance and transmittance spectra from 3 to 75 THz were made using a Fourier transform spectrometer on freestanding material samples. These data were quantitatively analyzed, taking into account multiple partial reflections from front and back surfaces and molecular bond resonances, where applicable, to generate real and imaginary parts of the refraction index as a function of frequency. All materials showed signatures of infrared active organic molecular bond resonances between 10 and 50 THz. Low-loss transmission windows as well as anti-window bands of high dispersion and loss can be readily identified and incorporated into high-frequency design models.

  3. Estimation of red-light running frequency using high-resolution traffic and signal data.

    Science.gov (United States)

    Chen, Peng; Yu, Guizhen; Wu, Xinkai; Ren, Yilong; Li, Yueguang

    2017-05-01

    Red-light-running (RLR) emerges as a major cause that may lead to intersection-related crashes and endanger intersection safety. To reduce RLR violations, it's critical to identify the influential factors associated with RLR and estimate RLR frequency. Without resorting to video camera recordings, this study investigates this important issue by utilizing high-resolution traffic and signal event data collected from loop detectors at five intersections on Trunk Highway 55, Minneapolis, MN. First, a simple method is proposed to identify RLR by fully utilizing the information obtained from stop bar detectors, downstream entrance detectors and advance detectors. Using 12 months of event data, a total of 6550 RLR cases were identified. According to a definition of RLR frequency as the conditional probability of RLR on a certain traffic or signal condition (veh/1000veh), the relationships between RLR frequency and some influential factors including arriving time at advance detector, approaching speed, headway, gap to the preceding vehicle on adjacent lane, cycle length, geometric characteristics and even snowing weather were empirically investigated. Statistical analysis shows good agreement with the traffic engineering practice, e.g., RLR is most likely to occur on weekdays during peak periods under large traffic demands and longer signal cycles, and a total of 95.24% RLR events occurred within the first 1.5s after the onset of red phase. The findings confirmed that vehicles tend to run the red light when they are close to intersection during phase transition, and the vehicles following the leading vehicle with short headways also likely run the red light. Last, a simplified nonlinear regression model is proposed to estimate RLR frequency based on the data from advance detector. The study is expected to helpbetter understand RLR occurrence and further contribute to the future improvement of intersection safety. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. A dual resonant rectilinear-to-rotary oscillation converter for low frequency broadband electromagnetic energy harvesting

    Science.gov (United States)

    Deng, Wei; Wang, Ya

    2017-09-01

    This paper reports a dual resonant rectilinear-to-rotary oscillation converter (RROC) for low frequency broadband electromagnetic energy harvesting from ambient vibrations. An approximate theoretical model has been established to integrate the electromechanical coupling into a comprehensive electromagnetic-dynamic model of the dual resonant RROC. Numerical simulation has proved the nature of dual resonances by revealing that both the rectilinear resonance and the rotary resonance could be achieved when the stand-alone rectilinear oscillator (RLO) and the stand-alone rotary oscillator (RTO) were excited independently. Simulation on the magnetically coupled RROC has also shown that the rectilinear resonance and the rotary resonance could be obtained simultaneously in the low-frequency region (2-14 Hz) with well-defined restoring torque (M r ) and the initial rotation angle of the RLO (ψ). The magnetic interaction patterns between the rectilinear and the RTOs have been categorized based on aforementioned simulation results. Both simulation and experimental results have demonstrated broadband output attributing from the dual resonances. Experimental results have also indicated that the RROC could have wide bandwidth in a much lower frequency region (2-8 Hz) even without the rotary resonance as long as the system parameters are carefully tuned. Parameter analysis on different values of M r and ψ are experimentally carried out to provide a quantitative guidance of designing the RROC to achieve an optimal power density.

  5. Fully phase-encoded MRI near metallic implants using ultrashort echo times and broadband excitation.

    Science.gov (United States)

    Wiens, Curtis N; Artz, Nathan S; Jang, Hyungseok; McMillan, Alan B; Koch, Kevin M; Reeder, Scott B

    2018-04-01

    To develop a fully phase-encoded MRI method for distortion-free imaging near metallic implants, in clinically feasible acquisition times. An accelerated 3D fully phase-encoded acquisition with broadband excitation and ultrashort echo times is presented, which uses a broadband radiofrequency pulse to excite the entire off-resonance induced by the metallic implant. Furthermore, fully phase-encoded imaging is used to prevent distortions caused by frequency encoding, and to obtain ultrashort echo times for rapidly decaying signal. Phantom and in vivo acquisitions were used to describe the relationship among excitation bandwidth, signal loss near metallic implants, and T 1 weighting. Shorter radiofrequency pulses captured signal closer to the implant by improving spectral coverage and allowing shorter echo times, whereas longer pulses improved T 1 weighting through larger maximum attainable flip angles. Comparisons of fully phase-encoded acquisition with broadband excitation and ultrashort echo times to T 1 -weighted multi-acquisition with variable resonance image combination selective were performed in phantoms and subjects with metallic knee and hip prostheses. These acquisitions had similar contrast and acquisition efficiency. Accelerated fully phase-encoded acquisitions with ultrashort echo times and broadband excitation can generate distortion free images near metallic implants in clinically feasible acquisition times. Magn Reson Med 79:2156-2163, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  6. Josephson admittance spectroscopy application for frequency analysis of broadband THz antennas

    International Nuclear Information System (INIS)

    Volkov, O Yu; Divin, Yu Yu; Gubankov, V N; Gundareva, I I; Pavlovskiy, V V

    2010-01-01

    Application of Josephson admittance spectroscopy for the spectral analysis of a broad-band log-periodic superconducting antenna was demonstrated at the frequency range from 50 to 700 GHz. The [001]-tilt YBa 2 Cu 3 O 7-x bicrystal Josephson junctions, integrated with sinuous log-periodic YBa 2 Cu 3 O 7-x antennas, were fabricated on NdGaO 3 bicrystal substrates. A real part of the antenna admittance ReY(f) as a function of the frequency f was reconstructed from the modification of the dc current-voltage characteristic of the junction, induced by the antenna. Resonance features were observed in the recovered ReY(f)-spectra with a periodicity in the logarithmic frequency scale, corresponding to log-periodic geometry of the antenna. The ReY(f)-spectra, recovered by Josephson spectroscopy, were compared with the ReY(f)-spectra, obtained by CAD simulation, and both spectra were shown to be similar in their main features. A value of 23 was obtained for an effective permittivity of the NdGaO3 bicrystal substrates by fitting simulated data to those obtained from Josephson spectroscopy.

  7. Broadband Ionospheric Scintillation Measurements from Space

    Science.gov (United States)

    Suszcynsky, D. M.; Light, M. E.; Pigue, M. J.

    2014-12-01

    The U.S. Department of Energy's Radio Frequency Propagation (RFProp) experiment consists of a satellite-based radio receiver suite to study various aspects of trans-ionospheric signal propagation and detection in four frequency bands, 2 - 55 MHz, 125 - 175 MHz, 365 - 415 MHz and 825 - 1100 MHz. In this paper, we present an overview of the RFProp on-orbit research and analysis effort with particular focus on an equatorial scintillation experiment called ESCINT. The 3-year ESCINT project is designed to characterize equatorial ionospheric scintillation in the upper HF and lower VHF portions of the radio spectrum (20 - 150 MHz). Both a 40 MHz continuous wave (CW) signal and 30 - 42 MHz swept frequency signal are transmitted to the satellite receiver suite from the Reagan Test Site at Kwajalein Atoll in the Marshall Islands (8.7° N, 167.7° E) in four separate campaigns centered on the 2014 and 2015 equinoxes. Results from the first campaign conducted from April 22 - May 15, 2014 will be presented including (a) coherence bandwidth measurements over a full range of transmission frequencies and scintillation activity levels, (b) spread-Doppler clutter effects arising from preferential ray paths to the satellite due to refraction off of isolated density irregularities, and (c) supporting ray-trace simulations. The broadband nature of the measurements is found to offer unique insight into both the structure of ionospheric irregularities and their impact on HF/VHF trans-ionospheric radio wave propagation.

  8. 47 CFR 90.219 - Use of signal boosters.

    Science.gov (United States)

    2010-10-01

    ... to operate radio systems in the frequency bands above 150 MHz may employ signal boosters at fixed... fill in only weak signal areas and cannot extend the system's normal signal coverage area. (b) Class A... effective radiated power (ERP) of the unit to a maximum of 5 watts under all conditions. Class B broadband...

  9. Variable reflectivity signal mirrors and signal response measurements

    International Nuclear Information System (INIS)

    Vine, Glenn de; Shaddock, Daniel A; McClelland, David E

    2002-01-01

    Future gravitational wave detectors will include some form of signal mirror in order to alter the signal response of the device. We introduce interferometer configurations which utilize a variable reflectivity signal mirror allowing a tunable peak frequency and variable signal bandwidth. A detector configured with a Fabry-Perot cavity as the signal mirror is compared theoretically with one using a Michelson interferometer for a signal mirror. A system for the measurement of the interferometer signal responses is introduced. This technique is applied to a power-recycled Michelson interferometer with resonant sideband extraction. We present broadband measurements of the benchtop prototype's signal response for a range of signal cavity detunings. This technique is also applicable to most other gravitational wave detector configurations

  10. Variable reflectivity signal mirrors and signal response measurements

    CERN Document Server

    Vine, G D; McClelland, D E

    2002-01-01

    Future gravitational wave detectors will include some form of signal mirror in order to alter the signal response of the device. We introduce interferometer configurations which utilize a variable reflectivity signal mirror allowing a tunable peak frequency and variable signal bandwidth. A detector configured with a Fabry-Perot cavity as the signal mirror is compared theoretically with one using a Michelson interferometer for a signal mirror. A system for the measurement of the interferometer signal responses is introduced. This technique is applied to a power-recycled Michelson interferometer with resonant sideband extraction. We present broadband measurements of the benchtop prototype's signal response for a range of signal cavity detunings. This technique is also applicable to most other gravitational wave detector configurations.

  11. Broadband analysis of landslides seismic signal : example of the Oso-Steelhead landslide and other recent events

    Science.gov (United States)

    Hibert, C.; Stark, C. P.; Ekstrom, G.

    2014-12-01

    Landslide failures on the scale of mountains are spectacular, dangerous, and spontaneous, making direct observations hard to obtain. Measurement of their dynamic properties during runout is a high research priority, but a logistical and technical challenge. Seismology has begun to help in several important ways. Taking advantage of broadband seismic stations, recent advances now allow: (i) the seismic detection and location of large landslides in near-real-time, even for events in very remote areas that may have remain undetected, such as the 2014 Mt La Perouse supraglacial failure in Alaska; (ii) inversion of long-period waves generated by large landslides to yield an estimate of the forces imparted by the bulk accelerating mass; (iii) inference of the landslide mass, its center-of-mass velocity over time, and its trajectory.Key questions persist, such as: What can the short-period seismic data tell us about the high-frequency impacts taking place within the granular flow and along its boundaries with the underlying bedrock? And how does this seismicity relate to the bulk acceleration of the landslide and the long-period seismicity generated by it?Our recent work on the joint analysis of short- and long-period seismic signals generated by past and recent events, such as the Bingham Canyon Mine and the Oso-Steelhead landslides, provides new insights to tackle these issues. Qualitative comparison between short-period signal features and kinematic parameters inferred from long-period surface wave inversion helps to refine interpretation of the source dynamics and to understand the different mechanisms for the origin of the short-period wave radiation. Our new results also suggest that quantitative relationships can be derived from this joint analysis, in particular between the short-period seismic signal envelope and the inferred momentum of the center-of-mass. In the future, these quantitative relationships may help to constrain and calibrate parameters used in

  12. Radio-frequency transparent demodulation for broadband hybrid wireless-optical links

    DEFF Research Database (Denmark)

    Zibar, Darko; Sambaraju, Rakesh; Alemany, Ruben

    2010-01-01

    A novel demodulation technique which is transparent to radio-frequency (RF) carrier frequency is presented and experimentally demonstrated for multigigabit wireless signals. The presented demodulation technique employs optical single-sideband filtering, coherent detection, and baseband digital si...

  13. Broadband and high-efficient terahertz wave deflection based on C-shaped complex metamaterials with phase discontinuities

    KAUST Repository

    Tian, Zhen; Zhang, Xueqian; Yue, Weisheng; Gu, Jianqiang; Zhang, Shuang; Han, Jiaguang; Zhang, Weili

    2013-01-01

    A terahertz metamaterial comprised of C-shaped SRRs was experimentally devised and demonstrated to exhibit high-efficient and broadband anomalous refraction with strong phase discontinuities. The generalized refraction properties of the proposed metamaterial, including the effect of various incident angles and polarizations were investigated at broad terahertz frequencies. By employing such metasurface, we demonstrated a simple method to tailor transmission and phase of terahertz wave. © 2013 IEEE.

  14. Broadband and high-efficient terahertz wave deflection based on C-shaped complex metamaterials with phase discontinuities

    KAUST Repository

    Tian, Zhen

    2013-09-01

    A terahertz metamaterial comprised of C-shaped SRRs was experimentally devised and demonstrated to exhibit high-efficient and broadband anomalous refraction with strong phase discontinuities. The generalized refraction properties of the proposed metamaterial, including the effect of various incident angles and polarizations were investigated at broad terahertz frequencies. By employing such metasurface, we demonstrated a simple method to tailor transmission and phase of terahertz wave. © 2013 IEEE.

  15. Broadband Liner Optimization for the Source Diagnostic Test Fan

    Science.gov (United States)

    Nark, Douglas M.; Jones, Michael G.

    2012-01-01

    The broadband component of fan noise has grown in relevance with the utilization of increased bypass ratio and advanced fan designs. Thus, while the attenuation of fan tones remains paramount, the ability to simultaneously reduce broadband fan noise levels has become more appealing. This paper describes a broadband acoustic liner optimization study for the scale model Source Diagnostic Test fan. Specifically, in-duct attenuation predictions with a statistical fan source model are used to obtain optimum impedance spectra over a number of flow conditions for three liner locations in the bypass duct. The predicted optimum impedance information is then used with acoustic liner modeling tools to design liners aimed at producing impedance spectra that most closely match the predicted optimum values. Design selection is based on an acceptance criterion that provides the ability to apply increased weighting to specific frequencies and/or operating conditions. Typical tonal liner designs targeting single frequencies at one operating condition are first produced to provide baseline performance information. These are followed by multiple broadband design approaches culminating in a broadband liner targeting the full range of frequencies and operating conditions. The broadband liner is found to satisfy the optimum impedance objectives much better than the tonal liner designs. In addition, the broadband liner is found to provide better attenuation than the tonal designs over the full range of frequencies and operating conditions considered. Thus, the current study successfully establishes a process for the initial design and evaluation of novel broadband liner concepts for complex engine configurations.

  16. Characteristics of broadband slow earthquakes explained by a Brownian model

    Science.gov (United States)

    Ide, S.; Takeo, A.

    2017-12-01

    Brownian slow earthquake (BSE) model (Ide, 2008; 2010) is a stochastic model for the temporal change of seismic moment release by slow earthquakes, which can be considered as a broadband phenomena including tectonic tremors, low frequency earthquakes, and very low frequency (VLF) earthquakes in the seismological frequency range, and slow slip events in geodetic range. Although the concept of broadband slow earthquake may not have been widely accepted, most of recent observations are consistent with this concept. Then, we review the characteristics of slow earthquakes and how they are explained by BSE model. In BSE model, the characteristic size of slow earthquake source is represented by a random variable, changed by a Gaussian fluctuation added at every time step. The model also includes a time constant, which divides the model behavior into short- and long-time regimes. In nature, the time constant corresponds to the spatial limit of tremor/SSE zone. In the long-time regime, the seismic moment rate is constant, which explains the moment-duration scaling law (Ide et al., 2007). For a shorter duration, the moment rate increases with size, as often observed for VLF earthquakes (Ide et al., 2008). The ratio between seismic energy and seismic moment is constant, as shown in Japan, Cascadia, and Mexico (Maury et al., 2017). The moment rate spectrum has a section of -1 slope, limited by two frequencies corresponding to the above time constant and the time increment of the stochastic process. Such broadband spectra have been observed for slow earthquakes near the trench axis (Kaneko et al., 2017). This spectrum also explains why we can obtain VLF signals by stacking broadband seismograms relative to tremor occurrence (e.g., Takeo et al., 2010; Ide and Yabe, 2014). The fluctuation in BSE model can be non-Gaussian, as far as the variance is finite, as supported by the central limit theorem. Recent observations suggest that tremors and LFEs are spatially characteristic

  17. Dispersion-Flattened Composite Highly Nonlinear Fibre Optimised for Broadband Pulsed Four-Wave Mixing

    DEFF Research Database (Denmark)

    Lillieholm, Mads; Galili, Michael; Oxenløwe, Leif Katsuo

    2016-01-01

    We present a segmented composite HNLF optimised for mitigation of dispersion-fluctuation impairments for broadband pulsed four-wave mixing. The HNLF-segmentation allows for pulsed FWMprocessing of a 13-nm wide input WDM-signal with -4.6-dB conversion efficiency...

  18. A dual-polarized broadband planar antenna and channelizing filter bank for millimeter wavelengths

    Science.gov (United States)

    O'Brient, Roger; Ade, Peter; Arnold, Kam; Edwards, Jennifer; Engargiola, Greg; Holzapfel, William L.; Lee, Adrian T.; Myers, Michael J.; Quealy, Erin; Rebeiz, Gabriel; Richards, Paul; Suzuki, Aritoki

    2013-02-01

    We describe the design, fabrication, and testing of a broadband log-periodic antenna coupled to multiple cryogenic bolometers. This detector architecture, optimized here for astrophysical observations, simultaneously receives two linear polarizations with two octaves of bandwidth at millimeter wavelengths. The broad bandwidth signal received by the antenna is divided into sub-bands with integrated in-line frequency-selective filters. We demonstrate two such filter banks: a diplexer with two sub-bands and a log-periodic channelizer with seven contiguous sub-bands. These detectors have receiver efficiencies of 20%-40% and percent level polarization isolation. Superconducting transition-edge sensor bolometers detect the power in each sub-band and polarization. We demonstrate circularly symmetric beam patterns, high polarization isolation, accurately positioned bands, and high optical efficiency. The pixel design is applicable to astronomical observations of intensity and polarization at millimeter through sub-millimeter wavelengths. As compared with an imaging array of pixels measuring only one band, simultaneous measurements of multiple bands in each pixel has the potential to result in a higher signal-to-noise measurement while also providing spectral information. This development facilitates compact systems with high mapping speeds for observations that require information in multiple frequency bands.

  19. Implementation of PLL and FLL trackers for signals with high harmonic content and low sampling frequency

    DEFF Research Database (Denmark)

    Mathe, Laszlo; Iov, Florin; Sera, Dezso

    2014-01-01

    The accurate tracking of phase, frequency, and amplitude of different frequency components from a measured signal is an essential requirement for many digitally controlled equipment. The accurate and robust tracking of a frequency component from a complex signal was successfully applied for example...... in: grid connected inverters, sensorless motor control for rotor position estimation, grid voltage monitoring for ac-dc converters etc. Usually, the design of such trackers is done in continuous time domain. The discretization introduces errors which change the performance, especially when the input...... signal is rich in harmonics and the sampling frequency is close to the tracked frequency component. In this paper different discretization methods and implementation issues, such as Tustin, Backward-Forward Euler, are discussed and compared. A special case is analyzed, when the input signal is reach...

  20. Blind Compressed Sensing Parameter Estimation of Non-cooperative Frequency Hopping Signal

    Directory of Open Access Journals (Sweden)

    Chen Ying

    2016-10-01

    Full Text Available To overcome the disadvantages of a non-cooperative frequency hopping communication system, such as a high sampling rate and inadequate prior information, parameter estimation based on Blind Compressed Sensing (BCS is proposed. The signal is precisely reconstructed by the alternating iteration of sparse coding and basis updating, and the hopping frequencies are directly estimated based on the results. Compared with conventional compressive sensing, blind compressed sensing does not require prior information of the frequency hopping signals; hence, it offers an effective solution to the inadequate prior information problem. In the proposed method, the signal is first modeled and then reconstructed by Orthonormal Block Diagonal Blind Compressed Sensing (OBD-BCS, and the hopping frequencies and hop period are finally estimated. The simulation results suggest that the proposed method can reconstruct and estimate the parameters of noncooperative frequency hopping signals with a low signal-to-noise ratio.

  1. Multi element synthetic aperture transmission using a frequency division approach

    DEFF Research Database (Denmark)

    Gran, Fredrik; Jensen, Jørgen Arendt

    2003-01-01

    transmitted into the tissue is low. This paper describes a novel method in which the available spectrum is divided into 2N overlapping subbands. This will assure a smooth broadband high resolution spectrum when combined. The signals are grouped into two subsets in which all signals are fully orthogonal...... can therefore be used for flow imaging, unlike with Hadamard and Golay coding. The frequency division approach increases the SNR by a factor of N2 compared to conventional pulsed synthetic aperture imaging, provided that N transmission centers are used. Simulations and phantom measurements...

  2. Wide-band analog frequency modulation of optic signals using indirect techniques

    Science.gov (United States)

    Fitzmartin, D. J.; Balboni, E. J.; Gels, R. G.

    1991-01-01

    The wideband frequency modulation (FM) of an optical carrier by a radio frequency (RF) or microwave signal can be accomplished independent of laser type when indirect modulation is employed. Indirect modulators exploit the integral relation of phase to frequency so that phase modulators can be used to impress frequency modulation on an optical carrier. The use of integrated optics phase modulators, which are highly linear, enables the generation of optical wideband FM signals with very low intermodulation distortion. This modulator can be used as part of an optical wideband FM link for RF and microwave signals. Experimental results from the test of an indirect frequency modulator for an optical carrier are discussed.

  3. Suppression of high-frequency perturbations in pulse-width modulation

    DEFF Research Database (Denmark)

    2008-01-01

    A method suppresses high-frequency perturbations in a pulse-width modulated signal. The pulse-width modulation may superpose a carrier signal onto an input signal having a predetermined modulation frequency. The carrier signals may be phase-shifted. The resulting modulated signals may...

  4. A low-jitter RF PLL frequency synthesizer with high-speed mixed-signal down-scaling circuits

    International Nuclear Information System (INIS)

    Tang Lu; Wang Zhigong; Xue Hong; He Xiaohu; Xu Yong; Sun Ling

    2010-01-01

    A low-jitter RF phase locked loop (PLL) frequency synthesizer with high-speed mixed-signal down-scaling circuits is proposed. Several techniques are proposed to reduce the design complexity and improve the performance of the mixed-signal down-scaling circuit in the PLL. An improved D-latch is proposed to increase the speed and the driving capability of the DMP in the down-scaling circuit. Through integrating the D-latch with 'OR' logic for dual-modulus operation, the delays associated with both the 'OR' and D-flip-flop (DFF) operations are reduced, and the complexity of the circuit is also decreased. The programmable frequency divider of the down-scaling circuit is realized in a new method based on deep submicron CMOS technology standard cells and a more accurate wire-load model. The charge pump in the PLL is also realized with a novel architecture to improve the current matching characteristic so as to reduce the jitter of the system. The proposed RF PLL frequency synthesizer is realized with a TSMC 0.18-μm CMOS process. The measured phase noise of the PLL frequency synthesizer output at 100 kHz offset from the center frequency is only -101.52 dBc/Hz. The circuit exhibits a low RMS jitter of 3.3 ps. The power consumption of the PLL frequency synthesizer is also as low as 36 mW at a 1.8 V power supply. (semiconductor integrated circuits)

  5. Design of high-power, broadband 180o pulses and mixing sequences for fast MAS solid state chemical shift correlation NMR spectroscopy

    International Nuclear Information System (INIS)

    Herbst, Christian; Herbst, Jirada; Kirschstein, Anika; Leppert, Joerg; Ohlenschlaeger, Oliver; Goerlach, Matthias; Ramachandran, Ramadurai

    2009-01-01

    An approach for the design of high-power, broadband 180 o pulses and mixing sequences for generating dipolar and scalar coupling mediated 13 C- 13 C chemical shift correlation spectra of isotopically labelled biological systems at fast magic-angle spinning frequencies without 1 H decoupling during mixing is presented. Considering RF field strengths in the range of 100-120 kHz, as typically available in MAS probes employed at high spinning speeds, and limited B 1 field inhomogeneities, the Fourier coefficients defining the phase modulation profile of the RF pulses were optimised numerically to obtain broadband inversion and refocussing pulses and mixing sequences. Experimental measurements were carried out to assess the performance characteristics of the mixing sequences reported here

  6. Biasing vector network analyzers using variable frequency and amplitude signals

    Science.gov (United States)

    Nobles, J. E.; Zagorodnii, V.; Hutchison, A.; Celinski, Z.

    2016-08-01

    We report the development of a test setup designed to provide a variable frequency biasing signal to a vector network analyzer (VNA). The test setup is currently used for the testing of liquid crystal (LC) based devices in the microwave region. The use of an AC bias for LC based devices minimizes the negative effects associated with ionic impurities in the media encountered with DC biasing. The test setup utilizes bias tees on the VNA test station to inject the bias signal. The square wave biasing signal is variable from 0.5 to 36.0 V peak-to-peak (VPP) with a frequency range of DC to 10 kHz. The test setup protects the VNA from transient processes, voltage spikes, and high-frequency leakage. Additionally, the signals to the VNA are fused to ½ amp and clipped to a maximum of 36 VPP based on bias tee limitations. This setup allows us to measure S-parameters as a function of both the voltage and the frequency of the applied bias signal.

  7. Sensibility to Changes of Vibrational Modes of Excited Electron: Sum Frequency Signals Versus Difference Frequency Signals

    International Nuclear Information System (INIS)

    Gu Anna; Liang Xianting

    2011-01-01

    In this paper, we investigate a two electronic level system with vibrational modes coupled to a Brownian oscillator bath. The difference frequency generation (DFG) signals and sum frequency generation (SFG) signals are calculated. It is shown that, for the same model, the SFG signals are more sensitive than the DFG signals to the changes of the vibrational modes of the electronic two-level system. Because the SFG conversion efficiency can be improved by using the time-delay method, the findings in this paper predict that the SFG spectrum may probe the changes of the microstructure more effectively. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  8. Investigation of non-uniform airflow signal oscillation during high frequency chest compression

    Directory of Open Access Journals (Sweden)

    Lee Jongwon

    2005-05-01

    Full Text Available Abstract Background High frequency chest compression (HFCC is a useful and popular therapy for clearing bronchial airways of excessive or thicker mucus. Our observation of respiratory airflow of a subject during use of HFCC showed the airflow oscillation by HFCC was strongly influenced by the nonlinearity of the respiratory system. We used a computational model-based approach to analyse the respiratory airflow during use of HFCC. Methods The computational model, which is based on previous physiological studies and represented by an electrical circuit analogue, was used for simulation of in vivo protocol that shows the nonlinearity of the respiratory system. Besides, airflow was measured during use of HFCC. We compared the simulation results to either the measured data or the previous research, to understand and explain the observations. Results and discussion We could observe two important phenomena during respiration pertaining to the airflow signal oscillation generated by HFCC. The amplitudes of HFCC airflow signals varied depending on spontaneous airflow signals. We used the simulation results to investigate how the nonlinearity of airway resistance, lung capacitance, and inertance of air characterized the respiratory airflow. The simulation results indicated that lung capacitance or the inertance of air is also not a factor in the non-uniformity of HFCC airflow signals. Although not perfect, our circuit analogue model allows us to effectively simulate the nonlinear characteristics of the respiratory system. Conclusion We found that the amplitudes of HFCC airflow signals behave as a function of spontaneous airflow signals. This is due to the nonlinearity of the respiratory system, particularly variations in airway resistance.

  9. High-coherence mid-infrared dual-comb spectroscopy spanning 2.6 to 5.2 μm

    Science.gov (United States)

    Ycas, Gabriel; Giorgetta, Fabrizio R.; Baumann, Esther; Coddington, Ian; Herman, Daniel; Diddams, Scott A.; Newbury, Nathan R.

    2018-04-01

    Mid-infrared dual-comb spectroscopy has the potential to supplant conventional Fourier-transform spectroscopy in applications requiring high resolution, accuracy, signal-to-noise ratio and speed. Until now, mid-infrared dual-comb spectroscopy has been limited to narrow optical bandwidths or low signal-to-noise ratios. Using digital signal processing and broadband frequency conversion in waveguides, we demonstrate a mid-infrared dual-comb spectrometer covering 2.6 to 5.2 µm with comb-tooth resolution, sub-MHz frequency precision and accuracy, and a spectral signal-to-noise ratio as high as 6,500. As a demonstration, we measure the highly structured, broadband cross-section of propane from 2,840 to 3,040 cm-1, the complex phase/amplitude spectra of carbonyl sulfide from 2,000 to 2,100 cm-1, and of a methane, acetylene and ethane mixture from 2,860 to 3,400 cm-1. The combination of broad bandwidth, comb-mode resolution and high brightness will enable accurate mid-infrared spectroscopy in precision laboratory experiments and non-laboratory applications including open-path atmospheric gas sensing, process monitoring and combustion.

  10. Cluster observations of high-frequency waves in the exterior cusp

    Directory of Open Access Journals (Sweden)

    Y. Khotyaintsev

    2004-07-01

    Full Text Available We study wave emissions, in the frequency range from above the lower hybrid frequency up to the plasma frequency, observed during one of the Cluster crossings of a high-beta exterior cusp region on 4 March 2003. Waves are localized near narrow current sheets with a thickness a few times the ion inertial length; currents are strong, of the order of 0.1-0.5μA/m2 (0.1-0.5mA/m2 when mapped to ionosphere. The high frequency part of the waves, frequencies above the electron-cyclotron frequency, is analyzed in more detail. These high frequency waves can be broad-band, can have spectral peaks at the plasma frequency or spectral peaks at frequencies below the plasma frequency. The strongest wave emissions usually have a spectral peak near the plasma frequency. The wave emission intensity and spectral character change on a very short time scale, of the order of 1s. The wave emissions with strong spectral peaks near the plasma frequency are usually seen on the edges of the narrow current sheets. The most probable generation mechanism of high frequency waves are electron beams via bump-on-tail or electron two-stream instability. Buneman and ion-acoustic instability can be excluded as a possible generation mechanism of waves. We suggest that high frequency waves are generated by electron beams propagating along the separatrices of the reconnection region.

  11. Broadband Millimeter-Wave In-Phase and Out-of-Phase Waveguide Dividers with High Isolation

    Science.gov (United States)

    Dong, Jun; Liu, Yu; Yang, Ziqiang; Peng, Hao; Yang, Tao

    2015-11-01

    In this paper, two novel broadband in-phase and out-of-phase waveguide power dividers with high isolation are presented. Based on the substrate-integrated waveguide (SIW) divider and SIW-to-waveguide transition circuit, two kinds of E-plane waveguide dividers have been implemented. Due to the features of in-phase and out-of-phase performances, the proposed waveguide dividers can provide much more flexibilities than that of conventional E-plane waveguide T-junction. A broadband phase and amplitude performances are achieved across the whole Ka-band owing to the wideband characteristic of the SIW divider and transition circuits. To minimize the size and loss of the divider, a compact and low-loss SIW-to-waveguide transition circuit has been developed using the antisymmetric tapered probes. Two prototypes of the Ka-band waveguide dividers, including the in-phase and out-of-phase types, have been fabricated and measured. Measured results show that the isolation, input return loss, output return loss, amplitude imbalance, and phase imbalance of the in-phase divider are better than 15.5, 13.1, 10.8, 0.4 dB, and 3.50, while those of the out-of-phase divider are better than 15.0, 13.4, 10.4, 0.5 dB, and 3.60, respectively, over the frequency range from 26.5 to 40 GHz. The measured results agree well with the simulated ones. Considering their wide bandwidth, high isolation, good port matching performance, and compact configuration, the two types of waveguide dividers can be good candidates for broadband applications in millimeter-wave waveguide systems.

  12. Broadband illumination of superconducting pair breaking photon detectors

    International Nuclear Information System (INIS)

    Guruswamy, T; Goldie, D J; Withington, S

    2016-01-01

    Understanding the detailed behaviour of superconducting pair breaking photon detectors such as Kinetic Inductance Detectors (KIDs) requires knowledge of the nonequilibrium quasiparticle energy distributions. We have previously calculated the steady state distributions resulting from uniform absorption of monochromatic sub gap and above gap frequency radiation by thin films. In this work, we use the same methods to calculate the effect of illumination by broadband sources, such as thermal radiation from astrophysical phenomena or from the readout system. Absorption of photons at multiple above gap frequencies is shown to leave unchanged the structure of the quasiparticle energy distribution close to the superconducting gap. Hence for typical absorbed powers, we find the effects of absorption of broadband pair breaking radiation can simply be considered as the sum of the effects of absorption of many monochromatic sources. Distribution averaged quantities, like quasiparticle generation efficiency η, match exactly a weighted average over the bandwidth of the source of calculations assuming a monochromatic source. For sub gap frequencies, however, distributing the absorbed power across multiple frequencies does change the low energy quasiparticle distribution. For moderate and high absorbed powers, this results in a significantly larger η–a higher number of excess quasiparticles for a broadband source compared to a monochromatic source of equal total absorbed power. Typically in KIDs the microwave power absorbed has a very narrow bandwidth, but in devices with broad resonance characteristics (low quality factors), this increase in η may be measurable. (paper)

  13. Demonstrations of analog-to-digital conversion using a frequency domain stretched processor.

    Science.gov (United States)

    Reibel, Randy Ray; Harrington, Calvin; Dahl, Jason; Ostrander, Charles; Roos, Peter Aaron; Berg, Trenton; Mohan, R Krishna; Neifeld, Mark A; Babbitt, Wm R

    2009-07-06

    The first proof-of-concept demonstrations are presented for a broadband photonic-assisted analog-to-digital converter (ADC) based on spatial spectral holography (SSH). The SSH-ADC acts as a frequency-domain stretch processor converting high bandwidth input signals to low bandwidth output signals, allowing the system to take advantage of high performance, low bandwidth electronic ADCs. Demonstrations with 50 MHz effective bandwidth are shown to highlight basic performance with approximately 5 effective bits of vertical resolution. Signal capture with 1600 MHz effective bandwidth is also shown. Because some SSH materials span over 100 GHz and have large time apertures (approximately 10 micros), this technique holds promise as a candidate for the next generation of ADCs.

  14. A methodology for low-speed broadband rotational energy harvesting using piezoelectric transduction and frequency up-conversion

    International Nuclear Information System (INIS)

    Fu, Hailing; Yeatman, Eric M.

    2017-01-01

    Energy harvesting from vibration for low-power electronics has been investigated intensively in recent years, but rotational energy harvesting is less investigated and still has some challenges. In this paper, a methodology for low-speed rotational energy harvesting using piezoelectric transduction and frequency up-conversion is analysed. The system consists of a piezoelectric cantilever beam with a tip magnet and a rotating magnet on a revolving host. The angular kinetic energy of the host is transferred to the vibration energy of the piezoelectric beam via magnetic coupling between the magnets. Frequency up-conversion is achieved by magnetic plucking, converting low frequency rotation into high frequency vibration of the piezoelectric beam. A distributed-parameter theoretical model is presented to analyse the electromechanical behaviour of the rotational energy harvester. Different configurations and design parameters were investigated to improve the output power of the device. Experimental studies were conducted to validate the theoretical estimation. The results illustrate that the proposed method is a feasible solution to collecting low-speed rotational energy from ambient hosts, such as vehicle tires, micro-turbines and wristwatches. - Highlights: • A topology to harvest low-frequency broad-band rotational energy is studied. • Different configurations were considered; arrangement (a)-repulsive was the best. • Theoretical analysis shows the harvester has a wide bandwidth at low frequency. • The ripples of output power are related to the beam's natural frequency. • Experimental results show a good performance (over 20 μW) from 15 Hz to 35 Hz.

  15. Broadband electromagnetic analysis of compacted kaolin

    International Nuclear Information System (INIS)

    Bore, Thierry; Scheuermann, Alexander; Wagner, Norman; Cai, Caifang

    2017-01-01

    The mechanical compaction of soil influences not only the mechanical strength and compressibility but also the hydraulic behavior in terms of hydraulic conductivity and soil suction. At the same time, electric and dielectric parameters are increasingly used to characterize soil and to relate them with mechanic and hydraulic parameters. In the presented study electromagnetic soil properties and suction were measured under defined conditions of standardized compaction tests. The impact of external mechanical stress conditions of nearly pure kaolinite was analyzed on soil suction and broadband electromagnetic soil properties. An experimental procedure was developed and validated to simultaneously determine mechanical, hydraulic and broadband (1 MHz–3 GHz) electromagnetic properties of the porous material. The frequency dependent electromagnetic properties were modeled with a classical mixture equation (advanced Lichtenecker and Rother model, ALRM) and a hydraulic-mechanical-electromagnetic coupling approach was introduced considering water saturation, soil structure (bulk density, porosity), soil suction (pore size distribution, water sorption) as well as electrical conductivity of the aqueous pore solution. Moreover, the relaxation behavior was analyzed with a generalized fractional relaxation model concerning a high-frequency water process and two interface processes extended with an apparent direct current conductivity contribution. The different modeling approaches provide a satisfactory agreement with experimental data for the real part. These results show the potential of broadband electromagnetic approaches for quantitative estimation of the hydraulic state of the soil during densification. (paper)

  16. Temperature controlled infrared broadband cloaking with the bilayer coatings of semiconductor and superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiaohua [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); College of Physics and Electronics, Yancheng Teachers University, Yancheng 224051 (China); Liu, Youwen, E-mail: ywliu@nuaa.edu.cn [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Feng, Yuncai [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)

    2015-06-15

    Highlights: • We first propose that the cloak is composed of the bilayer of semiconductor and superconductor. • We realize the infrared broadband cloaking based on the scattering cancellation method. • The cloaking frequency can be tuned by external temperature. - Abstract: The infrared broadband tunable cloaking have been proposed and investigated with the bilayer coating materials of semiconductor (n-Ge) and high-temperature superconductor (YBa{sub 2}Cu{sub 3}O{sub 7}), whose cloaking frequency can be controlled by external temperature. The analytical solution is derived based on the scattering cancellation cloaking technique from the Mie scattering theory, and the full-wave numerical simulation is performed by the finite element method. The calculated and simulated results have demonstrated that this invisibility cloak may reduce the total scattering cross section of the composite structure of 90% over a broad frequency band of nearly 20 THz, and the infrared cloaking frequency can be tuned by the external temperature. It can provide a feasible way to design a broadband tunable cloak.

  17. Broadband phase difference method for ultrasonic velocimetry in molten glass

    International Nuclear Information System (INIS)

    Kikura, Hiroshige; Ihara, Tomonori

    2016-01-01

    This study aims to develop ultrasonic Doppler velocimetry in molten glass. Realization of such a technique has two difficulties: ultrasonic transmission into molten salt and Doppler signal processing. Buffer rod technique was developed in our research to transmit ultrasound into high temperature molten glass. This article discusses newly developed signal processing technique named broadband phase difference method. (J.P.N.)

  18. Acoustic-Seismic Coupling of Broadband Signals - Analysis of Potential Disturbances during CTBT On-Site Inspection Measurements

    Science.gov (United States)

    Liebsch, Mattes; Altmann, Jürgen

    2015-04-01

    For the verification of the Comprehensive Nuclear Test Ban Treaty (CTBT) the precise localisation of possible underground nuclear explosion sites is important. During an on-site inspection (OSI) sensitive seismic measurements of aftershocks can be performed, which, however, can be disturbed by other signals. To improve the quality and effectiveness of these measurements it is essential to understand those disturbances so that they can be reduced or prevented. In our work we focus on disturbing signals caused by airborne sources: When the sound of aircraft (as often used by the inspectors themselves) hits the ground, it propagates through pores in the soil. Its energy is transferred to the ground and soil vibrations are created which can mask weak aftershock signals. The understanding of the coupling of acoustic waves to the ground is still incomplete. However, it is necessary to improve the performance of an OSI, e.g. to address potential consequences for the sensor placement, the helicopter trajectories etc. We present our recent advances in this field. We performed several measurements to record sound pressure and soil velocity produced by various sources, e.g. broadband excitation by jet aircraft passing overhead and signals artificially produced by a speaker. For our experimental set-up microphones were placed close to the ground and geophones were buried in different depths in the soil. Several sensors were shielded from the directly incident acoustic signals by a box coated with acoustic damping material. While sound pressure under the box was strongly reduced, the soil velocity measured under the box was just slightly smaller than outside of it. Thus these soil vibrations were mostly created outside the box and travelled through the soil to the sensors. This information is used to estimate characteristic propagation lengths of the acoustically induced signals in the soil. In the seismic data we observed interference patterns which are likely caused by the

  19. Optimization of the poro-serrated trailing edges for airfoil broadband noise reduction.

    Science.gov (United States)

    Chong, Tze Pei; Dubois, Elisa

    2016-08-01

    This paper reports an aeroacoustic investigation of a NACA0012 airfoil with a number of poro-serrated trailing edge devices that contain porous materials of various air flow resistances at the gaps between adjacent members of the serrated-sawtooth trailing edge. The main objective of this work is to determine whether multiple-mechanisms on the broadband noise reduction can co-exist on a poro-serrated trailing edge. When the sawtooth gaps are filled with porous material of low-flow resistivity, the vortex shedding tone at low-frequency could not be completely suppressed at high-velocity, but a reasonably good broadband noise reduction can be achieved at high-frequency. When the sawtooth gaps are filled with porous material of very high-flow resistivity, no vortex shedding tone is present, but the serration effect on the broadband noise reduction becomes less effective. An optimal choice of the flow resistivity for a poro-serrated configuration has been identified, where it can surpass the conventional serrated trailing edge of the same geometry by achieving a further 1.5 dB reduction in the broadband noise while completely suppressing the vortex shedding tone. A weakened turbulent boundary layer noise scattering at the poro-serrated trailing edge is reflected by the lower-turbulence intensity at the near wake centreline across the whole spanwise wavelength of the sawtooth.

  20. Ultra-high-speed Optical Signal Processing using Silicon Photonics

    DEFF Research Database (Denmark)

    Oxenløwe, Leif Katsuo; Ji, Hua; Jensen, Asger Sellerup

    with a photonic layer on top to interconnect them. For such systems, silicon is an attractive candidate enabling both electronic and photonic control. For some network scenarios, it may be beneficial to use optical on-chip packet switching, and for high data-density environments one may take advantage...... of the ultra-fast nonlinear response of silicon photonic waveguides. These chips offer ultra-broadband wavelength operation, ultra-high timing resolution and ultra-fast response, and when used appropriately offer energy-efficient switching. In this presentation we review some all-optical functionalities based...... on silicon photonics. In particular we use nano-engineered silicon waveguides (nanowires) [1] enabling efficient phasematched four-wave mixing (FWM), cross-phase modulation (XPM) or self-phase modulation (SPM) for ultra-high-speed optical signal processing of ultra-high bit rate serial data signals. We show...

  1. A Design of Double Broadband MIMO Antenna

    Directory of Open Access Journals (Sweden)

    Yanfeng Geng

    2015-01-01

    Full Text Available The MIMO antenna applied to LTE mobile system should be miniaturization and can work in the current communication frequency band; isolation between each antenna unit also should be good so as to reduce loss of radio wave energy and improve the antenna performance of the MIMO system. This paper puts forward the design scheme of a broadband MIMO double antenna. And the design of antenna unit and debugging and related technical measures, such as bending antenna bracket, are both presented; the integration design of high isolation of ultra broadband MIMO antenna is realized on the plate with the volume of 100 × 52 × 0.8 mm3; antenna working bands are 698 MHz~960 MHz and 1710 MHz~2700 MHz; in the whole spectrum, the 10 dB of port isolation can be basically achieved; in low frequency band, the isolation degree of antenna port can reach 12 dB.

  2. Laser generated ultrasound sources using polymer nanocomposites for high frequency metrology

    KAUST Repository

    Rajagopal, Srinath

    2017-11-22

    Accurate characterisation of ultrasound fields generated by diagnostic and therapeutic transducers is critical for patient safety. This requires hydrophones calibrated to a traceable standard. The existing implementation of the primary standard at the National Measurement Institutes, e.g., NPL and PTB, can provide accurate calibration to a maximum frequency of 40MHz. However, the increasing use of high frequencies for both imaging and therapy necessitates calibrations to frequencies well beyond this range. For this to be possible, a source of high amplitude, broadband, quasi-planar and stable ultrasound fields is required. This is difficult to achieve using conventional piezoelectric sources, but laser generated ultrasound is a promising technique in this regard. In this study various polymer-carbon nanotube nanocomposites (PNC) were fabricated and tested for their suitability for such an application.

  3. Frequency-dependent absorbance of broadband terahertz wave in dense plasma sheet

    Science.gov (United States)

    Peng, Yan; Qi, Binbin; Jiang, Xiankai; Zhu, Zhi; Zhao, Hongwei; Zhu, Yiming

    2018-05-01

    Due to the ability of accurate fingerprinting and low-ionization for different substances, terahertz (THz) technology has a lot of crucial applications in material analysis, information transfer, and safety inspection, etc. However, the spectral characteristic of atmospheric gas and ionized gas has not been widely investigated, which is important for the remote sensing application. Here, in this paper, we investigate the absorbance of broadband terahertz wave in dense plasma sheet generated by femtosecond laser pulses. It was found that as the terahertz wave transmits through the plasma sheet formed, respectively, in carbon dioxide, oxygen, argon and nitrogen, spectrum presents completely different and frequency-dependent absorbance. The reasons for these absorption peaks are related to the molecular polarity, electric charge, intermolecular and intramolecular interactions, and collisional absorption of gas molecules. These results have significant implications for the remote sensing of gas medium.

  4. Broadband electron spin resonance experiments using superconducting coplanar waveguides

    Energy Technology Data Exchange (ETDEWEB)

    Clauss, Conrad; Bogani, Lapo; Scheffler, Marc; Dressel, Martin [1. Physikalisches Institut, Universitaet Stuttgart (Germany); Bothner, Daniel; Koelle, Dieter; Kleiner, Reinhold [Physikalisches Institut - Experimentalphysik II and Center for Collective Quantum Phenomena in LISA+, Universitaet Tuebingen (Germany)

    2012-07-01

    In recent years superconducting coplanar devices operating at microwave/GHz frequencies are employed in more and more experimental studies. Here, we present electron spin resonance (ESR) experiments using a superconducting coplanar waveguide to provide the RF field to drive the spin flips. In contrast to conventional ESR studies this allows broadband frequency as well as magnetic field swept observation of the spin resonance. We show experimental data of the spin resonance of the organic radical NitPhoMe (2-(4'-methoxyphenyl)-4,4,5,5-tetra-methylimidazoline-1-oxyl-3-oxide) for frequencies in the range of 1 GHz to 40 GHz and corresponding magnetic fields up to 1.4 T (for g=2). In addition we show the temperature dependence of the ESR signals for temperatures up to 30 K, which is well above the critical temperature of the niobium superconductor.

  5. Broadband plasmon induced transparency in terahertz metamaterials

    International Nuclear Information System (INIS)

    Zhu Zhihua; Yang Xu; Gu Jianqiang; Jiang Jun; Tian Zhen; Han Jiaguang; Zhang Weili; Yue Weisheng; Tonouchi, Masayoshi

    2013-01-01

    Plasmon induced transparency (PIT) could be realized in metamaterials via interference between different resonance modes. Within the sharp transparency window, the high dispersion of the medium may lead to remarkable slow light phenomena and an enhanced nonlinear effect. However, the transparency mode is normally localized in a narrow frequency band, which thus restricts many of its applications. Here we present the simulation, implementation, and measurement of a broadband PIT metamaterial functioning in the terahertz regime. By integrating four U-shape resonators around a central bar resonator, a broad transparency window across a frequency range greater than 0.40 THz is obtained, with a central resonance frequency located at 1.01 THz. Such PIT metamaterials are promising candidates for designing slow light devices, highly sensitive sensors, and nonlinear elements operating over a broad frequency range. (paper)

  6. Water-based metamaterial absorbers for optical transparency and broadband microwave absorption

    Science.gov (United States)

    Pang, Yongqiang; Shen, Yang; Li, Yongfeng; Wang, Jiafu; Xu, Zhuo; Qu, Shaobo

    2018-04-01

    Naturally occurring water is a promising candidate for achieving broadband absorption. In this work, by virtue of the optically transparent character of the water, the water-based metamaterial absorbers (MAs) are proposed to achieve the broadband absorption at microwave frequencies and optical transparence simultaneously. For this purpose, the transparent indium tin oxide (ITO) and polymethyl methacrylate (PMMA) are chosen as the constitutive materials. The water is encapsulated between the ITO backed plate and PMMA, serving as the microwave loss as well as optically transparent material. Numerical simulations show that the broadband absorption with the efficiency over 90% in the frequency band of 6.4-30 GHz and highly optical transparency of about 85% in the visible region can be achieved and have been well demonstrated experimentally. Additionally, the proposed water-based MA displays a wide-angle absorption performance for both TE and TM waves and is also robust to the variations of the structure parameters, which is much desired in a practical application.

  7. PSpice modeling of broadband RF cavities for transient and frequency domain simulations

    Energy Technology Data Exchange (ETDEWEB)

    Harzheim, Jens [Institut fuer Theorie Elektromagnetischer Felder, Fachgebiet Beschleunigertechnik, TU Darmstadt (Germany)

    2016-07-01

    In the future accelerator facility FAIR, Barrier-Bucket Systems will play an important role for different longitudinal beam manipulations. As the function of this type of system is to provide single sine gap voltages, the components of the system have to operate in a broad frequency range. To investigate the different effects and to design the different system components, the whole Barrier-Bucket System is to be modeled in PSpice. While for low power signals, the system shows linear behavior, nonlinear effects arise at higher amplitudes. Therefore, simulations in both, frequency and time domain are needed. The highly frequency dependent magnetic alloy ring cores of the future Barrier-Bucket cavity have been mod eled in a first step and based on these models, the whole cavity was analyzed in PSpice. The simulation results show good agreement with former measurements.

  8. Instantaneous and Frequency-Warped Signal Processing Techniques for Auditory Source Separation.

    Science.gov (United States)

    Wang, Avery Li-Chun

    This thesis summarizes several contributions to the areas of signal processing and auditory source separation. The philosophy of Frequency-Warped Signal Processing is introduced as a means for separating the AM and FM contributions to the bandwidth of a complex-valued, frequency-varying sinusoid p (n), transforming it into a signal with slowly-varying parameters. This transformation facilitates the removal of p (n) from an additive mixture while minimizing the amount of damage done to other signal components. The average winding rate of a complex-valued phasor is explored as an estimate of the instantaneous frequency. Theorems are provided showing the robustness of this measure. To implement frequency tracking, a Frequency-Locked Loop algorithm is introduced which uses the complex winding error to update its frequency estimate. The input signal is dynamically demodulated and filtered to extract the envelope. This envelope may then be remodulated to reconstruct the target partial, which may be subtracted from the original signal mixture to yield a new, quickly-adapting form of notch filtering. Enhancements to the basic tracker are made which, under certain conditions, attain the Cramer -Rao bound for the instantaneous frequency estimate. To improve tracking, the novel idea of Harmonic -Locked Loop tracking, using N harmonically constrained trackers, is introduced for tracking signals, such as voices and certain musical instruments. The estimated fundamental frequency is computed from a maximum-likelihood weighting of the N tracking estimates, making it highly robust. The result is that harmonic signals, such as voices, can be isolated from complex mixtures in the presence of other spectrally overlapping signals. Additionally, since phase information is preserved, the resynthesized harmonic signals may be removed from the original mixtures with relatively little damage to the residual signal. Finally, a new methodology is given for designing linear-phase FIR filters

  9. New results on the generation of broadband electrostatic waves in the magnetotail

    Science.gov (United States)

    Grabbe, C. L.

    1985-01-01

    The theory of the generation of broadband electrostatic noise (BEN) in the magnetotail is extended through numerical solution of the dispersion relation under conditions that exist in the plasma sheet boundary layer. It is found that the low-frequency portion of the spectrum has a broad angular spectrum but a fairly sharp peak near 75 deg with respect to the magnetic field, while the high-frequency portion has a narrower angular spectrum that is strongly concentrated along the magnetic field line. These results are in excellent agreement with observations of the broadband wave spectrum and a recent measurement of the propagation direction. The effect of a second cold component of electrons is analyzed, and it is found that it can increase the upper cutoff frequency of BEN to the observed value at about the plasma frequency.

  10. Simultaneous topography imaging and broadband nanomechanical mapping on atomic force microscope

    Science.gov (United States)

    Li, Tianwei; Zou, Qingze

    2017-12-01

    In this paper, an approach is proposed to achieve simultaneous imaging and broadband nanomechanical mapping of soft materials in air by using an atomic force microscope. Simultaneous imaging and nanomechanical mapping are needed, for example, to correlate the morphological and mechanical evolutions of the sample during dynamic phenomena such as the cell endocytosis process. Current techniques for nanomechanical mapping, however, are only capable of capturing static elasticity of the material, or the material viscoelasticity in a narrow frequency band around the resonant frequency(ies) of the cantilever used, not competent for broadband nanomechanical mapping, nor acquiring topography image of the sample simultaneously. These limitations are addressed in this work by enabling the augmentation of an excitation force stimuli of rich frequency spectrum for nanomechanical mapping in the imaging process. Kalman-filtering technique is exploited to decouple and split the mixed signals for imaging and mapping, respectively. Then the sample indentation generated is quantified online via a system-inversion method, and the effects of the indentation generated and the topography tracking error on the topography quantification are taken into account. Moreover, a data-driven feedforward-feedback control is utilized to track the sample topography. The proposed approach is illustrated through experimental implementation on a polydimethylsiloxane sample with a pre-fabricated pattern.

  11. Ultra-broadband and high-efficiency polarization conversion metasurface with multiple plasmon resonance modes

    International Nuclear Information System (INIS)

    Dong Guo-Xiang; Xia Song; Li Wei; Zhang An-Xue; Xu Zhuo; Wei Xiao-Yong; Shi Hong-Yu

    2016-01-01

    In this paper, we present a novel metasurface design that achieves a high-efficiency ultra-broadband cross polarization conversion. The metasurface is composed of an array of unit resonators, each of which combines an H-shaped structure and two rectangular metallic patches. Different plasmon resonance modes are excited in unit resonators and allow the polarization states to be manipulated. The bandwidth of the cross polarization converter is 82% of the central frequency, covering the range from 15.7 GHz to 37.5 GHz. The conversion efficiency of the innovative new design is higher than 90%. At 14.43 GHz and 40.95 GHz, the linearly polarized incident wave is converted into a circularly polarized wave. (paper)

  12. A Broadband Metasurface-Based Terahertz Flat-Lens Array

    KAUST Repository

    Wang, Qiu; Zhang, Xueqian; Xu, Yuehong; Tian, Zhen; Gu, Jianqiang; Yue, Weisheng; Zhang, Shuang; Han, Jiaguang; Zhang, Weili; Zhang, Weili

    2015-01-01

    A metasurface-based terahertz flat-lens array is proposed, comprising C-shaped split-ring resonators exhibiting locally engineerable phase discontinuities. Possessing a high numerical aperture, the planar lens array is flexible, robust, and shows excellent focusing characteristics in a broadband terahertz frequency. It could be an important step towards the development of planar terahertz focusing devices for practical applications.

  13. A Broadband Metasurface-Based Terahertz Flat-Lens Array

    KAUST Repository

    Wang, Qiu

    2015-02-12

    A metasurface-based terahertz flat-lens array is proposed, comprising C-shaped split-ring resonators exhibiting locally engineerable phase discontinuities. Possessing a high numerical aperture, the planar lens array is flexible, robust, and shows excellent focusing characteristics in a broadband terahertz frequency. It could be an important step towards the development of planar terahertz focusing devices for practical applications.

  14. Readout for intersatellite laser interferometry: Measuring low frequency phase fluctuations of high-frequency signals with microradian precision

    DEFF Research Database (Denmark)

    Gerberding, Oliver; Diekmann, Christian; Kullmann, Joachim

    2015-01-01

    Precision phase readout of optical beat note signals is one of the core techniques required for inter-satellite laser interferometry. Future space based gravitational wave detectors like eLISA require such a readout over a wide range of MHz frequencies, due to orbit induced Doppler shifts...

  15. Frequency-resolved measurement of the orbital angular momentum spectrum of femtosecond ultra-broadband optical-vortex pulses based on field reconstruction

    International Nuclear Information System (INIS)

    Yamane, Keisaku; Yang, Zhili; Toda, Yasunori; Morita, Ryuji

    2014-01-01

    We propose a high-precision method for measuring the orbital angular momentum (OAM) spectrum of ultra-broadband optical-vortex (OV) pulses from fork-like interferograms between OV pulses and a reference plane-wave pulse. It is based on spatial reconstruction of the electric fields of the pulses to be measured from the frequency-resolved interference pattern. Our method is demonstrated experimentally by obtaining the OAM spectra for different spectral components of the OV pulses, enabling us to characterize the frequency dispersion of the topological charge of the OAM spectrum by a simple experimental setup. Retrieval is carried out in quasi-real time, allowing us to investigate OAM spectra dynamically. Furthermore, we determine the relative phases (including the sign) of the topological-charge-resolved electric-field amplitudes, which are significant for evaluating OVs or OV pulses with arbitrarily superposed modes. (paper)

  16. A Novel Partial Discharge Ultra-High Frequency Signal De-Noising Method Based on a Single-Channel Blind Source Separation Algorithm

    Directory of Open Access Journals (Sweden)

    Liangliang Wei

    2018-02-01

    Full Text Available To effectively de-noise the Gaussian white noise and periodic narrow-band interference in the background noise of partial discharge ultra-high frequency (PD UHF signals in field tests, a novel de-noising method, based on a single-channel blind source separation algorithm, is proposed. Compared with traditional methods, the proposed method can effectively de-noise the noise interference, and the distortion of the de-noising PD signal is smaller. Firstly, the PD UHF signal is time-frequency analyzed by S-transform to obtain the number of source signals. Then, the single-channel detected PD signal is converted into multi-channel signals by singular value decomposition (SVD, and background noise is separated from multi-channel PD UHF signals by the joint approximate diagonalization of eigen-matrix method. At last, the source PD signal is estimated and recovered by the l1-norm minimization method. The proposed de-noising method was applied on the simulation test and field test detected signals, and the de-noising performance of the different methods was compared. The simulation and field test results demonstrate the effectiveness and correctness of the proposed method.

  17. Broadband plasmon induced transparency in terahertz metamaterials

    KAUST Repository

    Zhu, Zhihua

    2013-04-25

    Plasmon induced transparency (PIT) could be realized in metamaterials via interference between different resonance modes. Within the sharp transparency window, the high dispersion of the medium may lead to remarkable slow light phenomena and an enhanced nonlinear effect. However, the transparency mode is normally localized in a narrow frequency band, which thus restricts many of its applications. Here we present the simulation, implementation, and measurement of a broadband PIT metamaterial functioning in the terahertz regime. By integrating four U-shape resonators around a central bar resonator, a broad transparency window across a frequency range greater than 0.40 THz is obtained, with a central resonance frequency located at 1.01 THz. Such PIT metamaterials are promising candidates for designing slow light devices, highly sensitive sensors, and nonlinear elements operating over a broad frequency range. © 2013 IOP Publishing Ltd.

  18. Decoding a combined amplitude modulated and frequency modulated signal

    DEFF Research Database (Denmark)

    2015-01-01

    The present disclosure relates to a method for decoding a combined AM/FM encoded signal, comprising the steps of: combining said encoded optical signal with light from a local oscillator configured with a local oscillator frequency; converting the combined local oscillator and encoded optical...... signal into one or more electrical signals by means of at least one opto-electrical converter having a predefined frequency bandwidth, thereby providing an amplified and encoded electrical signal having one or more encoded signal current(s), where one type of states have a higher oscillation frequency...... than other type of states; rectifying the encoded signal current(s), thereby obtaining an encoded power spectrum, wherein said power spectrum has different states, such as "0"-states and "1"-states, with different power levels such that they can be discriminated, said local oscillator frequency...

  19. Reconfigurable Signal Processing and Hardware Architecture for Broadband Wireless Communications

    Directory of Open Access Journals (Sweden)

    Liang Ying-Chang

    2005-01-01

    Full Text Available This paper proposes a broadband wireless transceiver which can be reconfigured to any type of cyclic-prefix (CP -based communication systems, including orthogonal frequency-division multiplexing (OFDM, single-carrier cyclic-prefix (SCCP system, multicarrier (MC code-division multiple access (MC-CDMA, MC direct-sequence CDMA (MC-DS-CDMA, CP-based CDMA (CP-CDMA, and CP-based direct-sequence CDMA (CP-DS-CDMA. A hardware platform is proposed and the reusable common blocks in such a transceiver are identified. The emphasis is on the equalizer design for mobile receivers. It is found that after block despreading operation, MC-DS-CDMA and CP-DS-CDMA have the same equalization blocks as OFDM and SCCP systems, respectively, therefore hardware and software sharing is possible for these systems. An attempt has also been made to map the functional reconfigurable transceiver onto the proposed hardware platform. The different functional entities which will be required to perform the reconfiguration and realize the transceiver are explained.

  20. From spectral holeburning memory to spatial-spectral microwave signal processing

    International Nuclear Information System (INIS)

    Babbitt, Wm Randall; Barber, Zeb W; Harrington, Calvin; Mohan, R Krishna; Sharpe, Tia; Bekker, Scott H; Chase, Michael D; Merkel, Kristian D; Stiffler, Colton R; Traxinger, Aaron S; Woidtke, Alex J

    2014-01-01

    Many storage and processing systems based on spectral holeburning have been proposed that access the broad bandwidth and high dynamic range of spatial-spectral materials, but only recently have practical systems been developed that exceed the performance and functional capabilities of electronic devices. This paper reviews the history of the proposed applications of spectral holeburning and spatial-spectral materials, from frequency domain optical memory to microwave photonic signal processing systems. The recent results of a 20 GHz bandwidth high performance spectrum monitoring system with the additional capability of broadband direction finding demonstrates the potential for spatial-spectral systems to be the practical choice for solving demanding signal processing problems in the near future. (paper)

  1. Noninvasive Diagnosis of Coronary Artery Disease Using 12-Lead High-Frequency Electrocardiograms

    Science.gov (United States)

    Schlegel, Todd T.; Arenare, Brian

    2006-01-01

    A noninvasive, sensitive method of diagnosing certain pathological conditions of the human heart involves computational processing of digitized electrocardiographic (ECG) signals acquired from a patient at all 12 conventional ECG electrode positions. In the processing, attention is focused on low-amplitude, high-frequency components of those portions of the ECG signals known in the art as QRS complexes. The unique contribution of this method lies in the utilization of signal features and combinations of signal features from various combinations of electrode positions, not reported previously, that have been found to be helpful in diagnosing coronary artery disease and such related pathological conditions as myocardial ischemia, myocardial infarction, and congestive heart failure. The electronic hardware and software used to acquire the QRS complexes and perform some preliminary analyses of their high-frequency components were summarized in Real-Time, High-Frequency QRS Electrocardiograph (MSC- 23154), NASA Tech Briefs, Vol. 27, No. 7 (July 2003), pp. 26-28. To recapitulate, signals from standard electrocardiograph electrodes are preamplified, then digitized at a sampling rate of 1,000 Hz, then analyzed by the software that detects R waves and QRS complexes and analyzes them from several perspectives. The software includes provisions for averaging signals over multiple beats and for special-purpose nonrecursive digital filters with specific low- and high-frequency cutoffs. These filters, applied to the averaged signal, effect a band-pass operation in the frequency range from 150 to 250 Hz. The output of the bandpass filter is the desired high-frequency QRS signal. Further processing is then performed in real time to obtain the beat-to-beat root mean square (RMS) voltage amplitude of the filtered signal, certain variations of the RMS voltage, and such standard measures as the heart rate and R-R interval at any given time. A key signal feature analyzed in the present

  2. Broadband enhancement of infrared absorption in microbolometers using Ag nanocrystals

    International Nuclear Information System (INIS)

    Hyun, Jerome K.; Ahn, Chi Won; Kim, Woo Choong; Kim, Tae Hyun; Hyun, Moon Seop; Kim, Hee Yeoun; Park, Jae Hong; Lee, Won-Oh

    2015-01-01

    High performance microbolometers are widely sought for thermal imaging applications. In order to increase the performance limits of microbolometers, the responsivity of the device to broadband infrared (IR) radiation needs to be improved. In this work, we report a simple, quick, and cost-effective approach to modestly enhance the broadband IR response of the device by evaporating Ag nanocrystals onto the light entrance surface of the device. When irradiated with IR light, strong fields are built up within the gaps between adjacent Ag nanocrystals. These fields resistively generate heat in the nanocrystals and underlying substrate, which is transduced into an electrical signal via a resistive sensing element in the device. Through this method, we are able to enhance the IR absorption over a broadband spectrum and improve the responsivity of the device by ∼11%

  3. High-speed broadband elastic actuator in water using induced-charge electro-osmosis with a skew structure

    Science.gov (United States)

    Sugioka, Hideyuki; Nakano, Naoki

    2018-01-01

    An artificial cilium using ac electro-osmosis (ACEO) is attractive because of its large potentiality for innovative microfluidic applications. However, the ACEO cilium has not been probed experimentally and has a shortcoming that the working frequency range is very narrow. Thus, we here propose an ACEO elastic actuator having a skew structure that broadens a working frequency range and experimentally demonstrate that the elastic actuator in water can be driven with a high-speed (˜10 Hz) and a wide frequency range (˜0.1 to ˜10 kHz). Moreover, we propose a simple self-consistent model that explains the broadband characteristic due to the skew structure with other characteristics. By comparing the theoretical results with the experimental results, we find that they agree fairly well. We believe that our ACEO elastic actuator will play an important role in microfluidics in the future.

  4. High-speed broadband elastic actuator in water using induced-charge electro-osmosis with a skew structure.

    Science.gov (United States)

    Sugioka, Hideyuki; Nakano, Naoki

    2018-01-01

    An artificial cilium using ac electro-osmosis (ACEO) is attractive because of its large potentiality for innovative microfluidic applications. However, the ACEO cilium has not been probed experimentally and has a shortcoming that the working frequency range is very narrow. Thus, we here propose an ACEO elastic actuator having a skew structure that broadens a working frequency range and experimentally demonstrate that the elastic actuator in water can be driven with a high-speed (∼10 Hz) and a wide frequency range (∼0.1 to ∼10 kHz). Moreover, we propose a simple self-consistent model that explains the broadband characteristic due to the skew structure with other characteristics. By comparing the theoretical results with the experimental results, we find that they agree fairly well. We believe that our ACEO elastic actuator will play an important role in microfluidics in the future.

  5. Time-frequency analysis of phonocardiogram signals using wavelet transform: a comparative study.

    Science.gov (United States)

    Ergen, Burhan; Tatar, Yetkin; Gulcur, Halil Ozcan

    2012-01-01

    Analysis of phonocardiogram (PCG) signals provides a non-invasive means to determine the abnormalities caused by cardiovascular system pathology. In general, time-frequency representation (TFR) methods are used to study the PCG signal because it is one of the non-stationary bio-signals. The continuous wavelet transform (CWT) is especially suitable for the analysis of non-stationary signals and to obtain the TFR, due to its high resolution, both in time and in frequency and has recently become a favourite tool. It decomposes a signal in terms of elementary contributions called wavelets, which are shifted and dilated copies of a fixed mother wavelet function, and yields a joint TFR. Although the basic characteristics of the wavelets are similar, each type of the wavelets produces a different TFR. In this study, eight real types of the most known wavelets are examined on typical PCG signals indicating heart abnormalities in order to determine the best wavelet to obtain a reliable TFR. For this purpose, the wavelet energy and frequency spectrum estimations based on the CWT and the spectra of the chosen wavelets were compared with the energy distribution and the autoregressive frequency spectra in order to determine the most suitable wavelet. The results show that Morlet wavelet is the most reliable wavelet for the time-frequency analysis of PCG signals.

  6. Broadband polymer microstructured THz fiber coupler with downdoped cores

    DEFF Research Database (Denmark)

    Nielsen, Kristian; Rasmussen, Henrik K.; Bang, Ole

    2010-01-01

    We demonstrate a broadband THz directional coupler based on a dual core photonic crystal fiber (PCF) design with mechanically down-doped core regions. For a center frequency of 1.3 THz we demonstrate a bandwidth of 0.65 THz.......We demonstrate a broadband THz directional coupler based on a dual core photonic crystal fiber (PCF) design with mechanically down-doped core regions. For a center frequency of 1.3 THz we demonstrate a bandwidth of 0.65 THz....

  7. Broadband photosensor with a tunable frequency range, built on the basis of nanoscale carbon structure with field localization

    Science.gov (United States)

    Yakunin, Alexander N.; Akchurin, Garif G.; Aban'shin, Nikolay P.; Gorfinkel, Boris I.

    2014-03-01

    The work is devoted to the development of a new direction in creating of broadband photo sensors which distinctive feature is the possibility of dynamic adjustment of operating frequency range. The author's results of study of red threshold control of classic photoelectric effect were the basis for the work implementation. This effect was predicted theoretically and observed experimentally during irradiation of nanoscale carbon structure of planar-edge type by stream of low-energy photons. The variation of the accelerating voltage within a small range allows you to change photoelectric threshold for carbon in a wide range - from UV to IR. This is the consequence of the localization of electrostatic field at tip of the blade planar structure and of changes in the conditions of non-equilibrium electrons tunneling from the boundary surface of the cathode into the vacuum. The generation of nonequilibrium electrons in the carbon film thickness of 20 nm has a high speed which provides high performance of photodetector. The features of the use of nanoscale carbon structure photocurrent registration as in the prethreshold regime, and in the mode of field emission existence are discussed. The results of simulation and experimental examination of photosensor samples are given. It is shown that the observed effect is a single-photon tunneling. This in combination with the possibility of highspeed dynamic tuning determines the good perspectives for creation of new devices working in the mode of select multiple operating spectral bands for the signal recording. The architecture of such devices is expected to be significantly simpler than the conventional ones, based on the use of tunable filters.

  8. High Frequency Amplitude Detector for GMI Magnetic Sensors

    Directory of Open Access Journals (Sweden)

    Aktham Asfour

    2014-12-01

    Full Text Available A new concept of a high-frequency amplitude detector and demodulator for Giant-Magneto-Impedance (GMI sensors is presented. This concept combines a half wave rectifier, with outstanding capabilities and high speed, and a feedback approach that ensures the amplitude detection with easily adjustable gain. The developed detector is capable of measuring high-frequency and very low amplitude signals without the use of diode-based active rectifiers or analog multipliers. The performances of this detector are addressed throughout the paper. The full circuitry of the design is given, together with a comprehensive theoretical study of the concept and experimental validation. The detector has been used for the amplitude measurement of both single frequency and pulsed signals and for the demodulation of amplitude-modulated signals. It has also been successfully integrated in a GMI sensor prototype. Magnetic field and electrical current measurements in open- and closed-loop of this sensor have also been conducted.

  9. A low-cost, high-performance, digital signal processor-based lock-in amplifier capable of measuring multiple frequency sweeps simultaneously

    International Nuclear Information System (INIS)

    Sonnaillon, Maximiliano Osvaldo; Bonetto, Fabian Jose

    2005-01-01

    A high-performance digital lock-in amplifier implemented in a low-cost digital signal processor (DSP) board is described. This lock in is capable of measuring simultaneously multiple frequencies that change in time as frequency sweeps (chirps). The used 32-bit DSP has enough computing power to generate N=3 simultaneous reference signals and accurately measure the N=3 responses, operating as three lock ins connected in parallel to a linear system. The lock in stores the measured values in memory until they are downloaded to the a personal computer (PC). The lock in works in stand-alone mode and can be programmed and configured through the PC serial port. Downsampling and multiple filter stages were used in order to obtain a sharp roll off and a long time constant in the filters. This makes measurements possible in presence of high-noise levels. Before each measurement, the lock in performs an autocalibration that measures the frequency response of analog output and input circuitry in order to compensate for the departure from ideal operation. Improvements from previous lock-in implementations allow measuring the frequency response of a system in a short time. Furthermore, the proposed implementation can measure how the frequency response changes with time, a characteristic that is very important in our biotechnological application. The number of simultaneous components that the lock in can generate and measure can be extended, without reprogramming, by only using other DSPs of the same family that are code compatible and work at higher clock frequencies

  10. A low-cost, high-performance, digital signal processor-based lock-in amplifier capable of measuring multiple frequency sweeps simultaneously

    Energy Technology Data Exchange (ETDEWEB)

    Sonnaillon, Maximiliano Osvaldo; Bonetto, Fabian Jose [Laboratorio de Cavitacion y Biotecnologia, San Carlos de Bariloche (8400) (Argentina)

    2005-02-01

    A high-performance digital lock-in amplifier implemented in a low-cost digital signal processor (DSP) board is described. This lock in is capable of measuring simultaneously multiple frequencies that change in time as frequency sweeps (chirps). The used 32-bit DSP has enough computing power to generate N=3 simultaneous reference signals and accurately measure the N=3 responses, operating as three lock ins connected in parallel to a linear system. The lock in stores the measured values in memory until they are downloaded to the a personal computer (PC). The lock in works in stand-alone mode and can be programmed and configured through the PC serial port. Downsampling and multiple filter stages were used in order to obtain a sharp roll off and a long time constant in the filters. This makes measurements possible in presence of high-noise levels. Before each measurement, the lock in performs an autocalibration that measures the frequency response of analog output and input circuitry in order to compensate for the departure from ideal operation. Improvements from previous lock-in implementations allow measuring the frequency response of a system in a short time. Furthermore, the proposed implementation can measure how the frequency response changes with time, a characteristic that is very important in our biotechnological application. The number of simultaneous components that the lock in can generate and measure can be extended, without reprogramming, by only using other DSPs of the same family that are code compatible and work at higher clock frequencies.

  11. Tunable and broadband microwave frequency combs based on a semiconductor laser with incoherent optical feedback

    International Nuclear Information System (INIS)

    Zhao Mao-Rong; Wu Zheng-Mao; Deng Tao; Zhou Zhen-Li; Xia Guang-Qiong

    2015-01-01

    Based on a semiconductor laser (SL) with incoherent optical feedback, a novel all-optical scheme for generating tunable and broadband microwave frequency combs (MFCs) is proposed and investigated numerically. The results show that, under suitable operation parameters, the SL with incoherent optical feedback can be driven to operate at a regular pulsing state, and the generated MFCs have bandwidths broader than 40 GHz within a 10 dB amplitude variation. For a fixed bias current, the line spacing (or repetition frequency) of the MFCs can be easily tuned by varying the feedback delay time and the feedback strength, and the tuning range of the line spacing increases with the increase in the bias current. The linewidth of the MFCs is sensitive to the variation of the feedback delay time and the feedback strength, and a linewidth of tens of KHz can be achieved through finely adjusting the feedback delay time and the feedback strength. In addition, mappings of amplitude variation, repetition frequency, and linewidth of MFCs in the parameter space of the feedback delay time and the feedback strength are presented. (paper)

  12. Ultra-broadband carpet cloak for transverse-electric polarization

    International Nuclear Information System (INIS)

    Deng, Ye; Xu, Su; Zhang, Runren; Zheng, Bin; Chen, Hongsheng; Chen, Hua; Yu, Faxin; Gao, Fei; Zhang, Baile

    2016-01-01

    Magnetism is a necessity in constructing macroscopic metamaterial invisibility cloaks that are theoretically designed by transformation optics, but will generally limit the cloaking bandwidth to an impractically narrow range. To meet the broad bandwidth demand, magnetism has been fully abandoned in previous demonstrations of macroscopic carpet cloaking, whose approach, however, cannot apply to a transverse-electric (TE) polarization. To fill this gap, here we experimentally demonstrate an ultra-broadband magnetic carpet cloak for the TE polarization. The cloak is made of non-resonant closed-ring metamaterials with little dispersion and the cloaking performance is confirmed with both time-domain simulation and frequency scanning measurement over a broad bandwidth corresponding to a pulse signal illumination. (paper)

  13. Ultra-broadband carpet cloak for transverse-electric polarization

    Science.gov (United States)

    Deng, Ye; Xu, Su; Zhang, Runren; Zheng, Bin; Chen, Hua; Gao, Fei; Yu, Faxin; Zhang, Baile; Chen, Hongsheng

    2016-04-01

    Magnetism is a necessity in constructing macroscopic metamaterial invisibility cloaks that are theoretically designed by transformation optics, but will generally limit the cloaking bandwidth to an impractically narrow range. To meet the broad bandwidth demand, magnetism has been fully abandoned in previous demonstrations of macroscopic carpet cloaking, whose approach, however, cannot apply to a transverse-electric (TE) polarization. To fill this gap, here we experimentally demonstrate an ultra-broadband magnetic carpet cloak for the TE polarization. The cloak is made of non-resonant closed-ring metamaterials with little dispersion and the cloaking performance is confirmed with both time-domain simulation and frequency scanning measurement over a broad bandwidth corresponding to a pulse signal illumination.

  14. Wavelet-OFDM Signal Transmission Characteristics with High-Speed PLC Modem

    Science.gov (United States)

    Nakagawa, Kenichi; Tokuda, Masamitsu; Igata, Yuji

    In this paper, we measured the interference immunity characteristics of high-speed PLC system using Wavelet-OFDM when the narrowband conducted interference wave signal was injected. As the results, it was clear that (1) measured PHY rate at the all frequency band hardly decreased in C/I (Carrier to Interference ratio) of above 20dB, but began to decrease rapidly in C/I of below 0dB when the interference signal was injected in the frequency band of high-speed PLC signal, (2) when C/I became from 0dB to -20dB, the measured PHY rate at the frequency existing the notch band were improved around 10Mbps than that at the frequency not existing the notch band, (3) when the narrowband interference wave was injected outside of frequency band of high-speed PLC signal, the measured PHY rate did not decrease than that in each notch band. Therefore, it was revealed that high-speed PLC system using Wavelet-OFDM had good interference immunity characteristics.

  15. High Temperature, High Frequency Fuel Metering Valve, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Active Signal Technologies and its subcontractor Moog propose to develop a high-frequency actuator driven valve intended to achieve TRL 6 by the end of Phase II....

  16. Ultra-high throughput real-time instruments for capturing fast signals and rare events

    Science.gov (United States)

    Buckley, Brandon Walter

    Wide-band signals play important roles in the most exciting areas of science, engineering, and medicine. To keep up with the demands of exploding internet traffic, modern data centers and communication networks are employing increasingly faster data rates. Wide-band techniques such as pulsed radar jamming and spread spectrum frequency hopping are used on the battlefield to wrestle control of the electromagnetic spectrum. Neurons communicate with each other using transient action potentials that last for only milliseconds at a time. And in the search for rare cells, biologists flow large populations of cells single file down microfluidic channels, interrogating them one-by-one, tens of thousands of times per second. Studying and enabling such high-speed phenomena pose enormous technical challenges. For one, parasitic capacitance inherent in analog electrical components limits their response time. Additionally, converting these fast analog signals to the digital domain requires enormous sampling speeds, which can lead to significant jitter and distortion. State-of-the-art imaging technologies, essential for studying biological dynamics and cells in flow, are limited in speed and sensitivity by finite charge transfer and read rates, and by the small numbers of photo-electrons accumulated in short integration times. And finally, ultra-high throughput real-time digital processing is required at the backend to analyze the streaming data. In this thesis, I discuss my work in developing real-time instruments, employing ultrafast optical techniques, which overcome some of these obstacles. In particular, I use broadband dispersive optics to slow down fast signals to speeds accessible to high-bit depth digitizers and signal processors. I also apply telecommunication multiplexing techniques to boost the speeds of confocal fluorescence microscopy. The photonic time stretcher (TiSER) uses dispersive Fourier transformation to slow down analog signals before digitization and

  17. On chip frequency discriminator for microwave photonics signal processing

    NARCIS (Netherlands)

    Marpaung, D.A.I.; Roeloffzen, C.G.H.

    2012-01-01

    Microwave photonics (MWP) techniques for the generation, distribution and pro- cessing of radio frequency (RF) signals have enjoyed a surge of interest in the last few years. The workhorse behind these MWP functionalities is a high performance MWP link. Such a link needs to fulfill several criteria

  18. Cortical feedback signals generalise across different spatial frequencies of feedforward inputs.

    Science.gov (United States)

    Revina, Yulia; Petro, Lucy S; Muckli, Lars

    2017-09-22

    Visual processing in cortex relies on feedback projections contextualising feedforward information flow. Primary visual cortex (V1) has small receptive fields and processes feedforward information at a fine-grained spatial scale, whereas higher visual areas have larger, spatially invariant receptive fields. Therefore, feedback could provide coarse information about the global scene structure or alternatively recover fine-grained structure by targeting small receptive fields in V1. We tested if feedback signals generalise across different spatial frequencies of feedforward inputs, or if they are tuned to the spatial scale of the visual scene. Using a partial occlusion paradigm, functional magnetic resonance imaging (fMRI) and multivoxel pattern analysis (MVPA) we investigated whether feedback to V1 contains coarse or fine-grained information by manipulating the spatial frequency of the scene surround outside an occluded image portion. We show that feedback transmits both coarse and fine-grained information as it carries information about both low (LSF) and high spatial frequencies (HSF). Further, feedback signals containing LSF information are similar to feedback signals containing HSF information, even without a large overlap in spatial frequency bands of the HSF and LSF scenes. Lastly, we found that feedback carries similar information about the spatial frequency band across different scenes. We conclude that cortical feedback signals contain information which generalises across different spatial frequencies of feedforward inputs. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  19. Generation of broadband electrostatic noise by electron acoustic solitons

    International Nuclear Information System (INIS)

    Dubouloz, N.; Pottelette, R.; Malingre, M.; Treumann, R.A.

    1991-01-01

    Broadband electrostatic noise (BEN) bursts whose amplitude sometimes reaches about 100 mV m -1 have been observed by the Viking satellite in the dayside auroral zone. These emissions have been shown to be greatly influenced by nonlinear effects and to occur simultaneously with the observation of particle distributions favouring the destabilization of the electron acoustic mode. It is shown that electron acoustic solitons passing by the satellite would generate spectra that can explain the high-frequency part of BEN, above the electron plasma frequency

  20. Experimental separation of a frequency spin echo signal

    International Nuclear Information System (INIS)

    Bun'kov, Yu.M.; Dmitriev, V.V.

    1981-01-01

    To study systems with bound nuclear-electron precession CsMnF 2 antiferromagnetic light-plane monocrystal was investigated. Crystal orientation was carried out by roentgenoscopy. Measurements were performed at helium temperatures in the 500-700 MHz frequency range. A NMR pulsed spectrometer with generators of both resonance and doubled frequency was used to produce an echo signal (to study by the parametric echo method). It was shown that the theory of the formation of a frequency modulated echo (FM echo) did not fully describe the properties of the echo signals in systems with dynamic frequency shift (DFS). An intense spin echo signal, which formation was apparently connected with other nonlinear properties of the systems with nuclear-electron precession, was observed. The spin echo signal in magnetics with DFS, which properties correspond to notions of the frequency mechanism of echo formation, was experimentally separated. As a result of the investigations it had been possible to settle contradictions between the theory of FM echo formation and the experimental results for the last 9 years. It turned out that the mechanism of FM echo formation in the magnetics with bound nuclear-electron precession was effective only at large delay times between the pulses. In the range of small delays the FM echo is ''jammed'' by a gigantic echo signal of a nature different from that of the traditional FM signal. The constant of gigantic echo intensity drop at increasing delay between the pulses weakly depends on spin-spin relaxation time [ru

  1. High-frequency, three-phase current controller implementation in an FPGA

    Energy Technology Data Exchange (ETDEWEB)

    Hartmann, M.; Round, S. D.; Kolar, J. W.

    2008-07-01

    Three phase rectifiers with switching frequencies of 500 kHz or more require high speed current controllers. At such high switching frequencies analog controllers as well as high speed digital signal processing (DSP) systems have limited performance. In this paper, two high speed current controller implementations using two different field-programmable gate arrays (FPGA) - one for switching frequencies up to 1 MHz and one for switching frequencies beyond 1 MHz - are presented to overcome this performance limitation. Starting with the digital system design all the blocks of the signal chain, containing analog-to-digital (A/D) interface, digital controller implementation using HW-multipliers and implementation of a novel high speed, high resolution pulse width modulation (PWM) are discussed and compared. Final measurements verify the performance of the controllers. (author)

  2. The promise of downlink MU-MIMO for high-capacity next generation mobile broadband networks based on IEEE 802.16 m

    OpenAIRE

    Papathanassiou Apostolos; Davydov Alexei

    2011-01-01

    Abstract The dramatic increase of the demand for mobile broadband services poses stringent requirements on the performance evolution of currently deployed mobile broadband networks, such as Mobile WiMAX Release 1 and 3GPP LTE Release 8. Although the combination of single-user multiple-input multiple-output (SU-MIMO) and orthogonal frequency division multiple access (OFDMA) provide the appropriate technologies for improving the downlink performance of third generation (3G) code division multip...

  3. Detrimental Effect Elimination of Laser Frequency Instability in Brillouin Optical Time Domain Reflectometer by Using Self-Heterodyne Detection

    Directory of Open Access Journals (Sweden)

    Yongqian Li

    2017-03-01

    Full Text Available A useful method for eliminating the detrimental effect of laser frequency instability on Brillouin signals by employing the self-heterodyne detection of Rayleigh and Brillouin scattering is presented. From the analysis of Brillouin scattering spectra from fibers with different lengths measured by heterodyne detection, the maximum usable pulse width immune to laser frequency instability is obtained to be about 4 µs in a self-heterodyne detection Brillouin optical time domain reflectometer (BOTDR system using a broad-band laser with low frequency stability. Applying the self-heterodyne detection of Rayleigh and Brillouin scattering in BOTDR system, we successfully demonstrate that the detrimental effect of laser frequency instability on Brillouin signals can be eliminated effectively. Employing the broad-band laser modulated by a 130-ns wide pulse driven electro-optic modulator, the observed maximum errors in temperatures measured by the local heterodyne and self-heterodyne detection BOTDR systems are 7.9 °C and 1.2 °C, respectively.

  4. Gender Identification Using High-Frequency Speech Energy: Effects of Increasing the Low-Frequency Limit.

    Science.gov (United States)

    Donai, Jeremy J; Halbritter, Rachel M

    The purpose of this study was to investigate the ability of normal-hearing listeners to use high-frequency energy for gender identification from naturally produced speech signals. Two experiments were conducted using a repeated-measures design. Experiment 1 investigated the effects of increasing high-pass filter cutoff (i.e., increasing the low-frequency spectral limit) on gender identification from naturally produced vowel segments. Experiment 2 studied the effects of increasing high-pass filter cutoff on gender identification from naturally produced sentences. Confidence ratings for the gender identification task were also obtained for both experiments. Listeners in experiment 1 were capable of extracting talker gender information at levels significantly above chance from vowel segments high-pass filtered up to 8.5 kHz. Listeners in experiment 2 also performed above chance on the gender identification task from sentences high-pass filtered up to 12 kHz. Cumulatively, the results of both experiments provide evidence that normal-hearing listeners can utilize information from the very high-frequency region (above 4 to 5 kHz) of the speech signal for talker gender identification. These findings are at variance with current assumptions regarding the perceptual information regarding talker gender within this frequency region. The current results also corroborate and extend previous studies of the use of high-frequency speech energy for perceptual tasks. These findings have potential implications for the study of information contained within the high-frequency region of the speech spectrum and the role this region may play in navigating the auditory scene, particularly when the low-frequency portion of the spectrum is masked by environmental noise sources or for listeners with substantial hearing loss in the low-frequency region and better hearing sensitivity in the high-frequency region (i.e., reverse slope hearing loss).

  5. Broadband W-band Rapid Frequency Sweep Considerations for Fourier Transform EPR.

    Science.gov (United States)

    Strangeway, Robert A; Hyde, James S; Camenisch, Theodore G; Sidabras, Jason W; Mett, Richard R; Anderson, James R; Ratke, Joseph J; Subczynski, Witold K

    2017-12-01

    A multi-arm W-band (94 GHz) electron paramagnetic resonance spectrometer that incorporates a loop-gap resonator with high bandwidth is described. A goal of the instrumental development is detection of free induction decay following rapid sweep of the microwave frequency across the spectrum of a nitroxide radical at physiological temperature, which is expected to lead to a capability for Fourier transform electron paramagnetic resonance. Progress toward this goal is a theme of the paper. Because of the low Q-value of the loop-gap resonator, it was found necessary to develop a new type of automatic frequency control, which is described in an appendix. Path-length equalization, which is accomplished at the intermediate frequency of 59 GHz, is analyzed. A directional coupler is favored for separation of incident and reflected power between the bridge and the loop-gap resonator. Microwave leakage of this coupler is analyzed. An oversize waveguide with hyperbolic-cosine tapers couples the bridge to the loop-gap resonator, which results in reduced microwave power and signal loss. Benchmark sensitivity data are provided. The most extensive application of the instrument to date has been the measurement of T 1 values using pulse saturation recovery. An overview of that work is provided.

  6. An ultra-broadband multilayered graphene absorber

    KAUST Repository

    Amin, Muhammad; Farhat, Mohamed; Bagci, Hakan

    2013-01-01

    An ultra-broadband multilayered graphene absorber operating at terahertz (THz) frequencies is proposed. The absorber design makes use of three mechanisms: (i) The graphene layers are asymmetrically patterned to support higher order surface plasmon

  7. Input signal shaping based on harmonic frequency response function for suppressing nonlinear optical frequency in frequency-scanning interferometry

    Science.gov (United States)

    Zhu, Yu; Liu, Zhigang; Deng, Wen; Deng, Zhongwen

    2018-05-01

    Frequency-scanning interferometry (FSI) using an external cavity diode laser (ECDL) is essential for many applications of the absolute distance measurement. However, owing to the hysteresis and creep of the piezoelectric actuator inherent in the ECDL, the optical frequency scanning exhibits a nonlinearity that seriously affects the phase extraction accuracy of the interference signal and results in the reduction of the measurement accuracy. To suppress the optical frequency nonlinearity, a harmonic frequency synthesis method for shaping the desired input signal instead of the original triangular wave is presented. The effectiveness of the presented shaping method is demonstrated through the comparison of the experimental results. Compared with an incremental Renishaw interferometer, the standard deviation of the displacement measurement of the FSI system is less than 2.4 μm when driven by the shaped signal.

  8. Broadband short pulse measurement by autocorrelation with a sum-frequency generation set-up

    International Nuclear Information System (INIS)

    Glotin, F.; Jaroszynski, D.; Marcouille, O.

    1995-01-01

    Previous spectral and laser pulse length measurements carried out on the CLIO FEL at wavelength λ=8.5 μm suggested that very short light pulses could be generated, about 500 fs wide (FWHM). For these measurements a Michelson interferometer with a Te crystal, as a non-linear detector, was used as a second order autocorrelation device. More recent measurements in similar conditions have confirmed that the laser pulses observed are indeed single: they are not followed by other pulses distant by the slippage length Nλ. As the single micropulse length is likely to depend on the slippage, more measurements at different wavelengths would be useful. This is not directly possible with our actual interferometer set-up, based on a phase-matched non-linear crystal. However, we can use the broadband non-linear medium provided by one of our users' experiments: Sum-Frequency Generation over surfaces. With such autocorrelation set-up, interference fringes are no more visible, but this is largely compensated by the frequency range provided. First tests at 8 μm have already been performed to validate the technic, leading to results similar to those obtained with our previous Michelson set-up

  9. A large coaxial reflection cell for broadband dielectric characterization of coarse-grained materials

    Science.gov (United States)

    Bore, Thierry; Bhuyan, Habibullah; Bittner, Tilman; Murgan, Vignesh; Wagner, Norman; Scheuermann, Alexander

    2018-01-01

    Knowledge of the frequency-dependent electromagnetic properties of coarse-grained materials is imperative for the successful application of high frequency electromagnetic measurement techniques for near and subsurface monitoring. This paper reports the design, calibration and application of a novel one-port large coaxial cell for broadband complex permittivity measurements of civil engineering materials. It was designed to allow the characterization of heterogeneous material with large aggregate dimensions (up to 28 mm) over a frequency range from 1 MHz-860 MHz. In the first step, the system parameters were calibrated using the measured scattering function in a perfectly known dielectric material in an optimization scheme. In the second step, the method was validated with measurements made on standard liquids. Then the performance of the cell was evaluated on a compacted coarse-grained soil. The dielectric spectra were obtained by means of fitting the measured scattering function using a transverse electromagnetic mode propagation model considering the frequency-dependent complex permittivity. Two scenarios were systematically analyzed and compared. The first scenario consisted of a broadband generalized dielectric relaxation model with two Cole-Cole type relaxation processes related to the interaction of the aqueous phase and the solid phase, a constant high frequency contribution as well as an apparent direct current conductivity term. The second scenario relied on a three-phase theoretical mixture equation which was used in a forward approach in order to calibrate the model. Both scenarios provide almost identical results for the broadband effective complex relative permittivity. The combination of both scenarios suggests the simultaneous estimation of water content, density, bulk and pore water conductivity for road base materials for in situ applications.

  10. ALMA High Frequency Techniques

    Science.gov (United States)

    Meyer, J. D.; Mason, B.; Impellizzeri, V.; Kameno, S.; Fomalont, E.; Chibueze, J.; Takahashi, S.; Remijan, A.; Wilson, C.; ALMA Science Team

    2015-12-01

    The purpose of the ALMA High Frequency Campaign is to improve the quality and efficiency of science observing in Bands 8, 9, and 10 (385-950 GHz), the highest frequencies available to the ALMA project. To this end, we outline observing modes which we have demonstrated to improve high frequency calibration for the 12m array and the ACA, and we present the calibration of the total power antennas at these frequencies. Band-to-band (B2B) transfer and bandwidth switching (BWSW), techniques which improve the speed and accuracy of calibration at the highest frequencies, are most necessary in Bands 8, 9, and 10 due to the rarity of strong calibrators. These techniques successfully enable increased signal-to-noise on the calibrator sources (and better calibration solutions) by measuring the calibrators at lower frequencies (B2B) or in wider bandwidths (BWSW) compared to the science target. We have also demonstrated the stability of the bandpass shape to better than 2.4% for 1 hour, hidden behind random noise, in Band 9. Finally, total power observing using the dual sideband receivers in Bands 9 and 10 requires the separation of the two sidebands; this procedure has been demonstrated in Band 9 and is undergoing further testing in Band 10.

  11. Optimization of measurement methods for a multi-frequency electromagnetic field from mobile phone base station using broadband EMF meter

    Directory of Open Access Journals (Sweden)

    Paweł Bieńkowski

    2015-10-01

    Full Text Available Background: This paper presents the characteristics of the mobile phone base station (BS as an electromagnetic field (EMF source. The most common system configurations with their construction are described. The parameters of radiated EMF in the context of the access to methods and other parameters of the radio transmission are discussed. Attention was also paid to antennas that are used in this technology. Material and Methods: The influence of individual components of a multi-frequency EMF, most commonly found in the BS surroundings, on the resultant EMF strength value indicated by popular broadband EMF meters was analyzed. The examples of metrological characteristics of the most common EMF probes and 2 measurement scenarios of the multisystem base station, with and without microwave relays, are shown. Results: The presented method for measuring the multi-frequency EMF using 2 broadband probes allows for the significant minimization of measurement uncertainty. Equations and formulas that can be used to calculate the actual EMF intensity from multi-frequency sources are shown. They have been verified in the laboratory conditions on a specific standard setup as well as in real conditions in a survey of the existing base station with microwave relays. Conclusions: Presented measurement methodology of multi-frequency EMF from BS with microwave relays, validated both in laboratory and real conditions. It has been proven that the described measurement methodology is the optimal approach to the evaluation of EMF exposure in BS surrounding. Alternative approaches with much greater uncertainty (precaution method or more complex measuring procedure (sources exclusion method are also presented. Med Pr 2015;66(5:701–712

  12. [Optimization of measurement methods for a multi-frequency electromagnetic field from mobile phone base station using broadband EMF meter].

    Science.gov (United States)

    Bieńkowski, Paweł; Cała, Paweł; Zubrzak, Bartłomiej

    2015-01-01

    This paper presents the characteristics of the mobile phone base station (BS) as an electromagnetic field (EMF) source. The most common system configurations with their construction are described. The parameters of radiated EMF in the context of the access to methods and other parameters of the radio transmission are discussed. Attention was also paid to antennas that are used in this technology. The influence of individual components of a multi-frequency EMF, most commonly found in the BS surroundings, on the resultant EMF strength value indicated by popular broadband EMF meters was analyzed. The examples of metrological characteristics of the most common EMF probes and 2 measurement scenarios of the multisystem base station, with and without microwave relays, are shown. The presented method for measuring the multi-frequency EMF using 2 broadband probes allows for the significant minimization of measurement uncertainty. Equations and formulas that can be used to calculate the actual EMF intensity from multi-frequency sources are shown. They have been verified in the laboratory conditions on a specific standard setup as well as in real conditions in a survey of the existing base station with microwave relays. Presented measurement methodology of multi-frequency EMF from BS with microwave relays, validated both in laboratory and real conditions. It has been proven that the described measurement methodology is the optimal approach to the evaluation of EMF exposure in BS surrounding. Alternative approaches with much greater uncertainty (precaution method) or more complex measuring procedure (sources exclusion method) are also presented). This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

  13. Highly nonlinear organic crystal OHQ-T for efficient ultra-broadband terahertz wave generation beyond 10 THz.

    Science.gov (United States)

    Kang, Bong Joo; Baek, In Hyung; Lee, Seung-Heon; Kim, Won Tae; Lee, Seung-Jun; Jeong, Young Uk; Kwon, O-Pil; Rotermund, Fabian

    2016-05-16

    We report on efficient generation of ultra-broadband terahertz (THz) waves via optical rectification in a novel nonlinear organic crystal with acentric core structure, i.e. 2-(4-hydroxystyryl)-1-methylquinolinium 4-methylbenzenesulfonate (OHQ-T), which possesses an ideal molecular structure leading to a maximized nonlinear optical response for near-infrared-pumped THz wave generation. By systematic studies on wavelength-dependent phase-matching conditions in OHQ-T crystals of different thicknesses we are able to generate coherent THz waves with a high peak-to-peak electric field amplitude of up to 650 kV/cm and an upper cut-off frequency beyond 10 THz. High optical-to-THz conversion efficiency of 0.31% is achieved by efficient index matching with a selective pumping at 1300 nm.

  14. Frequency identification of vibration signals using video camera image data.

    Science.gov (United States)

    Jeng, Yih-Nen; Wu, Chia-Hung

    2012-10-16

    This study showed that an image data acquisition system connecting a high-speed camera or webcam to a notebook or personal computer (PC) can precisely capture most dominant modes of vibration signal, but may involve the non-physical modes induced by the insufficient frame rates. Using a simple model, frequencies of these modes are properly predicted and excluded. Two experimental designs, which involve using an LED light source and a vibration exciter, are proposed to demonstrate the performance. First, the original gray-level resolution of a video camera from, for instance, 0 to 256 levels, was enhanced by summing gray-level data of all pixels in a small region around the point of interest. The image signal was further enhanced by attaching a white paper sheet marked with a black line on the surface of the vibration system in operation to increase the gray-level resolution. Experimental results showed that the Prosilica CV640C CMOS high-speed camera has the critical frequency of inducing the false mode at 60 Hz, whereas that of the webcam is 7.8 Hz. Several factors were proven to have the effect of partially suppressing the non-physical modes, but they cannot eliminate them completely. Two examples, the prominent vibration modes of which are less than the associated critical frequencies, are examined to demonstrate the performances of the proposed systems. In general, the experimental data show that the non-contact type image data acquisition systems are potential tools for collecting the low-frequency vibration signal of a system.

  15. Frequency Identification of Vibration Signals Using Video Camera Image Data

    Directory of Open Access Journals (Sweden)

    Chia-Hung Wu

    2012-10-01

    Full Text Available This study showed that an image data acquisition system connecting a high-speed camera or webcam to a notebook or personal computer (PC can precisely capture most dominant modes of vibration signal, but may involve the non-physical modes induced by the insufficient frame rates. Using a simple model, frequencies of these modes are properly predicted and excluded. Two experimental designs, which involve using an LED light source and a vibration exciter, are proposed to demonstrate the performance. First, the original gray-level resolution of a video camera from, for instance, 0 to 256 levels, was enhanced by summing gray-level data of all pixels in a small region around the point of interest. The image signal was further enhanced by attaching a white paper sheet marked with a black line on the surface of the vibration system in operation to increase the gray-level resolution. Experimental results showed that the Prosilica CV640C CMOS high-speed camera has the critical frequency of inducing the false mode at 60 Hz, whereas that of the webcam is 7.8 Hz. Several factors were proven to have the effect of partially suppressing the non-physical modes, but they cannot eliminate them completely. Two examples, the prominent vibration modes of which are less than the associated critical frequencies, are examined to demonstrate the performances of the proposed systems. In general, the experimental data show that the non-contact type image data acquisition systems are potential tools for collecting the low-frequency vibration signal of a system.

  16. Broadband high-resolution multi-species CARS in gas-filled hollow-core photonic crystal fiber.

    Science.gov (United States)

    Trabold, Barbara M; Hupfer, Robert J R; Abdolvand, Amir; St J Russell, Philip

    2017-09-01

    We report the use of coherent anti-Stokes Raman spectroscopy (CARS) in gas-filled hollow-core photonic crystal fiber (HC-PCF) for trace gas detection. The long optical path-lengths yield a 60 dB increase in the signal level compared with free-space arrangements. This enables a relatively weak supercontinuum (SC) to be used as Stokes seed, along with a ns pump pulse, paving the way for broadband (>4000  cm -1 ) single-shot CARS with an unprecedented resolution of ∼100  MHz. A kagomé-style HC-PCF provides broadband guidance, and, by operating close to the pressure-tunable zero dispersion wavelength, we can ensure simultaneous phase-matching of all gas species. We demonstrate simultaneous measurement of the concentrations of multiple trace gases in a gas sample introduced into the core of the HC-PCF.

  17. Theoretical and experimental study on broadband terahertz atmospheric transmission characteristics

    International Nuclear Information System (INIS)

    Guo Shi-Bei; Zhong Kai; Wang Mao-Rong; Liu Chu; Xu De-Gang; Yao Jian-Quan; Xiao Yong; Wang Wen-Peng

    2017-01-01

    Broadband terahertz (THz) atmospheric transmission characteristics from 0 to 8 THz are theoretically simulated based on a standard Van Vleck–Weisskopf line shape, considering 1696 water absorption lines and 298 oxygen absorption lines. The influences of humidity, temperature, and pressure on the THz atmospheric absorption are analyzed and experimentally verified with a Fourier transform infrared spectrometer (FTIR) system, showing good consistency. The investigation and evaluation on high-frequency atmospheric windows are good supplements to existing data in the low-frequency range and lay the foundation for aircraft-based high-altitude applications of THz communication and radar. (paper)

  18. Broadband Internet and Income Inequality

    OpenAIRE

    HOUNGBONON , Georges Vivien; Liang , Julienne

    2017-01-01

    Policy makers are aiming for a large coverage of high-speed broadband Internet. However , there is still a lack of evidence about its effects on income distribution. In this paper, we investigate the effects of fixed broadband Internet on mean income and income inequality using a unique town-level data on broadband adoption and quality in France. We find that broadband adoption and quality raise mean income and lower income inequality. These results are robust to initial conditions, and yield...

  19. Design Methodology of High Power Distributed Amplifier Employing Broadband Impedance Transformer

    DEFF Research Database (Denmark)

    Narendra, Kumar; Zhurbenko, Vitaliy; Collantes, Juan Mari

    2009-01-01

    A novel topology of a high power distributed amplifier (DA) in combination with a broadband impedance transformer is presented. The advantages of the proposed topology are explored analytically and verified by a full-wave 3D simulations. Stability of the high power DA is verified with the pole...

  20. Signal Adaptive System for Space/Spatial-Frequency Analysis

    Directory of Open Access Journals (Sweden)

    Veselin N. Ivanović

    2009-01-01

    Full Text Available This paper outlines the development of a multiple-clock-cycle implementation (MCI of a signal adaptive two-dimensional (2D system for space/spatial-frequency (S/SF signal analysis. The design is based on a method for improved S/SF representation of the analyzed 2D signals, also proposed here. The proposed MCI design optimizes critical design performances related to hardware complexity, making it a suitable system for real time implementation on an integrated chip. Additionally, the design allows the implemented system to take a variable number of clock cycles (CLKs (the only necessary ones regarding desirable—2D Wigner distribution-presentation of autoterms in different frequency-frequency points during the execution. This ability represents a major advantage of the proposed design which helps to optimize the time required for execution and produce an improved, cross-terms-free S/SF signal representation. The design has been verified by a field-programmable gate array (FPGA circuit design, capable of performing S/SF analysis of 2D signals in real time.

  1. DIRECTED SEARCHES FOR BROADBAND EXTENDED GRAVITATIONAL WAVE EMISSION IN NEARBY ENERGETIC CORE-COLLAPSE SUPERNOVAE

    Energy Technology Data Exchange (ETDEWEB)

    Van Putten, Maurice H. P. M., E-mail: mvp@sejong.ac.kr [Room 614, Astronomy and Space Science, Sejong University, 98 Gunja-Dong Gwangin-gu, Seoul 143-747 (Korea, Republic of)

    2016-03-10

    Core-collapse supernovae (CC-SNe) are factories of neutron stars and stellar-mass black holes. SNe Ib/c stand out as potentially originating in relatively compact stellar binaries and they have a branching ratio of about 1% into long gamma-ray bursts. The most energetic events probably derive from central engines harboring rapidly rotating black holes, wherein the accretion of fall-back matter down to the innermost stable circular orbit (ISCO) offers a window into broadband extended gravitational wave emission (BEGE). To search for BEGE, we introduce a butterfly filter in time–frequency space by time-sliced matched filtering. To analyze long epochs of data, we propose using coarse-grained searches followed by high-resolution searches on events of interest. We illustrate our proposed coarse-grained search on two weeks of LIGO S6 data prior to SN 2010br (z = 0.002339) using a bank of up to 64,000 templates of one-second duration covering a broad range in chirp frequencies and bandwidth. Correlating events with signal-to-noise ratios > 6 from the LIGO L1 and H1 detectors reduces the total to a few events of interest. Lacking any further properties reflecting a common excitation by broadband gravitational radiation, we disregarded these as spurious. This new pipeline may be used to systematically search for long-duration chirps in nearby CC-SNe from robotic optical transient surveys using embarrassingly parallel computing.

  2. A New High Frequency Injection Method Based on Duty Cycle Shifting without Maximum Voltage Magnitude Loss

    DEFF Research Database (Denmark)

    Wang, Dong; Lu, Kaiyuan; Rasmussen, Peter Omand

    2015-01-01

    The conventional high frequency signal injection method is to superimpose a high frequency voltage signal to the commanded stator voltage before space vector modulation. Therefore, the magnitude of the voltage used for machine torque production is limited. In this paper, a new high frequency...... amplitude. This may be utilized to develop new position estimation algorithm without involving the inductance in the medium to high speed range. As an application example, a developed inductance independent position estimation algorithm using the proposed high frequency injection method is applied to drive...... injection method, in which high frequency signal is generated by shifting the duty cycle between two neighboring switching periods, is proposed. This method allows injecting a high frequency signal at half of the switching frequency without the necessity to sacrifice the machine fundamental voltage...

  3. Noise-Immune Cavity-Enhanced Optical Frequency Comb Spectroscopy

    Science.gov (United States)

    Rutkowski, Lucile; Khodabakhsh, Amir; Johanssson, Alexandra C.; Foltynowicz, Aleksandra

    2015-06-01

    We present noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS), a recently developed technique for sensitive, broadband, and high resolution spectroscopy. In NICE-OFCS an optical frequency comb (OFC) is locked to a high finesse cavity and phase-modulated at a frequency precisely equal to (a multiple of) the cavity free spectral range. Since each comb line and sideband is transmitted through a separate cavity mode in exactly the same way, any residual frequency noise on the OFC relative to the cavity affects each component in an identical manner. The transmitted intensity contains a beat signal at the modulation frequency that is immune to frequency-to-amplitude noise conversion by the cavity, in a way similar to continuous wave noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS). The light transmitted through the cavity is detected with a fast-scanning Fourier-transform spectrometer (FTS) and the NICE-OFCS signal is obtained by fast Fourier transform of the synchronously demodulated interferogram. Our NICE-OFCS system is based on an Er:fiber femtosecond laser locked to a cavity with a finesse of ˜9000 and a fast-scanning FTS equipped with a high-bandwidth commercial detector. We measured NICE-OFCS signals from the 3νb{1}+νb{3} overtone band of CO_2 around 1.57 μm and achieved absorption sensitivity 6.4×10-11cm-1 Hz-1/2 per spectral element, corresponding to a minimum detectable CO_2 concentration of 25 ppb after 330 s integration time. We will describe the principles of the technique and its technical implementation, and discuss the spectral lineshapes of the NICE-OFCS signals. A. Khodabakhsh, C. Abd Alrahman, and A. Foltynowicz, Opt. Lett. 39, 5034-5037 (2014). J. Ye, L. S. Ma, and J. L. Hall, J. Opt. Soc. Am. B 15, 6-15 (1998). A. Khodabakhsh, A. C. Johansson, and A. Foltynowicz, Appl. Phys. B (2015) doi:10.1007/s00340-015-6010-7.

  4. AIRTV: Broadband Direct to Aircraft

    Science.gov (United States)

    Sorbello, R.; Stone, R.; Bennett, S. B.; Bertenyi, E.

    2002-01-01

    over the poles. The system consists of a constellation of 4 geostationary satellites covering the earth and delivering its signals to the aircraft at S band (2.52 -2.67 GHz). The S-band spectrum is ideal for this application since it is allocated on a primary basis by the ITU for global broadcast service. The AirTV service is expected to begin in 2004 and should be unencumbered by adjacent satellite interference due to near completion of the ITU coordination process. Each satellite will deliver four 20 Mbps QPSK data streams consisting of multiplexed compressed digital video channels and IP data over the full global beam coverage. The 80 Mbps capacity of each satellite will provide approximately 60 video channels while still allocating 40 Mbits to data services. The combined constellation capacity of 320 Mbits will significantly exceed the capacity of any similar existing or currently planned global satellite system. In addition, the simplicity of the 4-satellite approach is the most cost effective means to deliver high bandwidth globally. Return links, which are required for internet service, will be provided through the existing Inmarsat Aero-H system already onboard virtually all long haul aircraft and will provide return data rates from the aircraft as high as 432 kbps. integrated receiver/decoder (IRD) assembly. The phased array antenna, a key technology element, is being developed by AirTV's strategic partner, CMC Electronics. This antenna is a scaled version of CMC's Inmarsat Aero H antenna and is capable of scanning to 5 degrees above the horizon. Wide angle scanning up to 85 degrees from zenith is necessary for aircraft traversing the northernmost latitudes on transoceanic routes. AirTV has designed both the satellite coverage and aircraft antenna performance to ensure that high signal quality is maintained along all non-polar airline routes. AirTV will be the future of aeronautical broadband delivery. It has been designed specifically for global services and

  5. Highly Reflecting, Broadband Deformable Membrane Mirror for Wavefront Control Applications, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This Phase I STTR project will develop a highly reflecting, broadband, radiation resistant, low-stress and lightweight, membrane integrated into an electrostatically...

  6. Wide-angle, polarization-insensitive and broadband absorber based on eight-fold symmetric SRRs metamaterial

    Science.gov (United States)

    Wu, Dong; Liu, Yumin; Yu, Zhongyuan; Chen, Lei; Ma, Rui; Li, Yutong; Li, Ruifang; Ye, Han

    2016-12-01

    In this paper, we propose a novel three dimensional metamaterial design with eight-fold rotational symmetry that shows a polarization-insensitive, wide-angle and broadband perfect absorption in the microwave band. By simulation, the polarization-insensitive absorption is over 90% between 26.9 GHz to 32.9 GHz, and the broadband absorption remains a good absorption performance to a wide incident angles for both TE and TM polarizations. The magnetic field distribution are investigated to interpret the physical mechanism of broadband absorption. The broadband absorption is based on overlapping the multiple magnetic resonances at the neighboring frequencies by coupling effects of multiple metallic split-ring resonators (SRRs). Moreover, it is demonstrate that the designed structure can be extended to other frequencies by scale down the size of the unit cell, such as the visible frequencies. The simulated results show that the absorption of the smaller absorber is above 90% in the frequency range from 467 THz to 765 THz(392-642 nm), which include orange to purple light in visible region(400-760nm). The wide-angle and polarization-insensitive stabilities of the smaller absorber is also demonstrated at visible region. The proposed work provides a new design of realization of a polarization-insensitive, wide-angle and broadband absorber ranging different frequency bands, and such a structure has potential application in the fields of solar cell, imaging and detection.

  7. Flaw-size measurement in a weld samples by ultrasonic frequency analysis

    International Nuclear Information System (INIS)

    Adler, L.; Cook, K.V.; Whaley, H.L. Jr.; McClung, R.W.

    1975-01-01

    An ultrasonic frequency-analysis technique was developed and applies to characterize flaws in an 8-in. (203-mm) thick heavy-section steel weld specimen. The technique applies a multitransducer system. The spectrum of the received broad-band signal is frequency analyzed at two different receivers for each of the flaws. From the two spectra, the size and orientation of the flaw are determined by the use of an analytic model proposed earlier. (auth)

  8. Pump-To-Signal Intensity Modulation Transfer Characteristics in FOPAs: Modulation Frequency and Saturation Effect

    DEFF Research Database (Denmark)

    Lali-Dastjerdi, Zohreh; Cristofori, Valentina; Lund-Hansen, Toke

    2012-01-01

    This paper reports a comprehensive study of pump- to-signal intensity modulation transfer (IMT) in single-pump fiber optic parametric amplifiers (FOPAs). In particular, the IMT is studied for the first time for high-frequency fluctuations of the pump as well as in the saturated gain regime. The IMT...... cut-off frequency in typical single-pump FOPAs is around 100–200 GHz. The possibilities to shift this frequency based on dispersion and nonlinearities involved in the parametric gain are discussed. The severe IMT to the signal at low modulation frequencies can be suppressed by more than 50...

  9. Spectrally shaped broadband study of up-conversion in Y2O3:Er3+

    International Nuclear Information System (INIS)

    Lytle, A.L.; Gagnon, E.; Tulchinsky, L.; Krebs, J.K.

    2014-01-01

    We present a novel scheme for studying up-conversion through excited state absorption (ESA) by using a broadband excitation source with spectral shaping capabilities. Up-conversion processes have typically been investigated using a single, narrowband excitation source, when the two steps of the process are coincident in frequency, which is often made possible by broadening mechanisms of the intermediate excited state manifolds. Thus, narrowband sources are limited in the systems they can excite and what material information they can provide. With broadband light, we are able to drive up-conversion with non-coincident frequencies as well. Finally, by windowing the spectrum, we determine the optimal excitation bandwidth for low-concentration (1%) Y 2 O 3 :Er 3+ nanocrystals. - Highlights: • Broadband excitation light is used to drive up-conversion in Y 2 O 3 :Er 3+ . • Broadband light excites all available transitions in the two-photon process. • A spectral shaping technique is used to alter the excitation frequencies present. • The optimal excitation bandwidth is measured by windowing the spectrum. • Broadband excitation reveals information inaccessible by narrowband sources

  10. Broadband standard dipole antenna for antenna calibration

    Science.gov (United States)

    Koike, Kunimasa; Sugiura, Akira; Morikawa, Takao

    1995-06-01

    Antenna calibration of EMI antennas is mostly performed by the standard antenna method at an open-field test site using a specially designed dipole antenna as a reference. In order to develop broadband standard antennas, the antenna factors of shortened dipples are theoretically investigated. First, the effects of the dipole length are analyzed using the induced emf method. Then, baluns and loads are examined to determine their influence on the antenna factors. It is found that transformer-type baluns are very effective for improving the height dependence of the antenna factors. Resistive loads are also useful for flattening the frequency dependence. Based on these studies, a specification is developed for a broadband standard antenna operating in the 30 to 150 MHz frequency range.

  11. Broadband Access

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Broadband Access. Worldwide market for broadband access $30 Billion! Over 200 million broadband subscribers worldwide! Various Competing Broadband access. Digital Subscriber line; Wireless; Optical Fiber.

  12. Optimization study on inductive-resistive circuit for broadband piezoelectric energy harvesters

    Directory of Open Access Journals (Sweden)

    Ting Tan

    2017-03-01

    Full Text Available The performance of cantilever-beam piezoelectric energy harvester is usually analyzed with pure resistive circuit. The optimal performance of such a vibration-based energy harvesting system is limited by narrow bandwidth around its modified natural frequency. For broadband piezoelectric energy harvesting, series and parallel inductive-resistive circuits are introduced. The electromechanical coupled distributed parameter models for such systems under harmonic base excitations are decoupled with modified natural frequency and electrical damping to consider the coupling effect. Analytical solutions of the harvested power and tip displacement for the electromechanical decoupled model are confirmed with numerical solutions for the coupled model. The optimal performance of piezoelectric energy harvesting with inductive-resistive circuits is revealed theoretically as constant maximal power at any excitation frequency. This is achieved by the scenarios of matching the modified natural frequency with the excitation frequency and equating the electrical damping to the mechanical damping. The inductance and load resistance should be simultaneously tuned to their optimal values, which may not be applicable for very high electromechanical coupling systems when the excitation frequency is higher than their natural frequencies. With identical optimal performance, the series inductive-resistive circuit is recommended for relatively small load resistance, while the parallel inductive-resistive circuit is suggested for relatively large load resistance. This study provides a simplified optimization method for broadband piezoelectric energy harvesters with inductive-resistive circuits.

  13. Optimization study on inductive-resistive circuit for broadband piezoelectric energy harvesters

    Science.gov (United States)

    Tan, Ting; Yan, Zhimiao

    2017-03-01

    The performance of cantilever-beam piezoelectric energy harvester is usually analyzed with pure resistive circuit. The optimal performance of such a vibration-based energy harvesting system is limited by narrow bandwidth around its modified natural frequency. For broadband piezoelectric energy harvesting, series and parallel inductive-resistive circuits are introduced. The electromechanical coupled distributed parameter models for such systems under harmonic base excitations are decoupled with modified natural frequency and electrical damping to consider the coupling effect. Analytical solutions of the harvested power and tip displacement for the electromechanical decoupled model are confirmed with numerical solutions for the coupled model. The optimal performance of piezoelectric energy harvesting with inductive-resistive circuits is revealed theoretically as constant maximal power at any excitation frequency. This is achieved by the scenarios of matching the modified natural frequency with the excitation frequency and equating the electrical damping to the mechanical damping. The inductance and load resistance should be simultaneously tuned to their optimal values, which may not be applicable for very high electromechanical coupling systems when the excitation frequency is higher than their natural frequencies. With identical optimal performance, the series inductive-resistive circuit is recommended for relatively small load resistance, while the parallel inductive-resistive circuit is suggested for relatively large load resistance. This study provides a simplified optimization method for broadband piezoelectric energy harvesters with inductive-resistive circuits.

  14. High Power Combiner/Divider with Coupled Lines for Broadband Applications

    Science.gov (United States)

    2017-03-20

    novel isolation structure will also be presented. I. INTRODUCTION Power divider/combiners are traditionally used in the development of high power ...a novel Gysel divider/combiner structure have been demonstrated. The divider/combiner are applicable to various high- power , broadband radar, EW...Gysel Power Divider With Arbitrary Power Ratios and Filtering Responses Using Coupling Structure ,” IEEE Transactions on Microwave Theory and Tech., vol

  15. Bearing Estimation Using Double Frequency Reassignment for a Linear Passive Array

    Directory of Open Access Journals (Sweden)

    Czarnecki Krzysztof

    2017-09-01

    Full Text Available The paper demonstrates the use of frequency reassignment for bearing estimation. For this task, signals derived from a linear equispaced passive array are used. The presented method makes use of Fourier transformation based spatial spectrum estimation. It is further developed through the application of two-dimensional reassignment, which leads to obtaining highly concentrated energy distributions in the joint frequency-angle domain and sharp graphical imaging. The introduced method can be used for analysing, a priori, unknown signals of broadband, nonstationary, and/or multicomponent type. For such signals, the direction of arrival is obtained based upon the marginal energy distribution in the angle domain, through searching for arguments of its maxima. In the paper, bearing estimation of three popular types of sonar pulses, including linear and hyperbolic frequency modulated pulses, as well as no frequency modulation at all, is considered. The results of numerical experiments performed in the presence of additive white Gaussian noise are presented and compared to conventional digital sum-delay beamforming performed in the time domain. The root-mean-square error and the peak-to-average power ratio, also known as the crest factor, are introduced in order to estimate, respectively, the accuracy of the methods and the sharpness of the obtained energy distributions in the angle domain.

  16. Optical frequency upconversion technique for transmission of wireless MIMO-type signals over optical fiber.

    Science.gov (United States)

    Shaddad, R Q; Mohammad, A B; Al-Gailani, S A; Al-Hetar, A M

    2014-01-01

    The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio-over-fiber (ROF) technique. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as wireless multi-input multi-output (MIMO) signals feeding multiple antennas in the fiber wireless (FiWi) system. A novel optical frequency upconversion (OFU) technique is proposed to solve this problem. In this paper, the novel OFU approach is used to transmit three wireless MIMO signals over a 20 km standard single mode fiber (SMF). The OFU technique exploits one optical source to produce multiple wavelengths by delivering it to a LiNbO3 external optical modulator. The wireless MIMO signals are then modulated by LiNbO3 optical intensity modulators separately using the generated optical carriers from the OFU process. These modulators use the optical single-sideband with carrier (OSSB+C) modulation scheme to optimize the system performance against the fiber dispersion effect. Each wireless MIMO signal is with a 2.4 GHz or 5 GHz carrier frequency, 1 Gb/s data rate, and 16-quadrature amplitude modulation (QAM). The crosstalk between the wireless MIMO signals is highly suppressed, since each wireless MIMO signal is carried on a specific optical wavelength.

  17. Study on The Extended Range Weather Forecast of Low Frequency Signal Based on Period Analysis Method

    Science.gov (United States)

    Li, X.

    2016-12-01

    Although many studies have explored the MJO and its application for weather forecasting, low-frequency oscillation has been insufficiently studied for the extend range weather forecasting over middle and high latitudes. In China, low-frequency synoptic map is a useful tool for meteorological operation department to forecast extend range weather. It is therefore necessary to develop objective methods to serve the need for finding low-frequency signal, interpretation and application of this signal in the extend range weather forecasting. In this paper, method of Butterworth band pass filter was applied to get low-frequency height field at 500hPa from 1980 to 2014 by using NCEP/NCAR daily grid data. Then period analysis and optimal subset regression methods were used to process the low frequency data of 150 days before the first forecast day and extend the low frequency signal of 500hPa low-frequency high field to future 30 days in the global from June to August during 2011-2014. Finally, the results were test. The main results are as follows: (1) In general, the fitting effect of low frequency signals of 500hPa low-frequency height field by period analysis in the northern hemisphere was better than that in the southern hemisphere, and was better in the low latitudes than that in the high latitudes. The fitting accuracy gradually reduced with the increase of forecast time length, which tended to be stable during the late forecasting period. (2) The fitting effects over the 6 key regions in China showed that except filtering result over Xinjiang area in the first 10 days and 30 days, filtering results over the other 5 key regions throughout the whole period have passed reliability test with level more than 95%. (3) The center and scope of low and high low frequency systems can be fitted well by using the methods mentioned above, which is consist with the corresponding use of the low-frequency synoptic map for the prediction of the extended period. Application of the

  18. Real-time, high frequency QRS electrocardiograph with reduced amplitude zone detection

    Science.gov (United States)

    Schlegel, Todd T. (Inventor); DePalma, Jude L. (Inventor); Moradi, Saeed (Inventor)

    2009-01-01

    Real time cardiac electrical data are received from a patient, manipulated to determine various useful aspects of the ECG signal, and displayed in real time in a useful form on a computer screen or monitor. The monitor displays the high frequency data from the QRS complex in units of microvolts, juxtaposed with a display of conventional ECG data in units of millivolts or microvolts. The high frequency data are analyzed for their root mean square (RMS) voltage values and the discrete RMS values and related parameters are displayed in real time. The high frequency data from the QRS complex are analyzed with imbedded algorithms to determine the presence or absence of reduced amplitude zones, referred to herein as ''RAZs''. RAZs are displayed as ''go, no-go'' signals on the computer monitor. The RMS and related values of the high frequency components are displayed as time varying signals, and the presence or absence of RAZs may be similarly displayed over time.

  19. Use of high frequency analysis of acoustic emission signals to determine rolling element bearing condition

    International Nuclear Information System (INIS)

    Cockerill, A; Holford, K M; Pullin, R; Clarke, A; Bradshaw, T; Cole, P

    2015-01-01

    Acoustic Emission (AE) sensors were used to detect signals arising from a cylindrical roller bearing with artificial defects seeded onto the outer raceway. An SKF N204ECP roller bearing was placed between two double row spherical roller bearings, type SKF 22202E, and loaded between 0.29 and 1.79kN. Speed was constant at 5780rpm. High frequency analysis allowed insight into the condition of the bearings through the determination of an increase in the structural resonances of the system as the size of an artificial defect was increased. As higher loads were applied, frequencies around 100kHz were excited, indicating the release of AE possibly attributed to friction and the plastic deformation as peaks, induced through engraving of the raceway, were flattened and worn down. Sensitivity of AE to this level in bearings indicates the potential of the technique to detect the early stages of bearing failure during life tests. (paper)

  20. Radio over fiber transceiver employing phase modulation of an optical broadband source.

    Science.gov (United States)

    Grassi, Fulvio; Mora, José; Ortega, Beatriz; Capmany, José

    2010-10-11

    This paper proposes a low-cost RoF transceiver for multichannel SCM/WDM signal distribution suitable for future broadband access networks. The transceiver is based on the phase modulation of an optical broadband source centered at third transmission window. Prior to phase modulation the optical broadband source output signal is launched into a Mach-Zehnder interferometer structure, as key device enabling radio signals propagation over the optical link. Furthermore, an optical CWDM is employed to create a multichannel scenario by performing the spectral slicing of the modulated optical signal into a number of channels each one conveying the information from the central office to different base stations. The operation range is up to 20 GHz with a modulation bandwidth around of 500 MHz. Experimental results of the transmission of SCM QPSK and 64-QAM data through 20 Km of SMF exhibit good EVM results in the operative range determined by the phase-to-intensity conversion process. The proposed approach shows a great suitability for WDM networks based on RoF signal transport and also represents a cost-effective solution for passive optical networks.

  1. Using pulse oximetry to account for high and low frequency physiological artifacts in the BOLD signal.

    Science.gov (United States)

    Verstynen, Timothy D; Deshpande, Vibhas

    2011-04-15

    The BOLD signal not only reflects changes in local neural activity, but also exhibits variability from physiological processes like cardiac rhythms and breathing. We investigated how both of these physiological sources are reflected in the pulse oximetry (PO) signal, a direct measure of blood oxygenation, and how this information can be used to account for different types of noise in the BOLD response. Measures of heart rate, respiration and PO were simultaneously recorded while neurologically healthy participants performed an eye-movement task in a 3T MRI. PO exhibited power in frequencies that matched those found in the independently recorded cardiac and respiration signals. Using the phasic and aphasic properties of these signals as nuisance regressors, we found that the different frequency components of the PO signal could be used to identify different types of physiological artifacts in the BOLD response. A comparison of different physiological noise models found that a simple, down-sampled version of the PO signal improves the estimation of task-relevant statistics nearly as well as more established noise models that may run the risk of over-parameterization. These findings suggest that the PO signal captures multiple sources of physiological noise in the BOLD response and provides a simple and efficient way of modeling these noise sources in subsequent analysis. Copyright © 2011 Elsevier Inc. All rights reserved.

  2. [Design of High Frequency Signal Detecting Circuit of Human Body Impedance Used for Ultrashort Wave Diathermy Apparatus].

    Science.gov (United States)

    Fan, Xu; Wang, Yunguang; Cheng, Haiping; Chong, Xiaochen

    2016-02-01

    The present circuit was designed to apply to human tissue impedance tuning and matching device in ultra-short wave treatment equipment. In order to judge if the optimum status of circuit parameter between energy emitter circuit and accepter circuit is in well syntony, we designed a high frequency envelope detect circuit to coordinate with automatic adjust device of accepter circuit, which would achieve the function of human tissue impedance matching and tuning. Using the sampling coil to receive the signal of amplitude-modulated wave, we compared the voltage signal of envelope detect circuit with electric current of energy emitter circuit. The result of experimental study was that the signal, which was transformed by the envelope detect circuit, was stable and could be recognized by low speed Analog to Digital Converter (ADC) and was proportional to the electric current signal of energy emitter circuit. It could be concluded that the voltage, transformed by envelope detect circuit can mirror the real circuit state of syntony and realize the function of human tissue impedance collecting.

  3. Broadband filters for abatement of spontaneous emission in circuit quantum electrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Bronn, Nicholas T., E-mail: ntbronn@us.ibm.com; Hertzberg, Jared B.; Córcoles, Antonio D.; Gambetta, Jay M.; Chow, Jerry M. [IBM T.J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, New York 10598 (United States); Liu, Yanbing; Houck, Andrew A. [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544 (United States)

    2015-10-26

    The ability to perform fast, high-fidelity readout of quantum bits (qubits) is essential to the goal of building a quantum computer. However, coupling a fast measurement channel to a superconducting qubit typically also speeds up its relaxation via spontaneous emission. Here, we use impedance engineering to design a filter by which photons may easily leave the resonator at the cavity frequency but not at the qubit frequency. We implement this broadband filter in both an on-chip and off-chip configuration.

  4. Computational expressions for signals in frequency-modulation spectroscopy.

    Science.gov (United States)

    Di Rosa, Michael D; Reiten, M T

    2015-06-01

    General expressions for the signals in frequency-modulation spectroscopy (FMS) appear in the literature but are often reduced to simple analytical equations following the assumption of a weak modulation index. This is little help to the experimentalist who wants to predict signals for modulation depths of the order of unity or greater, where strong FMS signals reside. Here, we develop general formulas for FMS signals in the case of an absorber with a Voigt line shape and then link these expressions to an example and existing numerical code for the line shape. The resulting computational recipe is easy to implement and exercised here to show where the larger FMS signals are found over the coordinates of modulation index and modulation frequency. One can also estimate from provided curves the in-phase FMS signal over a wide range of modulation parameters at either the Lorentzian-broadening or Doppler-broadening limit, or anywhere in between by interpolation.

  5. Phase measurements of very-low-frequency signals from the magnetosphere

    International Nuclear Information System (INIS)

    Paschal, E.V.

    1988-01-01

    The usual methods of spectrum analysis applied to analog tape recordings of very low frequency (VLF) signals extract only magnitude information and ignore phase information. A digital signal-processing system using a recorded constant-frequency pilot tone was developed that can correct tape errors due to wow and flutter, and reconstruct the signal phases. Frequency shifts are corrected during analysis by interpolating between spectral points in the windowed Fourier transform, and the output phases of the synthesized filters are corrected for timing errors. Having signal-component phases as well as magnitudes doubles the available information. Whistler-mode signals from the VLF transmitter at Siple Station, Antarctica, were analyzed as received at Roberval, Quebec. The phase of a non-growing signal is found to give a less-noisy measure of duct motion than Doppler frequency shift, with improved time resolution. Correlations are seen between variations in the whistler-mode phase delay and the earth's magnetic field component D. They are interpreted as Pc 2 micropulsation transients, short compared to the length of the field line, which propagate from equator to ground as Alfven waves

  6. A Quantitative Analysis of Pulsed Signals Emitted by Wild Bottlenose Dolphins.

    Directory of Open Access Journals (Sweden)

    Ana Rita Luís

    Full Text Available Common bottlenose dolphins (Tursiops truncatus, produce a wide variety of vocal emissions for communication and echolocation, of which the pulsed repertoire has been the most difficult to categorize. Packets of high repetition, broadband pulses are still largely reported under a general designation of burst-pulses, and traditional attempts to classify these emissions rely mainly in their aural characteristics and in graphical aspects of spectrograms. Here, we present a quantitative analysis of pulsed signals emitted by wild bottlenose dolphins, in the Sado estuary, Portugal (2011-2014, and test the reliability of a traditional classification approach. Acoustic parameters (minimum frequency, maximum frequency, peak frequency, duration, repetition rate and inter-click-interval were extracted from 930 pulsed signals, previously categorized using a traditional approach. Discriminant function analysis revealed a high reliability of the traditional classification approach (93.5% of pulsed signals were consistently assigned to their aurally based categories. According to the discriminant function analysis (Wilk's Λ = 0.11, F3, 2.41 = 282.75, P < 0.001, repetition rate is the feature that best enables the discrimination of different pulsed signals (structure coefficient = 0.98. Classification using hierarchical cluster analysis led to a similar categorization pattern: two main signal types with distinct magnitudes of repetition rate were clustered into five groups. The pulsed signals, here described, present significant differences in their time-frequency features, especially repetition rate (P < 0.001, inter-click-interval (P < 0.001 and duration (P < 0.001. We document the occurrence of a distinct signal type-short burst-pulses, and highlight the existence of a diverse repertoire of pulsed vocalizations emitted in graded sequences. The use of quantitative analysis of pulsed signals is essential to improve classifications and to better assess the

  7. Time-frequency peak filtering for random noise attenuation of magnetic resonance sounding signal

    Science.gov (United States)

    Lin, Tingting; Zhang, Yang; Yi, Xiaofeng; Fan, Tiehu; Wan, Ling

    2018-05-01

    When measuring in a geomagnetic field, the method of magnetic resonance sounding (MRS) is often limited because of the notably low signal-to-noise ratio (SNR). Most current studies focus on discarding spiky noise and power-line harmonic noise cancellation. However, the effects of random noise should not be underestimated. The common method for random noise attenuation is stacking, but collecting multiple recordings merely to suppress random noise is time-consuming. Moreover, stacking is insufficient to suppress high-level random noise. Here, we propose the use of time-frequency peak filtering for random noise attenuation, which is performed after the traditional de-spiking and power-line harmonic removal method. By encoding the noisy signal with frequency modulation and estimating the instantaneous frequency using the peak of the time-frequency representation of the encoded signal, the desired MRS signal can be acquired from only one stack. The performance of the proposed method is tested on synthetic envelope signals and field data from different surveys. Good estimations of the signal parameters are obtained at different SNRs. Moreover, an attempt to use the proposed method to handle a single recording provides better results compared to 16 stacks. Our results suggest that the number of stacks can be appropriately reduced to shorten the measurement time and improve the measurement efficiency.

  8. The Implications of Encoder/Modulator/ Phased Array Designs for Future Broadband LEO Communications

    Science.gov (United States)

    Vanderaar, Mark; Jensen, Chris A.; Terry, John D.

    1997-01-01

    In this paper we summarize the effects of modulation and channel coding on the design of wide angle scan, broadband, phased army antennas. In the paper we perform several trade studies. First, we investigate the amplifier back-off requirement as a function of variability of modulation envelope. Specifically, we contrast constant and non-constant envelope modulations, as well as single and multiple carrier schemes. Additionally, we address the issues an(f concerns of using pulse shaping filters with the above modulation types. Second, we quantify the effects of beam steering on the quality of data, recovery using selected modulation techniques. In particular, we show that the frequency response of the array introduces intersymbol interference for broadband signals and that the mode of operation for the beam steering controller may introduce additional burst or random errors. Finally, we show that the encoder/modulator design must be performed in conjunction with the phased array antenna design.

  9. Broadband acoustic properties of a murine skull.

    Science.gov (United States)

    Estrada, Héctor; Rebling, Johannes; Turner, Jake; Razansky, Daniel

    2016-03-07

    It has been well recognized that the presence of a skull imposes harsh restrictions on the use of ultrasound and optoacoustic techniques in the study, treatment and modulation of the brain function. We propose a rigorous modeling and experimental methodology for estimating the insertion loss and the elastic constants of the skull over a wide range of frequencies and incidence angles. A point-source-like excitation of ultrawideband acoustic radiation was induced via the absorption of nanosecond duration laser pulses by a 20 μm diameter microsphere. The acoustic waves transmitted through the skull are recorded by a broadband, spherically focused ultrasound transducer. A coregistered pulse-echo ultrasound scan is subsequently performed to provide accurate skull geometry to be fed into an acoustic transmission model represented in an angular spectrum domain. The modeling predictions were validated by measurements taken from a glass cover-slip and ex vivo adult mouse skulls. The flexible semi-analytical formulation of the model allows for seamless extension to other transducer geometries and diverse experimental scenarios involving broadband acoustic transmission through locally flat solid structures. It is anticipated that accurate quantification and modeling of the skull transmission effects would ultimately allow for skull aberration correction in a broad variety of applications employing transcranial detection or transmission of high frequency ultrasound.

  10. High frequency measurement of P- and S-wave velocities on crystalline rock massif surface - methodology of measurement

    Science.gov (United States)

    Vilhelm, Jan; Slavík, Lubomír

    2014-05-01

    For the purpose of non-destructive monitoring of rock properties in the underground excavation it is possible to perform repeated high-accuracy P- and S-wave velocity measurements. This contribution deals with preliminary results gained during the preparation of micro-seismic long-term monitoring system. The field velocity measurements were made by pulse-transmission technique directly on the rock outcrop (granite) in Bedrichov gallery (northern Bohemia). The gallery at the experimental site was excavated using TBM (Tunnel Boring Machine) and it is used for drinking water supply, which is conveyed in a pipe. The stable measuring system and its automatic operation lead to the use of piezoceramic transducers both as a seismic source and as a receiver. The length of measuring base at gallery wall was from 0.5 to 3 meters. Different transducer coupling possibilities were tested namely with regard of repeatability of velocity determination. The arrangement of measuring system on the surface of the rock massif causes better sensitivity of S-transducers for P-wave measurement compared with the P-transducers. Similarly P-transducers were found more suitable for S-wave velocity determination then P-transducers. The frequency dependent attenuation of fresh rock massif results in limited frequency content of registered seismic signals. It was found that at the distance between the seismic source and receiver from 0.5 m the frequency components above 40 kHz are significantly attenuated. Therefore for the excitation of seismic wave 100 kHz transducers are most suitable. The limited frequency range should be also taken into account for the shape of electric impulse used for exciting of piezoceramic transducer. The spike pulse generates broad-band seismic signal, short in the time domain. However its energy after low-pass filtration in the rock is significantly lower than the energy of seismic signal generated by square wave pulse. Acknowledgments: This work was partially

  11. Broadband microwave frequency doubler based on left-handed nonlinear transmission lines

    International Nuclear Information System (INIS)

    Huang Jie; Gu Wenwen; Zhao Qian

    2017-01-01

    A bandwidth microwave second harmonic generator is successfully designed using composite right/left-handed nonlinear transmission lines (CRLH NLTLs) in a GaAs monolithic microwave integrated circuit (MMIC) technology. The structure parameters of CRLH NLTLs, e.g. host transmission line, rectangular spiral inductor, and nonlinear capacitor, have a great impact on the second harmonic performance enhancement in terms of second harmonic frequency, output power, and conversion efficiency. It has been experimentally demonstrated that the second harmonic frequency is determined by the anomalous dispersion of CRLH NLTLs and can be significantly improved by effectively adjusting these structure parameters. A good agreement between the measured and simulated second harmonic performances of Ka-band CRLH NLTLs frequency multipliers is successfully achieved, which further validates the design approach of frequency multipliers on CRLH NLTLs and indicates the potentials of CRLH NLTLs in terms of the generation of microwave and millimeter-wave signal source. (paper)

  12. Time-Frequency Analysis of Signals Generated by Rotating Machines

    Directory of Open Access Journals (Sweden)

    R. Zetik

    1999-06-01

    Full Text Available This contribution is devoted to the higher order time-frequency analyses of signals. Firstly, time-frequency representations of higher order (TFRHO are defined. Then L-Wigner distribution (LWD is given as a special case of TFRHO. Basic properties of LWD are illustrated based on the analysis of mono-component and multi-component synthetic signals and acoustical signals generated by rotating machine. The obtained results confirm usefulness of LWD application for the purpose of rotating machine condition monitoring.

  13. Broadband semiconductor optical amplifiers of the spectral range 750 – 1100 nm

    International Nuclear Information System (INIS)

    Andreeva, E V; Il'chenko, S N; Lobintsov, A A; Shramenko, M V; Ladugin, M A; Marmalyuk, A A; Yakubovich, S D

    2013-01-01

    A line of travelling-wave semiconductor optical amplifiers (SOAs) based on heterostructures used for production of broadband superluminescent diodes is developed. The pure small-signal gains of the developed SOA modules are about 25 dB, while the gain bandwidths at a level of –10 dB reach 50 – 100 nm. As a whole, the SOA modules cover the IR spectral range from 750 to 1100 nm. The SOAs demonstrate a high reliability at a single-mode fibre-coupled cw output power up to 50 mW. Examples of application of two of the developed SOA modules as active elements of broadband fast-tunable lasers are presented. (lasers)

  14. Broadband semiconductor optical amplifiers of the spectral range 750 – 1100 nm

    Energy Technology Data Exchange (ETDEWEB)

    Andreeva, E V; Il' chenko, S N; Lobintsov, A A; Shramenko, M V [Superlum Diodes Ltd., Moscow (Russian Federation); Ladugin, M A [' Sigm Plyus' Ltd, Moscow (Russian Federation); Marmalyuk, A A [Open Joint-Stock Company M.F. Stel' makh Polyus Research Institute, Moscow (Russian Federation); Yakubovich, S D [Moscow State Institute of Radio-Engineering, Electronics and Automation (Technical University), Moscow (Russian Federation)

    2013-11-30

    A line of travelling-wave semiconductor optical amplifiers (SOAs) based on heterostructures used for production of broadband superluminescent diodes is developed. The pure small-signal gains of the developed SOA modules are about 25 dB, while the gain bandwidths at a level of –10 dB reach 50 – 100 nm. As a whole, the SOA modules cover the IR spectral range from 750 to 1100 nm. The SOAs demonstrate a high reliability at a single-mode fibre-coupled cw output power up to 50 mW. Examples of application of two of the developed SOA modules as active elements of broadband fast-tunable lasers are presented. (lasers)

  15. Metallic stereostructured layer: An approach for broadband polarization state manipulation

    International Nuclear Information System (INIS)

    Xiong, Xiang; Hu, Yuan-Sheng; Jiang, Shang-Chi; Hu, Yu-Hui; Fan, Ren-Hao; Ma, Guo-Bin; Shu, Da-Jun; Peng, Ru-Wen; Wang, Mu

    2014-01-01

    In this letter, we report a full-metallic broadband wave plate assembled by standing metallic L-shaped stereostructures (LSSs). We show that with an array of LSSs, high polarization conversion ratio is achieved within a broad frequency band. Moreover, by rotating the orientation of the array of LSSs, the electric components of the reflection beam in two orthogonal directions and their phase difference can be independently tuned. In this way, all the polarization states on the Poincaré sphere can be realized. As examples, the functionalities of a quarter wave plate and a half wave plate are experimentally demonstrated with both reflection spectra and focal-plane-array imaging. Our designing provides a unique approach in realizing the broadband wave plate to manipulate the polarization state of light

  16. Frequency-dependent tACS modulation of BOLD signal during rhythmic visual stimulation.

    Science.gov (United States)

    Chai, Yuhui; Sheng, Jingwei; Bandettini, Peter A; Gao, Jia-Hong

    2018-05-01

    Transcranial alternating current stimulation (tACS) has emerged as a promising tool for modulating cortical oscillations. In previous electroencephalogram (EEG) studies, tACS has been found to modulate brain oscillatory activity in a frequency-specific manner. However, the spatial distribution and hemodynamic response for this modulation remains poorly understood. Functional magnetic resonance imaging (fMRI) has the advantage of measuring neuronal activity in regions not only below the tACS electrodes but also across the whole brain with high spatial resolution. Here, we measured fMRI signal while applying tACS to modulate rhythmic visual activity. During fMRI acquisition, tACS at different frequencies (4, 8, 16, and 32 Hz) was applied along with visual flicker stimulation at 8 and 16 Hz. We analyzed the blood-oxygen-level-dependent (BOLD) signal difference between tACS-ON vs tACS-OFF, and different frequency combinations (e.g., 4 Hz tACS, 8 Hz flicker vs 8 Hz tACS, 8 Hz flicker). We observed significant tACS modulation effects on BOLD responses when the tACS frequency matched the visual flicker frequency or the second harmonic frequency. The main effects were predominantly seen in regions that were activated by the visual task and targeted by the tACS current distribution. These findings bridge different scientific domains of tACS research and demonstrate that fMRI could localize the tACS effect on stimulus-induced brain rhythms, which could lead to a new approach for understanding the high-level cognitive process shaped by the ongoing oscillatory signal. © 2018 Wiley Periodicals, Inc.

  17. Scheme for efficient extraction of low-frequency signal beyond the quantum limit by frequency-shift detection.

    Science.gov (United States)

    Yang, R G; Zhang, J; Zhai, Z H; Zhai, S Q; Liu, K; Gao, J R

    2015-08-10

    Low-frequency (Hz~kHz) squeezing is very important in many schemes of quantum precision measurement. But it is more difficult than that at megahertz-frequency because of the introduction of laser low-frequency technical noise. In this paper, we propose a scheme to obtain a low-frequency signal beyond the quantum limit from the frequency comb in a non-degenerate frequency and degenerate polarization optical parametric amplifier (NOPA) operating below threshold with type I phase matching by frequency-shift detection. Low-frequency squeezing immune to laser technical noise is obtained by a detection system with a local beam of two-frequency intense laser. Furthermore, the low-frequency squeezing can be used for phase measurement in Mach-Zehnder interferometer, and the signal-to-noise ratio (SNR) can be enhanced greatly.

  18. High repetition rate tunable femtosecond pulses and broadband amplification from fiber laser pumped parametric amplifier.

    Science.gov (United States)

    Andersen, T V; Schmidt, O; Bruchmann, C; Limpert, J; Aguergaray, C; Cormier, E; Tünnermann, A

    2006-05-29

    We report on the generation of high energy femtosecond pulses at 1 MHz repetition rate from a fiber laser pumped optical parametric amplifier (OPA). Nonlinear bandwidth enhancement in fibers provides the intrinsically synchronized signal for the parametric amplifier. We demonstrate large tunability extending from 700 nm to 1500 nm of femtosecond pulses with pulse energies as high as 1.2 muJ when the OPA is seeded by a supercontinuum generated in a photonic crystal fiber. Broadband amplification over more than 85 nm is achieved at a fixed wavelength. Subsequent compression in a prism sequence resulted in 46 fs pulses. With an average power of 0.5 W these pulses have a peak-power above 10 MW. In particular, the average power and pulse energy scalability of both involved concepts, the fiber laser and the parametric amplifier, will enable easy up-scaling to higher powers.

  19. Dual-tone optical vector millimeter wave signal generated by frequency-nonupling the radio frequency 16-star quadrature-amplitude-modulation signal

    Science.gov (United States)

    Wu, Tonggen; Ma, Jianxin

    2017-12-01

    This paper proposes an original scheme to generate the photonic dual-tone optical millimeter wave (MMW) carrying the 16-star quadrature-amplitude-modulation (QAM) signal via an optical phase modulator (PM) and an interleaver with adaptive photonic frequency-nonupling without phase precoding. To enable the generated optical vector MMW signal to resist the power fading effect caused by the fiber chromatic dispersion, the modulated -5th- and +4th-order sidebands are selected from the output of the PM, which is driven by the precoding 16-star QAM signal. The modulation index of the PM is optimized to gain the maximum opto-electrical conversion efficiency. A radio over fiber link is built by simulation, and the simulated constellations and the bit error rate graph demonstrate that the frequency-nonupling 16-star QAM MMW signal has good transmission performance. The simulation results agree well with our theoretical results.

  20. Photoacoustic signal and noise analysis for Si thin plate: signal correction in frequency domain.

    Science.gov (United States)

    Markushev, D D; Rabasović, M D; Todorović, D M; Galović, S; Bialkowski, S E

    2015-03-01

    Methods for photoacoustic signal measurement, rectification, and analysis for 85 μm thin Si samples in the 20-20 000 Hz modulation frequency range are presented. Methods for frequency-dependent amplitude and phase signal rectification in the presence of coherent and incoherent noise as well as distortion due to microphone characteristics are presented. Signal correction is accomplished using inverse system response functions deduced by comparing real to ideal signals for a sample with well-known bulk parameters and dimensions. The system response is a piece-wise construction, each component being due to a particular effect of the measurement system. Heat transfer and elastic effects are modeled using standard Rosencweig-Gersho and elastic-bending theories. Thermal diffusion, thermoelastic, and plasmaelastic signal components are calculated and compared to measurements. The differences between theory and experiment are used to detect and correct signal distortion and to determine detector and sound-card characteristics. Corrected signal analysis is found to faithfully reflect known sample parameters.

  1. Highly Efficient Broadband Yellow Phosphor Based on Zero-Dimensional Tin Mixed-Halide Perovskite.

    Science.gov (United States)

    Zhou, Chenkun; Tian, Yu; Yuan, Zhao; Lin, Haoran; Chen, Banghao; Clark, Ronald; Dilbeck, Tristan; Zhou, Yan; Hurley, Joseph; Neu, Jennifer; Besara, Tiglet; Siegrist, Theo; Djurovich, Peter; Ma, Biwu

    2017-12-27

    Organic-inorganic hybrid metal halide perovskites have emerged as a highly promising class of light emitters, which can be used as phosphors for optically pumped white light-emitting diodes (WLEDs). By controlling the structural dimensionality, metal halide perovskites can exhibit tunable narrow and broadband emissions from the free-exciton and self-trapped excited states, respectively. Here, we report a highly efficient broadband yellow light emitter based on zero-dimensional tin mixed-halide perovskite (C 4 N 2 H 14 Br) 4 SnBr x I 6-x (x = 3). This rare-earth-free ionically bonded crystalline material possesses a perfect host-dopant structure, in which the light-emitting metal halide species (SnBr x I 6-x 4- , x = 3) are completely isolated from each other and embedded in the wide band gap organic matrix composed of C 4 N 2 H 14 Br - . The strongly Stokes-shifted broadband yellow emission that peaked at 582 nm from this phosphor, which is a result of excited state structural reorganization, has an extremely large full width at half-maximum of 126 nm and a high photoluminescence quantum efficiency of ∼85% at room temperature. UV-pumped WLEDs fabricated using this yellow emitter together with a commercial europium-doped barium magnesium aluminate blue phosphor (BaMgAl 10 O 17 :Eu 2+ ) can exhibit high color rendering indexes of up to 85.

  2. DC response of dust to low frequency AC signals

    Science.gov (United States)

    McKinlay, Michael; Konopka, Uwe; Thomas, Edward

    2017-10-01

    Macroscopic changes in the shape and equilibrium position of clouds of charged microparticles suspended in a plasma have been observed in response to low frequency AC signals. In these experiments, dusty plasmas consisting of 2-micron diameter silica microspheres suspended between an anode and cathode in an argon, DC glow discharge plasma are produced in a grounded, 6-way cross vacuum chamber. An AC signal, produced by a function generator and amplified by a bipolar op-amp, is superimposed onto the potential from the cathode. The frequencies of the applied AC signals, ranging from tens to hundreds of kHz, are comparable to the ion-neutral collision frequency; well below the ion/electron plasma frequencies, but also considerably higher than the dust plasma frequency. This presentation will detail the experimental setup, present documentation and categorization of observations of the dust response, and present an initial model of the response. This work is supported by funding from the US Dept. of Energy, Grant Number DE-SC0016330, and by the National Science Foundation, Grant Number PHY-1613087.

  3. A nonuniform-polarization high-energy ultra-broadband laser with a long erbium-doped fiber

    International Nuclear Information System (INIS)

    Mao, Dong

    2013-01-01

    We have experimentally investigated nonuniformly polarized broadband high-energy pulses delivered from a mode-locked laser with an ultra-long erbium-doped fiber (EDF). The pulses exhibit a broadband spectrum of ∼73 nm and can avoid optical wave breaking at high-pump regimes. The polarization states of the pulses evolve from uniform to nonuniform at each round trip in the oscillator, which is distinct from other pulses. Remarkably, the output pulses broaden in anomalous- or normal-dispersion regimes while they can be shortened with an EDF amplifier external to the cavity. Our results suggest that the long EDF results in a nonuniform-polarization state and plays a decisive role in the formation of high-energy pulses. (paper)

  4. Estimation of High-Frequency Earth-Space Radio Wave Signals via Ground-Based Polarimetric Radar Observations

    Science.gov (United States)

    Bolen, Steve; Chandrasekar, V.

    2002-01-01

    Expanding human presence in space, and enabling the commercialization of this frontier, is part of the strategic goals for NASA's Human Exploration and Development of Space (HEDS) enterprise. Future near-Earth and planetary missions will support the use of high-frequency Earth-space communication systems. Additionally, increased commercial demand on low-frequency Earth-space links in the S- and C-band spectra have led to increased interest in the use of higher frequencies in regions like Ku and Ka-band. Attenuation of high-frequency signals, due to a precipitating medium, can be quite severe and can cause considerable disruptions in a communications link that traverses such a medium. Previously, ground radar measurements were made along the Earth-space path and compared to satellite beacon data that was transmitted to a ground station. In this paper, quantitative estimation of the attenuation along the propagation path is made via inter-comparisons of radar data taken from the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and ground-based polarimetric radar observations. Theoretical relationships between the expected specific attenuation (k) of spaceborne measurements with ground-based measurements of reflectivity (Zh) and differential propagation phase shift (Kdp) are developed for various hydrometeors that could be present along the propagation path, which are used to estimate the two-way path-integrated attenuation (PIA) on the PR return echo. Resolution volume matching and alignment of the radar systems is performed, and a direct comparison of PR return echo with ground radar attenuation estimates is made directly on a beam-by-beam basis. The technique is validated using data collected from the TExas and Florida UNderflights (TEFLUN-B) experiment and the TRMM large Biosphere-Atmosphere experiment in Amazonia (LBA) campaign. Attenuation estimation derived from this method can be used for strategiC planning of communication systems for

  5. High frequency source localization in a shallow ocean sound channel using frequency difference matched field processing.

    Science.gov (United States)

    Worthmann, Brian M; Song, H C; Dowling, David R

    2015-12-01

    Matched field processing (MFP) is an established technique for source localization in known multipath acoustic environments. Unfortunately, in many situations, particularly those involving high frequency signals, imperfect knowledge of the actual propagation environment prevents accurate propagation modeling and source localization via MFP fails. For beamforming applications, this actual-to-model mismatch problem was mitigated through a frequency downshift, made possible by a nonlinear array-signal-processing technique called frequency difference beamforming [Abadi, Song, and Dowling (2012). J. Acoust. Soc. Am. 132, 3018-3029]. Here, this technique is extended to conventional (Bartlett) MFP using simulations and measurements from the 2011 Kauai Acoustic Communications MURI experiment (KAM11) to produce ambiguity surfaces at frequencies well below the signal bandwidth where the detrimental effects of mismatch are reduced. Both the simulation and experimental results suggest that frequency difference MFP can be more robust against environmental mismatch than conventional MFP. In particular, signals of frequency 11.2 kHz-32.8 kHz were broadcast 3 km through a 106-m-deep shallow ocean sound channel to a sparse 16-element vertical receiving array. Frequency difference MFP unambiguously localized the source in several experimental data sets with average peak-to-side-lobe ratio of 0.9 dB, average absolute-value range error of 170 m, and average absolute-value depth error of 10 m.

  6. A comprehensive inversion approach for feedforward compensation of piezoactuator system at high frequency

    Science.gov (United States)

    Tian, Lizhi; Xiong, Zhenhua; Wu, Jianhua; Ding, Han

    2016-09-01

    Motion control of the piezoactuator system over broadband frequencies is limited due to its inherent hysteresis and system dynamics. One of the suggested ways is to use feedforward controller to linearize the input-output relationship of the piezoactuator system. Although there have been many feedforward approaches, it is still a challenge to develop feedforward controller for the piezoactuator system at high frequency. Hence, this paper presents a comprehensive inversion approach in consideration of the coupling of hysteresis and dynamics. In this work, the influence of dynamics compensation on the input-output relationship of the piezoactuator system is investigated first. With system dynamics compensation, the input-output relationship of the piezoactuator system will be further represented as rate-dependent nonlinearity due to the inevitable dynamics compensation error, especially at high frequency. Base on this result, the feedforward controller composed by a cascade of linear dynamics inversion and rate-dependent nonlinearity inversion is developed. Then, the system identification of the comprehensive inversion approach is proposed. Finally, experimental results show that the proposed approach can improve the performance on tracking of both periodic and non-periodic trajectories at medium and high frequency compared with the conventional feedforward approaches.

  7. Frequency hopping signal detection based on wavelet decomposition and Hilbert-Huang transform

    Science.gov (United States)

    Zheng, Yang; Chen, Xihao; Zhu, Rui

    2017-07-01

    Frequency hopping (FH) signal is widely adopted by military communications as a kind of low probability interception signal. Therefore, it is very important to research the FH signal detection algorithm. The existing detection algorithm of FH signals based on the time-frequency analysis cannot satisfy the time and frequency resolution requirement at the same time due to the influence of window function. In order to solve this problem, an algorithm based on wavelet decomposition and Hilbert-Huang transform (HHT) was proposed. The proposed algorithm removes the noise of the received signals by wavelet decomposition and detects the FH signals by Hilbert-Huang transform. Simulation results show the proposed algorithm takes into account both the time resolution and the frequency resolution. Correspondingly, the accuracy of FH signals detection can be improved.

  8. Synthesis of multi-wavelength temporal phase-shifting algorithms optimized for high signal-to-noise ratio and high detuning robustness using the frequency transfer function.

    Science.gov (United States)

    Servin, Manuel; Padilla, Moises; Garnica, Guillermo

    2016-05-02

    Synthesis of single-wavelength temporal phase-shifting algorithms (PSA) for interferometry is well-known and firmly based on the frequency transfer function (FTF) paradigm. Here we extend the single-wavelength FTF-theory to dual and multi-wavelength PSA-synthesis when several simultaneous laser-colors are present. The FTF-based synthesis for dual-wavelength (DW) PSA is optimized for high signal-to-noise ratio and minimum number of temporal phase-shifted interferograms. The DW-PSA synthesis herein presented may be used for interferometric contouring of discontinuous industrial objects. Also DW-PSA may be useful for DW shop-testing of deep free-form aspheres. As shown here, using the FTF-based synthesis one may easily find explicit DW-PSA formulae optimized for high signal-to-noise and high detuning robustness. To this date, no general synthesis and analysis for temporal DW-PSAs has been given; only ad hoc DW-PSAs formulas have been reported. Consequently, no explicit formulae for their spectra, their signal-to-noise, their detuning and harmonic robustness has been given. Here for the first time a fully general procedure for designing DW-PSAs (or triple-wavelengths PSAs) with desire spectrum, signal-to-noise ratio and detuning robustness is given. We finally generalize DW-PSA to higher number of wavelength temporal PSAs.

  9. Time domain acoustic contrast control implementation of sound zones for low-frequency input signals

    DEFF Research Database (Denmark)

    Schellekens, Daan H. M.; Møller, Martin Bo; Olsen, Martin

    2016-01-01

    Sound zones are two or more regions within a listening space where listeners are provided with personal audio. Acoustic contrast control (ACC) is a sound zoning method that maximizes the average squared sound pressure in one zone constrained to constant pressure in other zones. State......-of-the-art time domain broadband acoustic contrast control (BACC) methods are designed for anechoic environments. These methods are not able to realize a flat frequency response in a limited frequency range within a reverberant environment. Sound field control in a limited frequency range is a requirement...... to accommodate the effective working range of the loudspeakers. In this paper, a new BACC method is proposed which results in an implementation realizing a flat frequency response in the target zone. This method is applied in a bandlimited low-frequency scenario where the loudspeaker layout surrounds two...

  10. Direct and quantitative broadband absorptance spectroscopy with multilayer cantilever probes

    Science.gov (United States)

    Hsu, Wei-Chun; Tong, Jonathan Kien-Kwok; Liao, Bolin; Chen, Gang

    2015-04-21

    A system for measuring the absorption spectrum of a sample is provided that includes a broadband light source that produces broadband light defined within a range of an absorptance spectrum. An interferometer modulates the intensity of the broadband light source for a range of modulation frequencies. A bi-layer cantilever probe arm is thermally connected to a sample arm having at most two layers of materials. The broadband light modulated by the interferometer is directed towards the sample and absorbed by the sample and converted into heat, which causes a temperature rise and bending of the bi-layer cantilever probe arm. A detector mechanism measures and records the deflection of the probe arm so as to obtain the absorptance spectrum of the sample.

  11. Interpretation of the instantaneous frequency of phonocardiogram signals

    Science.gov (United States)

    Rey, Alexis B.

    2005-06-01

    Short-Time Fourier transforms, Wigner-Ville distribution, and Wavelet Transforms have been commonly used when dealing with non-stationary signals, and they have been known as time-frequency distributions. Also, it is commonly intended to investigate the behaviour of phonocardiogram signals as a means of prediction some oh the pathologies of the human hart. For this, this paper aims to analyze the relationship between the instantaneous frequency of a PCG signal and the so-mentioned time-frequency distributions; three algorithms using Matlab functions have been developed: the first one, the estimation of the IF using the normalized linear moment, the second one, the estimation of the IF using the periodic first moment, and the third one, the computing of the WVD. Meanwhile, the computing of the STFT spectrogram is carried out with a Matlab function. Several simulations of the spectrogram for a set of PCG signals and the estimation of the IF are shown, and its relationship is validated through correlation. Finally, the second algorithm is a better choice because the estimation is not biased, whereas the WVD is very computing-demanding and offers no benefit since the estimation of the IF by using this TFD has an equivalent result when using the derivative of the phase of the analytic signal, which is also less computing-demanding.

  12. High-Order Frequency-Locked Loops

    DEFF Research Database (Denmark)

    Golestan, Saeed; Guerrero, Josep M.; Quintero, Juan Carlos Vasquez

    2017-01-01

    In very recent years, some attempts for designing high-order frequency-locked loops (FLLs) have been made. Nevertheless, the advantages and disadvantages of these structures, particularly in comparison with a standard FLL and high-order phase-locked loops (PLLs), are rather unclear. This lack...... study, and its small-signal modeling, stability analysis, and parameter tuning are presented. Finally, to gain insight about advantages and disadvantages of high-order FLLs, a theoretical and experimental performance comparison between the designed second-order FLL and a standard FLL (first-order FLL...

  13. Broad-band beam buncher

    International Nuclear Information System (INIS)

    Goldberg, D.A.; Flood, W.S.; Arthur, A.A.; Voelker, F.

    1986-01-01

    This patent describes a broad-band beam buncher. This beam buncher consists of: a housing adapted to be eacuated, an electron gun in the housing for producing a beam of electrons, buncher means in the housing forming a buncher cavity which has an entrance opening for receiving the electron beam and an exit opening through which the electron beam passes out of the buncher cavity, a drift tube electrode in the buncher cavity and disposed between the entrance opening and the exit opening with first and second gaps between the drift tube electrode and the entrance and exit openings, the drift tube electrode which has a first drift space through which the electron beam passes in traveling between the entrance and exit openings, modulating means for supplying an ultrahigh frequeny modulating signal to the drift tube electrode for producing velocity modulation of the electrons in the electron beam as the electrons pass through the buncher cavity and the drift tube electrode between the entrance opening and the exit opening, drift space means in the housing forming a second drift space for receiving the velocity modulated electron beam from the exit opening, the velocity modulated electron beam being bunched as it passes along the second drift space, the drift space means has a discharge opening through which the electron beam is discharged from the second drift space after being bunched therein, the modulating means containing a signal source for producing an ultrahigh frequency signal, a transmission line connected between the signal source and the drift tube electrode, and terminating means connected to the drift tube electrode for terminating the transmission line in approximately its characteristic impedance to afford a broad response band with minimum 6 variations therein

  14. Low velocity target detection based on time-frequency image for high frequency ground wave radar

    Institute of Scientific and Technical Information of China (English)

    YAN Songhua; WU Shicai; WEN Biyang

    2007-01-01

    The Doppler spectral broadening resulted from non-stationary movement of target and radio-frequency interference will decrease the veracity of target detection by high frequency ground wave(HEGW)radar.By displaying the change of signal energy on two dimensional time-frequency images based on time-frequency analysis,a new mathematical morphology method to distinguish target from nonlinear time-frequency curves is presented.The analyzed results from the measured data verify that with this new method the target can be detected correctly from wide Doppler spectrum.

  15. Broadband radiometric LED measurements

    Science.gov (United States)

    Eppeldauer, G. P.; Cooksey, C. C.; Yoon, H. W.; Hanssen, L. M.; Podobedov, V. B.; Vest, R. E.; Arp, U.; Miller, C. C.

    2016-09-01

    At present, broadband radiometric LED measurements with uniform and low-uncertainty results are not available. Currently, either complicated and expensive spectral radiometric measurements or broadband photometric LED measurements are used. The broadband photometric measurements are based on the CIE standardized V(λ) function, which cannot be used in the UV range and leads to large errors when blue or red LEDs are measured in its wings, where the realization is always poor. Reference irradiance meters with spectrally constant response and high-intensity LED irradiance sources were developed here to implement the previously suggested broadband radiometric LED measurement procedure [1, 2]. Using a detector with spectrally constant response, the broadband radiometric quantities of any LEDs or LED groups can be simply measured with low uncertainty without using any source standard. The spectral flatness of filtered-Si detectors and low-noise pyroelectric radiometers are compared. Examples are given for integrated irradiance measurement of UV and blue LED sources using the here introduced reference (standard) pyroelectric irradiance meters. For validation, the broadband measured integrated irradiance of several LED-365 sources were compared with the spectrally determined integrated irradiance derived from an FEL spectral irradiance lamp-standard. Integrated responsivity transfer from the reference irradiance meter to transfer standard and field UV irradiance meters is discussed.

  16. Signal existence verification (SEV) for GPS low received power signal detection using the time-frequency approach.

    Science.gov (United States)

    Jan, Shau-Shiun; Sun, Chih-Cheng

    2010-01-01

    The detection of low received power of global positioning system (GPS) signals in the signal acquisition process is an important issue for GPS applications. Improving the miss-detection problem of low received power signal is crucial, especially for urban or indoor environments. This paper proposes a signal existence verification (SEV) process to detect and subsequently verify low received power GPS signals. The SEV process is based on the time-frequency representation of GPS signal, and it can capture the characteristic of GPS signal in the time-frequency plane to enhance the GPS signal acquisition performance. Several simulations and experiments are conducted to show the effectiveness of the proposed method for low received power signal detection. The contribution of this work is that the SEV process is an additional scheme to assist the GPS signal acquisition process in low received power signal detection, without changing the original signal acquisition or tracking algorithms.

  17. Ultra-broadband and high-efficiency polarization conversion metasurface with multiple plasmon resonance modes

    Science.gov (United States)

    Dong, Guo-Xiang; Shi, Hong-Yu; Xia, Song; Li, Wei; Zhang, An-Xue; Xu, Zhuo; Wei, Xiao-Yong

    2016-08-01

    In this paper, we present a novel metasurface design that achieves a high-efficiency ultra-broadband cross polarization conversion. The metasurface is composed of an array of unit resonators, each of which combines an H-shaped structure and two rectangular metallic patches. Different plasmon resonance modes are excited in unit resonators and allow the polarization states to be manipulated. The bandwidth of the cross polarization converter is 82% of the central frequency, covering the range from 15.7 GHz to 37.5 GHz. The conversion efficiency of the innovative new design is higher than 90%. At 14.43 GHz and 40.95 GHz, the linearly polarized incident wave is converted into a circularly polarized wave. Project supported by the National Natural Science Foundation of China (Grant Nos. 61471292, 61331005, 61471388, 51277012, 41404095, and 61501365), the 111 Project, China (Grant No. B14040), the National Basic Research Program of China (Grant No. 2015CB654602), and the China Postdoctoral Science Foundation ( Grant No. 2015M580849).

  18. Incorporation of Tin on copper clad laminate to increase the interface adhesion for signal loss reduction of high-frequency PCB lamination

    Science.gov (United States)

    Wang, Chong; Wen, Na; Zhou, Guoyun; Wang, Shouxu; He, Wei; Su, Xinhong; Hu, Yongsuan

    2017-11-01

    A novel method of improving the adhesion between copper and prepreg in high frequency PCB was proposed and studied in this work. This process which aimed to decrease the IEP (isoelectric point) of the copper to obtain higher adhesion, was achieved by depositing a thin tin layer with lower IEP on copper. It was characterized by scanning electron microscopy (SEM), 3D microscope, peel strength test, X-Ray thickness test, grazing incidence X-ray diffraction (GXRD), X-ray photoelectron spectroscopy (XPS), Agilent vector network analyzer (VNA), which confirmed its excellent adhesion performance and outstanding electrical properties in high-frequency signal transmission compared with traditional brown oxide method. Moreover, the mechanism of achieving high adhesion for this method was also investigated.

  19. Broadband plasmonic silver nanoflowers for high-performance random lasing covering visible region

    Directory of Open Access Journals (Sweden)

    Chang Qing

    2017-05-01

    Full Text Available Multicolor random lasing has broad potential applications in the fields of imaging, sensing, and optoelectronics. Here, silver nanoflowers (Ag NF with abundant nanogaps are fabricated by a rapid one-step solution-phase synthesis method and are first proposed as effective broadband plasmonic scatterers to achieve different color random lasing. With abundant nanogaps and spiky tips near the surface and the interparticle coupling effect, Ag NFs greatly enhance the local electromagnetic field and induce broadband plasmonic scattering spectra over the whole visible range. The extremely low working threshold and the high-quality factor for Ag NF-based random lasers are thus demonstrated as 0.24 MW cm−2 and 11,851, respectively. Further, coherent colorful random lasing covering the visible range is realized using the dye molecules oxazine (red, Coumarin 440 (blue, and Coumarin 153 (green, showing high-quality factor of more than 10,000. All these features show that Ag NF are highly efficient scatterers for high-performance coherent random lasing and colorful random lasers.

  20. Development of earthquake early warning system using real time signal of broadband seismogram

    International Nuclear Information System (INIS)

    Gunawan, Hendar; Puspito, Nanang T.; Ibrahim, Gunawan; Harjadi, Prih

    2012-01-01

    Earthquake pose serious threat of live and properties for urban area near subduction zone offshore and active fault on land. Jakarta and Bandung is an example of big city that no system of Earthquake early warning (EEW) event very high urbanization, and has many important infra structure in the area. The capital city is potentially high risk ground shaking. EEW can be usefull tool for reducing earthquake hazard, if spatial relation between cities and earthquake source is favorable for such warning and their citizens are properly trained to response early warning message. An EEW and rapid response system can provide the critical information needed to minimized lost of live and property and direct rescue. Earthquake ground shaking with magnitude M>6.0 from zone of Megathrust, southern of West Java should potentially damage in the area of west java especially Bandung and Jakarta City. This research development of EEW parameter such as amplitude displacement (Pd), rapid magnitude determination (M) and Peak ground Velocity (PGV). We explore the practical approach to EEW with the use of Broadband seismogram signal. Time effective EEW which epicenter from megathrust zone has potential to provide EEW in the area of west java such as Jakarta first ground shaking more or less 60 second later and strong shaking 118 second after EEW Alarm on CISI Station. EEW notification at potentially damage in the area of west java can be predicted from the characteristic of Pd > 0.5 cm, M> 6 and PGV > 10 cm/sec. GIS as a tool for presentation of hazard mapping in the affected area.

  1. Measurement uncertainty in broadband radiofrequency radiation level measurements

    Directory of Open Access Journals (Sweden)

    Vulević Branislav D.

    2014-01-01

    Full Text Available For the evaluation of measurement uncertainty in the measurement of broadband radio frequency radiation, in this paper we propose a new approach based on the experience of the authors of the paper with measurements of radiofrequency electric field levels conducted in residential areas of Belgrade and over 35 municipalities in Serbia. The main objective of the paper is to present practical solutions in the evaluation of broadband measurement uncertainty for the in-situ RF radiation levels. [Projekat Ministarstva nauke Republike Srbije, br. III43009

  2. Characteristics of a Broadband Dye Laser Using Pyrromethene and Rhodamine Dyes

    Science.gov (United States)

    Tedder, Sarah A.; Danehy, Paul M.; Wheeler, Jeffrey L.

    2011-01-01

    A broadband dye laser pumped by a frequency-doubled Nd:YAG laser with a full-width half-maximum (FWHM) from 592 to 610 nm was created for the use in a dual-pump broadband CARS system called WIDECARS. The desired broadband dye laser was generated with a mixture of Pyrromethene dyes as an oscillator gain medium and a spectral selective optic in the oscillator cavity. A mixture of Rhodamine dyes were used in the amplifier dye cell. To create this laser a study was performed to characterize the spectral behavior of broadband dye lasers created with Rhodamine dyes 590, 610, and 640, Pyrromethene dyes 597 and 650 as well as mixture of these dyes.

  3. The Time-Frequency Signatures of Advanced Seismic Signals Generated by Debris Flows

    Science.gov (United States)

    Chu, C. R.; Huang, C. J.; Lin, C. R.; Wang, C. C.; Kuo, B. Y.; Yin, H. Y.

    2014-12-01

    The seismic monitoring is expected to reveal the process of debris flow from the initial area to alluvial fan, because other field monitoring techniques, such as the video camera and the ultrasonic sensor, are limited by detection range. For this reason, seismic approaches have been used as the detection system of debris flows over the past few decades. The analysis of the signatures of the seismic signals in time and frequency domain can be used to identify the different phases of debris flow. This study dedicates to investigate the different stages of seismic signals due to debris flow, including the advanced signal, the main front, and the decaying tail. Moreover, the characteristics of the advanced signals forward to the approach of main front were discussed for the warning purpose. This study presents a permanent system, composed by two seismometers, deployed along the bank of Ai-Yu-Zi Creek in Nantou County, which is one of the active streams with debris flow in Taiwan. The three axes seismometer with frequency response of 7 sec - 200 Hz was developed by the Institute of Earth Sciences (IES), Academia Sinica for the purpose to detect debris flow. The original idea of replacing the geophone system with the seismometer technique was for catching the advanced signals propagating from the upper reach of the stream before debris flow arrival because of the high sensitivity. Besides, the low frequency seismic waves could be also early detected because of the low attenuation. However, for avoiding other unnecessary ambient vibrations, the sensitivity of seismometer should be lower than the general seismometer for detecting teleseism. Three debris flows with different mean velocities were detected in 2013 and 2014. The typical triangular shape was obviously demonstrated in time series data and the spectrograms of the seismic signals from three events. The frequency analysis showed that enormous debris flow bearing huge boulders would induce low frequency seismic

  4. Estimation of chromatic errors from broadband images for high contrast imaging

    Science.gov (United States)

    Sirbu, Dan; Belikov, Ruslan

    2015-09-01

    Usage of an internal coronagraph with an adaptive optical system for wavefront correction for direct imaging of exoplanets is currently being considered for many mission concepts, including as an instrument addition to the WFIRST-AFTA mission to follow the James Web Space Telescope. The main technical challenge associated with direct imaging of exoplanets with an internal coronagraph is to effectively control both the diffraction and scattered light from the star so that the dim planetary companion can be seen. For the deformable mirror (DM) to recover a dark hole region with sufficiently high contrast in the image plane, wavefront errors are usually estimated using probes on the DM. To date, most broadband lab demonstrations use narrowband filters to estimate the chromaticity of the wavefront error, but this reduces the photon flux per filter and requires a filter system. Here, we propose a method to estimate the chromaticity of wavefront errors using only a broadband image. This is achieved by using special DM probes that have sufficient chromatic diversity. As a case example, we simulate the retrieval of the spectrum of the central wavelength from broadband images for a simple shaped- pupil coronagraph with a conjugate DM and compute the resulting estimation error.

  5. A broadband metamaterial absorber based on multi-layer graphene in the terahertz region

    Science.gov (United States)

    Fu, Pan; Liu, Fei; Ren, Guang Jun; Su, Fei; Li, Dong; Yao, Jian Quan

    2018-06-01

    A broadband metamaterial absorber, composed of the periodic graphene pattern on SiO2 dielectric with the double layer graphene films inserted in it and all of them backed by metal plan, is proposed and investigated. The simulation results reveal that the wide absorption band can be flexibly tuned between the low-frequency band and the high-frequency band by adjusting graphene's Fermi level. The absorption can achieve 90% in 5.50-7.10 THz, with Fermi level of graphene is 0.3 eV, while in 6.98-9.10 THz with Fermi level 0.6 eV. Furthermore, the proposed structure can be switched from reflection (>81%) to absorption (>90%) over the whole operation band, when the Fermi level of graphene varies from 0 to 0.6 eV. Besides, the proposed absorber is insensitive to the polarization and can work over a wide range of incident angle. Compared with the previous broadband absorber, our graphene based wideband terahertz absorber can enable a wide application of high performance terahertz devices, including sensors, imaging devices and electro-optic switches.

  6. Interaural time sensitivity of high-frequency neurons in the inferior colliculus.

    Science.gov (United States)

    Yin, T C; Kuwada, S; Sujaku, Y

    1984-11-01

    Recent psychoacoustic experiments have shown that interaural time differences provide adequate cues for lateralizing high-frequency sounds, provided the stimuli are complex and not pure tones. We present here physiological evidence in support of these findings. Neurons of high best frequency in the cat inferior colliculus respond to interaural phase differences of amplitude modulated waveforms, and this response depends upon preservation of phase information of the modulating signal. Interaural phase differences were introduced in two ways: by interaural delays of the entire waveform and by binaural beats in which there was an interaural frequency difference in the modulating waveform. Results obtained with these two methods are similar. Our results show that high-frequency cells can respond to interaural time differences of amplitude modulated signals and that they do so by a sensitivity to interaural phase differences of the modulating waveform.

  7. The Influence of High-Frequency Envelope Information on Low-Frequency Vowel Identification in Noise.

    Directory of Open Access Journals (Sweden)

    Wiebke Schubotz

    Full Text Available Vowel identification in noise using consonant-vowel-consonant (CVC logatomes was used to investigate a possible interplay of speech information from different frequency regions. It was hypothesized that the periodicity conveyed by the temporal envelope of a high frequency stimulus can enhance the use of the information carried by auditory channels in the low-frequency region that share the same periodicity. It was further hypothesized that this acts as a strobe-like mechanism and would increase the signal-to-noise ratio for the voiced parts of the CVCs. In a first experiment, different high-frequency cues were provided to test this hypothesis, whereas a second experiment examined more closely the role of amplitude modulations and intact phase information within the high-frequency region (4-8 kHz. CVCs were either natural or vocoded speech (both limited to a low-pass cutoff-frequency of 2.5 kHz and were presented in stationary 3-kHz low-pass filtered masking noise. The experimental results did not support the hypothesized use of periodicity information for aiding low-frequency perception.

  8. The Influence of High-Frequency Envelope Information on Low-Frequency Vowel Identification in Noise.

    Science.gov (United States)

    Schubotz, Wiebke; Brand, Thomas; Kollmeier, Birger; Ewert, Stephan D

    2016-01-01

    Vowel identification in noise using consonant-vowel-consonant (CVC) logatomes was used to investigate a possible interplay of speech information from different frequency regions. It was hypothesized that the periodicity conveyed by the temporal envelope of a high frequency stimulus can enhance the use of the information carried by auditory channels in the low-frequency region that share the same periodicity. It was further hypothesized that this acts as a strobe-like mechanism and would increase the signal-to-noise ratio for the voiced parts of the CVCs. In a first experiment, different high-frequency cues were provided to test this hypothesis, whereas a second experiment examined more closely the role of amplitude modulations and intact phase information within the high-frequency region (4-8 kHz). CVCs were either natural or vocoded speech (both limited to a low-pass cutoff-frequency of 2.5 kHz) and were presented in stationary 3-kHz low-pass filtered masking noise. The experimental results did not support the hypothesized use of periodicity information for aiding low-frequency perception.

  9. High frequency P(VDF-TrFE) copolymer broadband annular array ultrasound transducers using high density flexible circuit interconnect

    Science.gov (United States)

    Gottlieb, Emanuel J.; Cannata, Jonathan M.; Hu, Chang Hong; Shung, K. K.

    2005-04-01

    A kerfless eight element high frequency ultrasound annular array transducer using 9 μm P(VDF-TrFE) bonded to a high density flexible interconnect was fabricated. The flexible circuit composed of Kapton polyimide film with gold electrode pattern of equal area annuli apertures on the top side of a 50 μm thick Kapton polyimide film. Each element had several 30 μm diameter electroplated vias that connected to electrode traces on the bottom side of the Kapton polyimide film. There was a 30 μm spacing between elements. The total aperture of the array was 3.12 mm. The transducer's performance has been modeled by implementing the Redwood version of the Mason model into PSpice and using the Krimholtz, Leedom and Matthaei (KLM) model utilized in the commercial software PiezoCAD. The transducer"s performance was evaluated by measuring the electrical impedance with a HP 4194 impedance analyzer, pulse echo response using a Panametrics 5900 pulser/receiver and crosstalk measurement for each element in the array. The measured electrical impedance for each element was 540 Ω and -84° phase. In order to improve device sensitivity an inductor was attached in series with each element to reduce the insertion loss to 33 dB. The measured average center frequency and bandwidth of each element was 55 MHz and 50% respectively. The measured crosstalk at the center frequency was -45 dB in water.

  10. RF Performance of Layer-Structured Broadband Passive Millimeter-Wave Imaging System

    Directory of Open Access Journals (Sweden)

    Kunio Sakakibara

    2016-01-01

    Full Text Available Low profile and simple configuration are advantageous for RF module in passive millimeter-wave imaging system. High sensitivity over broad operation bandwidth is also necessary to detect right information from weak signal. We propose a broadband layer-structured module with low profile, simple structure, and ease of manufacture. This module is composed of a lens antenna and a detector module that consists of a detector circuit and a broadband microstrip-to-waveguide transition. The module forms a layer structure as a printed substrate with detector circuit is fixed between two metal plates with horn antennas and back-short waveguides. We developed a broadband passive millimeter-wave imaging module composed of a lens antenna and a detector module in this work. The gain and the antenna efficiency were measured, and the broadband operation was observed for the lens antenna. For the detector module, peak sensitivity was 8100 V/W. Furthermore, the detector module recognized a difference in the absorber’s temperature. The designs of the lens antenna and the detector module are presented and the RF performances of these components are reported. Finally, passive millimeter-wave imaging of a car, a human, and a metal plate in clothes is demonstrated in this paper.

  11. Direct UV-written broadband directional broadband planar waveguide couplers

    DEFF Research Database (Denmark)

    Olivero, Massimo; Svalgaard, Mikael

    2005-01-01

    We report the fabrication of broadband directional couplers by direct UV-writing. The fabrication process is shown to be beneficial, robust and flexible. The components are compact and show superior performance in terms of loss and broadband operation.......We report the fabrication of broadband directional couplers by direct UV-writing. The fabrication process is shown to be beneficial, robust and flexible. The components are compact and show superior performance in terms of loss and broadband operation....

  12. Simultaneously measured signals in scanning probe microscopy with a needle sensor: frequency shift and tunneling current.

    Science.gov (United States)

    Morawski, Ireneusz; Voigtländer, Bert

    2010-03-01

    We present combined noncontact scanning force microscopy and tunneling current images of a platinum(111) surface obtained by means of a 1 MHz quartz needle sensor. The low-frequency circuit of the tunneling current was combined with a high-frequency signal of the quartz resonator enabling full electrical operation of the sensor. The frequency shift and the tunneling current were detected simultaneously, while the feedback control loop of the topography signal was fed using one of them. In both cases, the free signal that was not connected to the feedback loop reveals proportional-integral controller errorlike behavior, which is governed by the time derivative of the topography signal. A procedure is proposed for determining the mechanical oscillation amplitude by utilizing the tunneling current also including the average tip-sample work function.

  13. Monolithic optoelectronic integrated broadband optical receiver with graphene photodetectors

    Directory of Open Access Journals (Sweden)

    Cheng Chuantong

    2017-07-01

    Full Text Available Optical receivers with potentially high operation bandwidth and low cost have received considerable interest due to rapidly growing data traffic and potential Tb/s optical interconnect requirements. Experimental realization of 65 GHz optical signal detection and 262 GHz intrinsic operation speed reveals the significance role of graphene photodetectors (PDs in optical interconnect domains. In this work, a novel complementary metal oxide semiconductor post-backend process has been developed for integrating graphene PDs onto silicon integrated circuit chips. A prototype monolithic optoelectronic integrated optical receiver has been successfully demonstrated for the first time. Moreover, this is a firstly reported broadband optical receiver benefiting from natural broadband light absorption features of graphene material. This work is a perfect exhibition of the concept of monolithic optoelectronic integration and will pave way to monolithically integrated graphene optoelectronic devices with silicon ICs for three-dimensional optoelectronic integrated circuit chips.

  14. Monolithic optoelectronic integrated broadband optical receiver with graphene photodetectors

    Science.gov (United States)

    Cheng, Chuantong; Huang, Beiju; Mao, Xurui; Zhang, Zanyun; Zhang, Zan; Geng, Zhaoxin; Xue, Ping; Chen, Hongda

    2017-07-01

    Optical receivers with potentially high operation bandwidth and low cost have received considerable interest due to rapidly growing data traffic and potential Tb/s optical interconnect requirements. Experimental realization of 65 GHz optical signal detection and 262 GHz intrinsic operation speed reveals the significance role of graphene photodetectors (PDs) in optical interconnect domains. In this work, a novel complementary metal oxide semiconductor post-backend process has been developed for integrating graphene PDs onto silicon integrated circuit chips. A prototype monolithic optoelectronic integrated optical receiver has been successfully demonstrated for the first time. Moreover, this is a firstly reported broadband optical receiver benefiting from natural broadband light absorption features of graphene material. This work is a perfect exhibition of the concept of monolithic optoelectronic integration and will pave way to monolithically integrated graphene optoelectronic devices with silicon ICs for three-dimensional optoelectronic integrated circuit chips.

  15. Broadband Nonlinear Signal Processing in Silicon Nanowires

    DEFF Research Database (Denmark)

    Yvind, Kresten; Pu, Minhao; Hvam, Jørn Märcher

    The fast non-linearity of silicon allows Tbit/s optical signal processing. By choosing suitable dimensions of silicon nanowires their dispersion can be tailored to ensure a high nonlinearity at power levels low enough to avoid significant two-photon abso We have fabricated low insertion...

  16. Adding seismic broadband analysis to characterize Andean backarc seismicity in Argentina

    Science.gov (United States)

    Alvarado, P.; Giuliano, A.; Beck, S.; Zandt, G.

    2007-05-01

    Characterization of the highly seismically active Andean backarc is crucial for assessment of earthquake hazards in western Argentina. Moderate-to-large crustal earthquakes have caused several deaths, damage and drastic economic consequences in Argentinean history. We have studied the Andean backarc crust between 30°S and 36°S using seismic broadband data available from a previous ("the CHARGE") IRIS-PASSCAL experiment. We collected more than 12 terabytes of continuous seismic data from 22 broadband instruments deployed across Chile and Argentina during 1.5 years. Using free software we modeled full regional broadband waveforms and obtained seismic moment tensor inversions of crustal earthquakes testing for the best focal depth for each event. We also mapped differences in the Andean backarc crustal structure and found a clear correlation with different types of crustal seismicity (i.e. focal depths, focal mechanisms, magnitudes and frequencies of occurrence) and previously mapped terrane boundaries. We now plan to use the same methodology to study other regions in Argentina using near-real time broadband data available from the national seismic (INPRES) network and global seismic networks operating in the region. We will re-design the national seismic network to optimize short-period and broadband seismic station coverage for different network purposes. This work is an international effort that involves researchers and students from universities and national government agencies with the goal of providing more information about earthquake hazards in western Argentina.

  17. Identifying Broadband Rotational Spectra with Neural Networks

    Science.gov (United States)

    Zaleski, Daniel P.; Prozument, Kirill

    2017-06-01

    A typical broadband rotational spectrum may contain several thousand observable transitions, spanning many species. Identifying the individual spectra, particularly when the dynamic range reaches 1,000:1 or even 10,000:1, can be challenging. One approach is to apply automated fitting routines. In this approach, combinations of 3 transitions can be created to form a "triple", which allows fitting of the A, B, and C rotational constants in a Watson-type Hamiltonian. On a standard desktop computer, with a target molecule of interest, a typical AUTOFIT routine takes 2-12 hours depending on the spectral density. A new approach is to utilize machine learning to train a computer to recognize the patterns (frequency spacing and relative intensities) inherit in rotational spectra and to identify the individual spectra in a raw broadband rotational spectrum. Here, recurrent neural networks have been trained to identify different types of rotational spectra and classify them accordingly. Furthermore, early results in applying convolutional neural networks for spectral object recognition in broadband rotational spectra appear promising. Perez et al. "Broadband Fourier transform rotational spectroscopy for structure determination: The water heptamer." Chem. Phys. Lett., 2013, 571, 1-15. Seifert et al. "AUTOFIT, an Automated Fitting Tool for Broadband Rotational Spectra, and Applications to 1-Hexanal." J. Mol. Spectrosc., 2015, 312, 13-21. Bishop. "Neural networks for pattern recognition." Oxford university press, 1995.

  18. On temporal correlations in high-resolution frequency counting

    OpenAIRE

    Dunker, Tim; Hauglin, Harald; Rønningen, Ole Petter

    2016-01-01

    We analyze noise properties of time series of frequency data from different counting modes of a Keysight 53230A frequency counter. We use a 10 MHz reference signal from a passive hydrogen maser connected via phase-stable Huber+Suhner Sucoflex 104 cables to the reference and input connectors of the counter. We find that the high resolution gap-free (CONT) frequency counting process imposes long-term correlations in the output data, resulting in a modified Allan deviation that is characteristic...

  19. The promise of downlink MU-MIMO for high-capacity next generation mobile broadband networks based on IEEE 802.16 m

    Directory of Open Access Journals (Sweden)

    Papathanassiou Apostolos

    2011-01-01

    Full Text Available Abstract The dramatic increase of the demand for mobile broadband services poses stringent requirements on the performance evolution of currently deployed mobile broadband networks, such as Mobile WiMAX Release 1 and 3GPP LTE Release 8. Although the combination of single-user multiple-input multiple-output (SU-MIMO and orthogonal frequency division multiple access (OFDMA provide the appropriate technologies for improving the downlink performance of third generation (3G code division multiple access (CDMA-based mobile radio systems and, thus, address the current mobile internet requirements, a fundamental paradigm shift is required to cope with the constantly increasing mobile broadband data rate and spectral efficiency requirements. Among the different technologies available for making the paradigm shift from current to next-generation mobile broadband networks, multiuser MIMO (MU-MIMO constitutes the most promising technology because of its significant performance improvement advantages. In this article, we analyze the performance of MU-MIMO under a multitude of deployment scenarios and system parameters through extensive system-level simulations which are based on widely used system-level evaluation methodologies. The target mobile broadband system used in the simulations is IEEE 802.16 m which was recently adopted by ITU-R as an IMT-Advanced technology along with 3GPP LTE-Advanced. The results provide insights into different aspects of MU-MIMO with respect to system-level performance, parameter sensitivity, and deployment scenarios, and they can be used by the mobile broadband network designer for maximizing the benefits of MU-MIMO in a scenario with specific deployment requirements and goals.

  20. Spectral Properties of Chaotic Signals Generated by the Bernoulli Map

    Directory of Open Access Journals (Sweden)

    Rafael A. da Costa

    2014-11-01

    Full Text Available In the last decades, the use of chaotic signals as broadband carriers has been considered in Telecommunications. Despite the relevance of the frequency domain analysis in this field, there are few studies that are concerned with spectral properties of chaotic signals. Bearing this in mind, this paper aims the characterization of the power spectral density (PSD of chaotic orbits generated by Bernoulli maps. We obtain analytic expressions for autocorrelation sequence, PSD and essential bandwidth for chaotic orbits generated by this map as function of the family parameter and Lyapunov exponent. Moreover, we verify that analytical expressions match numerical results. We conclude that the power of the generated orbits is concentrated in low frequencies for all parameters values. Besides, it is possible to obtain chaotic narrowband signals.

  1. Broadband pulsed difference frequency generation laser source centered 3326 nm based on ring fiber lasers

    Science.gov (United States)

    Chen, Guangwei; Li, Wenlei

    2018-03-01

    A broadband pulsed mid-infrared difference frequency generation (DFG) laser source based on MgO-doped congruent LiNbO3 bulk is experimentally demonstrated, which employs a homemade pulsed ytterbium-doped ring fiber laser and a continuous wave erbium-doped ring fiber laser to act as seed sources. The experimental results indicate that the perfect phase match crystal temperature is about 74.5∘C. The maximum spectrum bandwidth of idler is about 60 nm with suitable polarization states of fundamental lights. The central wavelength of idlers varies from 3293 nm to 3333 nm over the crystal temperature ranges of 70.4-76∘C. A jump of central wavelength exists around crystal temperature of 72∘C with variation of about 30 nm. The conversion efficiency of DFG can be tuned with the crystal temperature and polarization states of fundamental lights.

  2. A new method of hybrid frequency hopping signals selection and blind parameter estimation

    Science.gov (United States)

    Zeng, Xiaoyu; Jiao, Wencheng; Sun, Huixian

    2018-04-01

    Frequency hopping communication is widely used in military communications at home and abroad. In the case of single-channel reception, it is scarce to process multiple frequency hopping signals both effectively and simultaneously. A method of hybrid FH signals selection and blind parameter estimation is proposed. The method makes use of spectral transformation, spectral entropy calculation and PRI transformation basic theory to realize the sorting and parameter estimation of the components in the hybrid frequency hopping signal. The simulation results show that this method can correctly classify the frequency hopping component signal, and the estimated error of the frequency hopping period is about 5% and the estimated error of the frequency hopping frequency is less than 1% when the SNR is 10dB. However, the performance of this method deteriorates seriously at low SNR.

  3. High-Performance Ultraviolet-to-Infrared Broadband Perovskite Photodetectors Achieved via Inter-/Intraband Transitions

    KAUST Repository

    Alwadai, Norah Mohammed Mosfer

    2017-10-17

    A high-performance vertically injected broadband UV-to-IR photodetector based on Gd-doped ZnO nanorods (NRs)/CH3NH3PbI3 perovskite heterojunction was fabricated on metal substrates. Our perovskite-based photodetector is sensitive to a broad spectral range, from ultraviolet to infrared light region (λ = 250–1357 nm). Such structure leads to a high photoresponsivity of 28 and 0.22 A/W, for white light and IR illumination, respectively, with high detectivity values of 1.1 × 1012 and 9.3 × 109 Jones. Optical characterizations demonstrate that the IR detection is due to intraband transition in the perovskite material. Metal substrate boosts carrier injection, resulting in higher responsivity compared to the conventional devices grown on glass, whereas the presence of Gd increases the ZnO NRs performance. For the first time, the perovskite-based photodetector is demonstrated to extend its detection capability to IR (>1000 nm) with high room temperature responsivity across the detected spectrum, leading to a high-performance ingenious cost-effective UV-to-IR broadband photodetector design for large-scale applications.

  4. Compact broadband circularly polarised slot antenna for universal UHF RFID readers

    DEFF Research Database (Denmark)

    Xu, Bo; Zhang, Shuai; Liu, Yusha

    2015-01-01

    A compact broadband circularly polarised (CP) slot antenna is designed for universal ultra-high-frequency (UHF) radio frequency identification (RFID) readers. The antenna consists of an L-shaped metal strip and a square-slot-loaded ground plane with four tuning stubs. The total size is 100 mm×100mm......×1.6 mm. The measured –10 dB impedance bandwidth is 40.7% (772–1166 MHz) and the measured 3 dB axial ratio (AR) bandwidth is 13.9% (840–965 MHz). Both the impedance and AR bandwidth cover the worldwide UHF RFID band....

  5. A broadband damper design inspired by cartilage-like relaxation mechanisms

    Science.gov (United States)

    Liu, Lejie; Usta, Ahmet D.; Eriten, Melih

    2017-10-01

    In this study, we introduce a broadband damper design inspired by the cartilage-like relaxation mechanisms. In particular, we study broadband (static to 10 kHz) dissipative properties of model cartilage systems by probe-based static and dynamic indentation, and validate that fractional Zener models can simulate the empirical data up to a desirable accuracy within the frequency range of interest. Utilizing these observations, we design a composite damper design where a poroelastic layer is sandwiched between two hard materials, and load transfer occurs across interfaces with multiple length scales. Modeling those interfaces with fractional Zener elements in parallel configuration, and manipulating the distribution of the Zener elements across different peak relaxation frequencies, we obtain a relatively constant loss factor within an unprecedented frequency range (3-3 kHz). We also discuss how these findings can be employed in a practical damping design.

  6. Synthesis of multi-wavelength temporal phase-shifting algorithms optimized for high signal-to-noise ratio and high detuning robustness using the frequency transfer function

    OpenAIRE

    Servin, Manuel; Padilla, Moises; Garnica, Guillermo

    2016-01-01

    Synthesis of single-wavelength temporal phase-shifting algorithms (PSA) for interferometry is well-known and firmly based on the frequency transfer function (FTF) paradigm. Here we extend the single-wavelength FTF-theory to dual and multi-wavelength PSA-synthesis when several simultaneous laser-colors are present. The FTF-based synthesis for dual-wavelength PSA (DW-PSA) is optimized for high signal-to-noise ratio and minimum number of temporal phase-shifted interferograms. The DW-PSA synthesi...

  7. Extracting a shape function for a signal with intra-wave frequency modulation.

    Science.gov (United States)

    Hou, Thomas Y; Shi, Zuoqiang

    2016-04-13

    In this paper, we develop an effective and robust adaptive time-frequency analysis method for signals with intra-wave frequency modulation. To handle this kind of signals effectively, we generalize our data-driven time-frequency analysis by using a shape function to describe the intra-wave frequency modulation. The idea of using a shape function in time-frequency analysis was first proposed by Wu (Wu 2013 Appl. Comput. Harmon. Anal. 35, 181-199. (doi:10.1016/j.acha.2012.08.008)). A shape function could be any smooth 2π-periodic function. Based on this model, we propose to solve an optimization problem to extract the shape function. By exploring the fact that the shape function is a periodic function with respect to its phase function, we can identify certain low-rank structure of the signal. This low-rank structure enables us to extract the shape function from the signal. Once the shape function is obtained, the instantaneous frequency with intra-wave modulation can be recovered from the shape function. We demonstrate the robustness and efficiency of our method by applying it to several synthetic and real signals. One important observation is that this approach is very stable to noise perturbation. By using the shape function approach, we can capture the intra-wave frequency modulation very well even for noise-polluted signals. In comparison, existing methods such as empirical mode decomposition/ensemble empirical mode decomposition seem to have difficulty in capturing the intra-wave modulation when the signal is polluted by noise. © 2016 The Author(s).

  8. High frequency seismic signal generated by landslides on complex topographies: from point source to spatially distributed sources

    Science.gov (United States)

    Mangeney, A.; Kuehnert, J.; Capdeville, Y.; Durand, V.; Stutzmann, E.; Kone, E. H.; Sethi, S.

    2017-12-01

    During their flow along the topography, landslides generate seismic waves in a wide frequency range. These so called landquakes can be recorded at very large distances (a few hundreds of km for large landslides). The recorded signals depend on the landslide seismic source and the seismic wave propagation. If the wave propagation is well understood, the seismic signals can be inverted for the seismic source and thus can be used to get information on the landslide properties and dynamics. Analysis and modeling of long period seismic signals (10-150s) have helped in this way to discriminate between different landslide scenarios and to constrain rheological parameters (e.g. Favreau et al., 2010). This was possible as topography poorly affects wave propagation at these long periods and the landslide seismic source can be approximated as a point source. In the near-field and at higher frequencies (> 1 Hz) the spatial extent of the source has to be taken into account and the influence of the topography on the recorded seismic signal should be quantified in order to extract information on the landslide properties and dynamics. The characteristic signature of distributed sources and varying topographies is studied as a function of frequency and recording distance.The time dependent spatial distribution of the forces applied to the ground by the landslide are obtained using granular flow numerical modeling on 3D topography. The generated seismic waves are simulated using the spectral element method. The simulated seismic signal is compared to observed seismic data from rockfalls at the Dolomieu Crater of Piton de la Fournaise (La Réunion).Favreau, P., Mangeney, A., Lucas, A., Crosta, G., and Bouchut, F. (2010). Numerical modeling of landquakes. Geophysical Research Letters, 37(15):1-5.

  9. Fatigue characteristics of high strength fire resistance steel for frame structure and time-frequency analysis its acoustic emission signal

    International Nuclear Information System (INIS)

    Kim, Hyun Soo; Nam, Ki Woo; Kang, Chang Young

    2000-01-01

    Demand for now nondestructive evaluation are growing to detect fatigue crack growth behavior to predict long term performance of materials and structure in aggressive environments, especially when they are in non-visible area. Acoustic emission technique is well suited to these problems and has drawn a keen interests because of its dynamic detection ability, extreme sensitivity and location of growing defects. In this study, we analysed acoustic emission signals obtained in fatigue and tensile test of high strength fire resistance steel for frame structure with time-frequency analysis methods. The main frequency range is different in the noise and the fatigue crack propagation. It could be classified that it were also generated by composite fracture mechanics of cleavage, dimple, inclusion separation etc

  10. Tunable Broadband Nanocarbon Transparent Conductor by Electrochemical Intercalation.

    Science.gov (United States)

    Wan, Jiayu; Xu, Yue; Ozdemir, Burak; Xu, Lisha; Sushkov, Andrei B; Yang, Zhi; Yang, Bao; Drew, Dennis; Barone, Veronica; Hu, Liangbing

    2017-01-24

    Optical transparent and electrical conducting materials with broadband transmission are important for many applications in optoelectronic, telecommunications, and military devices. However, studies of broadband transparent conductors and their controlled modulation are scarce. In this study, we report that reversible transmittance modulation has been achieved with sandwiched nanocarbon thin films (containing carbon nanotubes (CNTs) and reduced graphene oxide (rGO)) via electrochemical alkali-ion intercalation/deintercalation. The transmittance modulation covers a broad range from the visible (450 nm) to the infrared (5 μm), which can be achieved only by rGO rather than pristine graphene films. The large broadband transmittance modulation is understood with DFT calculations, which suggest a decrease in interband transitions in the visible range as well as a reduced reflection in the IR range upon intercalation. We find that a larger interlayer distance in few-layer rGO results in a significant increase in transparency in the infrared region of the spectrum, in agreement with experimental results. Furthermore, a reduced plasma frequency in rGO compared to few-layer graphene is also important to understand the experimental results for broadband transparency in rGO. The broadband transmittance modulation of the CNT/rGO/CNT systems can potentially lead to electrochromic and thermal camouflage applications.

  11. The Real-time Frequency Spectrum Analysis of Neutron Pulse Signal Series

    International Nuclear Information System (INIS)

    Tang Yuelin; Ren Yong; Wei Biao; Feng Peng; Mi Deling; Pan Yingjun; Li Jiansheng; Ye Cenming

    2009-01-01

    The frequency spectrum analysis of neutron pulse signal is a very important method in nuclear stochastic signal processing Focused on the special '0' and '1' of neutron pulse signal series, this paper proposes new rotation-table and realizes a real-time frequency spectrum algorithm under 1G Hz sample rate based on PC with add, address and SSE. The numerical experimental results show that under the count rate of 3X10 6 s -1 , this algorithm is superior to FFTW in time-consumption and can meet the real-time requirement of frequency spectrum analysis. (authors)

  12. A cervid vocal fold model suggests greater glottal efficiency in calling at high frequencies.

    Directory of Open Access Journals (Sweden)

    Ingo R Titze

    2010-08-01

    Full Text Available Male Rocky Mountain elk (Cervus elaphus nelsoni produce loud and high fundamental frequency bugles during the mating season, in contrast to the male European Red Deer (Cervus elaphus scoticus who produces loud and low fundamental frequency roaring calls. A critical step in understanding vocal communication is to relate sound complexity to anatomy and physiology in a causal manner. Experimentation at the sound source, often difficult in vivo in mammals, is simulated here by a finite element model of the larynx and a wave propagation model of the vocal tract, both based on the morphology and biomechanics of the elk. The model can produce a wide range of fundamental frequencies. Low fundamental frequencies require low vocal fold strain, but large lung pressure and large glottal flow if sound intensity level is to exceed 70 dB at 10 m distance. A high-frequency bugle requires both large muscular effort (to strain the vocal ligament and high lung pressure (to overcome phonation threshold pressure, but at least 10 dB more intensity level can be achieved. Glottal efficiency, the ration of radiated sound power to aerodynamic power at the glottis, is higher in elk, suggesting an advantage of high-pitched signaling. This advantage is based on two aspects; first, the lower airflow required for aerodynamic power and, second, an acoustic radiation advantage at higher frequencies. Both signal types are used by the respective males during the mating season and probably serve as honest signals. The two signal types relate differently to physical qualities of the sender. The low-frequency sound (Red Deer call relates to overall body size via a strong relationship between acoustic parameters and the size of vocal organs and body size. The high-frequency bugle may signal muscular strength and endurance, via a 'vocalizing at the edge' mechanism, for which efficiency is critical.

  13. Advanced Time-Frequency Representation in Voice Signal Analysis

    Directory of Open Access Journals (Sweden)

    Dariusz Mika

    2018-03-01

    Full Text Available The most commonly used time-frequency representation of the analysis in voice signal is spectrogram. This representation belongs in general to Cohen's class, the class of time-frequency energy distributions. From the standpoint of properties of the resolution spectrogram representation is not optimal. In Cohen class representations are known which have a better resolution properties. All of them are created by smoothing the Wigner-Ville'a (WVD distribution characterized by the best resolution, however, the biggest harmful interference. Used smoothing functions decide about a compromise between the properties of resolution and eliminating harmful interference term. Another class of time-frequency energy distributions is the affine class of distributions. From the point of view of readability of analysis the best properties are known so called Redistribution of energy caused by the use of a general methodology referred to as reassignment to any time-frequency representation. Reassigned distributions efficiently combine a reduction of the interference terms provided by a well adapted smoothing kernel and an increased concentration of the signal components.

  14. Frequency analysis of the visual steady-state response measured with the fast optical signal in younger and older adults

    OpenAIRE

    Tse, Chun-Yu; Gordon, Brian A.; Fabiani, Monica; Gratton, Gabriele

    2010-01-01

    Relatively high frequency activity (>4 Hz) carries important information about the state of the brain or its response to high frequency events. The electroencephalogram (EEG) is commonly used to study these changes because it possesses high temporal resolution and a good signal-to-noise ratio. However, it provides limited spatial information. Non-invasive fast optical signals (FOS) have been proposed as a neuroimaging tool combining spatial and temporal resolution. Yet, this technique has not...

  15. The Low Pitch of High-Frequency Complex Tones Relies on Temporal Fine Structure Information

    DEFF Research Database (Denmark)

    Santurette, Sébastien; Dau, Torsten

    2010-01-01

    High-frequency complex tones containing only unresolved harmonic components with a frequency spacing Δf usually evoke a low pitch equal to Δf. However, for inharmonic components, the low pitch is often found to deviate slightly from Δf. Whether this pitch shift relies exclusively on temporal fine...... structure (TFS) cues has been a matter of debate. It is also controversial up to which frequency TFS information remains available, and to what extent envelope cues become dominant as frequency increases. Using a pitch-matching paradigm, this study investigated whether the pitch of transposed tones.......5]. All stimuli were presented at 50 dB SPL in broadband pink-noise (13.5 dB/Hz at 1 kHz), and 40 matches per condition were obtained. For fenv = fc/11.5, the results favored hypothesis A for all values of fc, indicating that TFS cues are available and used for pitch extraction, up to at least 7 k...

  16. High-harmonic electron bunching in the field of a signal wave and the use of this effect in cyclotron masers with frequency multiplication

    Directory of Open Access Journals (Sweden)

    I. V. Bandurkin

    2005-01-01

    Full Text Available A method of organizing electron-wave interaction at the multiplied frequency of the signal wave is proposed. This type of electron-wave interaction provides multiplied-frequency electron bunching, which leads to formation of an intense harmonic of the electron current at a selected multiplied frequency of the signal wave. This effect is attractive for the use in klystron-type cyclotron masers with frequency multiplication as a way to increase the output frequency and improve the selectivity.

  17. Advent of broadband public-switched communications

    Science.gov (United States)

    Casey, John J.

    1992-02-01

    Advances in data communications infrastructure, display technology, and man-machine interfaces have changed business applications and the requirements of public network data transport. These changes have created opportunities for a new generation of public broadband services to more efficiently extend high speed communications capabilities beyond the customer premises. This paper provides a view of the technology and market evolution of these public broadband data communications services, and suggests early customer networked applications that justify the deployment of a public switched broadband network infrastructure.

  18. Hybrid Simulations of the Broadband Ground Motions for the 2008 MS8.0 Wenchuan, China, Earthquake

    Science.gov (United States)

    Yu, X.; Zhang, W.

    2012-12-01

    The Ms8.0 Wenchuan earthquake occurred on 12 May 2008 at 14:28 Beijing Time. It is the largest event happened in the mainland of China since the 1976, Mw7.6, Tangshan earthquake. Due to occur in the mountainous area, this great earthquake and the following thousands aftershocks also caused many other geological disasters, such as landslide, mud-rock flow and "quake lakes" which formed by landslide-induced reservoirs. These resulted in tremendous losses of life and property. Casualties numbered more than 80,000 people, and there were major economic losses. However, this earthquake is the first Ms 8 intraplate earthquake with good close fault strong motion coverage. Over four hundred strong motion stations of the National Strong Motion Observation Network System (NSMONS) recorded the mainshock. Twelve of them located within 20 km of the fault traces and another 33 stations located within 100 km. These observations, accompanying with the hundreds of GPS vectors and multiple ALOS INSAR images, provide an unprecedented opportunity to study the rupture process of such a great intraplate earthquake. In this study, we calculate broadband near-field ground motion synthetic waveforms of this great earthquake using a hybrid broadband ground-motion simulation methodology, which combines a deterministic approach at low frequencies (f < 1.0 Hz) with a theoretic Green's function calculation approach at high frequency ( ~ 10.0 Hz). The fault rupture is represented kinematically and incorporates spatial heterogeneity in slip, rupture speed, and rise time that were obtained by an inversion kinematic source model. At the same time, based on the aftershock data, we analyze the site effects for the near-field stations. Frequency-dependent site-amplification values for each station are calculated using genetic algorithms. For the calculation of the synthetic waveforms, at first, we carry out simulations using the hybrid methodology for the frequency up to 10.0 Hz. Then, we consider for

  19. Ionospheric heating with oblique high-frequency waves

    International Nuclear Information System (INIS)

    Field, E.C. Jr.; Bloom, R.M.; Kossey, P.A.

    1990-01-01

    This paper presents calculations of ionospheric electron temperature and density perturbations and ground-level signal changes produced by intense oblique high-frequency (HF) radio waves. The analysis takes into account focusing at caustics, the consequent Joule heating of the surrounding plasma, heat conduction, diffusion, and recombination processes, these being the effects of a powerful oblique modifying wave. It neglects whatever plasma instabilities might occur. The authors then seek effects on a secondary test wave that is propagated along the same path as the first. The calculations predict ground-level field strength reductions of several decibels in the test wave for modifying waves having effective radiated power (ERP) in the 85- to 90-dBW range. These field strength changes are similar in sign, magnitude, and location to ones measured in Soviet experiments. The location of the signal change is sensitive to the frequency and the model ionosphere assumed; so future experiments should employ the widest possible range of frequencies and propagation conditions. An ERP of 90 dBW seems to be a sort of threshold that, if exceeded, might result in substantial rather than small signal changes. The conclusions are based solely on Joule heating and subsequent refraction of waves passing through caustic regions

  20. Relativistic runaway breakdown in low-frequency radio

    Science.gov (United States)

    Füllekrug, Martin; Roussel-Dupré, Robert; Symbalisty, Eugene M. D.; Chanrion, Olivier; Odzimek, Anna; van der Velde, Oscar; Neubert, Torsten

    2010-01-01

    The electromagnetic radiation emitted by an electron avalanche beam resulting from relativistic runaway breakdown within the Earth's atmosphere is investigated. It is found from theoretical modeling with a computer simulation that the electron beam emits electromagnetic radiation which is characterized by consecutive broadband pulses in the low-frequency radio range from ˜10 to 300 kHz at a distance of ˜800 km. Experimental evidence for the existence of consecutive broadband pulses is provided by low-frequency radio observations of sprite-producing lightning discharges at a distance of ˜550 km. The measured broadband pulses occur ˜4-9 ms after the sprite-producing lightning discharge, they exhibit electromagnetic radiation which mainly spans the frequency range from ˜50 to 350 kHz, and they exhibit complex waveforms without the typical ionospheric reflection of the first hop sky wave. Two consecutive pulses occur ˜4.5 ms and ˜3 ms after the causative lightning discharge and coincide with the sprite luminosity. It is concluded that relativistic runaway breakdown within the Earth's atmosphere can emit broadband electromagnetic pulses and possibly generates sprites. The source location of the broadband pulses can be determined with an interferometric network of wideband low-frequency radio receivers to lend further experimental support to the relativistic runaway breakdown theory.

  1. Frequency analysis of the visual steady-state response measured with the fast optical signal in younger and older adults.

    Science.gov (United States)

    Tse, Chun-Yu; Gordon, Brian A; Fabiani, Monica; Gratton, Gabriele

    2010-09-01

    Relatively high frequency activity (>4Hz) carries important information about the state of the brain or its response to high frequency events. The electroencephalogram (EEG) is commonly used to study these changes because it possesses high temporal resolution and a good signal-to-noise ratio. However, it provides limited spatial information. Non-invasive fast optical signals (FOS) have been proposed as a neuroimaging tool combining spatial and temporal resolution. Yet, this technique has not been applied to study high frequency brain oscillations because of its relatively low signal-to-noise ratio. Here we investigate the sensitivity of FOS to relatively high-frequency brain oscillations. We measured the steady-state optical response elicited in medial and lateral occipital cortex by checkerboard reversals occurring at 4, 6, and 8Hz in younger and older adults. Stimulus-dependent oscillations were observed at the predicted stimulation frequency. In addition, in the younger adults the FOS steady-state response was smaller in lateral than medial areas, whereas in the older adults it was reversed in these two cortical regions. This may reflect diminished top-down inhibitory control in the older adults. The results indicate that FOS can be used to study the modulation of relatively high-frequency brain oscillations in adjacent cortical regions. Copyright (c) 2010 Elsevier B.V. All rights reserved.

  2. Broadband infrared absorption enhancement by electroless-deposited silver nanoparticles

    Directory of Open Access Journals (Sweden)

    Gritti Claudia

    2016-07-01

    Full Text Available Decorating semiconductor surfaces with plasmonic nanoparticles (NPs is considered a viable solution for enhancing the absorptive properties of photovoltaic and photodetecting devices. We propose to deposit silver NPs on top of a semiconductor wafer by a cheap and fast electroless plating technique. Optical characterization confirms that the random array of electroless-deposited NPs improves absorption by up to 20% in a broadband of near-infrared frequencies from the bandgap edge to 2000 nm. Due to the small filling fraction of particles, the reflection in the visible range is practically unchanged, which points to the possible applications of such deposition method for harvesting photons in nanophotonics and photovoltaics. The broadband absorption is a consequence of the resonant behavior of particles with different shapes and sizes, which strongly localize the incident light at the interface of a high-index semiconductor substrate. Our hypothesis is substantiated by examining the plasmonic response of the electroless-deposited NPs using both electron energy loss spectroscopy and numerical calculations.

  3. A Broadband UHF Tag Antenna For Near-Field and Far-Field RFID Communications

    Directory of Open Access Journals (Sweden)

    M. Dhaouadi

    2014-12-01

    Full Text Available The paper deals with the design of passive broadband tag antenna for Ultra-High Frequency (UHF band. The antenna is intended for both near and far fields Radio Frequency Identification (RFID applications. The meander dipole tag antenna geometry modification is designed for frequency bandwidth increasing. The measured bandwidth of the proposed broadband Tag antenna is more than 140 MHz (820–960 MHz, which can cover the entire UHF RFID band. A comparison between chip impedance of datasheet and the measured chip impedance has been used in our simulations. The proposed progressive meandered antenna structure, with an overall size of 77 mm × 14 mm × 0.787 mm, produces strong and uniform magnetic field distribution in the near-field zone. The antenna impedance is matched to common UHF chips in market simply by tuning its capacitive and inductive values since a perfect matching is required in the antenna design in order to enhance the near and the far field communications. Measurements confirm that the designed antenna exhibits good performance of Tag identification for both near-field and far-field UHF RFID applications.

  4. Broadband Polarization-Insensitive Wavelength Conversion Based on Non-Degenerate Four-Wave Mixing in a Silicon Nanowire

    DEFF Research Database (Denmark)

    Pu, Minhao; Hu, Hao; Ji, Hua

    2012-01-01

    We experimentally demonstrate broadband polarization-insensitive one-to-two wavelength conversion of a 10-Gb/s DPSK data signal based on non-degenerate four-wave mixing in a silicon nanowire with bit-error rate measurements.......We experimentally demonstrate broadband polarization-insensitive one-to-two wavelength conversion of a 10-Gb/s DPSK data signal based on non-degenerate four-wave mixing in a silicon nanowire with bit-error rate measurements....

  5. Femtosecond Broadband Stimulated Raman Spectroscopy

    International Nuclear Information System (INIS)

    Lee, Soo-Y; Yoon, Sagwoon; Mathies, Richard A

    2006-01-01

    Femtosecond broadband stimulated Raman spectroscopy (FSRS) is a new technique where a narrow bandwidth picosecond Raman pump pulse and a red-shifted broadband femtosecond Stokes probe pulse (with or without time delay between the pulses) act on a sample to produce a high resolution Raman gain spectrum with high efficiency and speed, free from fluorescence background interference. It can reveal vibrational structural information and dynamics of stationary or transient states. Here, the quantum picture for femtosecond broadband stimulated Raman spectroscopy (FSRS) is used to develop the semiclassical coupled wave theory of the phenomenon and to derive an expression for the measurable Raman gain in FSRS. The semiclassical theory is applied to study the dependence of lineshapes in FSRS on the pump-probe time delay and to deduce vibrational dephasing times in cyclohexane in the ground state

  6. Layer-by-Layer-Assembled High-Performance Broadband Antireflection Coatings

    KAUST Repository

    Shimomura, Hiroomi

    2010-03-24

    Nanoparticles are indispensable ingredients of solution-processed optical, dielectric, and catalytic thin films. Although solution-based methods are promising low-cost alternatives to vacuum methods, they can have significant limitations. Coating uniformity, thickness control, roughness control, mechanical durability, and incorporation of a diverse set of functional organic molecules into nanoparticle thin films are major challenges. We have used the electrostatic layer-by-layer assembly technique to make uniform, conformal multistack nanoparticle thin films for optical applications with precise thickness control over each stack. Two particularly sought-after optical applications are broadband antireflection and structural color. The effects of interstack and surface roughness on optical properties of these constructs (e.g., haze and spectral response) have been studied quantitatively using a combination of Fourier-transform methods and atomic force microscopy measurements. Deconvoluting root-mean-square roughness into its large-, intermediate-, and small-scale components enables enhanced optical simulations. A 4-stack broadband antireflection coating (<0.5% average reflectance in the visible range, and 0.2% haze) composed of alternating high-index (n ≈ 1.96) and low-index (n ≈ 1.28) stacks has been made on glass substrate. Films calcinated at 550 °C endure a one-hour-long cloth cleaning test under 100 kPa normal stress. © 2010 American Chemical Society.

  7. Adoption of Broadband Services

    DEFF Research Database (Denmark)

    Falch, Morten

    2008-01-01

    Broadband is seen as a key infrastructure for developing the information society. For this reason many Governments are actively engaged in stimulating investments in broadband infrastructures and use of broadband services. This chapter compares a wide range of broadband strategies in the most suc....... Many countries have provided active support for stimulating diffusion of broadband and national variants of this type of policies in different countries are important for an explanation of national differences in adoption of broadband....

  8. A High-Precision Time-Frequency Entropy Based on Synchrosqueezing Generalized S-Transform Applied in Reservoir Detection

    Directory of Open Access Journals (Sweden)

    Hui Chen

    2018-06-01

    Full Text Available According to the fact that high frequency will be abnormally attenuated when seismic signals travel across reservoirs, a new method, which is named high-precision time-frequency entropy based on synchrosqueezing generalized S-transform, is proposed for hydrocarbon reservoir detection in this paper. First, the proposed method obtains the time-frequency spectra by synchrosqueezing generalized S-transform (SSGST, which are concentrated around the real instantaneous frequency of the signals. Then, considering the characteristics and effects of noises, we give a frequency constraint condition to calculate the entropy based on time-frequency spectra. The synthetic example verifies that the entropy will be abnormally high when seismic signals have an abnormal attenuation. Besides, comparing with the GST time-frequency entropy and the original SSGST time-frequency entropy in field data, the results of the proposed method show higher precision. Moreover, the proposed method can not only accurately detect and locate hydrocarbon reservoirs, but also effectively suppress the impact of random noises.

  9. Time–frequency analysis of nonstationary complex magneto-hydro-dynamics in fusion plasma signals using the Choi–Williams distribution

    International Nuclear Information System (INIS)

    Xu, L.Q.; Hu, L.Q.; Chen, K.Y.; Li, E.Z.

    2013-01-01

    Highlights: • Choi–Williams distribution yields excellent time–frequency resolution for discrete signal. • CWD method provides clear time–frequency pictures of EAST and HT-7 fast MHD events. • CWD method has advantages to wavelets transform scalogram and the short-time Fourier transform spectrogram. • We discuss about how to choose the windows and free parameter of CWD method. -- Abstract: The Choi–Williams distribution is applied to the time–frequency analysis of signals describing rapid magneto-hydro-dynamic (MHD) modes and events in tokamak plasmas. A comparison is made with Soft X-ray (SXR) signals as well as Mirnov signal that shows the advantages of the Choi–Williams distribution over both continuous wavelets transform scalogram and the short-time Fourier transform spectrogram. Examples of MHD activities in HT-7 and EAST tokamak are shown, namely the onset of coupling tearing modes, high frequency precursors of sawtooth, and low frequency MHD instabilities in edge localized mode (ELM) free in H mode discharge

  10. Plastic straw: future of high-speed signaling

    Science.gov (United States)

    Song, Ha Il; Jin, Huxian; Bae, Hyeon-Min

    2015-11-01

    The ever-increasing demand for bandwidth triggered by mobile and video Internet traffic requires advanced interconnect solutions satisfying functional and economic constraints. A new interconnect called E-TUBE is proposed as a cost-and-power-effective all-electrical-domain wideband waveguide solution for high-speed high-volume short-reach communication links. The E-TUBE achieves an unprecedented level of performance in terms of bandwidth-per-carrier frequency, power, and density without requiring a precision manufacturing process unlike conventional optical/waveguide solutions. The E-TUBE exhibits a frequency-independent loss-profile of 4 dB/m and has nearly 20-GHz bandwidth over the V band. A single-sideband signal transmission enabled by the inherent frequency response of the E-TUBE renders two-times data throughput without any physical overhead compared to conventional radio frequency communication technologies. This new interconnect scheme would be attractive to parties interested in high throughput links, including but not limited to, 100/400 Gbps chip-to-chip communications.

  11. Optimization of carrier frequency and duty cycle for pulse modulation of biological signals.

    Science.gov (United States)

    Tandon, S N; Singh, S; Sharma, P K; Khosla, S

    1980-10-01

    Digital modulation techniques are commonly used for the recording and transmission of biological signals. Hitherto, the choice of subcarrier frequency for recording or transmission of biological signals has been arbitary and this usually results in poor signal to noise ratio (SNR) due to the limited frequency characteristics of the system. In the present study the frequency characteristics of the system (first order approximation) has been taken to be that of a Butterworth filter. Computations based on this assumption show that for a given input signal there exists an optimum subcarrier frequency and a corresponding optimum duty cycle which would give maximum SNR of the system. For convenience, a nomogram has been prepared and it has been shown that for a given frequency response of the system, the nomogram could be used for selecting an optimum subcarrier frequency and a corresponding duty cycle. The theoretical formulations have been verified with experimental work.

  12. A broadband electromagnetic UT system

    International Nuclear Information System (INIS)

    Repplinger, W.; Salzburger, H.J.

    1985-01-01

    An ultrasonic testing system based on contactless electromagnetic acoustic (E.M.A.) transduction has been developed by which broadband ultrasonic pulses are excited. This system overcomes disadvantages of usual E.M.A. transducers with meanderlike coil configuration, namely the excitation of narrowband pulses and the symmetrical radiation pattern. By dividing up a meanderlike coil into single elements and a time-delayed firing of the elements, whereby the time delay is given by the distance of the elements and the phase velocity of the wave propagating along the surface, the ultrasonic pulse radiated in one preferred direction becomes broadband by constructive interference. The signals radiated in the opposite direction do no more interfere. Its amplitude is smaller than that of the other direction, so that the transducer becomes uni-directional. This technique can be applied for the excitation of all dispersionless waves (bulk waves and guided waves)

  13. Broadband manipulation of refracted wavefronts by gradient acoustic metasurface with V-shape structure

    Science.gov (United States)

    Lan, Jun; Li, Yifeng; Liu, Xiaozhou

    2017-12-01

    We present a space folding acoustic metasurface with a V-shaped structure, which exhibits ultra-broadband and high efficiency transmission compared to previously investigated space folding metasurfaces. The proposal employs a gradient refractive index profile to redirect the refracted wave arbitrarily and an existence of air channels with direct sound propagation to improve impedance matching between the metasurface and the background medium. As expected from frequency-independent generalized Snell's law, the demonstrated acoustic metasurface can steer refracted wavefronts at will, including anomalous refraction, non-diffracting Bessel beam, sub-wavelength flat lens, and conversion of the propagating wave into the surface wave. The designed V-shape metasurface overcomes the limitation of narrowband, which may offer potential applications in medical ultrasound imaging and broadband acoustical devices.

  14. Broadband Two-Photon Absorption Characteristics of Highly Photostable Fluorenyl-Dicyanoethylenylated [60]Fullerene Dyads

    Directory of Open Access Journals (Sweden)

    Seaho Jeon

    2016-05-01

    Full Text Available We synthesized four C60-(light-harvesting antenna dyads C60 (>CPAF-Cn (n = 4, 9, 12, or 18 1-Cn for the investigation of their broadband nonlinear absorption effect. Since we have previously demonstrated their high function as two-photon absorption (2PA materials at 1000 nm, a different 2PA wavelength of 780 nm was applied in the study. The combined data taken at two different wavelength ranges substantiated the broadband characteristics of 1-Cn. We proposed that the observed broadband absorptions may be attributed by a partial π-conjugation between the C60 > cage and CPAF-Cn moieties, via endinitrile tautomeric resonance, giving a resonance state with enhanced molecular conjugation. This transient state could increase its 2PA and excited-state absorption at 800 nm. In addition, a trend of concentration-dependent 2PA cross-section (σ2 and excited-state absorption magnitude was detected showing a higher σ value at a lower concentration that was correlated to increasing molecular separation with less aggregation for dyads C60(>CPAF-C18 and C60(>CPAF-C9, as better 2PA and excited-state absorbers.

  15. Calibration of High Frequency MEMS Microphones

    Science.gov (United States)

    Shams, Qamar A.; Humphreys, William M.; Bartram, Scott M.; Zuckewar, Allan J.

    2007-01-01

    Understanding and controlling aircraft noise is one of the major research topics of the NASA Fundamental Aeronautics Program. One of the measurement technologies used to acquire noise data is the microphone directional array (DA). Traditional direction array hardware, consisting of commercially available condenser microphones and preamplifiers can be too expensive and their installation in hard-walled wind tunnel test sections too complicated. An emerging micro-machining technology coupled with the latest cutting edge technologies for smaller and faster systems have opened the way for development of MEMS microphones. The MEMS microphone devices are available in the market but suffer from certain important shortcomings. Based on early experiments with array prototypes, it has been found that both the bandwidth and the sound pressure level dynamic range of the microphones should be increased significantly to improve the performance and flexibility of the overall array. Thus, in collaboration with an outside MEMS design vendor, NASA Langley modified commercially available MEMS microphone as shown in Figure 1 to meet the new requirements. Coupled with the design of the enhanced MEMS microphones was the development of a new calibration method for simultaneously obtaining the sensitivity and phase response of the devices over their entire broadband frequency range. Over the years, several methods have been used for microphone calibration. Some of the common methods of microphone calibration are Coupler (Reciprocity, Substitution, and Simultaneous), Pistonphone, Electrostatic actuator, and Free-field calibration (Reciprocity, Substitution, and Simultaneous). Traditionally, electrostatic actuators (EA) have been used to characterize air-condenser microphones for wideband frequency ranges; however, MEMS microphones are not adaptable to the EA method due to their construction and very small diaphragm size. Hence a substitution-based, free-field method was developed to

  16. Small Displacement Detection of Biological Signals Using the Cyclic Frequency Method

    Directory of Open Access Journals (Sweden)

    Dan Zhang

    2015-01-01

    Full Text Available A new signal processing method called the Cyclic Frequency method is proposed for small displacement detection of vital signals such as heart rate and respiration using the CW radar method. We have presented experimental results of small displacement detection to confirm the validity of the method. The displacement amplitude 2.5 mm can be detected with a propagation frequency of 24.15 GHz. We may increase the propagation frequency for smaller displacement amplitude or target velocity.

  17. System and method for earth probing with deep subsurface penetration using low frequency electromagnetic signals

    International Nuclear Information System (INIS)

    Etten, P. van; Brown, R.D.

    1996-01-01

    An earth probing system uses deep penetration of electromagnetic waves into soil and other media. Advantage is taken of lower attenuation of radar in soil by frequencies of about three megahertz or less. Bursts of electromagnetic energy of various frequencies in this range are consecutively transmitted. The transmitting antenna is continuously tuned, so as to maintain resonance during each burst, allowing large circulating currents and high power output. In a receiving antenna system, a dual antenna arrangement is providing for obtaining improved reception. A corresponding dual antenna circuit employs 'a spatial notch filtering', automatic adjustment of antenna gain-frequency variations, as well as compensation for transmitter gain variation. The system may be implemented in a totally analog, totally digital, or hybrid manner. Preferably, a signal processing method detected and digitally samples signal reflected from subsurface layers and buried objects. The invention provides means for removing system distortions and interfering signals, for compensating for aliasing errors and frequency-dependent antenna gain and phase variations, and for avoiding masking errors introduced by strong reflections. (author)

  18. Nonlinear Analysis of Renal Autoregulation Under Broadband Forcing Conditions

    DEFF Research Database (Denmark)

    Marmarelis, V Z; Chon, K H; Chen, Y M

    1994-01-01

    Linear analysis of renal blood flow fluctuations, induced experimentally in rats by broad-band (pseudorandom) arterial blood pressure forcing at various power levels, has been unable to explain fully the dynamics of renal autoregulation at low frequencies. This observation has suggested...... the possibility of nonlinear mechanisms subserving renal autoregulation at frequencies below 0.2 Hz. This paper presents results of 3rd-order Volterra-Wiener analysis that appear to explain adequately the nonlinearities in the pressure-flow relation below 0.2 Hz in rats. The contribution of the 3rd-order kernel...... in describing the dynamic pressure-flow relation is found to be important. Furthermore, the dependence of 1st-order kernel waveforms on the power level of broadband pressure forcing indicates the presence of nonlinear feedback (of sigmoid type) based on previously reported analysis of a class of nonlinear...

  19. Quantum frequency conversion with ultra-broadband tuning in a Raman memory

    Science.gov (United States)

    Bustard, Philip J.; England, Duncan G.; Heshami, Khabat; Kupchak, Connor; Sussman, Benjamin J.

    2017-05-01

    Quantum frequency conversion is a powerful tool for the construction of hybrid quantum photonic technologies. Raman quantum memories are a promising method of conversion due to their broad bandwidths. Here we demonstrate frequency conversion of THz-bandwidth, fs-duration photons at the single-photon level using a Raman quantum memory based on the rotational levels of hydrogen molecules. We shift photons from 765 nm to wavelengths spanning from 673 to 590 nm—an absolute shift of up to 116 THz. We measure total conversion efficiencies of up to 10% and a maximum signal-to-noise ratio of 4.0(1):1, giving an expected conditional fidelity of 0.75, which exceeds the classical threshold of 2/3. Thermal noise could be eliminated by cooling with liquid nitrogen, giving noiseless conversion with wide tunability in the visible and infrared.

  20. Silicon Micromachined Sensor for Broadband Vibration Analysis

    Science.gov (United States)

    Gutierrez, Adolfo; Edmans, Daniel; Cormeau, Chris; Seidler, Gernot; Deangelis, Dave; Maby, Edward

    1995-01-01

    The development of a family of silicon based integrated vibration sensors capable of sensing mechanical resonances over a broad range of frequencies with minimal signal processing requirements is presented. Two basic general embodiments of the concept were designed and fabricated. The first design was structured around an array of cantilever beams and fabricated using the ARPA sponsored multi-user MEMS processing system (MUMPS) process at the Microelectronics Center of North Carolina (MCNC). As part of the design process for this first sensor, a comprehensive finite elements analysis of the resonant modes and stress distribution was performed using PATRAN. The dependence of strain distribution and resonant frequency response as a function of Young's modulus in the Poly-Si structural material was studied. Analytical models were also studied. In-house experimental characterization using optical interferometry techniques were performed under controlled low pressure conditions. A second design, intended to operate in a non-resonant mode and capable of broadband frequency response, was proposed and developed around the concept of a cantilever beam integrated with a feedback control loop to produce a null mode vibration sensor. A proprietary process was used to integrat a metal-oxide semiconductor (MOS) sensing device, with actuators and a cantilever beam, as part of a compatible process. Both devices, once incorporated as part of multifunction data acquisition and telemetry systems will constitute a useful system for NASA launch vibration monitoring operations. Satellite and other space structures can benefit from the sensor for mechanical condition monitoring functions.

  1. Broadband electrical impedance matching for piezoelectric ultrasound transducers.

    Science.gov (United States)

    Huang, Haiying; Paramo, Daniel

    2011-12-01

    This paper presents a systematic method for designing broadband electrical impedance matching networks for piezoelectric ultrasound transducers. The design process involves three steps: 1) determine the equivalent circuit of the unmatched piezoelectric transducer based on its measured admittance; 2) design a set of impedance matching networks using a computerized Smith chart; and 3) establish the simulation model of the matched transducer to evaluate the gain and bandwidth of the impedance matching networks. The effectiveness of the presented approach is demonstrated through the design, implementation, and characterization of impedance matching networks for a broadband acoustic emission sensor. The impedance matching network improved the power of the acquired signal by 9 times.

  2. Spatial-temporal dynamics of broadband terahertz Bessel beam propagation

    International Nuclear Information System (INIS)

    Semenova, V A; Kulya, M S; Bespalov, V G

    2016-01-01

    The unique properties of narrowband and broadband terahertz Bessel beams have led to a number of their applications in different fields, for example, for the depth of focusing and resolution enhancement in terahertz imaging. However, broadband terahertz Bessel beams can probably be also used for the diffraction minimization in the short-range broadband terahertz communications. For this purpose, the study of spatial-temporal dynamics of the broadband terahertz Bessel beams is needed. Here we present a simulation-based study of the propagating in non-dispersive medium broadband Bessel beams generated by a conical axicon lens. The algorithm based on scalar diffraction theory was used to obtain the spatial amplitude and phase distributions of the Bessel beam in the frequency range from 0.1 to 3 THz at the distances 10-200 mm from the axicon. Bessel beam field is studied for the different spectral components of the initial pulse. The simulation results show that for the given parameters of the axicon lens one can obtain the Gauss-Bessel beam generation in the spectral range from 0.1 to 3 THz. The length of non-diffraction propagation for a different spectral components was measured, and it was shown that for all spectral components of the initial pulse this length is about 130 mm. (paper)

  3. Narrowband pulse-enhanced upconversion of chirped broadband pulses

    International Nuclear Information System (INIS)

    Zhao, Kun; Yuan, Peng; Zhong, Haizhe; Zhang, Dongfang; Zhu, Heyuan; Qian, Liejia; Chen, Liezun; Wen, Shuangchun

    2010-01-01

    We propose and demonstrate an efficient sum-frequency mixing scheme based on narrowband and chirped broadband pulses. It combines the advantages of wider spectral acceptance bandwidth and of alleviating the temporal walk-off, which are both beneficial to higher conversion efficiency. Chirped sum-frequency pulses at 455 nm with energy up to 360 µJ, corresponding to a conversion efficiency of ∼ 40%, are obtained and the pulses can be compressed to ∼ 110 fs. The sum-frequency mixing scheme may provide a promising route to the efficient generation of deep-ultraviolet femtosecond pulses

  4. Advanced spectral processing of broadband light using acousto-optic devices with arbitrary transmission functions.

    Science.gov (United States)

    Molchanov, Vladimir Ya; Yushkov, Konstantin B

    2014-06-30

    In the paper, we developed a dispersive method for transmission function synthesis of collinear and quasi-collinear acousto-optic tunable filters. General theoretical consideration was performed, and modelling was made for broadband and narrowband signals. Experimental results on spectral shaping of femtosecond laser emission were obtained. Binary spectral encoding of broadband emission was demonstrated.

  5. Record power, ultra-broadband supercontinuum source based on highly GeO2 doped silica fiber

    DEFF Research Database (Denmark)

    Jain, Deepak; Sidharthan, R.; Moselund, Peter M.

    2016-01-01

    the potential of germania based photonic crystal fiber or a step-index fiber supercontinuum source for high power ultra-broad band emission being by pumped a 1060 nm or a 1550 nm laser source. To the best of our knowledge, this is the record power, ultra-broadband, and all-fiberized supercontinuum light source...... based on silica and germania fiber ever demonstrated to the date. (C) 2016 Optical Society of America......We demonstrate highly germania doped fibers for mid-infrared supercontinuum generation. Experiments ensure a highest output power of 1.44 W for a broadest spectrum from 700 nm to 3200 nm and 6.4 W for 800 nm to 2700 nm from these fibers, while being pumped by a broadband Erbium-Ytterbium doped...

  6. Sync transmission method and apparatus for high frequency pulsed neutron spectral analysis systems

    International Nuclear Information System (INIS)

    Culver, R.B.

    1981-01-01

    An improved synchronization system was developed for high-frequency pulsed-neutron gamma ray well-logging which extends the upper limit of the usable source pulsing frequency. A clock is used to pulse the neutron generator at a given frequency and a scaler generates scaled-down sync pulses at a lower frequency. Radiation from the formations surrounding the borehole is detected and electrical signals related functionally to the radiation are generated. The scaled-down sync pulses and electrical signals are transmitted to the earth's surface via a seven conductor well logging cable. (DN)

  7. Study on electrical impedance matching for broadband ultrasonic transducer

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Geon Woo [University of Science and Technology, Daejeon (Korea, Republic of); Kim, Ki Bok [Korea Research Institute of Standards and Science, Center for Safety Measurement, Daejeon (Korea, Republic of); Baek, Kwang Sae [Elache Co., Busan (Korea, Republic of)

    2017-02-15

    Ultrasonic transducers with high resolution and resonant frequency are required to detect small defects (less than hundreds of μm) by ultrasonic testing. The resonance frequency and resolution of an ultrasonic transducer are closely related to the thickness of piezo-electric materials, backing materials, and the electric impedance matching technique. Among these factors, electrical impedance matching plays an important role because it can reduce the loss and reflection of ultrasonic energy differences in electrical impedance between an ultrasonic transducer and an ultrasonic defects detecting system. An LC matching circuit is the most frequently used electric matching method. It is necessary for the electrical impedance of an ultrasonic transducer to correspond to approximately 50 Ω to compensate the difference in electrical impedance between both connections. In this study, a 15 MHz immersion ultrasonic transducer was fabricated and an LC electrical impedance circuit was applied to that for having broad-band frequency characteristic.

  8. Application on technique of joint time-frequency analysis of seismic signal's first arrival estimation

    International Nuclear Information System (INIS)

    Xu Chaoyang; Liu Junmin; Fan Yanfang; Ji Guohua

    2008-01-01

    Joint time-frequency analysis is conducted to construct one joint density function of time and frequency. It can open out one signal's frequency components and their evolvements. It is the new evolvement of Fourier analysis. In this paper, according to the characteristic of seismic signal's noise, one estimation method of seismic signal's first arrival based on triple correlation of joint time-frequency spectrum is introduced, and the results of experiment and conclusion are presented. (authors)

  9. High Order Differential Frequency Hopping: Design and Analysis

    Directory of Open Access Journals (Sweden)

    Yong Li

    2015-01-01

    Full Text Available This paper considers spectrally efficient differential frequency hopping (DFH system design. Relying on time-frequency diversity over large spectrum and high speed frequency hopping, DFH systems are robust against hostile jamming interference. However, the spectral efficiency of conventional DFH systems is very low due to only using the frequency of each channel. To improve the system capacity, in this paper, we propose an innovative high order differential frequency hopping (HODFH scheme. Unlike in traditional DFH where the message is carried by the frequency relationship between the adjacent hops using one order differential coding, in HODFH, the message is carried by the frequency and phase relationship using two-order or higher order differential coding. As a result, system efficiency is increased significantly since the additional information transmission is achieved by the higher order differential coding at no extra cost on either bandwidth or power. Quantitative performance analysis on the proposed scheme demonstrates that transmission through the frequency and phase relationship using two-order or higher order differential coding essentially introduces another dimension to the signal space, and the corresponding coding gain can increase the system efficiency.

  10. Broad-band simulation of M7.2 earthquake on the North Tehran fault, considering non-linear soil effects

    Science.gov (United States)

    Majidinejad, A.; Zafarani, H.; Vahdani, S.

    2018-05-01

    The North Tehran fault (NTF) is known to be one of the most drastic sources of seismic hazard on the city of Tehran. In this study, we provide broad-band (0-10 Hz) ground motions for the city as a consequence of probable M7.2 earthquake on the NTF. Low-frequency motions (0-2 Hz) are provided from spectral element dynamic simulation of 17 scenario models. High-frequency (2-10 Hz) motions are calculated with a physics-based method based on S-to-S backscattering theory. Broad-band ground motions at the bedrock level show amplifications, both at low and high frequencies, due to the existence of deep Tehran basin in the vicinity of the NTF. By employing soil profiles obtained from regional studies, effect of shallow soil layers on broad-band ground motions is investigated by both linear and non-linear analyses. While linear soil response overestimate ground motion prediction equations, non-linear response predicts plausible results within one standard deviation of empirical relationships. Average Peak Ground Accelerations (PGAs) at the northern, central and southern parts of the city are estimated about 0.93, 0.59 and 0.4 g, respectively. Increased damping caused by non-linear soil behaviour, reduces the soil linear responses considerably, in particular at frequencies above 3 Hz. Non-linear deamplification reduces linear spectral accelerations up to 63 per cent at stations above soft thick sediments. By performing more general analyses, which exclude source-to-site effects on stations, a correction function is proposed for typical site classes of Tehran. Parameters for the function which reduces linear soil response in order to take into account non-linear soil deamplification are provided for various frequencies in the range of engineering interest. In addition to fully non-linear analyses, equivalent-linear calculations were also conducted which their comparison revealed appropriateness of the method for large peaks and low frequencies, but its shortage for small to

  11. A broadband two axis flux-gate magnetometer

    Directory of Open Access Journals (Sweden)

    P. Palangio

    1998-06-01

    Full Text Available A broadband two axis flux-gate magnetometer was developed to obtain high sensitivity in magnetotelluric measurements. In magnetotelluric sounding, natural low frequency electromagnetic fields are used to estimate the conductivity of the Earth's interior. Because variations in the natural magnetic field have small amplitude(10-100 pT in the frequency range 1 Hz to 100 Hz, highly sensitive magnetic sensors are required. In magnetotelluric measurements two long and heavy solenoids, which must be installed, in the field station, perpendicular to each other (north-south and east-west and levelled in the horizontal plane are used. The coil is a critical component in magnetotelluric measurements because very slight motions create noise voltages, particularly troublesome in wooded areas; generally the installation takes place in a shallow trench. Moreover the coil records the derivative of the variations rather than the magnetic field variations, consequently the transfer function (amplitude and phase of this sensor is not constant throughout the frequency range 0.001-100 Hz. The instrument, developed at L'Aquila Geomagnetic Observatory, has a flat response in both amplitude and phase in the frequency band DC-100 Hz, in addition it has low weight, low power, small volume and it is easier to install in the field than induction magnetometers. The sensivity of this magnetometer is 10 pT rms.

  12. Broadband illusion optical devices based on conformal mappings

    Science.gov (United States)

    Xiong, Zhan; Xu, Lin; Xu, Ya-Dong; Chen, Huan-Yang

    2017-10-01

    In this paper, we propose a simple method of illusion optics based on conformal mappings. By carefully developing designs with specific conformal mappings, one can make an object look like another with a significantly different shape. In addition, the illusion optical devices can work in a broadband of frequencies.

  13. A compact broadband high efficient X-band 9-watt PHEMT MMIC high-power amplifier for phased array radar applications

    NARCIS (Netherlands)

    Hek, A.P. de; Hunneman, P.A.H.; Demmler, M.; Hulsmann, A.

    1999-01-01

    ln this paper the development and measurement results of a compact broadband 9-Watt high efficient X-band high-power amplifier are discussed. The described amplifier has the following state-of-the art performance: an average ouput power of 9 Watt, a gain of 20 dB and an average Power Added

  14. Boxcar detection for high-frequency modulation in stimulated Raman scattering microscopy

    Science.gov (United States)

    Fimpel, P.; Riek, C.; Ebner, L.; Leitenstorfer, A.; Brida, D.; Zumbusch, A.

    2018-04-01

    Stimulated Raman scattering (SRS) microscopy is an important non-linear optical technique for the investigation of unlabeled samples. The SRS signal manifests itself as a small intensity exchange between the laser pulses involved in coherent excitation of Raman modes. Usually, high-frequency modulation is applied in one pulse train, and the signal is then detected on the other pulse train via lock-in amplification. While allowing shot-noise limited detection sensitivity, lock-in detection, which corresponds to filtering the signal in the frequency domain, is not the most efficient way of using the excitation light. In this manuscript, we show that boxcar averaging, which is equivalent to temporal filtering, is better suited for the detection of low-duty-cycle signals as encountered in SRS microscopy. We demonstrate that by employing suitable gating windows, the signal-to-noise ratios achievable with lock-in detection can be realized in shorter time with boxcar averaging. Therefore, high-quality images are recorded at a faster rate and lower irradiance which is an important factor, e.g., for minimizing degradation of biological samples.

  15. Fiber optics frequency comb enabled linear optical sampling with operation wavelength range extension.

    Science.gov (United States)

    Liao, Ruolin; Wu, Zhichao; Fu, Songnian; Zhu, Shengnan; Yu, Zhe; Tang, Ming; Liu, Deming

    2018-02-01

    Although the linear optical sampling (LOS) technique is powerful enough to characterize various advanced modulation formats with high symbol rates, the central wavelength of a pulsed local oscillator (LO) needs to be carefully set according to that of the signal under test, due to the coherent mixing operation. Here, we experimentally demonstrate wideband LOS enabled by a fiber optics frequency comb (FOFC). Meanwhile, when the broadband FOFC acts as the pulsed LO, we propose a scheme to mitigate the enhanced sampling error arising in the non-ideal response of a balanced photodetector. Finally, precise characterizations of arbitrary 128 Gbps PDM-QPSK wavelength channels from 1550 to 1570 nm are successfully achieved, when a 101.3 MHz frequency spaced comb with a 3 dB spectral power ripple of 20 nm is used.

  16. Test the mergers of the primordial black holes by high frequency gravitational-wave detector

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xin; Wang, Li-Li; Li, Jin [Chongqing University, Department of Physics, Chongqing (China)

    2017-09-15

    The black hole could have a primordial origin if its mass is less than 1M {sub CircleDot}. The mergers of these black hole binaries generate stochastic gravitational-wave background (SGWB). We investigate the SGWB in high frequency band 10{sup 8}-10{sup 10} Hz. It can be detected by high frequency gravitational-wave detector. Energy density spectrum and amplitude of the SGWB are derived. The upper limit of the energy density spectrum is around 10{sup -7}. Also, the upper limit of the amplitude ranges from 10{sup -31.5} to 10{sup -29.5}. The fluctuation of spacetime origin from gravitational wave could give a fluctuation of the background electromagnetic field in a high frequency gravitational-wave detector. The signal photon flux generated by the SGWB in the high frequency band 10{sup 8}-10{sup 10} Hz is derived, which ranges from 1 to 10{sup 2} s{sup -1}. The comparison between the signal photon flux generated by relic gravitational waves (RGWs) and the SGWB is also discussed in this paper. It is shown that the signal photon flux generated by the RGW, which is predicted by the canonical single-field slow-roll inflation models, is sufficiently lower than the one generated by the SGWB in the high frequency band 10{sup 8}-10{sup 10} Hz. Our results indicate that the SGWB in the high frequency band 10{sup 8}-10{sup 10} Hz is more likely to be detected by the high frequency gravitational-wave detector. (orig.)

  17. Signal Conditioning in Process of High Speed Imaging

    Directory of Open Access Journals (Sweden)

    Libor Hargas

    2015-01-01

    Full Text Available The accuracy of cinematic analysis with camera system depends on frame rate of used camera. Specific case of cinematic analysis is in medical research focusing on microscopic objects moving with high frequencies (cilia of respiratory epithelium. The signal acquired by high speed video acquisition system has very amount of data. This paper describes hardware parts, signal condition and software, which is used for image acquiring thru digital camera, intelligent illumination dimming hardware control and ROI statistic creation. All software parts are realized as virtual instruments.

  18. The thermal history of the plasma and high-frequency gravitons

    International Nuclear Information System (INIS)

    Giovannini, Massimo

    2009-01-01

    Possible deviations from a radiation-dominated evolution, occurring prior to the synthesis of light nuclei, impacted on the spectral energy density of high-frequency gravitons. For a systematic scrutiny of this situation, the ΛCDM paradigm must be complemented by (at least two) physical parameters describing, respectively, a threshold frequency and a slope. The supplementary frequency scale sets the lower border of a high-frequency domain where the spectral energy grows with a slope which depends, predominantly, upon the total sound speed of the plasma right after inflation. While the infrared region of the graviton energy spectrum is nearly scale invariant, the expected signals for typical frequencies larger than 0.01 nHz are hereby analyzed in a model-independent framework by requiring that the total sound speed of the post-inflationary plasma be smaller than the speed of light. Current (e.g., low-frequency) upper limits on the tensor power spectra (determined from the combined analysis of the three large-scale data sets) are shown to be compatible with a detectable signal in the frequency range of wideband interferometers. In the present context, the scrutiny of the early evolution of the sound speed of the plasma can then be mapped onto a reliable strategy of parameter extraction including not only the well-established cosmological observables but also the forthcoming data from wideband interferometers.

  19. An ultra-broadband multilayered graphene absorber

    KAUST Repository

    Amin, Muhammad

    2013-01-01

    An ultra-broadband multilayered graphene absorber operating at terahertz (THz) frequencies is proposed. The absorber design makes use of three mechanisms: (i) The graphene layers are asymmetrically patterned to support higher order surface plasmon modes that destructively interfere with the dipolar mode and generate electromagnetically induced absorption. (ii) The patterned graphene layers biased at different gate voltages backedup with dielectric substrates are stacked on top of each other. The resulting absorber is polarization dependent but has an ultra-broadband of operation. (iii) Graphene\\'s damping factor is increased by lowering its electron mobility to 1000cm 2=Vs. Indeed, numerical experiments demonstrate that with only three layers, bandwidth of 90% absorption can be extended upto 7THz, which is drastically larger than only few THz of bandwidth that can be achieved with existing metallic/graphene absorbers. © 2013 Optical Society of America.

  20. Perceptual Coding of Audio Signals Using Adaptive Time-Frequency Transform

    Directory of Open Access Journals (Sweden)

    Umapathy Karthikeyan

    2007-01-01

    Full Text Available Wide band digital audio signals have a very high data-rate associated with them due to their complex nature and demand for high-quality reproduction. Although recent technological advancements have significantly reduced the cost of bandwidth and miniaturized storage facilities, the rapid increase in the volume of digital audio content constantly compels the need for better compression algorithms. Over the years various perceptually lossless compression techniques have been introduced, and transform-based compression techniques have made a significant impact in recent years. In this paper, we propose one such transform-based compression technique, where the joint time-frequency (TF properties of the nonstationary nature of the audio signals were exploited in creating a compact energy representation of the signal in fewer coefficients. The decomposition coefficients were processed and perceptually filtered to retain only the relevant coefficients. Perceptual filtering (psychoacoustics was applied in a novel way by analyzing and performing TF specific psychoacoustics experiments. An added advantage of the proposed technique is that, due to its signal adaptive nature, it does not need predetermined segmentation of audio signals for processing. Eight stereo audio signal samples of different varieties were used in the study. Subjective (mean opinion score—MOS listening tests were performed and the subjective difference grades (SDG were used to compare the performance of the proposed coder with MP3, AAC, and HE-AAC encoders. Compression ratios in the range of 8 to 40 were achieved by the proposed technique with subjective difference grades (SDG ranging from –0.53 to –2.27.

  1. Experimental Investigation on Propagation Characteristics of PD Radiated UHF Signal in Actual 252 kV GIS

    Directory of Open Access Journals (Sweden)

    Tianhui Li

    2017-07-01

    Full Text Available For partial discharge (PD diagnostics in gas insulated switchgears (GISs based on the ultra-high-frequency (UHF method, it is essential to study the attenuation characteristics of UHF signals so as to improve the application of the UHF technique. Currently, the performance of UHF has not been adequately considered in most experimental research, while the constructive conclusions about the installation and position of UHF sensors are relatively rare. In this research, by using a previously-designed broadband sensor, the output signal is detected and analyzed experimentally in a 252 kV GIS with L-shaped structure and disconnecting switch. Since the relative position of the sensor and the defect is usually fixed by prior research, three circumferential angle positions of the defect in cross section are performed. The results are studied by time, statistics and frequency analyses. This identifies that the discontinuity conductor of DS will lead to a rise of both the peak to peak value (Vpp and the transmission rate of the UHF signal. Then, the frequency analysis indicates that the reason for the distinction of signal amplitude and transmission rate is that the mode components of the PD signal are distinctively affected by the special structure of GIS. Finally, the optimal circumferential angle position of the UHF Sensor is given based on the comparison of transmission rates.

  2. Fundamental Frequency and Direction-of-Arrival Estimation for Multichannel Speech Enhancement

    DEFF Research Database (Denmark)

    Karimian-Azari, Sam

    Audio systems receive the speech signals of interest usually in the presence of noise. The noise has profound impacts on the quality and intelligibility of the speech signals, and it is therefore clear that the noisy signals must be cleaned up before being played back, stored, or analyzed. We can...... estimate the speech signal of interest from the noisy signals using a priori knowledge about it. A human speech signal is broadband and consists of both voiced and unvoiced parts. The voiced part is quasi-periodic with a time-varying fundamental frequency (or pitch as it is commonly referred to). We...... their time differences which eventually may further reduce the effects of noise. This thesis introduces a number of principles and methods to estimate periodic signals in noisy environments with application to multichannel speech enhancement. We propose model-based signal enhancement concerning the model...

  3. Improving mental task classification by adding high frequency band information.

    Science.gov (United States)

    Zhang, Li; He, Wei; He, Chuanhong; Wang, Ping

    2010-02-01

    Features extracted from delta, theta, alpha, beta and gamma bands spanning low frequency range are commonly used to classify scalp-recorded electroencephalogram (EEG) for designing brain-computer interface (BCI) and higher frequencies are often neglected as noise. In this paper, we implemented an experimental validation to demonstrate that high frequency components could provide helpful information for improving the performance of the mental task based BCI. Electromyography (EMG) and electrooculography (EOG) artifacts were removed by using blind source separation (BSS) techniques. Frequency band powers and asymmetry ratios from the high frequency band (40-100 Hz) together with those from the lower frequency bands were used to represent EEG features. Finally, Fisher discriminant analysis (FDA) combining with Mahalanobis distance were used as the classifier. In this study, four types of classifications were performed using EEG signals recorded from four subjects during five mental tasks. We obtained significantly higher classification accuracy by adding the high frequency band features compared to using the low frequency bands alone, which demonstrated that the information in high frequency components from scalp-recorded EEG is valuable for the mental task based BCI.

  4. Fiber lightguide-coupled high frequency analog data system

    International Nuclear Information System (INIS)

    Davies, T.J.; Nelson, M.A.; Morton, J.R.; Pruett, B.

    1976-06-01

    An experimental system is described for measuring the time history of a high voltage, high frequency electrical pulse from a radiation detector. The system employs several fibers of a 500-m graded index light-guide cable to carry modelocked laser pulses from a safe location to an electro-optical Kerr cell located near the detector. These 200-ps pulses are widened to 500 ps at the cell by fiber dispersion. They are intensity-modulated in the cell by the electrical signal and returned over other cable fibers to an optical detector and recorder located near the laser. System frequency response exceeds 500 MHz over an amplitude dynamic range of 1000:1

  5. High-resolution mid-IR spectrometer based on frequency upconversion

    DEFF Research Database (Denmark)

    Hu, Qi; Dam, Jeppe Seidelin; Pedersen, Christian

    2012-01-01

    We demonstrate a novel approach for high-resolution spectroscopy based on frequency upconversion and postfiltering by means of a scanning Fabryx2013;Perot interferometer. The system is based on sum-frequency mixing, shifting the spectral content from the mid-infrared to the near-visible region al......-frequency 1064xA0;nm laser. We investigate water vapor emission lines from a butane burner and compare the measured results to model data. The presented method we suggest to be used for real-time monitoring of specific gas lines and reference signals....

  6. High frequency vibration analysis by the complex envelope vectorization.

    Science.gov (United States)

    Giannini, O; Carcaterra, A; Sestieri, A

    2007-06-01

    The complex envelope displacement analysis (CEDA) is a procedure to solve high frequency vibration and vibro-acoustic problems, providing the envelope of the physical solution. CEDA is based on a variable transformation mapping the high frequency oscillations into signals of low frequency content and has been successfully applied to one-dimensional systems. However, the extension to plates and vibro-acoustic fields met serious difficulties so that a general revision of the theory was carried out, leading finally to a new method, the complex envelope vectorization (CEV). In this paper the CEV method is described, underlying merits and limits of the procedure, and a set of applications to vibration and vibro-acoustic problems of increasing complexity are presented.

  7. A simple-architecture fibered transmission system for dissemination of high stability 100 MHz signals

    Science.gov (United States)

    Bakir, A.; Rocher, C.; Maréchal, B.; Bigler, E.; Boudot, R.; Kersalé, Y.; Millo, J.

    2018-05-01

    We report on the development of a simple-architecture fiber-based frequency distribution system used to transfer high frequency stability 100 MHz signals. This work is focused on the emitter and the receiver performances that allow the transmission of the radio-frequency signal over an optical fiber. The system exhibits a residual fractional frequency stability of 1 × 10-14 at 1 s integration time and in the low 10-16 range after 100 s. These performances are suitable to transfer the signal of frequency references such as those of a state-of-the-art hydrogen maser without any phase noise compensation scheme. As an application, we demonstrate the dissemination of such a signal through a 100 m long optical fiber without any degradation. The proposed setup could be easily extended for operating frequencies in the 10 MHz-1 GHz range.

  8. Optical broadband in-home networks for converged service delivery

    NARCIS (Netherlands)

    Shi, Y.

    2013-01-01

    Broadband access networks, and in particular fibre-to-the-home (FTTH) networks, are offering abundantly available bandwidth in the local loop with high quality of services. Under such broadband connectivity conditions, in-home networks should not represent the bottleneck for high capacity service

  9. High-performance broad-band spectroscopy for breast cancer risk assessment

    Science.gov (United States)

    Pawluczyk, Olga; Blackmore, Kristina; Dick, Samantha; Lilge, Lothar

    2005-09-01

    Medical diagnostics and screening are becoming increasingly demanding applications for spectroscopy. Although for many years the demand was satisfied with traditional spectrometers, analysis of complex biological samples has created a need for instruments capable of detecting small differences between samples. One such application is the measurement of absorbance of broad spectrum illumination by breast tissue, in order to quantify the breast tissue density. Studies have shown that breast cancer risk is closely associated with the measurement of radiographic breast density measurement. Using signal attenuation in transillumination spectroscopy in the 550-1100nm spectral range to measure breast density, has the potential to reduce the frequency of ionizing radiation, or making the test accessible to younger women; lower the cost and make the procedure more comfortable for the patient. In order to determine breast density, small spectral variances over a total attenuation of up to 8 OD have to be detected with the spectrophotometer. For this, a high performance system has been developed. The system uses Volume Phase Holographic (VPH) transmission grating, a 2D detector array for simultaneous registration of the whole spectrum with high signal to noise ratio, dedicated optical system specifically optimized for spectroscopic applications and many other improvements. The signal to noise ratio exceeding 50,000 for a single data acquisition eliminates the need for nitrogen cooled detectors and provides sufficient information to predict breast tissue density. Current studies employing transillumination breast spectroscopy (TIBS) relating to breast cancer risk assessment and monitoring are described.

  10. Thermal history of the plasma and high-frequency gravitons

    CERN Document Server

    Giovannini, Massimo

    2009-01-01

    Possible deviations from a radiation-dominated evolution, occurring prior the synthesis of light nuclei, impacted on the spectral energy density of high-frequency gravitons. For a systematic scrutiny of this situation, the $\\Lambda$CDM paradigm must be complemented by (at least two) physical parameters describing, respectively, a threshold frequency and a slope. The supplementary frequency scale sets the lower border of a high-frequency domain where the spectral energy grows with a slope which depends, predominantly, upon the total sound speed of the plasma right after inflation. While the infra-red region of the graviton energy spectrum is nearly scale-invariant, the expected signals for typical frequencies larger than 0.01 nHz are hereby analyzed in a model-independent framework by requiring that the total sound speed of the post-inflationary plasma is smaller than the speed of light. Current (e.g. low-frequency) upper limits on the tensor power spectra (determined from the combined analysis of the three la...

  11. Broadband manipulation of acoustic wavefronts by pentamode metasurface

    International Nuclear Information System (INIS)

    Tian, Ye; Wei, Qi; Cheng, Ying; Xu, Zheng; Liu, Xiaojun

    2015-01-01

    An acoustic metasurface with a sub-wavelength thickness can manipulate acoustic wavefronts freely by the introduction of abrupt phase variation. However, the existence of a narrow bandwidth and a low transmittance limits further applications. Here, we present a broadband and highly transparent acoustic metasurface based on a frequency-independent generalized acoustic Snell's law and pentamode metamaterials. The proposal employs a gradient velocity to redirect refracted waves and pentamode metamaterials to improve impedance matching between the metasurface and the background medium. Excellent wavefront manipulation based on the metasurface is further demonstrated by anomalous refraction, generation of non-diffracting Bessel beam, and sub-wavelength flat focusing

  12. Plate-type metamaterials for extremely broadband low-frequency sound insulation

    Science.gov (United States)

    Wang, Xiaopeng; Guo, Xinwei; Chen, Tianning; Yao, Ge

    2018-01-01

    A novel plate-type acoustic metamaterial with a high sound transmission loss (STL) in the low-frequency range ( ≤1000 Hz) is designed, theoretically proven and then experimentally verified. The thin plates with large modulus used in this paper mean that we do not need to apply tension to the plates, which is more applicable to practical engineering, the achievement of noise reduction is better and the installation of plates is more user-friendly than that of the membranes. The effects of different structural parameters of the plates on the sound-proofed performance at low-frequencies were also investigated by experiment and finite element method (FEM). The results showed that the STL can be modulated effectively and predictably using vibration theory by changing the structural parameters, such as the radius and thickness of the plate. Furthermore, using unit cells of different geometric sizes which are responsible for different frequency regions, the stacked panels with thickness ≤16 mm and weight ≤5 kg/m2 showed high STL below 2000 Hz. The acoustic metamaterial proposed in this study could provide a potential application in the low-frequency noise insulation.

  13. Parametric nanomechanical amplification at very high frequency.

    Science.gov (United States)

    Karabalin, R B; Feng, X L; Roukes, M L

    2009-09-01

    Parametric resonance and amplification are important in both fundamental physics and technological applications. Here we report very high frequency (VHF) parametric resonators and mechanical-domain amplifiers based on nanoelectromechanical systems (NEMS). Compound mechanical nanostructures patterned by multilayer, top-down nanofabrication are read out by a novel scheme that parametrically modulates longitudinal stress in doubly clamped beam NEMS resonators. Parametric pumping and signal amplification are demonstrated for VHF resonators up to approximately 130 MHz and provide useful enhancement of both resonance signal amplitude and quality factor. We find that Joule heating and reduced thermal conductance in these nanostructures ultimately impose an upper limit to device performance. We develop a theoretical model to account for both the parametric response and nonequilibrium thermal transport in these composite nanostructures. The results closely conform to our experimental observations, elucidate the frequency and threshold-voltage scaling in parametric VHF NEMS resonators and sensors, and establish the ultimate sensitivity limits of this approach.

  14. Auto-identification of engine fault acoustic signal through inverse trigonometric instantaneous frequency analysis

    Directory of Open Access Journals (Sweden)

    Dayong Ning

    2016-03-01

    Full Text Available The acoustic signals of internal combustion engines contain valuable information about the condition of engines. These signals can be used to detect incipient faults in engines. However, these signals are complex and composed of a faulty component and other noise signals of background. As such, engine conditions’ characteristics are difficult to extract through wavelet transformation and acoustic emission techniques. In this study, an instantaneous frequency analysis method was proposed. A new time–frequency model was constructed using a fixed amplitude and a variable cycle sine function to fit adjacent points gradually from a time domain signal. The instantaneous frequency corresponds to single value at any time. This study also introduced instantaneous frequency calculation on the basis of an inverse trigonometric fitting method at any time. The mean value of all local maximum values was then considered to identify the engine condition automatically. Results revealed that the mean of local maximum values under faulty conditions differs from the normal mean. An experiment case was also conducted to illustrate the availability of the proposed method. Using the proposed time–frequency model, we can identify engine condition and determine abnormal sound produced by faulty engines.

  15. Two models of the sound-signal frequency dependence on the animal body size as exemplified by the ground squirrels of Eurasia (mammalia, rodentia).

    Science.gov (United States)

    Nikol'skii, A A

    2017-11-01

    Dependence of the sound-signal frequency on the animal body length was studied in 14 ground squirrel species (genus Spermophilus) of Eurasia. Regression analysis of the total sample yielded a low determination coefficient (R 2 = 26%), because the total sample proved to be heterogeneous in terms of signal frequency within the dimension classes of animals. When the total sample was divided into two groups according to signal frequency, two statistically significant models (regression equations) were obtained in which signal frequency depended on the body size at high determination coefficients (R 2 = 73 and 94% versus 26% for the total sample). Thus, the problem of correlation between animal body size and the frequency of their vocal signals does not have a unique solution.

  16. ISIS 1 measurements of high-frequency backscatter inside the ionosphere

    International Nuclear Information System (INIS)

    James, H.G.

    1989-01-01

    A study has been made of high-frequency backscatter observed by the ISIS 1 topside sounder at orbital heights from approximately 600 to 800 km. Signals are detected during high-latitude passes at radar ranges x of up to about 400 km and at frequencies from about the X mode cutoff at the spacecraft (usually around 5 MHz) up to 10 MHz typically and 18 MHz occasionally. The signals are interpreted as coherent aspect-sensitive scatter. The absolute power of return signals at high latitudes usually varies as x -2 for x ≤ 150 km. This implies that the scattering cross-section density σ is constant for all azimuths about the magnetic field and for ranges out to 150 km or, in other words, that irregularity patches have a constant σ over cross-field dimensions of 300 km. At larger ranges the signal often falls off more sharply with x, indicating azimuthal variations in σ. The cross section scaled from the data using the radar equation is found to have values centered near 10 -8 to 10 -7 m -1 for the most intense signals, referred to an assumed polar-aspect angle sensitivity. However, the magnitude of σ drops by about 2 orders of magnitude in the frequency range 5-15 MHz. Previous statistical studies have established that strong backscatter is restricted to auroral latitudes. Here the polar distribution of backscatter has been plotted for two sets of passes over the south pole, one collected during austral winter and the other during summer. The strongest backscatter is located at invariant latitudes around 80 degree. Backscatter is significantly stronger and distributed more extensively over the polar cap in winter than in summer

  17. Top down and bottom up selection drives variations in frequency and form of a visual signal.

    Science.gov (United States)

    Yeh, Chien-Wei; Blamires, Sean J; Liao, Chen-Pan; Tso, I-Min

    2015-03-30

    The frequency and form of visual signals can be shaped by selection from predators, prey or both. When a signal simultaneously attracts predators and prey selection may favour a strategy that minimizes risks while attracting prey. Accordingly, varying the frequency and form of the silken decorations added to their web may be a way that Argiope spiders minimize predation while attracting prey. Nonetheless, the role of extraneous factors renders the influences of top down and bottom up selection on decoration frequency and form variation difficult to discern. Here we used dummy spiders and decorations to simulate four possible strategies that the spider Argiope aemula may choose and measured the prey and predator attraction consequences for each in the field. The strategy of decorating at a high frequency with a variable form attracted the most prey, while that of decorating at a high frequency with a fixed form attracted the most predators. These results suggest that mitigating the cost of attracting predators while maintaining prey attraction drives the use of variation in decoration form by many Argiope spp. when decorating frequently. Our study highlights the importance of considering top-down and bottom up selection pressure when devising evolutionary ecology experiments.

  18. Research of propagation the high frequency signals during total solar eclipses

    Science.gov (United States)

    Ryabova, Mariya; Ivanov, Vladimir; Ivanov, Dmitrii; Riabova, Natalia; Elsukov, Aleksei

    Vertical-oblique sounding methods are special importance for the study; they provide data on the electron concentration. In panoramic sounders, the mean frequencies of sounding signals vary consequently in the range of apriori uncertainty of the conditions of their reflection from the ionosphere. The aim of this work is the experimental study of the variations in the MUFs along one-hop HF lines during the total solar eclipses, and their application for the estimation of the effective recombination coefficient. To solve the above problem, experiments were carried out with the use of a chirp sounder manufactured at the Volga State University of Technology. The main advantages of chirp sounder are connected with the use of continuous chirps, which allow for the use of methods of optimal reception when deciphering in a frequency region, which provides for a signal-to-noise ratio acceptable for obtaining reliable results. We carried out experiments on oblique chirp sounding of the ionosphere during the total solar eclipse of March 29, 2006, and on the reference days of March 28 and 30, 2006, as well as during the total solar eclipse of August 1, 2008, and the reference days of July 31 and August 2, 2008. The ionosonde transmitters were located in Great Britain (the town of Inskip), Cyprus, and Irkutsk, and the receiver was located in Yoshkar-Ola. The maximal phases of the eclipse of March 29 at the target sounding point (TSP) were 0.89 for Cyprus-Yoshkar-Ola (observed at 11:15 UT) and 0.49 for Inskip-Yoshkar-Ola (observed at 11:03 UT); for the eclipse of August 1, 1 for Irkutsk-Yoshkar-Ola (observed at 11:36 UT). Based on the primary data (ionograms), the secondary data were determined in automatic mode. In particular, diurnal variations in the MUF of the 1F2 and 2F2 modes were calculated for the eclipse periods and the reference days along different radio paths. Variation in the MUF on the reference days required the use of a smoothing procedure, which was carried out

  19. Frequency modulator. Transmission of meteorological signals in LVC

    International Nuclear Information System (INIS)

    Rivero G, P.T.; Ramirez S, R.; Gonzalez M, J.L.; Rojas N, P.; Celis del Angel, L.

    2007-01-01

    The development of the frequency modulator and demodulator circuit for transmission of meteorological signals by means of fiber optics of the meteorology station to the nuclear reactor unit 1 in the Laguna Verde Central in Veracruz is described. (Author)

  20. Multi-Gigahertz radar range processing of baseband and RF carrier modulated signals in Tm:YAG

    International Nuclear Information System (INIS)

    Merkel, K.D.; Krishna Mohan, R.; Cole, Z.; Chang, T.; Olson, A.; Babbitt, W.R.

    2004-01-01

    An optical device is described and demonstrated that uses a spatial-spectral holographic material to perform coherent signal processing operations on analog, high-bandwidth optical signals with large time-bandwidth-products. Signal processing is performed as the material records the coherent spectral interference (or cross-power spectrum) of modulated optical signals as a spatial-spectral population grating between electronic transition states. Multiple exposures of processing pulse sequences are integrated with increasing grating strength. The device, coined as the Spatial-Spectral Coherent Holographic Integrating Processor (or S 2 -CHIP), is described as currently envisioned for a broadband, mid-to-high pulse repetition frequency range-Doppler radar signal processing system. Experiments were performed in Tm:YAG (0.1 at% at 5 K) to demonstrate time delay variation, integration dynamics, and effects of coding as applied to a radar range processor. These demonstrations used baseband modulation with a 1 gigabit per second (GPBS) bit rate and code length of 512 bits (512 ns), where delays up to 1.0 μs were resolved with greater than a 40 dB peak to RMS sidelobe ratio after 800 processing shots. Multi-GHz processing was demonstrated using a bit rate of 2.5 GBPS (baseband modulation) and code length of 2048 bits (819.2 ns). Processing of double-sideband modulated signals on a radio frequency (RF) carrier was demonstrated, where 512 bit, 1.0 GBPS codes were modulated on a 1.75 GHz carrier and then modulated on the optical carrier

  1. Exploiting the dispersion of the double-negative-index fishnet metamaterial to create a broadband low-profile metallic lens.

    Science.gov (United States)

    Orazbayev, B; Pacheco-Peña, V; Beruete, M; Navarro-Cía, M

    2015-04-06

    Metamaterial lenses with close values of permittivity and permeability usually display low reflection losses at the expense of narrow single frequency operation. Here, a broadband low-profile lens is designed by exploiting the dispersion of a fishnet metamaterial together with the zoning technique. The lens operates in a broadband regime from 54 GHz to 58 GHz, representing a fractional bandwidth ~7%, and outperforms Silicon lenses between 54 and 55.5 GHz. This broadband operation is demonstrated by a systematic analysis comprising Huygens-Fresnel analytical method, full-wave numerical simulations and experimental measurements at millimeter waves. For demonstrative purposes, a detailed study of the lens operation at two frequencies is done for the most important lens parameters (focal length, depth of focus, resolution, radiation diagram). Experimental results demonstrate diffraction-limited ~0.5λ transverse resolution, in agreement with analytical and numerical calculations. In a lens antenna configuration, a directivity as high as 16.6 dBi is achieved. The different focal lengths implemented into a single lens could be potentially used for realizing the front end of a non-mechanical zoom millimeter-wave imaging system.

  2. A two-dimensional regularization algorithm for density profile evaluation from broadband reflectometry

    International Nuclear Information System (INIS)

    Nunes, F.; Varela, P.; Silva, A.; Manso, M.; Santos, J.; Nunes, I.; Serra, F.; Kurzan, B.; Suttrop, W.

    1997-01-01

    Broadband reflectometry is a current technique that uses the round-trip group delays of reflected frequency-swept waves to measure density profiles of fusion plasmas. The main factor that may limit the accuracy of the reconstructed profiles is the interference of the probing waves with the plasma density fluctuations: plasma turbulence leads to random phase variations and magneto hydrodynamic activity produces mainly strong amplitude and phase modulations. Both effects cause the decrease, and eventually loss, of signal at some frequencies. Several data processing techniques can be applied to filter and/or interpolate noisy group delay data obtained from turbulent plasmas with a single frequency sweep. Here, we propose a more powerful algorithm performing two-dimensional regularization (in space and time) of data provided by multiple consecutive frequency sweeps, which leads to density profiles with improved accuracy. The new method is described and its application to simulated data corrupted by noise and missing data is considered. It is shown that the algorithm improves the identification of slowly varying plasma density perturbations by attenuating the effect of fast fluctuations and noise contained in experimental data. First results obtained with this method in ASDEX Upgrade tokamak are presented. copyright 1997 American Institute of Physics

  3. A Serendipitous MWA Search for Narrowband Signals from ‘Oumuamua

    Science.gov (United States)

    Tingay, S. J.; Kaplan, D. L.; Lenc, E.; Croft, S.; McKinley, B.; Beardsley, A.; Crosse, B.; Emrich, D.; Franzen, T. M. O.; Gaensler, B. M.; Horsley, L.; Johnston-Hollitt, M.; Kenney, D.; Morales, M. F.; Pallot, D.; Steele, K.; Trott, C. M.; Walker, M.; Wayth, R. B.; Williams, A.; Wu, C.

    2018-04-01

    We examine data from the Murchison Widefield Array (MWA) in the frequency range 72–102 MHz for a field of view that serendipitously contained the interstellar object ‘Oumuamua on 2017 November 28. Observations took place with a time resolution of 0.5 s and a frequency resolution of 10 kHz. Based on the interesting but highly unlikely suggestion that ‘Oumuamua is an interstellar spacecraft, due to some unusual orbital and morphological characteristics, we examine our data for signals that might indicate the presence of intelligent life associated with ‘Oumuamua. We searched our radio data for (1) impulsive narrowband signals, (2) persistent narrowband signals, and (3) impulsive broadband signals. We found no such signals with nonterrestrial origins and make estimates of the upper limits on equivalent isotropic radiated power (EIRP) for these three cases of approximately 7 kW, 840 W, and 100 kW, respectively. These transmitter powers are well within the capabilities of human technologies, and are therefore plausible for alien civilizations. While the chances of positive detection in any given search for extraterrestrial intelligence (SETI) experiment are vanishingly small, the characteristics of new generation telescopes such as the MWA (and, in the future, the Square Kilometre Array) make certain classes of SETI experiments easy, or even a trivial by-product of astrophysical observations. This means that the future costs of SETI experiments are very low, allowing large target lists to partially balance the low probability of a positive detection.

  4. Broadband time domain acoustic holography based on the discrete orthonormal S-transform

    NARCIS (Netherlands)

    Zhou, H.; Lopez Arteaga, I.; Nijmeijer, H.; Lim, Kian Meng

    2015-01-01

    The purpose of this paper is to deal with the problem of nonstationary broadband sound fields more efficiently. A basis function of the discrete orthonormal S-transform (DOST) is used to analyze the measured signal. With respect to the time domain signal in a certain band, DOST leads to a

  5. Crossed SMPS MOSFET-based protection circuit for high frequency ultrasound transceivers and transducers.

    Science.gov (United States)

    Choi, Hojong; Shung, K Kirk

    2014-06-12

    The ultrasonic transducer is one of the core components of ultrasound systems, and the transducer's sensitivity is significantly related the loss of electronic components such as the transmitter, receiver, and protection circuit. In an ultrasonic device, protection circuits are commonly used to isolate the electrical noise between an ultrasound transmitter and transducer and to minimize unwanted discharged pulses in order to protect the ultrasound receiver. However, the performance of the protection circuit and transceiver obviously degrade as the operating frequency or voltage increases. We therefore developed a crossed SMPS (Switching Mode Power Supply) MOSFET-based protection circuit in order to maximize the sensitivity of high frequency transducers in ultrasound systems.The high frequency pulse signals need to trigger the transducer, and high frequency pulse signals must be received by the transducer. We therefore selected the SMPS MOSFET, which is the main component of the protection circuit, to minimize the loss in high frequency operation. The crossed configuration of the protection circuit can drive balanced bipolar high voltage signals from the pulser and transfer the balanced low voltage echo signals from the transducer. The equivalent circuit models of the SMPS MOSFET-based protection circuit are shown in order to select the proper device components. The schematic diagram and operation mechanism of the protection circuit is provided to show how the protection circuit is constructed. The P-Spice circuit simulation was also performed in order to estimate the performance of the crossed MOSFET-based protection circuit. We compared the performance of our crossed SMPS MOSFET-based protection circuit with a commercial diode-based protection circuit. At 60 MHz, our expander and limiter circuits have lower insertion loss than the commercial diode-based circuits. The pulse-echo test is typical method to evaluate the sensitivity of ultrasonic transducers

  6. Analysis on frequency response of trans-impedance amplifier (TIA) for signal-to-noise ratio (SNR) enhancement in optical signal detection system using lock-in amplifier (LIA)

    Science.gov (United States)

    Kim, Ji-Hoon; Jeon, Su-Jin; Ji, Myung-Gi; Park, Jun-Hee; Choi, Young-Wan

    2017-02-01

    Lock-in amplifier (LIA) has been widely used in optical signal detection systems because it can measure small signal under high noise level. Generally, The LIA used in optical signal detection system is composed of transimpedance amplifier (TIA), phase sensitive detector (PSD) and low pass filter (LPF). But commercial LIA using LPF is affected by flicker noise. To avoid flicker noise, there is 2ω detection LIA using BPF. To improve the dynamic reserve (DR) of the 2ω LIA, the signal to noise ratio (SNR) of the TIA should be improved. According to the analysis of frequency response of the TIA, the noise gain can be minimized by proper choices of input capacitor (Ci) and feed-back network in the TIA in a specific frequency range. In this work, we have studied how the SNR of the TIA can be improved by a proper choice of frequency range. We have analyzed the way to control this frequency range through the change of passive component in the TIA. The result shows that the variance of the passive component in the TIA can change the specific frequency range where the noise gain is minimized in the uniform gain region of the TIA.

  7. High density terahertz frequency comb produced by coherent synchrotron radiation

    Science.gov (United States)

    Tammaro, S.; Pirali, O.; Roy, P.; Lampin, J.-F.; Ducournau, G.; Cuisset, A.; Hindle, F.; Mouret, G.

    2015-07-01

    Frequency combs have enabled significant progress in frequency metrology and high-resolution spectroscopy extending the achievable resolution while increasing the signal-to-noise ratio. In its coherent mode, synchrotron radiation is accepted to provide an intense terahertz continuum covering a wide spectral range from about 0.1 to 1 THz. Using a dedicated heterodyne receiver, we reveal the purely discrete nature of this emission. A phase relationship between the light pulses leads to a powerful frequency comb spanning over one decade in frequency. The comb has a mode spacing of 846 kHz, a linewidth of about 200 Hz, a fractional precision of about 2 × 10-10 and no frequency offset. The unprecedented potential of the comb for high-resolution spectroscopy is demonstrated by the accurate determination of pure rotation transitions of acetonitrile.

  8. Atmospheric and Fog Effects on Ultra-Wide Band Radar Operating at Extremely High Frequencies.

    Science.gov (United States)

    Balal, Nezah; Pinhasi, Gad A; Pinhasi, Yosef

    2016-05-23

    The wide band at extremely high frequencies (EHF) above 30 GHz is applicable for high resolution directive radars, resolving the lack of free frequency bands within the lower part of the electromagnetic spectrum. Utilization of ultra-wideband signals in this EHF band is of interest, since it covers a relatively large spectrum, which is free of users, resulting in better resolution in both the longitudinal and transverse dimensions. Noting that frequencies in the millimeter band are subjected to high atmospheric attenuation and dispersion effects, a study of the degradation in the accuracy and resolution is presented. The fact that solid-state millimeter and sub-millimeter radiation sources are producing low power, the method of continuous-wave wideband frequency modulation becomes the natural technique for remote sensing and detection. Millimeter wave radars are used as complementary sensors for the detection of small radar cross-section objects under bad weather conditions, when small objects cannot be seen by optical cameras and infrared detectors. Theoretical analysis for the propagation of a wide "chirped" Frequency-Modulated Continuous-Wave (FMCW) radar signal in a dielectric medium is presented. It is shown that the frequency-dependent (complex) refractivity of the atmospheric medium causes distortions in the phase of the reflected signal, introducing noticeable errors in the longitudinal distance estimations, and at some frequencies may also degrade the resolution.

  9. Design of broadband single polarized antenna

    Science.gov (United States)

    Shin, Phoo Kho; Aziz, Mohamad Zoinol Abidin Abd.; Ahmad, Badrul Hisham; Ramli, Mohamad Hafize Bin; Fauzi, Noor Azamiah Md; Malek, Mohd Fareq Abd

    2015-05-01

    In practical wireless communication application, bandwidth enhancement becomes one of the major design considerations. At the same time, circular polarized (CP) antenna received much attention for the applications of modern wireless communication system when compared to linear polarized (LP) antenna. This is because CP antenna can reduce the multipath effect. Hence, broadband antenna with operating frequency at 2.4GHz for WLAN application is proposed. The proposed antenna is done by using L-probe amendment with rectangular patch. The rectangular patch and copper ground plane is separated with 10mm air gap. This approach is used to enhance the bandwidth and the gain of the proposed antenna. The bandwidth of the designed antenna is more than 200MHz which meet broadband application. The return loss for the antenna is below -10dB to achieved 90% matching efficiency. The position of L-probe feed is altered in order to obtained different polarizations. The broadband antenna had been designed and simulated by using Computer Simulation Technology (CST) software. In this paper, the comparison for single polarized antenna with the design of non-inverted patch and inverted patch is discussed. The characteristics of the S-parameter, axial ratio, gain, surface current for each designed antenna are analyzed.

  10. Design of a broadband passive X-band double-balanced mixer in SiGe HBT technology

    DEFF Research Database (Denmark)

    Michaelsen, Rasmus Schandorph; Johansen, Tom Keinicke; Tamborg, Kjeld M.

    2014-01-01

    ) and the radio frequency (RF) port. A break out of the Marchand balun is measured. This demonstrates good phase and magnitude match of 0.7° and 0.11 dB, respectively. The Marchand baluns are broadband with a measured 3 dB bandwidth of 6.4 GHz, while still having a magnitude imbalance better than 0.4 d...... frequency of 8.5 GHz is −9.8 dB at an LO drive level of 15 dBm. The whole mixer is very broadband with 3 dB bandwidth from 7 to 12 GHz covering the entire X-band. The LO–IF, RF–IF, and RF–LO isolation is better than 46, 36, and 36 dB, respectively, in the entire band of operation.......B and a phase imbalance better than 5°. Unfortunately with a rather high loss of 2.5 dB, mainly due to the low Q-factor of the inductors used. The mixer is optimized for use in doppler radars and is highly linear with a 1 dB compression point above 12 dBm IIP2 of 66 dBm. The conversion gain at the center...

  11. System and method for constructing filters for detecting signals whose frequency content varies with time

    Science.gov (United States)

    Qian, S.; Dunham, M.E.

    1996-11-12

    A system and method are disclosed for constructing a bank of filters which detect the presence of signals whose frequency content varies with time. The present invention includes a novel system and method for developing one or more time templates designed to match the received signals of interest and the bank of matched filters use the one or more time templates to detect the received signals. Each matched filter compares the received signal x(t) with a respective, unique time template that has been designed to approximate a form of the signals of interest. The robust time domain template is assumed to be of the order of w(t)=A(t)cos(2{pi}{phi}(t)) and the present invention uses the trajectory of a joint time-frequency representation of x(t) as an approximation of the instantaneous frequency function {phi}{prime}(t). First, numerous data samples of the received signal x(t) are collected. A joint time frequency representation is then applied to represent the signal, preferably using the time frequency distribution series. The joint time-frequency transformation represents the analyzed signal energy at time t and frequency f, P(t,f), which is a three-dimensional plot of time vs. frequency vs. signal energy. Then P(t,f) is reduced to a multivalued function f(t), a two dimensional plot of time vs. frequency, using a thresholding process. Curve fitting steps are then performed on the time/frequency plot, preferably using Levenberg-Marquardt curve fitting techniques, to derive a general instantaneous frequency function {phi}{prime}(t) which best fits the multivalued function f(t). Integrating {phi}{prime}(t) along t yields {phi}{prime}(t), which is then inserted into the form of the time template equation. A suitable amplitude A(t) is also preferably determined. Once the time template has been determined, one or more filters are developed which each use a version or form of the time template. 7 figs.

  12. Visualization of the microcirculatory network in skin by high frequency optoacoustic mesoscopy

    Science.gov (United States)

    Schwarz, Mathias; Aguirre, Juan; Buehler, Andreas; Omar, Murad; Ntziachristos, Vasilis

    2015-07-01

    Optoacoustic (photoacoustic) imaging has a high potential for imaging melanin-rich structures in skin and the microvasculature of the dermis due to the natural chromophores (de)oxyhemoglobin, and melanin. The vascular network in human dermis comprises a large network of arterioles, capillaries, and venules, ranging from 5 μm to more than 100 μm in diameter. The frequency spectrum of the microcirculatory network in human skin is intrinsically broadband, due to the large variety in size of absorbers. In our group we have developed raster-scan optoacoustic mesoscopy (RSOM) that applies a 100 MHz transducer with ultra-wide bandwidth in raster-scan mode achieving lateral resolution of 18 μm. In this study, we applied high frequency RSOM to imaging human skin in a healthy volunteer. We analyzed the frequency spectrum of anatomical structures with respect to depth and show that frequencies >60 MHz contain valuable information of structures in the epidermis and the microvasculature of the papillary dermis. We illustrate that RSOM is capable of visualizing the fine vascular network at and beneath the epidermal-dermal junction, revealing the vascular fingerprint of glabrous skin, as well as the larger venules deeper inside the dermis. We evaluate the ability of the RSOM system in measuring epidermal thickness in both hairy and glabrous skin. Finally, we showcase the capability of RSOM in visualizing benign nevi that will potentially help in imaging the penetration depth of melanoma.

  13. Signal Identification and Isolation Utilizing Radio Frequency Photonics

    Science.gov (United States)

    2017-09-01

    RF filter is the use of either a FIR or an infinite impulse response (IIR) filter. The FIR filter is simply the discrete convolution sum of the...by using a feedback loop of a fixed delay. In this case, the signal will ideally be a summation of an infinite number of delay round trips. While...and Infinite Impulse Response filters. A combination of FIR and IIR filters can be used to identify the center frequency of an RF signal, as seen in

  14. Broadband and high efficiency all-dielectric metasurfaces for wavefront steering with easily obtained phase shift

    Science.gov (United States)

    Yang, Hui; Deng, Yan

    2017-12-01

    All-dielectric metasurfaces for wavefront deflecting and optical vortex generating with broadband and high efficiency are demonstrated. The unit cell of the metasurfaces is optimized to function as a half wave-plate with high polarization conversion efficiency (94%) and transmittance (94.5%) at the telecommunication wavelength. Under such a condition, we can get rid of the complicated parameter sweep process for phase shift selecting. Hence, a phase coverage ranges from 0 to 2 π can be easily obtained by introducing the Pancharatnam-Berry phase. Metasurfaces composed of the two pre-designed super cells are demonstrated for optical beam deflecting and vortex beam generating. It is found that the metasurfaces with more phase shift sampling points (small phase shift increment) exhibit better performance. Moreover, optical vortex beams can be generated by the designed metasurfaces within a wavelength range of 200 nm. These results will provide a viable route for designing broadband and high efficiency devices related to phase modulation.

  15. High-frequency fluctuation measurements by far-infrared laser Faraday-effect polarimetry-interferometry and forward scattering system on MST.

    Science.gov (United States)

    Ding, W X; Lin, L; Duff, J R; Brower, D L

    2014-11-01

    Magnetic fluctuation-induced transport driven by global tearing modes has been measured by Faraday-effect polarimetry and interferometry (phase measurements) in the MST reversed field pinch. However, the role of small-scale broadband magnetic and density turbulence in transport remains unknown. In order to investigate broadband magnetic turbulence, we plan to upgrade the existing detector system by using planar-diode fundamental waveguide mixers optimized for high sensitivity. Initial tests indicate these mixers have ×10 sensitivity improvement compared to currently employed corner-cube Schottky-diode mixers and ×5 lower noise. Compact mixer design will allow us to resolve the wavenumbers up to k ∼ 1-2 cm(-1) for beam width w = 1.5 cm and 15 cm(-1) for beam width w = 2 mm. The system can also be used to measure the scattered signal (amplitude measurement) induced by both plasma density and magnetic fluctuations.

  16. Perceptual Coding of Audio Signals Using Adaptive Time-Frequency Transform

    Directory of Open Access Journals (Sweden)

    Karthikeyan Umapathy

    2007-08-01

    Full Text Available Wide band digital audio signals have a very high data-rate associated with them due to their complex nature and demand for high-quality reproduction. Although recent technological advancements have significantly reduced the cost of bandwidth and miniaturized storage facilities, the rapid increase in the volume of digital audio content constantly compels the need for better compression algorithms. Over the years various perceptually lossless compression techniques have been introduced, and transform-based compression techniques have made a significant impact in recent years. In this paper, we propose one such transform-based compression technique, where the joint time-frequency (TF properties of the nonstationary nature of the audio signals were exploited in creating a compact energy representation of the signal in fewer coefficients. The decomposition coefficients were processed and perceptually filtered to retain only the relevant coefficients. Perceptual filtering (psychoacoustics was applied in a novel way by analyzing and performing TF specific psychoacoustics experiments. An added advantage of the proposed technique is that, due to its signal adaptive nature, it does not need predetermined segmentation of audio signals for processing. Eight stereo audio signal samples of different varieties were used in the study. Subjective (mean opinion score—MOS listening tests were performed and the subjective difference grades (SDG were used to compare the performance of the proposed coder with MP3, AAC, and HE-AAC encoders. Compression ratios in the range of 8 to 40 were achieved by the proposed technique with subjective difference grades (SDG ranging from –0.53 to –2.27.

  17. Modeling off-frequency binaural masking for short- and long-duration signals.

    Science.gov (United States)

    Nitschmann, Marc; Yasin, Ifat; Henning, G Bruce; Verhey, Jesko L

    2017-08-01

    Experimental binaural masking-pattern data are presented together with model simulations for 12- and 600-ms signals. The masker was a diotic 11-Hz wide noise centered on 500 Hz. The tonal signal was presented either diotically or dichotically (180° interaural phase difference) with frequencies ranging from 400 to 600 Hz. The results and the modeling agree with previous data and hypotheses; simulations with a binaural model sensitive to monaural modulation cues show that the effect of duration on off-frequency binaural masking-level differences is mainly a result of modulation cues which are only available in the monaural detection of long signals.

  18. Time-Frequency Analysis and Hermite Projection Method Applied to Swallowing Accelerometry Signals

    Directory of Open Access Journals (Sweden)

    Ervin Sejdić

    2010-01-01

    Full Text Available Fast Hermite projections have been often used in image-processing procedures such as image database retrieval, projection filtering, and texture analysis. In this paper, we propose an innovative approach for the analysis of one-dimensional biomedical signals that combines the Hermite projection method with time-frequency analysis. In particular, we propose a two-step approach to characterize vibrations of various origins in swallowing accelerometry signals. First, by using time-frequency analysis we obtain the energy distribution of signal frequency content in time. Second, by using fast Hermite projections we characterize whether the analyzed time-frequency regions are associated with swallowing or other phenomena (vocalization, noise, bursts, etc.. The numerical analysis of the proposed scheme clearly shows that by using a few Hermite functions, vibrations of various origins are distinguishable. These results will be the basis for further analysis of swallowing accelerometry to detect swallowing difficulties.

  19. Asymptotically exact localized expansions for signals in the time–frequency domain

    International Nuclear Information System (INIS)

    Muzhikyan, Aramazd H; Avanesyan, Gagik T

    2012-01-01

    Based on a unique waveform with strong exponential localization property, an exact mathematical method for solving problems in signal analysis in the time–frequency domain is presented. An analogue of the Gabor frame exposes the non-commutative geometry of the time–frequency plane. Signals are visualized using the constructed graphical representation. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’. (paper)

  20. Broadband and Resonant Approaches to Axion Dark Matter Detection.

    Science.gov (United States)

    Kahn, Yonatan; Safdi, Benjamin R; Thaler, Jesse

    2016-09-30

    When ultralight axion dark matter encounters a static magnetic field, it sources an effective electric current that follows the magnetic field lines and oscillates at the axion Compton frequency. We propose a new experiment to detect this axion effective current. In the presence of axion dark matter, a large toroidal magnet will act like an oscillating current ring, whose induced magnetic flux can be measured by an external pickup loop inductively coupled to a SQUID magnetometer. We consider both resonant and broadband readout circuits and show that a broadband approach has advantages at small axion masses. We estimate the reach of this design, taking into account the irreducible sources of noise, and demonstrate potential sensitivity to axionlike dark matter with masses in the range of 10^{-14}-10^{-6}  eV. In particular, both the broadband and resonant strategies can probe the QCD axion with a GUT-scale decay constant.

  1. Broadband sound blocking in phononic crystals with rotationally symmetric inclusions.

    Science.gov (United States)

    Lee, Joong Seok; Yoo, Sungmin; Ahn, Young Kwan; Kim, Yoon Young

    2015-09-01

    This paper investigates the feasibility of broadband sound blocking with rotationally symmetric extensible inclusions introduced in phononic crystals. By varying the size of four equally shaped inclusions gradually, the phononic crystal experiences remarkable changes in its band-stop properties, such as shifting/widening of multiple Bragg bandgaps and evolution to resonance gaps. Necessary extensions of the inclusions to block sound effectively can be determined for given incident frequencies by evaluating power transmission characteristics. By arraying finite dissimilar unit cells, the resulting phononic crystal exhibits broadband sound blocking from combinational effects of multiple Bragg scattering and local resonances even with small-numbered cells.

  2. FPGA implementation of high-frequency multiple PWM for variable voltage variable frequency controller

    Energy Technology Data Exchange (ETDEWEB)

    Boumaaraf, Abdelâali, E-mail: aboumaaraf@yahoo.fr [Université Abbès Laghrour, Laboratoire des capteurs, Instrumentations et procédés (LCIP), Khenchela (Algeria); University of Farhat Abbas Setif1, Sétif, 19000 (Algeria); Mohamadi, Tayeb [University of Farhat Abbas Setif1, Sétif, 19000 (Algeria); Gourmat, Laïd [Université Abbès Laghrour, Khenchela, 40000 (Algeria)

    2016-07-25

    In this paper, we present the FPGA implementation of the multiple pulse width modulation (MPWM) signal generation with repetition of data segments, applied to the variable frequency variable voltage systems and specially at to the photovoltaic water pumping system, in order to generate a signal command very easily between 10 Hz to 60 Hz with a small frequency and reduce the cost of the control system.

  3. Imaging of endogenous exchangeable proton signals in the human brain using frequency labeled exchange transfer imaging.

    Science.gov (United States)

    Yadav, Nirbhay N; Jones, Craig K; Hua, Jun; Xu, Jiadi; van Zijl, Peter C M

    2013-04-01

    To image endogenous exchangeable proton signals in the human brain using a recently reported method called frequency labeled exchange transfer (FLEX) MRI. As opposed to labeling exchangeable protons using saturation (i.e., chemical exchange saturation transfer, or CEST), FLEX labels exchangeable protons with their chemical shift evolution. The use of short high-power frequency pulses allows more efficient labeling of rapidly exchanging protons, while time domain acquisition allows removal of contamination from semi-solid magnetization transfer effects. FLEX-based exchangeable proton signals were detected in human brain over the 1-5 ppm frequency range from water. Conventional magnetization transfer contrast and the bulk water signal did not interfere in the FLEX spectrum. The information content of these signals differed from in vivo CEST data in that the average exchange rate of these signals was 350-400 s(-1) , much faster than the amide signal usually detected using direct saturation (∼30 s(-1) ). Similarly, fast exchanging protons could be detected in egg white in the same frequency range where amide and amine protons of mobile proteins and peptides are known to resonate. FLEX MRI in the human brain preferentially detects more rapidly exchanging amide/amine protons compared to traditional CEST experiments, thereby changing the information content of the exchangeable proton spectrum. This has the potential to open up different types of endogenous applications as well as more easy detection of rapidly exchanging protons in diaCEST agents or fast exchanging units such as water molecules in paracest agents without interference of conventional magnetization transfer contrast. Copyright © 2013 Wiley Periodicals, Inc.

  4. Ultra-broadband THz time-domain spectroscopy of common polymers using THz air photonics

    DEFF Research Database (Denmark)

    D’Angelo, Francesco; Mics, Zoltán; Bonn, Mischa

    2014-01-01

    -domain spectrometer employing air-photonics for the generation and detection of single-cycle sub-50 fs THz transients. The time domain measurements provide direct access to both the absorption and refractive index spectra. The polymers LDPE and TOPAS® demonstrate negligible absorption and spectrally-flat refractive...... index across the entire spectroscopy window, revealing the high potential of these polymers for applications in THz photonics such as ultra-broadband polymer-based dielectric mirrors, waveguides, and fibers. Resonant high-frequency polar vibrational modes are observed and assigned in polymers PA6...... and PTFE, and their dielectric functions in the complete frequency window 2-15 THz are theoretically reproduced. Our results demonstrate the potential of ultrabroadband air-photonics-based THz time domain spectroscopy as a valuable analytic tool for materials science....

  5. Analyzing Broadband Divide in the Farming Sector

    DEFF Research Database (Denmark)

    Jensen, Michael; Gutierrez Lopez, Jose Manuel; Pedersen, Jens Myrup

    2013-01-01

    , upstream and downstream connection. The main constraint is that farms are naturally located in rural areas where the required access broadband data rates are not available. This paper studies the broadband divide in relation to the Danish agricultural sector. Results show how there is an important......Agriculture industry has been evolving for centuries. Currently, the technological development of Internet oriented farming tools allows to increase the productivity and efficiency of this sector. Many of the already available tools and applications require high bandwidth in both directions...... difference between the broadband availability for farms and the rest of the households/buildings the country. This divide may be slowing down the potential technological development of the farming industry, in order to keep their competitiveness in the market. Therefore, broadband development in rural areas...

  6. Broadband terahertz wave deflection based on C-shape complex metamaterials with phase discontinuities

    KAUST Repository

    Zhang, Xueqian; Tian, Zhen; Yue, Weisheng; Gu, Jianqiang; Zhang, Shuang; Han, Jiaguang; Zhang, Weili

    2013-01-01

    A broadband terahertz wave deflector based on metasurface induced phase discontinuities is reported. Various frequency components ranging from 0.43 to 1.0 THz with polarization orthogonal to the incidence are deflected into a broad range of angles from 25° to 84°. A Fresnel zone plate consequently developed from the beam deflector is capable of focusing a broadband terahertz radiation. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Broadband terahertz wave deflection based on C-shape complex metamaterials with phase discontinuities

    KAUST Repository

    Zhang, Xueqian

    2013-06-21

    A broadband terahertz wave deflector based on metasurface induced phase discontinuities is reported. Various frequency components ranging from 0.43 to 1.0 THz with polarization orthogonal to the incidence are deflected into a broad range of angles from 25° to 84°. A Fresnel zone plate consequently developed from the beam deflector is capable of focusing a broadband terahertz radiation. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Enhanced noise tolerance for 10 Gb/s Bi-directional cross-wavelength reuse colorless WDM-PON by using spectrally shaped OFDM signals

    Science.gov (United States)

    Choudhury, Pallab K.

    2018-05-01

    Spectrally shaped orthogonal frequency division multiplexing (OFDM) signal for symmetric 10 Gb/s cross-wavelength reuse reflective semiconductor optical amplifier (RSOA) based colorless wavelength division multiplexed passive optical network (WDM-PON) is proposed and further analyzed to support broadband services of next generation high speed optical access networks. The generated OFDM signal has subcarriers in separate frequency ranges for downstream and upstream, such that the re-modulation noise can be effectively minimized in upstream data receiver. Moreover, the cross wavelength reuse approach improves the tolerance against Rayleigh backscattering noise due to the propagation of different wavelengths in the same feeder fiber. The proposed WDM-PON is successfully demonstrated for 25 km fiber with 16-QAM (quadrature amplitude modulation) OFDM signal having bandwidth of 2.5 GHz for 10 Gb/s operation and subcarrier frequencies in 3-5.5 GHz and DC-2.5 GHz for downstream (DS) and upstream (US) transmission respectively. The result shows that the proposed scheme maintains a good bit error rate (BER) performance below the forward error correction (FEC) limit of 3.8 × 10-3 at acceptable receiver sensitivity and provides a high resilience against re-modulation and Rayleigh backscattering noises as well as chromatic dispersion.

  9. Time-frequency analysis of time-varying modulated signals based on improved energy separation by iterative generalized demodulation

    Science.gov (United States)

    Feng, Zhipeng; Chu, Fulei; Zuo, Ming J.

    2011-03-01

    Energy separation algorithm is good at tracking instantaneous changes in frequency and amplitude of modulated signals, but it is subject to the constraints of mono-component and narrow band. In most cases, time-varying modulated vibration signals of machinery consist of multiple components, and have so complicated instantaneous frequency trajectories on time-frequency plane that they overlap in frequency domain. For such signals, conventional filters fail to obtain mono-components of narrow band, and their rectangular decomposition of time-frequency plane may split instantaneous frequency trajectories thus resulting in information loss. Regarding the advantage of generalized demodulation method in decomposing multi-component signals into mono-components, an iterative generalized demodulation method is used as a preprocessing tool to separate signals into mono-components, so as to satisfy the requirements by energy separation algorithm. By this improvement, energy separation algorithm can be generalized to a broad range of signals, as long as the instantaneous frequency trajectories of signal components do not intersect on time-frequency plane. Due to the good adaptability of energy separation algorithm to instantaneous changes in signals and the mono-component decomposition nature of generalized demodulation, the derived time-frequency energy distribution has fine resolution and is free from cross term interferences. The good performance of the proposed time-frequency analysis is illustrated by analyses of a simulated signal and the on-site recorded nonstationary vibration signal of a hydroturbine rotor during a shut-down transient process, showing that it has potential to analyze time-varying modulated signals of multi-components.

  10. Analisis Perkembangan Internet Broadband di Daerah Perbatasan Sulawesi Utara

    Directory of Open Access Journals (Sweden)

    Riva'atul Adaniah Wahab

    2016-12-01

    infrastructure is still insufficient, the availability of high-quality internet broadband services with low rates are still difficult to realize. From the aspect of demand, stigma or the community perception that the internet is not important makes the people don't have internet access. The barriers is predominantly lack of knowledge in internet usage. This factor also causes community internet broadband literacy at level 0. As solutions, the preparation and establishment of policies and regulations such as the QoS service, interconnection, infrastructure sharing can provide high-quality internet broadband internet at a cheaper price. Besides the distribution of valuable mobile device (smartphone should also be encouraged by the application of local content level for the production of the device. No less important is the increase of community lietracy in internet broadband through socialization or training, both formal and informal.

  11. Spectral analysis of highly aliased sea-level signals

    Science.gov (United States)

    Ray, Richard D.

    1998-10-01

    Observing high-wavenumber ocean phenomena with a satellite altimeter generally calls for "along-track" analyses of the data: measurements along a repeating satellite ground track are analyzed in a point-by-point fashion, as opposed to spatially averaging data over multiple tracks. The sea-level aliasing problems encountered in such analyses can be especially challenging. For TOPEX/POSEIDON, all signals with frequency greater than 18 cycles per year (cpy), including both tidal and subdiurnal signals, are folded into the 0-18 cpy band. Because the tidal bands are wider than 18 cpy, residual tidal cusp energy, plus any subdiurnal energy, is capable of corrupting any low-frequency signal of interest. The practical consequences of this are explored here by using real sea-level measurements from conventional tide gauges, for which the true oceanographic spectrum is known and to which a simulated "satellite-measured" spectrum, based on coarsely subsampled data, may be compared. At many locations the spectrum is sufficently red that interannual frequencies remain unaffected. Intra-annual frequencies, however, must be interpreted with greater caution, and even interannual frequencies can be corrupted if the spectrum is flat. The results also suggest that whenever tides must be estimated directly from the altimetry, response methods of analysis are preferable to harmonic methods, even in nonlinear regimes; this will remain so for the foreseeable future. We concentrate on three example tide gauges: two coastal stations on the Malay Peninsula where the closely aliased K1 and Ssa tides are strong and at Canton Island where trapped equatorial waves are aliased.

  12. First Measurements of High Frequency Cross-Spectra from a Pair of Large Michelson Interferometers

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Aaron S.; Gustafson, Richard; Hogan, Craig; Kamai, Brittany; Kwon, Ohkyung; Lanza, Robert; McCuller, Lee; Meyer, Stephan S.; Richardson, Jonathan; Stoughton, Chris; Tomlin, Raymond; Waldman, Samuel; Weiss, Rainer

    2016-09-01

    Measurements are reported of high frequency cross-spectra of signals from the Fermilab Holometer, a pair of co-located 39 m, high power Michelson interferometers. The instrument obtains differential position sensitivity to cross-correlated signals far exceeding any previous measurement in a broad frequency band extending to the 3.8 MHz inverse light crossing time of the apparatus. A model of universal exotic spatial shear correlations that matches the Planck scale holographic information bound of space-time position states is excluded to 4.6{\\sigma} significance.

  13. High frequency switched-mode stimulation can evoke postsynaptic responses in cerebellar principal neurons

    Directory of Open Access Journals (Sweden)

    Marijn Van Dongen

    2015-03-01

    Full Text Available This paper investigates the efficacy of high frequency switched-mode neural stimulation. Instead of using a constant stimulation amplitude, the stimulus is switched on and off repeatedly with a high frequency (up to 100kHz duty cycled signal. By means of tissue modeling that includes the dynamic properties of both the tissue material as well as the axon membrane, it is first shown that switched-mode stimulation depolarizes the cell membrane in a similar way as classical constant amplitude stimulation.These findings are subsequently verified using in vitro experiments in which the response of a Purkinje cell is measured due to a stimulation signal in the molecular layer of the cerebellum of a mouse. For this purpose a stimulator circuit is developed that is able to produce a monophasic high frequency switched-mode stimulation signal. The results confirm the modeling by showing that switched-mode stimulation is able to induce similar responses in the Purkinje cell as classical stimulation using a constant current source. This conclusion opens up possibilities for novel stimulation designs that can improve the performance of the stimulator circuitry. Care has to be taken to avoid losses in the system due to the higher operating frequency.

  14. Optimization of Quantum-state-preserving Frequency Conversion by Changing the Input Signal

    DEFF Research Database (Denmark)

    Andersen, Lasse Mejling; Reddy, D. V.; McKinstrie, C. J.

    We optimize frequency conversion based on four-wave mixing by using the input modes of the system. We find a 10-25 % higher conversion efficiency relative to a pump-shaped input signal.......We optimize frequency conversion based on four-wave mixing by using the input modes of the system. We find a 10-25 % higher conversion efficiency relative to a pump-shaped input signal....

  15. Multichannel Recorder for Low Frequency Signals: Application of Oscilloscope as Integrated Mobile Service for a Smartphone

    Directory of Open Access Journals (Sweden)

    Michal Kochlan

    2016-01-01

    Full Text Available Data acquisition and processing are well known for some time. Many applications use powerful hardware to acquire, process, and visualize signal waveforms. But there are some applications that do not have to perform high resolution signal acquisition and process large amount of data, for example, low frequency applications of embedded design and applications for remote power grid monitoring. The paper describes special system for low frequency signal data sample acquisition, processing, and visualization implemented as a service on Android-based smart device. The service makes smart device functioning as an oscilloscope or arbitrary waveform generator which is accessible remotely through Bluetooth. The design respects low power consumption requirements, simplicity, and user friendliness in application design. Application scenario was implemented as wireless data acquisition system for power grid monitoring.

  16. Efficient and Robust Detection of GFSK Signals under Dispersive Channel, Modulation Index, and Carrier Frequency Offset Conditions

    Directory of Open Access Journals (Sweden)

    Stephan Weiss

    2005-09-01

    Full Text Available Gaussian frequency shift keying is the modulation scheme specified for Bluetooth. Signal adversities typical in Bluetooth networks include AWGN, multipath propagation, carrier frequency, and modulation index offsets. In our effort to realise a robust but efficient Bluetooth receiver, we adopt a high-performance matched-filter-based detector, which is near optimal in AWGN, but requires a prohibitively costly filter bank for processing of K bits worth of the received signal. However, through filtering over a single bit period and performing phase propagation of intermediate results over successive single-bit stages, we eliminate redundancy involved in providing the matched filter outputs and reduce its complexity by up to 90% (for K=9. The constant modulus signal characteristic and the potential for carrier frequency offsets make the constant modulus algorithm (CMA suitable for channel equalisation, and we demonstrate its effectiveness in this paper. We also introduce a stochastic gradient-based algorithm for carrier frequency offset correction, and show that the relative rotation between successive intermediate filter outputs enables us to detect and correct offsets in modulation index.

  17. Advanced optical signal processing of broadband parallel data signals

    DEFF Research Database (Denmark)

    Oxenløwe, Leif Katsuo; Hu, Hao; Kjøller, Niels-Kristian

    2016-01-01

    Optical signal processing may aid in reducing the number of active components in communication systems with many parallel channels, by e.g. using telescopic time lens arrangements to perform format conversion and allow for WDM regeneration.......Optical signal processing may aid in reducing the number of active components in communication systems with many parallel channels, by e.g. using telescopic time lens arrangements to perform format conversion and allow for WDM regeneration....

  18. Complex Signal Kurtosis and Independent Component Analysis for Wideband Radio Frequency Interference Detection

    Science.gov (United States)

    Schoenwald, Adam; Mohammed, Priscilla; Bradley, Damon; Piepmeier, Jeffrey; Wong, Englin; Gholian, Armen

    2016-01-01

    Radio-frequency interference (RFI) has negatively implicated scientific measurements across a wide variation passive remote sensing satellites. This has been observed in the L-band radiometers SMOS, Aquarius and more recently, SMAP [1, 2]. RFI has also been observed at higher frequencies such as K band [3]. Improvements in technology have allowed wider bandwidth digital back ends for passive microwave radiometry. A complex signal kurtosis radio frequency interference detector was developed to help identify corrupted measurements [4]. This work explores the use of ICA (Independent Component Analysis) as a blind source separation technique to pre-process radiometric signals for use with the previously developed real and complex signal kurtosis detectors.

  19. Micro-Doppler Signal Time-Frequency Algorithm Based on STFRFT

    Directory of Open Access Journals (Sweden)

    Cunsuo Pang

    2016-09-01

    Full Text Available This paper proposes a time-frequency algorithm based on short-time fractional order Fourier transformation (STFRFT for identification of a complicated movement targets. This algorithm, consisting of a STFRFT order-changing and quick selection method, is effective in reducing the computation load. A multi-order STFRFT time-frequency algorithm is also developed that makes use of the time-frequency feature of each micro-Doppler component signal. This algorithm improves the estimation accuracy of time-frequency curve fitting through multi-order matching. Finally, experiment data were used to demonstrate STFRFT’s performance in micro-Doppler time-frequency analysis. The results validated the higher estimate accuracy of the proposed algorithm. It may be applied to an LFM (Linear frequency modulated pulse radar, SAR (Synthetic aperture radar, or ISAR (Inverse synthetic aperture radar, for improving the probability of target recognition.

  20. Micro-Doppler Signal Time-Frequency Algorithm Based on STFRFT.

    Science.gov (United States)

    Pang, Cunsuo; Han, Yan; Hou, Huiling; Liu, Shengheng; Zhang, Nan

    2016-09-24

    This paper proposes a time-frequency algorithm based on short-time fractional order Fourier transformation (STFRFT) for identification of a complicated movement targets. This algorithm, consisting of a STFRFT order-changing and quick selection method, is effective in reducing the computation load. A multi-order STFRFT time-frequency algorithm is also developed that makes use of the time-frequency feature of each micro-Doppler component signal. This algorithm improves the estimation accuracy of time-frequency curve fitting through multi-order matching. Finally, experiment data were used to demonstrate STFRFT's performance in micro-Doppler time-frequency analysis. The results validated the higher estimate accuracy of the proposed algorithm. It may be applied to an LFM (Linear frequency modulated) pulse radar, SAR (Synthetic aperture radar), or ISAR (Inverse synthetic aperture radar), for improving the probability of target recognition.

  1. Efficient Implementation of a Symbol Timing Estimator for Broadband PLC.

    Science.gov (United States)

    Nombela, Francisco; García, Enrique; Mateos, Raúl; Hernández, Álvaro

    2015-08-21

    Broadband Power Line Communications (PLC) have taken advantage of the research advances in multi-carrier modulations to mitigate frequency selective fading, and their adoption opens up a myriad of applications in the field of sensory and automation systems, multimedia connectivity or smart spaces. Nonetheless, the use of these multi-carrier modulations, such as Wavelet-OFDM, requires a highly accurate symbol timing estimation for reliably recovering of transmitted data. Furthermore, the PLC channel presents some particularities that prevent the direct use of previous synchronization algorithms proposed in wireless communication systems. Therefore more research effort should be involved in the design and implementation of novel and robust synchronization algorithms for PLC, thus enabling real-time synchronization. This paper proposes a symbol timing estimator for broadband PLC based on cross-correlation with multilevel complementary sequences or Zadoff-Chu sequences and its efficient implementation in a FPGA; the obtained results show a 90% of success rate in symbol timing estimation for a certain PLC channel model and a reduced resource consumption for its implementation in a Xilinx Kyntex FPGA.

  2. Efficient Implementation of a Symbol Timing Estimator for Broadband PLC

    Directory of Open Access Journals (Sweden)

    Francisco Nombela

    2015-08-01

    Full Text Available Broadband Power Line Communications (PLC have taken advantage of the research advances in multi-carrier modulations to mitigate frequency selective fading, and their adoption opens up a myriad of applications in the field of sensory and automation systems, multimedia connectivity or smart spaces. Nonetheless, the use of these multi-carrier modulations, such as Wavelet-OFDM, requires a highly accurate symbol timing estimation for reliably recovering of transmitted data. Furthermore, the PLC channel presents some particularities that prevent the direct use of previous synchronization algorithms proposed in wireless communication systems. Therefore more research effort should be involved in the design and implementation of novel and robust synchronization algorithms for PLC, thus enabling real-time synchronization. This paper proposes a symbol timing estimator for broadband PLC based on cross-correlation with multilevel complementary sequences or Zadoff-Chu sequences and its efficient implementation in a FPGA; the obtained results show a 90% of success rate in symbol timing estimation for a certain PLC channel model and a reduced resource consumption for its implementation in a Xilinx Kyntex FPGA.

  3. EVALUASI LAYANAN BROADBAND CAMPUS DENGAN MENGGUNAKAN FRAMEWORK COBIT 4.1

    Directory of Open Access Journals (Sweden)

    Fajar Tri Prabowo

    2017-08-01

    Full Text Available Abstract - Broadband campus is a high speed internet service with high transfer rate that implemented within the campus area. The sole purpose of this service is to optimize the internet network in certain area that is still lack of a high speed internet connection. This paper will ellaborate more on the evaluation of certain ongoing broadband campus service at Mahasaraswati University in Denpasar by using COBIT 4.1 Framework. This evaluation is intended to enhance the user effectiveness through existing services. This evaluation was conducted through certain mini-survey by using the broadband campus IT service by examining the university students satisfaction through series of interviews and questionnaires. The conclusion that was inferred through the surveys is that the broadband services within the university gain a subsequently low existing maturity level with 1.9 mark in the COBIT Framework scale. One of the major reason of why the service acquire low satisfaction level within the university is due the students in Mahasaraswati University did not manage to optimize the broadband campus service in the first place

  4. Broadband electromagnetic power harvester from vibrations via frequency conversion by impact oscillations

    International Nuclear Information System (INIS)

    Yuksek, N. S.; Almasri, M.; Feng, Z. C.

    2014-01-01

    In this paper, we propose an electromagnetic power harvester that uses a transformative multi-impact approach to achieve a wide bandwidth response from low frequency vibration sources through frequency-up conversion. The device consists of a pick-up coil, fixed at the free edge of a cantilever beam with high resonant frequency, and two cantilever beams with low excitation frequencies, each with an impact mass attached at its free edge. One of the two cantilevers is designed to resonate at 25 Hz, while the other resonates at 50 Hz within the range of ambient vibration frequency. When the device is subjected to a low frequency vibration, the two low-frequency cantilevers responded by vibrating at low frequencies, and thus their thick metallic masses made impacts with the high resonance frequency cantilever repeatedly at two locations. This has caused it along with the pick-up coil to oscillate, relative to the permanent magnet, with decaying amplitude at its resonance frequency, and results in a wide bandwidth response from 10 to 63 Hz at 2 g. A wide bandwidth response between 10–51 Hz and 10–58 Hz at acceleration values of 0.5 g and 2 g, respectively, were achieved by adjusting the impact cantilever frequencies closer to each other (25 Hz and 45 Hz). A maximum output power of 85 μW was achieved at 5 g at 30 Hz across a load resistor, 2.68 Ω.

  5. Improved MIMO radar GMTI via cyclic-shift transmission of orthogonal frequency division signals

    Science.gov (United States)

    Li, Fuyou; He, Feng; Dong, Zhen; Wu, Manqing

    2018-05-01

    Minimum detectable velocity (MDV) and maximum detectable velocity are both important in ground moving target indication (GMTI) systems. Smaller MDV can be achieved by longer baseline via multiple-input multiple-output (MIMO) radar. Maximum detectable velocity is decided by blind velocities associated with carrier frequencies, and blind velocities can be mitigated by orthogonal frequency division signals. However, the scattering echoes from different carrier frequencies are independent, which is not good for improving MDV performance. An improved cyclic-shift transmission is applied in MIMO GMTI system in this paper. MDV performance is improved due to the longer baseline, and maximum detectable velocity performance is improved due to the mitigation of blind velocities via multiple carrier frequencies. The signal model for this mode is established, the principle of mitigating blind velocities with orthogonal frequency division signals is presented; the performance of different MIMO GMTI waveforms is analysed; and the performance of different array configurations is analysed. Simulation results by space-time-frequency adaptive processing proves that our proposed method is a valid way to improve GMTI performance.

  6. High frequency vibration characteristics of electric wheel system under in-wheel motor torque ripple

    Science.gov (United States)

    Mao, Yu; Zuo, Shuguang; Wu, Xudong; Duan, Xianglei

    2017-07-01

    With the introduction of in-wheel motor, the electric wheel system encounters new vibration problems brought by motor torque ripple excitation. In order to analyze new vibration characteristics of electric wheel system, torque ripple of in-wheel motor based on motor module and vector control system is primarily analyzed, and frequency/order features of the torque ripple are discussed. Then quarter vehicle-electric wheel system (QV-EWS) dynamics model based on the rigid ring tire assumption is established and the main parameters of the model are identified according to tire free modal test. Modal characteristics of the model are further analyzed. The analysis indicates that torque excitation of in-wheel motor is prone to arouse horizontal vibration, in which in-phase rotational, anti-phase rotational and horizontal translational modes of electric wheel system mainly participate. Based on the model, vibration responses of the QV-EWS under torque ripple are simulated. The results show that unlike vertical low frequency (lower than 20 Hz) vibration excited by road roughness, broadband torque ripple will arouse horizontal high frequency (50-100 Hz) vibration of electric wheel system due to participation of the three aforementioned modes. To verify the theoretical analysis, the bench experiment of electric wheel system is conducted and vibration responses are acquired. The experiment demonstrates the high frequency vibration phenomenon of electric wheel system and the measured order features as well as main resonant frequencies agree with simulation results. Through theoretical modeling, analysis and experiments this paper reveals and explains the high frequency vibration characteristics of electric wheel system, providing references for the dynamic analysis, optimal design of QV-EWS.

  7. Broadband silicon polarization beam splitter with a high extinction ratio using a triple-bent-waveguide directional coupler.

    Science.gov (United States)

    Ong, Jun Rong; Ang, Thomas Y L; Sahin, Ezgi; Pawlina, Bryan; Chen, G F R; Tan, D T H; Lim, Soon Thor; Png, Ching Eng

    2017-11-01

    We report on the design and experimental demonstration of a broadband silicon polarization beam splitter (PBS) with a high extinction ratio (ER)≥30  dB. This was achieved using triple-bent-waveguide directional coupling in a single PBS, and cascaded PBS topology. For the single PBS, the bandwidths for an ER≥30  dB are 20 nm for the quasi-TE mode, and 70 nm for the quasi-TM mode when a broadband light source (1520-1610 nm) was employed. The insertion loss (IL) varies from 0.2 to 1 dB for the quasi-TE mode and 0.2-2 dB for the quasi-TM mode. The cascaded PBS improved the bandwidth of the quasi-TE mode for an ER≥30  dB to 90 nm, with a low IL of 0.2-2 dB. To the best of our knowledge, our PBS system is one of the best broadband PBSs with an ER as high as ∼42  dB and a low IL below 1 dB around the central wavelength, and experimentally demonstrated using edge-coupling.

  8. Bilinear Time-frequency Analysis for Lamb Wave Signal Detected by Electromagnetic Acoustic Transducer

    Science.gov (United States)

    Sun, Wenxiu; Liu, Guoqiang; Xia, Hui; Xia, Zhengwu

    2018-03-01

    Accurate acquisition of the detection signal travel time plays a very important role in cross-hole tomography. The experimental platform of aluminum plate under the perpendicular magnetic field is established and the bilinear time-frequency analysis methods, Wigner-Ville Distribution (WVD) and the pseudo-Wigner-Ville distribution (PWVD), are applied to analyse the Lamb wave signals detected by electromagnetic acoustic transducer (EMAT). By extracting the same frequency component of the time-frequency spectrum as the excitation frequency, the travel time information can be obtained. In comparison with traditional linear time-frequency analysis method such as short-time Fourier transform (STFT), the bilinear time-frequency analysis method PWVD is more appropriate in extracting travel time and recognizing patterns of Lamb wave.

  9. Chaos in high-power high-frequency gyrotrons

    International Nuclear Information System (INIS)

    Airila, M.

    2004-01-01

    Gyrotron interaction is a complex nonlinear dynamical process, which may turn chaotic in certain circumstances. The emergence of chaos renders dynamical systems unpredictable and causes bandwidth broadening of signals. Such effects would jeopardize the prospect of advanced gyrotrons in fusion. Therefore, it is important to be aware of the possibility of chaos in gyrotrons. There are three different chaos scenarios closely related to the development of high-power gyrotrons: First, the onset of chaos in electron trajectories would lead to difficulties in the design and efficient operation of depressed potential collectors, which are used for efficiency enhancement. Second, the radio-frequency signal could turn chaotic, decreasing the output power and the spectral purity of the output signal. As a result, mode conversion, transmission, and absorption efficiencies would be reduced. Third, spatio-temporal chaos in the resonator field structure can set a limit for the use of large-diameter interaction cavities and high-order TE modes (large azimuthal index) allowing higher generated power. In this thesis, the issues above are addressed with numerical modeling. It is found that chaos in electron residual energies is practically absent in the parameter region corresponding to high efficiency. Accordingly, depressed collectors are a feasible solution also in advanced high-power gyrotrons. A new method is presented for straightforward numerical solution of the one-dimensional self-consistent time-dependent gyrotron equations, and the method is generalized to two dimensions. In 1D, a chart of gyrotron oscillations is calculated. It is shown that the regions of stationary oscillations, automodulation, and chaos have a complicated topology in the plane of generalized gyrotron variables. The threshold current for chaotic oscillations exceeds typical operating currents by a factor of ten. However, reflection of the output signal may significantly lower the threshold. 2D

  10. Broadband infrared photoluminescence in silicon nanowires with high density stacking faults.

    Science.gov (United States)

    Li, Yang; Liu, Zhihong; Lu, Xiaoxiang; Su, Zhihua; Wang, Yanan; Liu, Rui; Wang, Dunwei; Jian, Jie; Lee, Joon Hwan; Wang, Haiyan; Yu, Qingkai; Bao, Jiming

    2015-02-07

    Making silicon an efficient light-emitting material is an important goal of silicon photonics. Here we report the observation of broadband sub-bandgap photoluminescence in silicon nanowires with a high density of stacking faults. The photoluminescence becomes stronger and exhibits a blue shift under higher laser powers. The super-linear dependence on excitation intensity indicates a strong competition between radiative and defect-related non-radiative channels, and the spectral blue shift is ascribed to the band filling effect in the heterostructures of wurtzite silicon and cubic silicon created by stacking faults.

  11. Broadband spectroscopy of magnetic response in a nano-scale magnetic wire

    International Nuclear Information System (INIS)

    Yamaguchi, A.; Motoi, K.; Miyajima, H.; Utsumi, Y.

    2014-01-01

    We measure the broadband spectra of magnetic response in a single layered ferromagnetic nano-scale wire in order to investigate the size effect on the ferromagnetic resonance. We found that the resonance frequency difference between 300-nm- and 5-μm-wide wires was varied by about 5 GHz due to the shape anisotropy. Furthermore, we experimentally detected the magnetization precession induced by the thermal fluctuation via the rectification of a radio-frequency (rf) current by incorporating an additional direct current (dc) by using Wheatstone bridge circuit. Our investigation renders that the shape anisotropy is of great importance to control the resonance frequency and to provide thermal stability of the microwave devices. - Highlights: • We describe an experimental investigation of the magnetic response of a single layered ferromagnetic nano-scale wire. • We present the conventional broadband microwave spectroscopy with a vector network analyzer and rectifying spectroscopy obtained with a Wheatstone bridge technique. • The investigation enables us to characterize the size effect on the ferromagnetic response and also to detect the magnetization precession induced by the thermal fluctuations

  12. High-frequency combination coding-based steady-state visual evoked potential for brain computer interface

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Feng; Zhang, Xin; Xie, Jun; Li, Yeping; Han, Chengcheng; Lili, Li; Wang, Jing [School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); Xu, Guang-Hua [School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710054 (China)

    2015-03-10

    This study presents a new steady-state visual evoked potential (SSVEP) paradigm for brain computer interface (BCI) systems. The goal of this study is to increase the number of targets using fewer stimulation high frequencies, with diminishing subject’s fatigue and reducing the risk of photosensitive epileptic seizures. The new paradigm is High-Frequency Combination Coding-Based High-Frequency Steady-State Visual Evoked Potential (HFCC-SSVEP).Firstly, we studied SSVEP high frequency(beyond 25 Hz)response of SSVEP, whose paradigm is presented on the LED. The SNR (Signal to Noise Ratio) of high frequency(beyond 40 Hz) response is very low, which is been unable to be distinguished through the traditional analysis method; Secondly we investigated the HFCC-SSVEP response (beyond 25 Hz) for 3 frequencies (25Hz, 33.33Hz, and 40Hz), HFCC-SSVEP produces n{sup n} with n high stimulation frequencies through Frequence Combination Code. Further, Animproved Hilbert-huang transform (IHHT)-based variable frequency EEG feature extraction method and a local spectrum extreme target identification algorithmare adopted to extract time-frequency feature of the proposed HFCC-SSVEP response.Linear predictions and fixed sifting (iterating) 10 time is used to overcome the shortage of end effect and stopping criterion,generalized zero-crossing (GZC) is used to compute the instantaneous frequency of the proposed SSVEP respondent signals, the improved HHT-based feature extraction method for the proposed SSVEP paradigm in this study increases recognition efficiency, so as to improve ITR and to increase the stability of the BCI system. what is more, SSVEPs evoked by high-frequency stimuli (beyond 25Hz) minimally diminish subject’s fatigue and prevent safety hazards linked to photo-induced epileptic seizures, So as to ensure the system efficiency and undamaging.This study tests three subjects in order to verify the feasibility of the proposed method.

  13. High-frequency combination coding-based steady-state visual evoked potential for brain computer interface

    International Nuclear Information System (INIS)

    Zhang, Feng; Zhang, Xin; Xie, Jun; Li, Yeping; Han, Chengcheng; Lili, Li; Wang, Jing; Xu, Guang-Hua

    2015-01-01

    This study presents a new steady-state visual evoked potential (SSVEP) paradigm for brain computer interface (BCI) systems. The goal of this study is to increase the number of targets using fewer stimulation high frequencies, with diminishing subject’s fatigue and reducing the risk of photosensitive epileptic seizures. The new paradigm is High-Frequency Combination Coding-Based High-Frequency Steady-State Visual Evoked Potential (HFCC-SSVEP).Firstly, we studied SSVEP high frequency(beyond 25 Hz)response of SSVEP, whose paradigm is presented on the LED. The SNR (Signal to Noise Ratio) of high frequency(beyond 40 Hz) response is very low, which is been unable to be distinguished through the traditional analysis method; Secondly we investigated the HFCC-SSVEP response (beyond 25 Hz) for 3 frequencies (25Hz, 33.33Hz, and 40Hz), HFCC-SSVEP produces n n with n high stimulation frequencies through Frequence Combination Code. Further, Animproved Hilbert-huang transform (IHHT)-based variable frequency EEG feature extraction method and a local spectrum extreme target identification algorithmare adopted to extract time-frequency feature of the proposed HFCC-SSVEP response.Linear predictions and fixed sifting (iterating) 10 time is used to overcome the shortage of end effect and stopping criterion,generalized zero-crossing (GZC) is used to compute the instantaneous frequency of the proposed SSVEP respondent signals, the improved HHT-based feature extraction method for the proposed SSVEP paradigm in this study increases recognition efficiency, so as to improve ITR and to increase the stability of the BCI system. what is more, SSVEPs evoked by high-frequency stimuli (beyond 25Hz) minimally diminish subject’s fatigue and prevent safety hazards linked to photo-induced epileptic seizures, So as to ensure the system efficiency and undamaging.This study tests three subjects in order to verify the feasibility of the proposed method

  14. Repeating Deep Very Low Frequency Earthquakes: An Evidence of Transition Zone between Brittle and Ductile Zone along Plate Boundary

    Science.gov (United States)

    Ishihara, Y.; Yamamoto, Y.; Arai, R.

    2017-12-01

    Recently slow or low frequency seismic and geodetic events are focused under recognition of important role in tectonic process. The most western region of Ryukyu trench, Yaeyama Islands, is very active area of these type events. It has semiannual-like slow slip (Heki et.al., 2008; Nishimura et.al.,2014) and very frequent shallow very low frequency earthquakes near trench zone (Ando et.al.,2012; Nakamura et.al.,2014). Arai et.al.(2016) identified clear reverse phase discontinuity along plate boundary by air-gun survey, suggesting existence of low velocity layer including fluid. The subducting fluid layer is considered to control slip characteristics. On the other hand, deep low frequency earthquake and tremor observed at south-western Honshu and Shikoku of Japan are not identified well due to lack of high-quality seismic network. A broadband seismic station(ISG/PS) of Pacific21 network is operating in last 20 years that locates on occurrence potential area of low frequency earthquake. We tried to review continuous broadband record, searching low frequency earthquakes. In pilot survey, we found three very low frequency seismic events which are dominant in less than 0.1Hz component and are not listed in earthquake catalogue. Source locates about 50km depth and at transition area between slow slip event and active area of general earthquake along plate boundary. To detect small and/or hidden very low frequency earthquake, we applied matched filter analysis to continuous three components waveform data using pre-reviewed seismogram as template signal. 12 events with high correlation are picked up in last 10 years. Most events have very similar waveform, which means characteristics of repeating deep very low frequency earthquake. The event history of very low frequency earthquake is not related with one of slow slip event in this region. In Yaeyama region, low frequency earthquake, general earthquake and slow slip event occur dividing in space and have apparent

  15. Robust frequency diversity based algorithm for clutter noise reduction of ultrasonic signals using multiple sub-spectrum phase coherence

    Energy Technology Data Exchange (ETDEWEB)

    Gongzhang, R.; Xiao, B.; Lardner, T.; Gachagan, A. [Centre for Ultrasonic Engineering, University of Strathclyde, Glasgow, G1 1XW (United Kingdom); Li, M. [School of Engineering, University of Glasgow, Glasgow, G12 8QQ (United Kingdom)

    2014-02-18

    This paper presents a robust frequency diversity based algorithm for clutter reduction in ultrasonic A-scan waveforms. The performance of conventional spectral-temporal techniques like Split Spectrum Processing (SSP) is highly dependent on the parameter selection, especially when the signal to noise ratio (SNR) is low. Although spatial beamforming offers noise reduction with less sensitivity to parameter variation, phased array techniques are not always available. The proposed algorithm first selects an ascending series of frequency bands. A signal is reconstructed for each selected band in which a defect is present when all frequency components are in uniform sign. Combining all reconstructed signals through averaging gives a probability profile of potential defect position. To facilitate data collection and validate the proposed algorithm, Full Matrix Capture is applied on the austenitic steel and high nickel alloy (HNA) samples with 5MHz transducer arrays. When processing A-scan signals with unrefined parameters, the proposed algorithm enhances SNR by 20dB for both samples and consequently, defects are more visible in B-scan images created from the large amount of A-scan traces. Importantly, the proposed algorithm is considered robust, while SSP is shown to fail on the austenitic steel data and achieves less SNR enhancement on the HNA data.

  16. A high and low noise model for strong motion accelerometers

    Science.gov (United States)

    Clinton, J. F.; Cauzzi, C.; Olivieri, M.

    2010-12-01

    We present reference noise models for high-quality strong motion accelerometer installations. We use continuous accelerometer data acquired by the Swiss Seismological Service (SED) since 2006 and other international high-quality accelerometer network data to derive very broadband (50Hz-100s) high and low noise models. The proposed noise models are compared to the Peterson (1993) low and high noise models designed for broadband seismometers; the datalogger self-noise; background noise levels at existing Swiss strong motion stations; and typical earthquake signals recorded in Switzerland and worldwide. The standard strong motion station operated by the SED consists of a Kinemetrics Episensor (2g clip level; flat acceleration response from 200 Hz to DC; insulated sensor / datalogger systems placed in vault quality sites. At all frequencies, there is at least one order of magnitude between the ALNM and the AHNM; at high frequencies (> 1Hz) this extends to 2 orders of magnitude. This study provides remarkable confirmation of the capability of modern strong motion accelerometers to record low-amplitude ground motions with seismic observation quality. In particular, an accelerometric station operating at the ALNM is capable of recording the full spectrum of near source earthquakes, out to 100 km, down to M2. Of particular interest for the SED, this study provides acceptable noise limits for candidate sites for the on-going Strong Motion Network modernisation.

  17. Vibro-Shock Dynamics Analysis of a Tandem Low Frequency Resonator—High Frequency Piezoelectric Energy Harvester

    Directory of Open Access Journals (Sweden)

    Darius Žižys

    2017-04-01

    Full Text Available Frequency up-conversion is a promising technique for energy harvesting in low frequency environments. In this approach, abundantly available environmental motion energy is absorbed by a Low Frequency Resonator (LFR which transfers it to a high frequency Piezoelectric Vibration Energy Harvester (PVEH via impact or magnetic coupling. As a result, a decaying alternating output signal is produced, that can later be collected using a battery or be transferred directly to the electric load. The paper reports an impact-coupled frequency up-converting tandem setup with different LFR to PVEH natural frequency ratios and varying contact point location along the length of the harvester. RMS power output of different frequency up-converting tandems with optimal resistive values was found from the transient analysis revealing a strong relation between power output and LFR-PVEH natural frequency ratio as well as impact point location. Simulations revealed that higher power output is obtained from a higher natural frequency ratio between LFR and PVEH, an increase of power output by one order of magnitude for a doubled natural frequency ratio and up to 150% difference in power output from different impact point locations. The theoretical results were experimentally verified.

  18. Systematic errors in the determination of the spectroscopic g-factor in broadband ferromagnetic resonance spectroscopy: A proposed solution

    Science.gov (United States)

    Gonzalez-Fuentes, C.; Dumas, R. K.; García, C.

    2018-01-01

    A theoretical and experimental study of the influence of small offsets of the magnetic field (δH) on the measurement accuracy of the spectroscopic g-factor (g) and saturation magnetization (Ms) obtained by broadband ferromagnetic resonance (FMR) measurements is presented. The random nature of δH generates systematic and opposite sign deviations of the values of g and Ms with respect to their true values. A δH on the order of a few Oe leads to a ˜10% error of g and Ms for a typical range of frequencies employed in broadband FMR experiments. We propose a simple experimental methodology to significantly minimize the effect of δH on the fitted values of g and Ms, eliminating their apparent dependence in the range of frequencies employed. Our method was successfully tested using broadband FMR measurements on a 5 nm thick Ni80Fe20 film for frequencies ranging between 3 and 17 GHz.

  19. Detection in shallow water using broadband-DORT

    Science.gov (United States)

    Fromm, David M.; Gaumond, Charles F.; Lingevitch, Joseph F.; Gauss, Roger C.; Menis, Richard

    2003-10-01

    The decomposition of the time-reversal operator (DORT) [Prada et al., J. Acoust. Soc. Am. 99, 2067-2076 (1996)] has been extended into a coherent, broadband method. Broadband DORT has also been shown to isolate resolvable scatterers at various depths and ranges in a bistatic, active sonar in shallow water. Results are shown from the application of DORT to sea data taken in an area south of Hudson Canyon off the New Jersey coast during Geoclutter II. The vertical source/receiver array with 56 hydrophones spanning the water column was operated between 3.0 and 3.5 kHz. The elements were divided into four groups, with each group acting as a coherent, broadside source. Two methods were used for exciting the separate channels. One method was the use of subsequent LFMs and the other was the use of simultaneous transmission of four pseudorandom-noise signals. The target was a midwater column echo-repeater. Results are compared with modeling based on in situ environmental measurements during the experiment. [The authors acknowledge signal-processing expertise from Dr. Ning Xiang, University of Mississippi, and ENS Alan Meyer, LLNL, support from Dr. Jeff Simmen, ONR, and assistance from Dr. Charles Holland, ARL/PSU. Work supported by ONR.

  20. Searches for high frequency variations in the 8-B neutrino flux at the Sudbury neutrino observatory

    Energy Technology Data Exchange (ETDEWEB)

    Rielage, Keith [Los Alamos National Laboratory; Seibert, Stanley R [Los Alamos National Laboratory; Hime, Andrew [Los Alamos National Laboratory; Elliott, Steven R [Los Alamos National Laboratory; Stonehill, L C [Los Alamos National Laboratory; Wouters, J M [Los Alamos National Laboratory; Aharmim, B [LAURENTIAN UNIV; Ahmed, S N [QUEEN' S UNIV; Anthony, A E [UNIV OF TEXAS; Barros, N [PORTUGAL; Beier, E W [UNIV OF PA; Bellerive, A [CARLETON UNIV; Belttran, B [UNIV OF ALBERTA; Bergevin, M [LBNL; Biller, S D [UNIV OF OXFORD; Boudjemline, K [CARLETON UNIV; Burritt, T H [UNIV OF WASHINGTON; Cai, B [QUEEN' S UNIV; Chan, Y D [LBNL; Chauhan, D [LAURENTIAN UNIV; Chen, M [QUEEN' S UNIV; Cleveland, B T [UNIV OF OXFORD; Cox - Mobrand, G A [UNIV OF WASHINGTON; Dai, X [QUEEN' S UNIV; Deng, H [UNIV OF PA; Detwiler, J [LBNL; Dimarco, M [QUEEN' S UNIV; Doe, P J [UNIV OF WASHINGTON; Drouin, P - L [CARLTON UNIV; Duba, C A [UNIV OF WASHINGTON; Duncan, F A [SNOLAB, SUDBURY; Dunford, M [UNIV OF PA; Earle, E D [QUEEN' S UNIV; Evans, H C [QUEEN' S UNIV; Ewan, G T [QUEEN' S UNIV; Farine, J [LAURENTTIAN UNIV; Fergani, H [UNIV OF OXFORD; Fleurot, F [LAURENTIAN UNIV; Ford, R J [SNOLAB, SUDBURY; Formaggilo, J A [MASSACHUSETTS INST. OF TECH.; Gagnon, N [UNIV OF WASHINGTON; Goon, J Tm [LOUISIANA STATE UNIV; Guillian, E [QUEEN' S UNIV; Habib, S [UNIV OF ALBERTA; Hahn, R L [BNL; Hallin, A L [UNIV OF ALBERTA; Hallman, E D [LAURENTIAN UNIV; Harvey, P J [QUEEN' S UNIV; Hazama, R [UNIV OF WASHINGTON; Heintzelman, W J [UNIV OF PA; Heise, J [SNOLAB, SUDBURY; Helmer, R L [TRIUMF; Howard, C [UNIV OF ALBERTA; Howe, M A [UNIV OF WASHINGTON; Huang, M [UNIV OF TEXAS; Jamieson, B [UNIV OF BRITISH COLUMBIA; Jelley, N A [UNIV OF OXFORD; Keeter, K J [SNOLAB, SUDBURY; Klein, J R [UNIV OF TEXAS; Kos, M [QUEEN' S UNIV; Kraus, C [QUEEN' S UNIV; Krauss, C B [UNIV OF ALBERTA; Kutter, T [LOUISIANA STATE UNIV; Kyba, C C M [UNIV OF PA; Law, J [UNIV OF GUELPH; Lawson, I T [SNOLAB, SUDBURY; Lesko, K T [LBNL; Leslie, J R [QUEEN' S UNIV; Loach, J C [UNIV OF OXFORD; Maclellan, R [QUEEN' S UNIV; Majerus, S [UNIV OF OXFORD; Mak, H B [QUEEN' S UNIV; Maneira, J [PORTUGAL; Martin, R [QUEEN' S UNIV; Mccauley, N [UNIV OF PA; Mc Donald, A B [QUEEN' S UNIV; Mcgee, S [UNIV OF WASHINGTON; Miffin, C [CARLETON UNIV; Miller, M L [MASSACHUSETTS INST. OF TECH.; Monreal, B [MASSACHUSETTS INST. OF TECH.; Monroe, J [MASSACHUSETTS INST. OF TECH; Morissette, B [SNOLAB, SUDBURY; Nickel, B G [UNIV OF GUELPH; Noble, A J [QUEEN' S UNIV; O' Keeffe, H M [UNIV OF OXFORD; Oblath, N S [UNIV OF WASHINGTON; Orebi Gann, G D [UNIV OF OXFORD; Oser, S M [UNIV OF BRITISH COLUMBIA; Ott, R A [MASSACHUSETTS INST. OF TECH.; Peeters, S J M [UNIV OF OXFORD; Poon, A W P [LBNL; Prior, G [LBNL; Reitzner, S D [UNIV OF GUELPH; Robertson, B C [QUEEN' S UNIV; Robertson, R G H [UNIV OF WASHINGTON; Rollin, E [CARLETON UNIV; Schwendener, M H [LAURENTIAN UNIV; Secrest, J A [UNIV OF PA; Seibert, S R [UNIV OF TEXAS; Simard, O [CARLETON UNIV; Sinclair, D [CARLETON UNIV; Sinclair, L [CARLETON UNIV; Skensved, P [QUEEN' S UNIV; Sonley, T J [MASSACHUSETTS INST. OF TECH.; Tesic, G [CARLETON UNIV; Tolich, N [UNIV OF WASHINGTON; Tsui, T [UNIV OF BRITISH COLUMBIA; Tunnell, C D [UNIV OF TEXAS; Van Berg, R [UNIV OF PA; Van Devender, B A [UNIV OF WASHINGTON; Virtue, C J [LAURENTIAN UNIV; Wall, B L [UNIV OF WASHINGTON; Waller, D [CARLETON UNIV; Wan Chan Tseung, H [UNIV OF OXFORD; West, N [UNIV OF OXFORD; Wilkerson, J F [UNIV OF WASHINGTON; Wilson, J R [UNIV OF OXFORD; Wright, A [QUEEN' S UNIV; Yeh, M [BNL; Zhang, F [CARLETON UNIV; Zuber, K [UNIV OF OXFORD

    2009-01-01

    We have peformed three searches for high-frequency signals in the solar neutrino flux measured by the Sudbury Neutrino Observatory (SNO), motivated by the possibility that solar g-mode oscillations could affect the production or propagation of solar {sup 8}B neutrinos. The first search looked for any significant peak in the frequency range l/day to 144/day, with a sensitivity to sinusoidal signals with amplitudes of 12% or greater. The second search focused on regions in which g-mode signals have been claimed by experiments aboard the SoHO satellite, and was sensitive to signals with amplitudes of 10% or greater. The third search looked for extra power across the entire frequency band. No statistically significant signal was detected in any of the three searches.

  1. High-resolution imaging methods in array signal processing

    DEFF Research Database (Denmark)

    Xenaki, Angeliki

    in active sonar signal processing for detection and imaging of submerged oil contamination in sea water from a deep-water oil leak. The submerged oil _eld is modeled as a uid medium exhibiting spatial perturbations in the acoustic parameters from their mean ambient values which cause weak scattering...... of the incident acoustic energy. A highfrequency active sonar is selected to insonify the medium and receive the backscattered waves. High-frequency acoustic methods can both overcome the optical opacity of water (unlike methods based on electromagnetic waves) and resolve the small-scale structure...... of the submerged oil field (unlike low-frequency acoustic methods). The study shows that high-frequency acoustic methods are suitable not only for large-scale localization of the oil contamination in the water column but also for statistical characterization of the submerged oil field through inference...

  2. Application of small-size antennas for estimation of angles of arrival of HF signals scattered by ionospheric irregularities

    Science.gov (United States)

    Guo, Qiang; Galushko, Volodymyr G.; Zalizovski, Andriy V.; Kashcheyev, Sergiy B.; Zheng, Yu

    2018-05-01

    A modification of the Doppler Interferometry Technique is suggested to enable estimating angles of arrival of comparatively broadband HF signals scattered by random irregularities of the ionospheric plasma with the use of small-size weakly directional antennas. The technique is based on the measurements of cross-spectra phases of the probe radiation recorded at least in three spatially separated points. The developed algorithm has been used to investigate the angular and frequency-time characteristics of HF signals propagating at frequencies above the maximum usable one (MUF) for the direct radio path Moscow-Kharkiv. The received signal spectra show presence of three families of spatial components attributed, respectively, to scattering by plasma irregularities near the middle point of the radio path, ground backscatter signals and scattering of the sounding signals by the intense plasma turbulence associated with auroral activations. It has been shown that the regions responsible for the formation of the third family components are located well inside the auroral oval. The drift velocity and direction of the auroral ionosphere plasma have been determined. The obtained estimates are consistent with the classical conception of the ionospheric plasma convection at high latitudes and do not contradict the results of investigations of the auroral ionosphere dynamics using the SuperDARN network.

  3. Flexible GaN for High Performance, Strainable Radio Frequency Devices (Postprint)

    Science.gov (United States)

    2017-11-02

    wireless systems where consumers will benefit significantly from the high power densities achievable in GaN devices.[8] Further complicating the...future strainable and conformal devices for transmission of radio-frequency (RF) signals over large distances for more efficient wireless communication... power density of traditional RF amplifier materials at different frequencies and wireless generation bands, as well as an image of the flexible GaN

  4. Influence of RZ and NRZ signal format on the high-speed performance of gain-clamped semiconductor optical amplifiers

    DEFF Research Database (Denmark)

    Fjelde, Tina; Wolfson, David; Kloch, Allan

    2000-01-01

    High-speed experiments show that the influence from the limited relaxation frequency of GC-SOAs that severely degrades the performance for NRZ signals is reduced by using RZ signals, thus resulting in a higher input power dynamic range.......High-speed experiments show that the influence from the limited relaxation frequency of GC-SOAs that severely degrades the performance for NRZ signals is reduced by using RZ signals, thus resulting in a higher input power dynamic range....

  5. The monterey bay broadband ocean bottom seismic observatory

    Directory of Open Access Journals (Sweden)

    R. Uhrhammer

    2006-06-01

    Full Text Available We report on the installation of a long-term buried ocean-floor broadband seismic station (MOBB in Monterey Bay, California (USA, 40km off-shore, at a water depth of 1000 m. The station was installed in April 2002 using a ship and ROV, in a collaborative effort between the Monterey Bay Aquarium Research Institute (MBARI and the Berkeley Seismological Laboratory (BSL. The station is located on the western side of the San Gregorio Fault, a major fault in the San Andreas plate boundary fault system. In addition to a 3-component CMG-1T seismometer package, the station comprises a current meter and Differential Pressure Gauge, both sampled at high-enough frequency (1 Hz to allow the study of relations between background noise on the seismometers and ocean waves and currents. The proximity of several land-based broadband seismic stations of the Berkeley Digital Seismic Network allows insightful comparisons of land/ocean background seismic noise at periods relevant to regional and teleseismic studies. The station is currently autonomous. Recording and battery packages are exchanged every 3 months during scheduled one day dives. Ultimately, this station will be linked to shore using continuous telemetry (cable and/or buoy and will contribute to the earthquake notification system in Northern California. We present examples of earthquake and noise data recorded during the first 6 months of operation of MOBB. Lessons learned from these and continued recordings will help understand the nature and character of background noise in regional off-shore environments and provide a reference for the installation of future off-shore temporary and permanent broadband seismic stations.

  6. Efficacy of high frequency ultrasound in postoperative evaluation of carpal tunnel syndrome treatment

    Directory of Open Access Journals (Sweden)

    Katarzyna Kapuścińska

    2016-03-01

    Full Text Available Carpal tunnel syndrome (CTS is the most common entrapment neuropathy and a frequent cause of sick leave because of work-related hand overload. The main treatment is operation. Aim: The aim of the study is to assess the usefulness of high frequency ultrasound in the postoperative evaluation of CTS treatment efficacy. Material and methods: Sixty-two patients (50 women and 12 men aged 28–70, mean age 55.2 underwent surgical treatment of CTS. Ultrasound examinations of the wrist in all carpal tunnel sufferers were performed 3 months after the procedure with the use of a high frequency broadband linear array transducer (6–18 MHz, using 18 MHz band of MyLab 70/Esaote. On the basis of the collected data, the author has performed multiple analyses to confirm the usefulness of ultrasound imaging for postoperative evaluation of CTS treatment efficacy. Results: Among all 62 patients, 3 months after surgical median nerve decompression: in 40 patients, CTS symptoms subsided completely, and sonographic evaluation did not show median nerve entrapment signs; in 9 patients, CTS symptoms persisted or exacerbated, and ultrasound proved nerve compression revealing preserved flexor retinaculum fibers; in 13 patients, scar tissue symptoms occurred, and in 5 of them CTS did not subside completely (although ultrasound showed no signs of compression. Conclusions: Ultrasound imaging with the use of a high frequency transducer is a valuable diagnostic tool for postoperative assessment of CTS treatment efficacy.

  7. Active Control of High-Speed Free Jets Using High-Frequency Excitation

    Science.gov (United States)

    Upadhyay, Puja

    global suppression of turbulence intensities for all axial locations, also evidenced by a longer potential core and overall reduced jet spreading. The resulting impact on the noise signature is estimated via far-field acoustic measurements. Noise reduction was observed at low to moderate frequencies for all observation angles. Direct comparison of these results with that of steady microjet injection revealed some notable differences in the initial development of streamwise vorticity and the redistribution of peak turbulence in the azimuthal direction. However, despite significant differences in the near nozzle aerodynamics, the downstream evolution of the jet appeared to approach near similar conditions with both high-frequency and steady microjet injection. Moreover, the impact on far-field noise was also comparable between the two injection methods as well as with others reported in the literature. Finally, for jets at higher Mach numbers and elevated temperatures, the effect of control was observed to vary with jet conditions. While the impact of the two control mechanisms were fairly comparable on non-shock containing jets, high-frequency forcing was observed to produce significantly larger reductions in screech and broadband shock-associated noise (BBSN) at select under-expanded jet conditions. The observed variations in control effects at different jet conditions call for further investigation.

  8. Note: A flexible light emitting diode-based broadband transient-absorption spectrometer

    Science.gov (United States)

    Gottlieb, Sean M.; Corley, Scott C.; Madsen, Dorte; Larsen, Delmar S.

    2012-05-01

    This Note presents a simple and flexible ns-to-ms transient absorption spectrometer based on pulsed light emitting diode (LED) technology that can be incorporated into existing ultrafast transient absorption spectrometers or operate as a stand-alone instrument with fixed-wavelength laser sources. The LED probe pulses from this instrument exhibit excellent stability (˜0.5%) and are capable of producing high signal-to-noise long-time (>100 ns) transient absorption signals either in a broadband multiplexed (spanning 250 nm) or in tunable narrowband (20 ns) operation. The utility of the instrument is demonstrated by measuring the photoinduced ns-to-ms photodynamics of the red/green absorbing fourth GMP phosphodiesterase/adenylyl cyclase/FhlA domain of the NpR6012 locus of the nitrogen-fixing cyanobacterium Nostoc punctiforme.

  9. Response of resonant gravitational wave detectors to damped sinusoid signals

    International Nuclear Information System (INIS)

    Pai, A; Celsi, C; Pallottino, G V; D'Antonio, S; Astone, P

    2007-01-01

    Till date, the search for burst signals with resonant gravitational wave (GW) detectors has been done using the δ-function approximation for the signal, which was reasonable due to the very small bandwidth of these detectors. However, now with increased bandwidth (of the order of 10 or more Hz) and with the possibility of comparing results with interferometric GW detectors (broad-band), it is very important to exploit the resonant detectors' capability to detect also signals with specific wave shapes. As a first step, we present a study of the response of resonant GW detectors to damped sinusoids with given frequency and decay time and report on the development of a filter matched to these signals. This study is a preliminary step towards the comprehension of the detector response and of the filtering for signals such as the excitation of stellar quasi-normal modes

  10. Overview of frequency bandwidth determination techniques of useful signal in case of leaks detection by correlation method

    International Nuclear Information System (INIS)

    Faerman, V A; Avramchuk, V S; Luneva, E E

    2014-01-01

    In this paper an overview of useful signal detection methods on the background of intense noise and limits determination methods of useful signal is presented. The following features are considered: peculiarities of usage of correlation analysis, cross-amplitude spectrum, coherence function, cross-phase spectrum, time-frequency correlation function in case of frequency limits determination as well as leaks detection in pipelines. The possibility of using time-frequency correlation function for solving above named issues is described. Time- frequency correlation function provides information about the signals correlation for each of the investigated frequency bands. Data about location of peaks on the surface plot of a time- frequency correlation function allows making an assumption about the spectral composition of useful signal and its frequency boundaries

  11. Broadband characteristics of vibration energy harvesting using one-dimensional phononic piezoelectric cantilever beams

    Energy Technology Data Exchange (ETDEWEB)

    Chen Zhongsheng, E-mail: czs_study@sina.com [Key Laboratory of Science and Technology on Integrated Logistics Support, College of Mechatronic Engineering and Automation, National University of Defense Technology, Changsha, Hunan 410073 (China); Yang Yongmin; Lu Zhimiao; Luo Yanting [Key Laboratory of Science and Technology on Integrated Logistics Support, College of Mechatronic Engineering and Automation, National University of Defense Technology, Changsha, Hunan 410073 (China)

    2013-02-01

    Nowadays broadband vibration energy harvesting using piezoelectric effect has become a research hotspot. The innovation in this paper is the widening of the resonant bandwidth of a piezoelectric harvester based on phononic band gaps, which is called one-dimensional phononic piezoelectric cantilever beams (PPCBs). Broadband characteristics of one-dimensional PPCBs are analyzed deeply and the vibration band gap can be calculated. The effects of different parameters on the vibration band gap are presented by both numerical and finite element simulations. Finally experimental tests are conducted to validate the proposed method. It can be concluded that it is feasible to use the PPCB for broadband vibration energy harvesting and there should be a compromise among related parameters for low-frequency vibrations.

  12. Broadband characteristics of vibration energy harvesting using one-dimensional phononic piezoelectric cantilever beams

    International Nuclear Information System (INIS)

    Chen Zhongsheng; Yang Yongmin; Lu Zhimiao; Luo Yanting

    2013-01-01

    Nowadays broadband vibration energy harvesting using piezoelectric effect has become a research hotspot. The innovation in this paper is the widening of the resonant bandwidth of a piezoelectric harvester based on phononic band gaps, which is called one-dimensional phononic piezoelectric cantilever beams (PPCBs). Broadband characteristics of one-dimensional PPCBs are analyzed deeply and the vibration band gap can be calculated. The effects of different parameters on the vibration band gap are presented by both numerical and finite element simulations. Finally experimental tests are conducted to validate the proposed method. It can be concluded that it is feasible to use the PPCB for broadband vibration energy harvesting and there should be a compromise among related parameters for low-frequency vibrations.

  13. Observation of High-Frequency Electrostatic Waves in the Vicinity of the Reconnection Ion Diffusion Region by the Spacecraft of the Magnetospheric Multiscale (MMS) Mission

    Science.gov (United States)

    Zhou, M.; Ashour-Abdalla, M.; Berchem, J.; Walker, R. J.; Liang, H.; El-Alaoui, M.; Goldstein, M. L.; Lindqvist, P.-A.; Marklund, G.; Khotyaintsev, Y. V.; hide

    2016-01-01

    We report Magnetospheric Multiscale observations of high-frequency electrostatic waves in the vicinity of the reconnection ion diffusion region on the dayside magnetopause. The ion diffusion region is identified during two magnetopause crossings by the Hall electromagnetic fields, the slippage of ions with respect to the magnetic field, and magnetic energy dissipation. In addition to electron beam modes that have been previously detected at the separatrix on the magnetospheric side of the magnetopause, we report, for the first time, the existence of electron cyclotron harmonic waves at the magnetosheath separatrix. Broadband waves between the electron cyclotron and electron plasma frequencies, which were probably generated by electron beams, were found within the magnetopause current sheet. Contributions by these high-frequency waves to the magnetic energy dissipation were negligible in the diffusion regions as compared to those of lower-frequency waves.

  14. Broadband seismic deployments in East Antarctica: IPY contribution to monitoring the Earth’s interiors

    Directory of Open Access Journals (Sweden)

    Masaki Kanao

    2014-06-01

    Full Text Available “Deployment of broadband seismic stations on the Antarctica continent” is an ambitious project to improve the spatial resolution of seismic data across the Antarctic Plate and surrounding regions. Several international collaborative programs for the purpose of geomonitoring were conducted in Antarctica during the International Polar Year (IPY 2007-2008. The Antarctica’s GAmburtsev Province (AGAP; IPY #147, the GAmburtsev Mountain SEISmic experiment (GAMSEIS, a part of AGAP, and the Polar Earth Observing Network (POLENET; IPY #185 were major contributions in establishing a geophysical network in Antarctica. The AGAP/GAMSEIS project was an internationally coordinated deployment of more than 30 broadband seismographs over the crest of the Gambursev Mountains (Dome-A, Dome-C and Dome-F area. The investigations provide detailed information on crustal thickness and mantle structure; provide key constraints on the origin of the Gamburtsev Mountains; and more broadly on the structure and evolution of the East Antarctic craton and subglacial environment. From GAMSEIS and POLENET data obtained, local and regional seismic signals associated with ice movements, oceanic loading, and local meteorological variations were recorded together with a significant number of teleseismic events. In this chapter, in addition to the Earth’s interiors, we will demonstrate some of the remarkable seismic signals detected during IPY that illustrate the capabilities of broadband seismometers to study the sub-glacial environment, particularly at the margins of Antarctica. Additionally, the AGAP and POLENET stations have an important role in the Federation of Digital Seismographic Network (FDSN in southern high latitude.

  15. The analysis and interpretation of very-long-period seismic signals on volcanoes

    Science.gov (United States)

    Sindija, Dinko; Neuberg, Jurgen; Smith, Patrick

    2017-04-01

    The study of very long period (VLP) seismic signals became possible with the widespread use of broadband instruments. VLP seismic signals are caused by transients of pressure in the volcanic edifice and have periods ranging from several seconds to several minutes. For the VLP events recorded in March 2012 and 2014 at Soufriere Hills Volcano, Montserrat, we model the ground displacement using several source time functions: a step function using Richards growth equation, Küpper wavelet, and a damped sine wave to which an instrument response is then applied. This way we get a synthetic velocity seismogram which is directly comparable to the data. After the full vector field of ground displacement is determined, we model the source mechanism to determine the relationship between the source mechanism and the observed VLP waveforms. Emphasis of the research is on how different VLP waveforms are related to the volcano environment and the instrumentation used and on the processing steps in this low frequency band to get most out of broadband instruments.

  16. Adaptive frequency-difference matched field processing for high frequency source localization in a noisy shallow ocean.

    Science.gov (United States)

    Worthmann, Brian M; Song, H C; Dowling, David R

    2017-01-01

    Remote source localization in the shallow ocean at frequencies significantly above 1 kHz is virtually impossible for conventional array signal processing techniques due to environmental mismatch. A recently proposed technique called frequency-difference matched field processing (Δf-MFP) [Worthmann, Song, and Dowling (2015). J. Acoust. Soc. Am. 138(6), 3549-3562] overcomes imperfect environmental knowledge by shifting the signal processing to frequencies below the signal's band through the use of a quadratic product of frequency-domain signal amplitudes called the autoproduct. This paper extends these prior Δf-MFP results to various adaptive MFP processors found in the literature, with particular emphasis on minimum variance distortionless response, multiple constraint method, multiple signal classification, and matched mode processing at signal-to-noise ratios (SNRs) from -20 to +20 dB. Using measurements from the 2011 Kauai Acoustic Communications Multiple University Research Initiative experiment, the localization performance of these techniques is analyzed and compared to Bartlett Δf-MFP. The results show that a source broadcasting a frequency sweep from 11.2 to 26.2 kHz through a 106 -m-deep sound channel over a distance of 3 km and recorded on a 16 element sparse vertical array can be localized using Δf-MFP techniques within average range and depth errors of 200 and 10 m, respectively, at SNRs down to 0 dB.

  17. High-power broad-band tunable microwave oscillator, driven by REB in plasma

    Energy Technology Data Exchange (ETDEWEB)

    Kuzelev, M V; Loza, O T; Ponomarev, A V; Rukhadze, A A; Strel` kov, P S; Shkvarunets, A G; Ulyanov, D K [General Physics Inst. of Russian Academy of Sciences, Moscow (Russian Federation)

    1997-12-31

    The radiation spectra of a plasma relativistic broad-band microwave oscillator were measured. A hollow relativistic electron beam (REB) was injected into the plasma waveguide, consisting of annular plasma in a circular metal waveguide. The radiation spectra were measured by means of a calorimeter-spectrometer with a large cross section in the band of 3-39 GHz. The mean frequency was tunable in the band of 20-27 GHz, the spectrum width was 5-25 GHz with a power level of 40-85 MW. Calculations were carried out based on non-linear theory, taking into account electromagnetic noise amplification due to REB injection into the plasma waveguide. According to the theory the radiation regime should change from the single-particle regime to the collective regime when the plasma density and the gap between the annular plasma and REB are increased. Comparison of the experimental results with the non-linear theory explains some peculiarities of the measured spectrum. (author). 4 figs., 2 refs.

  18. A calibrated, broadband antenna for plasma RF emission measurements below 1 GHz

    International Nuclear Information System (INIS)

    Spence, P.D.; Rosenberg, D.; Roth, J.R.

    1984-01-01

    A constant impedance, constant aperture antenna can make possible broadband plasma RF emission measurements which yield relative and absolute power levels. However, good technique must be followed for the immersion of such an RF probe into plasma radiation. The authors have used a complementary conical spiral antenna to observe plasma RF emission over the frequency range 100 ≤ν≤ 1200 MHz. The RF emission was emitted by a modified Penning discharge. The RF emission from the discharge typically exhibits harmonic structure over a broad frequency range, necessitating a broadband antenna with a flat frequency response curve to allow detailed spectral analysis. The antenna consists of two metal strips of approximately uniform width wound helically on a cone made of Lexan plastic. Since the antenna is a balanced network, a balun is employed to make the transition to a 50-ohm coaxial line. The antenna feed method is critical in maintaining a uniform impedance network. Neglecting stray transmission line effects, the probe circuit for the frequency range 100 ≤ν≤ 500 MHz is 50 ohms due to the spectrum analyzer, paralleled by 291 ohms due to balun magnetization; the combination is fed by a 144 ohm probe aperture

  19. The SCEC Broadband Platform: A Collaborative Open-Source Software Package for Strong Ground Motion Simulation and Validation

    Science.gov (United States)

    Silva, F.; Maechling, P. J.; Goulet, C. A.; Somerville, P.; Jordan, T. H.

    2014-12-01

    The Southern California Earthquake Center (SCEC) Broadband Platform is a collaborative software development project involving geoscientists, earthquake engineers, graduate students, and the SCEC Community Modeling Environment. The SCEC Broadband Platform (BBP) is open-source scientific software that can generate broadband (0-100Hz) ground motions for earthquakes, integrating complex scientific modules that implement rupture generation, low and high-frequency seismogram synthesis, non-linear site effects calculation, and visualization into a software system that supports easy on-demand computation of seismograms. The Broadband Platform operates in two primary modes: validation simulations and scenario simulations. In validation mode, the Platform runs earthquake rupture and wave propagation modeling software to calculate seismograms for a well-observed historical earthquake. Then, the BBP calculates a number of goodness of fit measurements that quantify how well the model-based broadband seismograms match the observed seismograms for a certain event. Based on these results, the Platform can be used to tune and validate different numerical modeling techniques. In scenario mode, the Broadband Platform can run simulations for hypothetical (scenario) earthquakes. In this mode, users input an earthquake description, a list of station names and locations, and a 1D velocity model for their region of interest, and the Broadband Platform software then calculates ground motions for the specified stations. Working in close collaboration with scientists and research engineers, the SCEC software development group continues to add new capabilities to the Broadband Platform and to release new versions as open-source scientific software distributions that can be compiled and run on many Linux computer systems. Our latest release includes 5 simulation methods, 7 simulation regions covering California, Japan, and Eastern North America, the ability to compare simulation results

  20. Control of broadband optically generated ultrasound pulses using binary amplitude holograms.

    Science.gov (United States)

    Brown, Michael D; Jaros, Jiri; Cox, Ben T; Treeby, Bradley E

    2016-04-01

    In this work, the use of binary amplitude holography is investigated as a mechanism to focus broadband acoustic pulses generated by high peak-power pulsed lasers. Two algorithms are described for the calculation of the binary holograms; one using ray-tracing, and one using an optimization based on direct binary search. It is shown using numerical simulations that when a binary amplitude hologram is excited by a train of laser pulses at its design frequency, the acoustic field can be focused at a pre-determined distribution of points, including single and multiple focal points, and line and square foci. The numerical results are validated by acoustic field measurements from binary amplitude holograms, excited by a high peak-power laser.

  1. New method to estimate the frequency stability of laser signals

    International Nuclear Information System (INIS)

    McFerran, J.J.; Maric, M.; Luiten, A.N.

    2004-01-01

    A frequent challenge in the scientific and commercial use of lasers is the need to determine the frequency stability of the output optical signal. In this article we present a new method to estimate this quantity while avoiding the complexity of the usual technique. The new technique displays the result in terms of the usual time domain measure of frequency stability: the square root Allan variance

  2. GNSS Signal Tracking Performance Improvement for Highly Dynamic Receivers by Gyroscopic Mounting Crystal Oscillator.

    Science.gov (United States)

    Abedi, Maryam; Jin, Tian; Sun, Kewen

    2015-08-31

    In this paper, the efficiency of the gyroscopic mounting method is studied for a highly dynamic GNSS receiver's reference oscillator for reducing signal loss. Analyses are performed separately in two phases, atmospheric and upper atmospheric flights. Results show that the proposed mounting reduces signal loss, especially in parts of the trajectory where its probability is the highest. This reduction effect appears especially for crystal oscillators with a low elevation angle g-sensitivity vector. The gyroscopic mounting influences frequency deviation or jitter caused by dynamic loads on replica carrier and affects the frequency locked loop (FLL) as the dominant tracking loop in highly dynamic GNSS receivers. In terms of steady-state load, the proposed mounting mostly reduces the frequency deviation below the one-sigma threshold of FLL (1σ(FLL)). The mounting method can also reduce the frequency jitter caused by sinusoidal vibrations and reduces the probability of signal loss in parts of the trajectory where the other error sources accompany this vibration load. In the case of random vibration, which is the main disturbance source of FLL, gyroscopic mounting is even able to suppress the disturbances greater than the three-sigma threshold of FLL (3σ(FLL)). In this way, signal tracking performance can be improved by the gyroscopic mounting method for highly dynamic GNSS receivers.

  3. Broadband Faraday isolator.

    Science.gov (United States)

    Berent, Michał; Rangelov, Andon A; Vitanov, Nikolay V

    2013-01-01

    Driving on an analogy with the technique of composite pulses in quantum physics, we theoretically propose a broadband Faraday rotator and thus a broadband optical isolator, which is composed of sequences of ordinary Faraday rotators and achromatic quarter-wave plates rotated at the predetermined angles.

  4. High capacity wireless data links in the W-band using hybrid photonics-electronic techniques for signal generation and detection

    DEFF Research Database (Denmark)

    Vegas Olmos, Juan José; Tafur Monroy, Idelfonso

    2014-01-01

    Seamless convergence of fiber-optic and the wireless networks is of great interest for enabling transparent delivery of broadband services to users in different locations, including both metropolitan and rural areas. Current demand of bandwidth by end-users, especially using mobile devices...... latest findings and experimental results on the W-band, specifically on its 81–86GHz sub-band. These include photonic generation of millimeter-wave carriers and transmission performance of broadband signals on different types of fibers and span lengths....

  5. High frequency modulation circuits based on photoconductive wide bandgap switches

    Science.gov (United States)

    Sampayan, Stephen

    2018-02-13

    Methods, systems, and devices for high voltage and/or high frequency modulation. In one aspect, an optoelectronic modulation system includes an array of two or more photoconductive switch units each including a wide bandgap photoconductive material coupled between a first electrode and a second electrode, a light source optically coupled to the WBGP material of each photoconductive switch unit via a light path, in which the light path splits into multiple light paths to optically interface with each WBGP material, such that a time delay of emitted light exists along each subsequent split light path, and in which the WBGP material conducts an electrical signal when a light signal is transmitted to the WBGP material, and an output to transmit the electrical signal conducted by each photoconductive switch unit. The time delay of the photons emitted through the light path is substantially equivalent to the time delay of the electrical signal.

  6. BROADBAND OBSERVATIONS OF HIGH REDSHIFT BLAZARS

    Energy Technology Data Exchange (ETDEWEB)

    Paliya, Vaidehi S. [Department of Physics and Astronomy, Clemson University, Kinard Lab of Physics, Clemson, SC 29634-0978 (United States); Parker, M. L.; Fabian, A. C. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Stalin, C. S., E-mail: vpaliya@g.clemson.edu [Indian Institute of Astrophysics, Block II, Koramangala, Bangalore-560034 (India)

    2016-07-01

    We present a multi-wavelength study of four high redshift blazars, S5 0014+81 ( z = 3.37), CGRaBS J0225+1846 ( z = 2.69), BZQ J1430+4205 ( z = 4.72), and 3FGL J1656.2−3303 ( z = 2.40) using quasi-simultaneous data from the Swift , Nuclear Spectroscopic Telescope Array ( NuSTAR ) and the Fermi -Large Area Telescope (LAT) and also archival XMM-Newton observations. Other than 3FGL J1656.2−3303, none of the sources were known as γ -ray emitters, and our analysis of ∼7.5 yr of LAT data reveals the first time detection of statistically significant γ -ray emission from CGRaBS J0225+1846. We generate the broadband spectral energy distributions (SED) of all the objects, centering at the epoch of NuSTAR observations and reproduce them using a one-zone leptonic emission model. The optical−UV emission in all the objects can be explained by radiation from the accretion disk, whereas the X-ray to γ -ray windows of the SEDs are found to be dominated by inverse Compton scattering off the broad line region photons. All of them host black holes that are billions of solar masses. Comparing the accretion disk luminosity and the jet power of these sources with a large sample of blazars, we find them to occupy a high disk luminosity–jet power regime. We also investigate the X-ray spectral properties of the sources in detail with a major focus on studying the causes of soft X-ray deficit, a feature generally seen in high redshift radio-loud quasars. We summarize that this feature could be explained based on the intrinsic curvature in the jet emission rather than being due to the external effects predicted in earlier studies, such as host galaxy and/or warm absorption.

  7. Borehole Volumetric Strainmeter Calibration From a Nearby Seismic Broadband Array at Etna Volcano

    Science.gov (United States)

    Currenti, G.; Zuccarello, L.; Bonaccorso, A.; Sicali, A.

    2017-10-01

    Strainmeter and broadband seismic signals have been analyzed jointly with the aim of calibrating a borehole strainmeter at Etna volcano by using a seismo-geodetic technique. Our results reveal a good coherence between the dynamic strains estimated from seismometer data and strains recorded by a dilatometer in a low-frequency range [0.03-0.06 Hz] at the arrival of teleseismic waves. This significant coherence enabled estimating the calibration coefficient and making a comparison with calibration results derived from other methods. In particular, we verified that the proposed approach provides a calibration coefficient that matches the results obtained from the comparison of the recorded strain both with theoretical strain tides and with normal-mode synthetic straingrams. The approach presented here has the advantage of exploiting recorded seismic data, avoiding the use of computed strain from theoretical models.

  8. Note: Demodulation of spectral signal modulated by optical chopper with unstable modulation frequency.

    Science.gov (United States)

    Zhang, Shengzhao; Li, Gang; Wang, Jiexi; Wang, Donggen; Han, Ying; Cao, Hui; Lin, Ling; Diao, Chunhong

    2017-10-01

    When an optical chopper is used to modulate the light source, the rotating speed of the wheel may vary with time and subsequently cause jitter of the modulation frequency. The amplitude calculated from the modulated signal would be distorted when the frequency fluctuations occur. To precisely calculate the amplitude of the modulated light flux, we proposed a method to estimate the range of the frequency fluctuation in the measurement of the spectrum and then extract the amplitude based on the sum of power of the signal in the selected frequency range. Experiments were designed to test the feasibility of the proposed method and the results showed lower root means square error than the conventional way.

  9. Highly efficient and broadband wide-angle holography using patch-dipole nanoantenna reflectarrays.

    Science.gov (United States)

    Yifat, Yuval; Eitan, Michal; Iluz, Zeev; Hanein, Yael; Boag, Amir; Scheuer, Jacob

    2014-05-14

    We demonstrate wide-angle, broadband, and efficient reflection holography by utilizing coupled dipole-patch nanoantenna cells to impose an arbitrary phase profile on the reflected light. High-fidelity images were projected at angles of 45 and 20° with respect to the impinging light with efficiencies ranging between 40-50% over an optical bandwidth exceeding 180 nm. Excellent agreement with the theoretical predictions was found at a wide spectral range. The demonstration of such reflectarrays opens new avenues toward expanding the limits of large-angle holography.

  10. Instantaneous Real-Time Kinematic Decimeter-Level Positioning with BeiDou Triple-Frequency Signals over Medium Baselines.

    Science.gov (United States)

    He, Xiyang; Zhang, Xiaohong; Tang, Long; Liu, Wanke

    2015-12-22

    Many applications, such as marine navigation, land vehicles location, etc., require real time precise positioning under medium or long baseline conditions. In this contribution, we develop a model of real-time kinematic decimeter-level positioning with BeiDou Navigation Satellite System (BDS) triple-frequency signals over medium distances. The ambiguities of two extra-wide-lane (EWL) combinations are fixed first, and then a wide lane (WL) combination is reformed based on the two EWL combinations for positioning. Theoretical analysis and empirical analysis is given of the ambiguity fixing rate and the positioning accuracy of the presented method. The results indicate that the ambiguity fixing rate can be up to more than 98% when using BDS medium baseline observations, which is much higher than that of dual-frequency Hatch-Melbourne-Wübbena (HMW) method. As for positioning accuracy, decimeter level accuracy can be achieved with this method, which is comparable to that of carrier-smoothed code differential positioning method. Signal interruption simulation experiment indicates that the proposed method can realize fast high-precision positioning whereas the carrier-smoothed code differential positioning method needs several hundreds of seconds for obtaining high precision results. We can conclude that a relatively high accuracy and high fixing rate can be achieved for triple-frequency WL method with single-epoch observations, displaying significant advantage comparing to traditional carrier-smoothed code differential positioning method.

  11. Instantaneous Real-Time Kinematic Decimeter-Level Positioning with BeiDou Triple-Frequency Signals over Medium Baselines

    Directory of Open Access Journals (Sweden)

    Xiyang He

    2015-12-01

    Full Text Available Many applications, such as marine navigation, land vehicles location, etc., require real time precise positioning under medium or long baseline conditions. In this contribution, we develop a model of real-time kinematic decimeter-level positioning with BeiDou Navigation Satellite System (BDS triple-frequency signals over medium distances. The ambiguities of two extra-wide-lane (EWL combinations are fixed first, and then a wide lane (WL combination is reformed based on the two EWL combinations for positioning. Theoretical analysis and empirical analysis is given of the ambiguity fixing rate and the positioning accuracy of the presented method. The results indicate that the ambiguity fixing rate can be up to more than 98% when using BDS medium baseline observations, which is much higher than that of dual-frequency Hatch-Melbourne-Wübbena (HMW method. As for positioning accuracy, decimeter level accuracy can be achieved with this method, which is comparable to that of carrier-smoothed code differential positioning method. Signal interruption simulation experiment indicates that the proposed method can realize fast high-precision positioning whereas the carrier-smoothed code differential positioning method needs several hundreds of seconds for obtaining high precision results. We can conclude that a relatively high accuracy and high fixing rate can be achieved for triple-frequency WL method with single-epoch observations, displaying significant advantage comparing to traditional carrier-smoothed code differential positioning method.

  12. High resolution mid-infrared spectroscopy based on frequency upconversion

    DEFF Research Database (Denmark)

    Dam, Jeppe Seidelin; Hu, Qi; Tidemand-Lichtenberg, Peter

    2013-01-01

    signals can be analyzed. The obtainable frequency resolution is usually in the nm range where sub nm resolution is preferred in many applications, like gas spectroscopy. In this work we demonstrate how to obtain sub nm resolution when using upconversion. In the presented realization one object point...... high resolution spectral performance by observing emission from hot water vapor in a butane gas burner....

  13. Design of 20-44 GHz broadband doubler MMIC

    International Nuclear Information System (INIS)

    Li Qin; Wang Zhigong; Li Wei

    2010-01-01

    This paper presents the design and performance of a broadband millimeter-wave frequency doubler MMIC using active 0.15 μm GaAs PHEMT and operating at output frequencies from 20 to 44 GHz. This chip is composed of a single ended-into differential-out active Balun, balanced FETs in push-push configuration, and a distributed amplifier. The MMIC doubler exhibits more than 4 dB conversion gain with 12 dBm of output power, and the fundamental frequency suppression is typically -20 dBc up to 44 GHz. The MMIC works at V DD = 3.5 V, V SS = -3.5 V, I d = 200 mA and the chip size is 1.5 x 1.8 mm 2 . (semiconductor integrated circuits)

  14. Broadband and scalable mobile satellite communication system for future access networks

    Science.gov (United States)

    Ohata, Kohei; Kobayashi, Kiyoshi; Nakahira, Katsuya; Ueba, Masazumi

    2005-07-01

    Due to the recent market trends, NTT has begun research into next generation satellite communication systems, such as broadband and scalable mobile communication systems. One service application objective is to provide broadband Internet access for transportation systems, temporal broadband access networks and telemetries to remote areas. While these are niche markets the total amount of capacity should be significant. We set a 1-Gb/s total transmission capacity as our goal. Our key concern is the system cost, which means that the system should be unified system with diversified services and not tailored for each application. As satellites account for a large portion of the total system cost, we set the target satellite size as a small, one-ton class dry mass with a 2-kW class payload power. In addition to the payload power and weight, the mobile satellite's frequency band is extremely limited. Therefore, we need to develop innovative technologies that will reduce the weight and maximize spectrum and power efficiency. Another challenge is the need for the system to handle up to 50 dB and a wide data rate range of other applications. This paper describes the key communication system technologies; the frequency reuse strategy, multiplexing scheme, resource allocation scheme, and QoS management algorithm to ensure excellent spectrum efficiency and support a variety of services and quality requirements in the mobile environment.

  15. High-frequency, high-intensity photoionization

    Science.gov (United States)

    Reiss, H. R.

    1996-02-01

    Two analytical methods for computing ionization by high-frequency fields are compared. Predicted ionization rates compare well, but energy predictions for the onset of ionization differ radically. The difference is shown to arise from the use of a transformation in one of the methods that alters the zero from which energy is measured. This alteration leads to an apparent energy threshold for ionization that can, especially in the stabilization regime, differ strongly from the laboratory measurement. It is concluded that channel closings in intense-field ionization can occur at high as well as low frequencies. It is also found that the stabilization phenomenon at high frequencies, very prominent for hydrogen, is absent in a short-range potential.

  16. Seismic signal and noise on Europa

    Science.gov (United States)

    Panning, Mark; Stähler, Simon; Bills, Bruce; Castillo Castellanos, Jorge; Huang, Hsin-Hua; Husker, Allen; Kedar, Sharon; Lorenz, Ralph; Pike, William T.; Schmerr, Nicholas; Tsai, Victor; Vance, Steven

    2017-10-01

    Seismology is one of our best tools for detailing interior structure of planetary bodies, and a seismometer is included in the baseline and threshold mission design for the upcoming Europa Lander mission. Guiding mission design and planning for adequate science return, though, requires modeling of both the anticipated signal and noise. Assuming ice seismicity on Europa behaves according to statistical properties observed in Earth catalogs and scaling cumulative seismic moment release to the moon, we can simulate long seismic records and estimate background noise and peak signal amplitudes (Panning et al., 2017). This suggests a sensitive instrument comparable to many broadband terrestrial instruments or the SP instrument from the InSight mission to Mars will be able to record signals, while high frequency geophones are likely inadequate. We extend this analysis to also begin incorporation of spatial and temporal variation due to the tidal cycle, which can help inform landing site selection. We also begin exploration of how chaotic terrane at the bottom of the ice shell and inter-ice heterogeneities (i.e. internal melt structures) may affect anticipated seismic observations using 2D numerical seismic simulations.M. P. Panning, S. C. Stähler, H.-H. Huang, S. D. Vance, S. Kedar, V. C. Tsai, W. T. Pike, R. D. Lorenz, “Expected seismicity and the seismic noise environment of Europa,” J. Geophys. Res., in revision, 2017.

  17. High frequency microseismic noise as possible earthquake precursor

    OpenAIRE

    Ivica Sović; Kristina Šariri; Mladen Živčić

    2013-01-01

    Before an earthquake occurs, microseismic noise in high frequency (HF) range, i.e. 2-25 Hz, is being generated during preparation process. These signals change the microseismic noise and, consequently, the spectrum of microseismic noise. Time variation of spectra recorded at the same seismological station could imply the change of the state of noise source. We propose the image moment analysis approach to objectively compare microseismic noise spectra. The result could be used for earthquake ...

  18. Flexible Gallium Nitride for High-Performance, Strainable Radio-Frequency Devices.

    Science.gov (United States)

    Glavin, Nicholas R; Chabak, Kelson D; Heller, Eric R; Moore, Elizabeth A; Prusnick, Timothy A; Maruyama, Benji; Walker, Dennis E; Dorsey, Donald L; Paduano, Qing; Snure, Michael

    2017-12-01

    Flexible gallium nitride (GaN) thin films can enable future strainable and conformal devices for transmission of radio-frequency (RF) signals over large distances for more efficient wireless communication. For the first time, strainable high-frequency RF GaN devices are demonstrated, whose exceptional performance is enabled by epitaxial growth on 2D boron nitride for chemical-free transfer to a soft, flexible substrate. The AlGaN/GaN heterostructures transferred to flexible substrates are uniaxially strained up to 0.85% and reveal near state-of-the-art values for electrical performance, with electron mobility exceeding 2000 cm 2 V -1 s -1 and sheet carrier density above 1.07 × 10 13 cm -2 . The influence of strain on the RF performance of flexible GaN high-electron-mobility transistor (HEMT) devices is evaluated, demonstrating cutoff frequencies and maximum oscillation frequencies greater than 42 and 74 GHz, respectively, at up to 0.43% strain, representing a significant advancement toward conformal, highly integrated electronic materials for RF applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Squeezed light for the interferometric detection of high-frequency gravitational waves

    Science.gov (United States)

    Schnabel, R.; Harms, J.; Strain, K. A.; Danzmann, K.

    2004-03-01

    The quantum noise of the light field is a fundamental noise source in interferometric gravitational-wave detectors. Injected squeezed light is capable of reducing the quantum noise contribution to the detector noise floor to values that surpass the so-called standard quantum limit (SQL). In particular, squeezed light is useful for the detection of gravitational waves at high frequencies where interferometers are typically shot-noise limited, although the SQL might not be beaten in this case. We theoretically analyse the quantum noise of the signal-recycled laser interferometric gravitational-wave detector GEO 600 with additional input and output optics, namely frequency-dependent squeezing of the vacuum state of light entering the dark port and frequency-dependent homodyne detection. We focus on the frequency range between 1 kHz and 10 kHz, where, although signal recycled, the detector is still shot-noise limited. It is found that the GEO 600 detector with present design parameters will benefit from frequency-dependent squeezed light. Assuming a squeezing strength of -6 dB in quantum noise variance, the interferometer will become thermal noise limited up to 4 kHz without further reduction of bandwidth. At higher frequencies the linear noise spectral density of GEO 600 will still be dominated by shot noise and improved by a factor of 106dB/20dB ap 2 according to the squeezing strength assumed. The interferometer might reach a strain sensitivity of 6 × 10-23 above 1 kHz (tunable) with a bandwidth of around 350 Hz. We propose a scheme to implement the desired frequency-dependent squeezing by introducing an additional optical component into GEO 600's signal-recycling cavity.

  20. Squeezed light for the interferometric detection of high-frequency gravitational waves

    International Nuclear Information System (INIS)

    Schnabel, R; Harms, J; Strain, K A; Danzmann, K

    2004-01-01

    The quantum noise of the light field is a fundamental noise source in interferometric gravitational-wave detectors. Injected squeezed light is capable of reducing the quantum noise contribution to the detector noise floor to values that surpass the so-called standard quantum limit (SQL). In particular, squeezed light is useful for the detection of gravitational waves at high frequencies where interferometers are typically shot-noise limited, although the SQL might not be beaten in this case. We theoretically analyse the quantum noise of the signal-recycled laser interferometric gravitational-wave detector GEO 600 with additional input and output optics, namely frequency-dependent squeezing of the vacuum state of light entering the dark port and frequency-dependent homodyne detection. We focus on the frequency range between 1 kHz and 10 kHz, where, although signal recycled, the detector is still shot-noise limited. It is found that the GEO 600 detector with present design parameters will benefit from frequency-dependent squeezed light. Assuming a squeezing strength of -6 dB in quantum noise variance, the interferometer will become thermal noise limited up to 4 kHz without further reduction of bandwidth. At higher frequencies the linear noise spectral density of GEO 600 will still be dominated by shot noise and improved by a factor of 10 6dB/20dB ∼ 2 according to the squeezing strength assumed. The interferometer might reach a strain sensitivity of 6 x 10 -23 above 1 kHz (tunable) with a bandwidth of around 350 Hz. We propose a scheme to implement the desired frequency-dependent squeezing by introducing an additional optical component into GEO 600's signal-recycling cavity

  1. Broadband Rotational Spectroscopy

    Science.gov (United States)

    Pate, Brooks

    2014-06-01

    The past decade has seen several major technology advances in electronics operating at microwave frequencies making it possible to develop a new generation of spectrometers for molecular rotational spectroscopy. High-speed digital electronics, both arbitrary waveform generators and digitizers, continue on a Moore's Law-like development cycle that started around 1993 with device bandwidth doubling about every 36 months. These enabling technologies were the key to designing chirped-pulse Fourier transform microwave (CP-FTMW) spectrometers which offer significant sensitivity enhancements for broadband spectrum acquisition in molecular rotational spectroscopy. A special feature of the chirped-pulse spectrometer design is that it is easily implemented at low frequency (below 8 GHz) where Balle-Flygare type spectrometers with Fabry-Perot cavity designs become technologically challenging due to the mirror size requirements. The capabilities of CP-FTMW spectrometers for studies of molecular structure will be illustrated by the collaborative research effort we have been a part of to determine the structures of water clusters - a project which has identified clusters up to the pentadecamer. A second technology trend that impacts molecular rotational spectroscopy is the development of high power, solid state sources in the mm-wave/THz regions. Results from the field of mm-wave chirped-pulse Fourier transform spectroscopy will be described with an emphasis on new problems in chemical dynamics and analytical chemistry that these methods can tackle. The third (and potentially most important) technological trend is the reduction of microwave components to chip level using monolithic microwave integrated circuits (MMIC) - a technology driven by an enormous mass market in communications. Some recent advances in rotational spectrometer designs that incorporate low-cost components will be highlighted. The challenge to the high-resolution spectroscopy community - as posed by Frank De

  2. Determination of High-Frequency d- and q-axis Inductances for Surface-Mounted Permanent-Magnet Synchronous Machines

    DEFF Research Database (Denmark)

    Lu, Kaiyuan; Vetuschi, M.; Rasmussen, Peter Omand

    2010-01-01

    This paper presents a reliable method for the experimental determination of high-frequency d- and q -axis inductances for surface-mounted permanent-magnet synchronous machines (SMPMSMs). Knowledge of the high-frequency d- and q-axis inductances plays an important role in the efficient design...... of sensorless controllers using high-frequency signal injection techniques. The proposed method employs a static locked-rotor test using an ac +dc power supply. By injecting a high-frequency rotating voltage vector into the machine, the d- and q-axis inductances may simultaneously be determined with no need...

  3. Analysis and design of broadband U-slot cut rectangular microstrip ...

    Indian Academy of Sciences (India)

    AMIT A DESHMUKH

    2017-07-15

    Jul 15, 2017 ... Abstract. Broadband microstrip antenna using variations of U-slot has been widely reported. However, in most of the reported work, an in-depth explanation about the mode introduced by U-slot and procedure to design. U-slot cut antennas at any given frequency is not explained. In this paper, first an ...

  4. Broadband infrared absorption enhancement by electroless-deposited silver nanoparticles

    DEFF Research Database (Denmark)

    Gritti, Claudia; Raza, Søren; Kadkhodazadeh, Shima

    2017-01-01

    Decorating semiconductor surfaces with plasmonic nanoparticles (NPs) is considered a viable solution for enhancing the absorptive properties of photovoltaic and photodetecting devices. We propose to deposit silver NPs on top of a semiconductor wafer by a cheap and fast electroless plating technique....... Optical characterization confirms that the random array of electroless-deposited NPs improves absorption by up to 20% in a broadband of nearinfrared frequencies from the bandgap edge to 2000 nm. Due to the small filling fraction of particles, the reflection in the visible range is practically unchanged......, which points to the possible applications of such deposition method for harvesting photons in nanophotonics and photovoltaics. The broadband absorption is a consequence of the resonant behavior of particles with different shapes and sizes, which strongly localize the incident light at the interface...

  5. Effects of the major sudden stratospheric warming event of 2009 on the subionospheric very low frequency/low frequency radio signals

    Science.gov (United States)

    Pal, S.; Hobara, Y.; Chakrabarti, S. K.; Schnoor, P. W.

    2017-07-01

    This paper presents effects of the major sudden stratospheric warming (SSW) event of 2009 on the subionospheric very low frequency/low frequency (VLF/LF) radio signals propagating in the Earth-ionosphere waveguide. Signal amplitudes from four transmitters received by VLF/LF radio networks of Germany and Japan corresponding to the major SSW event are investigated for possible anomalies and atmospheric influence on the high- to middle-latitude ionosphere. Significant anomalous increase or decrease of nighttime and daytime amplitudes of VLF/LF signals by ˜3-5 dB during the SSW event have been found for all propagation paths associated with stratospheric temperature rise at 10 hPa level. Increase or decrease in VLF/LF amplitudes during daytime and nighttime is actually due to the modification of the lower ionospheric boundary conditions in terms of electron density and electron-neutral collision frequency profiles and associated modal interference effects between the different propagating waveguide modes during the SSW period. TIMED/SABER mission data are also used to investigate the upper mesospheric conditions over the VLF/LF propagation path during the same time period. We observe a decrease in neutral temperature and an increase in pressure at the height of 75-80 km around the peak time of the event. VLF/LF anomalies are correlated and in phase with the stratospheric temperature and mesospheric pressure variation, while minimum of mesospheric cooling shows a 2-3 day delay with maximum VLF/LF anomalies. Simulations of VLF/LF diurnal variation are performed using the well-known Long Wave Propagating Capability (LWPC) code within the Earth-ionosphere waveguide to explain the VLF/LF anomalies qualitatively.

  6. Broad-Band Analysis of Polar Motion Excitations

    Science.gov (United States)

    Chen, J.

    2016-12-01

    Earth rotational changes, i.e. polar motion and length-of-day (LOD), are driven by two types of geophysical excitations: 1) mass redistribution within the Earth system, and 2) angular momentum exchange between the solid Earth (more precisely the crust) and other components of the Earth system. Accurate quantification of Earth rotational excitations has been difficult, due to the lack of global-scale observations of mass redistribution and angular momentum exchange. The over 14-years time-variable gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) have provided a unique means for quantifying Earth rotational excitations from mass redistribution in different components of the climate system. Comparisons between observed Earth rotational changes and geophysical excitations estimated from GRACE, satellite laser ranging (SLR) and climate models show that GRACE-derived excitations agree remarkably well with polar motion observations over a broad-band of frequencies. GRACE estimates also suggest that accelerated polar region ice melting in recent years and corresponding sea level rise have played an important role in driving long-term polar motion as well. With several estimates of polar motion excitations, it is possible to estimate broad-band noise variance and noise power spectra in each, given reasonable assumptions about noise independence. Results based on GRACE CSR RL05 solutions clearly outperform other estimates with the lowest noise levels over a broad band of frequencies.

  7. Laser Spectroscopy and Frequency Combs

    International Nuclear Information System (INIS)

    Hänsch, Theodor W; Picqué, Nathalie

    2013-01-01

    The spectrum of a frequency comb, commonly generated by a mode-locked femtosecond laser consists of several hundred thousand precisely evenly spaced spectral lines. Such laser frequency combs have revolutionized the art measuring the frequency of light, and they provide the long-missing clockwork for optical atomic clocks. The invention of the frequency comb technique has been motivated by precision laser spectroscopy of the simple hydrogen atom. The availability of commercial instruments is facilitating the evolution of new applications far beyond the original purpose. Laser combs are becoming powerful instruments for broadband molecular spectroscopy by dramatically improving the resolution and recording speed of Fourier spectrometers and by creating new opportunities for highly multiplexed nonlinear spectroscopy, such as two-photon spectroscopy or coherent Raman spectroscopy. Other emerging applications of frequency combs range from fundamental research in astronomy, chemistry, or attosecond science to telecommunications and satellite navigation

  8. A frequency conversion mode for dispenser in the service station based on flow rate signal

    International Nuclear Information System (INIS)

    Liu, Y J; Tang, D; Huang, J B; Liu, J; Jia, P F

    2012-01-01

    Dispenser is an integrated fuel transport and measurement system at the service station. In this paper, we developed a frequency conversion mode for the dispenser, based on the flow rate signal which is obtained from the converter measuring flow capacity. After introducing the frequency conversion mode to dispenser, we obtained that pump rotates at a high speed when fuelled with high flow rate, and it rotates at a low speed when fuelled with low flow rate. This makes the fuel dispenser more energy-efficient and controllable. We also did some valve optimizations on the dispenser and developed a new control mode for preset refuelling based on the frequency conversion mode, Experimental and theoretical studies have shown that the new dispenser not only can meet the national standards, but also performs better than the ordinary one especially in preset refuelling.

  9. Broadband Radiometric LED Measurements

    OpenAIRE

    Eppeldauer, G. P.; Cooksey, C. C.; Yoon, H. W.; Hanssen, L. M.; Podobedov, V. B.; Vest, R. E.; Arp, U.; Miller, C. C.

    2016-01-01

    At present, broadband radiometric measurements of LEDs with uniform and low-uncertainty results are not available. Currently, either complicated and expensive spectral radiometric measurements or broadband photometric LED measurements are used. The broadband photometric measurements are based on the CIE standardized V(��) function, which cannot be used in the UV range and leads to large errors when blue or red LEDs are measured in its wings, where the realization is always poor. Reference irr...

  10. Distortions in frequency spectra of signals associated with sampling-pulse shapes

    International Nuclear Information System (INIS)

    Njau, E.C.

    1983-04-01

    A method developed earlier by the author [IC/82/44; IC/82/45] is used to investigate distortions introduced into frequency spectra of signals by the shapes of the sampling pulses involved. Conditions are established under which the use of trapezoid or exponentially-edged pulses to digitize signals can make the frequency spectra of the resultant data samples devoid of the main features of the signals. This observation does not, however, apply in any way to cosinusoidally-edged pulses or to pulses with cosine-squared edges. Since parts of the Earth's surface and atmosphere receive direct solar energy in discrete samples (i.e. only from sunrise to sunset) we have extended the technique and attempted to develop a theory that explains the observed solar terrestrial relationships. A very good agreement is obtained between the theory and previous long-term and short-term observations. (author)

  11. A high-flux entanglement source based on a doubly resonant optical parametric amplifier

    International Nuclear Information System (INIS)

    Kuklewicz, Christopher E; Keskiner, Eser; Wong, Franco N C; Shapiro, Jeffrey H

    2002-01-01

    A 532 nm pumped type-II phase-matched, doubly resonant KTP optical parametric amplifier (OPA) was operated near frequency degeneracy to yield an inferred downconverted photon pair production rate of 1.7x10 6 s -1 at a pump power of 100 μW. The OPA output consisted of three components: narrowband doubly resonant mode pairs; narrowband singly resonant mode pairs for which either the signal or idler was resonant with the cavity and broadband nonresonant mode pairs. Under frequency-degenerate operation, the broadband nonresonant mode pairs were polarization triplet states. We observed quantum interference between the orthogonally polarized photons of the triplet states when they were analysed with a polarizer set at 45 deg. relative to the OPA's output polarizations, leading to reduced coincidence counts

  12. Distinguishing low frequency oscillations within the 1/f spectral behaviour of electromagnetic brain signals.

    Science.gov (United States)

    Demanuele, Charmaine; James, Christopher J; Sonuga-Barke, Edmund Js

    2007-12-10

    It has been acknowledged that the frequency spectrum of measured electromagnetic (EM) brain signals shows a decrease in power with increasing frequency. This spectral behaviour may lead to difficulty in distinguishing event-related peaks from ongoing brain activity in the electro- and magnetoencephalographic (EEG and MEG) signal spectra. This can become an issue especially in the analysis of low frequency oscillations (LFOs) - below 0.5 Hz - which are currently being observed in signal recordings linked with specific pathologies such as epileptic seizures or attention deficit hyperactivity disorder (ADHD), in sleep studies, etc. In this work we propose a simple method that can be used to compensate for this 1/f trend hence achieving spectral normalisation. This method involves filtering the raw measured EM signal through a differentiator prior to further data analysis. Applying the proposed method to various exemplary datasets including very low frequency EEG recordings, epileptic seizure recordings, MEG data and Evoked Response data showed that this compensating procedure provides a flat spectral base onto which event related peaks can be clearly observed. Findings suggest that the proposed filter is a useful tool for the analysis of physiological data especially in revealing very low frequency peaks which may otherwise be obscured by the 1/f spectral activity inherent in EEG/MEG recordings.

  13. Echolocation signals of free-ranging Indo-Pacific humpback dolphins (Sousa chinensis) in Sanniang Bay, China.

    Science.gov (United States)

    Fang, Liang; Li, Songhai; Wang, Kexiong; Wang, Zhitao; Shi, Wenjing; Wang, Ding

    2015-09-01

    While the low-frequency communication sounds of Indo-Pacific humpback dolphins (Sousa chinensis) have been reported in a number of papers, the high-frequency echolocation signals of Sousa chinensis, especially those living in the wild, have been less studied. In the current study, echolocation signals of humpback dolphins were recorded in Sanniang Bay, Guangxi Province, China, using a cross-type hydrophone array with five elements. In total, 77 candidate on-axis clicks from 77 scans were selected for analysis. The results showed that the varied peak-to-peak source levels ranged from 177.1 to 207.3 dB, with an average of 187.7 dB re: 1 μPa. The mean peak frequency was 109.0 kHz with a -3-dB bandwidth of 50.3 kHz and 95% energy duration of 22 μs. The -3-dB bandwidth was much broader than the root mean square bandwidth and exhibited a bimodal distribution. The center frequency exhibited a positive relationship with the peak-to-peak source level. The clicks of the wild Indo-Pacific humpback dolphins were short-duration, broadband, ultrasonic pulses, similar to those produced by other whistling dolphins of similar body size. However, the click source levels of the Indo-Pacific humpback dolphin appear to be lower than those of other whistling dolphins.

  14. High frequency oscillations evoked by peripheral magnetic stimulation.

    Science.gov (United States)

    Biller, S; Simon, L; Fiedler, P; Strohmeier, D; Haueisen, J

    2011-01-01

    The analysis of somatosensory evoked potentials (SEP) and / or fields (SEF) is a well-established and important tool for investigating the functioning of the peripheral and central human nervous system. A standard technique to evoke SEPs / SEFs is the stimulation of the median nerve by using a bipolar electrical stimulus. We aim at an alternative stimulation technique enabling stimulation of deep nerve structures while reducing patient stress and error susceptibility. In the current study, we apply a commercial transcranial magnetic stimulation system for peripheral magnetic stimulation of the median nerve. We compare the results of simultaneously recorded EEG signals to prove applicability of our technique to evoke SEPs including low frequency components (LFC) as well as high frequency oscillations (HFO). Therefore, we compare amplitude, latency and time-frequency characteristics of the SEP of 14 healthy volunteers after electric and magnetic stimulation. Both low frequency components and high frequency oscillations were detected. The HFOs were superimposed onto the primary cortical response N20. Statistical analysis revealed significantly lower amplitudes and increased latencies for LFC and HFO components after magnetic stimulation. The differences indicate the inability of magnetic stimulation to elicit supramaximal responses. A psycho-perceptual evaluation showed that magnetic stimulation was less unpleasant for 12 out of the 14 volunteers. In conclusion, we showed that LFC and HFO components related to median nerve stimulation can be evoked by peripheral magnetic stimulation.

  15. Broadband image sensor array based on graphene-CMOS integration

    Science.gov (United States)

    Goossens, Stijn; Navickaite, Gabriele; Monasterio, Carles; Gupta, Shuchi; Piqueras, Juan José; Pérez, Raúl; Burwell, Gregory; Nikitskiy, Ivan; Lasanta, Tania; Galán, Teresa; Puma, Eric; Centeno, Alba; Pesquera, Amaia; Zurutuza, Amaia; Konstantatos, Gerasimos; Koppens, Frank

    2017-06-01

    Integrated circuits based on complementary metal-oxide-semiconductors (CMOS) are at the heart of the technological revolution of the past 40 years, enabling compact and low-cost microelectronic circuits and imaging systems. However, the diversification of this platform into applications other than microcircuits and visible-light cameras has been impeded by the difficulty to combine semiconductors other than silicon with CMOS. Here, we report the monolithic integration of a CMOS integrated circuit with graphene, operating as a high-mobility phototransistor. We demonstrate a high-resolution, broadband image sensor and operate it as a digital camera that is sensitive to ultraviolet, visible and infrared light (300-2,000 nm). The demonstrated graphene-CMOS integration is pivotal for incorporating 2D materials into the next-generation microelectronics, sensor arrays, low-power integrated photonics and CMOS imaging systems covering visible, infrared and terahertz frequencies.

  16. Is attention based on spatial contextual memory preferentially guided by low spatial frequency signals?

    Science.gov (United States)

    Patai, Eva Zita; Buckley, Alice; Nobre, Anna Christina

    2013-01-01

    A popular model of visual perception states that coarse information (carried by low spatial frequencies) along the dorsal stream is rapidly transmitted to prefrontal and medial temporal areas, activating contextual information from memory, which can in turn constrain detailed input carried by high spatial frequencies arriving at a slower rate along the ventral visual stream, thus facilitating the processing of ambiguous visual stimuli. We were interested in testing whether this model contributes to memory-guided orienting of attention. In particular, we asked whether global, low-spatial frequency (LSF) inputs play a dominant role in triggering contextual memories in order to facilitate the processing of the upcoming target stimulus. We explored this question over four experiments. The first experiment replicated the LSF advantage reported in perceptual discrimination tasks by showing that participants were faster and more accurate at matching a low spatial frequency version of a scene, compared to a high spatial frequency version, to its original counterpart in a forced-choice task. The subsequent three experiments tested the relative contributions of low versus high spatial frequencies during memory-guided covert spatial attention orienting tasks. Replicating the effects of memory-guided attention, pre-exposure to scenes associated with specific spatial memories for target locations (memory cues) led to higher perceptual discrimination and faster response times to identify targets embedded in the scenes. However, either high or low spatial frequency cues were equally effective; LSF signals did not selectively or preferentially contribute to the memory-driven attention benefits to performance. Our results challenge a generalized model that LSFs activate contextual memories, which in turn bias attention and facilitate perception.

  17. Dynamic Range Enhancement of High-Speed Electrical Signal Data via Non-Linear Compression

    Science.gov (United States)

    Laun, Matthew C. (Inventor)

    2016-01-01

    Systems and methods for high-speed compression of dynamic electrical signal waveforms to extend the measuring capabilities of conventional measuring devices such as oscilloscopes and high-speed data acquisition systems are discussed. Transfer function components and algorithmic transfer functions can be used to accurately measure signals that are within the frequency bandwidth but beyond the voltage range and voltage resolution capabilities of the measuring device.

  18. A high frequency test bench for rapid single-flux-quantum circuits

    International Nuclear Information System (INIS)

    Engseth, H; Intiso, S; Rafique, M R; Tolkacheva, E; Kidiyarova-Shevchenko, A

    2006-01-01

    We have designed and experimentally verified a test bench for high frequency testing of rapid single-flux-quantum (RSFQ) circuits. This test bench uses an external tunable clock signal that is stable in amplitude, phase and frequency. The high frequency external clock reads out the clock pattern stored in a long shift register. The clock pattern is consequently shifted out at high speed and split to feed both the circuit under test and an additional shift register in the test bench for later verification at low speed. This method can be employed for reliable high speed verification of RSFQ circuit operation, with use of only low speed read-out electronics. The test bench consists of 158 Josephson junctions and the occupied area is 3300 x 660 μm 2 . It was experimentally verified up to 33 GHz with ± 21.7% margins on the global bias supply current

  19. Tapered amplifier laser with frequency-shifted feedback

    Directory of Open Access Journals (Sweden)

    A. Bayerle, S. Tzanova, P. Vlaar, B. Pasquiou, F. Schreck

    2016-10-01

    Full Text Available We present a frequency-shifted feedback (FSF laser based on a tapered amplifier. The laser operates as a coherent broadband source with up to 370GHz spectral width and 2.3us coherence time. If the FSF laser is seeded by a continuous-wave laser a frequency comb spanning the output spectrum appears in addition to the broadband emission. The laser has an output power of 280mW and a center wavelength of 780nm. The ease and flexibility of use of tapered amplifiers makes our FSF laser attractive for a wide range of applications, especially in metrology.

  20. Bio-inspired heterogeneous composites for broadband vibration mitigation.

    Science.gov (United States)

    Chen, Yanyu; Wang, Lifeng

    2015-12-08

    Structural biological materials have developed heterogeneous and hierarchical architectures that are responsible for the outstanding performance to provide protection against environmental threats including static and dynamic loading. Inspired by this observation, this research aims to develop new material and structural concepts for broadband vibration mitigation. The proposed composite materials possess a two-layered heterogeneous architecture where both layers consist of high-volume platelet-shape reinforcements and low-volume matrix, similar to the well-known "brick and mortar" microstructure of biological composites. Using finite element method, we numerically demonstrated that broadband wave attenuation zones can be achieved by tailoring the geometric features of the heterogeneous architecture. We reveal that the resulting broadband attenuation zones are gained by directly superimposing the attenuation zones in each constituent layer. This mechanism is further confirmed by the investigation into the phonon dispersion relation of each layer. Importantly, the broadband wave attenuation capability will be maintained when the mineral platelet orientation is locally manipulated, yet a contrast between the mineral platelet concentrations of the two constituent layers is essential. The findings of this work will provide new opportunities to design heterogeneous composites for broadband vibration mitigation and impact resistance under mechanically challenging environmental conditions.

  1. Long-period pulses in broadband records of near earthquakes

    Czech Academy of Sciences Publication Activity Database

    Zahradník, J.; Plešinger, Axel

    2005-01-01

    Roč. 95, č. 5 (2005), s. 1928-1939 ISSN 0037-1106 R&D Projects: GA ČR GA205/02/0381; GA ČR GA205/03/1047 Grant - others:EC(XE) EVG3-CT-2002-80006 ( MAGMA ) Institutional research plan: CEZ:AV0Z30120515 Keywords : broadband records * near earthquakes * seismic signal Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.772, year: 2005

  2. Analysis of Broad-band Frequency Selective Shielding Glass by FDTD method

    OpenAIRE

    笠嶋, 善憲; Kasashima, Yoshinori

    2010-01-01

    A frequency Selective shielding (FSS) glass is a print of many same size antennas on a sheet of glass, and it has high shielding properties for one specific frequency. In the past, the author analyzed theoretically the characteristics of the FSS, as a large scale array antenna. The FSS has narrow-band shielding characteristics. This time, the author analyzed accurately the characteristics of a FSS glass being a print of many same size dipole antennas on a sheet of glass by FDTD method. As the...

  3. High frequency statistical energy analysis applied to fluid filled pipe systems

    NARCIS (Netherlands)

    Beek, P.J.G. van; Smeulers, J.P.M.

    2013-01-01

    In pipe systems, carrying gas with high velocities, broadband turbulent pulsations can be generated causing strong vibrations and fatigue failure, called Acoustic Fatigue. This occurs at valves with high pressure differences (i.e. chokes), relief valves and obstructions in the flow, such as sharp

  4. Semiconductor Quantum Dash Broadband Emitters: Modeling and Experiments

    KAUST Repository

    Khan, Mohammed Zahed Mustafa

    2013-10-01

    Broadband light emitters operation, which covers multiple wavelengths of the electromagnetic spectrum, has been established as an indispensable element to the human kind, continuously advancing the living standard by serving as sources in important multi-disciplinary field applications such as biomedical imaging and sensing, general lighting and internet and mobile phone connectivity. In general, most commercial broadband light sources relies on complex systems for broadband light generation which are bulky, and energy hungry. \\tRecent demonstration of ultra-broadband emission from semiconductor light sources in the form of superluminescent light emitting diodes (SLDs) has paved way in realization of broadband emitters on a completely novel platform, which offered compactness, cost effectiveness, and comparatively energy efficient, and are already serving as a key component in medical imaging systems. The low power-bandwidth product is inherent in SLDs operating in the amplified spontaneous emission regime. A quantum leap in the advancement of broadband emitters, in which high power and large bandwidth (in tens of nm) are in demand. Recently, the birth of a new class of broadband semiconductor laser diode (LDs) producing multiple wavelength light in stimulated emission regime was demonstrated. This very recent manifestation of a high power-bandwidth-product semiconductor broadband LDs relies on interband optical transitions via quantum confined dot/dash nanostructures and exploiting the natural inhomogeneity of the self-assembled growth technology. This concept is highly interesting and extending the broad spectrum of stimulated emission by novel device design forms the central focus of this dissertation. \\tIn this work, a simple rate equation numerical technique for modeling InAs/InP quantum dash laser incorporating the properties of inhomogeneous broadening effect on lasing spectra was developed and discussed, followed by a comprehensive experimental analysis

  5. A photo-excited broadband to dual-band tunable terahertz prefect metamaterial polarization converter

    Science.gov (United States)

    Zhu, Jianfeng; Yang, Yang; Li, Shufang

    2018-04-01

    A new and simple design of photo-excited broadband to dual-band tunable terahertz (THz) metamaterial cross polarization converter is proposed in this paper. The tunable converter is a sandwich structure with the center-cut cross-shaped metallic patterned structure as a resonator, the middle dielectric layer as a spacer and the bottom metallic film as the ground. The conductivity of the photoconductive semiconductor (Silicon) filled in the gap of the cross-shaped metallic resonator can be tuned by the incident pump power, leading to an easy modulation of the electromagnetic response of the proposed converter. The results show that the proposed cross-polarization converter can be tuned from a broadband with polarization conversion ratio (PCR) beyond 95% (1.86-2.94 THz) to dual frequency bands (fl = 1 . 46 THz &fh = 2 . 9 THz). The conversion peaks can reach 99.9% for the broadband and, 99.5% (fl) and 99.7% (fh) for the dual-band, respectively. Most importantly, numerical simulations demonstrate that the broadband/dual-band polarization conversion mechanism of the converter originates from the localized surface plasmon modes, which make the design simple and different from previous designs. With these good features, the proposed broadband to dual-band tunable polarization converter is expected to be used in widespread applications.

  6. High-performance broadband photodetector using solution-processible PbSe-TiO(2)-graphene hybrids.

    Science.gov (United States)

    Manga, Kiran Kumar; Wang, Junzhong; Lin, Ming; Zhang, Jie; Nesladek, Milos; Nalla, Venkatram; Ji, Wei; Loh, Kian Ping

    2012-04-03

    Highly sensitive, multicomponent broadband photodetector devices are made from PbSe/graphene/TiO(2). TiO(2) and PbSe nanoparticles act as light harvesting photoactive materials from the UV to IR regions of the electromagnetic spectrum, while the graphene acts as a charge collector for both photogenerated holes and electrons under an applied electric field. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Testing a simple control law to reduce broadband frequency harmonic vibrations using semi-active tuned mass dampers

    International Nuclear Information System (INIS)

    Moutinho, Carlos

    2015-01-01

    This paper is focused on the control problems related to semi-active tuned mass dampers (TMDs) used to reduce harmonic vibrations, specially involving civil structures. A simplified version of the phase control law is derived and its effectiveness is investigated and evaluated. The objective is to improve the functioning of control systems of this type by simplifying the measurement process and reducing the number of variables involved, making the control system more feasible and reliable. Because the control law is of ON/OFF type, combined with appropriate trigger conditions, the activity of the actuation system may be significantly reduced, which may be of few seconds a day in many practical cases, increasing the durability of the device and reducing its maintenance. Moreover, due to the ability of the control system to command the motion of the inertial mass, the semi-active TMD is relatively insensitive to its initial tuning, resulting in the capability of self-tuning and in the possibility of controlling several vibration modes of a structure over a significant broadband frequency. (paper)

  8. Driving demand for broadband networks and services

    CERN Document Server

    Katz, Raul L

    2014-01-01

    This book examines the reasons why various groups around the world choose not to adopt broadband services and evaluates strategies to stimulate the demand that will lead to increased broadband use. It introduces readers to the benefits of higher adoption rates while examining the progress that developed and emerging countries have made in stimulating broadband demand. By relying on concepts such as a supply and demand gap, broadband price elasticity, and demand promotion, this book explains differences between the fixed and mobile broadband demand gap, introducing the notions of substitution and complementarity between both platforms. Building on these concepts, ‘Driving Demand for Broadband Networks and Services’ offers a set of best practices and recommendations aimed at promoting broadband demand.  The broadband demand gap is defined as individuals and households that could buy a broadband subscription because they live in areas served by telecommunications carriers but do not do so because of either ...

  9. High quality broadband spatial reflections of slow Rayleigh surface acoustic waves modulated by a graded grooved surface

    KAUST Repository

    Xu, Yanlong

    2015-01-21

    We report high quality broadband spatial reflections of Rayleigh surface acoustic waves (SAWs) through a graded grooved surface. High quality means that no wave is allowed to transmit and the incident wave is nearly all reflected to the input side. The graded grooved surface is structured by drilling one dimensional array of graded grooves with increased depths on a flat surface. We investigate SAW dispersion relations, wave field distribution at several typical SAW wavelengths, and time evolution of a Gaussian pulse through the graded grooved surface. Results show that the input broadband Rayleigh SAWs can be slowed, spatially enhanced and stopped, and finally reflected to the input side. The study suggests that engraving the flat surface can be used as an efficient and economical way to manipulate Rayleigh SAWs, which has potential application in novel SAW devices such as filters, reflectors, sensors, energy harvesters, and diodes.

  10. A MODEL FOR PRODUCING STABLE, BROADBAND TERAHERTZ COHERENT SYNCHROTRON RADIATION IN STORAGE RINGS

    International Nuclear Information System (INIS)

    Sannibale, Fernando; Byrd, John M.; Loftsdottir, Agusta; Martin, MichaelC.; Venturini, Marco

    2003-01-01

    We present a model for producing stable broadband coherent synchrotron radiation (CSR) in the terahertz frequency region in an electron storage ring. The model includes distortion of bunch shape from the synchrotron radiation (SR), enhancing higher frequency coherent emission and limits to stable emission due to a microbunching instability excited by the SR. We use this model to optimize the performance of a source for CSR emission

  11. Underwater Broadband Source Localization Based on Modal Filtering and Features Extraction

    Directory of Open Access Journals (Sweden)

    Dominique Fattaccioli

    2010-01-01

    Full Text Available Passive source localization is a crucial issue in underwater acoustics. In this paper, we focus on shallow water environment (0 to 400 m and broadband Ultra-Low Frequency acoustic sources (1 to 100 Hz. In this configuration and at a long range, the acoustic propagation can be described by normal mode theory. The propagating signal breaks up into a series of depth-dependent modes. These modes carry information about the source position. Mode excitation factors and mode phases analysis allow, respectively, localization in depth and distance. We propose two different approaches to achieve the localization: multidimensional approach (using a horizontal array of hydrophones based on frequency-wavenumber transform (F-K method and monodimensional approach (using a single hydrophone based on adapted spectral representation (FTa method. For both approaches, we propose first complete tools for modal filtering, and then depth and distance estimators. We show that adding mode sign and source spectrum informations improves considerably the localization performance in depth. The reference acoustic field needed for depth localization is simulated with the new realistic propagation modelMoctesuma. The feasibility of both approaches, F-K and FTa, are validated on data simulated in shallow water for different configurations. The performance of localization, in depth and distance, is very satisfactory.

  12. Underwater Broadband Source Localization Based on Modal Filtering and Features Extraction

    Directory of Open Access Journals (Sweden)

    Cristol Xavier

    2010-01-01

    Full Text Available Passive source localization is a crucial issue in underwater acoustics. In this paper, we focus on shallow water environment (0 to 400 m and broadband Ultra-Low Frequency acoustic sources (1 to 100 Hz. In this configuration and at a long range, the acoustic propagation can be described by normal mode theory. The propagating signal breaks up into a series of depth-dependent modes. These modes carry information about the source position. Mode excitation factors and mode phases analysis allow, respectively, localization in depth and distance. We propose two different approaches to achieve the localization: multidimensional approach (using a horizontal array of hydrophones based on frequency-wavenumber transform ( method and monodimensional approach (using a single hydrophone based on adapted spectral representation ( method. For both approaches, we propose first complete tools for modal filtering, and then depth and distance estimators. We show that adding mode sign and source spectrum informations improves considerably the localization performance in depth. The reference acoustic field needed for depth localization is simulated with the new realistic propagation modelMoctesuma. The feasibility of both approaches, and , are validated on data simulated in shallow water for different configurations. The performance of localization, in depth and distance, is very satisfactory.

  13. Tesla’s high voltage and high frequency generators with oscillatory circuits

    Directory of Open Access Journals (Sweden)

    Cvetić Jovan M.

    2016-01-01

    Full Text Available The principles that represent the basics of the work of the high voltage and high frequency generator with oscillating circuits will be discussed. Until 1891, Tesla made and used mechanical generators with a large number of extruded poles for the frequencies up to about 20 kHz. The first electric generators based on a new principle of a weakly coupled oscillatory circuits he used for the wireless signal transmission, for the study of the discharges in vacuum tubes, the wireless energy transmission, for the production of the cathode rays, that is x-rays and other experiments. Aiming to transfer the signals and the energy to any point of the surface of the Earth, in the late of 19th century, he had discovered and later patented a new type of high frequency generator called a magnifying transmitter. He used it to examine the propagation of electromagnetic waves over the surface of the Earth in experiments in Colorado Springs in the period 1899-1900. Tesla observed the formation of standing electromagnetic waves on the surface of the Earth by measuring radiated electric field from distant lightning thunderstorm. He got the idea to generate the similar radiation to produce the standing waves. On the one hand, signal transmission, i.e. communication at great distances would be possible and on the other hand, with more powerful and with at least three magnifying transmitters the wireless transmission of energy without conductors at any point of the Earth surface could also be achieved. The discovery of the standing waves on the surface of the Earth and the invention of the magnifying transmitter he claimed his greatest inventions. Less than two years later, at the end of 1901, he designed and started to build a much stronger magnifying transmitter on Long Island near New York City (the Wardenclyffe tower wishing to become a world telecommunication center. During the tower construction, he elaborated the plans for an even stronger transmitter based on

  14. Advances in the density profile evaluation from broadband reflectometry on ASDEX upgrade

    International Nuclear Information System (INIS)

    Varela, P.; Manso, M.; Conway, G.

    2001-01-01

    The high temporal and spatial resolutions provided by broadband microwave reflectometry make it an attractive diagnostic technique to measure the density profile in fusion plasmas. However, great problems have been encountered due to the plasma turbulence that difficult, and sometimes prevent, the routine evaluation of density profiles. Advanced broadband systems employ ultra-fast sweeping in an attempt to perform the profile measurement in a time window smaller than the temporal scale of the main plasma fluctuations but this is not sufficient. Indeed, abrupt plasma movements and/or spatial turbulence always affect the reflectometry signals, as shown by numerical studies (with both one- and two-dimensional codes), for the case of ultra-fast sweeping and pulse radar systems. For this reason not only the system performance is important but the software tools also play a crucial role for reflectometry to become a standard density profile diagnostic. Here we present the recent advances towards automatic evaluation of density profiles from broadband reflectometry on ASDEX Upgrade. For regimes with moderate levels of plasma turbulence, density profiles are obtained from single reflectometry samples (temporal resolution of 20 μs), and for higher turbulence levels average profiles are obtained from bursts of ultra-fast (20 μs), closely spaced (10 μs) sweeps. This method improved the accuracy and reliability of density profiles, which can now be obtained automatically from the edge to the bulk plasma - using reflectometry alone - in most plasma regimes of ASDEX Upgrade. New data processing capability has been implemented that allows the profiles to be available to the end-users 10-12 minutes after each discharge. These developments were possible due to the flexibility and high performance of the control and data acquisition systems and to the large number of measurements that can be performed with the diagnostic during each discharge (720 profiles both on the low- and

  15. Cross-polarisation discrimination-induced interference in dual-polarised high-capacity satellite communication systems

    Directory of Open Access Journals (Sweden)

    Abdulkareem Sarki Karasuwa

    2016-05-01

    Full Text Available The design of spectrally-efficient, high-throughput satellite (HTS systems with capacity approaching one terabit per second requires operating at Ka-band frequencies and above, where there are several gigahertz of allocated radio spectrum, using multiple spot beams with dual orthogonal polarisation mode. At these high frequencies, rain attenuation poses a major obstacle to the design of high-availability satellite links which are needed for the realisation of ubiquitous broadband multimedia communication services including high-speed Internet access at rural and remote locations. Furthermore, depolarisation-induced interference in such systems could have a performance-limiting impact if a co-channel cross-polar signal combines with system noise to drive the carrier-to-noise-plus-interference ratio (CNIR below an acceptable threshold. This paper employs real measurement data to investigate the impact of depolarisation-induced interference on dual-polarised HTS systems for temperate and tropical climatic regions. Scenarios that cause significant system performance degradation are analysed, including the effects of signal frequency, antenna size, and regional rainfall rate. The impact of depolarisation on system performance is quantified by the reductions in the CNIR and link availability of a dual-polarised system when compared with those of a similarly-dimensioned single-polarised system.

  16. Optimizing signal output: effects of viscoelasticity and difference frequency on vibroacoustic radiation of tissue-mimicking phantoms

    Science.gov (United States)

    Namiri, Nikan K.; Maccabi, Ashkan; Bajwa, Neha; Badran, Karam W.; Taylor, Zachary D.; St. John, Maie A.; Grundfest, Warren S.; Saddik, George N.

    2018-02-01

    Vibroacoustography (VA) is an imaging technology that utilizes the acoustic response of tissues to a localized, low frequency radiation force to generate a spatially resolved, high contrast image. Previous studies have demonstrated the utility of VA for tissue identification and margin delineation in cancer tissues. However, the relationship between specimen viscoelasticity and vibroacoustic emission remains to be fully quantified. This work utilizes the effects of variable acoustic wave profiles on unique tissue-mimicking phantoms (TMPs) to maximize VA signal power according to tissue mechanical properties, particularly elasticity. A micro-indentation method was utilized to provide measurements of the elastic modulus for each biological replica. An inverse relationship was found between elastic modulus (E) and VA signal amplitude among homogeneous TMPs. Additionally, the difference frequency (Δf ) required to reach maximum VA signal correlated with specimen elastic modulus. Peak signal diminished with increasing Δf among the polyvinyl alcohol specimen, suggesting an inefficient vibroacoustic response by the specimen beyond a threshold of resonant Δf. Comparison of these measurements may provide additional information to improve tissue modeling, system characterization, as well as insights into the unique tissue composition of tumors in head and neck cancer patients.

  17. Ultra-broadband photonic internet

    Science.gov (United States)

    Romaniuk, Ryszard S.

    2011-06-01

    In this paper, there is presented a review of our today's understanding of the ultimately broadband photonic Internet. A simple calculation is presented showing the estimate of the throughput of the core photonic network branches. Optoelectronic components, circuits, systems and signals, together with analogous electronic entities and common software layers, are building blocks of the contemporary Internet. Participation of photonics in development of the physical layer in the future Internet will probably increase. The photonics leads now to a better usage of the available bandwidth (increase of the spectral efficiency measured in Bit/s/Hz), increase in the transmission rate (from Gbps, via Tbps up to probably Pbps), increase in the transmission distance without signal regeneration (in distortion compensated active optical cables), increase in energy/power efficiency measured in W/Gbps, etc. Photonics may lead, in the future, to fully transparent optical networks and, thus, to essential increase in bandwidth and network reliability. It is expected that photonics (with biochemistry, electronics and mechatronics) may build psychological and physiological interface for humans to the future global network. The following optical signal multiplexing methods were considered, which are possible without O/E/O conversion: TDM-OTDM, FDM-CO-OFDM, OCDM-OCDMA, WDM-DWDM.

  18. Detecting Lamb waves with broadband acousto-ultrasonic signals in composite structures

    Science.gov (United States)

    Kautz, Harold E.

    1992-01-01

    Lamb waves can be produced and detected in ceramic matrix composites (CMC) and metal matrix composites (MMC) plates using the acousto-ultrasonic configuration employing broadband transducers. Experimental dispersion curves of lowest symmetric and lowest antisymmetric modes behave in a manner analogous to the graphite/polymer theoretical curves. In this study a basis has been established for analyzing Lamb wave velocities for characterizing composite plates. Lamb wave disperison curves and group velocities were correlated with variations in axial stiffness and shear stiffness in MMC and CMC. For CMCs, interfacial shear strength was also correlated with the first antisymmetric Lamb mode.

  19. Stochastic resonance in a single-mode laser driven by frequency modulated signal and coloured noises

    Institute of Scientific and Technical Information of China (English)

    Jin Guo-Xiang; Zhang Liang-Ying; Cao Li

    2009-01-01

    By adding frequency modulated signals to the intensity equation of gain-noise model of the single-mode laser driven by two coloured noises which are correlated, this paper uses the linear approximation method to calculate the power spectrum and signal-to-noise ratio (SNR) of the laser intensity. The results show that the SNR appears typical stochastic resonance with the variation of intensity of the pump noise and quantum noise. As the amplitude of a modulated signal has effects on the SNR, it shows suppression, monotone increasing, stochastic resonance, and multiple stochastic resonance with the variation of the frequency of a carrier signal and modulated signal.

  20. Modeling high dimensional multichannel brain signals

    KAUST Repository

    Hu, Lechuan

    2017-03-27

    In this paper, our goal is to model functional and effective (directional) connectivity in network of multichannel brain physiological signals (e.g., electroencephalograms, local field potentials). The primary challenges here are twofold: first, there are major statistical and computational difficulties for modeling and analyzing high dimensional multichannel brain signals; second, there is no set of universally-agreed measures for characterizing connectivity. To model multichannel brain signals, our approach is to fit a vector autoregressive (VAR) model with sufficiently high order so that complex lead-lag temporal dynamics between the channels can be accurately characterized. However, such a model contains a large number of parameters. Thus, we will estimate the high dimensional VAR parameter space by our proposed hybrid LASSLE method (LASSO+LSE) which is imposes regularization on the first step (to control for sparsity) and constrained least squares estimation on the second step (to improve bias and mean-squared error of the estimator). Then to characterize connectivity between channels in a brain network, we will use various measures but put an emphasis on partial directed coherence (PDC) in order to capture directional connectivity between channels. PDC is a directed frequency-specific measure that explains the extent to which the present oscillatory activity in a sender channel influences the future oscillatory activity in a specific receiver channel relative all possible receivers in the network. Using the proposed modeling approach, we have achieved some insights on learning in a rat engaged in a non-spatial memory task.