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Sample records for frequency modulated fm

  1. Preliminary Evidence of Preattentive Distinctions of Frequency-Modulated (FM tones that Convey Affect

    Directory of Open Access Journals (Sweden)

    David I Leitman

    2011-10-01

    Full Text Available Recognizing emotion is an evolutionary imperative. An early stage of auditory scene analysis involves the perceptual grouping of acoustic features, which can be based on both temporal coincidence and spectral features such as perceived pitch. Perceived pitch, or fundamental frequency (F0, is an especially salient cue for differentiating affective intent through speech intonation (prosody. We hypothesized that: 1 simple frequency modulated (FM tone abstractions, based on the parameters of actual prosodic stimuli, would be reliably classified as representing differing emotional categories; and 2 that such differences would yield significant mismatch negativities (MMNs - an index of preattentive deviance detection within the auditory environment. We constructed a set of FM tones that approximated the F0 mean and variation of reliably-recognized happy and neutral prosodic stimuli. These stimuli were presented to 13 subjects using a passive listening oddball paradigm. We additionally included stimuli with no frequency modulation (FM and FM tones with identical carrier frequencies but differing modulation depths as control conditions. Following electrophysiological recording, subjects were asked to identify the sounds they heard as happy, sad, angry or neutral. We observed that FM tones abstracted from happy and no expression speech stimuli elicited MMNs. Post-hoc behavioral testing revealed that subjects reliably identified the FM tones in a consistent manner. Finally, we also observed that FM tones and no-FM tones elicited equivalent MMNs. MMNs to FM tones that differentiate affect suggests that these abstractions may be sufficient to characterize prosodic distinctions, and that these distinctions can be represented in pre-attentive auditory sensory memory.

  2. Auditory rehabilitation after stroke: treatment of auditory processing disorders in stroke patients with personal frequency-modulated (FM) systems.

    Science.gov (United States)

    Koohi, Nehzat; Vickers, Deborah; Chandrashekar, Hoskote; Tsang, Benjamin; Werring, David; Bamiou, Doris-Eva

    2017-03-01

    Auditory disability due to impaired auditory processing (AP) despite normal pure-tone thresholds is common after stroke, and it leads to isolation, reduced quality of life and physical decline. There are currently no proven remedial interventions for AP deficits in stroke patients. This is the first study to investigate the benefits of personal frequency-modulated (FM) systems in stroke patients with disordered AP. Fifty stroke patients had baseline audiological assessments, AP tests and completed the (modified) Amsterdam Inventory for Auditory Disability and Hearing Handicap Inventory for Elderly questionnaires. Nine out of these 50 patients were diagnosed with disordered AP based on severe deficits in understanding speech in background noise but with normal pure-tone thresholds. These nine patients underwent spatial speech-in-noise testing in a sound-attenuating chamber (the "crescent of sound") with and without FM systems. The signal-to-noise ratio (SNR) for 50% correct speech recognition performance was measured with speech presented from 0° azimuth and competing babble from ±90° azimuth. Spatial release from masking (SRM) was defined as the difference between SNRs measured with co-located speech and babble and SNRs measured with spatially separated speech and babble. The SRM significantly improved when babble was spatially separated from target speech, while the patients had the FM systems in their ears compared to without the FM systems. Personal FM systems may substantially improve speech-in-noise deficits in stroke patients who are not eligible for conventional hearing aids. FMs are feasible in stroke patients and show promise to address impaired AP after stroke. Implications for Rehabilitation This is the first study to investigate the benefits of personal frequency-modulated (FM) systems in stroke patients with disordered AP. All cases significantly improved speech perception in noise with the FM systems, when noise was spatially separated from the

  3. Despeckle Filtering for Multiscale Amplitude-Modulation Frequency-Modulation (AM-FM Texture Analysis of Ultrasound Images of the Intima-Media Complex

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    C. P. Loizou

    2014-01-01

    Full Text Available The intima-media thickness (IMT of the common carotid artery (CCA is widely used as an early indicator of cardiovascular disease (CVD. Typically, the IMT grows with age and this is used as a sign of increased risk of CVD. Beyond thickness, there is also clinical interest in identifying how the composition and texture of the intima-media complex (IMC changed and how these textural changes grow into atherosclerotic plaques that can cause stroke. Clearly though texture analysis of ultrasound images can be greatly affected by speckle noise, our goal here is to develop effective despeckle noise methods that can recover image texture associated with increased rates of atherosclerosis disease. In this study, we perform a comparative evaluation of several despeckle filtering methods, on 100 ultrasound images of the CCA, based on the extracted multiscale Amplitude-Modulation Frequency-Modulation (AM-FM texture features and visual image quality assessment by two clinical experts. Texture features were extracted from the automatically segmented IMC for three different age groups. The despeckle filters hybrid median and the homogeneous mask area filter showed the best performance by improving the class separation between the three age groups and also yielded significantly improved image quality.

  4. Wideband FM Demodulation and Multirate Frequency Transformations

    Science.gov (United States)

    2016-12-15

    the center frequency and bandwidth are manually assigned to each formant, which may incur serious distortion to the isolated resonance signal and... problem can be solved via populating the whole time- frequency space to take advantage of the dyadic filter bank behavior of the EMD. Currently, we only...AFRL-RV-PS- AFRL-RV-PS- TR-2016-0123 TR-2016-0123 WIDEBAND FM DEMODULATION AND MULTIRATE FREQUENCY TRANSFORMATIONS Balu Santhanam and Wenjing Liu

  5. A combined frequency modulation dynamic force microscopy (FM-DFM) and scanning tunneling microscopy (STM) study of a SiO{sub 2}/Ru(0001) model system

    Energy Technology Data Exchange (ETDEWEB)

    Buechner, Christin; Lichtenstein, Leonid; Heinke, Lars; Heyde, Markus; Freund, Hans-Joachim [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin (Germany)

    2011-07-01

    Silica based support materials play an important role in catalysis. A stable and well characterized crystalline silica film can act as a model system for bulk silica and help us to understand silica's properties in detail. In order to examine catalytically relevant processes on such model surfaces, a thorough investigation of defect sites of any form is eminent. Recently, a double-layer silica film could be prepared on Ru(0001). Here we used a combined frequency modulation dynamic force microscope (FM-DFM) and scanning tunneling microscope (STM) under low temperature and ultra-high vacuum conditions to unveil the thin film's structural and electronic surface properties. Atomically resolved images of the crystalline silica film grown on Ru(0001) are presented. Structural elements of the pristine film, as well as its defects, are highlighted. Based on atomic resolution FM-DFM and STM images a direct comparison with density functional theory calculation can be made. Theory as well as experiment favor a hexagonal honeycomb structure of the film. Spectroscopy measurements, i.e. scanning tunneling spectroscopy (STS) and Kelvin probe force microscopy (KPFM), provide first insights into electronic properties of the system.

  6. Research on Doppler frequency in incoherent FM/CW laser detection

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    Liu, Kai; Cui, Zhanzhong

    2010-10-01

    The principle of transmitted and received laser in incoherent FM/CW laser detection is different from the one in coherent FM/CW laser detection. The methods for distance solution in both detections are similar. Incoherent FM/CW laser detection uses subcarrier to modulate the intensity of laser, and the photodetector detects the intensity of received signal. The amplified photocurrent is mixed with local oscillator signal, and the intermediate frequency (IF) signal contains the information of distance from sensor to target. The Doppler frequency for this detection is related with the relative radial velocity between sensor and target. The optical frequency is directly modulated with electro-optic device in coherent FM/CW laser detection and the received laser signal is photomixed with transmitted laser signal. The Doppler frequency in the detection relates to the optical frequency. In distance-measuring lidar, the Doppler frequency affects the solution. The Doppler frequency in incoherent FM/CW laser detection is unrelated with optical frequency, and it is much less than the one in coherent FM/CW laser detection, correspondingly. The error in incoherent FM/CW laser detection is smaller. As a result, the incoherent FM/CW laser detection is more suitable for the use of distance-measuring lidar.

  7. A New High-Performance Digital FM Modulator and Demodulator for Software-Defined Radio and Its FPGA Implementation

    Directory of Open Access Journals (Sweden)

    Indranil Hatai

    2011-01-01

    Full Text Available This paper deals with an FPGA implementation of a high performance FM modulator and demodulator for software defined radio (SDR system. The individual component of proposed FM modulator and demodulator has been optimized in such a way that the overall design consists of a high-speed, area optimized and low-power features. The modulator and demodulator contain an optimized direct digital frequency synthesizer (DDFS based on quarter-wave symmetry technique for generating the carrier frequency with spurious free dynamic range (SFDR of more than 64 dB. The FM modulator uses pipelined version of the DDFS to support the up conversion in the digital domain. The proposed FM modulator and demodulator has been implemented and tested using XC2VP30-7ff896 FPGA as a target device and can operate at a maximum frequency of 334.5 MHz and 131 MHz involving around 1.93 K and 6.4 K equivalent gates for FM modulator and FM demodulator respectively. After applying a 10 KHz triangular wave input and by setting the system clock frequency to 100 MHz using Xpower the power has been calculated. The FM modulator consumes 107.67 mW power while FM demodulator consumes 108.67 mW power for the same input running at same data rate.

  8. Speech recognition with amplitude and frequency modulations

    Science.gov (United States)

    Zeng, Fan-Gang; Nie, Kaibao; Stickney, Ginger S.; Kong, Ying-Yee; Vongphoe, Michael; Bhargave, Ashish; Wei, Chaogang; Cao, Keli

    2005-02-01

    Amplitude modulation (AM) and frequency modulation (FM) are commonly used in communication, but their relative contributions to speech recognition have not been fully explored. To bridge this gap, we derived slowly varying AM and FM from speech sounds and conducted listening tests using stimuli with different modulations in normal-hearing and cochlear-implant subjects. We found that although AM from a limited number of spectral bands may be sufficient for speech recognition in quiet, FM significantly enhances speech recognition in noise, as well as speaker and tone recognition. Additional speech reception threshold measures revealed that FM is particularly critical for speech recognition with a competing voice and is independent of spectral resolution and similarity. These results suggest that AM and FM provide independent yet complementary contributions to support robust speech recognition under realistic listening situations. Encoding FM may improve auditory scene analysis, cochlear-implant, and audiocoding performance. auditory analysis | cochlear implant | neural code | phase | scene analysis

  9. Detection of combined frequency and amplitude modulation.

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    Moore, B C; Sek, A

    1992-12-01

    This article is concerned with the detection of mixed modulation (MM), i.e., simultaneously occurring amplitude modulation (AM) and frequency modulation (FM). In experiment 1, an adaptive two-alternative forced-choice task was used to determine thresholds for detecting AM alone. Then, thresholds for detecting FM were determined for stimuli which had a fixed amount of AM in the signal interval only. The amount of AM was always less than the threshold for detecting AM alone. The FM thresholds depended significantly on the magnitude of the coexisting AM. For low modulation rates (4, 16, and 64 Hz), the FM thresholds did not depend significantly on the relative phase of modulation for the FM and AM. For a high modulation rate (256 Hz) strong effects of modulator phase were observed. These phase effects are as predicted by the model proposed by Hartmann and Hnath [Acustica 50, 297-312 (1982)], which assumes that detection of modulation at modulation frequencies higher than the critical modulation frequency is based on detection of the lower sideband in the modulated signal's spectrum. In the second experiment, psychometric functions were measured for the detection of AM alone and FM alone, using modulation rates of 4 and 16 Hz. Results showed that, for each type of modulation, d' is approximately a linear function of the square of the modulation index. Application of this finding to the results of experiment 1 suggested that, at low modulation rates, FM and AM are not detected by completely independent mechanisms. In the third experiment, psychometric functions were again measured for the detection of AM alone and FM alone, using a 10-Hz modulation rate. Detectability was then measured for combined AM and FM, with modulation depths selected so that each type of modulation would be equally detectable if presented alone. Significant effects of relative modulator phase were found when detectability was relatively high. These effects were not correctly predicted by either a

  10. Potentials for Radio Frequency Identification in AEC/FM

    Institute of Scientific and Technical Information of China (English)

    Karsten Menzel; CONG Zixiang; Luke Allan

    2008-01-01

    Radio frequency identification (RFID) technology has proved to be very effective in industries as di-verse as aircraft manufacturing to health and care. The construction industry has been slow to take up on RFID and this paper will discuss the merits of the technology in its potential for application within the con-struction sector. The paper reports about the prototypical implementation of RFID-based information man-agement in FM-scenarios. The prototypes were tested at University College Cork (UCC). The general appli-cability of RFID for decentralised information management could be demonstrated.

  11. 47 CFR 73.1570 - Modulation levels: AM, FM, TV and Class A TV aural.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Modulation levels: AM, FM, TV and Class A TV... levels: AM, FM, TV and Class A TV aural. (a) The percentage of modulation is to be maintained at as high... percent (82.5 kHz peak deviation). (3) TV and Class A TV stations. In no case shall the total...

  12. Wideband FM demodulation by injection-locked division of frequency deviation

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    Visweswaran, A.; Long, J.R.; Staszewski, R.B.

    2014-01-01

    A novel and useful wideband FM demodulator operating across an 8 GHz IF bandwidth for application in low-power, wideband heterodyne receivers. The demodulator includes an n-stage ring oscillator that is injection locked to a wideband input signal. Locking to the input frequency, it divides the FM de

  13. Improved PLL For FM Demodulator

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    Kirkham, Harold; Jackson, Shannon P.

    1992-01-01

    Phase-locked loop (PLL) for frequency demodulator contains improved frequency-to-voltage converter producing less ripple than conventional phase detector. In improved PLL, phase detector replaced by state estimator, implemented by ramp/sample-and-hold circuit. Intended to reduce noise in receiver of frequency-modulated (FM) telemetry link without sacrificing bandwidth. Also applicable to processing received FM signals.

  14. Linear, Low Noise Microwave Photonic Systems using Phase and Frequency Modulation

    Science.gov (United States)

    2012-05-11

    a monolithically integrated widely-tunable laser- phase modulator ,” in Proc. Optical Fiber Communication Conf. OFC 2004, vol. 2, 2004. [92] M. N... modulation efficiency experimental setup. . . . . . . . . . . . . . 70 5.5 DBR FM modulation efficiency versus frequency. . . . . . . . . . . . 71 v 5.6...Phase-noise limited noise figure for FM DBR lasers from measured modulation efficiency and linewidth. . . . . . . . . . . . . . . . . . . . 71 5.7

  15. Network models of frequency modulated sweep detection.

    Directory of Open Access Journals (Sweden)

    Steven Skorheim

    Full Text Available Frequency modulated (FM sweeps are common in species-specific vocalizations, including human speech. Auditory neurons selective for the direction and rate of frequency change in FM sweeps are present across species, but the synaptic mechanisms underlying such selectivity are only beginning to be understood. Even less is known about mechanisms of experience-dependent changes in FM sweep selectivity. We present three network models of synaptic mechanisms of FM sweep direction and rate selectivity that explains experimental data: (1 The 'facilitation' model contains frequency selective cells operating as coincidence detectors, summing up multiple excitatory inputs with different time delays. (2 The 'duration tuned' model depends on interactions between delayed excitation and early inhibition. The strength of delayed excitation determines the preferred duration. Inhibitory rebound can reinforce the delayed excitation. (3 The 'inhibitory sideband' model uses frequency selective inputs to a network of excitatory and inhibitory cells. The strength and asymmetry of these connections results in neurons responsive to sweeps in a single direction of sufficient sweep rate. Variations of these properties, can explain the diversity of rate-dependent direction selectivity seen across species. We show that the inhibitory sideband model can be trained using spike timing dependent plasticity (STDP to develop direction selectivity from a non-selective network. These models provide a means to compare the proposed synaptic and spectrotemporal mechanisms of FM sweep processing and can be utilized to explore cellular mechanisms underlying experience- or training-dependent changes in spectrotemporal processing across animal models. Given the analogy between FM sweeps and visual motion, these models can serve a broader function in studying stimulus movement across sensory epithelia.

  16. Electroacoustic Evaluation of Frequency-Modulated Receivers Interfaced with Personal Hearing Aids

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    Schafer, Erin C.; Thibodeau, Linda M.; Whalen, Holly S.; Overson, Gary J.

    2007-01-01

    Purpose: The purpose of this study was to compare the electroacoustic outputs of frequency-modulated (FM) systems coupled to hearing aids. Method: Electroacoustic performance of FM systems coupled to hearing aids was determined for 3 FM receivers: body-worn with neck loop, ear-level nonprogrammable, and ear-level programmable. Systems were…

  17. Detector level ABI spectral response function: FM4 analysis and comparison for different ABI modules

    Science.gov (United States)

    Efremova, Boryana; Pearlman, Aaron J.; Padula, Frank; Wu, Xiangqian

    2016-09-01

    A new generation of imaging instruments Advanced Baseline Imager (ABI) is to be launched aboard the Geostationary Operational Environmental Satellites - R Series (GOES-R). Four ABI flight modules (FM) are planned to be launched on GOES-R,S,T,U, the first one in the fall of 2016. Pre-launch testing is on-going for FM3 and FM4. ABI has 16 spectral channels, six in the visible/near infrared (VNIR 0.47 - 2.25 μm), and ten in the thermal infrared (TIR 3.9 - 13.3 μm) spectral regions, to be calibrated on-orbit by observing respectively a solar diffuser and a blackbody. Each channel has hundreds of detectors arranged in columns. Operationally one Analytic Generation of Spectral Response (ANGEN) function will be used to represent the spectral response function (SRF) of all detectors in a band. The Vendor conducted prelaunch end-to-end SRF testing to compare to ANGEN; detector specific SRF data was taken for: i) best detector selected (BDS) mode - for FM 2,3, and 4; and ii) all detectors (column mode) - for four spectral bands in FM3 and FM4. The GOES-R calibration working group (CWG) has independently used the SRF test data for FM2 and FM3 to study the potential impact of detector-to-detector SRF differences on the ABI detected Earth view radiances. In this paper we expand the CWG analysis to include the FM4 SRF test data - the results are in agreement with the Vendor analysis, and show excellent instrument performance and compare the detector-to-detector SRF differences and their potential impact on the detected Earth view radiances for all of the tested ABI modules.

  18. HIGHER FREQUENCY ULTRASONIC LIGHT MODULATORS.

    Science.gov (United States)

    LIGHT), (* MODULATORS , (*ULTRASONIC RADIATION, MODULATORS ), OPTICAL COMMUNICATIONS, BANDWIDTH, TRANSDUCERS, HIGH FREQUENCY, VERY HIGH FREQUENCY, ATTENUATION, DATA PROCESSING, OPTICAL EQUIPMENT, ANALOG COMPUTERS, THEORY.

  19. Frequency Modulation Spectroscopy Modeling for Remote Chemical Detection

    Energy Technology Data Exchange (ETDEWEB)

    Sheen, David M.

    2000-09-30

    Frequency modulation (FM) spectroscopy techniques show promise for active infrared remote chemical sensing. FM spectroscopy techniques have reduced sensitivity to optical and electronic noise, and are relatively immune to the effects of various electronic and mechanical drifts. FM systems are responsive to sharp spectral features and can therefore reduce the effects of spectral clutter due to interfering chemicals in the plume or in the atmosphere. The relatively high modulation frequencies used for FM also reduces the effects of albedo (reflectance) and plume variations. Conventional differential absorption lidar (DIAL) systems are performance limited by the noise induced by speckle. Analysis presented in this report shows that FM based sensors may reduce the effects of speckle by one to two orders of magnitude. This can result in reduced dwell times and faster area searches, as well as reducing various forms of spatial clutter. FM systems will require a laser system that is continuously tunable at relatively high frequencies (0.1 to 20 MHz). One promising candidate is the quantum-cascade (QC) laser [1, 2]. The QC laser is potentially capable of power levels on the order of 1 Watt and frequency tuning on the order of 3 - 6 GHz, which is the performance level required for FM spectroscopy based remote sensing. In this report we describe a high-level numerical model for an FM spectroscopy based remote sensing system, and application to two unmanned airborne vehicle (UAV) scenarios. A Predator scenario operating at a slant range of 6.5 km with a 10 cm diameter telescope, and a Global Hawk scenario operating at a range of 30 km with a 20 cm diameter telescope, has been assumed to allow estimation of the performance of potential FM systems.

  20. Amplitude-stabilized frequency-modulated laser diode and its interferometric sensing applications.

    Science.gov (United States)

    Takahashi, Y; Yoshino, T; Ohde, N

    1997-08-20

    A direct frequency-modulated (FM) laser diode light source without light power variation is developed. The amplitude variation of the FM laser diode is compensated by means of a feedback system with use of a superluminescent diode as an external light power controller. Output power greater than 1 mW is obtained at the modulation frequency to 5 kHz with a >10 stabilization factor. By use of the amplitude-stabilized FM laser diode, we measured subfringes with high accuracy in FM continuous wave interferometry, increased the dynamic range of the displacement measurement, and improved the stabilization factor in the laser diode feedback interferometer.

  1. DEMODULATION OF FREQUENCY OR SPACE MODULATED LIGHT.

    Science.gov (United States)

    LIGHT , DEMODULATION), (*OPTICAL COMMUNICATIONS, FREQUENCY MODULATION), (*FREQUENCY MODULATION, LIGHT ), OPTICAL TRACKING, BEAMS(ELECTROMAGNETIC), DEFLECTION, MICROWAVE FREQUENCY, ELECTRON BEAMS, PHOTOCATHODES

  2. Masking of a brief probe by sinusoidal frequency modulation.

    Science.gov (United States)

    Edwards, B W; Viemeister, N F

    1997-02-01

    Contrary to level detection models, the thresholds for a brief-duration probe masked by a sinusoidal frequency modulation (FM) masker increases as the modulation index (beta) of FM increases [Zwicker, Acustica 31, 243-256 (1974)]. In this paper the reason for this phenomenon is investigated. In experiment 1, a 10-ms, 1-kHz probe was detected in the presence of an FM masker centered at 1 kHz and sinusoidally modulated at 16 Hz. Thresholds increased by over 15 dB with increasing beta, consistent with Zwicker's findings. In experiment 2, the instantaneous frequency changes of the masker used in experiment 1 were clipped and the resulting thresholds indicated that detection was determined primarily by the masker's total frequency excursion rather than by its instantaneous sweep rate. In experiment 3, the FM maskers from the first two experiments were passed through a roex filter centered at 1 kHz and the resulting envelope was used to amplitude modulate a 1-kHz tone, producing approximately the same effective envelope at 1 kHz as the FM maskers. Threshold functions for the amplitude modulated (AM) maskers were similar to those for their corresponding FM maskers. Thresholds increased by over 15 dB while the total energy of the AM masker decreased by over 10 dB, again contrary to standard level-detection models. The results from these experiments can be explained, at least qualitatively, by a model based on envelope shape discrimination: similarities between the envelopes of the masker alone and masker-plus-probe at the output of an auditory filter centered on the frequency of the probe are primarily responsible for the observed masking, particularly at large beta's.

  3. Frequency modulated sound pattern analysis in the lesser bulldog bat: the role of interactions between adjacent frequency elements of complex sounds.

    Science.gov (United States)

    Roverud, R C

    1995-01-01

    A stereotyped approach phase vocalization response of Noctilio albiventris to artificial echoes simulating a virtual approaching object was used to assess the ability of the bat to analyze and extract distance information from the artificial echoes. The performance of the bats depended on the temporal pattern of frequency change of the continuously sweeping frequency modulated (FM) component of the signals. When the bats were presented with a CF/FM signal containing a time-reversed upward FM sweep, they responded with approach phase behavior at a performance level that was significantly below that seen with a CF/FM signal containing a naturally structured downward FM sweep. When the FM sweep was divided into a series of brief pure tone steps, the extent to which the bats showed a difference in their capability to process upward versus downward FM sweeps depended on the difference in frequency between the pure tone steps. The bats effectively processed downward but not upward FM sweeps when the difference in frequency between pure tone frequency elements of the FM sweeps was from about 100-200 Hz, but they effectually processed both downward and upward FM sweeps when the tonal elements composing the FM sweeps were separated by more than about 200 Hz. This suggests that the ability of the bats to effectively process downward but not upward FM sweeps is based on local interactions between adjacent frequency elements of the complex sounds.

  4. Suppression of FM-to-AM modulation by polarizing fiber front end for high-power lasers.

    Science.gov (United States)

    Qiao, Zhi; Wang, Xiaochao; Fan, Wei; Li, Xuechun; Jiang, Youen; Li, Rao; Huang, Canhong; Lin, Zunqi

    2016-10-10

    FM-to-AM modulation is an important effect in the front end of high-power lasers that influences the temporal profile. Various methods have been implemented in standard-fiber and polarization-maintaining (PM)-fiber front ends to suppress the FM-to-AM modulation. To analyze the modulation in the front end, a theoretical model is established and detailed simulations carried out that show that the polarizing (PZ) fiber, whose fast axis has a large loss, can successfully suppress the modulation. Moreover, the stability of the FM-to-AM modulation can be improved, which is important for the front end to obtain a stable output. To verify the model, a PZ fiber front end is constructed experimentally. The FM-to-AM modulation, without any compensation, is less than 4%, whereas that of the PM fiber front end with the same structure is nearly 20%. The stability of the FM-to-AM modulation depth is analyzed experimentally and the peak-to-peak and standard deviation (SD) are 2% and 0.38%, respectively, over 3 h. The experimental results agree with the simulation results and both prove that the PZ fiber front end can successfully suppress the FM-to-AM conversion. The PZ fiber front end is a promising alternative for improving the performance of the front end in high-power laser facilities.

  5. Intracellular responses to frequency modulated tones in the dorsal cortex of the mouse inferior colliculus

    NARCIS (Netherlands)

    H.R.A.P. Geis (H.-Rüdiger A.P.); J.G.G. Borst (Gerard)

    2013-01-01

    textabstractFrequency modulations occur in many natural sounds, including vocalizations. The neuronal response to frequency modulated (FM) stimuli has been studied extensively in different brain areas, with an emphasis on the auditory cortex and the central nucleus of the inferior colliculus. Here,

  6. Co-modulation of WDM-FDM WiMAX-FM and IEEE802.11ac signals by DFB-LD and MZM

    Science.gov (United States)

    Teruya, Miku; Chinen, Koyu

    2017-07-01

    We have investigated how wavelength spacing and frequency spacing in WDM (Wavelength Division Multiplexing) and FDM (Frequency Division Multiplexing) using direct modulation lasers (DML) and external modulators of Mach-Zehnder Modulator (MZM) affect optical and electrical interferences. Two signals of 4.8GHz-64QAM-5MHzBW WiMAX and 4.7GHz-32MHzBW FM were directly modulated with uncooled 1550nm DFB-LDs, and 5GHz-256QAM-80MHzBW IEEE802.11ac signal was modulated on the combined optical signals of WiMAX and FM at an MZM. Change in RCE of the WiMAX signal and EVM of the IEEE 802.11ac signal were measured when the wavelength spacing between two DFB-LDs was varied. When the wavelength spacing was larger than 0.05 nm and the ratio of peak to bottom of optical power was larger than 30 dB, the RCE of WiMAX signal was decreased to lower than -20dB. The WDM using directly modulated DFB-LDs and MZM was realized, when the wavelength spacing was larger than 0.1 nm and the peak to bottom ratio of optical power was larger than 60 dB, since the EVM of IEEE802.11ac signal was decreased to around -30dB. The FDM with the same configuration as that of the WDM was realized, when the frequency spacing was larger than a half of the sum of the BWs of WiMAX and FM signals, as the RCE of WiMAX signal decreased to lower than -35 dB and the EVM of IEEE802.11ac signal decreased to around -30dB.

  7. Accurate extraction method for the FM response of tunable diode lasers based on wavelength modulation spectroscopy

    Science.gov (United States)

    Chen, J.; Hangauer, A.; Strzoda, R.; Amann, M.-C.

    2008-02-01

    An accurate wavelength modulation spectroscopy based method to measure the dynamics of the wavelength modulation behavior of tunable diode lasers is introduced in this paper. This method requires only standard equipment and a simple mechanical setup. Under the condition of a constant laser modulation current, the wavelength modulation amplitude can be determined by analysis of the distance between the two zero crossings of the measured second harmonic spectrum of gas absorption. When measuring at different modulation frequencies, the frequency response of the current-to-wavelength tuning coefficient can be obtained. The use of a frequency analyzer instead of a lock-in amplifier to obtain the second harmonic spectrum has two advantages: it provides a higher bandwidth and allows for very precise detection of the zero crossings because of the logarithmic output. The results exhibit very good agreement with a reference measurement performed with a fast FTIR Spectrometer.

  8. A simple frequency sweep linearization method for FM density profile reflectometry

    Science.gov (United States)

    Liu, Adi; Hu, Jianqiang; Doyle, Edward; Zhang, Jin; Li, Hong; Zhou, Chu; Zhang, Xiaohui; Wang, Mingyuan; Lan, Tao; Xie, Jinglin; Liu, Wandong; Yu, Changxuan

    2015-11-01

    Frequency modulated, continuous wave (FMCW) reflectometry is widely used to measure the electron density profile on fusion devices. To ensure the output intermediate frequency signal is proportional to the propagation delay time, the frequency sweep should be linearized, especially for reflectometry with sweeping periods of only a few microseconds. We introduce a simple dynamic calibration technique to linearize the frequency sweep based on digital complex demodulation methods, without using a Fourier transform, which would induce a trade-off between frequency and time resolution. The technique is convenient as it can be done in the same conditions as for plasma measurements. The method is in use on the EAST profile reflectometer, and results will be presented. Work was supported by the Natural Science Foundation of China (NSFC) under 11475173, National Magnetic Confinement Fusion Energy Development Program of China under 2013GB106002 and 2014GB109002, and US DOE Grants DE- SC0010424 and DE-SC0010469.

  9. New pulse modulator with low switching frequency

    Directory of Open Access Journals (Sweden)

    Golub V. S.

    2014-12-01

    Full Text Available The author presents an integrating pulse modulator (analog signal converter with the pulse frequency and duration modulation similar to sigma-delta modulation (with low switching frequency, without quantization. The modulator is characterized by the absence of the quantization noise inherent in sigma-delta modulator, and a low switching frequency, unlike the pulse-frequency modulator. The modulator is recommended, in particular, to convert signals at the input of the class D power amplifier.

  10. High frequency modulation capabilities and quasi single-sideband emission from a quantum cascade laser.

    Science.gov (United States)

    Hangauer, Andreas; Spinner, Georg; Nikodem, Michal; Wysocki, Gerard

    2014-09-22

    Both intensity- (IM) and frequency-modulation (FM) behavior of a directly modulated quantum cascade laser (QCL) are measured from 300 Hz to 1.7 GHz. Quantitative measurements of tuning coefficients has been performed and the transition from thermal- to electronic-tuning is clearly observed. A very specific FM behavior of QCLs has been identified which allows for optical quasi single sideband (SSB) modulation through current injection and has not been observed in directly modulated semiconductor lasers before. This predestines QCLs in applications where SSB is required, such as telecommunication or high speed spectroscopy. The experimental procedure and theoretical modeling for data extraction is discussed.

  11. Radio frequency modulation made easy

    CERN Document Server

    Faruque, Saleh

    2017-01-01

    This book introduces Radio Frequency Modulation to a broad audience. The author blends theory and practice to bring readers up-to-date in key concepts, underlying principles and practical applications of wireless communications. The presentation is designed to be easily accessible, minimizing mathematics and maximizing visuals.

  12. Auditory cortical areas activated by slow frequency-modulated sounds in mice.

    Directory of Open Access Journals (Sweden)

    Yuusuke Honma

    Full Text Available Species-specific vocalizations in mice have frequency-modulated (FM components slower than the lower limit of FM direction selectivity in the core region of the mouse auditory cortex. To identify cortical areas selective to slow frequency modulation, we investigated tonal responses in the mouse auditory cortex using transcranial flavoprotein fluorescence imaging. For differentiating responses to frequency modulation from those to stimuli at constant frequencies, we focused on transient fluorescence changes after direction reversal of temporally repeated and superimposed FM sweeps. We found that the ultrasonic field (UF in the belt cortical region selectively responded to the direction reversal. The dorsoposterior field (DP also responded weakly to the reversal. Regarding the responses in UF, no apparent tonotopic map was found, and the right UF responses were significantly larger in amplitude than the left UF responses. The half-max latency in responses to FM sweeps was shorter in UF compared with that in the primary auditory cortex (A1 or anterior auditory field (AAF. Tracer injection experiments in the functionally identified UF and DP confirmed that these two areas receive afferent inputs from the dorsal part of the medial geniculate nucleus (MG. Calcium imaging of UF neurons stained with fura-2 were performed using a two-photon microscope, and the presence of UF neurons that were selective to both direction and direction reversal of slow frequency modulation was demonstrated. These results strongly suggest a role for UF, and possibly DP, as cortical areas specialized for processing slow frequency modulation in mice.

  13. Intracellular responses to frequency modulated tones in the dorsal cortex of the mouse inferior colliculus

    Directory of Open Access Journals (Sweden)

    Ruediger eGeis

    2013-01-01

    Full Text Available Frequency modulations occur in many natural sounds, including vocalizations. The neuronal response to frequency modulated (FM stimuli has been studied extensively in different brain areas, with an emphasis on the auditory cortex and the central nucleus of the inferior colliculus. Here, we measured the responses to FM sweeps in whole-cell recordings from neurons in the dorsal cortex of the mouse inferior colliculus. Both up- and downward logarithmic FM sweeps were presented at two different speeds to both the ipsi- and the contralateral ear. Based on the number of action potentials that were fired, between 10-24% of cells were selective for rate or direction of the FM sweeps. A somewhat lower percentage of cells, 6-21%, showed selectivity based on EPSP size. To study the mechanisms underlying the generation of FM selectivity, we compared FM responses with responses to simple tones in the same cells. We found that if pairs of neurons responded in a similar way to simple tones, they generally also responded in a similar way to FM sweeps. Further evidence that FM selectivity can be generated within the dorsal cortex was obtained by reconstructing FM sweeps from the response to simple tones using three different models. In about half of the direction selective neurons the selectivity was generated by spectrally asymmetric synaptic inhibition. In addition, evidence for direction selectivity based on the timing of excitatory responses was also obtained in some cells. No clear evidence for the local generation of rate selectivity was obtained. We conclude that FM direction selectivity can be generated within the dorsal cortex of the mouse inferior colliculus by multiple mechanisms.

  14. 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 sig...

  15. Perception of a Sung Vowel as a Function of Frequency-Modulation Rate and Excursion in Listeners with Normal Hearing and Hearing Impairment

    Science.gov (United States)

    Vatti, Marianna; Santurette, Sébastien; Pontoppidan, Niels Henrik; Dau, Torsten

    2014-01-01

    Purpose: Frequency fluctuations in human voices can usually be described as coherent frequency modulation (FM). As listeners with hearing impairment (HI listeners) are typically less sensitive to FM than listeners with normal hearing (NH listeners), this study investigated whether hearing loss affects the perception of a sung vowel based on FM…

  16. Wideband phase-locked loop circuit with real-time phase correction for frequency modulation atomic force microscopy

    OpenAIRE

    Fukuma, Takeshi; Yoshioka, Shunsuke; Asakawa, Hitoshi

    2011-01-01

    We have developed a wideband phase-locked loop (PLL) circuit with real-time phase correction for high-speed and accurate force measurements by frequency modulation atomic force microscopy (FM-AFM) in liquid. A high-speed operation of FM-AFM requires the use of a high frequency cantilever which, however, increases frequency-dependent phase delay caused by the signal delay within the cantilever excitation loop. Such phase delay leads to an error in the force measurements by FM-AFM especially wi...

  17. A Pilot Investigation regarding Speech-Recognition Performance in Noise for Adults with Hearing Loss in the FM+HA Listening Condition

    Science.gov (United States)

    Lewis, M. Samantha; Gallun, Frederick J.; Gordon, Jane; Lilly, David J.; Crandell, Carl

    2010-01-01

    While the concurrent use of the hearing aid (HA) microphone with frequency modulation (FM) technology can decrease speech-recognition performance, the FM+HA condition is still an important setting for users of both HA and FM technology. The primary goal of this investigation was to evaluate the effect of attenuating HA gain in the FM+HA listening…

  18. Autopilot for frequency-modulation atomic force microscopy

    Science.gov (United States)

    Kuchuk, Kfir; Schlesinger, Itai; Sivan, Uri

    2015-10-01

    One of the most challenging aspects of operating an atomic force microscope (AFM) is finding optimal feedback parameters. This statement applies particularly to frequency-modulation AFM (FM-AFM), which utilizes three feedback loops to control the cantilever excitation amplitude, cantilever excitation frequency, and z-piezo extension. These loops are regulated by a set of feedback parameters, tuned by the user to optimize stability, sensitivity, and noise in the imaging process. Optimization of these parameters is difficult due to the coupling between the frequency and z-piezo feedback loops by the non-linear tip-sample interaction. Four proportional-integral (PI) parameters and two lock-in parameters regulating these loops require simultaneous optimization in the presence of a varying unknown tip-sample coupling. Presently, this optimization is done manually in a tedious process of trial and error. Here, we report on the development and implementation of an algorithm that computes the control parameters automatically. The algorithm reads the unperturbed cantilever resonance frequency, its quality factor, and the z-piezo driving signal power spectral density. It analyzes the poles and zeros of the total closed loop transfer function, extracts the unknown tip-sample transfer function, and finds four PI parameters and two lock-in parameters for the frequency and z-piezo control loops that optimize the bandwidth and step response of the total system. Implementation of the algorithm in a home-built AFM shows that the calculated parameters are consistently excellent and rarely require further tweaking by the user. The new algorithm saves the precious time of experienced users, facilitates utilization of FM-AFM by casual users, and removes the main hurdle on the way to fully automated FM-AFM.

  19. Autopilot for frequency-modulation atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kuchuk, Kfir; Schlesinger, Itai; Sivan, Uri, E-mail: phsivan@tx.technion.ac.il [Department of Physics and the Russell Berrie Nanotechnology Institute, Technion - Israel Institute of Technology, Haifa 32000 (Israel)

    2015-10-15

    One of the most challenging aspects of operating an atomic force microscope (AFM) is finding optimal feedback parameters. This statement applies particularly to frequency-modulation AFM (FM-AFM), which utilizes three feedback loops to control the cantilever excitation amplitude, cantilever excitation frequency, and z-piezo extension. These loops are regulated by a set of feedback parameters, tuned by the user to optimize stability, sensitivity, and noise in the imaging process. Optimization of these parameters is difficult due to the coupling between the frequency and z-piezo feedback loops by the non-linear tip-sample interaction. Four proportional-integral (PI) parameters and two lock-in parameters regulating these loops require simultaneous optimization in the presence of a varying unknown tip-sample coupling. Presently, this optimization is done manually in a tedious process of trial and error. Here, we report on the development and implementation of an algorithm that computes the control parameters automatically. The algorithm reads the unperturbed cantilever resonance frequency, its quality factor, and the z-piezo driving signal power spectral density. It analyzes the poles and zeros of the total closed loop transfer function, extracts the unknown tip-sample transfer function, and finds four PI parameters and two lock-in parameters for the frequency and z-piezo control loops that optimize the bandwidth and step response of the total system. Implementation of the algorithm in a home-built AFM shows that the calculated parameters are consistently excellent and rarely require further tweaking by the user. The new algorithm saves the precious time of experienced users, facilitates utilization of FM-AFM by casual users, and removes the main hurdle on the way to fully automated FM-AFM.

  20. Mechanical models of amplitude and frequency modulation

    Energy Technology Data Exchange (ETDEWEB)

    Bellomonte, L; Guastella, I; Sperandeo-Mineo, R M [GRIAF - Research Group on Teaching/Learning Physics, DI.F.TE.R. -Dipartimento di Fisica e Tecnologie Relative, University of Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy)

    2005-05-01

    This paper presents some mechanical models for amplitude and frequency modulation. The equations governing both modulations are deduced alongside some necessary approximations. Computer simulations of the models are carried out by using available educational software. Amplitude modulation is achieved by using a system of two weakly coupled pendulums, whereas the frequency modulation is obtained by using a pendulum of variable length. Under suitable conditions (small oscillations, appropriate initial conditions, etc) both types of modulation result in significantly accurate and visualized simulations.

  1. Frequency Comb Velocity Modulation Spectroscopy

    Science.gov (United States)

    Cossel, Kevin C.; Sinclair, Laura C.; Coffey, Tyler; Cornell, Eric; Ye, Jun

    2011-06-01

    We have developed a novel technique for rapid ion-sensitive spectroscopy over a broad spectral bandwidth by combining the high sensitivity of velocity modulation spectroscopy (VMS) with the parallel nature and high frequency accuracy of cavity-enhanced direct frequency comb spectroscopy. Prior to this research, no techniques have been capable of high sensitivity velocity modulation spectroscopy on every parallel detection channel over such a broad spectral range. We have demonstrated the power of this technique by measuring the A^2Π_u - X^2Σ_g^+ (4,2) band of N_2^+ at 830 nm with an absorption sensitivity of 1×10-6 for each of 1500 simultaneous measurement channels spanning 150 Cm-1. A densely sampled spectrum consisting of interleaved measurements to achieve 75 MHz spacing is acquired in under an hour. This technique is ideally suited for high resolution survey spectroscopy of molecular ions with applications including chemical physics, astrochemistry, and precision measurement. Currently, this system is being used to map the electronic transitions of HfF^+ for the JILA electron electric dipole moment (eEDM) experiment. The JILA eEDM experiment uses trapped molecular ions to significantly increase the coherence time of the measurement in addition to utilizing the strong electric field enhancement available from molecules. Previous theoretical work has shown that the metastable ^3Δ_1 state in HfF^+ and ThF^+ provides high sensitivity to the eEDM and good cancellation of systematic effects; however, the electronic level structure of these species have not previously been measured, and the theoretical uncertainties are hundreds to thousands of wavenumbers. This necessitates broad-bandwidth, high-resolution survey spectroscopy provided by frequency comb VMS in the 700-900 nm spectral window. F. Adler, M. J. Thorpe, K. C. Cossel, and J. Ye. Annu. Rev. Anal. Chem. 3, 175-205 (2010) A. E. Leanhardt, et. al. arXiv:1008.2997v2 E. Meyer, J. L. Bohn, and M. P. Deskevich

  2. Real-time characterization of FM-AM modulation in a high-power laser facility using an RF-photonics system and a denoising algorithm.

    Science.gov (United States)

    Huang, Canhong; Lu, Xinghua; Jiang, Youen; Wang, Xiaochao; Qiao, Zhi; Fan, Wei

    2017-02-20

    FM-AM modulation of high-power lasers significantly affects laser performance. Therefore, precise measurement of the FM-AM modulation depth is necessary. The subsequent FM-AM modulation generated by group velocity dispersion when the laser pulse propagates through a fiber affects the measurement accuracy. In order to eliminate this effect, a waveform-acquisition module is proposed that converts a broad-spectrum pulse of 1053 nm to a narrow-spectrum pulse of 1550 nm, without affecting the waveform. In addition, a signal-processing algorithm based on the orthogonal matching pursuit method is implemented to remove the sampling noise from the waveform. In this way, the signal-to-noise ratio of the measurement can be readily improved. Both theoretical and experimental results indicate that the proposed FM-AM modulation detection system is effective and economical. It can measure the FM-AM modulation depth precisely, and therefore shows considerable promise for future applications in high-power lasers.

  3. Wideband phase-locked loop circuit with real-time phase correction for frequency modulation atomic force microscopy

    Science.gov (United States)

    Fukuma, Takeshi; Yoshioka, Shunsuke; Asakawa, Hitoshi

    2011-07-01

    We have developed a wideband phase-locked loop (PLL) circuit with real-time phase correction for high-speed and accurate force measurements by frequency modulation atomic force microscopy (FM-AFM) in liquid. A high-speed operation of FM-AFM requires the use of a high frequency cantilever which, however, increases frequency-dependent phase delay caused by the signal delay within the cantilever excitation loop. Such phase delay leads to an error in the force measurements by FM-AFM especially with a low Q factor. Here, we present a method to compensate this phase delay in real time. Combined with a wideband PLL using a subtraction-based phase comparator, the method allows to perform an accurate and high-speed force measurement by FM-AFM. We demonstrate the improved performance by applying the developed PLL to three-dimensional force measurements at a mica/water interface.

  4. Amplification of Frequency-Modulated Similariton Pulses in Length-Inhomogeneous Active Fibers

    Directory of Open Access Journals (Sweden)

    I. O. Zolotovskii

    2012-01-01

    Full Text Available The possibility of an effective gain of the self-similar frequency-modulated (FM wave packets is studied in the length-inhomogeneous active fibers. The dynamics of parabolic pulses with the constant chirp has been considered. The optimal profile for the change of the group-velocity dispersion corresponding to the optimal similariton pulse amplification has been obtained. It is shown that the use of FM pulses in the active (gain and length-inhomogeneous optical fibers with the normal group-velocity dispersion can provide subpicosecond optical pulse amplification up to the energies higher than 1 nJ.

  5. Multiple mechanisms shape FM sweep rate selectivity: complementary or redundant?

    Directory of Open Access Journals (Sweden)

    Zoltan M Fuzessery

    2012-08-01

    Full Text Available Auditory neurons in the inferior colliculus (IC of the pallid bat have strong rate selective responses to downward frequency modulated (FM sweeps attributable to the spectrotemporal pattern of their echolocation call (a brief FM pulse. Several mechanisms are known to shape FM rate selectivity within the pallid bat IC. Here we explore how two mechanisms, stimulus duration and high-frequency inhibition (HFI, can interact to shape FM rate selectivity within the same neuron. Results from extracellular recordings indicated that a derived duration-rate function (based on tonal response was highly predictive of the shape of the FM rate response. Longpass duration selectivity for tones was predictive of slowpass rate selectivity for FM sweeps, both of which required long stimulus durations and remained intact following iontophoretic blockade of inhibitory input. Bandpass duration selectivity for tones, sensitive to only a narrow range of tone durations, was predictive of bandpass rate selectivity for FM sweeps. Conversion of the tone duration response from bandpass to longpass after blocking inhibition was coincident with a change in FM rate selectivity from bandpass to slowpass indicating an active inhibitory component to the formation of bandpass selectivity. Independent of the effect of duration tuning on FM rate selectivity, the presence of HFI acted as a fastpass FM rate filter by suppressing slow FM sweep rates. In cases where both mechanisms were present, both had to be eliminated, by removing inhibition, before bandpass FM rate selectivity was affected. It is unknown why the auditory system utilizes multiple mechanisms capable of shaping identical forms of FM rate selectivity though it may represent distinct but convergent modes of neural signaling directed at shaping response selectivity for important biologically relevant sounds.

  6. Signal line shapes of Fourier transform cavity-enhanced frequency modulation spectroscopy with optical frequency combs

    CERN Document Server

    Johansson, Alexandra C; Khodabakhsh, Amir; Foltynowicz, Aleksandra

    2016-01-01

    We present a thorough analysis of the signal line shapes of Fourier transform-based noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS). We discuss the signal dependence on the ratio of the modulation frequency, f${_m}$, to the molecular line width, {\\Gamma}. We compare a full model of the signals and a simplified absorption-like analytical model that has high accuracy for low f${_m}$/{\\Gamma} ratios and is much faster to compute. We verify the theory experimentally by measuring and fitting NICE-OFCS spectra of CO${_2}$ at 1575 nm using a system based on an Er:fiber femtosecond laser and a cavity with a finesse of ~11000.

  7. Theoretical study of the frequency shift in bimodal FM-AFM by fractional calculus

    Directory of Open Access Journals (Sweden)

    Elena T. Herruzo

    2012-03-01

    Full Text Available Bimodal atomic force microscopy is a force-microscopy method that requires the simultaneous excitation of two eigenmodes of the cantilever. This method enables the simultaneous recording of several material properties and, at the same time, it also increases the sensitivity of the microscope. Here we apply fractional calculus to express the frequency shift of the second eigenmode in terms of the fractional derivative of the interaction force. We show that this approximation is valid for situations in which the amplitude of the first mode is larger than the length of scale of the force, corresponding to the most common experimental case. We also show that this approximation is valid for very different types of tip–surface forces such as the Lennard-Jones and Derjaguin–Muller–Toporov forces.

  8. Robust laser frequency stabilization by serrodyne modulation

    CERN Document Server

    Kohlhaas, Ralf; Bernon, Simon; Bertoldi, Andrea; Landragin, Arnaud; Bouyer, Philippe

    2011-01-01

    We report the frequency stabilization of a distributed feedback erbium-doped fiber laser on an optical cavity by serrodyne frequency shifting. A correction bandwidth of 2.4 MHz and a dynamic range of 220 MHz are achieved, which leads to a strong robustness against large disturbances up to high frequencies. Serrodyne frequency shifting allows to use an electro-optical modulator as a fast external transducer with a correction range which exceeds the one of acousto-optical modulators by at least one order of magnitude.

  9. Noise performance of frequency modulation Kelvin force microscopy.

    Science.gov (United States)

    Diesinger, Heinrich; Deresmes, Dominique; Mélin, Thierry

    2014-01-02

    Noise performance of a phase-locked loop (PLL) based frequency modulation Kelvin force microscope (FM-KFM) is assessed. Noise propagation is modeled step by step throughout the setup using both exact closed loop noise gains and an approximation known as "noise gain" from operational amplifier (OpAmp) design that offers the advantage of decoupling the noise performance study from considerations of stability and ideal loop response. The bandwidth can be chosen depending on how much noise is acceptable and it is shown that stability is not an issue up to a limit that will be discussed. With thermal and detector noise as the only sources, both approaches yield PLL frequency noise expressions equal to the theoretical value for self-oscillating circuits and in agreement with measurement, demonstrating that the PLL components neither modify nor contribute noise. Kelvin output noise is then investigated by modeling the surrounding bias feedback loop. A design rule is proposed that allows choosing the AC modulation frequency for optimized sharing of the PLL bandwidth between Kelvin and topography loops. A crossover criterion determines as a function of bandwidth, temperature and probe parameters whether thermal or detector noise is the dominating noise source. Probe merit factors for both cases are then established, suggesting how to tackle noise performance by probe design. Typical merit factors of common probe types are compared. This comprehensive study is an encouraging step toward a more integral performance assessment and a remedy against focusing on single aspects and optimizing around randomly chosen key values.

  10. Modulation frequency and modulation level owing to vocal microtremor.

    Science.gov (United States)

    Schoentgen, Jean

    2002-08-01

    Vocal microtremor designates a normal slow modulation of the vocal cycle lengths of speakers who do not suffer from pathological tremor of the limbs and whose voices are not perceived as tremulous. Vocal microtremor is therefore distinct from pathological vocal tremor. The objective is to report data about the modulation frequency and modulation level owing to vocal microtremor. The modulation data have been obtained for vowels [a], [i], and [u] sustained by normophonic and mildly dysphonic male and female speakers. The results are the following. First, modulation frequencies and relative modulation levels do not differ significantly for male and female speakers, normophonic and mildly dysphonic speakers, as well as for vowel timbres [a], [i], and [u]. Second, the typical interquartile intervals of the modulation frequency and modulation level are equal to 2.0-4.7 Hz and 0.4%-1.3%, respectively. Third, dissimilarities between data reported by different studies are due to different cutoff frequencies below which spectral peaks are considered not to contribute to vocal microtremor.

  11. Laser frequency modulator for modulating a laser cavity

    Science.gov (United States)

    Erbert, Gaylen V.

    1992-01-01

    The present invention relates to a laser frequency modulator for modulating a laser cavity. It is known in the prior art to utilize a PZT (piezoelectric transducer) element in combination with a mirror to change the cavity length of a laser cavity (which changes the laser frequency). Using a PZT element to drive the mirror directly is adequate at frequencies below 10 kHz. However, in high frequency applications (100 kHz and higher) PZT elements alone do not provide a sufficient change in the cavity length. The present invention utilizes an ultrasonic concentrator with a PZT element and mirror to provide modulation of the laser cavity. With an ultrasonic concentrator, the mirror element at the end of a laser cavity can move at larger amplitudes and higher frequencies.

  12. Self-phase modulation induced transmission penalty reduction in a 5 Gbit/s FM/AM conversion system experiment over 205 km of standard fiber

    DEFF Research Database (Denmark)

    Jørgensen, Bo Foged; Pedersen, Rune Johan Skullerud; Jørgensen, Carsten Gudmann

    1994-01-01

    The transmission penalty of a standard non-dispersion shifted fiber is experimentally demonstrated to be reduced by self-phase modulation due to the optical Kerr effect. A 2 dB reduction of transmission penalty is achieved in a 5 Gbit/s FM/AM conversion system experiment over 205 km of fiber...

  13. Spread Spectrum Communication with Chaotic Frequency Modulation

    Science.gov (United States)

    Volkovskii, Alexander R.; Tsimring, Lev S.; Rulkov, Nikolai F.; Langmore, Ian; Young, Stephen C.

    We describe two different approaches to employ chaotic signals in spread-spectrum (SS) communication systems with phase and frequency modulation. In the first one a chaotic signal is used as a carrier. We demonstrate that using a feedback loop controller, the local chaotic oscillator in the receiver can be synchronized to the transmitter. The information can be transmitted using phase or frequency modulation of the chaotic carrier signal. In the second system the chaotic signal is used for frequency modulation of a voltage controlled oscillator (VCO) to provide a SS signal similar to frequency hopping systems. We show that in a certain parameter range the receiver VCO can be synchronized to the transmitter VCO using a relatively simple phase lock loop (PLL) circuit. The same PLL is used for synchronization of the chaotic oscillators. The information signal can be transmitted using a binary phase shift key (BPSK) or frequency shift key (BFSK) modulation of the frequency modulated carrier signal. Using an experimental circuit operating at radio frequency band and a computer modeling we study the bit error rate (BER) performance in a noisy channel as well as multiuser capability of the system.

  14. Accurate encoding and decoding by single cells: amplitude versus frequency modulation.

    Directory of Open Access Journals (Sweden)

    Gabriele Micali

    2015-06-01

    Full Text Available Cells sense external concentrations and, via biochemical signaling, respond by regulating the expression of target proteins. Both in signaling networks and gene regulation there are two main mechanisms by which the concentration can be encoded internally: amplitude modulation (AM, where the absolute concentration of an internal signaling molecule encodes the stimulus, and frequency modulation (FM, where the period between successive bursts represents the stimulus. Although both mechanisms have been observed in biological systems, the question of when it is beneficial for cells to use either AM or FM is largely unanswered. Here, we first consider a simple model for a single receptor (or ion channel, which can either signal continuously whenever a ligand is bound, or produce a burst in signaling molecule upon receptor binding. We find that bursty signaling is more accurate than continuous signaling only for sufficiently fast dynamics. This suggests that modulation based on bursts may be more common in signaling networks than in gene regulation. We then extend our model to multiple receptors, where continuous and bursty signaling are equivalent to AM and FM respectively, finding that AM is always more accurate. This implies that the reason some cells use FM is related to factors other than accuracy, such as the ability to coordinate expression of multiple genes or to implement threshold crossing mechanisms.

  15. Behavioral and Molecular Genetics of Reading-Related AM and FM Detection Thresholds.

    Science.gov (United States)

    Bruni, Matthew; Flax, Judy F; Buyske, Steven; Shindhelm, Amber D; Witton, Caroline; Brzustowicz, Linda M; Bartlett, Christopher W

    2017-03-01

    Auditory detection thresholds for certain frequencies of both amplitude modulated (AM) and frequency modulated (FM) dynamic auditory stimuli are associated with reading in typically developing and dyslexic readers. We present the first behavioral and molecular genetic characterization of these two auditory traits. Two extant extended family datasets were given reading tasks and psychoacoustic tasks to determine FM 2 Hz and AM 20 Hz sensitivity thresholds. Univariate heritabilities were significant for both AM (h (2)  = 0.20) and FM (h (2)  = 0.29). Bayesian posterior probability of linkage (PPL) analysis found loci for AM (12q, PPL = 81 %) and FM (10p, PPL = 32 %; 20q, PPL = 65 %). Bivariate heritability analyses revealed that FM is genetically correlated with reading, while AM was not. Bivariate PPL analysis indicates that FM loci (10p, 20q) are not also associated with reading.

  16. Frequency Modulation Induced by using the Linear Phase Modulation Method used in a Resonator Micro-optic Gyro

    Institute of Scientific and Technical Information of China (English)

    HONG Ling-Fei; ZHANG Chun-Xi; FENG Li-Shuang; YU Huai-Yong; LEI Ming

    2012-01-01

    Resonator micro-optic gyro (R-MOG) sensing rotation angular-velocity is based on Sagnac effect.We present a frequency modulation (FM) induced by the analog triangle-waveform phase modulation (ATAW-PM) technique in an R-MOG.Compared with the traditional serrodyne phase modulation or digital phase modulation methods,the proposed modulation technique has the intrinsic advantage in free of sweeping-back or step-effect induced pulse noise.The influence on dynamic range and resolution of the R-MOG by the parameters of analog trianglewaveform is theoretically analyzed.Experiments are carried out on an R-MOG composed of an integrated optic resonator with a free spectral range (FSR) and a fitness (F) of 1.6GHz and 61,respectively.Dynamic range of ±500 deg/s and bias drift of 0.6 deg/s over 1 h and 0.05 deg/s for 60 s are reliably obtained.%Resonator micro-optic gyro (R-MOG) sensing rotation angular-velocity is based on Sagnac effect. We present a frequency modulation (FM) induced by the analog triangle-waveform phase modulation (ATAW-PM) technique in an R-MOG. Compared with the traditional serrodyne phase modulation or digital phase modulation methods, the proposed modulation technique has the intrinsic advantage in free of sweeping-back or step-effect induced pulse noise. The influence on dynamic range and resolution of the R-MOG by the parameters of analog triangle-waveform is theoretically analyzed. Experiments are carried out on an R-MOG composed of an integrated optic resonator with a free spectral range (FSR) and a Btness (F) of 1.6 GHz and 61, respectively. Dynamic range of ±500 deg/s and bias drift of 0.6deg/s over 1 h and 0.05deg/s for 60s are reliably obtained.

  17. Modified Range-Doppler Processing for FM-CW Synthetic Aperture Radar

    NARCIS (Netherlands)

    Wit, J.J.M. de; Meta, A.; Hoogeboom, P.

    2006-01-01

    The combination of compact frequency-modulated continuous-wave (FM-CW) technology and high-resolution synthetic aperture radar (SAR) processing techniques should pave the way for the development of a lightweight, cost-effective, high-resolution, airborne imaging radar. Regarding FM-CW SAR signal pro

  18. Digital Demodulation Algorithm for Multi-Tone FM Signal in New Type Track Circuit

    Institute of Scientific and Technical Information of China (English)

    ZHU Lin-xiao; WU Si-liang

    2006-01-01

    The multi-tone frequency modulation (FM) signal transferred through track circuit in automatic train control (ATC) system is analyzed. A digital filter with ideal sloping shape in frequency domain is designed for frequency discrimination. With this filter, the FM signal is converted into AM-FM signal by frequency-to-amplitude conversion. The modulating signal is finally extracted from the envelope of the AM-FM signal. Simulations show that the digital demodulation method could accurately recover the modulating signal in low signal noise ratio (SNR) circumstance, and has good performance in suppressing interference of harmonics of traction current frequency. The feasibility of the proposed method is proved in a hardware system based on SHARC DSP.

  19. Tunable Twin Matching Frequency (fm1/fm2) Behavior of Ni1‑xZnxFe2O4/NBR Composites over 2–12.4 GHz: A Strategic Material System for Stealth Applications

    Science.gov (United States)

    Saini, Lokesh; Patra, Manoj Kumar; Jani, Raj Kumar; Gupta, Goutam Kumar; Dixit, Ambesh; Vadera, Sampat Raj

    2017-03-01

    The gel to carbonate precipitate route has been used for the synthesis of Ni1‑xZnxFe2O4 (x = 0, 0.25, 0.5 and 0.75) bulk inverse spinel ferrite powder samples. The optimal zinc (50%) substitution has shown the maximum saturation magnetic moment and resulted into the maximum magnetic loss tangent (tanδm) > ‑1.2 over the entire 2–10 GHz frequency range with an optimum value ~‑1.75 at 6 GHz. Ni0.5Zn0.5Fe2O4- Acrylo-Nitrile Butadiene Rubber (NBR) composite samples are prepared at different weight percentage (wt%) of ferrite loading fractions in rubber for microwave absorption evaluation. The 80 wt% loaded Ni0.5Zn0.5Fe2O4/NBR composite (FMAR80) sample has shown two reflection loss (RL) peaks at 5 and 10 GHz. Interestingly, a single peak at 10 GHz for 3.25 mm thickness, can be scaled down to 5 GHz by increasing the thickness up to 4.6 mm. The onset of such twin matching frequencies in FMAR80 composite sample is attributed to the spin resonance relaxation at ~5 GHz (fm1) and destructive interference at λm/4 matched thickness near ~10 GHz (fm2) in these composite systems. These studies suggest the potential of tuning the twin frequencies in Ni0.5Zn0.5Fe2O4/NBR composite samples for possible microwave absorption applications.

  20. Analysis of intra-pulse frequency-modulated, low probability of interception, radar signals

    Indian Academy of Sciences (India)

    A R SACHIN; SOORAJ K AMBAT; K V S HARI

    2017-07-01

    In this paper, we investigate the problem of analysis of low probability of interception (LPI) radar signals with intra-pulse frequency modulation (FM) under low signal-to-noise ratio conditions from the perspective of an airborne electronic warfare (EW) digital receiver. EW receivers are designed to intercept andanalyse threat radar signals of different classes, received over large dynamic range and operating independently over large geographical spread to advice host aircraft to undertake specified actions. For an EW receiver, primary challenges in interception and analysis of LPI radar signals are low received power, intra-pulse modulations,multi-octave frequency range, wide signal bandwidth, long pulse width, vast and multi-parametric search space, etc. In the present work, a method based on match filterbank localization and Taylor’s seriesapproximation for analysing the entire family of intra-pulse FM radar signals is proposed. The method involves progressive, joint time–frequency (TF) localization of the signal of interest (SOI), under piecewise linearity andcontinuity assumptions on instantaneous frequency, to effectively capture local TF signatures. Detection is by information-theoretic criterion based hypotheses testing, while estimation and classification are based on polynomial approximation. Fine signal analysis is followed by synthetic reconstruction of the received signal slope. Detection, estimation and classification performances for the prominent FM radar signal classes are quantified based on simulation study statistics. Stagewise implementation of analysis and FM slope reconstruction,in realistic radar threat scenarios, is demonstrated for the potential SOIs. Subject discussion is organized from the perspective of practical EW system design and presented within the realm of signal processing architecture of concurrent EW digital receivers.Keywords. Digital receiver (DRx); electronic warfare (

  1. Toward automatic phenotyping of retinal images from genetically determined mono- and dizygotic twins using amplitude modulation-frequency modulation methods

    Science.gov (United States)

    Soliz, P.; Davis, B.; Murray, V.; Pattichis, M.; Barriga, S.; Russell, S.

    2010-03-01

    This paper presents an image processing technique for automatically categorize age-related macular degeneration (AMD) phenotypes from retinal images. Ultimately, an automated approach will be much more precise and consistent in phenotyping of retinal diseases, such as AMD. We have applied the automated phenotyping to retina images from a cohort of mono- and dizygotic twins. The application of this technology will allow one to perform more quantitative studies that will lead to a better understanding of the genetic and environmental factors associated with diseases such as AMD. A method for classifying retinal images based on features derived from the application of amplitude-modulation frequency-modulation (AM-FM) methods is presented. Retinal images from identical and fraternal twins who presented with AMD were processed to determine whether AM-FM could be used to differentiate between the two types of twins. Results of the automatic classifier agreed with the findings of other researchers in explaining the variation of the disease between the related twins. AM-FM features classified 72% of the twins correctly. Visual grading found that genetics could explain between 46% and 71% of the variance.

  2. Noise performance of frequency modulation Kelvin force microscopy

    Directory of Open Access Journals (Sweden)

    Heinrich Diesinger

    2014-01-01

    Full Text Available Noise performance of a phase-locked loop (PLL based frequency modulation Kelvin force microscope (FM-KFM is assessed. Noise propagation is modeled step by step throughout the setup using both exact closed loop noise gains and an approximation known as “noise gain” from operational amplifier (OpAmp design that offers the advantage of decoupling the noise performance study from considerations of stability and ideal loop response. The bandwidth can be chosen depending on how much noise is acceptable and it is shown that stability is not an issue up to a limit that will be discussed. With thermal and detector noise as the only sources, both approaches yield PLL frequency noise expressions equal to the theoretical value for self-oscillating circuits and in agreement with measurement, demonstrating that the PLL components neither modify nor contribute noise. Kelvin output noise is then investigated by modeling the surrounding bias feedback loop. A design rule is proposed that allows choosing the AC modulation frequency for optimized sharing of the PLL bandwidth between Kelvin and topography loops. A crossover criterion determines as a function of bandwidth, temperature and probe parameters whether thermal or detector noise is the dominating noise source. Probe merit factors for both cases are then established, suggesting how to tackle noise performance by probe design. Typical merit factors of common probe types are compared. This comprehensive study is an encouraging step toward a more integral performance assessment and a remedy against focusing on single aspects and optimizing around randomly chosen key values.

  3. Demodulation effect is observed in neurones by exposure to low frequency modulated microwaves

    Science.gov (United States)

    Pérez-Bruzón, R. N.; Figols, T.; Azanza, M. J.; del Moral, A.

    2010-01-01

    Neurones exposure to a microwave (carrier fc=13.6 GHz; power P simeq 5 mW; Ho simeq 0.10 Am-1 = 1.25 mOe; E0 simeq 3.5 V/m; ΔT simeq 0.01°C SAR: 3.1×10-3 - 5.8×10-3 W/Kg) EMF amplitude modulated by ELF-AC field (frequency, fm= 0-100 Hz) shows no electrophysiological effect under the carrier MF alone, but "frequency resonances: at 2, 4, 8, 12, 16, 50, 100 Hz: demodulation effect. Resonances appear when applied ELF-MF is close to a dominant characteristic frequency of the neurone impulse Fourier spectrum. This is an interesting result considering that ELF-MF modulating RF or MW in the range of human EEG could induce frequency-resonant effects on exposed human brain.

  4. Tradeoff between User Experience and BCI Classification Accuracy with Frequency Modulated Steady-State Visual Evoked Potentials.

    Science.gov (United States)

    Dreyer, Alexander M; Herrmann, Christoph S; Rieger, Jochem W

    2017-01-01

    Steady-state visual evoked potentials (SSVEPs) have been widely employed for the control of brain-computer interfaces (BCIs) because they are very robust, lead to high performance, and allow for a high number of commands. However, such flickering stimuli often also cause user discomfort and fatigue, especially when several light sources are used simultaneously. Different variations of SSVEP driving signals have been proposed to increase user comfort. Here, we investigate the suitability of frequency modulation of a high frequency carrier for SSVEP-BCIs. We compared BCI performance and user experience between frequency modulated (FM) and traditional sinusoidal (SIN) SSVEPs in an offline classification paradigm with four independently flickering light-emitting diodes which were overtly attended (fixated). While classification performance was slightly reduced with the FM stimuli, the user comfort was significantly increased. Comparing the SSVEPs for covert attention to the stimuli (without fixation) was not possible, as no reliable SSVEPs were evoked. Our results reveal that several, simultaneously flickering, light emitting diodes can be used to generate FM-SSVEPs with different frequencies and the resulting occipital electroencephalography (EEG) signals can be classified with high accuracy. While the performance we report could be further improved with adjusted stimuli and algorithms, we argue that the increased comfort is an important result and suggest the use of FM stimuli for future SSVEP-BCI applications.

  5. Detecting deception via eyeblink frequency modulation

    Directory of Open Access Journals (Sweden)

    Brandon S. Perelman

    2014-02-01

    Full Text Available To assess the efficacy of using eyeblink frequency modulation to detect deception about a third party, 32 participants were sent on a mission to deliver a package to an interviewer. 17 of the participants lied to the interviewer about the details of their mock mission and 15 responded truthfully. During the interview, eyeblink frequency data were collected via electromyography and recorded video. Liars displayed eyeblink frequency suppression while lying, while truth tellers exhibited an increase in eyeblink frequency during the mission relevant questioning period. The compensatory flurry of eyeblinks following deception observed in previous studies was absent in the present study. A discriminant function using eyeblink suppression to predict lying correctly classified 81.3% of cases, with a sensitivity of 88.2% and a specificity of 73.3%. This technique, yielding a reasonable sensitivity, shows promise for future testing as, unlike polygraph, it is compatible with distance technology.

  6. Frequency comb velocity-modulation spectroscopy.

    Science.gov (United States)

    Sinclair, Laura C; Cossel, Kevin C; Coffey, Tyler; Ye, Jun; Cornell, Eric A

    2011-08-26

    We have demonstrated a new technique that provides massively parallel comb spectroscopy sensitive specifically to ions through the combination of cavity-enhanced direct frequency comb spectroscopy with velocity-modulation spectroscopy. Using this novel system, we have measured electronic transitions of HfF⁺ and achieved a fractional absorption sensitivity of 3×10⁻⁷ recorded over 1500 simultaneous channels spanning 150  cm⁻¹ around 800 nm with an absolute frequency accuracy of 30 MHz (0.001  cm⁻¹). A fully sampled spectrum consisting of interleaved measurements is acquired in 30 min.

  7. Frequency Comb Velocity-Modulation Spectroscopy

    CERN Document Server

    Sinclair, Laura C; Coffey, Tyler; Ye, Jun; Cornell, Eric A

    2011-01-01

    We have demonstrated a new technique that provides massively parallel comb spectroscopy sensitive specifically to ions through the combination of cavity-enhanced direct frequency comb spectroscopy with velocity modulation spectroscopy. Using this novel system, we have measured electronic transitions of HfF+ and achieved a fractional absorption sensitivity of 3 x 10-7 recorded over 1500 simultaneous channels spanning 150 cm-1 around 800 nm with an absolute frequency accuracy of 30 MHz (0.001 cm-1). A fully sampled spectrum consisting of interleaved measurements is acquired in 30 minutes.

  8. An amplitude modulated radio frequency plasma generator

    Science.gov (United States)

    Lei, Fan; Li, Xiaoping; Liu, Yanming; Liu, Donglin; Yang, Min; Xie, Kai; Yao, Bo

    2017-04-01

    A glow discharge plasma generator and diagnostic system has been developed to study the effects of rapidly variable plasmas on electromagnetic wave propagation, mimicking the plasma sheath conditions encountered in space vehicle reentry. The plasma chamber is 400 mm in diameter and 240 mm in length, with a 300-mm-diameter unobstructed clear aperture. Electron densities produced are in the mid 1010 electrons/cm3. An 800 W radio frequency (RF) generator is capacitively coupled through an RF matcher to an internally cooled stainless steel electrode to form the plasma. The RF power is amplitude modulated by a waveform generator that operates at different frequencies. The resulting plasma contains electron density modulations caused by the varying power levels. A 10 GHz microwave horn antenna pair situated on opposite sides of the chamber serves as the source and detector of probe radiation. The microwave power feed to the source horn is split and one portion is sent directly to a high-speed recording oscilloscope. On mixing this with the signal from the pickup horn antenna, the plasma-induced phase shift between the two signals gives the path-integrated electron density with its complete time dependent variation. Care is taken to avoid microwave reflections and extensive shielding is in place to minimize electronic pickup. Data clearly show the low frequency modulation of the electron density as well as higher harmonics and plasma fluctuations.

  9. 基于RK2808的平板电脑FM收音模块设计%Design of FM Radio Module Based on RK2808 Tablet PC

    Institute of Scientific and Technical Information of China (English)

    王全宇; 覃志东; 齐蓓; 覃小红

    2011-01-01

    针对FM收音是许多消费电子的必备功能以及平板电脑的技术发展趋势,基于RK2808平板电脑解决方案,设计实现了FM收音模块.该模块采用SCT-806芯片,设计了相应外围电路及设备的驱动程序;模块应用程序的设计则结合了多种设计模式框架和多线程技术.所实现的FM收音模块操作界面友好简单,实用性强,成本低.%Under the consideration that FM radio is the essential function of many electronic consuming products and developing trends of tablet PC techniques,FM radio module was designed and realized based on the solving scheme of RK2808 tablet PC,which used SCT-806 chip and designed relevant peripheral circuits and hardware drivers.The design of the module's application combined various design patterns and multithread technology.The results show that the accomplished FM module has friendly and simple UI,good practicability and low cost.

  10. Modulation of induced frontocentral theta (Fm-θ) event-related (de-)synchronisation dynamics following mindfulness-based cognitive therapy in Major Depressive Disorder.

    Science.gov (United States)

    Schoenberg, Poppy L A; Speckens, Anne E M

    2014-10-01

    Depressive severity has been associated with attenuated neocortical frontal midline theta (Fm-θ) power/evoked activity. Mindfulness-Based Cognitive Therapy (MBCT) has shown to be a successful novel intervention for Major Depressive Disorder (MDD), albeit precise working mechanisms remain elusive. We examined the hypothesis that MBCT would have modulating effects upon evoked Fm-θ power, in addition to investigating possible mediation of induced event-related de/synchronisation (ERD/ERS) dynamics. Fifty one patients with a primary diagnosis of MDD (26 exposed to MBCT vs. 25 wait-list/WL controls) undertook a Go/NoGo task consisting of positive, negative and neutral words, further stratified into abstract versus trait adjective matrices. Depressive symptom severity and rumination were also examined. A pattern of enhanced induced Fm-θ synchronisation during the latter 400-800 ms temporal-window pre-to-post MBCT was observed; the contrary in the WL. Modulated ERD/ERS dynamics correlated to amelioration in depressive and rumination symptoms in the MBCT group. We propose the primary action pathway alluded to a neural disengagement mechanism enacting upon tonic neuronal assemblies implicated in emotional and self-related processing. Due to the complexity and presently undiscovered complete unified scientific understanding of neuro-oscillatory-dynamics, and associated clinical interplays; we hypothesise that the electro-cortical and connected clinical working pathways of MBCT in depression are multi-levelled constituting nonlinear and interdependent mechanisms, represented by mediated EEG synchronisation dynamics.

  11. An analysis of the autodyne effect of oscillators with linear frequency modulation

    Science.gov (United States)

    Votoropin, S. D.; Noskov, V. Ya.; Smolskiy, S. M.

    2008-06-01

    General equations are obtained for the autodyne response in the case of an arbitrary frequency modulation both over the active element bias circuit and voltage variation on the voltage-dependent capacitor (varicap). The results of investigation of an autodyne oscillator with linear frequency modulation following the antisymmetric and symmetric saw-tooth function are presented, with the oscillator being affected by its own reflected radiation. Special features of self-oscillations of such autodynes are considered, with the aim to improve their characteristics and extend the functional capabilities of short-range autodyne radars. The experimental results obtained for the TIGEL 08FM oscillator module manufactured using a hybrid-integral technology on the basis of a mm-range Gunn diode are reported.

  12. [IM/FM phase delay time measurement method of laser for TDLAS].

    Science.gov (United States)

    Zhang, Chao; Ma, Wei-Guang

    2014-11-01

    The present paper presents an method of using fiber Michelson interferometer to measure the Intensity-frequency (IM/FM) phase delay change of the laser, it could realize the phase delay time measurement, while modulating the laser. Experimental results show that the laser output signal intensity-frequency (IM/FM) phase delay of the laser has some differences from the theoretical value. The proposed method can be used to compensate for real-time signal strength-frequency (IM/FM) phase delay effect on the gas concentration measurement results.

  13. RetFM-J, an ImageJ-based module for automated counting and quantifying features of nuclei in retinal whole-mounts.

    Science.gov (United States)

    Hedberg-Buenz, Adam; Christopher, Mark A; Lewis, Carly J; Meyer, Kacie J; Rudd, Danielle S; Dutca, Laura M; Wang, Kai; Garvin, Mona K; Scheetz, Todd E; Abràmoff, Michael D; Harper, Matthew M; Anderson, Michael G

    2016-05-01

    The present article introduces RetFM-J, a semi-automated ImageJ-based module that detects, counts, and collects quantitative data on nuclei of the inner retina from H&E-stained whole-mounted retinas. To illustrate performance, computer-derived outputs were analyzed in inbred C57BL/6J mice. Automated characterization yielded computer-derived outputs that closely matched manual counts. As a method using open-source software that is freely available, inexpensive staining reagents that are robust, and imaging equipment that is routine to most laboratories, RetFM-J could be utilized in a wide variety of experiments benefiting from high-throughput, quantitative, uniform analyses of total cellularity in the inner retina.

  14. Time analysis and processing of FM-CW signals

    NARCIS (Netherlands)

    Meta, A.; Hoogeboom, P.

    2003-01-01

    Combining frequency modulated continuous wave (FM-CW) teehnology with synthetic aperture radar (SAR) methods leads to a cost-effective, high resolution imaging radar for smallscale applications. There is a growing interest in miniaturized versions of such sysfems. The radar delivers its output in th

  15. The use of phase modulation optimization for power lasers. Minimizing the FM-AM conversion while preserving spectral broadening functionalities required for fusion; Optimisation de la modulation de phase utilisee pour les lasers de puissance. Minimisation de la conversion FM-AM tout en conservant les fonctionnalites d'elargissement spectral necessaires a la fusion

    Energy Technology Data Exchange (ETDEWEB)

    Hocquet, St

    2009-11-15

    This research thesis deals with the problem of phase modulations in power lasers (such as the MegaJoule laser which is developed in France) and their impact of different physical phenomena like the suppression of the stimulated Brillouin scattering (which is necessary to avoid optics damage) and the optical smoothing which allows a spatial homogenisation of focal stains. The author deeply discusses the phase modulation counterparts, and more particularly the FM-AM conversion which is the source of unwanted intensity modulation and of energy loss. He reports the development of a comprehensive modelling of phenomena generating FM-AM conversion on a power laser chain. He theoretically and experimentally studies two methods allowing the FM-AM conversion to be reduced to a given spectral distortion: the compensation of transfer functions and the modification of the phase modulation signal to make it less sensitive to spectral distortion effects. For this last method, he determines the ideal spectrum shape for the phase modulation, and proposes a method to approach it. He shows the feasibility of such a method and reports experiments showing to which extent these solutions may improve performance of power lasers. Finally, he proposed optimised solutions for the MegaJoule Laser.

  16. A low noise all-fiber interferometer for high resolution frequency modulated atomic force microscopy imaging in liquids.

    Science.gov (United States)

    Rasool, Haider I; Wilkinson, Paul R; Stieg, Adam Z; Gimzewski, James K

    2010-02-01

    We have developed a low noise all-fiber interferometer for use as the deflection sensor in liquid environment frequency modulated atomic force microscopy (FM-AFM). A detailed description and rationale for the choice of the critical components are provided along with the design of a simple alignment assembly. The optimization of the deflection sensor toward achieving the highest possible sensitivity and lowest deflection noise density is discussed in the context of an ideal interference cavity. Based on the provided analysis we have achieved deflection noise densities of 2 fm/square root(Hz) on commercially available cantilevers in both ambient and liquid environments. The low noise interferometer works without the need for differential detection, special focusing lenses, or polarization sensitive optics, dramatically simplifying measurements. True atomic resolution imaging of muscovite mica by FM-AFM in water is demonstrated using the developed deflection sensor.

  17. Absolute frequency synthesis of pulsed coherent light waves through phase-modulation active optical feedback.

    Science.gov (United States)

    Shimizu, K; Horiguchi, T; Koyamada, Y

    1996-11-15

    A novel method for the broadband absolute frequency synthesis of pulsed coherent lightwaves is demonstrated. It is based on pulse recirculation around an active optical feedback ring containing a delay-line fiber, an external phase modulator, an acousto-optic frequency shifter (AOFS), and a high-finesse Fabry-Perot étalon. The modulation frequency F(M) and the frequency shift F(AO) that are due to AOFS are designed so that their sum or difference equals the free-spectral range of the étalon and F(AO) is set at larger than the half-width at full maximum of its resonant peaks. If one of the peak frequencies is tuned to the frequency of the initial pulse, the frequency of the recirculating pulse jumps to the next peak for each round trip. In the experiment the absolute frequency is synthesized over a frequency span of 700 GHz around the initial stabilized frequency of the master laser.

  18. FY05 FM Dial Summary Report

    Energy Technology Data Exchange (ETDEWEB)

    Harper, Warren W.; Strasburg, Jana D.; Golovich, Elizabeth C.; Thompson, Jason S.; Stewart, Timothy L.; Batdorf, Michael T.

    2005-12-01

    Pacific Northwest National Laboratory's Infrared Sensors team is focused on developing methods for standoff detection of nuclear proliferation. In FY05, PNNL continued the development of the FM DIAL (frequency-modulated differential absorption LIDAR) experiment. Additional improvements to the FM DIAL trailer provided greater stability during field campaigns which made it easier to explore new locations for field campaigns. In addition to the Hanford Townsite, successful experiments were conducted at the Marine Science Laboratory in Sequim, WA and the Nevada Test Site located outside Las Vegas, NV. The range of chemicals that can be detected by FM DIAL has also increased. Prior to FY05, distributed feedback quantum cascade lasers (DFB-QCL) were used in the FM DIAL experiments. With these lasers, only simple chemicals with narrow (1-2 cm-1) absorption spectra, such as CO2 and N2O, could be detected. Fabry-Perot (FP) QC lasers have much broader spectra (20-40 cm-1) which allows for the detection of larger chemicals and a wider array of chemicals that can be detected. A FP-QCL has been characterized and used during initial studies detecting DMMP (dimethyl methylphosphonate).

  19. Comparison of photothermal and piezoacoustic excitation methods for frequency and phase modulation atomic force microscopy in liquid environments

    Directory of Open Access Journals (Sweden)

    A. Labuda

    2011-06-01

    Full Text Available In attempting to perform frequency modulation atomic force microscopy (FM-AFM in liquids, a non-flat phase transfer function in the self-excitation system prevents proper tracking of the cantilever natural frequency. This results in frequency-and-phase modulation atomic force microscopy (FPM-AFM which lies in between phase modulation atomic force microscopy (PM-AFM and FM-AFM. We derive the theory necessary to recover the conservative force and damping in such a situation, where standard FM-AFM theory no longer applies. Although our recovery procedure applies to all cantilever excitation methods in principle, its practical implementation may be difficult, or even impossible, if the cantilever is driven piezoacoustically. Specifically, we contrast the piezoacoustic excitation method to the photothermal method in the context of force spectroscopy of hydration structures at the mica-water interface. The results clearly demonstrate that photothermal excitation is superior to piezoacoustic excitation, as it allows for accurate quantitative interpretation of the acquired data.

  20. An Asymmetry in the Automatic Detection of the Presence or Absence of a Frequency Modulation within a Tone: A Mismatch Negativity Study

    Science.gov (United States)

    Timm, Jana; Weise, Annekathrin; Grimm, Sabine; Schröger, Erich

    2011-01-01

    The infrequent occurrence of a transient feature (deviance; e.g., frequency modulation, FM) in one of the regular occurring sinusoidal tones (standards) elicits the deviance related mismatch negativity (MMN) component of the event-related brain potential. Based on a memory-based comparison, MMN reflects the mismatch between the representations of incoming and standard sounds. The present study investigated to what extent the infrequent exclusion of an FM is detected by the MMN system. For that purpose we measured MMN to deviances that either consisted of the exclusion or inclusion of an FM at an early or late position within the sound that was present or absent, respectively, in the standard. According to the information-content hypothesis, deviance detection relies on the difference in informational content of the deviant relative to that of the standard. As this difference between deviants with FM and standards without FM is the same as in the reversed case, comparable MMNs should be elicited to FM inclusions and exclusions. According to the feature-detector hypothesis, however, the deviance detection depends on the increased activation of feature detectors to additional sound features. Thus, rare exclusions of the FM should elicit no or smaller MMN than FM inclusions. In passive listening condition, MMN was obtained only for the early inclusion, but not for the exclusions nor for the late inclusion of an FM. This asymmetry in automatic deviance detection seems to partly reflect the contribution of feature detectors even though it cannot fully account for the missing MMN to late FM inclusions. Importantly, the behavioral deviance detection performance in the active listening condition did not reveal such an asymmetry, suggesting that the intentional detection of the deviants is based on the difference in informational content. On a more general level, the results partly support the “fresh-afferent” account or an extended memory-comparison based account of MMN

  1. Analysis of Coexistence of DRM Plus and FM Broadcasting Systems

    Directory of Open Access Journals (Sweden)

    K. Ulovec

    2015-12-01

    Full Text Available This paper deals with DRM (Digital Radio Mondiale Plus and FM (Frequency Modulation radio broadcasting systems coexistence. It brings results based on measurement of mutual interferences of each to other. Minimal necessary value of the signal to interference power ratio is measured under the given reception criteria. Results are useful for broadcasting networks planning. Different DRM Plus modes (i.e. combinations of various protection levels and data carriers modulations are assumed in the case of DRM Plus reception interfered with by FM broadcasting. The differences for various modes are crucial for coverage design of DRM Plus system, while protection ratios have been recommended for only two of eight modes until now. Corrections of protection ratios for other modes are proposed in this paper. Different waveforms types of modulating signal for interfering FM signal are tested. The both mono and stereo FM mode and various sound quality criteria are considered in the case of FM broadcasting reception interfered with by DRM Plus. The influence of peak to average power ratio reduction of interfering DRM Plus signal is observed.

  2. Monitoring lipid accumulation in the green microalga Botryococcus braunii with frequency-modulated stimulated Raman scattering

    Science.gov (United States)

    Wang, Chun-Chin; Chandrappa, Dayananda; Smirnoff, Nicholas; Moger, Julian

    2015-03-01

    The potential of microalgae as a source of renewable energy has received considerable interest because they can produce lipids (fatty acids and isoprenoids) that can be readily converted into biofuels. However, significant research in this area is required to increase yields to make this a viable renewable source of energy. An analytical tool that could provide quantitative in situ spectroscopic analysis of lipids synthesis in individual microalgae would significantly enhance our capability to understand the synthesis process at the cellular level and lead to the development of strategies for increasing yield. Stimulated Raman scattering (SRS) microscopy has great potential in this area however, the pump-probe signal from two-color two-photon absorption of pigments (chlorophyll and carotenoids) overwhelm the SRS signal and prevent its application. Clearly, the development of a background suppression technique is of significant value for this important research area. To overcome the limitation of SRS in pigmented specimens, we establish a frequency-modulated stimulated Raman scattering (FM-SRS) microscopy that eliminates the non-Raman background by rapidly toggling on-and-off the targeted Raman resonance. Moreover, we perform the background-free imaging and analysis of intracellular lipid droplets and extracellular hydrocarbons in a green microalga with FM-SRS microscopy. We believe that FM-SRS microscopy demonstrates the potential for many applications in pigmented cells and provides the opportunity for improved selective visualization of the chemical composition of algae and plants

  3. Spectral Features of FM Spectroscopy of Two-Photon Interactions

    Institute of Scientific and Technical Information of China (English)

    夏慧荣; JohnL.Hall

    1994-01-01

    The spectral features of FM two-photon resonant interaction processes have been calculated for five different frequency modulation versions of counter-propagating incident fields. It is found that the proposed new modulation version (case b in the text) provides novel spectral features for a completely canceled absorption and a sharp dispersion shape at the fundamental beat note. Moreover, its absorption feature appears at the second harmonic of the RF modulation frequency generated by the joint modes via six interaction pathways without mutual phase shift. Such features persist even when the effects of the second-order sidebands of the incident fields are taken into account. Application potentials are emphasized.

  4. Electrothermal Frequency Modulated Resonator for Mechanical Memory

    KAUST Repository

    Hafiz, Md Abdullah Al

    2016-08-18

    In this paper, we experimentally demonstrate a mechanical memory device based on the nonlinear dynamics of an electrostatically actuated microelectromechanical resonator utilizing an electrothermal frequency modulation scheme. The microstructure is deliberately fabricated as an in-plane shallow arch to achieve geometric quadratic nonlinearity. We exploit this inherent nonlinearity of the arch and drive it at resonance with minimal actuation voltage into the nonlinear regime, thereby creating softening behavior, hysteresis, and coexistence of states. The hysteretic frequency band is controlled by the electrothermal actuation voltage. Binary values are assigned to the two allowed dynamical states on the hysteretic response curve of the arch resonator with respect to the electrothermal actuation voltage. Set-and-reset operations of the memory states are performed by applying controlled dc pulses provided through the electrothermal actuation scheme, while the read-out operation is performed simultaneously by measuring the motional current through a capacitive detection technique. This novel memory device has the advantages of operating at low voltages and under room temperature. [2016-0043

  5. Linear Frequency Modulated Signals VS Orthogonal Frequency Division Multiplexing Signals for Synthetic Aperture Radar Systems

    Science.gov (United States)

    2014-06-01

    FREQUENCY MODULATED SIGNALS VS ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING SIGNALS FOR SYNTHETIC APERTURE RADAR SYSTEMS by Sade A. Holder June...SIGNALS VS ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING SIGNALS FOR SYNTHETIC APERTURE RADAR SYSTEMS 5. FUNDING NUMBERS 6. AUTHOR(S) Sade A. Holder 7...OFDM) signal versus a linear frequency modulated or chirp signal on simulated synthetic aperture radar (SAR) imagery. Various parameters of the

  6. Fast Resonance Frequency Modulation in Superconducting Stripline Resonator

    OpenAIRE

    Segev, Eran; Abdo, Baleegh; Shtempluck, Oleg; Buks, Eyal

    2006-01-01

    Fast resonance frequency modulation of a superconducting stripline resonator is investigated. The experiments are performed using a novel device which integrates a hot electron detector (HED) into a superconducting stripline ring resonator. Frequency modulation is demonstrated by both applying dc current or voltage to the HED, and by applying optical illumination, with modulation frequencies of up to 4.2GHz. Potential applications for such a device are in telecommunication, quantum cryptograp...

  7. Frequency Modulation and Spatiotemporal Stability of the sCPG in Preterm Infants with RDS

    Directory of Open Access Journals (Sweden)

    Steven M. Barlow

    2012-01-01

    Full Text Available The nonnutritive suck (NNS is an observable and accessible motor behavior which is often used to make inference about brain development and pre-feeding skill in preterm and term infants. The purpose of this study was to model NNS burst compression pressure dynamics in the frequency and time domain among two groups of preterm infants, including those with respiratory distress syndrome (RDS, N=15 and 17 healthy controls. Digitized samples of NNS compression pressure waveforms recorded at a 1-week interval were collected 15 minutes prior to a scheduled feed. Regression analysis and ANOVA revealed that healthy preterm infants produced longer NNS bursts and the mean burst initiation cycle frequencies were higher when compared to the RDS group. Moreover, the initial 5 cycles of the NNS burst manifest a frequency modulated (FM segment which is a significant feature of the suck central pattern generator (sCPG, and differentially expressed in healthy and RDS infants. The NNS burst structure revealed significantly lower spatiotemporal index values for control versus RDS preterm infants during FM, and provides additional information on the microstructure of the sCPG which may be used to gauge the developmental status and progression of oromotor control systems among these fragile infants.

  8. Convergence of reference frequencies by multiple CF-FM bats (Rhinolophus ferrumequinum nippon) during paired flights evaluated with onboard microphones.

    Science.gov (United States)

    Furusawa, Yuto; Hiryu, Shizuko; Kobayasi, Kohta I; Riquimaroux, Hiroshi

    2012-09-01

    The constant frequency component of the second harmonic (CF(2)) of echolocation sounds in Rhinolophus ferrumequinum nippon were measured using onboard telemetry microphones while the bats exhibited Doppler-shift compensation during flights with conspecifics. (1) The CF(2) frequency of pulses emitted by individual bats at rest (F (rest)) showed a long-term gradual decline by 0.22 kHz on average over a period of 3 months. The mean neighboring F (rest) (interindividual differences in F (rest) between neighboring bats when the bats were arranged in ascending order according to F (rest)) ranged from 0.08 to 0.11 kHz among 18 bats in a laboratory colony. (2) The standard deviation of observed echo CF(2) (reference frequency) for bats during paired flights ranged from 50 to 90 Hz, which was not significantly different from that during single flights. This finding suggests that during paired flights, bats exhibit Doppler-shift compensation with the same accuracy as when they fly alone. (3) In 60% (n = 29) of the cases, the difference in the reference frequency between two bats during paired flights significantly decreased compared to when the bats flew alone. However, only 15% of the cases (n = 7) showed a significant increase during paired flights. The difference in frequency between two bats did not increase even when the reference frequencies of the individuals were not statistically different during single flights.

  9. Research on Internal Connection Between Frequency Modulation and Phase Modulation in the Nonlinear Modulation%非线性调制中调频和调相内在联系的研究

    Institute of Scientific and Technical Information of China (English)

    陈皓; 桂伟

    2014-01-01

    从定义和角频率两个角度分析调相,同时从定义和相角两个角度分析调频。进而用数学公式对直接调相和利用调频间接调相、直接调频和利用调相间接调频进行比较,再定量的对调频和调相信号进行比较,从而阐述了调频与调相之间内在的联系。%The paper analyses phase modulation from two angles of definition and angular frequency,and analyses frequency modulation from two angles of definition and phase angle. And then uses a mathematical formula for the comparation between direct phase modulation and indirect phase modulation by frequency,for the comparation between direct frequency modulation and indirect frequency modulation by phase,and then the quantitative comparison of frequency modulation and phase modulation. Then elaborates the nternal connection between FM and PM.

  10. Atoms in the counter-propagating frequency-modulated waves: splitting, cooling, confinement

    Science.gov (United States)

    Romanenko, Victor I.; Kornilovska, Nataliya V.

    2017-09-01

    We show that the counter-propagating frequency-modulated (FM) waves of the same intensity can split an orthogonal atomic beam into two beams. We calculate the temperature of the atomic ensemble for the case when the atoms are grouped around zero velocity in the direction of the waves propagation. The high-intensity laser radiation with a properly chosen carrier frequency can form a one-dimensional trap for atoms. We carry out the numerical simulation of the atomic motion (two-level model of the atom-field interaction) using parameters appropriate for sodium atoms and show that sub-Doppler cooling can be reached. We suppose that such a cooling is partly based on the cooling without spontaneous emission in polychromatic waves [H. Metcalf, Phys. Rev. A 77, 061401 (2008)]. We calculate the state of the atom in the field by the Monte Carlo wave-function method and describe its mechanical motion by the classical mechanics.

  11. Neuromagnetic responses to frequency modulation of a continuous tone.

    Science.gov (United States)

    Hari, R; Mäkelä, J P

    1986-01-01

    Neuromagnetic responses to frequency modulation of a continuous tone were studied in nine subjects. The latencies of the transient responses increased and the amplitudes decreased with decreasing speed of modulation. The equivalent dipoles for modulation of a 1,000 Hz tone were slightly but statistically significantly anterior to the dipoles activated by modulation of a 500 Hz tone. The generation mechanisms of N100m are discussed.

  12. Analysis of Pulse Modulated Control Systems (Ⅲ) Stability of Systems with Pulse Frequency Modulation and Systems with Combined Pulse Frequency and Pulse Width Modulation

    OpenAIRE

    OI,Shigemitsu

    1993-01-01

    Sufficient conditions for finite pulse stability of interconnected systems with combined pulse frequency and pulse width modulation are developed in this paper using a direct method. The stability criteria established provide upper bounds on the number of pulses emitted by each modulator. The results are also applicable to those systems which contain a finite number of pulse frequency modulators and a finite number of combined pulse frequency and pulse width modulators

  13. Effects of sound-field frequency modulation amplification on reducing teachers' sound pressure level in the classroom.

    Science.gov (United States)

    Sapienza, C M; Crandell, C C; Curtis, B

    1999-09-01

    Voice problems are a frequent difficulty that teachers experience. Common complaints by teachers include vocal fatigue and hoarseness. One possible explanation for these symptoms is prolonged elevations in vocal loudness within the classroom. This investigation examined the effectiveness of sound-field frequency modulation (FM) amplification on reducing the sound pressure level (SPL) of the teacher's voice during classroom instruction. Specifically, SPL was examined during speech produced in a classroom lecture by 10 teachers with and without the use of sound-field amplification. Results indicated a significant 2.42-dB decrease in SPL with the use of sound-field FM amplification. These data support the use of sound-field amplification in the vocal hygiene regimen recommended to teachers by speech-language pathologists.

  14. Analysis of FM demodulator output noise with applications to FM telemetry

    Directory of Open Access Journals (Sweden)

    Rajendra Kumar

    2006-07-01

    Full Text Available We present an analysis for evaluating the probability density function (pdf of the noise at the output of the frequency demodulator. It is shown that the noise is non-Gaussian and that for low to medium signal-to-noise power ratios, its pdf differs very significantly from the Gaussian pdf commonly assumed in simplified analysis. These results are very important for analyzing the performance of the PCM/FM type of modulation schemes used in telemetry systems as illustrated in the paper.

  15. Effects of noise reduction on AM and FM perception.

    Science.gov (United States)

    Ives, D Timothy; Calcus, Axelle; Kalluri, Sridhar; Strelcyk, Olaf; Sheft, Stanley; Lorenzi, Christian

    2013-02-01

    The goal of noise reduction (NR) algorithms in digital hearing aid devices is to reduce background noise whilst preserving as much of the original signal as possible. These algorithms may increase the signal-to-noise ratio (SNR) in an ideal case, but they generally fail to improve speech intelligibility. However, due to the complex nature of speech, it is difficult to disentangle the numerous low- and high-level effects of NR that may underlie the lack of speech perception benefits. The goal of this study was to better understand why NR algorithms do not improve speech intelligibility by investigating the effects of NR on the ability to discriminate two basic acoustic features, namely amplitude modulation (AM) and frequency modulation (FM) cues, known to be crucial for speech identification in quiet and in noise. Here, discrimination of complex, non-linguistic AM and FM patterns was measured for normal hearing listeners using a same/different task. The stimuli were generated by modulating 1-kHz pure tones by either a two-component AM or FM modulator with patterns changed by manipulating component phases. Modulation rates were centered on 3 Hz. Discrimination of AM and FM patterns was measured in quiet and in the presence of a white noise that had been passed through a gammatone filter centered on 1 kHz. The noise was presented at SNRs ranging from -6 to +12 dB. Stimuli were left as such or processed via an NR algorithm based on the spectral subtraction method. NR was found to yield small but systematic improvements in discrimination for the AM conditions at favorable SNRs but had little effect, if any, on FM discrimination. A computational model of early auditory processing was developed to quantify the fidelity of AM and FM transmission. The model captured the improvement in discrimination performance for AM stimuli at high SNRs with NR. However, the model also predicted a relatively small detrimental effect of NR for FM stimuli in contrast with the average

  16. Direct Load Control by AC Frequency Modulation

    DEFF Research Database (Denmark)

    Douglass, Philip James; You, Shi

    2012-01-01

    Fine-grained under frequency load shedding called “demand as a frequency controlled reserve“ (DFCR) has been shown to be a promising method of providingfrequency regulation service from distributed loads [1]. Micro-grids with a large portion of intermittent renewable generation will benefit great...

  17. Broadcast Communication by System Frequency Modulation

    DEFF Research Database (Denmark)

    Douglass, Philip James; You, Shi; Heussen, Kai

    2012-01-01

    off-nominal system frequency values is a novel narrowband broadcast communications channel between system operators and frequency sensitive distributed energy resources (FS-DER). The feasibility of the proposed system is evaluated on an existing island power system in Denmark. This study shows...

  18. Designing Non-linear Frequency Modulated Signals For Medical Ultrasound Imaging

    DEFF Research Database (Denmark)

    Gran, Fredrik; Jensen, Jørgen Arendt

    2006-01-01

    is tested experimentally using the RASMUS ultrasound system with a 7 MHz linear array transducer. Synthetic transmit aperture ultrasound imaging is applied to acquire data. The proposed design method was compared to a linear FM signal. Due to more efficient spectral usage, a gain in SNR of 4.3plusmn1.2 d......In this paper a new method for designing non-linear frequency modulated (NLFM) waveforms for ultrasound imaging is proposed. The objective is to control the amplitude spectrum of the designed waveform and still keep a constant transmit amplitude, so that the transmitted energy is maximized...... in the transducer can be decreased. Secondly, by choosing an appropriate amplitude spectrum, no additional temporal tapering has to be applied to the matched filter to achieve sufficient range sidelobe suppression. Proper design results in waveforms with a range sidelobe level beyond -80 dB. The design method...

  19. Radio frequency powering of microelectronic sensor modules

    Energy Technology Data Exchange (ETDEWEB)

    Boegel, Gerd vom; Meyer, Frederic; Kemmerling, Martin [Fraunhofer-Institut fuer Mikroelektronische Schaltungen und Systeme, Duisburg (Germany)

    2013-03-01

    In RFID applications the power supply of transponders via electromagnetic field is state-of-the-art. In this presentation the use of electromagnetic energy will be discussed for the operation of sensor modules. Starting with the question, whether the omnipresent radiation from power supply networks, radio transmitters, and mobile phone base stations is useable (energy harvesting), the feasibility of the operation of self-sufficient sensor modules is explained. Ancillary conditions of typical applications (e.g. operating range) and technology are considered. (orig.)

  20. Generation of the Optical Frequency Comb with a Bandwidth of 3.8 nm by Using an Electro-absorption Modulator and a Frequency Modulator%利用EAM和FM产生带宽3.8 nm的光梳

    Institute of Scientific and Technical Information of China (English)

    高迪; 邵茜; 陈静远; 李培丽

    2015-01-01

    Using the cascade structure of an Electro-absorption Modulator (EAM) and a frequency modulator (FM), we proposed a new Optical Frequency Comb (OFC) generation scheme. The program structure is simple, easy to be controlled and the output noise is low. We conducted a theoretical analysis on the principle scheme and did research on the simulation with software of Optisystem7.0. The simulation results show that: we generated a flat optical frequency comb, whose center wavelength and line spacing can be tuned independently. Also,the effective bandwidth of the OFC is 3.8 nm, its line spacing is 5 GHz and number of lines is 105.%利用电吸收调制器(Electro-absorption Modulator, EAM)和频率调制器(Frequency Modulator, FM)的级联结构,提出了一种新型光学频率梳(Optical Frequency Comb, OFC)产生方案。本方案结构简单、易于控制,输出噪声低。对提出的方案原理进行了理论分析,并利用Optisystem7.0软件进行仿真研究。仿真结果表明:产生了平坦的光学频率梳,其中心波长和谱线间距均可独立调谐。产生的OFC有效带宽为3.8 nm,得到了谱线间距为5 GHz的105条谱线。

  1. Frequency specific modulation of human somatosensory cortex

    Directory of Open Access Journals (Sweden)

    Matteo eFeurra

    2011-02-01

    Full Text Available Oscillatory neuronal activities are commonly observed in response to sensory stimulation. However, their functional roles are still the subject of debate. One way to probe the roles of oscillatory neural activities is to deliver alternating current to the cortex at biologically relevant frequencies and examine whether such stimulation influences perception and cognition. In this study, we tested whether transcranial alternating current stimulation (tACS over the primary somatosensory cortex (SI could elicit tactile sensations in humans in a frequency dependent manner. We tested the effectiveness of tACS over SI at frequency bands ranging from 2 to 70 Hz. Our results show that stimulation in alpha (10-14 Hz and high gamma (52-70 Hz frequency range produces a tactile sensation in the contralateral hand. A weaker effect was also observed for beta (16-20 Hz stimulation. These findings highlight the frequency-dependency of effective tACS over SI with the effective frequencies corresponding to those observed in previous EEG/MEG studies of tactile perception. Our present study suggests that tACS could be used as a powerful online stimulation technique to reveal the causal roles of oscillatory brain activities.

  2. Frequency modulation reveals the phasing of orbital eccentricity during Cretaceous Oceanic Anoxic Event II and the Eocene hyperthermals

    Science.gov (United States)

    Laurin, Jiří; Meyers, Stephen R.; Galeotti, Simone; Lanci, Luca

    2016-05-01

    Major advances in our understanding of paleoclimate change derive from a precise reconstruction of the periods, amplitudes and phases of the 'Milankovitch cycles' of precession, obliquity and eccentricity. While numerous quantitative approaches exist for the identification of these astronomical cycles in stratigraphic data, limitations in radioisotopic dating, and instability of the theoretical astronomical solutions beyond ∼50 Myr ago, can challenge identification of the phase relationships needed to constrain climate response and anchor floating astrochronologies. Here we demonstrate that interference patterns accompanying frequency modulation (FM) of short eccentricity provide a robust basis for identifying the phase of long eccentricity forcing in stratigraphic data. One- and two-dimensional models of sedimentary distortion of the astronomical signal are used to evaluate the veracity of the FM method, and indicate that pristine eccentricity FM can be readily distinguished in paleo-records. Apart from paleoclimatic implications, the FM approach provides a quantitative technique for testing and calibrating theoretical astronomical solutions, and for refining chronologies for the deep past. We present two case studies that use the FM approach to evaluate major carbon-cycle perturbations of the Eocene and Late Cretaceous. Interference patterns in the short-eccentricity band reveal that Eocene hyperthermals ETM2 ('Elmo'), H2, I1 and ETM3 (X; ∼52-54 Myr ago) were associated with maxima in the 405-kyr cycle of orbital eccentricity. The same eccentricity configuration favored regional anoxic episodes in the Mediterranean during the Middle and Late Cenomanian (∼94.5-97 Myr ago). The initial phase of the global Oceanic Anoxic Event II (OAE II; ∼93.9-94.5 Myr ago) coincides with maximum and falling 405-kyr eccentricity, and the recovery phase occurs during minimum and rising 405-kyr eccentricity. On a Myr scale, the event overlaps with a node in eccentricity

  3. Abatement of PAPR for ACO-OFDM deployed in VLC systems by frequency modulation of the baseband signal forming a constant envelope

    Science.gov (United States)

    Kumar Singh, Vinay; Dalal, U. D.

    2017-06-01

    To inhibit the effect of non-linearity of the LEDs leading to a significant increase in the peak to average power ratio (PAPR) of the OFDM signals in the Visible light communication (VLC) we propose a frequency modulated constant envelope OFDM (FM CE-OFDM) technique. The abrupt amplitude variations in the OFDM signal are frequency modulated before being applied to the LED for electro-optical conversion resulting in a constant envelope signal. The LED is maintained in the linear region of operation by this constant envelope signal at sufficient DC bias. The proposed technique reduces the PAPR to the least possible value ≈0 dB. We theoretically analyze and perform numerical simulations to assess the enhancement of the proposed system. The optimal modulation index is found to be 0.3. The metrics pertaining to the evaluation of the phase discontinuity is derived and is found to be lesser for the FM CE-OFDM as compared to the phase modulated (PM) CE-OFDM. The receiver sensitivity is improved by 1.6 dB for a transmission distance of 2 m for the FM CE-OFDM as compared to the PM CE-OFDM at the FEC threshold. We compare the BER performance of the ideal OFDM (without the non linearity of LED), power back-off OFDM, PM CE-OFDM and FM CE-OFDM in an optical wireless channel (OWC) scenario. The FM CE-OFDM has an improvement of 2.1 dB SNR at the FEC threshold as compared to the PM CE-OFDM. It also shows an improvement of 11 dB when compared with the power back-off technique used in the VLC systems for 10 dB power back-off.

  4. Principles and Limitations of Ultra-Wideband FM Communications Systems

    Directory of Open Access Journals (Sweden)

    Kouwenhoven Michiel HL

    2005-01-01

    Full Text Available This paper presents a novel UWB communications system using double FM: a low-modulation index digital FSK followed by a high-modulation index analog FM to create a constant-envelope UWB signal. FDMA techniques at the subcarrier level are exploited to accommodate multiple users. The system is intended for low (1–10 kbps and medium (100–1000 kbps bit rate, and short-range WPAN systems. A wideband delay-line FM demodulator that is not preceded by any limiting amplifier constitutes the key component of the UWBFM receiver. This unusual approach permits multiple users to share the same RF bandwidth. Multipath, however, may limit the useful subcarrier bandwidth to one octave. This paper addresses the performance with AWGN and multipath, the resistance to narrowband interference, as well as the simultaneous detection of multiple FM signals at the same carrier frequency. SPICE and Matlab simulation results illustrate the principles and limitations of this new technology. A hardware demonstrator has been realized and has allowed the confirmation of theory with practical results.

  5. Method and apparatus for resonant frequency waveform modulation

    Science.gov (United States)

    Taubman, Matthew S [Richland, WA

    2011-06-07

    A resonant modulator device and process are described that provide enhanced resonant frequency waveforms to electrical devices including, e.g., laser devices. Faster, larger, and more complex modulation waveforms are obtained than can be obtained by use of conventional current controllers alone.

  6. Perception of a Sung Vowel as a Function of Frequency-Modulation Rate and Excursionin Normal-Hearing and Hearing-Impaired Listeners

    DEFF Research Database (Denmark)

    Vatti, Marianna; Santurette, Sébastien; Pontoppidan, Niels henrik

    2014-01-01

    affects the perception of a sung vowel based on FM cues. Method: Vibrato maps were obtained in 14 NH and 12 HI listeners with different degrees of musical experience. The FM rate and FM excursion of a synthesized vowel, to which coherent FM was applied, were adjusted until a singing voice emerged. Results......: In NH listeners, adding FM to the steady vowel components produced perception of a singing voice for FM rates between 4.1 and 7.5 Hz and FM excursions between 17 and 83 cents on average. In contrast, HI listeners showed substantially broader vibrato maps. Individual differences in map boundaries were......, overall, not correlated with audibility or frequency selectivity at the vowel fundamental frequency, with no clear effect of musical experience. Conclusion: Overall, it was shown that hearing loss affects the perception of a sung vowel based on FM-rate and FM-excursion cues, possibly due to deficits in FM...

  7. Excitation of spin echo by pulses with linear frequency modulation

    Science.gov (United States)

    Baruzdin, S. A.

    2015-03-01

    The excitation of a spin echo by two pulses with linear frequency modulation, upon which the pulse parameters ensure maximal compression of the response in time, is considered. The frequency of the excitation pulses was changed by a step law, approximating its linear rise. The transfer matrix of the state of the spin system for pulses with linear frequency modulation is found by solving the Bloch equations. The shape of the envelope of the spin echo in thin magnetic cobalt films, as well as the dependence of the echo amplitude on the parameters of the excitation pulses, is determined. The amplitudes of the excitation pulses, which ensure the excitation of the echo maximal amplitude for various values of the frequency deviation, are found. It is shown that the use of pulses with linear frequency modulation makes it possible to obtain the same echo amplitude as with the use of simple excitation pulses for a substantially smaller amplitude and power of excitation pulses.

  8. A CMOS frequency generation module for 60-GHz applications

    Institute of Scientific and Technical Information of China (English)

    Zhou Chunyuan; Zhang Lei; Wang Hongrui; Qian He

    2012-01-01

    A frequency generation module for 60-GHz transceivers and phased array systems is presented in this paper.It is composed of a divide-by-2 current mode logic divider (CM L) and a doubler in push-push configuration.Benefiting from the CML structure and push-push configuration,the proposed frequency generation module has a wide operating frequency range to cover process,voltage,and temperature variation.It is implemented in a 90-nm CMOS process,and occupies a chip area of 0.64 × 0.65 mm2 including pads.The measurement results show that the designed frequency generation module functions properly with input frequency over 15 GHz to 25 GHz.The whole chip dissipates 12.1 mW from a 1.2-V supply excluding the output buffers.

  9. Components of cross-frequency modulation in health and disease

    Directory of Open Access Journals (Sweden)

    Elena A Allen

    2011-07-01

    Full Text Available The cognitive deficits associated with schizophrenia are commonly believed to arise from the abnormal temporal integration of information, however a quantitative approach to assess network coordination is lacking. Here, we propose to use cross-frequency modulation, the dependence of local high-frequency activity on the phase of widespread low-frequency oscillations, as an indicator of network coordination and functional integration. In an exploratory analysis based on pre-existing data, we measured cross-frequency modulation from multi-channel EEG recordings acquired while schizophrenia patients (n = 47 and healthy controls (n = 130 performed an auditory oddball task. Novel application of independent component analysis (ICA to modulation data delineated components with specific spatial and spectral profiles, the weights of which showed co-variation with diagnosis. Global cross-frequency modulation was significantly greater in healthy controls (F1,175=9.25, P<0.005, while modulation at fronto-temporal electrodes was greater in patients (F1,175 =17.5, P<0.0001. We further found that the weights of schizophrenia-relevant components were associated with genetic polymorphisms at previously identified risk loci. Global cross-frequency modulation decreased with copies of 957C allele in the gene for the dopamine D2 receptor (r = −0.20, P < 0.01 across all subjects. Additionally, greater ‘aberrant’ fronto-temporal modulation in schizophrenia patients was correlated with several polymorphisms in the gene for the α2-subunit of the GABAA receptor (GABRA2 as well as the total number of risk alleles in GABRA2 (r = 0.45, P < 0.01. Overall, our results indicate great promise for this approach in establishing patterns of cross-frequency modulation in health and disease and elucidating the roles of oscillatory interactions in functional connectivity.

  10. Second-order temporal modulation transfer functions.

    Science.gov (United States)

    Lorenzi, C; Soares, C; Vonner, T

    2001-08-01

    Detection thresholds were measured for a sinusoidal modulation applied to the modulation depth of a sinusoidally amplitude-modulated (SAM) white noise carrier as a function of the frequency of the modulation applied to the modulation depth (referred to as f'm). The SAM noise acted therefore as a "carrier" stimulus of frequency fm, and sinusoidal modulation of the SAM-noise modulation depth generated two additional components in the modulation spectrum: fm-f'm and fm+f'm. The tracking variable was the modulation depth of the sinusoidal variation applied to the "carrier" modulation depth. The resulting "second-order" temporal modulation transfer functions (TMTFs) measured on four listeners for "carrier" modulation frequencies fm of 16, 64, and 256 Hz display a low-pass segment followed by a plateau. This indicates that sensitivity to fluctuations in the strength of amplitude modulation is best for fluctuation rates f'm below about 2-4 Hz when using broadband noise carriers. Measurements of masked modulation detection thresholds for the lower and upper modulation sideband suggest that this capacity is possibly related to the detection of a beat in the sound's temporal envelope. The results appear qualitatively consistent with the predictions of an envelope detector model consisting of a low-pass filtering stage followed by a decision stage. Unlike listeners' performance, a modulation filterbank model using Q values > or = 2 should predict that second-order modulation detection thresholds should decrease at high values of f'm due to the spectral resolution of the modulation sidebands (in the modulation domain). This suggests that, if such modulation filters do exist, their selectivity is poor. In the latter case, the Q value of modulation filters would have to be less than 2. This estimate of modulation filter selectivity is consistent with the results of a previous study using a modulation-masking paradigm [S. D. Ewert and T. Dau, J. Acoust. Soc. Am. 108, 1181

  11. Carrier suppression in quadruple frequency modulation by cascaded optical external modulators for millimeter-wave generation

    Institute of Scientific and Technical Information of China (English)

    Xue Feng; Wei Zhang; Xiaoming Liu

    2009-01-01

    The optical carrier suppression in optical quadruple frequency modulation by cascaded external modulators is investigated theoretically and experimentally. Theoretical analysis demonstrates that the optical carrier suppression ratio is related with not only the initial phase difference of electrical signals applied on the two modulators, but also the optical phase shift between the two modulators. The maximum suppression ratio can be achieved when the total phase difference is equal to nπ+π/2(n=1,2…),which is verified by experiments. By properly controlling the total phase shift, 40-GHz millimeter-wave is generated by using a 10-GHz radio frequency (RF) source and the modulators.

  12. Optical-fiber-connected 300-GHz FM-CW radar system

    Science.gov (United States)

    Kanno, Atsushi; Sekine, Norihiko; Kasamatsu, Akifumi; Yamamoto, Naokatsu; Kawanishi, Tetsuya

    2017-05-01

    300-GHz frequency-modulated continuous-wave (FM-CW) radar system operated by radio over fiber technologies is configured and demonstrated. Centralized signal generator, which is based on an optical frequency comb generation, provides high-precise FM-CW radar signal. The optical signal is easy to be transported to radar heads through an optical fiber network. Optical-modulator-based optical frequency comb generator is utilized as an optical frequency multiplier from a microwave signal to a 300-GHz terahertz signal by an optical modulation technique. In the study, we discuss the configuration of the network, signal generator and remote radar head for terahertz-wave multi-static radar system.

  13. Optimizing Frequency-Modulated CW EDMR in silicon

    Science.gov (United States)

    Zhu, Lihuang; van Schooten, Kipp; Ramanathan, Chandrasekhar

    Electrically detected magnetic resonance (EDMR) is a powerful method of probing dopant and defect spin states in semiconductor devices. Moreover, at the single dopant level, these spin states are heavily investigated as potential qubit systems, though facile electronic access to single dopants is exceedingly difficult. We therefore characterize detection sensitivities of frequency-modulated CW-EDMR of phosphorus donors in silicon Si:P using a home-built 2.5 GHz system (~80 mT) at 5 K. An arbitrary waveform generator controls the frequency modulation, allowing us to optimize the signal to noise ratio (SNR) of both the dangling bond and phosphorus donor signals against multiple experimental parameters, such as modulation amplitude and modulation frequency. The optimal range of frequency modulation parameters is constrained by the relaxation time of the phosphorous electron at 5 K, resulting in the same sensitivity limit as field modulated CW-EDMR, but offers some technical advantages; e.g. reducing the relative contribution of magnetic field induced currents and eliminating the need for field modulation coils. We further characterize the EDMR SNR in Si:P as a function of optical excitation energy by using a narrow line laser, tunable across donor exciton and band gap states.

  14. Laser frequency stabilization and shifting by using modulation transfer spectroscopy

    Science.gov (United States)

    Cheng, Bing; Wang, Zhao-Ying; Wu, Bin; Xu, Ao-Peng; Wang, Qi-Yu; Xu, Yun-Fei; Lin, Qiang

    2014-10-01

    The stabilizing and shifting of laser frequency are very important for the interaction between the laser and atoms. The modulation transfer spectroscopy for the 87Rb atom with D2 line transition F = 2 → F' = 3 is used for stabilizing and shifting the frequency of the external cavity grating feedback diode laser. The resonant phase modulator with electro—optical effect is used to generate frequency sideband to lock the laser frequency. In the locking scheme, circularly polarized pump- and probe-beams are used. By optimizing the temperature of the vapor, the pump- and probe-beam intensity, the laser linewidth of 280 kHz is obtained. Furthermore, the magnetic field generated by a solenoid is added into the system. Therefore the system can achieve the frequency locking at any point in a range of hundreds of megahertz frequency shifting with very low power loss.

  15. Behavioral Correlates of 50-kHz Ultrasonic Vocalizations in Rats: Progressive Operant Discrimination Learning Reduces Frequency Modulation and Increases Overall Amplitude

    Directory of Open Access Journals (Sweden)

    Shoko Yuki

    2014-11-01

    Full Text Available Ultrasonic vocalizations (USVs in rats are thought to contain ecological signals reflecting emotional states. These USVs are centered on 50-kHz, and frequency modulation (FM is hypothesized to indicate positive emotion; however, results from recent studies are inconsistent with this hypothesis. We suspected that such inconsistencies might result from ambiguity in defining frequency modulation, and problems with acoustic analyses and behavioral protocols. We addressed these problems by applying quantitative methods for USV analyses and using a food reward operant paradigm. Our results revealed that frequency modulation varied according to the degree of positive outcomes, but the direction of change was opposite to what had been observed in previous studies. The FM in 50-kHz USVs decreased as animals learned the task and obtained more reinforcement, while USV amplitude increased as learning progressed. To reconcile these results with those from prior studies, we suggest that FM in 50-kHz USVs should be taken as an index of reward prediction errors, and USV amplitude should be considered as an index of positive emotion.

  16. Digital intermediate frequency QAM modulator using parallel processing

    Science.gov (United States)

    Pao, Hsueh-Yuan; Tran, Binh-Nien

    2008-05-27

    The digital Intermediate Frequency (IF) modulator applies to various modulation types and offers a simple and low cost method to implement a high-speed digital IF modulator using field programmable gate arrays (FPGAs). The architecture eliminates multipliers and sequential processing by storing the pre-computed modulated cosine and sine carriers in ROM look-up-tables (LUTs). The high-speed input data stream is parallel processed using the corresponding LUTs, which reduces the main processing speed, allowing the use of low cost FPGAs.

  17. Frequency Response of Modulated Electroluminescence of Light-Emitting Diodes

    Institute of Scientific and Technical Information of China (English)

    FENG Lie-Feng; LI Yang; LI Ding; WANG Cun-Da; ZHANG Guo-Yi; YAO Dong-Sheng; LIU Wei-Fang; XING Peng-Fei

    2011-01-01

    Frequency responses of modulated electroluminescence (EL) of light-emitting diodes were measured using a testing setup.With increasing frequency of the ac signal,the relative light intensity (RLI) clearly decreases.Furthermore,a peculiar asynchrony between the RLI and ac small-signal is observed.At frequencies higher than 10kHz,the RLI clearly lags behind the ac signal and the absolute value of the lagging angle is nearly proportional to the signal frequency.Using the classical recombination model of light-emitting diodes under ac small-signal modulation,these abnormal characteristics of modulated EL can be clearly explained.High-power light-emitting diodes (LEDs) have received great attention recently owing to their applications in energy-saving lights,display items and many other fields;therefore,the optical and electrical characteristics of LEDs at forward bias hold significant potential for research.[1-4] However,for a new kind of light emission device,the general research on its performance focuses on the light emission and dc currentvoltage (I-V) characteristics.%Frequency responses of modulated electroluminescence (EL) of light-emitting diodes were measured using a testing setup. With increasing frequency of the ac signal, the relative light intensity (RLI) clearly decreases. Furthermore, a peculiar asynchrony between the RLI and ac small-signal is observed. At frequencies higher than 10kHz, the RLI clearly lags behind the ac signal and the absolute value of the lagging angle is nearly proportional to the signal frequency. Using the classical recombination model of light-emitting diodes under ac small-signal modulation, these abnormal characteristics of modulated EL can be clearly explained.

  18. Sistema de frequência modulada em crianças com deficiência auditiva: avaliação de resultados Frequency modulation systems in hearing impaired children: outcome evaluation

    Directory of Open Access Journals (Sweden)

    Regina Tangerino de Souza Jacob

    2012-12-01

    Full Text Available OBJETIVO: Avaliar a percepção da fala de crianças deficientes auditivas com o aparelho de amplificação sonora individual (AASI e sistema de frequência modulada (FM em situações de ruído em campo livre e em sala de aula. MÉTODOS: Participaram 13 crianças deficientes auditivas entre 7 e 17 anos. Foi aplicado o Hearing in Noise Test (HINT com AASI e com o FM. Também foi aplicado o questionário Avaliação do Sistema FM, respondido pelos professores das crianças, com o intuito de avaliar, individualmente, o desempenho da criança em diferentes situações auditivas somente com AASI e com o AASI e o sistema FM. RESULTADOS: Houve diferença para todas as situações com e sem FM no teste HINT. O mesmo aconteceu com os resultados do questionário, sendo que sem FM a pontuação foi sempre menor do que com FM, independentemente da condição. CONCLUSÃO: O uso de medidas subjetivas, como o questionário, é fundamental para determinar a eficácia da indicação dos dispositivos auxiliares para o deficiente auditivo. A efetividade do sistema FM pode ser observada pela "vantagem FM", que é a diferença média mínima de 10 dB encontrada nas avaliações de percepção da fala com e sem FM nas diferentes situações de ruído. Os benefícios encontrados na presente pesquisa com o uso do sistema FM na melhora da percepção da fala podem ser extrapolados não só para a sala de aula e para a legislação da educação inclusiva, mas também para atividades sociais e de lazer.PURPOSE: To assess speech perception of hearing impaired children with hearing aids (HA and frequency modulated system (FM in situations of noise in free field and in the classroom. METHODS: Subjects were 13 hearing impaired children between 7 and 17 years. It used the Hearing in Noise Test (HINT with hearing aids and FM. Questionnaire Evaluation System FM was also applied responded by teachers of children in order to assess individually the child's performance in

  19. Gearbox Vibration Signal Amplitude and Frequency Modulation

    Directory of Open Access Journals (Sweden)

    Fakher Chaari

    2012-01-01

    Full Text Available Gearboxes usually run under fluctuating load conditions during service, however most of papers available in the literature describe models of gearboxes under stationary load conditions. Main task of published papers is fault modeling for their detection. Considering real situation from industry, the assumption of stationarity of load conditions cannot be longer kept. Vibration signals issued from monitoring in maintenance operations differ from mentioned models (due to load non-stationarity and may be difficult to analyze which lead to erroneous diagnosis of the system. The objective of this paper is to study the influence of time varying load conditions on a gearbox dynamic behavior. To investigate this, a simple spur gear system without defects is modeled. It is subjected to a time varying load. The speed-torque characteristic of the driving motor is considered. The load variation induces speed variation, which causes a variation in the gearmesh stiffness period. Computer simulation shows deep amplitude modulations with sidebands that don't differ from those obtained when there is a defective tooth. In order to put in evidence the time varying load effects, Short Time Fourier Transform and then Smoothed Wigner-Ville distribution are used. Results show that the last one is well suited for the studied case.

  20. The stray capacitance effect in Kelvin probe force microscopy using FM, AM and heterodyne AM modes.

    Science.gov (United States)

    Ma, Zong Min; Kou, Lili; Naitoh, Yoshitaka; Li, Yan Jun; Sugawara, Yasuhiro

    2013-06-07

    The effect of stray capacitance on potential measurements was investigated using Kelvin probe force microscopy (KPFM) at room temperature under ultra-high vacuum (UHV). The stray capacitance effect was explored in three modes, including frequency modulation (FM), amplitude modulation (AM) and heterodyne amplitude modulation (heterodyne AM). We showed theoretically that the distance-dependence of the modulated electrostatic force in AM-KPFM is significantly weaker than in FM- and heterodyne AM-KPFMs and that the stray capacitance of the cantilever, which seriously influences the potential measurements in AM-KPFM, was almost completely eliminated in FM- and heterodyne AM-KPFMs. We experimentally confirmed that the contact potential difference (CPD) in AM-KPFM, which compensates the electrostatic force between the tip and the surface, was significantly larger than in FM- and heterodyne AM-KPFMs due to the stray capacitance effect. We also compared the atomic scale corrugations in the local contact potential difference (LCPD) among the three modes on the surface of Si(111)-7 × 7 finding that the LCPD corrugation in AM-KPFM was significantly weaker than in FM- and heterodyne AM-KPFMs under low AC bias voltage conditions. The very weak LCPD corrugation in AM-KPFM was attributed to the artefact induced by topographic feedback.

  1. A mechanism for frequency modulation in songbirds shared with humans.

    Science.gov (United States)

    Amador, Ana; Margoliash, Daniel

    2013-07-03

    In most animals that vocalize, control of fundamental frequency is a key element for effective communication. In humans, subglottal pressure controls vocal intensity but also influences fundamental frequency during phonation. Given the underlying similarities in the biomechanical mechanisms of vocalization in humans and songbirds, songbirds offer an attractive opportunity to study frequency modulation by pressure. Here, we present a novel technique for dynamic control of subsyringeal pressure in zebra finches. By regulating the opening of a custom-built fast valve connected to the air sac system, we achieved partial or total silencing of specific syllables, and could modify syllabic acoustics through more complex manipulations of air sac pressure. We also observed that more nuanced pressure variations over a limited interval during production of a syllable concomitantly affected the frequency of that syllable segment. These results can be explained in terms of a mathematical model for phonation that incorporates a nonlinear description for the vocal source capable of generating the observed frequency modulations induced by pressure variations. We conclude that the observed interaction between pressure and frequency was a feature of the source, not a result of feedback control. Our results indicate that, beyond regulating phonation or its absence, regulation of pressure is important for control of fundamental frequencies of vocalizations. Thus, although there are separate brainstem pathways for syringeal and respiratory control of song production, both can affect airflow and frequency. We hypothesize that the control of pressure and frequency is combined holistically at higher levels of the vocalization pathways.

  2. Optimal frequency conversion in the nonlinear stage of modulation instability

    CERN Document Server

    Bendahmane, A; Kudlinski, A; Szriftgiser, P; Conforti, M; Wabnitz, S; Trillo, S

    2015-01-01

    We investigate multi-wave mixing associated with the strongly pump depleted regime of induced modulation instability (MI) in optical fibers. For a complete transfer of pump power into the sideband modes, we theoretically and experimentally demonstrate that it is necessary to use a much lower seeding modulation frequency than the peak MI gain value. Our analysis shows that a record 95 % of the input pump power is frequency converted into the comb of sidebands, in good quantitative agreement with analytical predictions based on the simplest exact breather solution of the nonlinear Schr\\"odinger equation.

  3. Modulation of the Object/Background Interaction by Spatial Frequency

    Directory of Open Access Journals (Sweden)

    Yanju Ren

    2011-05-01

    Full Text Available With regard to the relationship between object and background perception in the natural scene images, functional isolation hypothesis and interactive hypothesis were proposed. Based on previous studies, the present study investigated the role of spatial frequency in the relationship between object and background perception in the natural scene images. In three experiments, participants reported the object, background, or both after seeing each picture for 500 ms followed by a mask. The authors found that (a backgrounds were identified more accurately when they contained a consistent rather than an inconsistent object, independently of spatial frequency; (b objects were identified more accurately in a consistent than an inconsistent background under the condition of low spatial frequencies but not high spatial frequencies; (c spatial frequency modulation remained when both objects and backgrounds were reported simultaneously. The authors conclude that object/background interaction is partially dependent on spatial frequency.

  4. Type 1,1-operators defined by vanishing frequency modulation

    DEFF Research Database (Denmark)

    Johnsen, Jon

    2009-01-01

    This paper presents a general definition of pseudo-differential operators of type 1,1; the definition is shown to be the largest one that is both compatible with negliible operators and stable under vanishing frequency modulation. Elaborating counter-examples of Ching, Hörmander and Parenti...

  5. Type 1,1-operators defined by vanishing frequency modulation

    DEFF Research Database (Denmark)

    Johnsen, Jon

    This paper presents a general definition of pseudo-differential operators of type 1,1; the definition is shown to be the largest one that is both compatible with negligible operators and stable under vanishing frequency modulation. Elaborating counter-examples of Ching andHörmander, type 1...

  6. Frequency modulation via the Doppler effect in optical fibers.

    Science.gov (United States)

    Oberson, P; Huttner, B; Gisin, N

    1999-04-01

    We present the principle of optical frequency modulation via the Doppler effect obtained by rapidly stretching an optical fiber and thus modifying the optical path of the light propagating in the fiber. This procedure creates a pure frequency shift, with no degradation of the spectrum. Moreover, the effect is wavelength independent and can therefore be applied to any type of light source. We show an experimental realization in which a frequency excursion of ~100 MHz was obtained with a bobbin vibrating at 180 Hz.

  7. Frequency-dependent signal transmission and modulation by neuromodulators

    Directory of Open Access Journals (Sweden)

    Hiroshi T Ito

    2008-12-01

    Full Text Available The brain uses a strategy of labor division, which may allow it to accomplish more elaborate and complicated tasks, but in turn, imposes a requirement for central control to integrate information among different brain areas. Anatomically, the divergence of long-range neuromodulator projections appears well-suited to coordinate communication between brain areas. Oscillatory brain activity is a prominent feature of neural transmission. Thus, the ability of neuromodulators to modulate signal transmission in a frequency-dependent manner adds an additional level of regulation. Here, we review the significance of frequency-dependent signal modulation in brain function and how a neuronal network can possess such properties. We also describe how a neuromodulator, dopamine, changes frequency-dependent signal transmission, controlling information flow from the entorhinal cortex to the hippocampus.

  8. Accurate, explicit formulae for higher harmonic force spectroscopy by frequency modulation-AFM.

    Science.gov (United States)

    Kuchuk, Kfir; Sivan, Uri

    2015-01-01

    The nonlinear interaction between an AFM tip and a sample gives rise to oscillations of the cantilever at integral multiples (harmonics) of the fundamental resonance frequency. The higher order harmonics have long been recognized to hold invaluable information on short range interactions but their utilization has thus far been relatively limited due to theoretical and experimental complexities. In particular, existing approximations of the interaction force in terms of higher harmonic amplitudes generally require simultaneous measurements of multiple harmonics to achieve satisfactory accuracy. In the present letter we address the mathematical challenge and derive accurate, explicit formulae for both conservative and dissipative forces in terms of an arbitrary single harmonic. Additionally, we show that in frequency modulation-AFM (FM-AFM) each harmonic carries complete information on the force, obviating the need for multi-harmonic analysis. Finally, we show that higher harmonics may indeed be used to reconstruct short range forces more accurately than the fundamental harmonic when the oscillation amplitude is small compared with the interaction range.

  9. Understanding 2D atomic resolution imaging of the calcite surface in water by frequency modulation atomic force microscopy

    Science.gov (United States)

    Tracey, John; Miyazawa, Keisuke; Spijker, Peter; Miyata, Kazuki; Reischl, Bernhard; Federici Canova, Filippo; Rohl, Andrew L.; Fukuma, Takeshi; Foster, Adam S.

    2016-10-01

    Frequency modulation atomic force microscopy (FM-AFM) experiments were performed on the calcite (10\\bar{1}4) surface in pure water, and a detailed analysis was made of the 2D images at a variety of frequency setpoints. We observed eight different contrast patterns that reproducibly appeared in different experiments and with different measurement parameters. We then performed systematic free energy calculations of the same system using atomistic molecular dynamics to obtain an effective force field for the tip-surface interaction. By using this force field in a virtual AFM simulation we found that each experimental contrast could be reproduced in our simulations by changing the setpoint, regardless of the experimental parameters. This approach offers a generic method for understanding the wide variety of contrast patterns seen on the calcite surface in water, and is generally applicable to AFM imaging in liquids.

  10. Modulation of induced frontocentral theta (Fm-theta) event-related (de-)synchronisation dynamics following mindfulness-based cognitive therapy in Major Depressive Disorder

    NARCIS (Netherlands)

    Schoenberg, P.L.; Speckens, A.E.M.

    2014-01-01

    Depressive severity has been associated with attenuated neocortical frontal midline theta (Fm-theta) power/evoked activity. Mindfulness-Based Cognitive Therapy (MBCT) has shown to be a successful novel intervention for Major Depressive Disorder (MDD), albeit precise working mechanisms remain elusive

  11. Magnetostatic surface waves in an FM/LH/FM sandwiched structure

    Energy Technology Data Exchange (ETDEWEB)

    Ma Jianing; Li Hua; Zhang Qiang; Yin Yongqi; Wang Xuanzhang, E-mail: limjn@126.co [Provincial Key Laboratory for Advanced Functional Material and Excited States Processes, School of Physics and Electronic Engineering, Harbin Normal University, Harbin 150025 (China)

    2010-07-15

    Properties of magnetostatic surface waves in a magnetic structure with one left-handed material (LHM) film sandwiched between two ferromagnetic (FM) films are discussed, where FM films are magnetized to be saturated by an external field parallel to the film surfaces and the LHM film has a constant and negative magnetic permeability. Besides the surface magnetostatic wave lying in the same frequency range as that of a single film, two new branches of surface magnetostatic waves with negative group velocity are found in different frequency ranges. The new branches propagate along the inner surface of an FM film, but the other propagates along the outer surface.

  12. High Frequency Modulation Method for Measuring of Birefringence

    Directory of Open Access Journals (Sweden)

    Šulc M.

    2013-05-01

    Full Text Available A method of optical birefringence measurement is presented. It uses an el ectro-optic modulator for the high frequency modulation of polarization of the laser beam. The developed optical apparatus exhibits high sensitivity. It is able to measure very small birefringence of samples down to 10-3 rad. The accuracy and sensitivity of the method was checked by measurement of calibrated Sol eil – Babi net compensator. Method can be also used for online and accurate measurement of an optical components birefringence. This application was developed with the aim to measure Cotton-Mouton effect in air and nitrogen.

  13. Basics and first experiments demonstrating isolation improvements in the agile polarimetric FM-CW radar – PARSAX

    NARCIS (Netherlands)

    Krasnov, O.A.; Babur, G.P.; Wang, Z.; Ligthart, L.P.; Van der Zwan, F.

    2010-01-01

    The article describes the IRCTR PARSAX radar system, the S-band high-resolution Doppler polarimetric frequency modulated continuous wave (FM-CW) radar with dual-orthogonal sounding signals, which has the possibility to measure all elements of the radar target polarization scattering matrix

  14. Radio-frequency-modulated Rydberg states in a vapor cell

    CERN Document Server

    Miller, Stephanie A; Raithel, Georg

    2016-01-01

    We measure strong radio-frequency (RF) electric fields using rubidium Rydberg atoms prepared in a room-temperature vapor cell as field sensors. Electromagnetically induced transparency is employed as an optical readout. We RF-modulate the 60$S_{1/2}$ and 58$D_{5/2}$ Rydberg states with 50~MHz and 100~MHz fields, respectively. For weak to moderate RF fields, the Rydberg levels become Stark-shifted, and sidebands appear at even multiples of the driving frequency. In high fields, the adjacent hydrogenic manifold begins to intersect the shifted levels, providing rich spectroscopic structure suitable for precision field measurements. A quantitative description of strong-field level modulation and mixing of $S$ and $D$ states with hydrogenic states is provided by Floquet theory. Additionally, we estimate the shielding of DC electric fields in the interior of the glass vapor cell.

  15. Spread spectrum communication system with chaotic frequency modulation

    Science.gov (United States)

    Volkovskii, A. R.; Tsimring, L. Sh.; Rulkov, N. F.; Langmore, I.

    2005-09-01

    A new spread spectrum communication system utilizing chaotic frequency modulation of sinusoidal signals is discussed. A single phase lock loop (PLL) system in the receiver is used both to synchronize the local chaotic oscillator and to recover the information signal. We study the dynamics of the synchronization process, stability of the PLL system, and evaluate the bit-error-rate performance of this chaos-based communication system.

  16. Polarization decoherence differential frequency-modulated continuous-wave gyroscope.

    Science.gov (United States)

    Zheng, Chao; Zheng, Gang; Han, Liwei; Luo, Jianhua; Teng, Fei; Wang, Bing; Song, Ping; Gao, Kun; Hou, Zhiqing

    2014-12-01

    A polarization decoherence differential frequency-modulated continuous-wave (FMCW) gyroscope is presented. The impact of coherent polarization crosstalk noise on the differential FMCW gyro is analyzed. In order to suppress coherent polarization crosstalk noise, a novel method was proposed to produce two incoherent orthogonal polarization narrow band beams from laser diode. In this way, the random drift has been reduced about one order.

  17. Primary somatosensory contextual modulation is encoded by oscillation frequency change.

    Science.gov (United States)

    Götz, T; Milde, T; Curio, G; Debener, S; Lehmann, T; Leistritz, L; Witte, O W; Witte, H; Haueisen, J

    2015-09-01

    This study characterized thalamo-cortical communication by assessing the effect of context-dependent modulation on the very early somatosensory evoked high-frequency oscillations (HF oscillations). We applied electrical stimuli to the median nerve together with an auditory oddball paradigm, presenting standard and deviant target tones representing differential cognitive contexts to the constantly repeated electrical stimulation. Median nerve stimulation without auditory stimulation served as unimodal control. A model consisting of one subcortical (near thalamus) and two cortical (Brodmann areas 1 and 3b) dipolar sources explained the measured HF oscillations. Both at subcortical and the cortical levels HF oscillations were significantly smaller during bimodal (somatosensory plus auditory) than unimodal (somatosensory only) stimulation. A delay differential equation model was developed to investigate interactions within the 3-node thalamo-cortical network. Importantly, a significant change in the eigenfrequency of Brodmann area 3b was related to the context-dependent modulation, while there was no change in the network coupling. This model strongly suggests cortico-thalamic feedback from both cortical Brodmann areas 1 and 3b to the thalamus. With the 3-node network model, thalamo-cortical feedback could be described. Frequency encoding plays an important role in contextual modulation in the somatosensory thalamo-cortical network. Copyright © 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  18. Spatio-temporal encoding using narrow-band linear frequency modulated signals in synthetic aperture ultrasound imaging

    DEFF Research Database (Denmark)

    Gran, Fredrik; Jensen, Jørgen Arendt

    2005-01-01

    energy, the signal to noise ratio will increase. However, to focus the data properly using the STA approach, the transmitters have to be separated from each other. This is done by dividing the available spectrum into several subbands with a small overlap. Separating different transmitters can be done......, thus, be avoided. To further increase the transmitted energy, the excitation waveforms are designed as linear frequency modulated (FM) signals. This makes it possible to maintain the full excitation amplitude during most of the transmission. The design of the separation filters will also be discussed...... the proposed method achieved approximately 2 cm improvement in penetration depth. The signal to noise ratio was also measured, where the gain was ∼ 7 dB in comparison to the reference....

  19. System and Method for Generating a Frequency Modulated Linear Laser Waveform

    Science.gov (United States)

    Pierrottet, Diego F. (Inventor); Petway, Larry B. (Inventor); Amzajerdian, Farzin (Inventor); Barnes, Bruce W. (Inventor); Lockard, George E. (Inventor); Hines, Glenn D. (Inventor)

    2017-01-01

    A system for generating a frequency modulated linear laser waveform includes a single frequency laser generator to produce a laser output signal. An electro-optical modulator modulates the frequency of the laser output signal to define a linear triangular waveform. An optical circulator passes the linear triangular waveform to a band-pass optical filter to filter out harmonic frequencies created in the waveform during modulation of the laser output signal, to define a pure filtered modulated waveform having a very narrow bandwidth. The optical circulator receives the pure filtered modulated laser waveform and transmits the modulated laser waveform to a target.

  20. System and Method for Generating a Frequency Modulated Linear Laser Waveform

    Science.gov (United States)

    Pierrottet, Diego F. (Inventor); Petway, Larry B. (Inventor); Amzajerdian, Farzin (Inventor); Barnes, Bruce W. (Inventor); Lockard, George E. (Inventor); Hines, Glenn D. (Inventor)

    2014-01-01

    A system for generating a frequency modulated linear laser waveform includes a single frequency laser generator to produce a laser output signal. An electro-optical modulator modulates the frequency of the laser output signal to define a linear triangular waveform. An optical circulator passes the linear triangular waveform to a band-pass optical filter to filter out harmonic frequencies created in the waveform during modulation of the laser output signal, to define a pure filtered modulated waveform having a very narrow bandwidth. The optical circulator receives the pure filtered modulated laser waveform and transmits the modulated laser waveform to a target.

  1. Active mode locking at 50 GHz repetition frequency by half-frequency modulation of monolithic semiconductor lasers integrated with electroabsorption modulators

    Science.gov (United States)

    Sato, Kenji; Kotaka, Isamu; Kondo, Yasuhiro; Yamamoto, Mitsuo

    1996-10-01

    Active mode locking achieved at a 50 GHz repetition frequency by modulation at half (25 GHz) the cavity resonance frequency using a monolithic mode-locked InGaAsP laser integrated with an electroabsorption modulator is described. A pulse width of around 3 ps and a high suppression ratio of more than 33 dB of the intensity modulation at the driving frequency are obtained.

  2. High-speed laser modulation beyond the relaxation resonance frequency limit.

    Science.gov (United States)

    Sacher, Wesley D; Zhang, Eric J; Kruger, Brett A; Poon, Joyce K S

    2010-03-29

    We propose and show that for coupling modulated lasers (CMLs), in which the output coupler is modulated rather than the pump rate, the conventional relaxation resonance frequency limit to the laser modulation bandwidth can be circumvented. The modulation response is limited only by the coupler. Although CMLs are best suited to microcavities, as a proof-of-principle, a coupling-modulated erbium-doped fiber laser is modulated at 1 Gb/s, over 10000 times its relaxation resonance frequency.

  3. Optical Frequency-Modulated Continuous-Wave (FMCW) Interferometry

    CERN Document Server

    Zheng, Jesse

    2005-01-01

    This book introduces the optical frequency-modulated continuous-wave (FMCW) interferometry - a new field of optics that is derived from radar. The study of optical FMCW interference not only updates our knowledge about the nature of light, but also creates an advanced technology for precision measurements. The principles, applications and signal processing of optical FMCW interference are systematically discussed. This book is intended for scientists and engineers in both academia and industry. It is especially suited to professionals who are working in the field of measurement instruments.

  4. Source of spill ripple in the RF-KO slow-extraction method with FM and AM

    Science.gov (United States)

    Noda, K.; Furukawa, T.; Shibuya, S.; Muramatsu, M.; Uesugi, T.; Kanazawa, M.; Torikoshi, M.; Takada, E.; Yamada, S.

    2002-10-01

    The RF-knockout (RF-KO) slow-extraction method with frequency modulation (FM) and amplitude modulation (AM) has brought high-accuracy irradiation to the treatment of a cancer tumor moving with respiration, because of a quick response to beam start/stop. However, a beam spill extracted from a synchrotron ring through RF-KO slow-extraction has a huge ripple with a frequency of around 1 kHz related to the FM. The spill ripple will disturb the lateral dose distribution in the beam scanning methods. Thus, the source of the spill ripple has been investigated through experiments and simulations. There are two tune regions for the extraction process through the RF-KO method: the extraction region and the diffusion region. The particles in the extraction region can be extracted due to amplitude growth through the transverse RF field, only when its frequency matches with the tune in the extraction region. For a large chromaticity, however, the particles in the extraction region can be extracted through the synchrotron oscillation, even when the frequency does not match with the tune in the extraction region. Thus, the spill structure during one period of the FM strongly depends on the horizontal chromaticity. They are repeated with the repetition frequency of the FM, which is the very source of the spill ripple in the RF-KO method.

  5. Single-cycle-PLL detection for real-time FM-AFM applications.

    Science.gov (United States)

    Schlecker, Benedikt; Dukic, Maja; Erickson, Blake; Ortmanns, Maurits; Fantner, Georg; Anders, Jens

    2014-04-01

    In this paper we present a novel architecture for phase-locked loop (PLL) based high-speed demodulation of frequency-modulated (FM) atomic force microscopy (AFM) signals. In our approach, we use single-sideband (SSB) frequency upconversion to translate the AFM signal from the position sensitive detector to a fixed intermediate frequency (IF) of 10 MHz. In this way, we fully benefit from the excellent noise performance of PLL-based FM demodulators still avoiding the intrinsic bandwidth limitation of such systems. In addition, the upconversion to a fixed IF renders the PLL demodulator independent of the cantilever's resonance frequency, allowing the system to work with a large range of cantilever frequencies. To investigate if the additional noise introduced by the SSB upconverter degrades the system noise figure we present a model of the AM-to-FM noise conversion in PLLs incorporating a phase-frequency detector. Using this model, we can predict an upper corner frequency for the demodulation bandwidth above which the converted noise from the single-sideband upconverter becomes the dominant noise source and therefore begins to deteriorate the overall system performance. The approach is validated by both electrical and AFM measurements obtained with a PCB-based prototype implementing the proposed demodulator architecture.

  6. Research on a Micro-Grid Frequency Modulation Strategy Based on Optimal Utilization of Air Conditioners

    Directory of Open Access Journals (Sweden)

    Qingzhu Wan

    2016-12-01

    Full Text Available With the proportion of air conditioners increasing gradually, they can provide a certain amount of frequency-controlled reserves for a micro-grid. Optimizing utilization of air conditioners and considering load response characteristics and customer comfort, the frequency adjustment model is a quadratic function model between the trigger temperature of the air conditioner compressor, and frequency variation is provided, which can be used to regulate the trigger temperature of the air conditioner when the micro-grid frequency rises and falls. This frequency adjustment model combines a primary frequency modulation method and a secondary frequency modulation method of the energy storage system, in order to optimize the frequency of a micro-grid. The simulation results show that the frequency modulation strategy for air conditioners can effectively improve the frequency modulation ability of air conditioners and frequency modulation effects of a micro-grid in coordination with an energy storage system.

  7. Frequency position modulation using multi-spectral projections

    Science.gov (United States)

    Goodman, Joel; Bertoncini, Crystal; Moore, Michael; Nousain, Bryan; Cowart, Gregory

    2012-10-01

    In this paper we present an approach to harness multi-spectral projections (MSPs) to carefully shape and locate tones in the spectrum, enabling a new and robust modulation in which a signal's discrete frequency support is used to represent symbols. This method, called Frequency Position Modulation (FPM), is an innovative extension to MT-FSK and OFDM and can be non-uniformly spread over many GHz of instantaneous bandwidth (IBW), resulting in a communications system that is difficult to intercept and jam. The FPM symbols are recovered using adaptive projections that in part employ an analog polynomial nonlinearity paired with an analog-to-digital converter (ADC) sampling at a rate at that is only a fraction of the IBW of the signal. MSPs also facilitate using commercial of-the-shelf (COTS) ADCs with uniform-sampling, standing in sharp contrast to random linear projections by random sampling, which requires a full Nyquist rate sample-and-hold. Our novel communication system concept provides an order of magnitude improvement in processing gain over conventional LPI/LPD communications (e.g., FH- or DS-CDMA) and facilitates the ability to operate in interference laden environments where conventional compressed sensing receivers would fail. We quantitatively analyze the bit error rate (BER) and processing gain (PG) for a maximum likelihood based FPM demodulator and demonstrate its performance in interference laden conditions.

  8. Study on moving target detection to passive radar based on FM broadcast transmitter

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Target detection by a noncooperative illuminator is a topic of general interest in the electronic warfare field.First of all,direct-path interference(DPI)suppression which is the technique of bottleneck of moving target detection by a noncooperative frequency modulation(FM) broadcast transmitter is analyzed in this article;Secondly,a space-time-frequency domain synthetic solution to this problem is introduced:Adaptive nulling array processing is considered in the space domain,DPI cancellation based on adaptive fractional delay interpolation(AFDI)technique is used in planned time domain,and long-time coherent integration is utilized in the frequency domain;Finally,an experimental system is planned by considering FM broadcast transmitter as a noncooperative illuminator,Simulation results by real collected data show that the proposed method has a better performance of moving target detection.

  9. Theoretical Study of Amplitude Modulation Application during Radio Frequency Electrocoagulation

    Directory of Open Access Journals (Sweden)

    V. A. Karpuhin

    2015-01-01

    Full Text Available This article concerns the investigation results of influence of the amplitude-modulated acting signal parameters on the thermoelectric characteristics of biological tissues for a specified geometry of the working electrode section during RF mono-polar electrocoagulation. The geometric model ‘electrode - a biological tissue’ was suggested to study the distribution of power and temperature fields in biological tissue during mono-polar coagulation. The model of biological tissue is represented as a cylinder and the needle electrode is an ellipsoid immersed in the biological tissue. The heat and quasi-electrostatics equations are used as a mathematical model. These equations are solved in Comsol Multiphysics environment.As a result, we have got the following findings: the technique of calculating parameters of the PAM acting signal which has a fixed carrier frequency for the needle electrode of a specified geometry and the immersion depth in biological tissues is suggested. Parameters of PAM signal are determined for this electrode geometry. These parameters provide a 60 ... 80°C heating range of biological tissues near the working part of the tool for different amplitudes of acting signal during RF coagulation. It has been found out that both the temperature and the relaxation frequency of biological tissue depend on exposure time for the needle electrode of a specified geometry and immersion depth of the working part of tool into biological tissue.It is shown that the relaxation frequency of the biological tissue, subjected to the radiofrequency pulses, linearly depends on its heating temperature and can be used as a numerical criterion for maintaining the specified temperature conditions. It is found that the relaxation frequency of the biological tissue depends on the contact area of the tool working part and biological tissues. To reduce this dependence it is necessary to provide automatic current control of the output action.

  10. Modulation of ionization on laser frequency in ultra-short pulse intense laser-gas-target

    Institute of Scientific and Technical Information of China (English)

    Hu Qiang-Lin; Liu Shi-Bing

    2006-01-01

    Based on the dispersion relation of intense laser pulse propagating in gradually ionized plasma, this paper discusses the frequency modulation induced by ionization of an ultra-short intense laser pulse interacting with a gas target.The relationship between the frequency modulation and the ionization rate, the plasmas frequency variation, and the polarization of atoms (ions) is analysed. The numerical results indicate that, at high frequency, the polarization of atoms (ions) plays a more important role than plasma frequency variation in modulating the laser frequency, and the laser frequency variation is different at different positions of the laser pulse.

  11. Frequency modulated continuous wave lidar performance model for target detection

    Science.gov (United States)

    Du Bosq, Todd W.; Preece, Bradley L.

    2017-05-01

    The desire to provide the warfighter both ranging and reflected intensity information is increasing to meet expanding operational needs. LIDAR imaging systems can provide the user with intensity, range, and even velocity information of a scene. The ability to predict the performance of LIDAR systems is critical for the development of future designs without the need to conduct time consuming and costly field studies. Performance modeling of a frequency modulated continuous wave (FMCW) LIDAR system is challenging due to the addition of the chirped laser source and waveform mixing. The FMCW LIDAR model is implemented in the NV-IPM framework using the custom component generation tool. This paper presents an overview of the FMCW Lidar, the customized LIDAR components, and a series of trade studies using the LIDAR model.

  12. Research on Feature Extraction of Composite Pseudocode Phase Modulation-Carrier Frequency Modulation Signal Based on PWD Transform

    Institute of Scientific and Technical Information of China (English)

    LI Ming-zi; ZHAO Hui-chang

    2008-01-01

    The identification features of composite pseudocode phase modulation and carry frequency modulation signal in-clude pseudocode and modulation frequency. In this paper, PWD is used to extract these features. First, the feature of pseudocode is extracted using the amplitude output of PWD and the correlation filter technology. Then the feature of fre-quency modulation is extracted by way of PWD analysis on the signal processed by anti-phase operation according to the extracted feature of pseudo code, i.e. position information of changed abruptly point of phase. The simulation result shows that both the features of frequency modulation and phase change position caused by the pseudocode phase modula-tion can be extracted effectively for SNR = 3 dB.

  13. Frequency-shift vibro-acoustic modulation driven by low-frequency broadband excitations in a bistable cantilever oscillator

    Science.gov (United States)

    He, Qingbo; Xu, Yanyan; Lu, Siliang; Shao, Yong

    2017-03-01

    This paper reports a frequency-shift vibro-acoustic modulation (VAM) effect in a bistable microcracked cantilever oscillator. Low-frequency broadband excitations induced a VAM effect with a shifted modulation frequency through involving a microcracked metal beam in a bistable oscillator model. We used nonlinear dynamics equations and principles to describe the mechanism of a bistable oscillator whose natural frequency varied as the oscillation amplitude increased. We demonstrated this frequency-shift VAM effect using a prototype bistable oscillator model designed to efficiently detect microcracks in solid materials via the VAM effect using ambient vibration excitations.

  14. Note: A frequency modulated wireless interrogation system exploiting narrowband acoustic resonator for remote physical quantity measurement.

    Science.gov (United States)

    Droit, C; Martin, G; Ballandras, S; Friedt, J-M

    2010-05-01

    We demonstrate the wireless conversion of frequency modulation to amplitude modulation by radio frequency resonators as means of accurately determining the resonance frequency of passive acoustoelectronic sensors. The emitted frequency modulated radio frequency pulses are generated by a pulsed radar for probing a surface acoustic wave based sensor. The sharp sign transition of the amplitude modulated received signal provides a signal on which a feedback loop is locked to monitor the resonance signal. The strategy is demonstrated using a full software implementation on a generic hardware, resulting in 2 Hz resolution at 1 s integration time limited by the proportional feedback loop.

  15. Brillouin optical correlation analysis system using a simplified frequency-modulated time division method

    Science.gov (United States)

    Choi, Bo-Hun; Kwon, Il-Bum

    2014-01-01

    A time-division Brillouin optical correlation domain analysis system was successfully achieved using simplified laser diode (LD) modulation and pump lightwave optimization. A complicated transfer function for a precise output waveform of a LD was required for the conventional system. However, a very simple modulation function gave a power output very close to a required ideal rectangle waveform without sacrificing optical output spectrum. An electrical input waveform applied into a gate in the pump lightwave path was also optimized for eliminating a probe lightwave included in a pump lightwave and for passing consecutive pump pulses alternatively. So the stimulated Brillouin scattering gain was attained without seriously distorting FM modulation, and the targeted spatial resolution was clearly accomplished. Additionally, using high speed response of a semiconductor optical amplifier (SOA), unlike an erbium-doped fiber amplifier (EDFA), the possibility was investigated that an SOA was going to replace an EDFA and a modulator used as a gate in the same time.

  16. Low-cost FM oscillator for capacitance type of blade tip clearance measurement system

    Science.gov (United States)

    Barranger, John P.

    1987-01-01

    The frequency-modulated (FM) oscillator described is part of a blade tip clearance measurement system that meets the needs of a wide class of fans, compressors, and turbines. As a result of advancements in the technology of ultra-high-frequency operational amplifiers, the FM oscillator requires only a single low-cost integrated circuit. Its carrier frequency is 42.8 MHz when it is used with an integrated probe and connecting cable assembly consisting of a 0.81 cm diameter engine-mounted capacitance probe and a 61 cm long hermetically sealed coaxial cable. A complete circuit analysis is given, including amplifier negative resistance characteristics. An error analysis of environmentally induced effects is also derived, and an error-correcting technique is proposed. The oscillator can be calibrated in the static mode and has a negative peak frequency deviation of 400 kHz for a rotor blade thickness of 1.2 mm. High-temperature performance tests of the probe and 13 cm of the adjacent cable show good accuracy up to 600 C, the maximum permissible seal temperature. The major source of error is the residual FM oscillator noise, which produces a clearance error of + or - 10 microns at a clearance of 0.5 mm. The oscillator electronics accommodates the high rotor speeds associated with small engines, the signals from which may have frequency components as high as 1 MHz.

  17. Locking of self-oscillation frequency by pump modulation in an erbium-doped fiber laser

    Science.gov (United States)

    Pisarchik, A. N.; Barmenkov, Yu. O.

    2005-10-01

    Frequency locking of self-oscillations in a diode-pumped erbium-doped fiber laser by external modulation of the diode current is studied experimentally. The coexistence of locking and unlocking regimes is detected. The condition for onset of the bistability and dependences of the frequency detuning on the modulation frequency and amplitude are established. Transitions to torus-chaos are also demonstrated.

  18. Carrier frequency modulation of an acousto-optic modulator for laser stabilization.

    Science.gov (United States)

    Aldous, Matthew; Woods, Jonathan; Dragomir, Andrei; Roy, Ritayan; Himsworth, Matt

    2017-05-29

    The stabilization of lasers to absolute frequency references is a fundamental requirement in several areas of atomic, molecular and optical physics. A range of techniques are available to produce a suitable reference onto which one can 'lock' the laser, many of which depend on the specific internal structure of the reference or are sensitive to laser intensity noise. We present a novel method using the frequency modulation of an acousto-optic modulator's carrier (drive) signal to generate two spatially separated beams, with a frequency difference of only a few MHz. These beams are used to probe a narrow absorption feature and the difference in their detected signals leads to a dispersion-like feature suitable for wavelength stabilization of a diode laser. This simple and versatile method only requires a narrow absorption line and is therefore suitable for both atomic and cavity based stabilization schemes. To demonstrate the suitability of this method we lock an external cavity diode laser near the (85)Rb 5S1/2 → 5P3/2, F = 3 → F' = 4 using sub-Doppler pump probe spectroscopy and also demonstrate excellent agreement between the measured signal and a theoretical model.

  19. Low frequency steady-state brain responses modulate large scale functional networks in a frequency-specific means.

    Science.gov (United States)

    Wang, Yi-Feng; Long, Zhiliang; Cui, Qian; Liu, Feng; Jing, Xiu-Juan; Chen, Heng; Guo, Xiao-Nan; Yan, Jin H; Chen, Hua-Fu

    2016-01-01

    Neural oscillations are essential for brain functions. Research has suggested that the frequency of neural oscillations is lower for more integrative and remote communications. In this vein, some resting-state studies have suggested that large scale networks function in the very low frequency range (brain networks because both resting-state studies and conventional frequency tagging approaches cannot simultaneously capture multiple large scale networks in controllable cognitive activities. In this preliminary study, we aimed to examine whether large scale networks can be modulated by task-induced low frequency steady-state brain responses (lfSSBRs) in a frequency-specific pattern. In a revised attention network test, the lfSSBRs were evoked in the triple network system and sensory-motor system, indicating that large scale networks can be modulated in a frequency tagging way. Furthermore, the inter- and intranetwork synchronizations as well as coherence were increased at the fundamental frequency and the first harmonic rather than at other frequency bands, indicating a frequency-specific modulation of information communication. However, there was no difference among attention conditions, indicating that lfSSBRs modulate the general attention state much stronger than distinguishing attention conditions. This study provides insights into the advantage and mechanism of lfSSBRs. More importantly, it paves a new way to investigate frequency-specific large scale brain activities.

  20. FM consolidation plan

    CERN Document Server

    Nonis, M; CERN. Geneva. TS Department

    2008-01-01

    The average life duration of infrastructure being 30 years, preventive or corrective maintenance is not enough to guarantee the perpetuity of the operation of equipment and installation in order to assure the maintain of the patrimony in a functional state. At CERN, such is the age of the civil engineering infrastructure and the relative technical equipment that urgent and appropriate consolidation programs shall be established. The big number of aged buildings and equipment entails that priorities are defined. This paper realizes a portrait of the actual situation and related problems, based on data extracted from D7i and inventories carried out by TS/FM group; at the same time it defines an interventions planning which optimizes safety aspects and maintenance costs. The timing of these interventions depends on the availability of specific resources.

  1. [Research of dual-photoelastic-modulator-based beat frequency modulation and Fourier-Bessel transform imaging spectrometer].

    Science.gov (United States)

    Wang, Zhi-Bin; Zhang, Rui; Wang, Yao-Li; Huang, Yan-Fei; Chen, You-Hua; Wang, Li-Fu; Yang, Qiang

    2014-02-01

    As the existing photoelastic-modulator(PEM) modulating frequency in the tens of kHz to hundreds of kHz between, leading to frequency of modulated interference signal is higher, so ordinary array detector cannot effectively caprure interference signal..A new beat frequency modulation method based on dual-photoelastic-modulator (Dual-PEM) and Fourier-Bessel transform is proposed as an key component of dual-photoelastic-modulator-based imaging spectrometer (Dual-PEM-IS) combined with charge coupled device (CCD). The dual-PEM are operated as an electro-optic circular retardance modulator, Operating the PEMs at slightly different resonant frequencies w1 and w2 respectively, generates a differential signal at a much lower heterodyne frequency that modulates the incident light. This method not only retains the advantages of the existing PEM, but also the frequency of modulated photocurrent decreased by 2-3 orders of magnitude (10-500 Hz) and can be detected by common array detector, and the incident light spectra can be obtained by Fourier-Bessel transform of low frequency component in the modulated signal. The method makes the PEM has the dual capability of imaging and spectral measurement. The basic principle is introduced, the basic equations is derived, and the feasibility is verified through the corresponding numerical simulation and experiment. This method has' potential applications in imaging spectrometer technology, and analysis of the effect of deviation of the optical path difference. This work provides the necessary theoretical basis for remote sensing of new Dual-PEM-IS and for engineering implementation of spectra inversion.

  2. Cylindrical PVF2 film based fiber optic phase modulator - Phase shift nonlinearity and frequency response

    Science.gov (United States)

    Sudarshanam, V. S.; Claus, Richard O.

    1993-03-01

    A new cylindrical coil configuration for polyvinylidene flouride (PVF2) film based fiber optic phase modulator is studied for the frequency response and nonlinearity of phase shift at the resonance frequency. This configuration, hitherto unapproached for PVF2 film modulators, offers resonance at well defined, controllable and higher frequencies than possible for the flat-strip configuration. Two versions of this configuration are presented that differ strongly in both the resonance frequency and the phase shift nonlinearity coefficient.

  3. Higher-order modulations of fs laser pulses for GHz frequency domain photon migration system.

    Science.gov (United States)

    Lin, Huang-Yi; Cheng, Nanyu; Tseng, Sheng-Hao; Chan, Ming-Che

    2014-02-24

    Except the fundamental modulation frequency, by higher-order-harmonic modulations of mode-locked laser pulses and a simple frequency demodulation circuit, a novel approach to GHz frequency-domain-photon-migration (FDPM) system was reported. With this novel approach, a wide-band modulation frequency comb is available without any external modulation devices and the only electronics to extract the optical attenuation and phase properties at a selected modulation frequency in FDPM systems are good mixers and lock-in devices. This approach greatly expands the frequency range that could be achieved by conventional FDPM systems and suggests that our system could extract much more information from biological tissues than the conventional FDPM systems. Moreover, this demonstration will be beneficial for discerning the minute change of tissue properties.

  4. Complex sound analysis in the lesser bulldog bat: evidence for a mechanism for processing frequency elements of frequency modulated signals over restricted time intervals.

    Science.gov (United States)

    Roverud, R C

    1994-05-01

    A stereotypical approach phase vocalization response of the lesser bulldog bat, Noctilio albiventris, to artificial echoes simulating a virtual approaching object was used to assess the ability of the bat to analyze and extract distance information from the artificial echoes. The performance of the bat was not significantly different when presented with naturally structured CF/FM echoes containing FM elements that sweep continuously from about 75-55 kHz in 4 ms or with CF/FM echoes containing FM components constructed from a series of 98 pure tone frequency steps, each with a duration of 0.04 ms. The performance of the bat remained unchanged when the duration of the tone steps was increased up to 0.08 ms but declined sharply to a level that was significantly below that seen with a naturally structured echo when the steps were 0.09 ms or longer. The performance of the bat depended on the duration of the individual tone steps, which could not exceed a specific upper limit of about 0.08 ms. The study suggests that the bats have adaptations for processing individual narrow band segments of FM signals over specific time intervals.

  5. Frequency Modulation of Directly Imaged Exoplanets: Geometric Effect as a Probe of Planetary Obliquity

    CERN Document Server

    Kawahara, Hajime

    2016-01-01

    We consider the time-frequency analysis of a scattered light curve by a directly imaged exoplanet. We show that the geometric effect due to planetary obliquity and orbital inclination induce the frequency modulation of the apparent diurnal periodicity. We construct a model of the frequency modulation and compare with the instantaneous frequency extracted from the pseudo-Wigner distribution of the simulated light curves of a cloudless Earth. The model provides good agreement with the simulated modulation factor even for the light curve with Gaussian noise comparable to the signal. Notably, the shape of the instantaneous frequency is sensitive to the difference between prograde, retrograde, and pole-on spin rotations. Whereas our technique requires the static property of the albedo map, it does not need to solve the albedo map of the planet. The time-frequency analysis is complementary to other methods which utilize the amplitude modulation. This paper demonstrates the importance of the frequency domain of the ...

  6. Modulation Frequency Multiplexed Tunable Diode Laser Spectroscopy System for Simultaneous CO, CO2 Measurements

    Institute of Scientific and Technical Information of China (English)

    CHEN Dong; LIU Wen-Qing; ZHANG Yu-Jun; LIU Jian-Guo; WEI Qing-Nong; KAN Rui-Feng; WANG Min; CUI Yi-Ben; CHEN Jiu-Ying

    2006-01-01

    @@ A modulation frequency multiplexed dual diode-laser system is developed for simultaneous detection of the two most common fire gas products CO and CO2. Simultaneous detection is achieved by modulating each laser at different frequencies, demodulating the signal by a pair of lock-in amplifiers for each gas.

  7. On the Frequency Correction in Temperature-Modulated Differential Scanning Calorimetry of Glass Transition

    DEFF Research Database (Denmark)

    Guo, Xiaoju; Mauro, J.C.; Allan, D.C.;

    2012-01-01

    Temperature-modulated differential scanning calorimetry (TMDSC) is based on conventional DSC but with a sinusoidally modulated temperature path. Simulations of TMDSC signals were performed for Corning EAGLE XG® glass over a wide range of modulation frequencies. Our results reveal that the frequen...

  8. [Change of cholinesterase relative activity under modulated ultra high frequency electromagnetic radiation in experiments in vitro].

    Science.gov (United States)

    Pashovkina, M S; Pashovkin, T N

    2011-01-01

    Changes in the activity of enzyme cholinesterase (ChE) have been experimentally investigated under the influence of amplitude-modulated super-high-frequency electromagnetic radiation (carrier frequency of 2.375 MHz; power flux density of 8 mW/cm2, 20 mW/cm2 and 50 mW/cm2; modulation frequency range 10 to 210 Hz; exposure time 5 min). The appearance of peaks of the cholinesterase increased relative activity, as well as the changes in the direction and intensity of the reaction associated with the modulation frequency and power flux are observed at equal power flux densities and exposure times.

  9. Gauss linear frequency modulation wavelet transforms and its application to seismic phases identification

    Institute of Scientific and Technical Information of China (English)

    刘希强; 周惠兰; 曹文海; 李红; 李永红; 季爱东

    2002-01-01

    Based on the characteristics of gradual change style seismic signal onset which has more high frequency signal components but less magnitude, this paper selects Gauss linear frequency modulation wavelet as base function to study the change characteristics of Gauss linear frequency modulation wavelet transform with difference wavelet and signal parameters, analyzes the error origin of seismic phases identification on the basis of Gauss linear frequency modulation wavelet transform, puts forward a kind of new method identifying gradual change style seismic phases with background noise which is called fixed scale wavelet transform ratio, and presents application examples about simulation digital signal and actual seismic phases recording onsets identification.

  10. Low frequency modulation of jets in quasigeostrophic turbulence

    CERN Document Server

    Suhas, D L

    2016-01-01

    Quasigeostrophic turbulence on a beta-plane with a finite deformation radius is studied nu- merically, with particular emphasis on frequency and combined wavenumber-frequency do- main analyses. Under suitable conditions, simulations with small-scale random forcing and large-scale drag exhibit a spontaneous formation of multiple zonal jets. The first hint of wave-like features is seen in the distribution of kinetic energy as a function of frequency; specifically, for progressively larger deformation scales there are systematic departures in the form of isolated peaks (at progressively higher frequencies) from a power-law scaling. Con- comitantly, there is an inverse flux of kinetic energy in frequency space which extends to lower frequencies for smaller deformation scales. The identification of these peaks as Rossby waves is made possible by examining the energy spectrum in frequency-zonal wavenumber and frequency-meridional wavenumber diagrams. In fact, the modified Rhines scale turns out to be a useful measu...

  11. Novel time-frequency differential space-time modulation for multi-antenna OFDM systems

    Institute of Scientific and Technical Information of China (English)

    Tian Jifeng; Jiang Haining; Song Wentao; Luo Hanwen; Xu Youyun

    2006-01-01

    Differential space-time (DST) modulation has been proposed recently for multiple-antenna systems over Rayleigh fading channels, where neither the transmitter nor the receiver knows the fading coefficients. Among existing schemes, differential modulation is always performed in the time domain and suffers performance degradations in frequency-selective fading channels. In order to combat the fast time and frequency-selective fading, a novel time-frequency differential space-time (TF-DST) modulation scheme, which adopts differential modulation in both time and frequency domains, is proposed for multi-antenna orthogonal frequency division multiplexing (OFDM) system. A corresponding suboptimal yet low-complexity non-coherent detection approach is also proposed. Simulation results demonstrate that the propped system is robust for time and frequency-selective Rayleigh fading channels.

  12. Frequency selection module in composition the central station of reception and transmission multimedia information

    Directory of Open Access Journals (Sweden)

    G. A. Mirskikh

    2011-10-01

    Full Text Available The knot is incomposition the keystation of reception and transmission signals of ether television, radiosignals and multimedia information is presented in the article. The module of frequencyselection is intended for filtration and division of power of signal between eight users. Thecomplete set from sixteen modules of frequency selection is used In the central station. Thebasic frequency parameters of filters of intermediate-frequency and topology of microstripcoplanaricdivizor on the basis of double circular divizors are presented in the article

  13. Modulation Depth Based on Frequency-shift Characteristic of LiNbO3 Waveguide Electro-optic Intensity Modulator

    Institute of Scientific and Technical Information of China (English)

    Hui-juan ZHOU; Zhou MENG; Yi LIAO

    2010-01-01

    The modulation depth,defined according to practical mod-ulation results,which changes with the microwave power and its fre-quency,is significant for systems utilizing the frequency-shift charac-teristic of the LiNbO3 waveguide Electro-Optic Intensity Modulator (EOIM).By analyzing the impedance mismatch between the micro-wave source and the EOIM,the effective voltage applied to the RF port of the EOIM is deprived frcm the microwave power and its fre-quency.Associating with analyses of the phase velocity mismatch be-tween the microwave and the optical wave,the theoretical modulation depth has been obtained,which is verified by experimental results.We provide a method to choose the appropriate modulation depth to optimize the desired sideband through proper transmission bias far the system based an the frequency-shift characteristic of the EOIM.

  14. Comparisons between PW Doppler system and enhanced FM Doppler system

    DEFF Research Database (Denmark)

    Wilhjelm, Jens E.; Pedersen, P. C.

    1995-01-01

    This paper presents a new implementation of an echo-ranging FM Doppler system with improved performance, relative to the FM Doppler system reported previously. The use of long sweeps provides a significant reduction in peak to average power ratio compared to pulsed wave (PW) emission. A PW Doppler...... system exploits the direct relationship between arrival time of the received signal and range from the transducer. In the FM Doppler systems, a similar relationship exists in the spectral domain of the demodulated received signals, so that range is represented by frequency. Thus, a shift in location...... of moving scatterers between consecutive emissions corresponds to a frequency shift in the spectral signature. The improvement relative to the earlier version of the FM Doppler system is attained by utilizing cross-correlation of real spectra rather than of magnitude spectra for assessing flow velocity...

  15. Listening to FM and Chasing Meteors

    Science.gov (United States)

    Nedeljkovic, Sasa; Barth Netterfield, C.

    2005-08-01

    This poster will show how a digital radio spectrometer working between 50 and 150 MHz can be used for meteor detection. The spectrometer is connected to a small wide-frequency, wide-beam antenna. With better than 50 kHz spectral resolution, the instrument can resolve individual FM radio and TV stations. Existing commercial transmitters over the horizon will be used as transmitters for the forward scattering method of meteor detection. Given the frequency, directivity, and power of transmitters, and time evolution of the reflection, we can extract dynamical parameters of the meteor using only one receiver.

  16. A New High Rate Differential Space-Time-Frequency Modulation for MIMO-OFDM

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this paper, we propose a new differential space-time-frequency (DSTF) modulation for MIMO- OFDM system with four transmit-antennas and arbitrary receive-antennas, which can improve the transmission rate since it can adopt high order quadrature amplitude modulation (QAM) modulation. Our proposed DSTF scheme embeds some full diversity full rate (FDFR) quasi-orthogonal space-time codes (QOSTBC) with QAM modulation into the frequency intervals and adopts the differential modulation in both time and frequency domains. The simulation results demonstrate that the proposed DSTF scheme can improve transmission rate greatly. Compared with the conventional differential unitary space-time modulation (DUSTM), it can get better transmission performance in high transmission rate for MIMO-OFDM system.

  17. The potential characteristics analysis of probing signal with the quadratic frequency modulation

    Directory of Open Access Journals (Sweden)

    O. D. Mrachkovsky

    2012-12-01

    Full Text Available Introduction: Complex signals with the button ambiguity function can provide the distance and speed of target independent estimation. The signal with the symmetrical linear frequency modulation has this property in the class of signal with frequency modulation. Problem statement: To show that in the class of signals frequency-shift is signal with button ambiguity function. Such signal is a signal with the quadratic frequency intra-modulation. The potential characteristics research of signal with the quadratic frequency intra-modulation: The signal with quadratic frequency modulation and its properties are considered, analytic form of signal and its spectrum are shown, figures of amplitude spectra of signal are drawn, and figures of ambiguity diagram, cross-correlation functions and response ambiguity function in strong and weak fields are shown. The comparison of the signal with the quadratic frequency intra-modulation and the signal with the symmetrical linear frequency modulation are shown. The result of research is that the ambiguity function form of a signal with the quadratic frequency intra-modulation comes nearer to button in the strong correlation field and it has X – for min the weak correlation field. The autocorrelation function of the signal with the quadratic frequency intra-modulation has some constant level which decreases with signal base increasing. It is revealed that autocorrelation function of the signal has no side lobes. It improves resolution capability of a weak signal against the strong signal. The pedestal level of the autocorrelation function of this signal is a little lower than pedestal level of the autocorrelation function of the signal with the symmetrical linear frequency modulation. Properties of section of cross-correlation function to two peaks and effect of these properties are considered. Signals with the quadratic frequency intra-modulation are expedient for using in the sonar of submarines, because in

  18. Manufacturing Technology Study on Radio Frequency Power Modules Packaging Techniques.

    Science.gov (United States)

    1981-01-01

    transmitter, without adequate waterproofing procedures for the transducer cables. No detailed mapping was carried out, since no mechanical carriage was... cosmetic and does not affect hermetic seal of module. A.7 Final Electrical Test Method: Test performed on computer controlled automatic module test...dull gray due to reaction to salt environment. Discoloration is cosmetic only since solder coating is used to prevent oxidation of copper runs. Gold

  19. Automatic Classification of Normal and Cancer Lung CT Images Using Multiscale AM-FM Features.

    Science.gov (United States)

    Magdy, Eman; Zayed, Nourhan; Fakhr, Mahmoud

    2015-01-01

    Computer-aided diagnostic (CAD) systems provide fast and reliable diagnosis for medical images. In this paper, CAD system is proposed to analyze and automatically segment the lungs and classify each lung into normal or cancer. Using 70 different patients' lung CT dataset, Wiener filtering on the original CT images is applied firstly as a preprocessing step. Secondly, we combine histogram analysis with thresholding and morphological operations to segment the lung regions and extract each lung separately. Amplitude-Modulation Frequency-Modulation (AM-FM) method thirdly, has been used to extract features for ROIs. Then, the significant AM-FM features have been selected using Partial Least Squares Regression (PLSR) for classification step. Finally, K-nearest neighbour (KNN), support vector machine (SVM), naïve Bayes, and linear classifiers have been used with the selected AM-FM features. The performance of each classifier in terms of accuracy, sensitivity, and specificity is evaluated. The results indicate that our proposed CAD system succeeded to differentiate between normal and cancer lungs and achieved 95% accuracy in case of the linear classifier.

  20. Experimental Demonstration of Ideal Noise Shaping in Resonant Tunneling Delta-Sigma Modulator for High Resolution, Wide Band Analog-to-Digital Converters

    Science.gov (United States)

    Maezawa, Koichi; Sakou, Mario; Matsubara, Wataru; Mizutani, Takashi; Matsuzaki, Hideaki

    2006-04-01

    A ΔΣ modulator using a frequency modulation intermediate signal was demonstrated using a resonant tunneling logic gate called a monostable bistable transition logic element (MOBILE). This ΔΣ modulator is based on the nature of an FM signal and suitable for high-speed operation. Experiments using an InP-based MOBILE demonstrate good noise shaping characteristics. Moreover, the operation with a higher FM carrier frequency than the sampling frequency was demonstrated, showing equally good noise shaping performance. This makes the design of the voltage-controlled oscillator, which is a key component of the FM ΔΣ modulator, much easier. Consequently, an FM ΔΣ modulator using MOBILE is promising for high-resolution, wide-band analog-to-digital converters (ADCs).

  1. Program on application of communications satellites to educational development: Design of a 12 channel FM microwave receiver. [color television from communication satellites

    Science.gov (United States)

    Risch, C. O.; Rosenbaum, F. J.; Gregory, R. O.

    1974-01-01

    The design, fabrication, and performance of elements of a low cost FM microwave satellite ground station receiver is described. It is capable of accepting 12 contiguous color television equivalent bandwidth channels in the 11.72 to 12.2 GHz band. Each channel is 40 MHz wide and incorporates a 4 MHz guard band. The modulation format is wideband FM and the channels are frequency division multiplexed. Twelve independent CATV compatible baseband outputs are provided. The overall system specifications are first discussed, then consideration is given to the receiver subsystems and the signal branching network.

  2. Observations on auditory learning in amplitude- and frequency-modulation rate discrimination

    DEFF Research Database (Denmark)

    Hoffmann, Pablo F.

    2010-01-01

    . One of the key issues when designing such training systems is in the assessment of transfer of learning. In this study we present data on the learning of an auditory task involving sinusoidal amplitude- and frequency-modulated tones. Modulation rate discrimination thresholds were measured during pre......-training, training, a post-training stages. During training, listeners were divided into two groups; one group trained on amplitude-modulation rate discrimination and the other group trained on frequency-modulation rate discrimination. Results will be discussed in terms of their implications for training...

  3. Design-oriented analytic model of phase and frequency modulated optical links

    Science.gov (United States)

    Monsurrò, Pietro; Saitto, Antonio; Tommasino, Pasquale; Trifiletti, Alessandro; Vannucci, Antonello; Cimmino, Rosario F.

    2016-07-01

    An analytic design-oriented model of phase and frequency modulated microwave optical links has been developed. The models are suitable for design of broadband high dynamic range optical links for antenna remoting and optical beamforming, where noise and linearity of the subsystems are a concern Digital filter design techniques have been applied to the design of optical filters working as frequency discriminator, that are the bottleneck in terms of linearity for these systems. The models of frequency modulated, phase modulated, and coherent I/Q link have been used to compare performance of the different architectures in terms of linearity and SFDR.

  4. Spatial Frequency Modulates the Degree of Illusory Second Flash Perception.

    Science.gov (United States)

    Takeshima, Yasuhiro; Gyoba, Jiro

    2015-01-01

    When a brief single flash is presented simultaneously with two brief beeps, the number of presented flashes is often perceived as two. This phenomenon is referred to as the fission illusion. Several effects related to the fission illusion have been investigated using both psychophysical and neurophysiological methods. The present study examined the effects of spatial frequency on the fission illusion. At a low spatial frequency, transient channels respond preferably; conversely, sustained channels respond preferably at a high spatial frequency. Sustained channels differ in temporal properties from transient channels and are characterized by poor temporal resolution and slow-onset responses. In our previous study, visual stimuli presented at a slow processing speed were not conducive to the fission illusion. Therefore, we hypothesized that the fission illusion would not be difficult to observe when using high spatial frequencies. The results indicated that the degree of the perceived illusory second flash was reduced when spatial frequency was high as compared to when it was is low. Furthermore, according to signal detection theory, this difference between high and low spatial frequencies was not attributed to participants' response biases. Therefore, the fission illusion likely will not occur in conditions of slow processing speed and long response latencies in sustained channels, which respond preferably to high spatial frequency stimuli. Overall, the results indicated that the fission illusion was affected by temporal characteristics of lower-order sensory processing stages.

  5. Frequency Modulation of High-Speed Mill Chatter

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Mill chatter is a common phenomenon in the metal strip rolling process. Product defects caused by mill vibration were reported worldwide during last two decades, which is usually classified as torque vibration of the driving system with low frequencies and vertical vibration of the mill stand with comparative higher frequencies. The frequency range of the vertical vibration is wide (in general from more than 100 Hz to more than 1 000 Hz), and the vibration phenomena are very complex, even it is very diffic...

  6. Analytical and experimental comparisons between the frequency-modulated–frequency-shift measurement and the pulsed-wave–time-shift measurement Doppler systems

    DEFF Research Database (Denmark)

    Wilhjelm, Jens Erik; Pedersen, P. C.

    1996-01-01

    In previous publications, a new echo-ranging Doppler system based on transmission of repetitive coherent frequency modulated (FM) sinusoids in two different implementations was presented. One of these implementations, the Frequency Modulated - frequency shift measurement (FM-fsm) Doppler system...... is in this paper compared with its PW counterpart, the Pulsed Wave - time shift measurement (PW-tsm) Doppler system. When using transmitted PW and FM signals with a Gaussian envelope, the parallelism between the two systems can be stated explicitly, and comparison be made between the main performance indices...... for the two Doppler systems. The performance of the FM and PW Doppler systems is evaluated by means of numerical simulation and measurements of actual flow profiles. The results indicate that the two Doppler systems have very similar levels of performance....

  7. Investigation on nanoscale processes on the BaF{sub 2}(111) surface in various solutions by frequency modulation atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, Naritaka, E-mail: naritaka@mail.saitama-u.ac.jp [Division of Strategic Research and Development, Graduate School of Science and Engineering, Saitama University, Shimo-okubo 255, Sakura-ku, Saitama 338-8570 (Japan); Kawamura, Ryuzo [Department of Chemistry, Faculty of Science, Saitama University, Shimo-okubo 255, Sakura-ku, Saitama 338-8570 (Japan); Yoshikawa, Hiroshi Y.; Nakabayashi, Seiichiro [Division of Strategic Research and Development, Graduate School of Science and Engineering, Saitama University, Shimo-okubo 255, Sakura-ku, Saitama 338-8570 (Japan); Department of Chemistry, Faculty of Science, Saitama University, Shimo-okubo 255, Sakura-ku, Saitama 338-8570 (Japan)

    2016-06-07

    In this study, we have directly observed nanoscale processes that occur on BaF{sub 2}(111) surfaces in various solutions using liquid-environment frequency modulation atomic force microscopy (FM-AFM) with a true atomic resolution. In addition, to investigate atomic-scale mechanisms of crystal growth process of BaF{sub 2}, we determined a suitable solution for atomic-resolution FM-AFM imaging of the BaF{sub 2}(111) surface. For undersaturated solutions, the surface is roughened by barium hydroxo complexes in the case of high pH, whereas by dissolution and proton or water molecule adsorption throughout the surface in the case of low pH. On the other hand, for supersaturated solutions, the surface shows two-dimensional nucleation and growth (σ = 0.1) and three-dimensional crystal growth with tetrahedral structures (σ = 1), where σ is the degree of supersaturation. The atomic-resolution imaging of the BaF{sub 2}(111) surface has been demonstrated in potassium fluoride (KF) and the supersaturated (σ = 0.1 and 1) solutions, wherein atomically flat terraces are shown at least for about 30 min.

  8. Instantaneous frequency based newborn EEG seizure characterisation

    Science.gov (United States)

    Mesbah, Mostefa; O'Toole, John M.; Colditz, Paul B.; Boashash, Boualem

    2012-12-01

    The electroencephalogram (EEG), used to noninvasively monitor brain activity, remains the most reliable tool in the diagnosis of neonatal seizures. Due to their nonstationary and multi-component nature, newborn EEG seizures are better represented in the joint time-frequency domain than in either the time domain or the frequency domain. Characterising newborn EEG seizure nonstationarities helps to better understand their time-varying nature and, therefore, allow developing efficient signal processing methods for both modelling and seizure detection and classification. In this article, we used the instantaneous frequency (IF) extracted from a time-frequency distribution to characterise newborn EEG seizures. We fitted four frequency modulated (FM) models to the extracted IFs, namely a linear FM, a piecewise-linear FM, a sinusoidal FM, and a hyperbolic FM. Using a database of 30-s EEG seizure epochs acquired from 35 newborns, we were able to show that, depending on EEG channel, the sinusoidal and piecewise-linear FM models best fitted 80-98% of seizure epochs. To further characterise the EEG seizures, we calculated the mean frequency and frequency span of the extracted IFs. We showed that in the majority of the cases (>95%), the mean frequency resides in the 0.6-3 Hz band with a frequency span of 0.2-1 Hz. In terms of the frequency of occurrence of the four seizure models, the statistical analysis showed that there is no significant difference( p = 0.332) between the two hemispheres. The results also indicate that there is no significant differences between the two hemispheres in terms of the mean frequency ( p = 0.186) and the frequency span ( p = 0.302).

  9. Frequency Stepped Pulse Train Modulated Wind Sensing Lidar

    DEFF Research Database (Denmark)

    Olesen, Anders Sig; Pedersen, Anders Tegtmeier; Rottwitt, Karsten

    2011-01-01

    In this paper a wind sensing lidar utilizing a Frequency Stepped Pulse Train (FSPT) is demonstrated. One of the advantages in the FSTP lidar is that it enables direct measurement of wind speed as a function of distance from the lidar. Theoretically the FSPT lidar continuously produces measurements...... as is the case with a CW lidar, but at the same time with a spatial resolution, and without the range ambiguity originating from e.g. clouds. The FSPT lidar utilizes a frequency sweeping source for generation of the FSPT. The source generates a pulse train where each pulse has an optical carrier frequency...... of frequency shifts corresponding to a specific distance. The spatial resolution depends on the repetition rate of the pulses in the pulse train. Directional wind measurements are shown and compared to a CW lidar measurement. The carrier to noise ratio of the FSPT lidar compared to a CW lidar is discussed...

  10. Context-related frequency modulations of macaque motor cortical LFP beta oscillations.

    Science.gov (United States)

    Kilavik, Bjørg Elisabeth; Ponce-Alvarez, Adrián; Trachel, Romain; Confais, Joachim; Takerkart, Sylvain; Riehle, Alexa

    2012-09-01

    The local field potential (LFP) is a population measure, mainly reflecting local synaptic activity. Beta oscillations (12-40 Hz) occur in motor cortical LFPs, but their functional relevance remains controversial. Power modulation studies have related beta oscillations to a "resting" motor cortex, postural maintenance, attention, sensorimotor binding and planning. Frequency modulations were largely overlooked. We here describe context-related beta frequency modulations in motor cortical LFPs. Two monkeys performed a reaching task with 2 delays. The first delay demanded attention in time in expectation of the visual spatial cue, whereas the second delay involved visuomotor integration and movement preparation. The frequency in 2 beta bands (around 20 and 30 Hz) was systematically 2-5 Hz lower during cue expectancy than during visuomotor integration and preparation. Furthermore, the frequency was directionally selective during preparation, with about 3 Hz difference between preferred and nonpreferred directions. Direction decoding with frequency gave similar accuracy as with beta power, and decoding accuracy improved significantly when combining power and frequency, suggesting that frequency might provide an additional signal for brain-machine interfaces. In conclusion, multiple beta bands coexist in motor cortex, and frequency modulations within each band are as behaviorally meaningful as power modulations, reflecting the changing behavioral context and the movement direction during preparation.

  11. Narrow Wavelength, Frequency Modulated Source at 1.5? Wavelength Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA needs narrow linewidth lasers in the 1.5 or 2 micron wavelength regime for Lidar applications. The laser should be tunable by several nm and frequency modulated...

  12. A theoretical and experimental analysis of modulated laser fields and power spectra

    DEFF Research Database (Denmark)

    Olesen, Henning; Jacobsen, G.

    1982-01-01

    A general theoretical description of modulated laser fields and power spectra for a current modulated single-mode laser is derived, taking into account both the intensity and frequency modulation (IM and FM) of the emitted light. The theory relies on an explicit knowledge of the modulus as well...

  13. Timbral Sharpness and Modulations in Frequency and Amplitude: Implications for the Fusion of Musical Sounds.

    Science.gov (United States)

    Goad, Pamela Joy

    The fusion of musical voices is an important aspect of musical blend, or the mixing of individual sounds. Yet, little research has been done to explicitly determine the factors involved in fusion. In this study, the similarity of timbre and modulation were examined for their contribution to the fusion of sounds. It is hypothesized that similar timbres will fuse better than dissimilar timbres, and, voices with the same kind of modulation will fuse better than voices of different modulations. A perceptually-based measure, known as sharpness was investigated as a measure of timbre. The advantages of using sharpness are that it is based on hearing sensitivities and masking phenomena of inner ear processing. Five musical instrument families were digitally recorded in performances across a typical playing range at two extreme dynamic levels. Analyses reveal that sharpness is capable of uncovering subtle changes in timbre including those found in musical dynamics, instrument design, and performer-specific variations. While these analyses alone are insufficient to address fusion, preliminary calculations of timbral combinations indicate that sharpness has the potential to predict the fusion of sounds used in musical composition. Three experiments investigated the effects of modulation on the fusion of a harmonic major sixth interval. In the first experiment using frequency modulation, stimuli varied in deviation about a mean fundamental frequency and relative modulation phase between the two tones. Results showed smaller frequency deviations promoted fusion and relative phase differences had a minimal effect. In a second experiment using amplitude modulation, stimuli varied in deviation about a mean amplitude level and relative phase of modulation. Results showed smaller amplitude deviations promoted better fusion, but unlike frequency modulation, relative phase differences were also important. In a third experiment, frequency modulation, amplitude modulation and mixed

  14. Frequency Properties Research of Elevator Drive System with Direct Torque Control-Pulse with Modulation

    Directory of Open Access Journals (Sweden)

    A. S. Koval

    2008-01-01

    Full Text Available In the article problems of frequency properties research for electric drive system with direct torque control and pulse width modulator are described. The mathematical description of elevator is present. Simplified mathematical description of direct torque control - pulse width modulator electric drive system is shown. Transfer functions for torque and speed loops are determined. Logarithmic frequency characteristics are computed. Damping properties of elevator drive system are estimated.

  15. Radio Frequency Identification (RFID) in medical environment: Gaussian Derivative Frequency Modulation (GDFM) as a novel modulation technique with minimal interference properties.

    Science.gov (United States)

    Rieche, Marie; Komenský, Tomás; Husar, Peter

    2011-01-01

    Radio Frequency Identification (RFID) systems in healthcare facilitate the possibility of contact-free identification and tracking of patients, medical equipment and medication. Thereby, patient safety will be improved and costs as well as medication errors will be reduced considerably. However, the application of RFID and other wireless communication systems has the potential to cause harmful electromagnetic disturbances on sensitive medical devices. This risk mainly depends on the transmission power and the method of data communication. In this contribution we point out the reasons for such incidents and give proposals to overcome these problems. Therefore a novel modulation and transmission technique called Gaussian Derivative Frequency Modulation (GDFM) is developed. Moreover, we carry out measurements to show the inteference properties of different modulation schemes in comparison to our GDFM.

  16. Corticospinal interaction during isometric compensation for modulated forces with different frequencies

    Directory of Open Access Journals (Sweden)

    Maurer Christoph

    2010-12-01

    Full Text Available Abstract Background During isometric compensation of modulated low-level forces corticomuscular coherence (CMC has been shown to occur in high-beta or gamma-range. The influence of the frequency of force modulation on CMC has up to now remained unexplored. We addressed this question by investigating CMC, motor performance, and cortical spectral power during a visuomotor task in which subjects had to compensate a modulated force of 8% of the maximum voluntary contraction exerted on their right index finger. The effect of three frequencies of force modulation (0.6, 1.0 and 1.6 Hz was tested. EEG, EMG from first dorsal interosseus, hand flexor and extensor muscles, and finger position were recorded in eight right-handed women. Results Five subjects showed CMC in gamma- (28-45 Hz and three in beta-range (15-30 Hz. Beta- and gamma-range CMC and cortical motor spectral power were not modulated by the various frequencies. However, a sharp bilateral CMC peak at 1.6 Hz was observed, but only in the five gamma-range CMC subjects. The performance error increased linearly with the frequency. Conclusions Our findings suggest that the frequency of force modulation has no effect on the beta- and gamma-range CMC during isometric compensation for modulated forces at 8% MVC. The beta- and gamma-range CMC may be related to interindividual differences and possibly to strategy differences.

  17. Corticospinal interaction during isometric compensation for modulated forces with different frequencies.

    Science.gov (United States)

    Naranjo, José R; Wang, Xi; Schulte-Mönting, Jürgen; Huethe, Frank; Maurer, Christoph; Hepp-Reymond, Marie-Claude; Kristeva, Rumyana

    2010-12-31

    During isometric compensation of modulated low-level forces corticomuscular coherence (CMC) has been shown to occur in high-beta or gamma-range. The influence of the frequency of force modulation on CMC has up to now remained unexplored. We addressed this question by investigating CMC, motor performance, and cortical spectral power during a visuomotor task in which subjects had to compensate a modulated force of 8% of the maximum voluntary contraction exerted on their right index finger. The effect of three frequencies of force modulation (0.6, 1.0 and 1.6 Hz) was tested. EEG, EMG from first dorsal interosseus, hand flexor and extensor muscles, and finger position were recorded in eight right-handed women. Five subjects showed CMC in gamma- (28-45 Hz) and three in beta-range (15-30 Hz). Beta- and gamma-range CMC and cortical motor spectral power were not modulated by the various frequencies. However, a sharp bilateral CMC peak at 1.6 Hz was observed, but only in the five gamma-range CMC subjects. The performance error increased linearly with the frequency. Our findings suggest that the frequency of force modulation has no effect on the beta- and gamma-range CMC during isometric compensation for modulated forces at 8% MVC. The beta- and gamma-range CMC may be related to interindividual differences and possibly to strategy differences.

  18. Selective attention modulates human auditory brainstem responses: relative contributions of frequency and spatial cues.

    Science.gov (United States)

    Lehmann, Alexandre; Schönwiesner, Marc

    2014-01-01

    Selective attention is the mechanism that allows focusing one's attention on a particular stimulus while filtering out a range of other stimuli, for instance, on a single conversation in a noisy room. Attending to one sound source rather than another changes activity in the human auditory cortex, but it is unclear whether attention to different acoustic features, such as voice pitch and speaker location, modulates subcortical activity. Studies using a dichotic listening paradigm indicated that auditory brainstem processing may be modulated by the direction of attention. We investigated whether endogenous selective attention to one of two speech signals affects amplitude and phase locking in auditory brainstem responses when the signals were either discriminable by frequency content alone, or by frequency content and spatial location. Frequency-following responses to the speech sounds were significantly modulated in both conditions. The modulation was specific to the task-relevant frequency band. The effect was stronger when both frequency and spatial information were available. Patterns of response were variable between participants, and were correlated with psychophysical discriminability of the stimuli, suggesting that the modulation was biologically relevant. Our results demonstrate that auditory brainstem responses are susceptible to efferent modulation related to behavioral goals. Furthermore they suggest that mechanisms of selective attention actively shape activity at early subcortical processing stages according to task relevance and based on frequency and spatial cues.

  19. Selective attention modulates human auditory brainstem responses: relative contributions of frequency and spatial cues.

    Directory of Open Access Journals (Sweden)

    Alexandre Lehmann

    Full Text Available Selective attention is the mechanism that allows focusing one's attention on a particular stimulus while filtering out a range of other stimuli, for instance, on a single conversation in a noisy room. Attending to one sound source rather than another changes activity in the human auditory cortex, but it is unclear whether attention to different acoustic features, such as voice pitch and speaker location, modulates subcortical activity. Studies using a dichotic listening paradigm indicated that auditory brainstem processing may be modulated by the direction of attention. We investigated whether endogenous selective attention to one of two speech signals affects amplitude and phase locking in auditory brainstem responses when the signals were either discriminable by frequency content alone, or by frequency content and spatial location. Frequency-following responses to the speech sounds were significantly modulated in both conditions. The modulation was specific to the task-relevant frequency band. The effect was stronger when both frequency and spatial information were available. Patterns of response were variable between participants, and were correlated with psychophysical discriminability of the stimuli, suggesting that the modulation was biologically relevant. Our results demonstrate that auditory brainstem responses are susceptible to efferent modulation related to behavioral goals. Furthermore they suggest that mechanisms of selective attention actively shape activity at early subcortical processing stages according to task relevance and based on frequency and spatial cues.

  20. Increased Sensitivity of Magnetoelectric Sensors at Low Frequencies Using Magnetic Field Modulation

    Science.gov (United States)

    Petrie, Jonathan; Viehland, Dwight; Gray, David; Mandal, Sanjay; Sreenivasulu, Gollapudi; Srinivasan, Gopalan; Edelstein, Alan

    2012-02-01

    Magnetoelectric (ME) laminate sensors are vector magnetometers that can detect pT magnetic fields at 1 kHz, although sensitivity may be reduced at lower frequencies. These passive sensors consist of alternating layers of magnetostrictive and piezoelectric materials. A magnetic field causes the magnetostrictive layer to strain the piezoelectric material and create measurable charge. We have shownootnotetextTo be published in Journal of Applied Physics. that since the strain response is a nonlinear function of the bias field, sweeping the magnetic bias on the magnetostrictive layer can modulate the ME response and increase the operating frequency of the sensor. This upward shift lowers the 1/f noise and increases the signal amplitude if the new operating frequency is near a mechanical resonance mode of the sensor. Using this modulation technique, the low frequency sensitivity has been improved by more than an order of magnitude and we have achieved a detectivity of 7 pT/Hz at1 Hz. In addition to increasing the magnetic signal frequency, we can use magnetic modulation to increase the operating frequency of acoustic signals detected by these sensors. This occurs because the ME sensors are nonlinear devices. In these cases using magnetic field modulation, the signal appears as sidebands around the modulation frequency.

  1. Observations on auditory learning in amplitude- and frequency-modulation rate discrimination

    DEFF Research Database (Denmark)

    Hoffmann, Pablo F.

    2010-01-01

    Because amplitude- and frequency-modulated sounds can be the basis for the synthesis of many complex sounds, they can be good candidates in the design of training systems aiming at improving the acquisition of perceptual skills that can benefit from information provided via the auditory channel......-training, training, a post-training stages. During training, listeners were divided into two groups; one group trained on amplitude-modulation rate discrimination and the other group trained on frequency-modulation rate discrimination. Results will be discussed in terms of their implications for training...

  2. 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.

  3. Optimisation of frequency-modulated characteristics of output radiation in a lidar with Raman amplification

    Energy Technology Data Exchange (ETDEWEB)

    Grigorievsky, V I [V.A.Kotel' nikov Institute of Radio Engineering and Electronics, Fryazino branch, Russian Academy of Sciences, Fryazino, Moscow Region (Russian Federation); Tezadov, Ya A [IRE-Polus Research and Technology Association, Fryazino, Moscow Region (Russian Federation)

    2016-03-31

    The reported study is aimed at increasing the power in the transmission path of a lidar with Raman amplification for longpath sensing of methane by optimising the frequency-modulated characteristics of the output radiation. The pump current of the used distributed-feedback master laser was modulated by a linearfrequency signal with simultaneous application of a non-synchronous high-frequency signal. For such a modulation regime, the Raman amplifier provided the mean output power of 2.5 W at a wavelength of 1650 nm. The spectral broadening did not significantly decrease the lidar sensitivity at long paths. (lidars)

  4. Radio frequency path characterization for wide band quadrature amplitude modulation

    Energy Technology Data Exchange (ETDEWEB)

    Bracht, R.

    1998-12-31

    Remote, high speed, high explosive wave front monitoring requires very high bandwidth telemetry to allow transmission of diagnostic data before the explosion destroys the sensor system itself. The main motivation for this study is that no known existing implementation of this sort has been applied to realistic weapons environments. These facts have prompted the research and gathering of data that can be used to extrapolate towards finding the best modulation method for this application. In addition to research of similar existing analysis and testing operations, data was recently captured from a Joint Test Assembly (JTA) Air Launched Cruise Missile (ALCM) flight.

  5. Achilles tendinopathy modulates force frequency characteristics of eccentric exercise.

    Science.gov (United States)

    Grigg, Nicole L; Wearing, Scott C; O'Toole, John M; Smeathers, James E

    2013-03-01

    Previous research has demonstrated that ground reaction force (GRF) recorded during eccentric ankle exercise is characterized by greater power in the 8- to 12-Hz bandwidth when compared with that recorded during concentric ankle exercise. Subsequently, it was suggested that vibrations in this bandwidth may underpin the beneficial effect of eccentric loading in tendon repair. However, this observation has been made only in individuals without Achilles tendinopathy. This research compared the force frequency characteristics of eccentric and concentric exercises in individuals with and without Achilles tendinopathy. Eleven male adults with unilateral midportion Achilles tendinopathy and nine control male adults without tendinopathy participated in the research. Kinematics and GRF were recorded while the participants performed a common eccentric rehabilitation exercise protocol and a concentric equivalent. Ankle joint kinematics and the frequency power spectrum of the resultant GRF were calculated. Eccentric exercise was characterized by a significantly greater proportion of spectral power between 4.5 and 11.5 Hz when compared with concentric exercise. There were no significant differences between limbs in the force frequency characteristics of concentric exercise. Eccentric exercise, in contrast, was defined by a shift in the power spectrum of the symptomatic limb, resulting in a second spectral peak at 9 Hz, rather than 10 Hz in the control limb. Compared with healthy tendon, Achilles tendinopathy was characterized by lower frequency vibrations during eccentric rehabilitation exercises. This finding may be associated with changes in neuromuscular activation and tendon stiffness that have been shown to occur with tendinopathy and provides a possible rationale for the previous observation of a different biochemical response to eccentric exercise in healthy and injured Achilles tendons.

  6. Energy dissipation measurements in frequency-modulated scanning probe microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Proksch, Roger [Asylum Research, Santa Barbara, CA (United States); Kalinin, Sergei V [Oak Ridge National Laboratory, Oak Ridge, TN (United States)

    2010-11-12

    Local dissipation measurements by scanning probe microscopy have attracted increasing interest as a method for probing energy losses and hysteretic phenomena due to magnetic, electrical, and structural transformations at the tip-surface junction. One challenge of this technique is the lack of a standard for ensuring quantification of the dissipation signal. In the following, we explored magnetic dissipation imaging of an yttrium-iron garnet (YIG) sample, using a number of similar but not identical cantilever probes. Typical frequency-dependent dispersion of the actuator-probe assembly commonly approached {+-} 1 part in 10{sup 3} Hz{sup -1}, much larger than the minimum detectable level of {+-} 1 part in 10{sup 5} Hz{sup -1}. This cantilever-dependent behavior results in a strong crosstalk between the conservative (frequency) and dissipative channels. This crosstalk was very apparent in the YIG dissipation images and in fact should be an inherent feature of single-frequency heterodyne detection schemes. It may also be a common effect in other dissipation imaging, even down to the atomic level, and in particular may be a significant issue when there are correlations between the conservative and dissipative components. On the other hand, we present a simple method for correcting for this effect. This correction technique resulted in self-consistent results for the YIG dissipation measurements and would presumably be effective for other systems as well.

  7. Effect of spectral shaping on defect detection in frequency modulated thermal wave imaging

    Science.gov (United States)

    Dua, Geetika; Mulaveesala, Ravibabu; Siddique, Juned A.

    2015-02-01

    This manuscript highlights a novel data processing approach for active infrared non-destructive testing and evaluation of carbon fibre reinforced polymers (CFRP). This is accomplished by performing spectral reshaping on a captured pre-processed linear frequency modulated thermal profile over the specimen. Results obtained from the Gaussian windowed frequency modulated thermal wave imaging (GWFMTWI) clearly shows better detection capabilities with improved test resolution and sensitivity. Further multi-transform techniques have been introduced both in time and frequency in order to test subsurface defect capabilities of the proposed approach.

  8. Operation Mode on Pulse Modulation in Atmospheric Radio Frequency Glow Discharges

    Science.gov (United States)

    Zhang, Jie; Guo, Ying; Huang, Xiaojiang; Zhang, Jing; Shi, Jianjun

    2016-10-01

    The discharge operation regime of pulse modulated atmospheric radio frequency (RF) glow discharge in helium is investigated on the duty cycle and frequency of modulation pulses. The characteristics of radio frequency discharge burst in terms of breakdown voltage, alpha(α)-gamma(γ) mode transition voltage and current are demonstrated by the discharge current voltage characteristics. The minimum breakdown voltage of RF discharge burst was obtained at the duty cycle of 20% and frequency of 400 kHz, respectively. The α-γ mode transition of RF discharge burst occurs at higher voltage and current by reducing the duty cycle and elevating the modulation frequency before the RF discharge burst evolving into the ignition phase, in which the RF discharge burst can operate stably in the γ mode. It proposes that the intensity and stability of RF discharge burst can be improved by manipulating the duty cycle and modulation frequency in pulse modulated atmospheric RF glow discharge. supported by National Natural Science Foundation of China (Nos. 11475043 and 11375042)

  9. Direct RF modulation transmitter, sampling clock frequency setting method for direct RF modulation transmitter

    NARCIS (Netherlands)

    Fukuda, Shuichi; Nauta, Bram

    2013-01-01

    PROBLEM TO BE SOLVED: To provide a direct RF modulation transmitter capable of satisfying a radiation level regulation even without providing a SAW filter. SOLUTION: A direct RF modulation transmitter includes: digital/RF converters 105, 106 to which an I digital baseband signal, a Q digital baseb

  10. Effect of Phase Shifted Frequency Modulation on Two Level Atom-Field Interaction

    Institute of Scientific and Technical Information of China (English)

    K.V. Priyesh; Ramesh Babu Thayyullathil

    2012-01-01

    We have studied the effect of phase shifted frequency modulation on two level atom with field interaction using Jaynes-Cummings model. Here the frequency of the interacting field is sinusoidally varying with time with a constant phase. Due to the presence of phase in the frequency modulation, the variation of population inversion with time is different from the standard case. There are no exact collapses and revivals in the variation of population inversion but it oscillates sinusoidally with time. In coherent field atom interaction the population inversion behaves as in the case of Fock state atom interaction, when frequency modulation with a non zero phase is applied. The study done with squeezed field has shown the same behavior of the population inversion.

  11. Frequency-specific modulation of population-level frequency tuning in human auditory cortex

    Directory of Open Access Journals (Sweden)

    Roberts Larry E

    2009-01-01

    Full Text Available Abstract Background Under natural circumstances, attention plays an important role in extracting relevant auditory signals from simultaneously present, irrelevant noises. Excitatory and inhibitory neural activity, enhanced by attentional processes, seems to sharpen frequency tuning, contributing to improved auditory performance especially in noisy environments. In the present study, we investigated auditory magnetic fields in humans that were evoked by pure tones embedded in band-eliminated noises during two different stimulus sequencing conditions (constant vs. random under auditory focused attention by means of magnetoencephalography (MEG. Results In total, we used identical auditory stimuli between conditions, but presented them in a different order, thereby manipulating the neural processing and the auditory performance of the listeners. Constant stimulus sequencing blocks were characterized by the simultaneous presentation of pure tones of identical frequency with band-eliminated noises, whereas random sequencing blocks were characterized by the simultaneous presentation of pure tones of random frequencies and band-eliminated noises. We demonstrated that auditory evoked neural responses were larger in the constant sequencing compared to the random sequencing condition, particularly when the simultaneously presented noises contained narrow stop-bands. Conclusion The present study confirmed that population-level frequency tuning in human auditory cortex can be sharpened in a frequency-specific manner. This frequency-specific sharpening may contribute to improved auditory performance during detection and processing of relevant sound inputs characterized by specific frequency distributions in noisy environments.

  12. Detecting Fleeting MRI Signals with Frequency-Modulated Pulses

    Science.gov (United States)

    Kobayashi, Naoharu; Idiyatullin, Djaudat; Corum, Curtis; Moeller, Steen; Chamberlain, Ryan; O'Connell, Robert; Nixdorf, Donald R.; Garwood, Michael

    2012-01-01

    We describe a fundamentally different approach to MRI referred to as SWIFT (sweep imaging with Fourier transformation). SWIFT exploits time-shared RF excitation and signal acquisition, allowing capture of signal from spins with extremely short transverse relaxation time, T2*. The MR signal is acquired in gaps inserted into a broadband frequency-swept excitation pulse, which results in acquisition delays of only 1 – 2 microseconds. In SWIFT, 3D k-space is sampled in a radial manner, whereby one projection of the object is acquired in the gaps of each frequency-swept pulse, allowing a repetition time (TR) on the order of the pulse length (typically 1 – 3 milliseconds). Since the orientation of consecutive projections varies in a smooth manner (i.e., only small increments in the values of the x, y, z gradients occur from view to view), SWIFT scanning is close to inaudible and is insensitive to gradient timing errors and eddy currents. SWIFT images can be acquired in scan times similar to and sometimes faster than conventional 3D gradient echo techniques. With its ability to capture signals from ultrashort T2* spins, SWIFT promises to expand the role of MRI in areas of research where MRI previously played no or negligible role. In this article, we show wood and tooth images obtained with SWIFT as examples of materials with ultrashort T2*. Early experience suggests SWIFT can play a role in materials science and porous media research. PMID:22661791

  13. 助听器无线调频系统临床应用研究%The study on the clinical application of hearing aids FM combination system

    Institute of Scientific and Technical Information of China (English)

    陈振声; 陈曦

    2006-01-01

    目的 观察助听器无线调频系统(hearing aid-frequency modulated,HA-FM)对于助听器听力补偿效果的影响.方法 在不同的声音环境下,分别采用麦克风(microphone,M)、无线调频(frequencymodulated,FM),无线调频+麦克风(frequency modulated+microphone,FM+M)三种输入方式,观察HA-FM使用者的言语听辨率和言语交流变化.结果 在安静环境下,近距离交流时,HA-FM的不同输入方式对言语听辨没有影响,在嘈杂环境下或远距离交流时,FM输入方式的听辨率几乎不受影响,M,FM+M的听辨率则明显下降.结论 在复杂的声音环境中,HA-FM是一种非常有用的助听辅助设备.

  14. Task-induced frequency modulation features for brain-computer interfacing

    Science.gov (United States)

    Jayaram, Vinay; Hohmann, Matthias; Just, Jennifer; Schölkopf, Bernhard; Grosse-Wentrup, Moritz

    2017-10-01

    Objective. Task-induced amplitude modulation of neural oscillations is routinely used in brain-computer interfaces (BCIs) for decoding subjects’ intents, and underlies some of the most robust and common methods in the field, such as common spatial patterns and Riemannian geometry. While there has been some interest in phase-related features for classification, both techniques usually presuppose that the frequencies of neural oscillations remain stable across various tasks. We investigate here whether features based on task-induced modulation of the frequency of neural oscillations enable decoding of subjects’ intents with an accuracy comparable to task-induced amplitude modulation. Approach. We compare cross-validated classification accuracies using the amplitude and frequency modulated features, as well as a joint feature space, across subjects in various paradigms and pre-processing conditions. We show results with a motor imagery task, a cognitive task, and also preliminary results in patients with amyotrophic lateral sclerosis (ALS), as well as using common spatial patterns and Laplacian filtering. Main results. The frequency features alone do not significantly out-perform traditional amplitude modulation features, and in some cases perform significantly worse. However, across both tasks and pre-processing in healthy subjects the joint space significantly out-performs either the frequency or amplitude features alone. This result only does not hold for ALS patients, for whom the dataset is of insufficient size to draw any statistically significant conclusions. Significance. Task-induced frequency modulation is robust and straight forward to compute, and increases performance when added to standard amplitude modulation features across paradigms. This allows more information to be extracted from the EEG signal cheaply and can be used throughout the field of BCIs.

  15. 基于 FM 的无线扩声系统%Wireless sound reinforcement system based on LabVIEW

    Institute of Scientific and Technical Information of China (English)

    巩学芳; 宋晓梅; 霍小波; 李楠

    2014-01-01

    In response to the demand of sound reinforcement system used in the classroom ,conference room and other places ,wireless sound reinforcement system based on LabVIEW is proposed .The system includes FM transceiver modules and graphical user interface (GUI) software .The FM transceiver mod‐ule implements voice signal wireless transceiver by using C8051F340 MCU to control RDA5820 ,which gets the operating frequency via USB from a PC and sends voice data ;the GUI which is realized by Lab‐VIEW software can modify FM transceiver frequency by USB ,and the acquired voice data can be ampli‐fied and played .The system is integrated designed of transceiver module to and implement FM voice sig‐nal wireless transceiver ,which can automatically switch the transceiver mode .The experiments show that the system is reasonable and feasible .%针对课堂教学、室内会议等对扩声系统的需求,提出了一种基于FM 的无线扩声系统.该系统包括FM 收发模块和图形用户界面(GUI)软件.FM 收发模块采用C8051F340单片机控制RDA5820实现对语音信号的无线收发,同时通过USB从PC机获取工作频率并发送语音数据;用LabVIEW实现的GUI软件可通过USB修改FM 收发频率,并将获取的语音数据进行扩声播放.该系统收发模块采用一体设计,实现语音的FM 无线收发,可自动切换收发工作模式,实验表明该系统方案合理可行.

  16. Development of a frequency-modulated ultrasonic sensor inspired by bat echolocation

    Science.gov (United States)

    Kepa, Krzysztof; Abaid, Nicole

    2015-03-01

    Bats have evolved to sense using ultrasonic signals with a variety of different frequency signatures which interact with their environment. Among these signals, those with time-varying frequencies may enable the animals to gather more complex information for obstacle avoidance and target tracking. Taking inspiration from this system, we present the development of a sonar sensor capable of generating frequency-modulated ultrasonic signals. The device is based on a miniature mobile computer, with on board data capture and processing capabilities, which is designed for eventual autonomous operation in a robotic swarm. The hardware and software components of the sensor are detailed, as well their integration. Preliminary results for target detection using both frequency-modulated and constant frequency signals are discussed.

  17. Trimming algorithm of frequency modulation for CIAE-230 MeV proton superconducting synchrocyclotron model cavity

    Science.gov (United States)

    Li, Pengzhan; Zhang, Tianjue; Ji, Bin; Hou, Shigang; Guo, Juanjuan; Yin, Meng; Xing, Jiansheng; Lv, Yinlong; Guan, Fengping; Lin, Jun

    2017-01-01

    A new project, the 230 MeV proton superconducting synchrocyclotron for cancer therapy, was proposed at CIAE in 2013. A model cavity is designed to verify the frequency modulation trimming algorithm featuring a half-wave structure and eight sets of rotating blades for 1 kHz frequency modulation. Based on the electromagnetic (EM) field distribution analysis of the model cavity, the variable capacitor works as a function of time and the frequency can be written in Maclaurin series. Curve fitting is applied for theoretical frequency and original simulation frequency. The second-order fitting excels at the approximation given its minimum variance. Constant equivalent inductance is considered as an important condition in the calculation. The equivalent parameters of theoretical frequency can be achieved through this conversion. Then the trimming formula for rotor blade outer radius is found by discretization in time domain. Simulation verification has been performed and the results show that the calculation radius with minus 0.012 m yields an acceptable result. The trimming amendment in the time range of 0.328-0.4 ms helps to reduce the frequency error to 0.69% in Simulation C with an increment of 0.075 mm/0.001 ms, which is half of the error in Simulation A (constant radius in 0.328-0.4 ms). The verification confirms the feasibility of the trimming algorithm for synchrocyclotron frequency modulation.

  18. Modulation of EMG power spectrum frequency during motor imagery.

    Science.gov (United States)

    Lebon, F; Rouffet, D; Collet, C; Guillot, A

    2008-04-25

    To provide evidence that motor imagery (MI) is accompanied by improvement of intramuscular conduction velocity (CV), we investigated surface electromyographic (EMG) activity of 3 muscles during the elbow flexion/extension. Thirty right-handed participants were asked to lift or to imagine lifting a weighted dumbbell under 3 types of muscular contractions, i.e. concentric, isometric and eccentric, taken as independent variables. The EMG activity of the agonist (long and short heads of biceps brachii) and the antagonist (long portion of triceps brachii) muscles was recorded and processed to determine the median frequency (MF) of EMG power spectrum as dependant variable. The MF was significantly higher during the MI sessions than during the resting condition while the participants remained strictly motionless. Moreover, the MF during imagined concentric contraction was significantly higher than during the eccentric. Thus, the MF variation was correlated to the type of contraction the muscle produced. During MI, the EMG patterns corresponding to each type of muscle contraction remained comparable to those observed during actual movement. In conclusion, specific motor programming is hypothesized to be performed as a function of muscle contraction type during MI.

  19. Theoretical optimal modulation frequencies for scattering parameter estimation and ballistic photon filtering in diffusive media

    CERN Document Server

    Panigrahi, Swapnesh; Ramachandran, Hema; Alouini, Mehdi

    2016-01-01

    The efficiency of using intensity modulated light for estimation of scattering properties of a turbid medium and for ballistic photon discrimination is theoretically quantified in this article. Using the diffusion model for modulated photon transport and considering a noisy quadrature demodulation scheme, the minimum-variance bounds on estimation of parameters of interest are analytically derived and analyzed. The existence of a variance-minimizing optimal modulation frequency is shown and its evolution with the properties of the intervening medium is derived and studied. Furthermore, a metric is defined to quantify the efficiency of ballistic photon filtering which may be sought when imaging through turbid media. The analytical derivation of this metric shows that the minimum modulation frequency required to attain significant ballistic discrimination depends only on the reduced scattering coefficient of the medium in a linear fashion for a highly scattering medium.

  20. Theoretical optimal modulation frequencies for scattering parameter estimation and ballistic photon filtering in diffusing media.

    Science.gov (United States)

    Panigrahi, Swapnesh; Fade, Julien; Ramachandran, Hema; Alouini, Mehdi

    2016-07-11

    The efficiency of using intensity modulated light for the estimation of scattering properties of a turbid medium and for ballistic photon discrimination is theoretically quantified in this article. Using the diffusion model for modulated photon transport and considering a noisy quadrature demodulation scheme, the minimum-variance bounds on estimation of parameters of interest are analytically derived and analyzed. The existence of a variance-minimizing optimal modulation frequency is shown and its evolution with the properties of the intervening medium is derived and studied. Furthermore, a metric is defined to quantify the efficiency of ballistic photon filtering which may be sought when imaging through turbid media. The analytical derivation of this metric shows that the minimum modulation frequency required to attain significant ballistic discrimination depends only on the reduced scattering coefficient of the medium in a linear fashion for a highly scattering medium.

  1. High-speed switching of biphoton delays through electro-optic pump frequency modulation

    Directory of Open Access Journals (Sweden)

    Ogaga D. Odele

    2017-01-01

    Full Text Available The realization of high-speed tunable delay control has received significant attention in the scene of classical photonics. In quantum optics, however, such rapid delay control systems for entangled photons have remained undeveloped. Here for the first time, we demonstrate rapid (2.5 MHz modulation of signal-idler arrival times through electro-optic pump frequency modulation. Our technique applies the quantum phenomenon of nonlocal dispersion cancellation along with pump frequency tuning to control the relative delay between photon pairs. Chirped fiber Bragg gratings are employed to provide large amounts of dispersion which result in biphoton delays exceeding 30 ns. This rapid delay modulation scheme could be useful for on-demand single-photon distribution in addition to quantum versions of pulse position modulation.

  2. High-Frequency Properties of Embedded Passives and Thermal Resistance in Organic Substrates for RF Module

    Directory of Open Access Journals (Sweden)

    Yusuke Kondo

    2010-01-01

    Full Text Available Radio Frequency (RF modules have been miniaturized to meet the demand for smaller and more enhanced handsets for wireless applications such as cellular phones. However, area for passive devices used in RF modules has made further miniaturization difficult. Passives embedded in substrates are now being studied intensively. In addition, circuit simulation technology has been developed that enables efficient designing of RF module circuits. Circuit designers, however, have limited database of organic substrates and embedded passives. Further, optimized thermal designs are required to prevent thermal resistance increase due to miniaturization of substrates. In this paper, we describe the high-frequency properties of the capacitors embedded in the organic substrates and present the equivalent circuit models of the embedded capacitors. We also present the thermal design of organic substrates applicable to RF modules.

  3. Control of Decoherence and Relaxation by Frequency Modulation of Heat Bath

    CERN Document Server

    Agarwal, G S

    2000-01-01

    We demonstrate in a very general fashion, considerable slowing down of decoherence and relaxation by fast frequency modulation of the system heat bath coupling. The slowing occurs as the decoherence rates are now determined by the spectral components of bath correlations which are shifted due to fast modulation. We present several examples including the slowing down of the heating of a trapped ion, where the system - bath interaction is not necessarily Markovian.

  4. Best Frequency for Temperature Modulation of Tin Oxide Gas Sensor for Chemical Vapor Identification

    OpenAIRE

    R Chutia; Bhuyan, M.

    2014-01-01

    In this paper, we describe a method of optimum temperature modulation of metal oxide semiconductor (MOS) based gas sensor, operated in dynamic temperature measurement for identification of gas. The volatile organic compound (VOC) sample space consists of fourteen laboratory chemicals sampled at various concentration. We have used eleven number of gas sensors, manufactured by Figaro sensors, Japan. The heater of the sensors were modulated with sawtooth heating waveform of different frequency. ...

  5. Corticofugal modulation of frequency tuning of inferior collicular neurons in big brown bat, Eptesicus fuscus

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In order to explore the possible mechanism of corticofugal modulation of excitatory frequency tuning curves (EFTCs) of midbrain neurons, we examined the change of sharpness, frequency-intensity response area, minimum threshold of both EFTCs and inhibitory frequency tuning curves (IFTCs) of inferior collicular neurons during corticofugal modulation using two-tone inhibition paradigm and micro-electrical stimulation technique. Our data showed that corticofugal inhibition increased sharpness, minimum threshold, and decreased the frequency-intensity response area of EFTCs, at the same time it decreased the sharpness, minimum threshold but increased the frequency-intensity response area of IFTCs. The opposite results were observed for EFTCs and IFTCs of corticofugally facilitated inferior collicular neurons. During corticofugal inhibition, the per-cent change of frequency-intensity response area of EFTCs had significant correlation with the percent change of that of IFTCs. These data suggest that cortical neurons are likely to improve frequency information processing of inferior col-licular neurons by modulation of IFTCs.

  6. Single-Bit All Digital Frequency Synthesis Using Homodyne Sigma-Delta Modulation.

    Science.gov (United States)

    Sotiriadis, Paul

    2016-10-05

    All-digital frequency synthesis using band-pass sigma-delta modulation to achieve spectrally clean single-bit output is presented and mathematically analyzed resulting in a complete model to predict stability and output spectrum. The quadrature homodyne filter architecture is introduced resulting in efficient implementations of carrier-frequency centred bandpass filters for the modulator. A multiplier-less version of the quadrature homodyne filter architecture is also introduced to reduce complexity maintaining clean in-band spectrum. MATLAB and SIMULINK simulation results present the potential capabilities of the synthesizer architectures and validate the accuracy of the developed theoretical framework.

  7. Time-of-flight detection of ultra-cold atoms using resonant frequency modulation imaging.

    Science.gov (United States)

    Hardman, K S; Wigley, P B; Everitt, P J; Manju, P; Kuhn, C C N; Robins, N P

    2016-06-01

    Resonant frequency modulation imaging is used to detect free falling ultra-cold atoms. A theoretical comparison of fluorescence imaging (FI) and frequency modulation imaging (FMI) is made, indicating that for low optical depth clouds, FMI accomplished a higher signal-to-noise ratio under conditions necessary for a 200 μm spatially resolved atom interferometer. A 750 ms time-of-flight measurement reveals near atom shot-noise limited number measurements of 2×106 Bose-condensed Rb87 atoms. The detection system is applied to high precision spinor BEC based atom interferometer.

  8. Involuntary human hand movements due to FM radio waves in a moving van.

    Science.gov (United States)

    Huttunen, P; Savinainen, A; Hänninen, Osmo; Myllylä, R

    2011-06-01

    Finland TRACT Involuntary movements of hands in a moving van on a public road were studied to clarify the possible role of frequency modulated radio waves on driving. The signals were measured in a direct 2 km test segment of an international road during repeated drives to both directions. Test subjects (n=4) had an ability to sense radio frequency field intensity variations of the environment. They were sitting in a minivan with arm movement detectors in their hands. A potentiometer was used to register the hand movements to a computer which simultaneously collected data on the amplitude of the RF signal of the local FM tower 30 km distance at a frequency of about 100 MHz. Involuntary hand movements of the test subjects correlated with electromagnetic field, i.e. FM radio wave intensity measured. They reacted also on the place of a geomagnetic anomaly crossing the road, which was found on the basis of these recordings and confirmed by the public geological maps of the area.In conclusion, RF irradiation seems to affect the human hand reflexes of sensitive persons in a moving van along a normal public road which may have significance in traffic safety.

  9. A low-cost, tunable laser lock without laser frequency modulation

    Science.gov (United States)

    Shea, Margaret E.; Baker, Paul M.; Gauthier, Daniel J.

    2015-05-01

    Many experiments in optical physics require laser frequency stabilization. This can be achieved by locking to an atomic reference using saturated absorption spectroscopy. Often, the laser frequency is modulated and phase sensitive detection used. This method, while well-proven and robust, relies on expensive components, can introduce an undesirable frequency modulation into the laser, and is not easily frequency tuned. Here, we report a simple locking scheme similar to those implemented previously. We modulate the atomic resonances in a saturated absorption setup with an AC magnetic field created by a single solenoid. The same coil applies a DC field that allows tuning of the lock point. We use an auto-balanced detector to make our scheme more robust against laser power fluctuations and stray magnetic fields. The coil, its driver, and the detector are home-built with simple, cheap components. Our technique is low-cost, simple to setup, tunable, introduces no laser frequency modulation, and only requires one laser. We gratefully acknowledge the financial support of the NSF through Grant # PHY-1206040.

  10. Frequency quadrupling optoelectronic oscillator using a single polarization modulator in a Sagnac loop

    Science.gov (United States)

    Wang, Wen Ting; Li, Wei; Zhu, Ning Hua

    2014-05-01

    We propose and demonstrate a novel and cost efficient method to generating a frequency quadrupling optoelectronic oscillator (OEO) using a single polarization modulator (PolM) in a Sagnac loop. The OEO loop and the Sagnac loop share the same PolM. In the OEO loop, the PolM is used to generate the fundamental microwave signal. In the Sagnac loop, the joint use of the PolM, a polarization controller (PC), and a polarization beam splitter (PBS) is equivalent to an intensity modulator. The odd order sidebands of the modulated signal are suppressed by biasing the equivalent intensity modulator at the maximum transmission point. Moreover, the undesired optical carrier is also eliminated by bidirectional use of the PolM. As a result, only the two second order sidebands are left. The beating between the two second order sidebands in a photodetector (PD) generates a microwave signal at the frequency corresponding to four times of the fundamental tone. A frequency quadrupling microwave signal at the frequency of 39.74 GHz with a phase noise of -100.14 dBc/Hz at 10 kHz frequency offset was experimentally generated.

  11. Absolute frequency references at 1529 nm and 1560 nm using modulation transfer spectroscopy

    CERN Document Server

    de Escobar, Y Natali Martinez; Coop, Simon; Vanderbruggen, Thomas; Kaczmarek, Krzysztof T; Mitchell, Morgan W

    2015-01-01

    We demonstrate a double optical frequency reference (1529 nm and 1560 nm) for the telecom C-band using $^{87}$Rb modulation transfer spectroscopy. The two reference frequencies are defined by the 5S$_{1/2} F=2 \\rightarrow $ 5P$_{3/2} F'=3$ two-level and 5S$_{1/2} F=2 \\rightarrow $ 5P$_{3/2} F'=3 \\rightarrow $ 4D$_{5/2} F"=4$ ladder transitions. We examine the sensitivity of the frequency stabilization to probe power and magnetic field fluctuations, calculate its frequency shift due to residual amplitude modulation, and estimate its shift due to gas collisions. The short-term Allan deviation was estimated from the error signal slope for the two transitions. Our scheme provides a simple and high performing system for references at these important wavelengths. We estimate an absolute accuracy of $\\sim$ 1 kHz is realistic.

  12. Digital modulation classification using multi-layer perceptron and time-frequency features

    Institute of Scientific and Technical Information of China (English)

    Yuan Ye; Mei Wenbo

    2007-01-01

    Considering that real communication signals corrupted by noise are generally nonstationary, and time-frequency distributions are especially suitable for the analysis of nonstationary signals, time-frequency distributions are introduced for the modulation classification of communication signals.The extracted time-frequency features have good classification information, and they are insensitive to signal to noise ratio (SNR) variation.According to good classification by the correct rate of a neural network classifier, a multilayer perceptron (MLP) classifier with better generalization, as well as, addition of time-frequency features set for classifying six different modulation types has been proposed.Computer simulations show that the MLP classifier outperforms the decision-theoretic classifier at low SNRs, and the classification experiments for real MPSK signals verify engineering significance of the MLP classifier.

  13. Bi-Frequency Modulated Quasi-Resonant Converters: Theory and Applications

    Science.gov (United States)

    Zhang, Yuefeng

    1995-01-01

    To avoid the variable frequency operation of quasi -resonant converters, many soft-switching PWM converters have been proposed, all of them require an auxiliary switch, which will increase the cost and complexity of the power supply system. In this thesis, a new kind of technique for quasi -resonant converters has been proposed, which is called the bi-frequency modulation technique. By operating the quasi-resonant converters at two switching frequencies, this technique enables quasi-resonant converters to achieve the soft-switching, at fixed switching frequencies, without an auxiliary switch. The steady-state analysis of four commonly used quasi-resonant converters, namely, ZVS buck, ZCS buck, ZVS boost, and ZCS boost converter has been presented. Using the concepts of equivalent sources, equivalent sinks, and resonant tank, the large signal models of these four quasi -resonant converters were developed. Based on these models, the steady-state control characteristics of BFM ZVS buck, BFM ZCS buck, BFM ZVS boost, and BFM ZCS boost converter have been derived. The functional block and design consideration of the bi-frequency controller were presented, and one of the implementations of the bi-frequency controller was given. A complete design example has been presented. Both computer simulations and experimental results have verified that the bi-frequency modulated quasi-resonant converters can achieve soft-switching, at fixed switching frequencies, without an auxiliary switch. One of the application of bi-frequency modulation technique is for EMI reduction. The basic principle of using BFM technique for EMI reduction was introduced. Based on the spectral analysis, the EMI performances of the PWM, variable-frequency, and bi-frequency modulated control signals was evaluated, and the BFM control signals show the lowest EMI emission. The bi-frequency modulated technique has also been applied to the power factor correction. A BFM zero -current switching boost converter has

  14. One-dimensional hydrogen in low-frequency radiation: Frequency-modulated hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Nayfeh, M.H.; Humm, D.C.; Peercy, M. (Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801 (US))

    1989-10-01

    We investigate the effect of intense, low-frequency fields on the structure of atomic hydrogen (prepared in the presence of an external dc electric field). The em field (of amplitude {ital E}{sub 0} and frequency {omega}) interacts with a low-lying ({ital n} in the range of 2--7) two-level system of one-dimensional'' hydrogen (transition frequency {omega}{sub 0}=(N+1){omega} and transition dipole moment {mu}). The field couples strongly to the permanent dipole moments of the two levels ({ital d}{sub 1} and {ital d}{sub 2}), creating a large number of equally spaced sidebands (spacing equal to {omega}) that share {mu} among themselves. The distribution of the oscillator strength depends on the universal parameter ({ital d}{sub 2}{minus}d{sub 1})E{sub 0}/{omega}. We determined the transition moment {mu}{sub {ital N}} of the {ital N}th sideband for a variety of ladder and off-ladder systems. Our results indicate that at sufficiently high intensities that are comparable to the threshold of classical chaos of the many-level hydrogen-atom system, off-ladder sidebands become as strong as ladder sidebands, thus breaking the one dimensionality of the system.

  15. Stabilisation of a fibre frequency synthesiser using acousto-optical and electro-optical modulators

    Science.gov (United States)

    Koliada, N. A.; Nyushkov, B. N.; Pivtsov, V. S.; Dychkov, A. S.; Farnosov, S. A.; Denisov, V. I.; Bagayev, S. N.

    2016-12-01

    A fibre-optic frequency synthesiser is developed that is stabilised to the optical frequency standard based on molecular iodine ({\\text{Nd : YAG/I}}2). The possibility of transferring stability of the optical frequency standard to other optical frequencies in the IR range 1 - 2 \\unicode{956}{\\text{m}} and to the RF range by using synthesiser phase-locked loops (PLLs) with acousto-optical and electro-optical modulators is experimentally demonstrated. The additive instability introduced into the optical frequency comb of the synthesiser (which arises due to PLL residual random errors) is several orders less than the intrinsic instability of the reference optical frequency standard employed (i.e., is noticeably less than 1 × 10-13 for 1 {\\text{s}} and 5 × 10-15 for 1000 {\\text{s}}).

  16. Frequency modulation during song in a suboscine does not require vocal muscles.

    Science.gov (United States)

    Amador, Ana; Goller, Franz; Mindlin, Gabriel B

    2008-05-01

    The physiology of sound production in suboscines is poorly investigated. Suboscines are thought to develop song innately unlike the closely related oscines. Comparing phonatory mechanisms might therefore provide interesting insight into the evolution of vocal learning. Here we investigate sound production and control of sound frequency in the Great Kiskadee (Pitangus sulfuratus) by recording air sac pressure and vocalizations during spontaneously generated song. In all the songs and calls recorded, the modulations of the fundamental frequency are highly correlated to air sac pressure. To test whether this relationship reflects frequency control by changing respiratory activity or indicates synchronized vocal control, we denervated the syringeal muscles by bilateral resection of the tracheosyringeal nerve. After denervation, the strong correlation between fundamental frequency and air sac pressure patterns remained unchanged. A single linear regression relates sound frequency to air sac pressure in the intact and denervated birds. This surprising lack of control by syringeal muscles of frequency in Kiskadees, in strong contrast to songbirds, poses the question of how air sac pressure regulates sound frequency. To explore this question theoretically, we assume a nonlinear restitution force for the oscillating membrane folds in a two mass model of sound production. This nonlinear restitution force is essential to reproduce the frequency modulations of the observed vocalizations.

  17. Generating nonlinear FM chirp waveforms for radar.

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter

    2006-09-01

    Nonlinear FM waveforms offer a radar matched filter output with inherently low range sidelobes. This yields a 1-2 dB advantage in Signal-to-Noise Ratio over the output of a Linear FM waveform with equivalent sidelobe filtering. This report presents design and implementation techniques for Nonlinear FM waveforms.

  18. FM Innovation in Science and Practice

    DEFF Research Database (Denmark)

    Mobach, Mark P.; Nardelli, Giulia; Konkol, Jennifer;

    2015-01-01

    Purpose : To report in FM Innovation. Theory : Innovation theory, service management, space design. Design/methodology/approach : Case studies, workshop. Findings : Barriers, areas of interest, and best practices in FM Innovation. Originality/value : Presents a first exploration of European case...... practices in FM Innovation....

  19. Immune particle swarm optimization of linear frequency modulation in acoustic communication

    Institute of Scientific and Technical Information of China (English)

    Haipeng Ren; Yang Zhao

    2015-01-01

    With the exploration of the ocean, underwater acoustic communication has attracted more and more attention in recent years. The underwater acoustic channel is considered to be one of the most complicated channels because it suffers from more serious multipath effect, fewer available bandwidths and quite complex noise. Since the signals experience a serious distortion after being transmitted through the underwater acoustic channel, the underwater acoustic communication experiences a high bit error rate (BER). To solve this problem, carrier waveform inter-displacement (CWID) modulation is proposed. It has been proved that CWID modulation is an effective method to decrease BER. The linear frequency modulation (LFM) carrier-waves are used in CWID modulation. The performance of the communication using CWID modulation is sensitive to the change of the frequency band of LFM carrier-waves. The immune particle swarm optimization (IPSO) is introduced to search for the optimal frequency band of the LFM carrier-waves, due to its excel ent performance in solving complicated optimization problems. The multi-objective and multi-peak optimization nature of the IPSO gives a suitable description of the relationship between the upper band and the lower band of the LFM carrier-waves. Simulations verify the improved perfor-mance and effectiveness of the optimization method.

  20. Amplitude and frequency modulation of the small scales in a turbulent jet

    NARCIS (Netherlands)

    Fiscaletti, D.; Elsinga, G.E.; Ganapathisubramani, B.; Westerweel, J.

    2013-01-01

    This work involves the large-scale amplitude and frequency modulation of the small-scale motions in fullydeveloped turbulence of a high Reynolds number jet. The scales responsible for the production of turbulent kinetic energy (large scales), and those responsible for its viscous dissipation (small

  1. Determination of the velocity of meteors based on sinodial modulation and frequency analysis

    NARCIS (Netherlands)

    Bettonvil, F.C.M.

    2008-01-01

    In meteor photography the velocity of meteors is generally obtained from a chopper which blocks periodically the incident light beam in front of the camera lens. In this paper I examine modulation of the meteor trail instead with a sinodial function and use frequency analysis to compute accurately t

  2. Recognizing cat-eye targets with dual criterions of shape and modulation frequency

    Institute of Scientific and Technical Information of China (English)

    Ximing Ren; Li Li

    2011-01-01

    We present an image recognition method to distinguish targets with cat-eye effect from the dynamic background based on target shape and modulation frequency. Original image sequences to be processed are acquired through an imaging mechanism that utilizes a pulsed laser as active illuminator and an industrial camera as detection device. There are two criterions to recognize a target: one exploits shape priors and the other is the active illuminator's modulation frequency. The feasibility of the proposed method and its superiority over the single criterion method have been demonstrated by practical experiments.%@@ We present an image recognition method to distinguish targets with cat-eye effect from the dynamic background based on target 8hape and modulation frequency.Original image sequences to be processed are acquired through an imaging mechanism that utilizes a pulsed laser as active illuminator and an industrialcamera as detection device.There are two criterions to recognize a target: one exploits shape prior8 and the other is the active illuminator's modulation frequency.The feasibility of the proposed method and its superiority over the single criterion method have been demonstrated by practical experiments.

  3. Broadcasting Stations of the World; Part II. Amplitude Modulation Broadcasting Stations According to Frequency.

    Science.gov (United States)

    Foreign Broadcast Information Service, Washington, DC.

    This second part of "Broadcasting Stations of the World", which lists all reported radio broadcasting and television stations with the exception of those in the United States which broadcast on domestic channels, covers amplitude modulation broadcasting stations according to frequency in ascending order. Information included covers call letters,…

  4. Broadcasting Stations of the World; Part III. Frequency Modulation Broadcasting Stations.

    Science.gov (United States)

    Foreign Broadcast Information Service, Washington, DC.

    This third part of "Broadcasting Stations of the World", which lists all reported radio broadcasting and television stations, with the exception of those in the United States which broadcast on domestic channels, covers frequency modulation broadcasting stations. It contains two sections: one indexed alphabetically by country and city, and the…

  5. Experiments and error analysis of laser ranging based on frequency-sweep polarization modulation

    Science.gov (United States)

    Gao, Shuyuan; Ji, Rongyi; Li, Yao; Cheng, Zhi; Zhou, Weihu

    2016-11-01

    Frequency-sweep polarization modulation ranging uses a polarization-modulated laser beam to determine the distance to the target, the modulation frequency is swept and frequency values are measured when transmitted and received signals are in phase, thus the distance can be calculated through these values. This method gets much higher theoretical measuring accuracy than phase difference method because of the prevention of phase measurement. However, actual accuracy of the system is limited since additional phase retardation occurs in the measuring optical path when optical elements are imperfectly processed and installed. In this paper, working principle of frequency sweep polarization modulation ranging method is analyzed, transmission model of polarization state in light path is built based on the theory of Jones Matrix, additional phase retardation of λ/4 wave plate and PBS, their impact on measuring performance is analyzed. Theoretical results show that wave plate's azimuth error dominates the limitation of ranging accuracy. According to the system design index, element tolerance and error correcting method of system is proposed, ranging system is built and ranging experiment is performed. Experiential results show that with proposed tolerance, the system can satisfy the accuracy requirement. The present work has a guide value for further research about system design and error distribution.

  6. Effect of modulation depth, frequency, and intermittence on wind turbine noise annoyance

    DEFF Research Database (Denmark)

    Ioannidou, Christina; Santurette, Sébastien; Jeong, Cheol-Ho

    2016-01-01

    Amplitude modulation (AM) may be an important factor for the perceived annoyance of wind turbine noise (WTN). Two AM types, typically referred to as “normal AM” (NAM) and “other AM” (OAM), characterize WTN AM, OAM corresponding to having intermittent periods with larger AM depth in lower frequency...

  7. [Design of modulating intermediate frequency electrotherapy system based on microcontroller unit].

    Science.gov (United States)

    Yu, Xuefei; Liu, Xianfeng; Peng, Daming

    2010-12-01

    This article is devoted to the design of a system for modulating intermediate frequency electrotherapy waveform output. Prescriptions with different output waveform combinations were produced using microcontroller unit (MCU). The rich output waveforms effectively improve tolerance of human adaptability and achieve a therapeutic effect.

  8. A novel variable polarity welding power based on high-frequency pulse modulation

    Institute of Scientific and Technical Information of China (English)

    Qiu Ling; Yang Chunli; Fan Chenglei; Lin Sanbao; Wu Yun

    2006-01-01

    A new type of variable polarity welding power modulated with high-frequency pulse current is developed.Series of high-frequency pulse current is superimposed on direct-current-electrode-negative (DCEN), which can improve the crystallization process in the weld bead as a result of the electromagnetic force generated by pulse current.Digital signal processor (DSP) is used to realize the closed-loop control of the first inverter, variable polarity output of the second inverter and high-frequency pulse current superposition.

  9. Digital Square-Wave Frequency Modulated Microwave Sources for a Miniature Optically Pumped Cesium Beam Clock

    Institute of Scientific and Technical Information of China (English)

    CHEN Jingbiao; ZHU Chengjin; LIU Ge; WANG Fengzhi; WANG Yiqiu; YANG Donghai

    2001-01-01

    Three different digital frequencymodulated microwave sources have been designed andapplied to our miniature optically pumped cesiumbeam clock.The main features and their influenceon clock accuracy have been experimentally tested.Itis proved that a digital square-wave frequency modu-lated microwave source using a microprocessor con-trolled direct-digital frequency synthesizer (DDFS)for our miniature optically pumped cesium beamclock works well,the frequency short term stability2 × 10 11/x r and the long term stability 3.5 x 10-13 forone day sample time have been obtained.

  10. Two models of high frequency chest compression therapy: interaction of jacket pressure and mouth airflow.

    Science.gov (United States)

    Lee, Yong Wan; Lee, Jongwon; Warwick, Warren J

    2007-01-01

    High frequency chest compression (HFCC) therapy assists clearing the secretions in the lung. This paper presents two mathematical models: 1) HFCC jacket function model (JFM) and 2) respiratory function model (RFM). JFM predicts the variation of the jacket pressure (Pj) from the respiratory pattern of mouth airflow (Fm). RFM predicts the HFCC induced mouth airflow (Fm) from the HFCC pulse pressures at the jacket (Pj). Fm and Pj were measured from a healthy subject during HFCC therapy. JFM, which was implemented with 2nd order system using prediction error method, shows the existence of breathing pattern at Pj. RFM, which was implemented with amplitude modulation technique, shows how the HFCC pulses affects to the Fm. JFM calculations match 78% of the measured respiratory pattern of Pj>. RFM calculations match 90% of measured HFCC induced Fm. These models can be used to test new breathing patterns before designing studies on patients having chronic obstructive pulmonary diseases.

  11. Double modulation of X radiation diffracted in a quartz single crystal by high and low frequency acoustic waves

    CERN Document Server

    Kocharyan, L A; Bornazyan, H S

    1986-01-01

    The time dependence of X radiation diffracted in a quartz single crystal is experimentally investigated when surface acoustic waves modulated by low frequency oscillations of different frequencies and forms are excited in the crystal.

  12. Very long pulse high-RF power test of a lower hybrid frequency antenna module

    Energy Technology Data Exchange (ETDEWEB)

    Goniche, M.; Brossaud, J.; Barral, C.; Berger-By, G.; Bibet, Ph.; Poli, S.; Rey, G.; Tonon, G. [Association Euratom-CEA, Centre d`Etudes Nucleaires de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Seki, M.; Obara, K. [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment] [and others

    1994-03-01

    Outgassing, induced by very long RF waves injection at high power density was studied in a module, able to be used for a lower hybrid frequency antenna. Good RF properties of the module are reported, however, resonance phenomena with strong absorption of RF power (15%) was observed at high temperature (T>400 deg C). A large outgassing data base is provided by the 75 shots cumulating 27 hours of RF injection. The comparison with previous experiments (Tore Supra and TdV prototype modules) confirm the effect of baking and results are consistent. Outgassing increases exponentially with -1/T, and a desorption model with an activation energy Ed {approx} 0.35 eV fits the data up to 400 deg C. In order to design vacuum pumping system for large lower hybrid frequency antenna, outgassing rates are given for different working temperatures. (author). 11 refs., 55 figs.

  13. Transformation of the frequency-modulated continuous-wave field into a train of short pulses by resonant filters

    CERN Document Server

    Shakhmuratov, R N

    2016-01-01

    The resonant filtering method transforming frequency modulated radiation field into a train of short pulses is proposed to apply in optical domain. Effective frequency modulation can be achieved by electro-optic modulator or by resonant frequency modulation of the filter with a narrow absorption line. Due to frequency modulation narrow-spectrum CW radiation field is seen by the resonant filter as a comb of equidistant spectral components separated by the modulation frequency. Tuning narrow-bandwidth filter in resonance with $n$-th spectral component of the comb transforms the radiation field into bunches of pulses with $n$ pulses in each bunch. The transformation is explained by the interference of the coherently scattered resonant component of the field with the whole comb. Constructive interference results in formation of pulses, while destructive interference is seen as dark windows between pulses. It is found that the optimal thickness of the resonant filter is several orders of magnitude smaller than the...

  14. Single snapshot multiple frequency modulated imaging of subsurface optical properties of turbid media with structured light

    Science.gov (United States)

    Xu, M.; Cao, Zili; Lin, Weihao; Chen, Xinlin; Zheng, Longfei; Zeng, Bixin

    2016-12-01

    We report a novel demodulation method that enables single snapshot wide field imaging of optical properties of turbid media in the Spatial Frequency Domain (SFD). This Single Snapshot Multiple frequency Demodulation (SSMD) method makes use of the orthogonality of harmonic functions to extract the modulation transfer function (MTF) at multiple modulation frequencies simultaneously from a single structured-illuminated image at once. The orientation, frequency, and amplitude of each modulation can be set arbitrarily subject to the limitation of the implementation device. We first validate and compare SSMD to the existing demodulation methods by numerical simulations. The performance of SSMD is then demonstrated with experiments on both tissue mimicking phantoms and in vivo for recovering optical properties by comparing to the standard three-phase demodulation approach. The results show that SSMD increases significantly the data acquisition speed and reduces motion artefacts. SSMD exhibits excellent noise suppression in imaging as well at the rate proportional to the square root of the number of pixels contained in its kernel. SSMD is ideal in the implementation of a real-time spatial frequency domain imaging platform and will open up SFDI for vast applications in imaging and monitoring dynamic turbid medium and processes.

  15. Single snapshot multiple frequency modulated imaging of subsurface optical properties of turbid media with structured light

    Directory of Open Access Journals (Sweden)

    M. Xu

    2016-12-01

    Full Text Available We report a novel demodulation method that enables single snapshot wide field imaging of optical properties of turbid media in the Spatial Frequency Domain (SFD. This Single Snapshot Multiple frequency Demodulation (SSMD method makes use of the orthogonality of harmonic functions to extract the modulation transfer function (MTF at multiple modulation frequencies simultaneously from a single structured-illuminated image at once. The orientation, frequency, and amplitude of each modulation can be set arbitrarily subject to the limitation of the implementation device. We first validate and compare SSMD to the existing demodulation methods by numerical simulations. The performance of SSMD is then demonstrated with experiments on both tissue mimicking phantoms and in vivo for recovering optical properties by comparing to the standard three-phase demodulation approach. The results show that SSMD increases significantly the data acquisition speed and reduces motion artefacts. SSMD exhibits excellent noise suppression in imaging as well at the rate proportional to the square root of the number of pixels contained in its kernel. SSMD is ideal in the implementation of a real-time spatial frequency domain imaging platform and will open up SFDI for vast applications in imaging and monitoring dynamic turbid medium and processes.

  16. Targeted treatment of cancer with radiofrequency electromagnetic fields amplitude-modulated at tumor-specific frequencies

    Institute of Scientific and Technical Information of China (English)

    Jacquelyn W. Zimmerman; Hugo Jimenez; Michael J. Pennison; Ivan Brezovich; Desiree Morgan; Albert Mudry; Frederico P. Costa; Alexandre Barbault; Boris Pasche

    2013-01-01

    In the past century, there have been many attempts to treat cancer with low levels of electric and magnetic fields. We have developed noninvasive biofeedback examination devices and techniques and discovered that patients with the same tumor type exhibit biofeedback responses to the same, precise frequencies. Intrabuccal administration of 27.12 MHz radiofrequency (RF) electromagnetic fields (EMF), which are amplitude-modulated at tumor-specific frequencies, results in long-term objective responses in patients with cancer and is not associated with any significant adverse effects. Intrabuccal administration al ows for therapeutic delivery of very low and safe levels of EMF throughout the body as exemplified by responses observed in the femur, liver, adrenal glands, and lungs. In vitro studies have demonstrated that tumor-specific frequencies identified in patients with various forms of cancer are capable of blocking the growth of tumor cells in a tissue-and tumor-specific fashion. Current experimental evidence suggests that tumor-specific modulation frequencies regulate the expression of genes involved in migration and invasion and disrupt the mitotic spindle. This novel targeted treatment approach is emerging as an appealing therapeutic option for patients with advanced cancer given its excellent tolerability. Dissection of the molecular mechanisms accounting for the anti-cancer effects of tumor-specific modulation frequencies is likely to lead to the discovery of novel pathways in cancer.

  17. Resonance of a Metal Drop under the Effect of Amplitude-Modulated High Frequency Magnetic Field

    Science.gov (United States)

    Guo, Jiahong; Lei, Zuosheng; Zhu, Hongda; Zhang, Lijie; Magnetic Hydrodynamics(Siamm) Team; Magnetic Mechanics; Engineering(Smse) Team

    2016-11-01

    The resonance of a sessile and a levitated drop under the effect of high frequency amplitude-modulated magnetic field (AMMF) is investigated experimentally and numerically. It is a new method to excite resonance of a metal drop, which is different from the case in the presence of a low-frequency magnetic field. The transient contour of the drop is obtained in the experiment and the simulation. The numerical results agree with the experimental results fairly well. At a given frequency and magnetic flux density of the high frequency AMMF, the edge deformations of the drop with an azimuthal wave numbers were excited. A stability diagram of the shape oscillation of the drop and its resonance frequency spectrum are obtained by analysis of the experimental and the numerical data. The results show that the resonance of the drop has a typical character of parametric resonance. The National Natural Science Foundation of China (No. 51274237 and 11372174).

  18. Fiber Bragg-grating strain sensor interrogation using laser radio-frequency modulation.

    Science.gov (United States)

    Gagliardi, G; Salza, M; Ferraro, P; De Natale, P

    2005-04-04

    We demonstrate the possibility of using radio-frequency modulation spectroscopic techniques for interrogation of fiber Bragg-grating (FBG) structures. Sidebands at 2 GHz are superimposed onto the output spectrum of a 1560-nm DFB diode laser. The power reflected by an FBG is demodulated at multiples of the sideband frequency. The sideband-to-carrier beat signal is shown to be extremely sensitive to Bragg wavelength shifts due to mechanical stress. Using this method, both static and dynamic strain measurements can be performed, with a noise-equivalent sensitivity of the order of 150 nepsilon/ radicalHz, in the quasi-static domain (2 Hz), and 1.6 nepsilon/ radicalHz at higher frequencies (1 kHz). The measured frequency response is presently limited at 20 kHz only by the test device bandwidth. A long-term reproducibility in strain measurements within 100 nepsilon is estimated from laser frequency drift referred to molecular absorption lines.

  19. Frequency shift keying by current modulation in a MTJ-based STNO with high data rate

    Science.gov (United States)

    Ruiz-Calaforra, A.; Purbawati, A.; Brächer, T.; Hem, J.; Murapaka, C.; Jiménez, E.; Mauri, D.; Zeltser, A.; Katine, J. A.; Cyrille, M.-C.; Buda-Prejbeanu, L. D.; Ebels, U.

    2017-08-01

    Spin torque nano-oscillators are nanoscopic microwave frequency generators which excel due to their large frequency tuning range and agility for amplitude and frequency modulation. Due to their compactness, they are regarded as suitable candidates for applications in wireless communications, where cost-effective and complementary metal-oxide semiconductor-compatible standalone devices are required. In this work, we study the ability of a magnetic-tunnel-junction based spin torque nano-oscillator to respond to a binary input sequence encoded in a square-shaped current pulse for its application as a frequency-shift-keying (FSK) based emitter. We demonstrate that below the limit imposed by the spin torque nano-oscillator intrinsic relaxation frequency, an agile variation between discrete oscillator states is possible. For this kind of devices, we demonstrate FSK up to data rates of 400 Mbps, which is well suited for the application of such oscillators in wireless networks.

  20. A miniature frequency-stabilized VCSEL system emitting at 795 nm based on LTCC modules

    Science.gov (United States)

    Gruet, Florian; Vecchio, Fabrizio; Affolderbach, Christoph; Pétremand, Yves; de Rooij, Nico F.; Maeder, Thomas; Mileti, Gaetano

    2013-08-01

    We present a compact frequency-stabilized laser system locked to the Rubidium absorption line of a micro-fabricated reference cell. A printed circuit board (PCB) is used to carry all the components and part of the electronics, and low-temperature co-fired ceramic (LTCC) modules are used to temperature-stabilize the laser diode and the miniature Rubidium cell (cell inner dimensions: 5 mm diameter and 2 mm height). The measured frequency stability of the laser, in terms of Allan deviation, is ≤8×10-10 for integration times of 103-105s. The current overall dimensions of the system are 70×40×50 mm3, with good potential for realization of a frequency-stabilized laser module with few cm3 volume.

  1. Parameters estimation of sinusoidal frequency modulation signal with application in synthetic aperture radar imaging

    Science.gov (United States)

    Wang, Yong; Wang, Zhaofa; Zhao, Bin; Xu, Liang

    2016-04-01

    A method for estimating the parameters of the sinusoidal frequency modulation (SFM) signal is presented in this paper. Based on the modified discrete sinusoid frequency modulation transform (DSFMT), the SFM signal can be transformed into the DSFMT domain where it is energy-concentrated and then the parameters can be estimated by the global maximum. To search for the location of the global maximum with less computational load, particle swarm optimization is used in this paper. Then the algorithm is used in the synthetic aperture radar imaging with high frequency vibration of the platform, and the focus performance can be improved significantly. Simulation results demonstrate the effectiveness of the method proposed in this paper.

  2. Improved dichotomous search frequency offset estimator for burst-mode continuous phase modulation

    Institute of Scientific and Technical Information of China (English)

    翟文超; 李赞; 司江勃; 柏均

    2015-01-01

    A data-aided technique for carrier frequency offset estimation with continuous phase modulation (CPM) in burst-mode transmission is presented. The proposed technique first exploits a special pilot sequence, or training sequence, to form a sinusoidal waveform. Then, an improved dichotomous search frequency offset estimator is introduced to determine the frequency offset using the sinusoid. Theoretical analysis and simulation results indicate that our estimator is noteworthy in the following aspects. First, the estimator can operate independently of timing recovery. Second, it has relatively low outlier, i.e., the minimum signal-to-noise ratio (SNR) required to guarantee estimation accuracy. Finally, the most important property is that our estimator is complexity-reduced compared to the existing dichotomous search methods: it eliminates the need for fast Fourier transform (FFT) and modulation removal, and exhibits faster convergence rate without accuracy degradation.

  3. Narrow-linewidth chirped frequency comb from a frequency-shifted feedback Ti:sapphire laser seeded by a phase-modulated single-frequency fiber laser.

    Science.gov (United States)

    Brandl, Matthias F; Mücke, Oliver D

    2010-12-15

    Frequency-shifted feedback (FSF) lasers have emerged as powerful tools for precision distance metrology. At the output of a Michelson interferometer, the detected rf spectra of the FSF laser light contain a length-dependent heterodyne beat signal whose linewidth ultimately limits the achievable accuracy of length measurements. Here, we demonstrate a narrow-linewidth chirped frequency comb from an FSF Ti:sapphire ring laser seeded by a phase-modulated, ultra-low-phase-noise, single-frequency fiber laser. We experimentally investigate the influence of the seed laser linewidth on the resulting width and shape of the length-dependent rf beat signal. An ultranarrow heterodyne beat linewidth of <20 Hz is observed.

  4. Research of Modulation of Bilateral Frequency Difference Based on Load Mode

    Science.gov (United States)

    Lin, Shenghong; Mao, Chizu; Zhu, Jianquan; Lu, Junyu

    2017-05-01

    Owning to high reliability, simple operation and easy acquirement of signals, modulation of bilateral frequency difference (MBFD) in HVDC is worthy for application in practical engineering. With the example of an AC/DC hybrid network and the software PSD-BPA, this paper analyses the effect of MBFD to DC block. The modulators parameters are setting by means of simulation. Two types of loads modes are considered to research the impact of them on simulation. The results indicate that in cooperation with operation modes adjusting at AC system, MBFD will effectively release the impact from DC block and shortage of reactive power caused by rapid variation of DC power owning to modulation. To achieve the best effect, only modulators of some HVDC systems instead of all of them are opened.

  5. 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.......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 two-stage frequency measurement cooperating with digital signal processing. In the experiment, 10GHz measurement range is guaranteed and the average uncertainty of estimated microwave frequency is 5.4MHz, which verifies the measurement accuracy is significantly improved by achieving an unprecedented...

  6. Bilateral collicular interaction: modulation of auditory signal processing in frequency domain.

    Science.gov (United States)

    Cheng, L; Mei, H-X; Tang, J; Fu, Z-Y; Jen, P H-S; Chen, Q-C

    2013-04-01

    In the ascending auditory pathway, the inferior colliculus (IC) receives and integrates excitatory and inhibitory inputs from a variety of lower auditory nuclei, intrinsic projections within the IC, contralateral IC through the commissure of the IC and the auditory cortex. All these connections make the IC a major center for subcortical temporal and spectral integration of auditory information. In this study, we examine bilateral collicular interaction in the modulation of frequency-domain signal processing of mice using electrophysiological recording and focal electrical stimulation. Focal electrical stimulation of neurons in one IC produces widespread inhibition and focused facilitation of responses of neurons in the other IC. This bilateral collicular interaction decreases the response magnitude and lengthens the response latency of inhibited IC neurons but produces an opposite effect on the response of facilitated IC neurons. In the frequency domain, the focal electrical stimulation of one IC sharpens or expands the frequency tuning curves (FTCs) of neurons in the other IC to improve frequency sensitivity and the frequency response range. The focal electrical stimulation also produces a shift in the best frequency (BF) of modulated IC (ICMdu) neurons toward that of electrically stimulated IC (ICES) neurons. The degree of bilateral collicular interaction is dependent upon the difference in the BF between the ICES neurons and ICMdu neurons. These data suggest that bilateral collicular interaction is a part of dynamic acoustic signal processing that adjusts and improves signal processing as well as reorganizes collicular representation of signal parameters according to the acoustic experience.

  7. Frequency-dependent modulation of KCNQ1 and HERG1 potassium channels

    DEFF Research Database (Denmark)

    Diness, Thomas Goldin; Hansen, Rie Schultz; Olesen, Søren-Peter

    2006-01-01

    of the beta-subunits KCNE1 and KCNE2. In addition, the functional role of HERG1 in native guinea pig cardiac myocytes was demonstrated at different pacing frequencies by application of 10microM of the new HERG1 activator, NS1643. In conclusion, we have demonstrated that HERG1 and hKCNQ1 channels are inversely......To obtain information about a possible frequency-dependent modulation of HERG1 and hKCNQ1 channels, we performed heterologous expression in Xenopus laevis oocytes. Channel activation was obtained by voltage protocols roughly imitating cardiac action potentials at frequencies of 1, 3, 5.8, and 8.3Hz....... The activity of HERG1 channels was inhibited down to 65% at high frequencies. In contrast, hKCNQ1 channel activity was increased up to 525% at high frequencies. The general frequency-dependent modulation of the channels was unaffected by both co-expression of hKCNQ1 and HERG1 channels, and by the presence...

  8. BPSK optical mm-wave signal generation by septupling frequency via a single optical phase modulator

    Science.gov (United States)

    Wu, Peng; Ma, Jianxin

    2016-09-01

    In this paper, we have proposed a novel and simple scheme to generate the BPSK optical millimeter wave (MMW) signal with frequency septupling by using an optical phase modulator (PM) and a wavelength selective switch (WSS). In this scheme, the PM is driven by a radio frequency (RF) BPSK signal at the optimized modulation index of 4.89 to assure the 4th and 3rd-order sidebands have equal amplitudes. An wavelength selective switch (WSS) is used to abstract the -4th and +3rd-order sidebands from the spectrum generated by RF BPSK signal modulating the lightwave to form the BPSK optical MMW signal with frequency septupling the driving RF signal. In these two tones, only the +3rd-order sideband bears the BPSK signal while the -4th-order sideband is unmodulated since the phase information is canceled by the even times multiplication of the phase of BPSK signal. The MMW signal can avoid the pulse walk-off effect and the amplitude fading effect caused by the fiber chromatic dispersion. By adjusting the modulation index to assure the two tones have equal amplitude, the generated optical MMW signal has the maximal opto-electrical conversion efficiency and good transmission performance.

  9. The frequency modulated auditory evoked response (FMAER, a technical advance for study of childhood language disorders: cortical source localization and selected case studies

    Directory of Open Access Journals (Sweden)

    Duffy Frank H

    2013-01-01

    Full Text Available Abstract Background Language comprehension requires decoding of complex, rapidly changing speech streams. Detecting changes of frequency modulation (FM within speech is hypothesized as essential for accurate phoneme detection, and thus, for spoken word comprehension. Despite past demonstration of FM auditory evoked response (FMAER utility in language disorder investigations, it is seldom utilized clinically. This report's purpose is to facilitate clinical use by explaining analytic pitfalls, demonstrating sites of cortical origin, and illustrating potential utility. Results FMAERs collected from children with language disorders, including Developmental Dysphasia, Landau-Kleffner syndrome (LKS, and autism spectrum disorder (ASD and also normal controls - utilizing multi-channel reference-free recordings assisted by discrete source analysis - provided demonstratrions of cortical origin and examples of clinical utility. Recordings from inpatient epileptics with indwelling cortical electrodes provided direct assessment of FMAER origin. The FMAER is shown to normally arise from bilateral posterior superior temporal gyri and immediate temporal lobe surround. Childhood language disorders associated with prominent receptive deficits demonstrate absent left or bilateral FMAER temporal lobe responses. When receptive language is spared, the FMAER may remain present bilaterally. Analyses based upon mastoid or ear reference electrodes are shown to result in erroneous conclusions. Serial FMAER studies may dynamically track status of underlying language processing in LKS. FMAERs in ASD with language impairment may be normal or abnormal. Cortical FMAERs can locate language cortex when conventional cortical stimulation does not. Conclusion The FMAER measures the processing by the superior temporal gyri and adjacent cortex of rapid frequency modulation within an auditory stream. Clinical disorders associated with receptive deficits are shown to demonstrate absent

  10. Parkinsonian Rest Tremor Is Associated With Modulations of Subthalamic High-Frequency Oscillations.

    Science.gov (United States)

    Hirschmann, Jan; Butz, Markus; Hartmann, Christian J; Hoogenboom, Nienke; Özkurt, Tolga E; Vesper, Jan; Wojtecki, Lars; Schnitzler, Alfons

    2016-10-01

    High frequency oscillations (>200 Hz) have been observed in the basal ganglia of PD patients and were shown to be modulated by the administration of levodopa and voluntary movement. The objective of this study was to test whether the power of high-frequency oscillations in the STN is associated with spontaneous manifestation of parkinsonian rest tremor. The electromyogram of both forearms and local field potentials from the STN were recorded in 11 PD patients (10 men, age 58 [9.4] years, disease duration 9.2 [6.3] years). Patients were recorded at rest and while performing repetitive hand movements before and after levodopa intake. High-frequency oscillation power was compared across epochs containing rest tremor, tremor-free rest, or voluntary movement and related to the tremor cycle. We observed prominent slow (200-300 Hz) and fast (300-400 Hz) high-frequency oscillations. The ratio between slow and fast high-frequency oscillation power increased when tremor became manifest. This increase was consistent across nuclei (94%) and occurred in medication ON and OFF. The ratio outperformed other potential markers of tremor, such as power at individual tremor frequency, beta power, or low gamma power. For voluntary movement, we did not observe a significant difference when compared with rest or rest tremor. Finally, rhythmic modulations of high-frequency oscillation power occurred within the tremor cycle. Subthalamic high-frequency oscillation power is closely linked to the occurrence of parkinsonian rest tremor. The balance between slow and fast high-frequency oscillation power combines information on motor and medication state. © 2016 International Parkinson and Movement Disorder Society. © 2016 International Parkinson and Movement Disorder Society.

  11. Microwave photonic frequency down-conversion link based on intensity and phase paralleled modulation

    Science.gov (United States)

    Li, Jingnan; Wang, Yunxin; Wang, Dayong; Du, Haozheng; Zhou, Tao; Zhong, Xin; Yang, Dengcai; Li, Hongli

    2016-01-01

    A photonic microwave down-conversion approach is proposed and experimentally demonstrated based on a Mach-Zehnder modulator paralleled with a phase modulator. The incident radio frequency signal and the local oscillator signal are feed to the MZM and PM, respectively, and these two modulated optical signals interfere in the coupler. The useless higher-order sidebands are removed by a tunable optical band-pass filter. The principle of microwave frequency down-conversion is analyzed theoretically, the MZM and PM paralleled frequency down-conversion system is built. Then the performance of system is tested, and the experimental results show that the spurious-free dynamic range achieves 104.8 dB:Hz2/3. Compared to the conventional MZM-MZM cascaded system, the SFDR has been improved by 16 dB. The MZM and PM paralleled frequency down-conversion system can balance the intensity of the two coherent beams easily, and only single DC bias is needed. The proposed method possesses simple structure and high dynamic range.

  12. Remarks on nonlinear relation among phases and frequencies in modulational instabilities of parallel propagating Alfven waves

    CERN Document Server

    Nariyuki, Y; Nariyuki, Yasuhiro; Hada, Tohru

    2006-01-01

    Nonlinear relations among frequencies and phases in modulational instability of circularly polarized Alfven waves are discussed, within the context of one dimensional, dissipation-less, unforced fluid system. We show that generation of phase coherence is a natural consequence of the modulational instability of Alfven waves. Furthermore, we quantitatively evaluate intensity of wave-wave interaction by using bi-coherence, and also by computing energy flow among wave modes, and demonstrate that the energy flow is directly related to the phase coherence generation.

  13. Selectivity enhancement in photoacoustic gas analysis via phase-sensitive detection at high modulation frequency

    Science.gov (United States)

    Kosterev, Anatoliy (Inventor)

    2010-01-01

    A method for detecting a target fluid in a fluid sample comprising a first fluid and the target fluid using photoacoustic spectroscopy (PAS), comprises a) providing a light source configured to introduce an optical signal having at least one wavelength into the fluid sample; b) modulating the optical signal at a desired modulation frequency such that the optical signal generates an acoustic signal in the fluid sample; c) measuring the acoustic signal in a resonant acoustic detector; and d) using the phase of the acoustic signal to detect the presence of the target fluid.

  14. Resolving multipath interference in time-of-flight imaging via modulation frequency diversity and sparse regularization.

    Science.gov (United States)

    Bhandari, Ayush; Kadambi, Achuta; Whyte, Refael; Barsi, Christopher; Feigin, Micha; Dorrington, Adrian; Raskar, Ramesh

    2014-03-15

    Time-of-flight (ToF) cameras calculate depth maps by reconstructing phase shifts of amplitude-modulated signals. For broad illumination of transparent objects, reflections from multiple scene points can illuminate a given pixel, giving rise to an erroneous depth map. We report here a sparsity-regularized solution that separates K interfering components using multiple modulation frequency measurements. The method maps ToF imaging to the general framework of spectral estimation theory and has applications in improving depth profiles and exploiting multiple scattering.

  15. Voice fundamental frequency modulates vocal response to pitch perturbations during English speech.

    Science.gov (United States)

    Liu, Hanjun; Auger, James; Larson, Charles R

    2010-01-01

    Previous research has demonstrated task-dependent vocal responses to pitch perturbations during speech production. The present study investigated the effect of voice fundamental frequency (F(0)) on the modulation of vocal responses during English speech. Randomized pitch shifts of +/-100 or 200 cents during speaking were presented to English speakers. Results indicated larger vocal responses and shorter latencies at a high voice F(0) than at a low voice F(0), but no significance differences were observed for stimulus magnitude or direction. These findings suggest that the pitch-shift reflex during speech can be modulated as a function of voice F(0).

  16. Source of spill ripple in the RF-KO slow-extraction method with FM and AM

    CERN Document Server

    Noda, K; Shibuya, S; Muramatsu, M; Uesugi, T; Kanazawa, M; Torikoshi, M; Takada, E; Yamada, S

    2002-01-01

    The RF-knockout (RF-KO) slow-extraction method with frequency modulation (FM) and amplitude modulation (AM) has brought high-accuracy irradiation to the treatment of a cancer tumor moving with respiration, because of a quick response to beam start/stop. However, a beam spill extracted from a synchrotron ring through RF-KO slow-extraction has a huge ripple with a frequency of around 1 kHz related to the FM. The spill ripple will disturb the lateral dose distribution in the beam scanning methods. Thus, the source of the spill ripple has been investigated through experiments and simulations. There are two tune regions for the extraction process through the RF-KO method: the extraction region and the diffusion region. The particles in the extraction region can be extracted due to amplitude growth through the transverse RF field, only when its frequency matches with the tune in the extraction region. For a large chromaticity, however, the particles in the extraction region can be extracted through the synchrotron ...

  17. Research of beam conditioning technologies using continuous phase plate, Multi-FM smoothing by spectral dispersion and polarization smoothing

    Science.gov (United States)

    Zhang, Rui; Jia, Huaiting; Tian, Xiaocheng; Yuan, Haoyu; Zhu, Na; Su, Jingqin; Hu, Dongxia; Zhu, Qihua; Zheng, Wanguo

    2016-10-01

    In the research of inertial confinement fusion, laser plasma interaction (LPI) is becoming a key problem that affects ignition. Here, multi-frequency modulation (Multi-FM) smoothing by spectral dispersion (SSD), continuous phase plate (CPP) and polarization smoothing (PS) were experimentally studied and implemented on the SG-III laser facility. After using these techniques, the far field distribution of SG-Ⅲ laser facility can be adjusted, controlled and repeated accurately. The output spectrums of the cascade phase modulators used for Multi-FM SSD were stable and the FM-to-AM effect can be restrained. Experiments on SG-III laser facility indicate that when the number of color cycles adopts 1, imposing SSD with 3.3 times diffraction limit (TDL) did not lead to pinhole closure in the spatial filters of preamplifier and main amplifiers with 30-TDL pinhole size. The nonuniformity of the focal spots using Multi-FM SSD, CPP and PS drops to 0.18, comparing to 0.26 with CPP+SSD, 0.57 with CPP+PS and 0.84 with only CPP and wedged lens. Polarization smoothing using flat birefringent plate in the convergent beam of final optics assembly (FOA) was studied. The PS plates were manufactured and equipped on SG-III laser facility for LPI research. Combined beam smoothing and polarization manipulation were also studied to solve the LPI problem. Results indicate that through adjusting dispersion directions of SSD beams in a quad, two dimensional SSD can be obtained. Using polarization control plate (PCP), polarization on the near field and far field can be manipulated, providing new method to solve LPI problem in indirect drive laser fusion.

  18. Influence of Intermediate Frequency Bandwidth Setting on Demodulation Performance of FM Telemetry System%中频带宽对调频遥测解调性能的影响分析

    Institute of Scientific and Technical Information of China (English)

    朱宏权; 王俊峰

    2013-01-01

    接收机中频带宽是影响调频(FM)遥测解调误码性能的一个重要因素.根据FM信号的解调原理,对非相干鉴频和多符号检测2种解调方式下,中频带宽对解调误码率性能的影响进行了仿真分析,提出了最优误码性能下中频带宽参数的推荐值为1.2倍码速率,通过硬件实验对仿真分析结果进行了验证.

  19. Profiling value added position in FM

    DEFF Research Database (Denmark)

    Katchamart, Akarapong

    organizations can best add value. Based on comprehensive literature studies and 7 case studies of private and public organisations from Denmark, Holland, Hong Kong and Thailand, the dissertation analyses, how FM organizations can best create added value. From the analyses the following four value added...... - FM organizations influence the business productivities and outcome Each type of value added requires specific conditions and contingencies involved. This research thus offers a visual aid tool, “FM product-process matrix”, to assist practitioners to indicate their existing circumstances and contexts...... the unarticulated notions of added value from FM organization and activities. It will broaden the managerial perception and discussion on FM provision ´s abilities and capabilities. The results are besides the field of FM also of relevance for management of other service industries and functions....

  20. KARAKTERISTIK BAHASA PENYIAR RADIO JPI FM SOLO

    Directory of Open Access Journals (Sweden)

    Muhammad Rohmadi

    2004-06-01

    Full Text Available Bahasa adalah alat komunikasi yang digunakan penyiar Radio JPI FM Solo untuk berkomunikasi dengan para pendengarnya. Bahasa penyiar radio memiliki berbagai variasi dan karakter tersendiri dibandingkan bahasa-bahasa yang digunakan dalam ranah pendidikan, pemerintahan, dan keluarga. Karakteristik ragam bahasa penyiar Radio JPI FM Solo diwarnal campur kode, alih kode, dan nuansa humor dalam siarannya. Tujuan utama penyiar Radio JPI FM Solo adalah untuk menarik simpati pendengar dan berinteraksi dengan para pendengar Radio JPI FM Solo secara kreatif. Selain itu, ragam bahasa penyiar Radio JPI FM Solo memanfatkan beberapa fungsi utama ketika berkomunikasi dengan pendengarnya. Fungsi-fungsi tersebut adalah fungsi puitik, fungsi direktif, fungsi fatis, fungsi ekspresif, dan fungsi referensial dalam siaran Radio JPI FM Solo.

  1. The concept of added value of FM

    DEFF Research Database (Denmark)

    2012-01-01

    Purpose: This chapter presents research perspectives and theoretical reflections on the concept of added value of FM from a variety of academic fields. Methodology: A literature review of the most influential journals within the academic fields of Facilities Management (FM), Corporate Real Estate...... conceptualization of the concept of added value of FM is of utmost importance for further research into the added value of FM and well-considered, evidence- based Value Adding Management in practice. Research limitations: Due to limited time not all FM-related journals could be included in the literature review...... Management (CREM) and Business to Business Marketing (B2B Marketing). Findings: The research shows different definitions and focus points, dependent on the academic field and the area of application. The different research perspectives explored a holistic view on the added value of FM by the integration...

  2. Low-frequency analog signal distribution on digital photonic networks by optical delta-sigma modulation

    Science.gov (United States)

    Kanno, Atsushi; Kawanishi, Tetsuya

    2013-12-01

    We propose a delta-sigma modulation scheme for low- and medium-frequency signal transmission in a digital photonic network system. A 10-Gb/s-class optical transceiver with a delta-sigma modulator utilized as a high-speed analog-to-digital converter (ADC) provides a binary optical signal. On the signal reception side, a low-cost and slow-speed photonic receiver directly converts the binary signal into an analog signal at frequencies from several hundreds of kilohertz several tens of megahertz. Further, by using a clock and data recovery circuit at the receiver to reduce jitters, the single-sideband phase noise of the generated signals can be significantly reduced.

  3. Double-wavelet approach to study frequency and amplitude modulation in renal autoregulation

    DEFF Research Database (Denmark)

    Sosnovtseva, Olga; Pavlov, A N; Mosekilde, E;

    2004-01-01

    Biological time series often display complex oscillations with several interacting rhythmic components. Renal autoregulation, for instance, involves at least two separate mechanisms both of which can produce oscillatory variations in the pressures and flows of the individual nephrons. Using double......-wavelet analysis we propose a method to examine how the instantaneous frequency and amplitude of a fast mode is modulated by the presence of a slower mode. Our method is applied both to experimental data from normotensive and hypertensive rats showing different oscillatory patterns and to simulation results...... obtained from a physiologically based model of the nephron pressure and flow control. We reveal a nonlinear interaction between the two mechanisms that regulate the renal blood flow in the form of frequency and amplitude modulation of the myogenic oscillations....

  4. Sub-optical wavelength acoustic wave modulation of integrated photonic resonators at microwave frequencies

    CERN Document Server

    Tadesse, Semere Ayalew

    2014-01-01

    Light-sound interactions have long been exploited in various acousto-optic devices based on bulk crystalline materials. Conventionally these devices operate in megahertz frequency range where the acoustic wavelength is much longer than the optical wavelength and a long interaction length is required to attain significant coupling. With nanoscale transducers, acoustic waves with sub-optical wavelengths can now be excited to induce strong acousto-optic coupling in nanophotonic devices. Here we demonstrate microwave frequency surface acoustic wave transducers co-integrated with nanophotonic resonators on piezoelectric aluminum nitride substrates. Acousto-optic modulation of the resonance modes at above 10 GHz with the acoustic wavelength significantly below the optical wavelength is achieved. The phase and modal matching conditions in this scheme are investigated for efficient modulation. The new acousto-optic platform can lead to novel optical devices based on nonlinear Brillouin processes and provides a direct...

  5. COMPARISON OF SIGMA-DELTA MODULATOR FOR FRACTIONAL-N PLL FREQUENCY SYNTHESIZER

    Institute of Scientific and Technical Information of China (English)

    Mao Xiaojian; Yang Huazhong; Wang Hui

    2007-01-01

    This paper investigates the design of digital Sigma-Delta Modulator(SDM)for fractional-N frequency synthesizer.Characteristics of SDMs are compared through theory analysis and simulation.The curve of maximum-loop-bandwidth vs.maximum-phase-noise is suggested to be a new criterion to the performance of SDM.which greatly helps designers to select an appropriate SDM structure to meet their real application requirements and to reduce the cost as low as possible.A low-spur 3-order Multistage Noise Shaping(MASH)-1-1-1 SDM using three 2-bit first-order cascaded modulators is proposed,which balances the requirements of tone-free and maximum operation frequency.

  6. Pacemaking the ice ages by frequency modulation of Earth's orbital eccentricity

    Science.gov (United States)

    Rial

    1999-07-23

    Evidence from power spectra of deep-sea oxygen isotope time series suggests that the climate system of Earth responds nonlinearly to astronomical forcing by frequency modulating eccentricity-related variations in insolation. With the help of a simple model, it is shown that frequency modulation of the approximate 100,000-year eccentricity cycles by the 413,000-year component accounts for the variable duration of the ice ages, the multiple-peak character of the time series spectra, and the notorious absence of significant spectral amplitude at the 413,000-year period. The observed spectra are consistent with the classic Milankovitch theories of insolation, so that climate forcing by 100,000-year variations in orbital inclination that cause periodic dust accretion appear unnecessary.

  7. Variable Voltage Source Inverter with controlled frequency spectrum based on Random Pulse Width Modulation

    Directory of Open Access Journals (Sweden)

    Muhammad Farrukh Yaqub

    2012-01-01

    Full Text Available This paper presents a new method for single phase variable voltage inverter based on Random Pulse Width Modulation. In Random Pulse Width Modulation based inverter, the frequency spectrum of the output current and voltage waveforms becomes continuous because of the randomization of the switching function of the devices controlling the output voltages. This paper establishes a theory that if the distributions of the random numbers generated by the random source are kept within certain limit with respect to the peak value of reference sinusoidal waveform, the frequency spectrum can be controlled. On the basis of the results, a novel drive using variable tap changing transformer (optional and adaptive random number generator, to control the ratio between the numbers generated by the random source and the reference waveform has been suggested that will guarantee a better power quality profile for a broad range of output voltages.

  8. Convective stability in the Rayleigh-Benard and directional solidification problems - High-frequency gravity modulation

    Science.gov (United States)

    Wheeler, A. A.; Mcfadden, G. B.; Murray, B. T.; Coriell, S. R.

    1991-01-01

    The effect of vertical, sinusoidal, time-dependent gravitational acceleration on the onset of solutal convection during directional solidification is analyzed in the limit of large modulation frequency. When the unmodulated state is unstable, the modulation amplitude required to stabilize the system is determined by the method of averaging. When the unmodulated state is stable, resonant modes of instability occur at large modulation amplitude. These are analyzed using matched asymptotic expansions to elucidate the boundary-layer structure for both the Rayleigh-Benard and directional solidification configurations. Based on these analyses, a thorough examination of the dependence of the stability criteria on the unmodulated Rayleigh number, Schmidt number, and distribution coefficient, is carried out.

  9. Frequency Modulated Continuous Wave RADAR for Objects Mapping in Enclosed Spaces Using Smartphones and Arduino Components

    Science.gov (United States)

    Bar-Magen Numhauser, Jonathan; Zalevsky, Zeev

    2017-06-01

    Based on previous studies and using mobile portable device, we were able to realize a portable system capable of detecting metallic objects in a room surrounded by walls while also extracting the approximate position of such objects. Our hardware included only a smartphone device connected to several Arduino components and we were applying frequency-modulated continuous-wave electronics in each of the Arduino devices.

  10. Analisys of alternatives for sidelobe reduction in linearly frequency modulated pulses

    Directory of Open Access Journals (Sweden)

    Jorge Torres Gómez

    2013-02-01

    Full Text Available Taking The present article deals with the topic of windowing techniques for sidelobe reduction inlinearly frequency modulated (LFM pulses compressed by an adapted filter. Main characteristics ofwindow´s techniques are presented; focusing on those that improves the window´s performance. Designsare simulated in a Graphic User Interface in MatLab and Simulink to conform it on FPGA. Simulationof carried out softwares allows the selection of the best choice as the case of interest.

  11. Voice fundamental frequency modulates vocal response to pitch perturbations during English speech

    OpenAIRE

    Liu, Hanjun; Auger, James; Charles R Larson

    2009-01-01

    Previous research has demonstrated task-dependent vocal responses to pitch perturbations during speech production. The present study investigated the effect of voice fundamental frequency (F0) on the modulation of vocal responses during English speech. Randomized pitch shifts of ±100 or 200 cents during speaking were presented to English speakers. Results indicated larger vocal responses and shorter latencies at a high voice F0 than at a low voice F0, but no significance differences were obse...

  12. Atomic orientation by a broadly frequency-modulated radiation: theory and experiment

    CERN Document Server

    Bevilacqua, G; Dancheva, Y

    2016-01-01

    We investigate magnetic resonances driven in thermal vapour of alkali atoms by laser radiation broadly modulated at a frequency resonant with the Zeeman splitting. A model accounting for both hyperfine and Zeeman pumping is developed and its results are compared with experimental measurements performed at relatively weak pump irradiance. The interplay between the two pumping processes generates intriguing interaction conditions, often overlooked by simplified models.

  13. About the Phasor Pathways in Analogical Amplitude Modulation

    CERN Document Server

    de Oliveira, H M

    2015-01-01

    The Phasor diagrams have long been used in Physics and Engineering. In telecommunications, this is particularly useful to clarify how the modulations work. This paper addresses rotating phasor pathways derived from different standard Amplitude Modulation Systems (e.g. A3E, H3E, J3E, C3F). A cornucopia of algebraic curves is then derived assuming a single tone or a double tone modulation signal. The ratio of the frequency of the tone modulator (fm) and carrier frequency (fc) is considered in two distinct cases, namely: fm/fc=1. The geometric figures are some sort of Lissajours figures. Different shapes appear looking like epicycloids (including cardioids), rhodonea curves, Lemniscates, folium of Descartes or Lam\\'e curves. The role played by the modulation index is elucidated in each case.

  14. Frequency modulated weak signal detection based on stochastic resonance and genetic algorithm

    Institute of Scientific and Technical Information of China (English)

    XING; Hongyan; LU; Chunxia; ZHANG; Qiang

    2016-01-01

    Stochastic resonance system is subject to the restriction of small frequency parameter in weak signal detection,in order to solve this problem,a frequency modulated weak signal detection method based on stochastic resonance and genetic algorithm is presented in this paper. The frequency limit of stochastic resonance is eliminated by introducing carrier signal,which is multiplied with the measured signal to be injected in the stochastic resonance system,meanwhile,using genetic algorithm to optimize the carrier signal frequency,which determine the generated difference-frequency signal in the lowfrequency range,so as to achieve the stochastic resonance weak signal detection. Results showthat the proposed method is feasible and effective,which can significantly improve the output SNR of stochastic resonance,in addition,the system has the better self-adaptability,according to the operation result and output phenomenon,the unknown frequency of the signal to be measured can be obtained,so as to realize the weak signal detection of arbitrary frequency.

  15. Low-frequency vibration modulation of guided waves to image nonlinear scatterers for structural health monitoring

    Science.gov (United States)

    Jiao, J. P.; Drinkwater, B. W.; Neild, S. A.; Wilcox, P. D.

    2009-06-01

    Guided wave structural health monitoring offers the prospect of continuous interrogation of large plate-like structures with a sparse network of permanently attached sensors. Currently, the most common approach is to monitor changes in the received signals by subtraction from a reference signal obtained when the structure was known to be defect-free. In this paper a comparison is made between this defect-free subtraction approach and a technique in which low-frequency vibration modulation of guided wave signals is used to detect nonlinear scatterers. The modulation technique potentially overcomes the need for the defect-free reference measurement as the subtraction is now made between different parts of an externally applied low-frequency vibration. Linear defects were simulated by masses bonded onto a plate and nonlinear scatterers were simulated by loading a similar mass against the plate. The experimental results show that the defect-free subtraction technique performs well in detecting the bonded mass whereas the modulation technique is able to discriminate between the bonded and loaded masses. Furthermore, because the modulation technique does not require a defect-free reference, it is shown to be relatively independent of temperature effects, a significant problem for reference based subtraction techniques.

  16. An ultrawide-bandwidth single-sideband modulator for terahertz frequencies

    Science.gov (United States)

    Meijer, A. S.; Berden, G.; Arslanov, D. D.; Ozerov, M.; Jongma, R. T.; van der Zande, W. J.

    2016-11-01

    Wireless high-speed data communication using terahertz (THz) carrier frequencies is becoming reality with data rates beyond 100 Gbit s-1. Many of the mobile applications use internet access and require that THz wireless base stations are connected to a global network, such as the radio-over-fibre network. We present the realization of an ultrawide bandwidth THz optical single-sideband (OSSB) modulator for converting (free-space) THz signals to THz optical modulations with an increased spectral efficiency. THz OSSB will mitigate chromatic dispersion-induced propagation losses in optical fibres and support digital modulation schemes. We demonstrate THz OSSB for free-space radiation between 0.3 and 1.0 THz using a specially designed dichroic beamsplitter for signal and carrier, and a planar light-wave circuit with multimode interference structures. This arrangement of optical elements mimics the Hartley single-sideband modulator for electronics signals and accomplishes the required Hilbert transform without any frequency-dependent tuning element over an ultrawide THz spectrum.

  17. The making of the FM value map

    DEFF Research Database (Denmark)

    2012-01-01

    Purpose: To present the FM Value Map and the background, process and considerations of its development and to reflect on perspectives and limitations. Methodology: The FM Value Map was developed from cases studies as part of the research project Facilities Management Best Practice in the Nordic....... Practical implications: The FM Value Map is a conceptual framework which can help to understand and explain the different ways that FM can create and add value to a core business and possibly to the surroundings. Furthermore, the value map may be used to identify and demonstrate the elements which...

  18. On second order effects in a galvanic cell : Part I. Polarization by a sine wave modulated high frequency current

    NARCIS (Netherlands)

    Pol, F. van der; Sluyters-Rehbach, M.; Sluyters, J.H.

    1975-01-01

    A theoretical study is presented concerning the application of a high-frequency alternating current, amplitude modulated by a low-frequency sine wave, to a galvanic cell. Based on the correlation with the faradaic rectification technique, expressions are given for the low-frequency demodulation

  19. Homogeneous spectral spanning of terahertz semiconductor lasers with radio frequency modulation

    Science.gov (United States)

    Wan, W. J.; Li, H.; Zhou, T.; Cao, J. C.

    2017-03-01

    Homogeneous broadband and electrically pumped semiconductor radiation sources emitting in the terahertz regime are highly desirable for various applications, including spectroscopy, chemical sensing, and gas identification. In the frequency range between 1 and 5 THz, unipolar quantum cascade lasers employing electron inter-subband transitions in multiple-quantum-well structures are the most powerful semiconductor light sources. However, these devices are normally characterized by either a narrow emission spectrum due to the narrow gain bandwidth of the inter-subband optical transitions or an inhomogeneous broad terahertz spectrum from lasers with heterogeneous stacks of active regions. Here, we report the demonstration of homogeneous spectral spanning of long-cavity terahertz semiconductor quantum cascade lasers based on a bound-to-continuum and resonant phonon design under radio frequency modulation. At a single drive current, the terahertz spectrum under radio frequency modulation continuously spans 330 GHz (~8% of the central frequency), which is the record for single plasmon waveguide terahertz lasers with a bound-to-continuum design. The homogeneous broadband terahertz sources can be used for spectroscopic applications, i.e., GaAs etalon transmission measurement and ammonia gas identification.

  20. Demodulation effect is observed in neurones by exposure to low frequency modulated microwaves

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Bruzon, R N; Figols, T; Azanza, M J [Laboratorio de Magnetobiologia, Departamento de Anatomia e Histologia Humanas, Facultad de Medicina, Universidad de Zaragoza (Spain); Moral, A del, E-mail: naogit@yahoo.co [Laboratorio de Magnetismo de Solidos, Departamento de Fisica de Materia Condensada and Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza and CSIC (Spain)

    2010-01-01

    Neurones exposure to a microwave (carrier f{sub c}=13.6 GHz; power P {approx_equal} 5 mW; H{sub o} {approx_equal} 0.10 Am{sup -1} = 1.25 mOe; E{sub 0} {approx_equal} 3.5 V/m; {Delta}T {approx_equal} 0.01{sup 0}C; SAR: 3.1x10{sup -3} - 5.8x10{sup -3} W/Kg) EMF amplitude modulated by ELF-AC field (frequency, f{sub m}= 0-100 Hz) shows no electrophysiological effect under the carrier MF alone, but {sup f}requency resonances: at 2, 4, 8, 12, 16, 50, 100 Hz: demodulation effect. Resonances appear when applied ELF-MF is close to a dominant characteristic frequency of the neurone impulse Fourier spectrum. This is an interesting result considering that ELF-MF modulating RF or MW in the range of human EEG could induce frequency-resonant effects on exposed human brain.

  1. Homogeneous spectral spanning of terahertz semiconductor lasers with radio frequency modulation

    Science.gov (United States)

    Wan, W. J.; Li, H.; Zhou, T.; Cao, J. C.

    2017-01-01

    Homogeneous broadband and electrically pumped semiconductor radiation sources emitting in the terahertz regime are highly desirable for various applications, including spectroscopy, chemical sensing, and gas identification. In the frequency range between 1 and 5 THz, unipolar quantum cascade lasers employing electron inter-subband transitions in multiple-quantum-well structures are the most powerful semiconductor light sources. However, these devices are normally characterized by either a narrow emission spectrum due to the narrow gain bandwidth of the inter-subband optical transitions or an inhomogeneous broad terahertz spectrum from lasers with heterogeneous stacks of active regions. Here, we report the demonstration of homogeneous spectral spanning of long-cavity terahertz semiconductor quantum cascade lasers based on a bound-to-continuum and resonant phonon design under radio frequency modulation. At a single drive current, the terahertz spectrum under radio frequency modulation continuously spans 330 GHz (~8% of the central frequency), which is the record for single plasmon waveguide terahertz lasers with a bound-to-continuum design. The homogeneous broadband terahertz sources can be used for spectroscopic applications, i.e., GaAs etalon transmission measurement and ammonia gas identification. PMID:28272492

  2. 基于自适应陷波器的噪声调频干扰抑制方法%FM Interference Noise Suppression Based on Adaptive Notch Filter

    Institute of Scientific and Technical Information of China (English)

    路翠华; 李国林; 谢鑫

    2014-01-01

    Aiming at the problem that linear frequency-modulated fuze’s ability of anti-noise interference was poor,the method of noise FM interference suppression based on adaptive notch filter was presented.According to the characteristic that the difference frequency signal of linear frequency-modulated fuze was monochromatic, an adaptive notch filter was adopted to suppress FM interference noise in linear frequency-modulated fuze. Through adj usting notch filter’s weights,the notch filter has the notch characteristics in difference frequency signal's frequency,then noise FM interference was suppressed.The simulation results showed that when SJR=-10dB,FM interference noise could be still suppressed effectively.%针对线性调频引信抗噪声干扰能力比较差的问题,提出了基于自适应陷波器的噪声调频干扰抑制方法。该方法根据线性调频引信差频信号的单频特性,将自适应陷波器应用到线性调频引信中,对噪声调频干扰进行抑制。通过自适应调整陷波器的权值,使陷波器在差频信号的频率点具有陷波特性,从而达到噪声调频干扰抑制的目的。仿真结果表明:SJB=-10 dB时,仍然能达到很好的噪声调频干扰抑制效果。

  3. OCT based on multi-frequency sweeping Fizeau interferometer with phase modulating method

    Science.gov (United States)

    Choi, S.; Watanabe, T.; Sasaki, O.; Suzuki, T.

    2013-09-01

    The Multi-frequency sweeping Fizeau-type interferometer (MFS-FI) for optical coherence tomography (OCT) is demonstrated. The multi-frequency sweeping by a variable Fabry-Perot filter permits detection of high-order low-coherence interferometric signals in the Fizeau interferometer. The sinusoidal phase modulation technique was utilized to detect accurate interference amplitude and phase distributions of back scattered light from surfaces of a sample. OCT measurements by the MFS-FI were conducted for vibrating glass plates with a frequency of 1 kHz, and cellular tissues fixed with formalin and embedded in paraffin. The tomographic 3-dimensional volume and cross-sectional surface displacements were detected with an accuracy of nano-meters.

  4. On natural frequencies of non-uniform beams modulated by finite periodic cells

    Science.gov (United States)

    Xu, Yanlong; Zhou, Xiaoling; Wang, Wei; Wang, Longqi; Peng, Fujun; Li, Bin

    2016-09-01

    It is well known that an infinite periodic beam can support flexural wave band gaps. However, in real applications, the number of the periodic cells is always limited. If a uniform beam is replaced by a non-uniform beam with finite periodicity, the vibration changes are vital by mysterious. This paper employs the transfer matrix method (TMM) to study the natural frequencies of the non-uniform beams with modulation by finite periodic cells. The effects of the amounts, cross section ratios, and arrangement forms of the periodic cells on the natural frequencies are explored. The relationship between the natural frequencies of the non-uniform beams with finite periodicity and the band gap boundaries of the corresponding infinite periodic beam is also investigated. Numerical results and conclusions obtained here are favorable for designing beams with good vibration control ability.

  5. Short-interval intracortical inhibition is modulated by high-frequency peripheral mixed nerve stimulation.

    Science.gov (United States)

    Murakami, Takenobu; Sakuma, Kenji; Nomura, Takashi; Nakashima, Kenji

    2007-06-01

    Cortical excitability can be modulated by manipulation of afferent input. We investigated the influence of peripheral mixed nerve stimulation on the excitability of the motor cortex. Motor evoked potentials (MEPs), short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) in the right abductor pollicis brevis (APB), extensor carpi radialis (ECR) and first dorsal interosseous (FDI) muscles were evaluated using paired-pulse transcranial magnetic stimulation (TMS) before and after high-frequency peripheral mixed nerve stimulation (150 Hz, 30 min) over the right median nerve at the wrist. The MEP amplitude and SICI of the APB muscle decreased transiently 0-10 min after the intervention, whereas the ICF did not change. High-frequency peripheral mixed nerve stimulation reduced the excitability of the motor cortex. The decrement in the SICI, which reflects the function of GABA(A)ergic inhibitory interneurons, might compensate for the reduced motor cortical excitability after high-frequency peripheral mixed nerve stimulation.

  6. A kinetic model for the frequency dependence of cholinergic modulation at hippocampal GABAergic synapses.

    Science.gov (United States)

    Stone, Emily; Haario, Heikki; Lawrence, J Josh

    2014-12-01

    In this paper we use a simple model of presynaptic neuromodulation of GABA signaling to decipher paired whole-cell recordings of frequency dependent cholinergic neuromodulation at CA1 parvalbumin-containing basket cell (PV BC)-pyramidal cell synapses. Variance-mean analysis is employed to normalize the data, which is then used to estimate parameters in the mathematical model. Various parameterizations and hidden parameter dependencies are investigated using Markov Chain Monte Carlo (MCMC) parameter estimation techniques. This analysis reveals that frequency dependence of cholinergic modulation requires both calcium-dependent recovery from depression and mAChR-induced inhibition of presynaptic calcium entry. A reduction in calcium entry into the presynaptic terminal in the kinetic model accounted for the frequency-dependent effects of mAChR activation.

  7. High-frequency radar observations of PMSE modulation by radio heating

    Science.gov (United States)

    Senior, Andrew; Rietveld, Michael; Mahmoudian, Alireza; La Hoz, Cesar; Kosch, Michael; Scales, Wayne; Pinedo, Henry

    The first observations using high-frequency (8 MHz) radar of modulation of polar mesospheric summer echoes (PMSE) by radio heating of the ionosphere are presented. The experiment was performed at the EISCAT facility near Tromsø, Norway. The observations are compared with simultaneous radar measurements at 224 MHz and with a model of the dusty plasma response to electron heating. Agreement between the model and observations is good considering technical limitations on the 8 MHz radar measurements. Predictions made about the response of high-frequency PMSE to heating where dust charging dominates over diffusion, opposite to the situation at very high-frequencies are confirmed. Suggestions are made about improving the 8 MHz observations to overcome the current limitations.

  8. Increased Low- and High-Frequency Oscillatory Activity in the Prefrontal Cortex of Fibromyalgia Patients

    Science.gov (United States)

    Lim, Manyoel; Kim, June Sic; Kim, Dajung J.; Chung, Chun Kee

    2016-01-01

    Recent human neuroimaging studies have suggested that fibromyalgia (FM), a chronic widespread pain disorder, exhibits altered thalamic structure and function. Since the thalamus has extensive reciprocal connection with the cortex, structural and functional thalamic alterations in FM might be linked to aberrant thalamocortical oscillation. This study investigated the presence of abnormal brain rhythmicity in low- and high-frequency bands during resting state in patients with FM and their relationship to clinical pain symptom. Spontaneous magnetoencephalography (MEG) activity was recorded in 18 females with FM and 18 age- and sex-matched healthy control (HC) subjects. The most remarkable finding was that FM patients had general increases in theta, beta and gamma power along with a slowing of the dominant alpha peak. Increased spectral powers in the theta-band were primarily localized to the left dorsolateral prefrontal (DLPFC) and orbitofrontal cortex (OFC). Beta and gamma over-activation were localized to insular, primary motor and primary and secondary somatosensory (S2) cortices, as well as the DLPFC and OFC. Furthermore, enhanced high-frequency oscillatory activities in the DLPFC and OFC were associated with higher affective pain scores in patients with FM. Our results demonstrate that FM patients feature enhanced low- and high-frequency oscillatory activity in the brain areas related to cognitive and emotional modulation of pain. Increased low- and high-frequency activity of the prefrontal cortex may contribute to persistent perception of pain in FM. Therapeutic intervention based on manipulating neural oscillation to restore normal thalamocortical rhythmicity may be beneficial to pain relief in FM. PMID:27014041

  9. Feasibility of frequency-modulated wireless transmission for a multi-purpose MEMS-based accelerometer.

    Science.gov (United States)

    Sabato, Alessandro; Feng, Maria Q

    2014-09-05

    Recent advances in the Micro Electro-Mechanical System (MEMS) technology have made wireless MEMS accelerometers an attractive tool for Structural Health Monitoring (SHM) of civil engineering structures. To date, sensors' low sensitivity and accuracy--especially at very low frequencies--have imposed serious limitations for their application in monitoring large-sized structures. Conventionally, the MEMS sensor's analog signals are converted to digital signals before radio-frequency (RF) wireless transmission. The conversion can cause a low sensitivity to the important low-frequency and low-amplitude signals. To overcome this difficulty, the authors have developed a MEMS accelerometer system, which converts the sensor output voltage to a frequency-modulated signal before RF transmission. This is achieved by using a Voltage to Frequency Conversion (V/F) instead of the conventional Analog to Digital Conversion (ADC). In this paper, a prototype MEMS accelerometer system is presented, which consists of a transmitter and receiver circuit boards. The former is equipped with a MEMS accelerometer, a V/F converter and a wireless RF transmitter, while the latter contains an RF receiver and a F/V converter for demodulating the signal. The efficacy of the MEMS accelerometer system in measuring low-frequency and low-amplitude dynamic responses is demonstrated through extensive laboratory tests and experiments on a flow-loop pipeline.

  10. Mechanical Properties of Microcrystalline Metal-Organic Frameworks (MOFs) Measured by Bimodal Amplitude Modulated-Frequency Modulated Atomic Force Microscopy.

    Science.gov (United States)

    Sun, Yao; Hu, Zhigang; Zhao, Dan; Zeng, Kaiyang

    2017-09-08

    Direct measurement of the mechanical properties of microcrystalline metal-organic framework (MOF) nanoparticles is challenging and rarely explored. In this work, we apply an effective method to realize elastic modulus mapping of a series of isostructural single MOF nanoparticles (100-500 nm) via bimodal amplitude modulated-frequency modulated atomic force microscopy. By probing five types of zirconium (Zr) and hafnium (Hf) isostructural UiO-66-type MOFs, we experimentally found that UiO-66(Hf)-type MOFs possess the higher elastic modulus (46-104 GPa) than that of UiO-66(Zr)-type MOFs (34-100 GPa), both of which are higher than that of reported zinc/copper based MOFs (3-10 GPa). We also experimentally demonstrate that the mechanical properties of MOFs can be tuned by adjusting the chemical functionalities of the ligands or using different metal nodes. In detail, the sterically bulky functional groups increase the mechanical properties of the resultant UiO-66-type MOFs, possibly due to the increased atomic density. These results pave a way to the direct measurement of mechanical properties of MOFs crystalline particles and provide an incisive perspective to the design of MOFs with high mechanical properties.

  11. Mapping power-law rheology of living cells using multi-frequency force modulation atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Ryosuke; Okajima, Takaharu, E-mail: okajima@ist.hokudai.ac.jp [Graduate School of Information Science and Technology, Hokkaido University, Kita-ku N14 W9, Sapporo 060-0814 (Japan)

    2015-10-26

    We present multi-frequency force modulation atomic force microscopy (AFM) for mapping the complex shear modulus G* of living cells as a function of frequency over the range of 50–500 Hz in the same measurement time as the single-frequency force modulation measurement. The AFM technique enables us to reconstruct image maps of rheological parameters, which exhibit a frequency-dependent power-law behavior with respect to G{sup *}. These quantitative rheological measurements reveal a large spatial variation in G* in this frequency range for single cells. Moreover, we find that the reconstructed images of the power-law rheological parameters are much different from those obtained in force-curve or single-frequency force modulation measurements. This indicates that the former provide information about intracellular mechanical structures of the cells that are usually not resolved with the conventional force measurement methods.

  12. The making of the FM value map

    DEFF Research Database (Denmark)

    2012-01-01

    Purpose: To present the FM Value Map and the background, process and considerations of its development and to reflect on perspectives and limitations. Methodology: The FM Value Map was developed from cases studies as part of the research project Facilities Management Best Practice in the Nordic...... it take the core business strategy as a starting point, and it is a fairly static framework. In spite of these limitations, the FM Value Map is an important element in the ongoing research and development in this area, but it should perhaps more be seen as a starting point rather than an end result...... in specific cases have a special importance for the value creation of FM. Research limitations: The chapter is a retrospective presentation of a research process. Originality/value: The chapter gives a detailed insight in the development process of the conceptual FM Value Map....

  13. FM research for practice in Denmark

    DEFF Research Database (Denmark)

    Jensen, Per Anker

    2012-01-01

    environment. FM started to be developed in practice with a strong focus on benchmarking and IT systems like CAFM. Around year 2000 a number of research and development project on Whole Life Costing was carried out and around 2005 there were some development projects and publications on new offices. Digital......Purpose: The purpose of this paper is to present an overview of research and development in the area of Facilities Management (FM) in Denmark. Background: Research in FM is a fairly new activity in Denmark, but there have during the 1980’s and 1990’s been a number of development activities...... on national level, which have had importance to constitute and form a professional basis for FM. Approach (Theory/Methodology): The paper provides a chronological overview of research and development activities related to FM over the last 30 years in Denmark, including CFM’s ongoing research projects. Results...

  14. FM Research for Practice in Denmark

    DEFF Research Database (Denmark)

    Jensen, Per Anker

    environment. FM started to be developed in practice with a strong focus on benchmarking and IT systems like CAFM. Around year 2000 a number of research and development project on Whole Life Costing was carried out and around 2005 there were some development projects and publications on new offices. Digital......Purpose: The purpose of this paper is to present an overview of research and development in the area of Facilities Management (FM) in Denmark. Background: Research in FM is a fairly new activity in Denmark, but there have during the 1980’s and 1990’s been a number of development activities...... on national level, which have had importance to constitute and form a professional basis for FM. Approach (Theory/Methodology): The paper provides a chronological overview of research and development activities related to FM over the last 30 years in Denmark, including CFM’s ongoing research projects. Results...

  15. A semiconductor-based, frequency-stabilized mode-locked laser using a phase modulator and an intracavity etalon.

    Science.gov (United States)

    Davila-Rodriguez, Josue; Ozdur, Ibrahim; Williams, Charles; Delfyett, Peter J

    2010-12-15

    We report a frequency-stabilized semiconductor-based mode-locked laser that uses a phase modulator and an intracavity Fabry-Perot etalon for both active mode-locking and optical frequency stabilization. A twofold multiplication of the repetition frequency of the laser is inherently obtained in the process. The residual timing jitter of the mode-locked pulse train is 13 fs (1 Hz to 100 MHz), measured after regenerative frequency division of the photodetected pulse train.

  16. Feasibility of Frequency-Modulated Wireless Transmission for a Multi-Purpose MEMS-Based Accelerometer

    Directory of Open Access Journals (Sweden)

    Alessandro Sabato

    2014-09-01

    Full Text Available Recent advances in the Micro Electro-Mechanical System (MEMS technology have made wireless MEMS accelerometers an attractive tool for Structural Health Monitoring (SHM of civil engineering structures. To date, sensors’ low sensitivity and accuracy—especially at very low frequencies—have imposed serious limitations for their application in monitoring large-sized structures. Conventionally, the MEMS sensor’s analog signals are converted to digital signals before radio-frequency (RF wireless transmission. The conversion can cause a low sensitivity to the important low-frequency and low-amplitude signals. To overcome this difficulty, the authors have developed a MEMS accelerometer system, which converts the sensor output voltage to a frequency-modulated signal before RF transmission. This is achieved by using a Voltage to Frequency Conversion (V/F instead of the conventional Analog to Digital Conversion (ADC. In this paper, a prototype MEMS accelerometer system is presented, which consists of a transmitter and receiver circuit boards. The former is equipped with a MEMS accelerometer, a V/F converter and a wireless RF transmitter, while the latter contains an RF receiver and a F/V converter for demodulating the signal. The efficacy of the MEMS accelerometer system in measuring low-frequency and low-amplitude dynamic responses is demonstrated through extensive laboratory tests and experiments on a flow-loop pipeline.

  17. An ultraviolet laser communication system using frequency-shift keying modulation scheme

    Science.gov (United States)

    Peng, Di-yong; Shi, Jun; Peng, Guang-hui; Xiao, Sha-li; Xu, Shan-he; Wang, Shan; Liu, Feng

    2015-01-01

    A communication system based on an ultraviolet (UV) laser at 266 nm is presented to improve the communication distance. The pulse frequency-shift keying (FSK) modulation scheme is studied and improved in order to reduce the bit error rate (BER), and is put into practice on a field programmable gate array (FPGA). The mathematical models of the modulation and demodulation are established. A test platform is set up to measure the energy density and pulse response under different distances and receiver elevation angles. It is shown that the omnibearing communication can be realized, and the bit rate is limited to 12.5 Mbit/s. The BER is estimated to be less than 10-7 at distance of 300 m in line-of-sight (LOS) communication model and to be less than 10-6 at distance of 80 m in non-line-of-sight (NLOS) communication model.

  18. Measurement of Frequency Shift Characteristics Based on LiNbO3 Waveguide Electro-Optic Intensity Modulator

    Institute of Scientific and Technical Information of China (English)

    Zhou Meng; Hui-Juan Zhou; Yi Liao; Qiong Yao

    2008-01-01

    High-speed and wide-band LiNbO3 waveguide electro-optic intensity modulator has drawn great attention in the field of optical fiber communi-cation and sensor. This paper reports the research results on the measurement of frequency shift character-istics of Mach-Zehnder electro-optic intensity modulator. Two measurement methods of frequency shift character-istics for high and low frequency modulations are studied in theory and experiment and demonstrate different results. The realization of a multi-wavelength optical source based on Mach-Zehnder electro-optic intensity modulator has been introduced. The technique to reach the maximum intensity for interesting shift frequency, particularly for heterodyne detection of Brillouin distributed optical fiber sensing, has been given.

  19. Frequency modulator. Transmission of meteorological signals in LVC; Modulador de frecuencia. Transmision de senales meteorologicas en CLV

    Energy Technology Data Exchange (ETDEWEB)

    Rivero G, P.T.; Ramirez S, R.; Gonzalez M, J.L.; Rojas N, P.; Celis del Angel, L. [ININ, 52750 La marquesa, Estado de Mexico (Mexico)

    2007-07-01

    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. High-purity 60GHz band millimeter-wave generation based on optically injected semiconductor laser under subharmonic microwave modulation.

    Science.gov (United States)

    Fan, Li; Xia, Guangqiong; Chen, Jianjun; Tang, Xi; Liang, Qing; Wu, Zhengmao

    2016-08-08

    Based on an optically injected semiconductor laser (OISL) operating at period-one (P1) nonlinear dynamical state, high-purity millimeter-wave generation at 60 GHz band is experimentally demonstrated via 1/4 and 1/9 subharmonic microwave modulation (the order of subharmonic is with respect to the frequency fc of the acquired 60 GHz band millimeter-wave but not the fundamental frequency f0 of P1 oscillation). Optical injection is firstly used to drive a semiconductor laser into P1 state. For the OISL operates at P1 state with a fundamental frequency f0 = 49.43 GHz, by introducing 1/4 subharmonic modulation with a modulation frequency of fm = 15.32 GHz, a 60 GHz band millimeter-wave with central frequency fc = 61.28 GHz ( = 4fm) is experimentally generated, whose linewidth is below 1.6 kHz and SSB phase noise at offset frequency 10 kHz is about -96 dBc/Hz. For fm is varied between 13.58 GHz and 16.49 GHz, fc can be tuned from 54.32 GHz to 65.96 GHz under matched modulation power Pm. Moreover, for the OISL operates at P1 state with f0 = 45.02 GHz, a higher order subharmonic modulation (1/9) is introduced into the OISL for obtaining high-purity 60 GHz band microwave signal. With (fm, Pm) = (7.23 GHz, 13.00 dBm), a microwave signal at 65.07 GHz ( = 9fm) with a linewidth below 1.6 kHz and a SSB phase noise less than -98 dBc/Hz is experimentally generated. Also, the central frequency fc can be tuned in a certain range through adjusting fm and selecting matched Pm.

  1. All-Optical Frequency Modulated High Pressure MEMS Sensor for Remote and Distributed Sensing

    DEFF Research Database (Denmark)

    Reck, Kasper; Thomsen, Erik Vilain; Hansen, Ole

    2011-01-01

    a shift in the Bragg wavelength. The simple and robust design combined with the small chip area of 1 × 1.8 mm2 makes the sensor ideally suited for remote and distributed sensing in harsh environments and where miniaturized sensors are required. The sensor is designed for high pressure applications up......We present the design, fabrication and characterization of a new all-optical frequency modulated pressure sensor. Using the tangential strain in a circular membrane, a waveguide with an integrated nanoscale Bragg grating is strained longitudinally proportional to the applied pressure causing...

  2. Velocity selective trapping of atoms in a frequency-modulated standing laser wave

    CERN Document Server

    Argonov, V Yu

    2013-01-01

    The wave function of a moderately cold atom in a stationary near-resonant standing light wave delocalizes very fast due to wave packet splitting. However, we show that frequency modulation of the field may suppress packet splitting for some atoms having specific velocities in a narrow range. These atoms remain localized in a small space for a long time. We propose that in a real experiment with cold atomic gas this effect may decrease the velocity distribution of atoms (the field traps the atoms with such specific velocities while all other atoms leave the field)

  3. Frequency-Modulated Microwave Photonic Links with Direct Detection: Review and Theory

    Science.gov (United States)

    2010-12-15

    approach for digital signals looks at an eye diagram and uses a Levenberg-Marquart optimization to maximize the eye opening. • LMSE / minimize ISI [56...FFT number o f po in t s etaMHz = param ( 3 ) ; % Frequency modulation e f f i c i e n c y in MHz/mA G = param ( 4 ) ; % RIM norma l i za t ion...in MHz/mA G = param ( 4 ) ; % RIM norma l i za t ion parameter PmW = param ( 5 ) ; % Opt i ca l power b e f o r e the f i l t e r s R = param ( 6

  4. Effect of modulation depth, frequency, and intermittence on wind turbine noise annoyance

    DEFF Research Database (Denmark)

    Ioannidou, Christina; Santurette, Sébastien; Jeong, Cheol-Ho

    2016-01-01

    Amplitude modulation (AM) may be an important factor for the perceived annoyance of wind turbine noise (WTN). Two AM types, typically referred to as “normal AM” (NAM) and “other AM” (OAM), characterize WTN AM, OAM corresponding to having intermittent periods with larger AM depth in lower frequency......, while determined from real on-site recordings, could be varied systematically. Listening tests with both original and synthesized stimuli showed that a reduction in mean AM depth across the spectrum led to a significant decrease in annoyance. When the spectrotemporal characteristics of the original far...

  5. Generating topological optical flux lattices for ultracold atoms by modulated Raman and radio-frequency couplings

    Science.gov (United States)

    Yu, Jinlong; Xu, Zhi-Fang; You, Li

    2017-01-01

    We propose a scheme to dynamically generate optical flux lattices with nontrivial band topology using amplitude-modulated Raman lasers and radio-frequency (rf) magnetic fields. By tuning the strength of Raman and rf fields, three distinct phases are realized at unit filling for a unit cell. Respectively, these three phases correspond to normal insulator, topological Chern insulator, and semimetal. Nearly nondispersive bands are found to appear in the topological phase, which promises opportunities for investigating strongly correlated quantum states within a simple cold-atom setup. The validity of our proposal is confirmed by comparing the Floquet quasienergies from the evolution operator with the spectrum of the effective Hamiltonian.

  6. First modulation of high-frequency polar mesospheric summer echoes by radio heating of the ionosphere

    Science.gov (United States)

    Senior, A.; Mahmoudian, A.; Pinedo, H.; La Hoz, C.; Rietveld, M. T.; Scales, W. A.; Kosch, M. J.

    2014-08-01

    The first high-frequency (HF, 8 MHz) observations of the modulation of polar mesospheric summer echoes (PMSE) by artificial radio heating of the ionosphere are presented and compared to observations at 224 MHz and model predictions. The experiments were performed at the European Incoherent Scatter facility in northern Norway. It is shown that model results are in qualitative and partial quantitative agreement with the observations, supporting the prediction that with certain ranges of ice particle radii and concentration, PMSE at HF radar wavelengths can be enhanced by heating due to the dominance of dust charging over plasma diffusion.

  7. High Accuracy Microwave Frequency Measurement Based on Single-Drive Dual-Parallel Mach-Zehnder Modulator

    DEFF Research Database (Denmark)

    Zhao, Ying; Deng, Lei; Pang, Xiaodan

    2011-01-01

    A novel approach for broadband microwave frequency measurement based on bias manipulation of a dual-parallel Mach-Zehnder modulator is proposed and experimentally demonstrated. A 10-3 relative error verifies a significant accuracy improvement by this method.......A novel approach for broadband microwave frequency measurement based on bias manipulation of a dual-parallel Mach-Zehnder modulator is proposed and experimentally demonstrated. A 10-3 relative error verifies a significant accuracy improvement by this method....

  8. A 750 μW 3.5–4.5 GHz FM-UWB transmitter

    Directory of Open Access Journals (Sweden)

    Mohamed Ali

    2015-05-01

    Full Text Available This paper presents an ultra-low power frequency modulated ultra-wideband (FM-UWB transmitter implemented in standard 130 nm CMOS technology. The transmitter operates in the range of 3.5–4.5 GHz with 4 GHz RF carrier frequency. The transmitter can accept input data rates up to 250 kbps. A relaxation oscillator is used to generate the subcarrier signal and a VCO for RF carrier generation. The center frequency of the VCO is periodically calibrated to avoid out of band operation. An integer-N phase-locked loop (PLL is used for both subcarrier generation and RF VCO calibration, which needs only 500 ns to complete the calibration. A class-AB power amplifier is used to output the power under the FCC mask. The proposed FM-UWB transmitter consumes 750 μW from a 1.2 V supply.

  9. High-frequency modulated signals of killer whales (Orcinus orca) in the North Pacific.

    Science.gov (United States)

    Simonis, Anne E; Baumann-Pickering, Simone; Oleson, Erin; Melcón, Mariana L; Gassmann, Martin; Wiggins, Sean M; Hildebrand, John A

    2012-04-01

    Killer whales in the North Pacific, similar to Atlantic populations, produce high-frequency modulated signals, based on acoustic recordings from ship-based hydrophone arrays and autonomous recorders at multiple locations. The median peak frequency of these signals ranged from 19.6-36.1 kHz and median duration ranged from 50-163 ms. Source levels were 185-193 dB peak-to-peak re: 1 μPa at 1 m. These uniform, repetitive, down-swept signals are similar to bat echolocation signals and possibly could have echolocation functionality. A large geographic range of occurrence suggests that different killer whale ecotypes may utilize these signals.

  10. Effect of modulation depth, frequency, and intermittence on wind turbine noise annoyance.

    Science.gov (United States)

    Ioannidou, Christina; Santurette, Sébastien; Jeong, Cheol-Ho

    2016-03-01

    Amplitude modulation (AM) may be an important factor for the perceived annoyance of wind turbine noise (WTN). Two AM types, typically referred to as "normal AM" (NAM) and "other AM" (OAM), characterize WTN AM, OAM corresponding to having intermittent periods with larger AM depth in lower frequency regions than NAM. The extent to which AM depth, frequency, and type affect WTN annoyance remains uncertain. Moreover, the temporal variations of WTN AM have often not been considered. Here, realistic stimuli accounting for such temporal variations were synthesized such that AM depth, frequency, and type, while determined from real on-site recordings, could be varied systematically. Listening tests with both original and synthesized stimuli showed that a reduction in mean AM depth across the spectrum led to a significant decrease in annoyance. When the spectrotemporal characteristics of the original far-field stimuli and the temporal AM variations were taken into account, the effect of AM frequency remained limited and the presence of intermittent OAM periods did not affect annoyance. These findings suggest that, at a given overall level, the AM depth of NAM periods is the most crucial AM parameter for WTN annoyance.

  11. Development of GaAs Gunn Diodes and Their Applications to Frequency Modulated Continuous Wave Radar

    Science.gov (United States)

    Choi, Seok-Gyu; Han, Min; Baek, Yong-Hyun; Ko, Dong-Sik; Baek, Tae-Jong; Lee, Sang-Jin; Kim, Jin-Ho; Lee, Seong-Dae; Kim, Mi-Ra; Chae, Yeon-Sik; Kathalingam, Adaikalam; Rhee, Jin-Koo

    2010-11-01

    In this work, we have designed and fabricated the GaAs Gunn diodes for a 94 GHz waveguide voltage controlled oscillator (VCO) which is one of the important parts in a frequency modulated continuous wave (FMCW) radar application. For fabrication of the high power GaAs Gunn diodes, we adopted a graded gap injector which enhances the output power and conversion efficiency by effectively removing the dead-zone. We have measured RF characteristics of the fabricated GaAs Gunn diodes. The operating current, oscillation frequency, and output power of the fabricated GaAs Gunn diodes are presented as a function of the anode diameters. The operating current increases with anode diameters, whereas the oscillation frequency decreases. The higher oscillation frequency was obtained from 60 µm anode diameters of the fabricated Gunn GaAs diodes and higher power was obtained from 68 µm. Also, for application of the 94 GHz FMCW radar system, we have fabricated the 94 GHz waveguide VCO. From the fabricated GaAs Gunn diodes of anode diameter of 60 µm, we have obtained the improved VCO performance.

  12. Network-state modulation of power-law frequency-scaling in visual cortical neurons.

    Science.gov (United States)

    El Boustani, Sami; Marre, Olivier; Béhuret, Sébastien; Baudot, Pierre; Yger, Pierre; Bal, Thierry; Destexhe, Alain; Frégnac, Yves

    2009-09-01

    Various types of neural-based signals, such as EEG, local field potentials and intracellular synaptic potentials, integrate multiple sources of activity distributed across large assemblies. They have in common a power-law frequency-scaling structure at high frequencies, but it is still unclear whether this scaling property is dominated by intrinsic neuronal properties or by network activity. The latter case is particularly interesting because if frequency-scaling reflects the network state it could be used to characterize the functional impact of the connectivity. In intracellularly recorded neurons of cat primary visual cortex in vivo, the power spectral density of V(m) activity displays a power-law structure at high frequencies with a fractional scaling exponent. We show that this exponent is not constant, but depends on the visual statistics used to drive the network. To investigate the determinants of this frequency-scaling, we considered a generic recurrent model of cortex receiving a retinotopically organized external input. Similarly to the in vivo case, our in computo simulations show that the scaling exponent reflects the correlation level imposed in the input. This systematic dependence was also replicated at the single cell level, by controlling independently, in a parametric way, the strength and the temporal decay of the pairwise correlation between presynaptic inputs. This last model was implemented in vitro by imposing the correlation control in artificial presynaptic spike trains through dynamic-clamp techniques. These in vitro manipulations induced a modulation of the scaling exponent, similar to that observed in vivo and predicted in computo. We conclude that the frequency-scaling exponent of the V(m) reflects stimulus-driven correlations in the cortical network activity. Therefore, we propose that the scaling exponent could be used to read-out the "effective" connectivity responsible for the dynamical signature of the population signals measured

  13. Network-state modulation of power-law frequency-scaling in visual cortical neurons.

    Directory of Open Access Journals (Sweden)

    Sami El Boustani

    2009-09-01

    Full Text Available Various types of neural-based signals, such as EEG, local field potentials and intracellular synaptic potentials, integrate multiple sources of activity distributed across large assemblies. They have in common a power-law frequency-scaling structure at high frequencies, but it is still unclear whether this scaling property is dominated by intrinsic neuronal properties or by network activity. The latter case is particularly interesting because if frequency-scaling reflects the network state it could be used to characterize the functional impact of the connectivity. In intracellularly recorded neurons of cat primary visual cortex in vivo, the power spectral density of V(m activity displays a power-law structure at high frequencies with a fractional scaling exponent. We show that this exponent is not constant, but depends on the visual statistics used to drive the network. To investigate the determinants of this frequency-scaling, we considered a generic recurrent model of cortex receiving a retinotopically organized external input. Similarly to the in vivo case, our in computo simulations show that the scaling exponent reflects the correlation level imposed in the input. This systematic dependence was also replicated at the single cell level, by controlling independently, in a parametric way, the strength and the temporal decay of the pairwise correlation between presynaptic inputs. This last model was implemented in vitro by imposing the correlation control in artificial presynaptic spike trains through dynamic-clamp techniques. These in vitro manipulations induced a modulation of the scaling exponent, similar to that observed in vivo and predicted in computo. We conclude that the frequency-scaling exponent of the V(m reflects stimulus-driven correlations in the cortical network activity. Therefore, we propose that the scaling exponent could be used to read-out the "effective" connectivity responsible for the dynamical signature of the population

  14. Accurate displacement-measuring interferometer with wide range using an I2 frequency-stabilized laser diode based on sinusoidal frequency modulation

    Science.gov (United States)

    Vu, Thanh-Tung; Higuchi, Masato; Aketagawa, Masato

    2016-10-01

    We propose the use of the sinusoidal frequency modulation technique to improve both the frequency stability of an external cavity laser diode (ECLD) and the measurement accuracy and range of a displacement-measuring interferometer. The frequency of the ECLD was modulated at 300 kHz by modulating the injection current, and it was locked to the b21 hyperfine component of the transition 6-3, P(33), 127I2 (633 nm) by the null method. A relative frequency stability of 6.5  ×  10-11 was achieved at 100 s sampling time. The stabilized ECLD was then utilized as a light source for an unbalanced Michelson interferometer. In the interferometer, the displacement and direction of the target mirror can be determined using a Lissajous diagram based on two consecutive and quadrant-phase harmonics of the interference signal. Generally, the measurement range of the interferometer by the proposed method is limited by the modulation index and the signal-to-noise ratio of the harmonics. To overcome this drawback, suitable consecutive harmonic pairs were selected for the specific measurement ranges to measure the displacement. The displacements determined in the specific ranges by the proposed method were compared with those observed by a commercial capacitive sensor. From the comparison, the proposed method has high precision to determine the displacement. The measurement range was also extended up to 10 m by selecting a suitable modulation index and suitable consecutive pairs of harmonics.

  15. Spin Biochemistry Modulates Reactive Oxygen Species (ROS) Production by Radio Frequency Magnetic Fields

    Science.gov (United States)

    Usselman, Robert J.; Hill, Iain; Singel, David J.; Martino, Carlos F.

    2014-01-01

    The effects of weak magnetic fields on the biological production of reactive oxygen species (ROS) from intracellular superoxide (O2•−) and extracellular hydrogen peroxide (H2O2) were investigated in vitro with rat pulmonary arterial smooth muscle cells (rPASMC). A decrease in O2•− and an increase in H2O2 concentrations were observed in the presence of a 7 MHz radio frequency (RF) at 10 μTRMS and static 45 μT magnetic fields. We propose that O2•− and H2O2 production in some metabolic processes occur through singlet-triplet modulation of semiquinone flavin (FADH•) enzymes and O2•− spin-correlated radical pairs. Spin-radical pair products are modulated by the 7 MHz RF magnetic fields that presumably decouple flavin hyperfine interactions during spin coherence. RF flavin hyperfine decoupling results in an increase of H2O2 singlet state products, which creates cellular oxidative stress and acts as a secondary messenger that affects cellular proliferation. This study demonstrates the interplay between O2•− and H2O2 production when influenced by RF magnetic fields and underscores the subtle effects of low-frequency magnetic fields on oxidative metabolism, ROS signaling, and cellular growth. PMID:24681944

  16. Use of Nonlinear Frequency Modulated Signals for the Enhancement of Subharmonic Response from Contrast Microbubbles

    Directory of Open Access Journals (Sweden)

    MUHAMMAD ARIF

    2017-01-01

    Full Text Available Ultrasound imaging with the subharmonic component from contrast microbubbles provide improved CTR (Contrast-to-Tissue Ratio, however it is susceptible to the low amplitude of the subharmonic component. In this simulation study, NLFM (Nonlinear Frequency Modulated signals are proposed in order to enhance the subharmonic response from microbubbles. NLFM signals having fractional bandwidths of 10, 20, and 40% with up and down sweeps were used as excitation. The performance of NLFM signals were compared with the reference tone-burst and LFM (Linear Frequency Modulated signals. The results show that the ultrasound contrast microbubbles can produce subharmonic response which is dependent on the applied signal pressure and bandwidth. It is observed that the subharmonic component of the scattered NLFM signal is 3.2dB higher than the LFM signal, whereas it is 9dB higher compared to the sinusoidal tone-burst signal. The results are also presented which show that the up and down sweeps NLFM signals performed better than the LFM signals at the same acoustic pressure and bandwidth.

  17. Spin biochemistry modulates reactive oxygen species (ROS production by radio frequency magnetic fields.

    Directory of Open Access Journals (Sweden)

    Robert J Usselman

    Full Text Available The effects of weak magnetic fields on the biological production of reactive oxygen species (ROS from intracellular superoxide (O2•- and extracellular hydrogen peroxide (H2O2 were investigated in vitro with rat pulmonary arterial smooth muscle cells (rPASMC. A decrease in O2•- and an increase in H2O2 concentrations were observed in the presence of a 7 MHz radio frequency (RF at 10 μTRMS and static 45 μT magnetic fields. We propose that O2•- and H2O2 production in some metabolic processes occur through singlet-triplet modulation of semiquinone flavin (FADH• enzymes and O2•- spin-correlated radical pairs. Spin-radical pair products are modulated by the 7 MHz RF magnetic fields that presumably decouple flavin hyperfine interactions during spin coherence. RF flavin hyperfine decoupling results in an increase of H2O2 singlet state products, which creates cellular oxidative stress and acts as a secondary messenger that affects cellular proliferation. This study demonstrates the interplay between O2•- and H2O2 production when influenced by RF magnetic fields and underscores the subtle effects of low-frequency magnetic fields on oxidative metabolism, ROS signaling, and cellular growth.

  18. Developing and integrating a computer-based AM/FM radio station

    Directory of Open Access Journals (Sweden)

    Everardo Inzunza González

    2010-06-01

    Full Text Available This article presents the development of a personal computer based AM/FM radio station operating on the AM/FM commercial band. Developing the graphical user interface for the software and the interconnection with an RF function generator by means of a GPIB is presented. Computer users can enter the desired transmission frequency within the commercial band as well as the transmission potency.

  19. Design and Implementation of FM Wave Generator Base on FPGA%基于FPGA的FM信号发生器设计与实现

    Institute of Scientific and Technical Information of China (English)

    左盼盼; 赛景波

    2016-01-01

    In order to improve the frequency accuracy and stability of the FM signal generator,and make it relevant technical parameters adjustable,a method is designed based on FPGA and Direct Digital Synthesizer(DDS)technol⁃ogy. The system achieves adjustable FM signal modulation parameters by the PC,and through the PCIE interfaceFM signal control word is transferred to the FPGA,FPGA controls the integrated DDS core to achieve the FM signal gen⁃eration. Test results show that the frequency of FM signal has high frequency accuracy and stability,the maximum output of the carrier frequency can reach 40 MHz,and the amplitude accuracy can reach 5 mV. The FM signal gener⁃ator has a broad application space in software radio,radar target feature identification and radar detection distance and other fields.%为提高FM信号发生器的频率准确度和稳定度,并使其相关技术参数可调,设计了一种基于FPGA和直接数字频率合成(DDS)技术的产生方法。系统通过上位机设置FM信号的调制参数,通过PCIE接口将上位机设置的FM信号控制字传给FPGA,FPGA内部通过控制DDS核来实现FM信号的产生。测试结果表明,FM信号的频率精度高且稳定性好,最高输出载波频率达40 MHz,幅度精度能达到5 mV。该FM信号发生器在软件无线电、雷达目标特征识别和雷达距离探测等领域具有广阔的应用空间。

  20. Time and frequency-dependent modulation of local field potential synchronization by deep brain stimulation.

    Directory of Open Access Journals (Sweden)

    Clinton B McCracken

    Full Text Available High-frequency electrical stimulation of specific brain structures, known as deep brain stimulation (DBS, is an effective treatment for movement disorders, but mechanisms of action remain unclear. We examined the time-dependent effects of DBS applied to the entopeduncular nucleus (EP, the rat homolog of the internal globus pallidus, a target used for treatment of both dystonia and Parkinson's disease (PD. We performed simultaneous multi-site local field potential (LFP recordings in urethane-anesthetized rats to assess the effects of high-frequency (HF, 130 Hz; clinically effective, low-frequency (LF, 15 Hz; ineffective and sham DBS delivered to EP. LFP activity was recorded from dorsal striatum (STR, ventroanterior thalamus (VA, primary motor cortex (M1, and the stimulation site in EP. Spontaneous and acute stimulation-induced LFP oscillation power and functional connectivity were assessed at baseline, and after 30, 60, and 90 minutes of stimulation. HF EP DBS produced widespread alterations in spontaneous and stimulus-induced LFP oscillations, with some effects similar across regions and others occurring in a region- and frequency band-specific manner. Many of these changes evolved over time. HF EP DBS produced an initial transient reduction in power in the low beta band in M1 and STR; however, phase synchronization between these regions in the low beta band was markedly suppressed at all time points. DBS also enhanced low gamma synchronization throughout the circuit. With sustained stimulation, there were significant reductions in low beta synchronization between M1-VA and STR-VA, and increases in power within regions in the faster frequency bands. HF DBS also suppressed the ability of acute EP stimulation to induce beta oscillations in all regions along the circuit. This dynamic pattern of synchronizing and desynchronizing effects of EP DBS suggests a complex modulation of activity along cortico-BG-thalamic circuits underlying the therapeutic

  1. Generation of ultrahigh frequency air microplasma in a magnetic loop and effects of pulse modulation on operation

    Science.gov (United States)

    Taghioskoui, Mazdak; Perlow, Joshua; Zaghloul, Mona; Montaser, Akbar

    2010-05-01

    An atmospheric pressure air microplasma (APAMP) source was developed under ambient conditions using a magnetic loop at an operating frequency of 740 MHz. A self-igniting, stable APAMP was generated at 9.5 W. Pulse modulation (PM) was applied to the ultra high frequency signal. The effects of PM on self-ignition and operation of the APAMP source were studied by using a square wave modulating signal in the frequency range of 5-30 KHz. With the application of PM on the APAMP, in the best case, the plasma self-ignites and is sustained at 2.5 W.

  2. Mode-locking and Q-switching in multi-wavelength fiber ring laser using low frequency phase modulation.

    Science.gov (United States)

    Jun, Chang Su; Kim, Byoung Yoon

    2011-03-28

    We describe experimental investigation of pulsed output from a multi-wavelength fiber ring laser incorporating low frequency phase modulation with large modulation amplitude. The Erbium-doped fiber (EDF) ring laser generated more than 8 wavelength channels with the help of a phase modulator operating at 26.2 kHz and a periodic intra-cavity filter. For most cases, the laser output is pulsed in the form of mode-locking at 5.62 MHz and/or Q-switching at harmonic and sub-harmonic of the phase modulation frequency. Chaotic pulse output is also observed. The behavior of the output pulses are described as functions of pump power and phase modulation amplitude. The relative intensity noise (RIN) value of a single wavelength channel is measured to be under -100 dB/Hz (-140 dB/Hz beyond 1.5 GHz).

  3. 40-Gbps vestigial sideband half-cycle Nyquist subcarrier modulation transmission experiment and its comparison with orthogonal frequency division multiplexing

    Science.gov (United States)

    Liu, Na; Chen, Xue; Ju, Cheng; Hui, Rongqing

    2014-09-01

    We experimentally demonstrate the superior performance of a 40-Gbps 16-QAM half-cycle Nyquist subcarrier modulation (SCM) transmission over a 100-km uncompensated standard single-mode fiber using dual-drive Mach-Zehnder modulator-based vestigial sideband intensity modulation and direct detection. The impact of modulator chirp on the system performance is experimentally evaluated. This Nyquist-SCM technique is compared with optical orthogonal frequency division multiplexing in both back-to-back and 100-km transmission experiments, and the results show that the Nyquist system has a better performance.

  4. Ultrafast modulation of the plasma frequency of vertically aligned indium tin oxide rods.

    Science.gov (United States)

    Tice, Daniel B; Li, Shi-Qiang; Tagliazucchi, Mario; Buchholz, D Bruce; Weiss, Emily A; Chang, Robert P H

    2014-03-12

    Light-matter interaction at the nanoscale is of particular interest for future photonic integrated circuits and devices with applications ranging from communication to sensing and imaging. In this Letter a combination of transient absorption (TA) and the use of third harmonic generation as a probe (THG-probe) has been adopted to investigate the response of the localized surface plasmon resonances (LSPRs) of vertically aligned indium tin oxide rods (ITORs) upon ultraviolet light (UV) excitation. TA experiments, which are sensitive to the extinction of the LSPR, show a fluence-dependent increase in the frequency and intensity of the LSPR. The THG-probe experiments show a fluence-dependent decrease of the LSPR-enhanced local electric field intensity within the rod, consistent with a shift of the LSPR to higher frequency. The kinetics from both TA and THG-probe experiments are found to be independent of the fluence of the pump. These results indicate that UV excitation modulates the plasma frequency of ITO on the ultrafast time scale by the injection of electrons into, and their subsequent decay from, the conduction band of the rods. Increases to the electron concentration in the conduction band of ∼13% were achieved in these experiments. Computer simulation and modeling have been used throughout the investigation to guide the design of the experiments and to map the electric field distribution around the rods for interpreting far-field measurement results.

  5. Separation of overlapping linear frequency modulated (LFM) signals using the fractional fourier transform.

    Science.gov (United States)

    Cowell, David M J; Freear, Steven

    2010-10-01

    Linear frequency modulated (LFM) excitation combined with pulse compression provides an increase in SNR at the receiver. LFM signals are of longer duration than pulsed signals of the same bandwidth; consequently, in many practical situations, maintaining temporal separation between echoes is not possible. Where analysis is performed on individual LFM signals, a separation technique is required. Time windowing is unable to separate signals overlapping in time. Frequency domain filtering is unable to separate signals with overlapping spectra. This paper describes a method to separate time-overlapping LFM signals through the application of the fractional Fourier transform (FrFT), a transform operating in both time and frequency domains. A short introduction to the FrFT and its operation and calculation are presented. The proposed signal separation method is illustrated by application to a simulated ultrasound signal, created by the summation of multiple time-overlapping LFM signals and the component signals recovered with ±0.6% spectral error. The results of an experimental investigation are presented in which the proposed separation method is applied to time-overlapping LFM signals created by the transmission of a LFM signal through a stainless steel plate and water-filled pipe.

  6. Compact high voltage, high peak power, high frequency transformer for converter type modulator applications.

    Science.gov (United States)

    Reghu, T; Mandloi, V; Shrivastava, Purushottam

    2016-04-01

    The design and development of a compact high voltage, high peak power, high frequency transformer for a converter type modulator of klystron amplifiers is presented. The transformer has been designed to operate at a frequency of 20 kHz and at a flux swing of ±0.6 T. Iron (Fe) based nanocrystalline material has been selected as a core for the construction of the transformer. The transformer employs a specially designed solid Teflon bobbin having 120 kV insulation for winding the high voltage secondary windings. The flux swing of the core has been experimentally found by plotting the hysteresis loop at actual operating conditions. Based on the design, a prototype transformer has been built which is per se a unique combination of high voltage, high frequency, and peak power specifications. The transformer was able to provide 58 kV (pk-pk) at the secondary with a peak power handling capability of 700 kVA. The transformation ratio was 1:17. The performance of the transformer is also presented and discussed.

  7. Extended-bandwidth frequency sweeps of a distributed feedback laser using combined injection current and temperature modulation

    Science.gov (United States)

    Hefferman, Gerald; Chen, Zhen; Wei, Tao

    2017-07-01

    This article details the generation of an extended-bandwidth frequency sweep using a single, communication grade distributed feedback (DFB) laser. The frequency sweep is generated using a two-step technique. In the first step, injection current modulation is employed as a means of varying the output frequency of a DFB laser over a bandwidth of 99.26 GHz. A digital optical phase lock loop is used to lock the frequency sweep speed during current modulation, resulting in a linear frequency chirp. In the second step, the temperature of the DFB laser is modulated, resulting in a shifted starting laser output frequency. A laser frequency chirp is again generated beginning at this shifted starting frequency, resulting in a frequency-shifted spectrum relative to the first recorded data. This process is then repeated across a range of starting temperatures, resulting in a series of partially overlapping, frequency-shifted spectra. These spectra are then aligned using cross-correlation and combined using averaging to form a single, broadband spectrum with a total bandwidth of 510.9 GHz. In order to investigate the utility of this technique, experimental testing was performed in which the approach was used as the swept-frequency source of a coherent optical frequency domain reflectometry system. This system was used to interrogate an optical fiber containing a 20 point, 1-mm pitch length fiber Bragg grating, corresponding to a period of 100 GHz. Using this technique, both the periodicity of the grating in the frequency domain and the individual reflector elements of the structure in the time domain were resolved, demonstrating the technique's potential as a method of extending the sweeping bandwidth of semiconductor lasers for frequency-based sensing applications.

  8. The Blazhko modulation of TV Boo in 2010

    CERN Document Server

    Hajdu, G; Sódor, Á; Szeidl, B; Smitola, P; Belucz, B; Posztobányi, K; Vida, K; Kun, E

    2012-01-01

    We present the analysis of the multicolour CCD observations in the 2010 season of the Blazhko RRc star TV Boo. TV Boo shows a complex Blazhko modulation dominated by two independent modulations with P_{fm1}=9.74 d and P_{fm2}=21.43 d long periods. Both modulation components appear in the frequency spectra as multiplet structures around the harmonics of the pulsation. The positive value of the asymmetry parameter (Q=+0.51) of the primary modulation suggests that it is similar in its character to the Blazhko effect of most of the modulated RRab stars. Interestingly, the secondary, lower-amplitude modulation exhibits a negative asymmetry parameter (Q=-0.22), which is an unusually low value when compared to the Blazhko-modulated RRab stars. Apart from the two modulation frequencies, the spectra also show an additional frequency f' and its linear combinations with the pulsation and the primary modulation f_{1}+f' and f_{1}-f'-f_{m1}. We conclude that the additional frequency most probably belongs to a non-radial m...

  9. Frequency locking to a high-finesse Fabry-Perot cavity of a Frequency doubled Nd YAG laser used as the optical phase modulator

    CERN Document Server

    Bregant, M; Valle, F D; Ruoso, G; Zavattini, G

    2002-01-01

    We report on the frequency locking of a frequency doubled Nd:YAG laser to a 45 000 finesse, 87-cm-long, Fabry-Perot cavity using a modified form of the Pound-Drever-Hall technique. Necessary signals, such as light phase modulation and frequency correction feedback, are fed direcly to the infrared pump laser. This is sufficient to achieve a stable locking of the 532 nm visible beam to the cavity, also showing that the doubling process does not degrade laser performances.

  10. DARC servis konvencionalne FM radio-difuzije / DARC service conventional FM radio broadcasting

    Directory of Open Access Journals (Sweden)

    Mladen Manjak

    2006-07-01

    Full Text Available Konvencionalna FM radio-difuzija može ponuditi dodatne servise uz pomoć podnosioca smještenih u slobodnom dijelu osnovnog opsega multipleksiranog signala. U radu su prikazane osnovne karakteristike DARC servisa FM radio-difuzije i njegove moguće primjene. / Conventional FM radio broadcasting can offer additional services by means of a subcarrier placed in a clear part of the beseband multiplex signal. This paper contains elementary characteristics of DARC service conventional FM radio broadcasting and possible applications.

  11. Model-based review of Doppler global velocimetry techniques with laser frequency modulation

    Science.gov (United States)

    Fischer, Andreas

    2017-06-01

    Optical measurements of flow velocity fields are of crucial importance to understand the behavior of complex flow. One flow field measurement technique is Doppler global velocimetry (DGV). A large variety of different DGV approaches exist, e.g., applying different kinds of laser frequency modulation. In order to investigate the measurement capabilities especially of the newer DGV approaches with laser frequency modulation, a model-based review of all DGV measurement principles is performed. The DGV principles can be categorized by the respective number of required time steps. The systematic review of all DGV principle reveals drawbacks and benefits of the different measurement approaches with respect to the temporal resolution, the spatial resolution and the measurement range. Furthermore, the Cramér-Rao bound for photon shot is calculated and discussed, which represents a fundamental limit of the achievable measurement uncertainty. As a result, all DGV techniques provide similar minimal uncertainty limits. With Nphotons as the number of scattered photons, the minimal standard deviation of the flow velocity reads about 106 m / s /√{Nphotons } , which was calculated for a perpendicular arrangement of the illumination and observation direction and a laser wavelength of 895 nm. As a further result, the signal processing efficiencies are determined with a Monte-Carlo simulation. Except for the newest correlation-based DGV method, the signal processing algorithms are already optimal or near the optimum. Finally, the different DGV approaches are compared regarding errors due to temporal variations of the scattered light intensity and the flow velocity. The influence of a linear variation of the scattered light intensity can be reduced by maximizing the number of time steps, because this means to acquire more information for the correction of this systematic effect. However, more time steps can result in a flow velocity measurement with a lower temporal resolution

  12. Dual-beam ELF wave generation as a function of power, frequency, modulation waveform, and receiver location

    Science.gov (United States)

    Agrawal, D.; Moore, R. C.

    2012-12-01

    Dual-beam ELF wave generation experiments performed at the High-frequency Active Auroral Research Program (HAARP) HF transmitter are used to investigate the dependence of the generated ELF wave magnitude on HF power, HF frequency, modulation waveform, and receiver location. During the experiments, two HF beams transmit simultaneously: one amplitude modulated (AM) HF beam modulates the conductivity of the lower ionosphere at ELF frequencies while a second HF beam broadcasts a continuous waveform (CW) signal, modifying the efficiency of ELF conductivity modulation and thereby the efficiency of ELF wave generation. We report experimental results for different ambient ionospheric conditions, and we interpret the observations in the context of a newly developed dual-beam HF heating model. A comparison between model predictions and experimental observations indicates that the theoretical model includes the essential physics involved in multifrequency HF heating of the lower ionosphere. In addition to the HF transmission parameters mentioned above, the model is used to predict the dependence of ELF wave magnitude on the polarization of the CW beam and on the modulation frequency of the modulated beam. We consider how these effects vary with ambientD-region electron density and electron temperature.

  13. Generation of coherent and frequency-lock multi-carriers using cascaded phase modulators and recirculating frequency shifter for Tb/s optical communication.

    Science.gov (United States)

    Zhang, Junwen; Chi, Nan; Yu, Jianjun; Shao, Yufeng; Zhu, Jiangbo; Huang, Bo; Tao, Li

    2011-07-04

    We investigate to generate coherent and frequency-lock optical multi-carriers by using cascaded phase modulators and recirculating frequency shifter (RFS) based on an EDFA loop. The phase and amplitude relation of RF signals on two cascaded phase modulators and the impact of EDFA gain are investigated. Experimental results are in good agreement with the theoretical analysis. The performance of 113 coherent and frequency-lock subcarriers with tone-to-noise ratio larger than 26dB and amplitude difference of 5dB obtained after a tilt filter covering totally 22.6nm shows that this scheme is a promising technique for the coming Tb/s optical communication.

  14. Thinking outside the box when reading aloud: Between (localist) module connection strength as a source of word frequency effects.

    Science.gov (United States)

    Besner, Derek; Risko, Evan F

    2016-10-01

    The frequency with which words appear in print is a powerful predictor of the time to read monosyllabic words aloud, and consequently all models of reading aloud provide an explanation for this effect. The entire class of localist accounts assumes that the effect of word frequency arises because the mental lexicon is organized around frequency of occurrence (the action is inside the lexical boxes). We propose instead that the frequency of occurrence effect is better understood in terms of the hypothesis that the strength of between module connections varies as a function of word frequency. Findings from 3 different lines of investigation (experimental and computational) are difficult to understand in terms of the "within lexicon" account, but are consistent with the strength of between-module connections account. (PsycINFO Database Record

  15. Generation of tunable, high repetition rate frequency combs with equalized spectra using carrier injection based silicon modulators

    Science.gov (United States)

    Nagarjun, K. P.; Selvaraja, Shankar Kumar; Supradeepa, V. R.

    2016-03-01

    High repetition-rate frequency combs with tunable repetition rate and carrier frequency are extensively used in areas like Optical communications, Microwave Photonics and Metrology. A common technique for their generation is strong phase modulation of a CW-laser. This is commonly implemented using Lithium-Niobate based modulators. With phase modulation alone, the combs have poor spectral flatness and significant number of missing lines. To overcome this, a complex cascade of multiple intensity and phase modulators are used. A comb generator on Silicon based on these principles is desirable to enable on-chip integration with other functionalities while reducing power consumption and footprint. In this work, we analyse frequency comb generation in carrier injection based Silicon modulators. We observe an interesting effect in these comb generators. Enhanced absorption accompanying carrier injection, an undesirable effect in data modulators, shapes the amplitude here to enable high quality combs from a single modulator. Thus, along with reduced power consumption to generate a specific number of lines, the complexity has also been significantly reduced. We use a drift-diffusion solver and mode solver (Silvaco TCAD) along with Soref-Bennett relations to calculate the variations in refractive indices and absorption of an optimized Silicon PIN - waveguide modulator driven by an unbiased high frequency (10 Ghz) voltage signal. Our simulations demonstrate that with a device length of 1 cm, a driving voltage of 2V and minor shaping with a passive ring-resonator filter, we obtain 37 lines with a flatness better than 5-dB across the band and power consumption an order of magnitude smaller than Lithium-Niobate modulators.

  16. Direct observation of frequency modulated transcription in single cells using light activation

    Science.gov (United States)

    Larson, Daniel R; Fritzsch, Christoph; Sun, Liang; Meng, Xiuhau; Lawrence, David S; Singer, Robert H

    2013-01-01

    Single-cell analysis has revealed that transcription is dynamic and stochastic, but tools are lacking that can determine the mechanism operating at a single gene. Here we utilize single-molecule observations of RNA in fixed and living cells to develop a single-cell model of steroid-receptor mediated gene activation. We determine that steroids drive mRNA synthesis by frequency modulation of transcription. This digital behavior in single cells gives rise to the well-known analog dose response across the population. To test this model, we developed a light-activation technology to turn on a single steroid-responsive gene and follow dynamic synthesis of RNA from the activated locus. DOI: http://dx.doi.org/10.7554/eLife.00750.001 PMID:24069527

  17. Imaging system of wavelet optics described by the Gaussian linear frequency-modulated complex wavelet

    Science.gov (United States)

    Tan, Liying; Ma, Jing; Wang, Guangming

    2005-12-01

    The image formation and the point-spread function of an optical system are analyzed by use of the wavelet basis function. The image described by a wavelet is no longer an indivisible whole image. It is, rather, a complex image consisting of many wavelet subimages, which come from the changes of different parameters (scale) a and c, and parameters b and d show the positions of wavelet subimages under different scales. A Gaussian frequency-modulated complex-valued wavelet function is introduced to express the point-spread function of an optical system and used to describe the image formation. The analysis, in allusion to the situation of illumination with a monochromatic plain light wave, shows that using the theory of wavelet optics to describe the image formation of an optical system is feasible.

  18. Input current interharmonics in adjustable speed drives caused by fixed-frequency modulation techniques

    DEFF Research Database (Denmark)

    Soltani, Hamid; Davari, Pooya; Loh, Poh Chiang

    2016-01-01

    Adjustable Speed Drives (ASDs) based on double-stage conversion systems may inject interharmonics distortion into the grid, other than the well-known characteristic harmonic components. The problems created by interharmonics make it necessary to find their precise sources, and, to adopt an approp......Adjustable Speed Drives (ASDs) based on double-stage conversion systems may inject interharmonics distortion into the grid, other than the well-known characteristic harmonic components. The problems created by interharmonics make it necessary to find their precise sources, and, to adopt...... an appropriate strategy for minimizing their effects. This paper investigates the ASD's input current interharmonic sources caused by applying symmetrical regularly sampled fixed-frequency modulation techniques on the inverter. The interharmonics generation process is precisely formulated and comparative results...

  19. A pulse-frequency modulation sensor using memristive-based inhibitory interconnections.

    Science.gov (United States)

    Kavehei, Omid; Lee, Sang-Jin; Cho, Kyoung-Rok; Al-Sarawi, Said; Abbott, Derek

    2013-05-01

    This paper proposes a programmable inhibitory interconnection network between pixels in an array of novel low-voltage Schmitt-trigger-based PFM sensors that will be of interest for future applications in memristor-based early vision processing. In addition, a new low-power inverter-based pulse-frequency modulation (PFM) design and its integration with the network is also presented. To ensure no change in the memristors conductance in the network, the CMOS imager was designed for low voltage operation. That has resulted in a significant power reduction, better than 60%, and a comparable linear dynamic range when compared to published designs in the literature. The design was performed using a 0.13 um Samsung Electronics standard CMOS process, using 0.75 V supply voltage.

  20. Electrosmog prevention in office buildings. Frequency modulators prevent electrosmog; Raumentstoerung in Buerogebaeuden. Mit Frequenzmodulatoren gegen Elektrosmog

    Energy Technology Data Exchange (ETDEWEB)

    Schmid, W. [Technische Gebaeudeausruestung, Muenchen (Germany)

    2002-07-01

    Experts agree that electrosmog is caused by radiocommunication, electronic and electric equipment at the place of work and call for minimisation of radiation. IPR Stuttgart, a subsidiary of Drees and Sommer, Stuttgart, reduces electrosmog in office buildings with the aid of frequency modulators. [German] Noch vor wenigen Jahren galt die Klimaanlage gemeinhin als Hauptverursacher von Muedigkeit, Kopfschmerzen und Konzentrationsschwaeche. Mit dem Trend zu Kuehldecken, Quell-Lueftung, Bauteiltemperierung und Oeko-Klimaanlagen hat die Akzeptanz raumlufttechnischer Anlagen spuerbar zugenommen. Viele buerotypischen Beschwerden sind allerdings geblieben. Experten sind sich darueber einig, dass dafuer in erster Linie Elektrosmog durch Mobilfunk, elektronische Geraete und Elektrosysteme verantwortlich sind und fordern eine Minimierung der Strahlenbelastung am Arbeitsplatz. Das Institut fuer physikalische Raumentstoerung (IPR), eine Tochtergesellschaft des Projektentwicklers Drees and Sommer, Stuttgart, hat sich jetzt zur Aufgabe gemacht, Gebaeude und deren technische Ausstattung mit Hilfe von Frequenzmodulatoren physikalischen zu entstoeren. (orig.)

  1. Spectral characterization of integrated acousto-optic tunable filters by means of laser frequency modulation spectroscopy.

    Science.gov (United States)

    Di Maio, Antonio; Salza, Mario; Gagliardi, Gianluca; Ferraro, Pietro; De Natale, Paolo

    2006-12-20

    The spectral characteristics of an integrated acousto-optic tunable filter (AOTF) as well as its responsivity to the rf driving signal and sensitivity to temperature changes are experimentally investigated and quantified using a diode-laser-based interrogation system. A spectroscopic technique, exploiting the rf frequency modulation of the laser beam and the phase-sensitive detection of the AOTF transmission, has been used for this purpose. That allows for the generation of a dispersivelike signal, which serves as a reference for tracking any wavelength change of the filter's peak with high resolution. The possibility of using the integrated AOTF as a spectrum analyzer with this interrogation scheme for fiber Bragg grating (FBG) strain sensing is also discussed.

  2. Cell-stimulation therapy of lateral epicondylitis with frequency-modulated low-intensity electric current.

    Science.gov (United States)

    Aliyev, R M; Geiger, G

    2012-03-01

    In addition to the routine therapy, the patients with lateral epicondylitis included into experimental group were subjected to a 12-week cell-stimulation therapy with low-intensity frequency-modulated electric current. The control group received the same routine therapy and sham stimulation (the therapeutic apparatus was not energized). The efficiency of this microcurrent therapy was estimated by comparing medical indices before therapy and at the end of a 12-week therapeutic course using a 10-point pain severity numeric rating scale (NRS) and Roles-Maudsley pain score. The study revealed high therapeutic efficiency of cell-stimulation with low-intensity electric current resulting probably from up-regulation of intracellular transmitters, interleukins, and prostaglandins playing the key role in the regulation of inflammation.

  3. The Use of Polysymptomatic Distress Categories in the Evaluation of Fibromyalgia (FM) and FM Severity

    Science.gov (United States)

    Wolfe, Frederick; Walitt, Brian T.; Rasker, Johannes J.; Katz, Robert S.; Hauser, Winfried

    2016-01-01

    Objective The polysymptomatic distress (PSD) scale is derived from variables used in the 2010 American College of Rheumatology (ACR) fibromyalgia (FM) criteria modified for survey and clinical research. The scale is useful in measuring the effect of PSD over the full range of pain-related clinical symptoms, not just in those who are FM criteria-positive. However, no PSD scale categories have been defined to distinguish severity of illness in FM or in those who do not satisfy the FM criteria. We analyzed the scale and multiple covariates to develop clinical categories and to further validate the scale. Methods FM was diagnosed according to the research criteria modification of the 2010 ACR FM criteria. We investigated categories in a large database of patients with pain (2732 with rheumatoid arthritis) and developed categories by using germane clinic variables that had been previously studied for severity groupings. By definition, FM cannot be diagnosed unless PSD is at least 12. Results Based on population categories, regression analysis, and inspections of curvilinear relationships, we established PSD severity categories of none (0–3), mild (4–7), moderate (8–11), severe (12–19), and very severe (20–31). Categories were statistically distinct, and a generally linear relationship between PSD categories and covariate severity was noted. Conclusion PSD categories are clinically relevant and demonstrate FM type symptoms over the full range of clinical illness. Although FM criteria can be clinically useful, there is no clear-cut symptom distinction between FM (+) and FM (−), and PSD categories can aid in more effectively classifying patients. PMID:26077414

  4. Neurosteroids modulate epileptiform activity and associated high-frequency oscillations in the piriform cortex.

    Science.gov (United States)

    Herrington, R; Lévesque, M; Avoli, M

    2014-01-03

    Allotetrahydrodeoxycorticosterone (THDOC) belongs to a class of pregnane neurosteroidal compounds that enhance brain inhibition by interacting directly with GABAA signaling, mainly through an increase in tonic inhibitory current. Here, we addressed the role of THDOC in the modulation of interictal- and ictal-like activity and associated high-frequency oscillations (HFOs, 80-500 Hz; ripples: 80-200 Hz, fast ripples: 250-500 Hz) recorded in vitro in the rat piriform cortex, a highly excitable brain structure that is implicated in seizure generation and maintenance. We found that THDOC: (i) increased the duration of interictal discharges in the anterior piriform cortex while decreasing ictal discharge duration in both anterior and posterior piriform cortices; (ii) reduced the occurrence of HFOs associated to both interictal and ictal discharges; and (iii) prolonged the duration of 4-aminopyridine-induced, glutamatergic independent synchronous field potentials that are known to mainly result from the activation of GABAA receptors. Our results indicate that THDOC can modulate epileptiform synchronization in the piriform cortex presumably by potentiating GABAA receptor-mediated signaling. This evidence supports the view that neurosteroids regulate neuronal excitability and thus control the occurrence of seizures.

  5. Affective and contextual values modulate spatial frequency use in object recognition

    Directory of Open Access Journals (Sweden)

    Laurent eCaplette

    2014-05-01

    Full Text Available Visual object recognition is of fundamental importance in our everyday interaction with the environment. Recent models of visual perception emphasize the role of top-down predictions facilitating object recognition via initial guesses that limit the number of object representations that need to be considered. Several results suggest that this rapid and efficient object processing relies on the early extraction and processing of low spatial frequencies (SF. The present study aimed to investigate the SF content of visual object representations and its modulation by contextual and affective values of the perceived object during a picture-name verification task. Stimuli consisted of pictures of objects equalized in SF content and categorised as having low or high affective and contextual values. To access the SF content of stored visual representations of objects, SFs of each image were then randomly sampled on a trial-by-trial basis. Results reveal that intermediate SFs between 14 and 24 cycles per object (2.3 to 4 cycles per degree are correlated with fast and accurate identification for all categories of objects. Moreover, there was a significant interaction between affective and contextual values over the SFs correlating with fast recognition. These results suggest that affective and contextual values of a visual object modulate the SF content of its internal representation, thus highlighting the flexibility of the visual recognition system.

  6. 47 CFR 73.297 - FM stereophonic sound broadcasting.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false FM stereophonic sound broadcasting. 73.297... RADIO BROADCAST SERVICES FM Broadcast Stations § 73.297 FM stereophonic sound broadcasting. (a) An FM... broadcasting, equipment performance measurements must be made to ensure that the transmitted signal...

  7. Continuous Transmission Frequency Modulation Detection under Variable Sonar-Target Speed Conditions

    Directory of Open Access Journals (Sweden)

    Jun Yang

    2013-03-01

    Full Text Available As a ranging sensor, a continuous transmission frequency modulation (CTFM sonar with its ability for range finding and range profile formation works effectively under stationary conditions. When a relative velocity exists between the target and the sonar, the echo signal is Doppler-shifted. This situation causes the output of the sensor to deviate from the actual target range, thus limiting its applications to stationary conditions only. This work presents an approach for correcting such a deviation. By analyzing the Doppler effect during the propagation process, the sensor output can be corrected by a Doppler factor. To obtain this factor, a conventional CTFM system is slightly modified by adding a single tone signal with a frequency that locates out-of-sweep range of the transmitted signal. The Doppler factor can be extracted from the echo. Both verification experiments and performance tests are carried out. Results indicate the validity of the proposed approach. Moreover, ranging precision under different processing setups is discussed. For adjacent multiple targets, the discrimination ability is influenced by displacement and velocity. A discrimination boundary is provided through an analysis.

  8. Continuous transmission frequency modulation detection under variable sonar-target speed conditions.

    Science.gov (United States)

    Wang, Yang; Yang, Jun

    2013-03-13

    As a ranging sensor, a continuous transmission frequency modulation (CTFM) sonar with its ability for range finding and range profile formation works effectively under stationary conditions. When a relative velocity exists between the target and the sonar, the echo signal is Doppler-shifted. This situation causes the output of the sensor to deviate from the actual target range, thus limiting its applications to stationary conditions only. This work presents an approach for correcting such a deviation. By analyzing the Doppler effect during the propagation process, the sensor output can be corrected by a Doppler factor. To obtain this factor, a conventional CTFM system is slightly modified by adding a single tone signal with a frequency that locates out-of-sweep range of the transmitted signal. The Doppler factor can be extracted from the echo. Both verification experiments and performance tests are carried out. Results indicate the validity of the proposed approach. Moreover, ranging precision under different processing setups is discussed. For adjacent multiple targets, the discrimination ability is influenced by displacement and velocity. A discrimination boundary is provided through an analysis.

  9. Frequency modulation of high-order harmonic generation in an orthogonally polarized two-color laser field.

    Science.gov (United States)

    Li, Guicun; Zheng, Yinghui; Ge, Xiaochun; Zeng, Zhinan; Li, Ruxin

    2016-08-08

    We have experimentally investigated the frequency modulation of high-order harmonics in an orthogonally polarized two-color laser field consisting of a mid-infrared 1800nm fundamental pulse and its second harmonic pulse. It is demonstrated that the high harmonic spectra can be fine-tuned as we slightly change the relative delay of the two-color laser pulses. By analyzing the relative frequency shift of each harmonic at different two-color delays, the nonadiabatic spectral shift induced by the rapid variation of the intensity-dependent intrinsic dipole phase can be distinguished from the blueshift induced by the change of the refractive index during self-phase modulation (SPM). Our comprehensive analysis shows that the frequency modulation pattern is a reflection of the average emission time of high-order harmonic generation (HHG), thus offering a simple method to fine-tune the spectra of the harmonics on a sub-cycle time scale.

  10. Manifestation of large-scale kink oscillations of coronal loops in the low frequency modulations of solar microwave emission

    Science.gov (United States)

    Khodachenko, Maxim; Kislyakova, Kristina; Zaqarashvili, Teimuraz; Kislyakov, Albert; Panchenko, Mykhaylo; Zaitsev, Valerii; Rucker, Helmut

    Very-low-frequency fluctuations (¡ 0.01 Hz) of solar microwave radiation were analysed by means of a "sliding window" Fourier transform combined with the Wigner-Ville technique. In view of the fact that slow variations of the magnetic field in the radiation source, as well as a large-scale motion of the source, can modulate the intensity of the received radio signal, we considered large-scale kink-type oscillatory motions of coronal loops which were accompanied also by periodic magnetic stress, created near the loops footpoints during each inclination of loop, i.e. two times per the oscillation cycle. In such cases a properly located observer, besides of the modulation caused by motion of the emission diagram pattern at the main oscillation frequency, may see also modulation at a double frequency of the loop oscillation as well as much weaker higher harmonics. Therefore, the presence in the very-low-frequency spectra of the lines at the main and double frequency of the loop oscillation ("modulation pairs") may indicate about a kink-type oscillatory dynamics of the loop. Special attention in the present study has been paid to the analysis of modulations of microwave emission recorded at the same time when TRACE EUV telescope observed large scale oscillations of coronal loops. The applied data analysis technique, besides of the modulations connected with loop kink oscillations seen by TRACE, enables to detect also the modulations associated with kink oscillations of smaller (invisible for TRACE) loops. Acknowledgements: MLK and TZ acknowledge Austrian Fond zur Fürderung der wissenschaftlichen Forschung (project P21197-N16); MP and HOR acknowledge Austrian Fond zur Fürderung der wissenschaftlichen Forschung (project P20680-N16).

  11. Design and modeling of an all-optical frequency modulated MEMS strain sensor using nanoscale Bragg gratings

    DEFF Research Database (Denmark)

    Reck, Kasper; Almind, Ninia Sejersen; Mar, Mikkel Dysseholm;

    2009-01-01

    We present modeling and design of an all-optical MEMS Bragg grating (half-pitch of 125 nm) strain sensor for single-fiber distributed sensing. Low optical loss and the use of frequency modulation rather than amplitude modulation, makes this sensor better suited for distributed systems than...... mechanical amplification can be obtained if using an angled double beam micrometer scale MEMS structure, compared to conventional fiber Bragg grating sensors. An optimized design and fabrication process is presented....

  12. Response of plasmonic terahertz detectors to amplitude modulated signals

    Science.gov (United States)

    Rupper, Greg; Rudin, Sergey; Shur, Michael

    2015-09-01

    We present theoretical study of the response of two-dimensional gated electron gas to an amplitude modulated signals with carrier frequency in the terahertz range. The model is based on complete hydrodynamic equations, and includes effects of viscosity, pressure gradients and thermal transport in the conduction channel of a high electron mobility semiconductor transistor (HEMT). The modulation response was evaluated as a function of modulation frequency fM for a wide range of mobility values. Maximum modulation frequency fMAX was evaluated as a function of channel mobility, with typical values of fMAX in the subterahertz range of frequencies. Our analysis shows that short channel field effect transistors operating in the plasmonic regime can meet all the requirements for applications as terahertz detectors and modulators in ultra high-speed wireless communication circuits.

  13. High-frequency combustion instability control through acoustic modulation at the inlet boundary for liquid rocket engine applications

    Science.gov (United States)

    Bennewitz, John William

    This research investigation encompasses experimental tests demonstrating the control of a high-frequency combustion instability by acoustically modulating the propellant flow. A model rocket combustor burned gaseous oxygen and methane using a single-element, pentad-style injector. Flow conditions were established that spontaneously excited a 2430 Hz first longitudinal combustion oscillation at an amplitude up to p'/pc ≈ 6%. An acoustic speaker was placed at the base of the oxidizer supply to modulate the flow and alter the oscillatory behavior of the combustor. Two speaker modulation approaches were investigated: (1) Bands of white noise and (2) Pure sinusoidal tones. The first approach adjusted 500 Hz bands of white noise ranging from 0-500 Hz to 2000-2500 Hz, while the second implemented single-frequency signals with arbitrary phase swept from 500-2500 Hz. The results showed that above a modulation signal amplitude threshold, both approaches suppressed 95+% of the spontaneous combustion oscillation. By increasing the applied signal amplitude, a wider frequency range of instability suppression became present for these two acoustic modulation approaches. Complimentary to these experiments, a linear modal analysis was undertaken to investigate the effects of acoustic modulation at the inlet boundary on the longitudinal instability modes of a dump combustor. The modal analysis employed acoustically consistent matching conditions with a specific impedance boundary condition at the inlet to represent the acoustic modulation. From the modal analysis, a naturally unstable first longitudinal mode was predicted in the absence of acoustic modulation, consistent with the spontaneously excited 2430 Hz instability observed experimentally. Subsequently, a detailed investigation involving variation of the modulation signal from 0-2500 Hz and mean combustor temperature from 1248-1685 K demonstrated the unstable to stable transition of a 2300-2500 Hz first longitudinal mode. The

  14. Baseband Transceiver Design of a High Definition Radio FM System Using Joint Theoretical Analysis and FPGA Implementation

    Directory of Open Access Journals (Sweden)

    Chien-Sheng Chen

    2014-01-01

    Full Text Available Advances in wireless communications have enabled various technologies for wireless digital communication. In the field of digital radio broadcasting, several specifications have been proposed, such as Eureka-147 and digital radio mondiale (DRM. These systems require a new spectrum assignment, which incurs heavy cost due to the depletion of the available spectrum. Therefore, the in-band on-channel (IBOC system has been developed to work in the same band with the conventional analog radio and to provide digital broadcasting services. This paper discusses the function and algorithm of the high definition (HD radio frequency modulation (FM digital radio broadcasting system. Content includes data format allocation, constellation mapping, orthogonal frequency division multiplexing (OFDM modulation of the transmitter, timing synchronization, OFDM demodulation, integer and fraction carrier frequency (integer carrier frequency offset (ICFO and fractional CFO (FCFO estimation, and channel estimation of the receiver. When we implement this system to the field programmable gate array (FPGA based on a hardware platform, both theoretical and practical aspects have been considered to accommodate the available hardware resources.

  15. The Time-Frequency Energy Attenuation Factor and Its Application on the Basis of Gauss Linear Frequency-Modulated Continuous Wavelet Transform

    Institute of Scientific and Technical Information of China (English)

    Liu Xiqiang; Shen Ping; Li Hong; Shan Changlun; Ji Aidong; Zhang Ping; Cai Mingjun

    2004-01-01

    Based on the Gauss linear frequency-modulated wavelet transform, a new characteristic index is presented, namely time-frequency energy attenuation factor which can reflect the difference features of waveform in earthquake focus mechanism, wave traveling path and its attenuation characteristics in focal area or near field. In order to test its validity, we select the natural earthquakes and explosion or collapse events whose focus mechanisms vary obviously, and some natural earthquakes located at the same site or in a very small area. The study indicates that the time-frequency energy attenuation factors of the natural earthquakes are obviously different with that of explosion or collapse events, and the change of the time-frequency energy attenuation factors is relatively stable for the earthquakes under the normal seismicity background. Using the above-mentioned method, it is expected to offer a useful criterion for strong earthquake prediction by continuous earthquake observation.

  16. Effects of electronic state modulation on the high-frequency response characteristics of GaAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Basanta Singh, N., E-mail: basanta_n@rediffmail.co [Department of Electronics and Communication Engineering, Manipur Institute of Technology, Imphal 795 004 (India); Deb, Sanjoy, E-mail: deb_sanjoy@yahoo.co [Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata 700 032 (India); Sarkar, Subir Kumar, E-mail: su_sircir@yahoo.co.i [Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata 700 032 (India)

    2009-11-01

    The effect of electronic-state modulation on the high frequency response of GaAs quantum well with thin inserted barrier layer is studied. The carrier scattering by polar optic phonons, acoustic deformation potential and background ionized impurities are incorporated in the present calculations considering the carrier distribution to be heated drifted Fermi-Dirac distribution. Modified phonon spectra and modulated electron wave function give different values of form factor compared to bulk mode phonon. Mobility is found to be enhanced on insertion of thin layer inside the quantum well. The ac mobility and the phase lag increases with the increase in both the channel width and the 2D carrier concentration. Cutoff frequency, where ac mobility drops down to 0.707 of its low frequency value, is observed to be enhanced reflecting better high frequency response.

  17. Receptores de radio monochip para FM

    OpenAIRE

    Miguel López, José María

    2005-01-01

    Este libro aborda de forma estructurada tanto los aspectos de diseño como los de realización de receptores de radio para la banda de FM. Tras unos primeros capítulos dedicados al estudio de las propiedades de la modulación de frecuencia y de los circuitos básicos que configuran un receptor de radio, se desarrolla un minucioso análisis de los circuitos integrados TDA7000/10/21. Paso a paso se muestra cómo diseñar con estos circuitos receptores de FM que, al requerir muy pocos ajustes, puede...

  18. FM Interference Suppression for PRC-CW Radar Based on ASTFT and Median Filtering%基于ASTFT和中值滤波的PRC-CW雷达FM干扰抑制方法

    Institute of Scientific and Technical Information of China (English)

    陈文武; 蔡征宇; 陈如山

    2011-01-01

    The influence of frequency modulation (FM) interference on correlation detection performance of the pseudo random code continuous wave( PRC-CW )radar is analyzed. It is found that the correlation output deteriorates greatly when the FM interference power exceeds the antijamming limitation of the radar. According to the fact that the PRC-CW radar return signal is a wideband pseudo random signal occupying the whole time-frequency(TF) plane,whereas the FM interference signal is well concentrated in the TF plane, a new method is proposed based on adaptive short-time Fourier transform (ASTIr) and median filtering for FM interference suppression. This method implements the filtering of the received signal by substituting the median filter output for only a portion of the IF plane corrupted by the interference. The echo signals corrupted by two types of interferences including linear FM ( LFM ) and sinusoidal FM ( SFM ) forms under different signal-tojamming ratio(SJR) situations are simulated. It is shown that the method can effectively suppress the FM interference and improve the performance of target detection significantly.%通过分析调频(FM)干扰对伪码调相连续波雷达相关检测性能的影响,发现当FM干扰超出伪码调相雷达自身抗干扰容限时,相关输出严重恶化.针对该问题,考虑到伪码在时频平面上是近似均匀和平坦的,而FM干扰则具有较好的时频聚集性,该文提出了基于自适应短时傅里叶变换(ASTFT)和中值滤波的FM干扰抑制方法.该方法通过对时频平面上被干扰污染的部分进行中值滤波,实现了对FM干扰的抑制.对不同信干比情况下线性调频和正弦调频干扰抑制前后的相关输出进行了仿真分析.结果表明,该方法能够有效抑制干扰,使相关输出得到显著改善.

  19. Time-frequency analysis for microwave reflectometry data processing in the HL-2A tokamak

    Science.gov (United States)

    Zhong, W. L.; Shi, Z. B.; Zou, X. L.; Ding, X. T.; Huang, X. L.; Dong, Y. B.; Liu, Z. T.; Xiao, W. W.; Ji, X. Q.; Cui, Z. Y.; Liu, Yi; Yan, L. W.; Yang, Q. W.; Duan, X. R.

    2011-10-01

    The Choi-Williams distribution (CWD) technique is introduced as a time-frequency tool for processing data measured from the new developed homodyne and the fixed frequency reflectometry in the HL-2A tokamak. The comparison between spectrogram and CWD for the simulated signal is presented. It indicates that the CWD can greatly improve the representation of the time-frequency content of the multi-components signal. Its effectiveness is demonstrated through two applications in HL-2A, which are the extraction of beat frequencies from the frequency modulated-continuous wave reflectometry (FM-CW) and the characterizing of the fluctuations. The density profile inversed from the group delay of the FM-CW and the density fluctuations deduced from the fixed-frequency reflectometry would be more reliable and accurate by using the CWD technique.

  20. Laser Frequency-Modulated Spectroscopy of a Laser-Guided Plasma in Sodium Vapor: Line Positions for NaH (A1Σ+-X1Σ+), Na (9-13dand 11-14s), and Ar (5p-4s)

    Science.gov (United States)

    Bahns, J. T.; Tsai, C. C.; Ji, B.; Kim, J. T.; Zhao, G.; Stwalley, W. C.; Bloch, J. C.; Field, R. W.

    1997-12-01

    Laser frequency-modulated (FM) spectroscopy has been used as an axial probe of a laser-guided electric discharge in sodium-argon vapor contained in an optically accessible metal heat pipe oven. Absorption measurements in the region 23 106-23 881 cm-1provided accurate line positions (±<0.006 cm-1) for 141 transitions in thev‧ = 3-8 ←v″ = 0 andv‧ = 5-9 ←v″ = 1 bands of NaH (A1Σ+-X1Σ+). In addition, 18 transitions of Na (3pto 9-13dand 11-14s) and 10 of argon (5p-4s) were measured. Analysis of the spectrum indicates that perhaps all absorption signals are due to neutrals NaH, Na, and Ar and are observed via "population" modulation.

  1. Polarization control efficiency manipulation in resonance-mediated two-photon absorption by femtosecond spectral frequency modulation

    Science.gov (United States)

    Yao, Yunhua; Cheng, Wenjing; Zheng, Ye; Xu, Cheng; Liu, Pei; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong; Zhang, Shian

    2017-04-01

    The femtosecond laser polarization modulation is considered as a very simple and efficient method to control the multi-photon absorption process. In this work, we theoretically and experimentally show that the polarization control efficiency in the resonance-mediated two-photon absorption can be artificially manipulated by modulating the femtosecond spectral frequency components. We theoretically demonstrate that the on- and near-resonant parts in the resonance-mediated two-photon absorption process depend on the different femtosecond spectral frequency components, and therefore their contributions in the whole excitation process can be controlled by properly designing the femtosecond spectral frequency components. The near-resonant two-photon absorption is correlated with the femtosecond laser polarization while the on-resonant two-photon absorption is independent of it, and thus the polarization control efficiency in the resonance-mediated two-photon absorption can be manipulated by the femtosecond spectral frequency modulation. We experimentally verify these theoretical results by performing the laser polarization control experiment in the Dy3+-doped glass sample under the modulated femtosecond spectral frequency components, and the experimental results show that the polarization control efficiency can be increased when the central spectral frequency components are cut off, while it is decreased when both the low and high spectral frequency components are cut off, which is in good agreement with the theoretical predictions. Our works can provide a feasible pathway to understand and control the resonance-mediated multi-photon absorption process under the femtosecond laser field excitation, and also may open a new opportunity to the related application areas.

  2. Low-Voltage, Low-Power, and Wide-Tuning-Range Ring-VCO for Frequency ΔΣ Modulator

    DEFF Research Database (Denmark)

    Tuan Vu, Cao; Wisland, Dag T.; Lande, Tor Sverre

    A low-voltage, low-power, and wide-tuning-range VCO which converts an analog input voltage to phase information for a frequency ΔΣ modulator is proposed in this paper. The VCO is based on a differential ring oscillator, which is improved with modified symmetric load and a positive feedback in the...

  3. Resting and Task-Modulated High-Frequency Brain Rhythms Measured by Scalp Encephalography in Infants with Tuberous Sclerosis Complex

    Science.gov (United States)

    Stamoulis, Catherine; Vogel-Farley, Vanessa; Degregorio, Geneva; Jeste, Shafali S.; Nelson, Charles A.

    2015-01-01

    The electrophysiological correlates of cognitive deficits in tuberous sclerosis complex (TSC) are not well understood, and modulations of neural dynamics by neuroanatomical abnormalities that characterize the disorder remain elusive. Neural oscillations (rhythms) are a fundamental aspect of brain function, and have dominant frequencies in a wide…

  4. A bulk-controlled ring-VCO with 1/f-noise reduction for frequency ΔΣ modulator

    DEFF Research Database (Denmark)

    Tuan Vu, CAO; Wisland, Dag T.; Lande, Tor Sverre

    The paper introduces a bulk-controlled ring-VCO with a tail transistor utilizing flicker-noise (1/f-noise) reduction techniques for a frequency-based DeltaSigma modulator (FDSM). This VCO converts an analog input voltage to phase information under various bias conditions ranging from sub...

  5. Coherent lidar modulated with frequency stepped pulse trains for unambiguous high duty cycle range and velocity sensing in the atmosphere

    DEFF Research Database (Denmark)

    Lindelöw, Per Jonas Petter; Mohr, Johan Jacob

    2007-01-01

    Range unambiguous high duty cycle coherent lidars can be constructed based on frequency stepped pulse train modulation, even continuously emitting systems could be envisioned. Such systems are suitable for velocity sensing of dispersed targets, like the atmosphere, at fast acquisition rates...

  6. Effect of higher order non-linearity in frequency variation of self-phase modulation in optical fiber communication

    Institute of Scientific and Technical Information of China (English)

    Abhijit Sinha; Sourangshu Mukhopadhyay

    2004-01-01

    In optical soliton propagation through a single mode optical fiber,it is established that self-phase mod ulation is maintained by the third order non-linearity of the silica-based glass material of the fiber.In this paper we show that the fifth order non-linearity has also some contribution in frequency variation of self-phase modulation.

  7. Resting and Task-Modulated High-Frequency Brain Rhythms Measured by Scalp Encephalography in Infants with Tuberous Sclerosis Complex

    Science.gov (United States)

    Stamoulis, Catherine; Vogel-Farley, Vanessa; Degregorio, Geneva; Jeste, Shafali S.; Nelson, Charles A.

    2015-01-01

    The electrophysiological correlates of cognitive deficits in tuberous sclerosis complex (TSC) are not well understood, and modulations of neural dynamics by neuroanatomical abnormalities that characterize the disorder remain elusive. Neural oscillations (rhythms) are a fundamental aspect of brain function, and have dominant frequencies in a wide…

  8. A micropower supervisor for wireless nodes with a digital pulse frequency modulator battery monitor

    Science.gov (United States)

    Carloni, Mirko; d'Aparo, Rocco; Scorrano, Pierpaolo; Naticchia, Berardo; Conti, Massimo

    2013-05-01

    In the last few years the increased development of wireless technologies led to the development of micropower devices with power management and real time power control, aimed to maximize the battery life time.1 The main and simplest method to estimate residual battery life time is by voltage measurement. This kind of measurement is simple but is useless in many cases, especially when long term Lithium-Thionyl chloride batteries are used, since its voltage is flat for more than 90% of the battery discharge. In this case, a current control should be used. However, these kinds of devices have various problems as a limited range of measurement and not negligible quiescent current that may distort the measurements. In this work we developed a micropower supervisor for wireless sensor nodes with a charge battery monitor, whose features are aimed at solving the problems just described. The current measured by a sense resistor, is filtered by a super-capacitor, amplified by a current sense amplifier and then fed to a voltage to pulse frequency modulator. In this way, the charge consumption can be estimated without the saturation of the current sense amplifier, even if the wireless node consumes time limited high current spikes, for example during transmission.

  9. Spatio-temporal analysis of stimuli-modulated spontaneous low frequency oscillations

    Institute of Scientific and Technical Information of China (English)

    LI Ming; LIU YaDong; HU DeWen; WANG YuCheng; LIU FaYi; FENG GuiYu

    2007-01-01

    In this paper, the spatio-temporal architecture of the stimulation-modulated spontaneous low frequency oscillation (LFO) in the SD rat's somatosensory cortex is studied by optical imaging (OI) technology.After the electrical stimulation, it is observed that the phases of the LFO signals are changed, the amplitudes are increased, and most importantly, the signals in the bilateral somatosensory cortex tend to be synchronized. Based on these phenomena, the origin of the LFO signals is discussed. It is argued that the arteriole vasomotion may be the major contribution to the LFO signals under green illumination (546±10 nm). The phase relationship among the LFO signals of arteries, veins and cortex has also been studied. It is found that there are phase differences between the LFO signal of veins and that of cortex under red illumination (605±10 nm), the signal of cortex leads that of veins by 0.6-1.0 s, while under green illumination, no obvious differences are observed and the reason may be that the mechanism of the LFO signals of cortexes and vessels are different.

  10. Super-resolved multimodal multiphoton microscopy with spatial frequency-modulated imaging

    CERN Document Server

    Field, Jeffrey J; Domingue, Scott R; Motz, Alyssa M Allende; DeLuca, Keith F; DeLuca, Jennifer G; Kuciauskas, Darius; Levi, Dean H; Squier, Jeff A; Bartels, Randy A

    2015-01-01

    Super-resolved far-field microscopy has emerged as a powerful tool for investigating the structure of objects with resolution well below the diffraction limit of light. Nearly all super-resolution imaging techniques reported to date rely on real energy states of probe molecules to circumvent the diffraction limit, preventing super-resolved imaging of contrast mechanisms that occur via virtual energy states such as harmonic generation (HG). Here we report a super-resolution technique based on SPatIal Frequency modulated Imaging (SPIFI) that permits super-resolved nonlinear microscopy with any contrast mechanism, and with single-pixel detection. We show multimodal super-resolved images with two-photon excited fluorescence (TPEF) and second-harmonic generation (SHG) from biological and inorganic media. Multiphoton SPIFI (MP-SPIFI) provides spatial resolution up to 2$\\eta$ below the diffraction limit, where $\\eta$ is the highest power of the nonlinear intensity response. MP-SPIFI has the potential to not only pro...

  11. Evaluation of correlation property of linear-frequency-modulated signals coded by maximum-length sequences

    Science.gov (United States)

    Yamanaka, Kota; Hirata, Shinnosuke; Hachiya, Hiroyuki

    2016-07-01

    Ultrasonic distance measurement for obstacles has been recently applied in automobiles. The pulse-echo method based on the transmission of an ultrasonic pulse and time-of-flight (TOF) determination of the reflected echo is one of the typical methods of ultrasonic distance measurement. Improvement of the signal-to-noise ratio (SNR) of the echo and the avoidance of crosstalk between ultrasonic sensors in the pulse-echo method are required in automotive measurement. The SNR of the reflected echo and the resolution of the TOF are improved by the employment of pulse compression using a maximum-length sequence (M-sequence), which is one of the binary pseudorandom sequences generated from a linear feedback shift register (LFSR). Crosstalk is avoided by using transmitted signals coded by different M-sequences generated from different LFSRs. In the case of lower-order M-sequences, however, the number of measurement channels corresponding to the pattern of the LFSR is not enough. In this paper, pulse compression using linear-frequency-modulated (LFM) signals coded by M-sequences has been proposed. The coding of LFM signals by the same M-sequence can produce different transmitted signals and increase the number of measurement channels. In the proposed method, however, the truncation noise in autocorrelation functions and the interference noise in cross-correlation functions degrade the SNRs of received echoes. Therefore, autocorrelation properties and cross-correlation properties in all patterns of combinations of coded LFM signals are evaluated.

  12. Property modulation of NiO films grown by radio frequency magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Chen, T.F.; Wang, A.J.; Shang, B.Y. [Department of Physics, Beijing Normal University, Beijing 100875 (China); Wu, Z.L.; Li, Y.L. [Analytical and Testing Center, Beijing Normal University, Beijing 100875 (China); Wang, Y.S., E-mail: yswang@bnu.edu.cn [Department of Physics, Beijing Normal University, Beijing 100875 (China)

    2015-09-15

    Highlights: • Controllable and preferential growth of NiO films were performed successfully on Si substrates. • Oxygen partial pressure lower than 6% is crucial for transformation of the preferential growth. • The film deposition rate is very sensitive to the low oxygen partial pressure. • NiO lattice expands quadratically with the increasing of oxygen partial pressures. • The films contain high concentration of Ni vacancies and show a good rectifying behavior with p-Si. - Abstract: NiO films were grown on Si substrates by radio frequency magnetron sputtering. The films were analyzed by an X-ray diffractometer, scanning electron microscope, X-ray photoelectron spectroscopy and SCS-4200 semiconductor characterization system. Evolution of the growth mode, lattice strain, morphology, chemistry states and electrical properties were investigated systematically. The film deposition rates and properties are very sensitive to the oxygen partial pressure lower than 10%. It is crucial to decrease the oxygen partial pressure to 2% for (1 1 1) film growth and the films would transform from (1 1 1) to (1 0 0) as the oxygen partial pressure increases from 2% to 6%. The film lattice expands quadratically with the increase of oxygen partial pressure. Nickel vacancy concentration in (1 1 1) films is much higher than that in (1 0 0) films. All (1 0 0) films show good rectifying behavior with p-Si. The film growth modes and properties could be modulated flexibly by controlling the oxygen partial pressures.

  13. Frequency modulation of stochastic gene expression bursts by strongly interacting small RNAs

    Science.gov (United States)

    Kumar, Niraj; Jia, Tao; Zarringhalam, Kourosh; Kulkarni, Rahul V.

    2016-10-01

    The sporadic nature of gene expression at the single-cell level—long periods of inactivity punctuated by bursts of mRNA or protein production—plays a critical role in diverse cellular processes. To elucidate the cellular role of bursting in gene expression, synthetic biology approaches have been used to design simple genetic circuits with bursty mRNA or protein production. Understanding how such genetic circuits can be designed with the ability to control burst-related parameters requires the development of quantitative stochastic models of gene expression. In this work, we analyze stochastic models for the regulation of gene expression bursts by strongly interacting small RNAs. For the parameter range considered, results based on mean-field approaches are significantly inaccurate and alternative analytical approaches are needed. Using simplifying approximations, we obtain analytical results for the corresponding steady-state distributions that are in agreement with results from stochastic simulations. These results indicate that regulation by small RNAs, in the strong interaction limit, can be used to effectively modulate the frequency of bursting. We explore the consequences of such regulation for simple genetic circuits involving feedback effects and switching between promoter states.

  14. In vivo BDNF modulation of hippocampal mossy fiber plasticity induced by high frequency stimulation.

    Science.gov (United States)

    Schjetnan, Andrea Gómez-Palacio; Escobar, Martha L

    2012-01-01

    Changes in synaptic efficacy and morphology have been proposed as mechanisms underlying learning and memory processes. In our previous studies, high frequency stimulation (HFS) sufficient to induce LTP at the hippocampal mossy fiber (MF) pathway, leads to MF synaptogenesis, in a prominent contralateral form, at the stratum oriens of hippocampal CA3 area. Recently we reported that acute intrahippocampal microinfusion of BDNF induces a lasting potentiation of synaptic efficacy at the MF projection accompanied by a structural reorganization at the CA3 area within the stratum oriens region in a prominent ipsilateral form. It is considered that the capacity of synapses to express plastic changes is itself subject to variation dependent on previous experience. Here we used intrahippocampal microinfusion of BDNF to analyze its effects on functional and structural synaptic plasticity induced by subsequent mossy fiber HFS sufficient to induce LTP in adult rats, in vivo. Our results show that BDNF modifies the ability of the MF pathway to present LTP by HFS. Moreover BDNF modified the structural reorganization pattern produced by HFS, presenting a balanced bilateral appearance. Microinfusion of K252a blocks the functional and morphological effects produced by BDNF, revealing that the BDNF modulation is dependent on its TrkB receptor activation. These findings support the idea that BDNF actions modify subsequent synaptic plasticity; a homeostatic mechanism thought to be essential for synaptic integration among prolonged temporal domains in the adult mammalian brain.

  15. Frequency modulation of stochastic gene expression bursts by strongly interacting small RNAs.

    Science.gov (United States)

    Kumar, Niraj; Jia, Tao; Zarringhalam, Kourosh; Kulkarni, Rahul V

    2016-10-01

    The sporadic nature of gene expression at the single-cell level-long periods of inactivity punctuated by bursts of mRNA or protein production-plays a critical role in diverse cellular processes. To elucidate the cellular role of bursting in gene expression, synthetic biology approaches have been used to design simple genetic circuits with bursty mRNA or protein production. Understanding how such genetic circuits can be designed with the ability to control burst-related parameters requires the development of quantitative stochastic models of gene expression. In this work, we analyze stochastic models for the regulation of gene expression bursts by strongly interacting small RNAs. For the parameter range considered, results based on mean-field approaches are significantly inaccurate and alternative analytical approaches are needed. Using simplifying approximations, we obtain analytical results for the corresponding steady-state distributions that are in agreement with results from stochastic simulations. These results indicate that regulation by small RNAs, in the strong interaction limit, can be used to effectively modulate the frequency of bursting. We explore the consequences of such regulation for simple genetic circuits involving feedback effects and switching between promoter states.

  16. Stable Isotope Measurements of Carbon Dioxide, Methane, and Hydrogen Sulfide Gas Using Frequency Modulation Spectroscopy

    Science.gov (United States)

    Nowak-Lovato, K.

    2014-12-01

    Seepage from enhanced oil recovery, carbon storage, and natural gas sites can emit trace gases such as carbon dioxide, methane, and hydrogen sulfide. Trace gas emission at these locations demonstrate unique light stable isotope signatures that provide information to enable source identification of the material. Light stable isotope detection through surface monitoring, offers the ability to distinguish between trace gases emitted from sources such as, biological (fertilizers and wastes), mineral (coal or seams), or liquid organic systems (oil and gas reservoirs). To make light stable isotope measurements, we employ the ultra-sensitive technique, frequency modulation spectroscopy (FMS). FMS is an absorption technique with sensitivity enhancements approximately 100-1000x more than standard absorption spectroscopy with the advantage of providing stable isotope signature information. We have developed an integrated in situ (point source) system that measures carbon dioxide, methane and hydrogen sulfide with isotopic resolution and enhanced sensitivity. The in situ instrument involves the continuous collection of air and records the stable isotope ratio for the gas being detected. We have included in-line flask collection points to obtain gas samples for validation of isotopic concentrations using our in-house isotope ratio mass spectroscopy (IRMS). We present calibration curves for each species addressed above to demonstrate the sensitivity and accuracy of the system. We also show field deployment data demonstrating the capabilities of the system in making live dynamic measurements from an active source.

  17. Neutron intensity modulation and time-focusing with integrated Larmor and resonant frequency techniques

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Jinkui, E-mail: zhaoj@ornl.gov; Hamilton, William A.; Robertson, J. L.; Crow, Lowell [Instrument and Source Division, Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Lee, Sung-Woo; Kang, Yoon W. [Research Accelerator Division, Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2015-09-14

    The analysis of neutron diffraction experiments often assumes that neutrons are elastically scattered from the sample. However, there is growing evidence that a significant fraction of the detected neutrons is in fact inelastically scattered, especially from soft materials and aqueous samples. Ignoring these inelastic contributions gives rise to inaccurate experimental results. To date, there has been no simple method with broad applicability for inelastic signal separation in neutron diffraction experiments. Here, we present a simple and robust method that we believe could be suited for this purpose. We use two radio frequency resonant spin flippers integrated with a Larmor precession field to modulate the neutron intensity and to encode the inelastic scattering information into the neutron data. All three components contribute to the spin encoding. The Larmor field serves several additional purposes. Its usage facilitates neutron time-focusing, eliminates the need for stringent magnetic shielding, and allows for compact setups. The scheme is robust, simple, and flexible. We believe that, with further improvements, it has the potential of adding inelastic signal discrimination capabilities to many existing diffraction instruments in the future.

  18. Frequency measurement of THz waves by electro-optic sampling using Mach-Zehnder-modulator-based flat comb generator

    Science.gov (United States)

    Morohashi, Isao; Kirigaya, Mayu; Kaneko, Yuta; Katayama, Ikufumi; Sakamoto, Takahide; Sekine, Norihiko; Kasamatsu, Akifumi; Hosako, Iwao

    2016-02-01

    In the recent progress in terahertz (THz) devices, various kinds of source devices, such as resonant tunneling diodes, quantum cascade lasers and so forth, have been developed. Frequency measurement of THz radiations, which can operate in high speed and at room-temperature, is important for development of high-performance THz source devices. Recently, frequency measurement using optical combs are demonstrated by several groups. In these techniques, modelocked lasers (MLLs) are used for optical comb source, so that phase-locking techniques are required in order to stabilize the repetition frequency of the MLLs. On the other hand, a modulator-based optical comb generator has high accuracy and stability in the comb spacing, which is comparable to that of microwave signal driving the modulator. Thus it is suitable for frequency measurement of THz waves. In this paper, we demonstrated frequency measurement of THz waves using a Mach-Zehnder-modulator-based flat comb generator (MZ-FCG). The frequency measurement was carried out by an electro-optic (EO) sampling method, where an optical two-tone signal extracted from the optical comb generated by the MZ-FCG was used for the probe light. A 100 GHz signal generated by a W-band frequency multiplier and the probe beam collinearly traveled through an EO crystal, and beat signals between them were measured by a combination of a balanced photodetector and a spectrum analyzer. As a result, frequency measurement of the 100 GHz wave was successfully demonstrated, in which the linewidth of the beat signal was less than 1 Hz.

  19. Q-switched mode-locking of an erbium-doped fiber laser using cavity modulation frequency detuning.

    Science.gov (United States)

    Chang, You Min; Lee, Junsu; Jhon, Young Min; Lee, Ju Han

    2012-07-20

    We present the results of an investigation regarding a Q-switched mode-locked fiber laser scheme based on a cavity modulation frequency detuning technique. The approach is based on undamped laser relaxation oscillations occurring due to frequency detuning in the fundamental cavity resonance frequency. Through a range of experiments with an erbium-doped, fiber-based, ring-cavity laser, this approach has been shown to be capable of generating high-quality Q-switched mode-locked pulses from an optical fiber-based laser. The maximum frequency detuning range for a stable Q-switched mode-locking operation has been observed to vary depending on the pump power used. We found that the highest pulse peak power was obtained at the frequency detuning threshold at which the operation changed from the mode-locking to the Q-switched mode-locking regime.

  20. Simultaneous optical carrier and radio frequency re-modulation in radio-over-fiber systems employing reflective SOA modulators

    DEFF Research Database (Denmark)

    Kassar, Carvalho; Calabretta, Nicola; Tafur Monroy, Idelfonso

    2007-01-01

    We demonstrate an innovative full-duplex radio-over-fibre transmission system employing a reflective SOA to perform simultaneous reusing of the optical carrier and data re-modulation, thus avoiding the use of local radiofrequency oscillator at the station sites.......We demonstrate an innovative full-duplex radio-over-fibre transmission system employing a reflective SOA to perform simultaneous reusing of the optical carrier and data re-modulation, thus avoiding the use of local radiofrequency oscillator at the station sites....

  1. TDLAS中激光器IM/FM相位延迟实时测量方法研究%IM/FM Phase Delay Time Measurement Method of Laser for TDLAS

    Institute of Scientific and Technical Information of China (English)

    张超; 马维光

    2014-01-01

    The present paper presents an method of using fiber Michelson interferometer to measure the Intensity-frequency (IM/FM ) phase delay change of the laser ,it could realize the phase delay time measurement ,while modulating the laser .Experimen-tal results show that the laser output signal intensity-frequency (IM/FM ) phase delay of the laser has some differences from the theoretical value .The proposed method can be used to compensate for real-time signal strength-frequency (IM/FM ) phase delay effect on the gas concentration measurement results .%在基于谐波检测法的TDLAS(可调谐二极管激光吸收光谱)系统中,在通过改变激光器注入电流实现激光频率扫描和调制的同时引起激光强度的变化,激光器输出信号的强度-频率(IM/FM )相位延迟φm 的变化将直接导致谐波系数波动,带来系统误差。提出一种利用光纤迈克尔逊干涉仪实现激光器输出信号强度-频率(IM/FM )相位延迟φm 的测量方法,能在激光器调制测量的同时实时测量相位延迟φm 。实验结果表明,激光器输出信号强度-频率(IM/FM )相位延迟φm 与理论值π有一定差异。研究提出的方法可以用来实时补偿信号强度-频率(IM/FM )相位延迟φm 对气体浓度测量结果的影响。

  2. Discrimination and Identification of Modulation-Frequency Using Noise, Tone, and Tonal-Complex Carriers

    Science.gov (United States)

    1988-05-23

    frequency. For these frequencies, identification performance was almost as good as discrimination performance. This " edge effect " is commonly...if the edge effect acts over a fixed frequency range, then the better relative performance at the lower frequencies may be due to the edge effect rather

  3. Effect of modulation frequency bandwidth on measurement accuracy and precision for digital diffuse optical spectroscopy (dDOS)

    Science.gov (United States)

    Jung, Justin; Istfan, Raeef; Roblyer, Darren

    2014-03-01

    Near-infrared (NIR) frequency-domain Diffuse Optical Spectroscopy (DOS) is an emerging technology with a growing number of potential clinical applications. In an effort to reduce DOS system complexity and improve portability, we recently demonstrated a direct digital sampling method that utilizes digital signal generation and detection as a replacement for more traditional analog methods. In our technique, a fast analog-to-digital converter (ADC) samples the detected time-domain radio frequency (RF) waveforms at each modulation frequency in a broad-bandwidth sweep (50- 300MHz). While we have shown this method provides comparable results to other DOS technologies, the process is data intensive as digital samples must be stored and processed for each modulation frequency and wavelength. We explore here the effect of reducing the modulation frequency bandwidth on the accuracy and precision of extracted optical properties. To accomplish this, the performance of the digital DOS (dDOS) system was compared to a gold standard network analyzer based DOS system. With a starting frequency of 50MHz, the input signal of the dDOS system was swept to 100, 150, 250, or 300MHz in 4MHz increments and results were compared to full 50-300MHz networkanalyzer DOS measurements. The average errors in extracted μa and μs' with dDOS were lowest for the full 50-300MHz sweep (less than 3%) and were within 3.8% for frequency bandwidths as narrow as 50-150MHz. The errors increased to as much as 9.0% when a bandwidth of 50-100MHz was tested. These results demonstrate the possibility for reduced data collection with dDOS without critical compensation of optical property extraction.

  4. Spectrotemporal modulation sensitivity for hearing-impaired listeners: dependence on carrier center frequency and the relationship to speech intelligibility.

    Science.gov (United States)

    Mehraei, Golbarg; Gallun, Frederick J; Leek, Marjorie R; Bernstein, Joshua G W

    2014-07-01

    Poor speech understanding in noise by hearing-impaired (HI) listeners is only partly explained by elevated audiometric thresholds. Suprathreshold-processing impairments such as reduced temporal or spectral resolution or temporal fine-structure (TFS) processing ability might also contribute. Although speech contains dynamic combinations of temporal and spectral modulation and TFS content, these capabilities are often treated separately. Modulation-depth detection thresholds for spectrotemporal modulation (STM) applied to octave-band noise were measured for normal-hearing and HI listeners as a function of temporal modulation rate (4-32 Hz), spectral ripple density [0.5-4 cycles/octave (c/o)] and carrier center frequency (500-4000 Hz). STM sensitivity was worse than normal for HI listeners only for a low-frequency carrier (1000 Hz) at low temporal modulation rates (4-12 Hz) and a spectral ripple density of 2 c/o, and for a high-frequency carrier (4000 Hz) at a high spectral ripple density (4 c/o). STM sensitivity for the 4-Hz, 4-c/o condition for a 4000-Hz carrier and for the 4-Hz, 2-c/o condition for a 1000-Hz carrier were correlated with speech-recognition performance in noise after partialling out the audiogram-based speech-intelligibility index. Poor speech-reception and STM-detection performance for HI listeners may be related to a combination of reduced frequency selectivity and a TFS-processing deficit limiting the ability to track spectral-peak movements.

  5. 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.

  6. A long-term frequency-stabilized erbium-fiber-laser-based optical frequency comb with an intra-cavity electro-optic modulator

    CERN Document Server

    Zhang, Y; Zhao, W; Meng, S; Fan, S; Zhang, L; Guo, G; Zhang, S; Jiang, H

    2014-01-01

    We demonstrate a home-made optical frequency comb based on an erbium-doped-fiber femtosecond laser with a ring cavity. The repetition rate of the laser is about 209 MHz determined by optical length of the laser cavity. By controlling an intra-cavity electro-optic modulator and a Piezo-transducer, the repetition rate can be stabilized with megahertz bandwidth in a range of 3 kilohertz, enabling long-term repetition rate phase-locking. The in-loop frequency instability of the repetition rate, limited by measurement system, is 1.3E-13 at 1 second integration time and inversely proportional to integration time for short terms. Using a common path f-2f interferometer, the carrier envelope offset (CEO) frequency of the frequency comb is obtained with a signal-to-noise ratio of 40 dB for 3 megahertz resolution spectrum. Stabilized CEO frequency exhibits a deviation of 0.6 milihertz at 1 second integration time.

  7. An Ultrahigh Frequency Partial Discharge Signal De-Noising Method Based on a Generalized S-Transform and Module Time-Frequency Matrix

    Directory of Open Access Journals (Sweden)

    Yushun Liu

    2016-06-01

    Full Text Available Due to electromagnetic interference in power substations, the partial discharge (PD signals detected by ultrahigh frequency (UHF antenna sensors often contain various background noises, which may hamper high voltage apparatus fault diagnosis and localization. This paper proposes a novel de-noising method based on the generalized S-transform and module time-frequency matrix to suppress noise in UHF PD signals. The sub-matrix maximum module value method is employed to calculate the frequencies and amplitudes of periodic narrowband noise, and suppress noise through the reverse phase cancellation technique. In addition, a singular value decomposition de-noising method is employed to suppress Gaussian white noise in UHF PD signals. Effective singular values are selected by employing the fuzzy c-means clustering method to recover the PD signals. De-noising results of simulated and field detected UHF PD signals prove the feasibility of the proposed method. Compared with four conventional de-noising methods, the results show that the proposed method can suppress background noise in the UHF PD signal effectively, with higher signal-to-noise ratio and less waveform distortion.

  8. Relations between frequency selectivity, temporal fine-structure processing, and speech reception in impaired hearing

    DEFF Research Database (Denmark)

    Strelcyk, Olaf; Dau, Torsten

    2009-01-01

    and binaural TFS-processing deficits in the HI listeners, no relation was found between TFS processing and frequency selectivity. The effect of noise on TFS processing was not larger for the HI listeners than for the NH listeners. Finally, TFS-processing performance was correlated with speech reception......Frequency selectivity, temporal fine-structure (TFS) processing, and speech reception were assessed for six normal-hearing (NH) listeners, ten sensorineurally hearing-impaired (HI) listeners with similar high-frequency losses, and two listeners with an obscure dysfunction (OD). TFS processing...... was investigated at low frequencies in regions of normal hearing, through measurements of binaural masked detection, tone lateralization, and monaural frequency modulation (FM) detection. Lateralization and FM detection thresholds were measured in quiet and in background noise. Speech reception thresholds were...

  9. Investigation of potential driver modules and transmission lines for a high frequency power system on the space station

    Science.gov (United States)

    Brush, Harold T.

    1986-01-01

    The feasibility of using Series Resonant Inverter as the driver module for high frequency power system on the Space Station was assessed. The performance of the Series Resonant Inverter that was used in the testing of the single-phase, 2.0-kw resonant AC power system breadboard is summarized. The architecture is descirbed and the driver modules of the 5.0 kw AC power system breadboard are analyzed. An investigation of the various types of transmission lines is continued. Measurements of equivalent series resistor and inductor and equivalent parallel capacitors are presented. In particular, a simplified approach is utilized to describe the optimal transmission line.

  10. Resolving Multi-path Interference in Time-of-Flight Imaging via Modulation Frequency Diversity and Sparse Regularization

    CERN Document Server

    Bhandari, Ayush; Whyte, Refael; Barsi, Christopher; Feigin, Micha; Dorrington, Adrian; Raskar, Ramesh

    2014-01-01

    Time-of-flight (ToF) cameras calculate depth maps by reconstructing phase shifts of amplitude-modulated signals. For broad illumination or transparent objects, reflections from multiple scene points can illuminate a given pixel, giving rise to an erroneous depth map. We report here a sparsity regularized solution that separates K-interfering components using multiple modulation frequency measurements. The method maps ToF imaging to the general framework of spectral estimation theory and has applications in improving depth profiles and exploiting multiple scattering.

  11. Investigation of noise in Lightwave Synthesized Frequency Sweeper seeded LIDAR anemometers from leakage through the Acousto Optic Modulators

    DEFF Research Database (Denmark)

    Pedersen, Anders Tegtmeier; Lindelöw, Per Jonas Petter

    2009-01-01

    Lightwave Synthesized Frequency Sweepers (LSFS) have potential use as lightsources in lidar anemometers. In this paper noise due to leakage in the acousto optic modulators in an LSFS is investigated. Theoretical expressions describing the build-up of noise in the LSFS due to leakage are derived...... Train (FSPT) modulated lidars the leakage will give rise to rapidly growing noise in the bins which corresponds to the signal from low radial wind velocities. It is likely that noise canceling techniques similar to those used for RIN removal has to be deployed for measurements of low wind velocities....

  12. Cancer versus FM radio polarization types.

    Science.gov (United States)

    Hallberg, Örjan

    2016-07-01

    In 2002, a detailed analysis of skin melanoma in 289 Swedish municipalities showed a strong association with the number of horizontally polarized main FM transmitters covering a municipality. Basic antenna theory says that body-resonance and standing waves cannot appear above a metal spring mattress unless the electric field is horizontally polarized. To test the hypothesis that body-resonant radiation can cause increased cancer risk in other European countries, I collected and analysed reported data from 24 countries, among which six were using vertical polarization. The results showed a strong association between cancer risk and the use of horizontally polarized FM broadcasting radiation, whereas vertical polarization seemed to cause no health effects. This information should form the basis for initiating relevant corrective actions by responsible authorities.

  13. FM Radio and Youth: Listeners or Users?

    Directory of Open Access Journals (Sweden)

    Marina Mučalo

    2014-06-01

    Full Text Available A survey conducted in the spring of 2013, says that Zagreb’s high school students are not regular listeners to FM radio programs. The dominant media is the Internet, which is used a few hours a day, mostly for Facebook. Despite the expressed need for music, the linear and passive nature of FM radio, does not correspond to the individual requirements of young and networked users. The Internet is the most popular daily source for music, with ability to download, while smartphones are becoming devices for storage and playback. However, this survey has shown that students are interested in web radio sites. Changes in media preferences and habits caused by the Internet show us the importance of information literacy, as a basic skill for participation in a networked society.

  14. Efficient FM Algorithm for VLSI Circuit Partitioning

    Directory of Open Access Journals (Sweden)

    M.RAJESH

    2013-04-01

    Full Text Available In FM algorithm initial partitioning matrix of the given circuit is assigned randomly, as a result for larger circuit having hundred or more nodes will take long time to arrive at the final partition if theinitial partitioning matrix is close to the final partitioning then the computation time (iteration required is small . Here we have proposed novel approach to arrive at initial partitioning by using spectralfactorization method the results was verified using several circuits.

  15. FM-HD RADIO的应用

    Institute of Scientific and Technical Information of China (English)

    黄文海

    2014-01-01

    结合中央塔FM-HD RADIO发射机,就HD RADIO技术应用于FM频段部分的频谱结构、发射机改造等方面进行阐述,并利用北京地区的测试数据说明现阶段该技术在FM频段的应用.

  16. Modulated Pulse Generations in a Laser-diode-pumped Passively Q-switched Intracavity-frequency-doubling Nd∶YVO4 Laser

    Institute of Scientific and Technical Information of China (English)

    郑加安; 赵圣之; 陈磊

    2002-01-01

    The investigative results of modulated pulse output from an LD end-pumped passively Q-switched intracavity-frequency-doubling Nd∶YVO4/KTP laser with Cr4+∶YAG saturable absorber are presented. The numerical stimulations of these modulated pulses are carried out basing on the rate equations. It indicated that the modulations are attribute to the frequency beating of two eigenstates of the resonant polarized modes. The theoretical calculations are in good agreement with the experimental observations.

  17. Effects of GSM modulated radio-frequency electromagnetic radiation on permeability of blood-brain barrier in male & female rats.

    Science.gov (United States)

    Sırav, Bahriye; Seyhan, Nesrin

    2016-09-01

    With the increased use of mobile phones, their biological and health effects have become more important. Usage of mobile phones near the head increases the possibility of effects on brain tissue. This study was designed to investigate the possible effects of pulse modulated 900MHz and 1800MHz radio-frequency radiation on the permeability of blood-brain barrier of rats. Study was performed with 6 groups of young adult male and female wistar albino rats. The permeability of blood-brain barrier to intravenously injected evans blue dye was quantitatively examined for both control and radio-frequency radiarion exposed groups. For male groups; Evans blue content in the whole brain was found to be 0.08±0.01mg% in the control, 0.13±0.03mg% in 900MHz exposed and 0.26±0.05mg% in 1800MHz exposed animals. In both male radio-frequency radiation exposed groups, the permeability of blood-brain barrier found to be increased with respect to the controls (pradio-frequency radiation exposure was found more effective on the male animals (p0.01). However 900MHz pulse modulated radio-frequency exposure was found effective on the permeability of blood-brain barrier of female animals. Results have shown that 20min pulse modulated radio-frequency radiation exposure of 900MHz and 1800MHz induces an effect and increases the permeability of blood-brain barrier of male rats. For females, 900MHz was found effective and it could be concluded that this result may due to the physiological differences between female and male animals. The results of this study suggest that mobile phone radation could lead to increase the permeability of blood-brain barrier under non-thermal exposure levels. More studies are needed to demonstrate the mechanisms of that breakdown.

  18. 75 FR 19340 - FM TABLE OF ALLOTMENTS, Jewett, Texas

    Science.gov (United States)

    2010-04-14

    ... COMMISSION 47 CFR Part 73 FM TABLE OF ALLOTMENTS, Jewett, Texas AGENCY: Federal Communications Commission..., proposing the allotment of FM Channel 232A at Jewett, Texas, as a first local service. The reference.... Section 73.202(b), the Table of FM Allotments under Texas, is ameded by adding Jewett, Channe 232A...

  19. 47 CFR 73.599 - NCE-FM engineering charts.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false NCE-FM engineering charts. 73.599 Section 73.599 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.599 NCE-FM engineering charts. This...

  20. Longitudinal dielectric permeability into quantum degenerate plasma with frequency of collisions proportional to the module of a wave vector

    CERN Document Server

    Latyshev, A V

    2013-01-01

    Formulas for the longitudinal dielectric permeability in quantum degenerate collisional plasma with the frequency of collisions proportional to the module of the wave vector, in Mermin's approach, are received. Equation of Shr\\"{o}dinger - Boltzmann with integral of collisions relaxation type in Mermin's approach is applied. It is spent numerical and graphic comparison of the real and imaginary parts of dielectric function of non-degenerate and maxwellian collisional quantum plasma with a constant and a variable frequencies of collisions. It is shown, that the longitudinal dielectric function weakly depends on a wave vector.

  1. Evaluation of closure strategies for a periodically-forced Duffing oscillator with slowly modulated frequency subject to Gaussian white noise

    Science.gov (United States)

    Yalim, Jason; Welfert, Bruno D.; Lopez, Juan M.

    2017-03-01

    The response of a Duffing oscillator subject to a periodic forcing with slowly and stochastically modulated frequency is analyzed numerically. The results of both moment and cumulant-based stochastic reductions are compared to Monte Carlo simulations. It is shown how the explicit characterization of higher-order central moments of the (Gaussian) noise source and the periodic nature of the forcing enable a reliable reduction strategy providing a faithful description of the mean behavior of stochastic solutions. The reduced model is then used to illustrate how a large noise level and fast frequency drift may combine to sustain a strong response that is normally associated to resonance in the noiseless static case.

  2. Contribution of third-harmonic and negative frequency polarization fields to self-phase modulation in nonlinear media

    CERN Document Server

    Loures, Cristian Redondo; Biancalana, Fabio

    2014-01-01

    We study the influence of third-harmonic generation (THG) and negative frequency polarization terms in the self-phase modulation (SPM) of short and intense pulses in Kerr media. We find that THG induces additional symmetric lobes in the SPM process. The amplitude of these new sidebands are greatly enhanced by the contributions of the negative frequency Kerr (NFK) term and the shock operator. We compare our theoretical predictions based on the analytical nonlinear phase with simulations carried out by using the full unidirectional pulse propagation equation (UPPE).

  3. High Resolution Pulse Compression Imaging Using Super Resolution FM-Chirp Correlation Method (SCM)

    Science.gov (United States)

    Fujiwara, M.; Okubo, K.; Tagawa, N.

    This study addresses the issue of the super-resolution pulse compression technique (PCT) for ultrasound imaging. Time resolution of multiple ultrasonic echoes using the FM-Chirp PCT is limited by the bandwidth of the sweep-frequency. That is, the resolution depends on the sharpness of auto-correlation function. We propose the Super resolution FM-Chirp correlation Method (SCM) and evaluate its performance. This method is based on the multiple signal classification (MUSIC) algorithm. Our simulations were made for the model assuming multiple signals reflected from some scatterers. We confirmed that SCM detects time delay of complicated reflected signals successfully with high resolution.

  4. Performance analysis of digital FM demodulators for fading channels in the threshold region

    Science.gov (United States)

    Dharamsi, M. T.; Gupta, S. C.

    1976-01-01

    The quasi-optimum digital FM demodulators for fading channels reported earlier (1975) reflected the system performance accurately under high signal to noise ratio conditions. In this paper, the prediction of the system performance for low SNR values is considered. A new set of error variance algorithms is developed from the filter algorithm assuming a Gaussian distribution for the state estimation errors and taking the effect of high frequency terms into consideration. Simulation analysis for an FM system with Rician fading channel shows that these algorithms predict the system performance accurately in the threshold region.

  5. Spatial Frequency Dependence of the Human Visual Cortex Response on Temporal Frequency Modulation Studied by fMRI

    Directory of Open Access Journals (Sweden)

    A. Mirzajani

    2006-07-01

    Full Text Available Background/Objective: The brain response to temporal frequencies (TF has been already reported. However, there is no study on different TF with respect to various spatial frequencies (SF. Materials and Methods: Functional magnetic resonance imaging (fMRI was done by a 1.5 T General Electric system for 14 volunteers (9 males and 5 females, aged 19–26 years during square-wave reversal checkerboard visual stimulation with different temporal frequencies of 4, 6, 8 and 10 Hz in 2 states of low SF of 0.4 and high SF of 8 cycles/degree (cpd. All subjects had normal visual acuity of 20/20 based on Snellen’s fraction in each eye with good binocular vision and normal visual field based on confrontation test. The mean luminance of the entire checkerboard was 161.4 cd/m2 and the black and white check contrast was 96%. The activation map was created using the data obtained from the block designed fMRI study. Pixels with a Z score above a threshold of 2.3, at a statistical significance level of 0.05, were considered activated. The average percentage blood oxygenation level dependent (BOLD signal change for all activated pixels within the occipital lobe, multiplied by the total number of activated pixels within the occipital lobe, was used as an index for the magnitude of the fMRI signal at each state of TF&SF. Results: The magnitude of the fMRI signal in response to different TF’s was maximum at 6 Hz for a high SF value of 8 cpd; it was however, maximum at a TF of 8 Hz for a low SF of 0.4 cpd. Conclusion: The results of this study agree with those of animal invasive neurophysiologic studies showing SF and TF selectivity of neurons in visual cortex. These results can be useful for vision therapy and selecting visual tasks in fMRI studies.

  6. Pyroelectric detectors with integrated operational amplifier for high modulation frequencies; Pyroelektrische Detektoren mit integriertem Operationsverstaerker fuer hohe Modulationsfrequenzen

    Energy Technology Data Exchange (ETDEWEB)

    Neumann, N.; Saenze, H.; Heinze, M. [InfraTec GmbH Dresden (Germany)

    2006-02-01

    In order to use the advantages of the current mode operation a pyroelectric detector family with integrated transimpedance amplifier (TIA) was developed particularly for modulation frequencies up to the kHz range with a simplified external circuitry for new application fields, e.g. absorption spectroscopy using quantum-cascade-laser. The essential advantages of the TIA arise from the small electrical time constant {tau}{sub E} and the short-circuiting of the pyroelectric element. A flat amplitude response up to some kHz was aimed at for a sufficiently high response of 7500 V/W, appr., also at high modulation frequencies. This can be achieved through a electrical time constant of 1 ms or less and a wide bandwidth of the op amp. The article describes in detail how these demands were accomplished and which compromises had to be accepted. (orig.)

  7. Low-Voltage, Low-Power, and Wide-Tuning-Range Ring-VCO for Frequency ΔΣ Modulator

    DEFF Research Database (Denmark)

    Tuan Vu, Cao; Wisland, Dag T.; Lande, Tor Sverre

    A low-voltage, low-power, and wide-tuning-range VCO which converts an analog input voltage to phase information for a frequency ΔΣ modulator is proposed in this paper. The VCO is based on a differential ring oscillator, which is improved with modified symmetric load and a positive feedback...... in the differential delay cells, a new bias circuit and a full-swing amplifier. The proposed VCO operating with two stages at a power supply voltage of 0.6 V can achieve wide tuning-range and low power consumption of 176.892 uW. The new VCO has a good linearity reducing harmonic distortion for frequency ΔΣ modulator...

  8. Near-field light detection of a photo induced force by atomic force microscopy with frequency modulation

    Science.gov (United States)

    Satoh, Nobuo; Kobayashi, Kei; Matsushige, Kazumi; Yamada, Hirofumi

    2017-08-01

    We demonstrated near-field light detection using a non contact-mode atomic force microscope (nc-AFM). This system obtains molecular-level resolution by reducing noise in the displacement detection of a Si cantilever. The Si cantilever probe tip was brought close to a glass with a patterned chromium film on a dove prism. The backside of the prism was irradiated by an intensity-modulated laser light to create an evanescent field at the glass surface. We obtained a near-field optical image of the chromium-patterned glass by detecting the amplitude modulation induced by the near-field light while the tip-sample distance was regulated by the frequency modulation method under atmospheric conditions.

  9. Cascade photonic integrated circuit architecture for electro-optic in-phase quadrature/single sideband modulation or frequency conversion.

    Science.gov (United States)

    Hasan, Mehedi; Hall, Trevor

    2015-11-01

    A photonic integrated circuit architecture for implementing frequency upconversion is proposed. The circuit consists of a 1×2 splitter and 2×1 combiner interconnected by two stages of differentially driven phase modulators having 2×2 multimode interference coupler between the stages. A transfer matrix approach is used to model the operation of the architecture. The predictions of the model are validated by simulations performed using an industry standard software tool. The intrinsic conversion efficiency of the proposed design is improved by 6 dB over the alternative functionally equivalent circuit based on dual parallel Mach-Zehnder modulators known in the prior art. A two-tone analysis is presented to study the linearity of the proposed circuit, and a comparison is provided over the alternative. The proposed circuit is suitable for integration in any platform that offers linear electro-optic phase modulation such as LiNbO(3), silicon, III-V, or hybrid technology.

  10. Attitude Control of Satellite With Pulse-Width Pulse- Frequency (PWPF Modulator Using Generalized Incremental Predictive Control

    Directory of Open Access Journals (Sweden)

    Ehsan Chegeni

    2014-09-01

    Full Text Available In this paper, we use generalized incremental predictive control (GIPC to stabilize attitude of satellite. We compare Generalized Predictive Control (GPC with GIPC algorithm and present that GIPC has better performance. The three-axis attitude control systems are activated in pulse mode. Consequently, a modulation of the torque command is compelling in order to avoid high non-linear control action. This work considers the Pulse-Width Pulse-Frequency modulator (PWPF is composed of a Schmitt trigger, a first order filter, and a feedback loop. PWPF modulator has several advantages over classical bang-bang controllers such as close to linear operation, high accuracy, and reduced propellant consumption

  11. Real-time implementation of frequency-modulated continuous-wave synthetic aperture radar imaging using field programmable gate array.

    Science.gov (United States)

    Quan, Yinghui; Li, Yachao; Hu, Guibin; Xing, Mengdao

    2015-06-01

    A new miniature linear frequency-modulated continuous-wave radar which mounted on an unmanned aerial vehicle is presented. It allows the accomplishment of high resolution synthetic aperture radar imaging in real-time. Only a Kintex-7 field programmable gate array from Xilinx is utilized for whole signal processing of sophisticated radar imaging algorithms. The proposed hardware architecture achieves remarkable improvement in integration, power consumption, volume, and computing performance over its predecessor designs. The realized design is verified by flight campaigns.

  12. Modulation-frequency dependencies of the intensity and the phase delay of photoinduced absorption from conjugated polymers

    Science.gov (United States)

    Furukawa, Yukio

    2000-03-01

    The modulation-frequency dependencies of the intensity and the phase delay of photoinduced infrared absorption from poly(p-phenylene) have been observed and simulated numerically on the basis of a model based on second-order kinetics involving a neutralization recombination process between the positive and negative charge carriers (polarons) that are formed from a photogenerated polaron pair (interchain charge-transfer exciton). The rate constant of the bimolecular recombination has been obtained.

  13. Nonlinear magneto-optical rotation of frequency-modulated light resonant with a low-J transition

    CERN Document Server

    Malakyan, Y P; Budker, D; Kimball, D F; Yashchuk, V V; Malakyan, Yu. P.

    2003-01-01

    A low-light-power theory of nonlinear magneto-optical rotation of frequency-modulated light resonant with a J=1->J'=0 transition is presented. The theory is developed for a Doppler-free transition, and then modified to account for Doppler broadening and velocity mixing due to collisions. The results of the theory are shown to be in qualitative agreement with experimental data obtained for the rubidium D1 line.

  14. Effects of Carrier Frequency Offset, Timing Offset, and Channel Spread Factor on the Performance of Hexagonal Multicarrier Modulation Systems

    Directory of Open Access Journals (Sweden)

    Xu Kui

    2009-01-01

    Full Text Available Abstract Hexagonal multicarrier modulation (HMM system is the technique of choice to overcome the impact of time-frequency dispersive transmission channel. This paper examines the effects of insufficient synchronization (carrier frequency offset, timing offset on the amplitude and phase of the demodulated symbol by using a projection receiver in hexagonal multicarrier modulation systems. Furthermore, effects of CFO, TO, and channel spread factor on the performance of signal-to-interference-plus-noise ratio (SINR in hexagonal multicarrier modulation systems are further discussed. The exact SINR expression versus insufficient synchronization and channel spread factor is derived. Theoretical analysis shows that similar degradation on symbol amplitude and phase caused by insufficient synchronization is incurred as in traditional cyclic prefix orthogonal frequency-division multiplexing (CP-OFDM transmission. Our theoretical analysis is confirmed by numerical simulations in a doubly dispersive (DD channel with exponential delay power profile and U-shape Doppler power spectrum, showing that HMM systems outperform traditional CP-OFDM systems with respect to SINR against ISI/ICI caused by insufficient synchronization and doubly dispersive channel.

  15. Spatiotemporal evolution of a cosine-modulated stationary field and Kerr frequency comb generation in a microresonator.

    Science.gov (United States)

    Hu, Xiaohong; Liu, Yuanshan; Xu, Xin; Feng, Ye; Zhang, Wenfu; Wang, Weiqiang; Song, Jiazheng; Wang, Yishan; Zhao, Wei

    2015-10-10

    Based on the normalized spatiotemporal Lugiato-Lefever equation, the evolutions of cosine-modulated stationary fields relating to the generation of single-free spectral range (FSR) or multi-FSR Kerr frequency combs in a microresonator with anomalous dispersion are studied numerically. The research results show that a single-FSR comb arises when a dissipative soliton pulse or multiple nonequidistant soliton pulses form in the cavity. Compared with the smooth and regular spectral structure of a single soliton pulse, the comb corresponding to the uneven distribution of multiple soliton pulses exhibits a complex and irregular profile. When the stable intracavity field consists of a "roll" Turing pattern or N(N>1) evenly distributed soliton pulses separated by 2π/N, multi-FSR combs can be generated. In the case of the "roll" Turing pattern solution, it is found that third-order dispersion could modify the comb mode spacing and decrease the intensity of high-order comb modes. For the situation of multiple soliton pulse generation, the simulation results indicate that both the number and locations of the soliton pulses can be actively controlled through the careful selection of modulation frequency. In addition, for the selected cosine-modulated initial field profile, only those modes with the mode numbers being equal to an integer multiple of N can be greatly amplified by the parametric gain during propagation in the microresonator. This process eventually leads to the formation of a N-FSR frequency comb.

  16. Effects of Carrier Frequency Offset, Timing Offset, and Channel Spread Factor on the Performance of Hexagonal Multicarrier Modulation Systems

    Directory of Open Access Journals (Sweden)

    Kui Xu

    2009-01-01

    Full Text Available Hexagonal multicarrier modulation (HMM system is the technique of choice to overcome the impact of time-frequency dispersive transmission channel. This paper examines the effects of insufficient synchronization (carrier frequency offset, timing offset on the amplitude and phase of the demodulated symbol by using a projection receiver in hexagonal multicarrier modulation systems. Furthermore, effects of CFO, TO, and channel spread factor on the performance of signal-to-interference-plus-noise ratio (SINR in hexagonal multicarrier modulation systems are further discussed. The exact SINR expression versus insufficient synchronization and channel spread factor is derived. Theoretical analysis shows that similar degradation on symbol amplitude and phase caused by insufficient synchronization is incurred as in traditional cyclic prefix orthogonal frequency-division multiplexing (CP-OFDM transmission. Our theoretical analysis is confirmed by numerical simulations in a doubly dispersive (DD channel with exponential delay power profile and U-shape Doppler power spectrum, showing that HMM systems outperform traditional CP-OFDM systems with respect to SINR against ISI/ICI caused by insufficient synchronization and doubly dispersive channel.

  17. Focusing vibrating targets in frequency-modulation continuous-wave-synthetic aperture radar with Doppler keystone transform

    Science.gov (United States)

    Hu, Yuxin; Zhang, Yuan; Sun, Jinping; Lei, Peng

    2016-04-01

    Vibrating targets generally induce sinusoidal micro-Doppler modulation in high resolution synthetic aperture radar (SAR). They could cause defocused and ghost results by conventional imaging algorithms. This paper proposes a method on vibrating target imaging in frequency-modulation continuous-wave (FMCW) SAR systems. The continuous motion of sensor platform during pulse time is considered in the signal model. Based on Bessel series expansion of the signal in the azimuth direction, the influence of platform motion on the azimuth frequency is eliminated after dechirp and deskew. In addition, the range walk is compensated in the two-dimensional frequency domain by Doppler keystone transform. Next, using range cell migration correction, the azimuth quadratic phase compensation and the range curvature correction are made in range-Doppler domain for the focus of paired echoes. The residual video phase of paired echoes is eliminated, and vibration parameters are estimated to compensate in the sinusoidal modulation phase. Then the deghosted image of vibrating targets can be obtained. The proposed method is applicable to multiple targets with various vibrating states due to no need of a priori knowledge of targets. Finally, simulations are carried out to validate the effectiveness of the method in FMCW-SAR imaging of vibrating targets.

  18. Spatial Frequency Components of Images Modulate Neuronal Activity in Monkey Amygdala.

    Science.gov (United States)

    Montes-Lourido, Pilar; Bermudez, M A; Romero, M C; Vicente, A F; Gonzalez, F

    2016-04-01

    Processing the spatial frequency components of an image is a crucial feature for visual perception, especially in recognition of faces. Here, we study the correlation between spatial frequency components of images of faces and neuronal activity in monkey amygdala while performing a visual recognition task. The frequency components of the images were analyzed using a fast Fourier transform for 40 spatial frequency ranges. We recorded 65 neurons showing statistically significant responses to at least one of the images used as a stimulus. A total of 37 of these neurons (n = 37) showed significant responses to at least three images, and in eight of them (8/37, 22%), we found a statistically significant correlation between neuron response and the modulus amplitude of at least one frequency range present in the images. Our results indicate that high spatial frequency and low spatial frequency components of images influence the activity of amygdala neurons.

  19. Monocular and binocular steady-state flicker VEPs: frequency-response functions to sinusoidal and square-wave luminance modulation.

    Science.gov (United States)

    Nicol, David S; Hamilton, Ruth; Shahani, Uma; McCulloch, Daphne L

    2011-02-01

    Steady-state VEPs to full-field flicker (FFF) using sinusoidally modulated light were compared with those elicited by square-wave modulated light across a wide range of stimulus frequencies with monocular and binocular FFF stimulation. Binocular and monocular VEPs were elicited in 12 adult volunteers to FFF with two modes of temporal modulation: sinusoidal or square-wave (abrupt onset and offset, 50% duty cycle) at ten temporal frequencies ranging from 2.83 to 58.8 Hz. All stimuli had a mean luminance of 100 cd/m(2) with an 80% modulation depth (20-180 cd/m(2)). Response magnitudes at the stimulus frequency (F1) and at the double and triple harmonics (F2 and F3) were compared. For both sinusoidal and square-wave flicker, the FFF-VEP magnitudes at F1 were maximal for 7.52 Hz flicker. F2 was maximal for 5.29 Hz flicker, and F3 magnitudes are largest for flicker stimulation from 3.75 to 7.52 Hz. Square-wave flicker produced significantly larger F1 and F2 magnitudes for slow flicker rates (up to 5.29 Hz for F1; at 2.83 and 3.75 Hz for F2). The F3 magnitudes were larger overall for square-wave flicker. Binocular FFF-VEP magnitudes are larger than those of monocular FFF-VEPs, and the amount of this binocular enhancement is not dependant on the mode of flicker stimulation (mean binocular: monocular ratio 1.41, 95% CI: 1.2-1.6). Binocular enhancement of F1 for 21.3 Hz flicker was increased to a factor of 2.5 (95% CI: 1.8-3.5). In the healthy adult visual system, FFF-VEP magnitudes can be characterized by the frequency-response functions of F1, F2 and F3. Low-frequency roll-off in the FFF-VEP magnitudes is greater for sinusoidal flicker than for square-wave flicker for rates ≤ 5.29 Hz; magnitudes for higher-frequency flicker are similar for the two types of flicker. Binocular FFF-VEPs are larger overall than those recorded monocularly, and this binocular summation is enhanced at 21.3 Hz in the mid-frequency range.

  20. Detection of objects in sandy ground by an FM-CW radar

    OpenAIRE

    Yamaguchi, Y.(International Center for Elementary Particle Physics and Department of Physics, The University of Tokyo, Tokyo, Japan); Tsurugi, M.; Watanabe, Y.; Sengoku, M.; Kikuta, T.; Nishino, M; Tsunasaki, M.; Yamaguchi, Yoshio; Sengoku, Masakazu; 山口, 芳雄; 仙石, 正和

    1993-01-01

    An FM-CW radar system for the detection of objects buried in sandy ground is explored and applied to field measurement. The key factors for underground radar performance are the center frequency and the bandwidth determining the depth at which the radar can detect targets and the resolution in the range direction, respectively. To realize a practical underground radar, two ridged horn antennas are employed in the system, which are operative in the frequency range of 250-1000 MHz. The impedanc...

  1. The method of «blind» carrier frequency estimation of radio signals with linear digital modulation

    Directory of Open Access Journals (Sweden)

    Nahornyuk О.А.

    2017-04-01

    Full Text Available Carrier frequency estimation in the conditions of a priori uncertainty of signal modulation and parameters is prerequisite for realization of frequency synchronization circuits in software-defined radio. To implement this operation the method of «blind» carrier frequency estimation of radio signals with amplitude, phase and quadrature-amplitude shift keying, which does not require prior information about modulation type, signal and communication channel parameters, is proposed in the article. The basis of method is calculation of constellation symbols cross-correlation and clock synchronization by Gardner method. As opposed to known approaches proposed method does not require two-dimensional objective function calculation which can reduce the number of computing operations. This is achieved by implementation of previous clock synchronization and reducing the two-dimensional objective function in one-dimensional. Verification of developed method is carried out by statistical modeling using more than 20 types of phase constellations. The practical significance of received results consists in reduction of carrier frequency estimation time and simplification of practical implementation at the expense of employment of approved clock synchronization circuits.

  2. Word Type Frequency Alone Can Modulate Hemispheric Asymmetry in Visual Word Recognition: Evidence from Modeling Chinese Character Recognition

    Directory of Open Access Journals (Sweden)

    Janet H. Hsiao

    2011-05-01

    Full Text Available In Chinese orthography, a dominant structure exists in which a semantic radical appears on the left and a phonetic radical on the right (SP characters; the minority, opposite arrangement also exists (PS characters. Recent studies showed that SP character processing is more left hemisphere (LH lateralized than PS character processing; nevertheless, it remains unclear whether this is due to phonetic radical position or character type frequency. Through computational modeling with artificial lexicons, in which we implement a theory of hemispheric asymmetry in perception that posits differential frequency bias in the two hemispheres (i.e., the DFF theory; Ivry & Robertson, 1998, but do not assume phonological processing being LH lateralized, we show that although phonetic radical position, visual complexity of the radicals, and character information structure may all modulate lateralization effects, the difference in character type frequency alone is sufficient to exhibit the effect that the dominant type has a stronger LH lateralization than the minority type. Further analysis suggests that this effect is due to higher visual similarity among characters in the dominant type as compared with those in the minority type. This result demonstrates that word type frequency alone can modulate hemispheric lateralization effects in visual word recognition.

  3. Word Type Frequency Alone Can Modulate Hemispheric Asymmetry in Visual Word Recognition: Evidence from Modeling Chinese Character Recognition

    Science.gov (United States)

    Hsiao, Janet H.; Cheung, Kit

    2011-01-01

    In Chinese orthography, a dominant structure exists in which a semantic radical appears on the left and a phonetic radical on the right (SP characters); the minority, opposite arrangement also exists (PS characters). Recent studies showed that SP character processing is more left hemisphere (LH) lateralized than PS character processing; nevertheless, it remains unclear whether this is due to phonetic radical position or character type frequency. Through computational modeling with artificial lexicons, in which we implement a theory of hemispheric asymmetry in perception that posits differential frequency bias in the two hemispheres (i.e., the DFF theory; Ivry & Robertson, 1998), but do not assume phonological processing being LH lateralized, we show that although phonetic radical position, visual complexity of the radicals, and character information structure may all modulate lateralization effects, the difference in character type frequency alone is sufficient to exhibit the effect that the dominant type has a stronger LH lateralization than the minority type. Further analysis suggests that this effect is due to higher visual similarity among characters in the dominant type as compared with those in the minority type. This result demonstrates that word type frequency alone can modulate hemispheric lateralization effects in visual word recognition.

  4. An Approach for Synthesis of Modulated -Channel FIR Filter Banks Utilizing the Frequency-Response Masking Technique

    Directory of Open Access Journals (Sweden)

    Rosenbaum Linnéa

    2007-01-01

    Full Text Available The frequency-response masking (FRM technique was introduced as a means of generating linear-phase FIR filters with narrow transition band and low arithmetic complexity. This paper proposes an approach for synthesizing modulated maximally decimated FIR filter banks (FBs utilizing the FRM technique. A new tailored class of FRM filters is introduced and used for synthesizing nonlinear-phase analysis and synthesis filters. Each of the analysis and synthesis FBs is realized with the aid of only three subfilters, one cosine-modulation block, and one sine-modulation block. The overall FB is a near-perfect reconstruction (NPR FB which in this case means that the distortion function has a linear-phase response but small magnitude errors. Small aliasing errors are also introduced by the FB. However, by allowing these small errors (that can be made arbitrarily small, the arithmetic complexity can be reduced. Compared to conventional cosine-modulated FBs, the proposed ones lower significantly the overall arithmetic complexity at the expense of a slightly increased overall FB delay in applications requiring narrow transition bands. Compared to other proposals that also combine cosine-modulated FBs with the FRM technique, the arithmetic complexity can typically be reduced by in specifications with narrow transition bands. Finally, a general design procedure is given for the proposed FBs and examples are included to illustrate their benefits.

  5. An Approach for Synthesis of Modulated M-Channel FIR Filter Banks Utilizing the Frequency-Response Masking Technique

    Directory of Open Access Journals (Sweden)

    Håkan Johansson

    2007-01-01

    Full Text Available The frequency-response masking (FRM technique was introduced as a means of generating linear-phase FIR filters with narrow transition band and low arithmetic complexity. This paper proposes an approach for synthesizing modulated maximally decimated FIR filter banks (FBs utilizing the FRM technique. A new tailored class of FRM filters is introduced and used for synthesizing nonlinear-phase analysis and synthesis filters. Each of the analysis and synthesis FBs is realized with the aid of only three subfilters, one cosine-modulation block, and one sine-modulation block. The overall FB is a near-perfect reconstruction (NPR FB which in this case means that the distortion function has a linear-phase response but small magnitude errors. Small aliasing errors are also introduced by the FB. However, by allowing these small errors (that can be made arbitrarily small, the arithmetic complexity can be reduced. Compared to conventional cosine-modulated FBs, the proposed ones lower significantly the overall arithmetic complexity at the expense of a slightly increased overall FB delay in applications requiring narrow transition bands. Compared to other proposals that also combine cosine-modulated FBs with the FRM technique, the arithmetic complexity can typically be reduced by 40% in specifications with narrow transition bands. Finally, a general design procedure is given for the proposed FBs and examples are included to illustrate their benefits.

  6. Spectral self-imaging of time-periodic coherent frequency combs by parabolic cross-phase modulation.

    Science.gov (United States)

    Maram, Reza; Azaña, José

    2013-11-18

    Integer and fractional spectral self-imaging effects are induced on infinite-duration periodic frequency combs (probe signal) using cross-phase modulation (XPM) with a parabolic pulse train as pump signal. Free-spectral-range tuning (fractional effects) or wavelength-shifting (integer effects) of the frequency comb can be achieved by changing the parabolic pulse peak power or/and repetition rate without affecting the spectral envelope shape and bandwidth of the original comb. For design purposes, we derive the complete family of different pump signals that allow implementing a desired spectral self-imaging process. Numerical simulation results validate our theoretical analysis. We also investigate the detrimental influence of group-delay walk-off and deviations in the nominal temporal shape or power of the pump pulses on the generated output frequency combs.

  7. Multi-pulse frequency shifted (MPFS) multiple access modulation for ultra wideband

    Science.gov (United States)

    Nekoogar, Faranak [San Ramon, CA; Dowla, Farid U [Castro Valley, CA

    2012-01-24

    The multi-pulse frequency shifted technique uses mutually orthogonal short duration pulses o transmit and receive information in a UWB multiuser communication system. The multiuser system uses the same pulse shape with different frequencies for the reference and data for each user. Different users have a different pulse shape (mutually orthogonal to each other) and different transmit and reference frequencies. At the receiver, the reference pulse is frequency shifted to match the data pulse and a correlation scheme followed by a hard decision block detects the data.

  8. Inhibitory projections from the ventral nucleus of the lateral lemniscus and superior paraolivary nucleus create directional selectivity of frequency modulations in the inferior colliculus: a comparison of bats with other mammals.

    Science.gov (United States)

    Pollak, George D; Gittelman, Joshua X; Li, Na; Xie, Ruili

    2011-03-01

    This review considers four auditory brainstem nuclear groups and shows how studies of both bats and other mammals have provided insights into their response properties and the impact of their convergence in the inferior colliculus (IC). The four groups are octopus cells in the cochlear nucleus, their connections with the ventral nucleus of the lateral lemniscus (VNLL) and the superior paraolivary nucleus (SPON), and the connections of the VNLL and SPON with the IC. The theme is that the response properties of neurons in the SPON and VNLL map closely onto the synaptic response features of a unique subpopulation of cells in the IC of bats whose inputs are dominated by inhibition. We propose that the convergence of VNLL and SPON inputs generates the tuning of these IC cells, their unique temporal responses to tones, and their directional selectivities for frequency modulated (FM) sweeps. Other IC neurons form directional properties in other ways, showing that selective response properties are formed in multiple ways. In the final section we discuss why multiple formations of common response properties could amplify differences in population activity patterns evoked by signals that have similar spectrotemporal features.

  9. Colossal magneto-optical modulation at terahertz frequencies by counterpropagating femtosecond laser pulses in Tbsub>3sub>Gasub>5sub>Osub>12sub>.

    Science.gov (United States)

    Mikhaylovskiy, Rostislav V; Subkhangulov, Ruslan R; Rasing, Theo; Kimel, Alexey V

    2016-11-01

    Single-frequency terahertz modulation of the magneto-optical Faraday effect with a record amplitude of the polarization rotation of ∼0.5° is achieved using a slab of the etalon Faraday rotator crystal Tbsub>3sub>Gasub>5sub>Osub>12sub>. The modulation is the result of the interaction of two counterpropagating laser pulses via the optical Kerr effect. The frequency of the modulation is determined by the applied magnetic field and is continuously tunable in a terahertz frequency range between 0 and 0.7 THz.

  10. Frequency-domain equalization for OFDMA-based multiuser MIMO systems with improper modulation schemes

    Science.gov (United States)

    Xiao, Pei; Lin, Zihuai; Fagan, Anthony; Cowan, Colin; Vucetic, Branka; Wu, Yi

    2011-12-01

    In this paper, we propose a novel transceiver structure for orthogonal frequency division multiple access-based uplink multiuser multiple-input multiple-output systems. The numerical results show that the proposed frequency-domain equalization schemes significantly outperform conventional linear minimum mean square error-based equalizers in terms of bit error rate performance with moderate increase in computational complexity.

  11. Photonic integrated single-sideband modulator / frequency shifter based on surface acoustic waves

    DEFF Research Database (Denmark)

    Barretto, Elaine Cristina Saraiva; Hvam, Jørn Märcher

    2010-01-01

    Optical frequency shifters are essential components of many systems. In this paper, a compact integrated optical frequency shifter is designed making use of the combination of surface acoustic waves and Mach-Zehnder interferometers. It has a very simple operation setup and can be fabricated...

  12. ERP Correlates of Letter Identity and Letter Position Are Modulated by Lexical Frequency

    Science.gov (United States)

    Vergara-Martinez, Marta; Perea, Manuel; Gomez, Pablo; Swaab, Tamara Y.

    2013-01-01

    The encoding of letter position is a key aspect in all recently proposed models of visual-word recognition. We analyzed the impact of lexical frequency on letter position assignment by examining the temporal dynamics of lexical activation induced by pseudowords extracted from words of different frequencies. For each word (e.g., BRIDGE), we created…

  13. Optimization of A 2-Micron Laser Frequency Stabilization System for a Double-Pulse CO2 Differential Absorption Lidar

    Science.gov (United States)

    Chen, Songsheng; Yu, Jirong; Bai, Yingsin; Koch, Grady; Petros, Mulugeta; Trieu, Bo; Petzar, Paul; Singh, Upendra N.; Kavaya, Michael J.; Beyon, Jeffrey

    2010-01-01

    A carbon dioxide (CO2) Differential Absorption Lidar (DIAL) for accurate CO2 concentration measurement requires a frequency locking system to achieve high frequency locking precision and stability. We describe the frequency locking system utilizing Frequency Modulation (FM), Phase Sensitive Detection (PSD), and Proportional Integration Derivative (PID) feedback servo loop, and report the optimization of the sensitivity of the system for the feed back loop based on the characteristics of a variable path-length CO2 gas cell. The CO2 gas cell is characterized with HITRAN database (2004). The method can be applied for any other frequency locking systems referring to gas absorption line.

  14. The frequency of hippocampal theta rhythm is modulated on a circadian period and is entrained by food availability.

    Science.gov (United States)

    Munn, Robert G K; Tyree, Susan M; McNaughton, Neil; Bilkey, David K

    2015-01-01

    The hippocampal formation plays a critical role in the generation of episodic memory. While the encoding of the spatial and contextual components of memory have been extensively studied, how the hippocampus encodes temporal information, especially at long time intervals, is less well understood. The activity of place cells in hippocampus has previously been shown to be modulated at a circadian time-scale, entrained by a behavioral stimulus, but not entrained by light. The experimental procedures used in the previous study of this phenomenon, however, necessarily conflated two alternative entraining stimuli, the exposure to the recording environment and the availability of food, making it impossible to distinguish between these possibilities. Here we demonstrate that the frequency of theta-band hippocampal EEG varies with a circadian period in freely moving animals and that this periodicity mirrors changes in the firing rate of hippocampal neurons. Theta activity serves, therefore, as a proxy of circadian-modulated hippocampal neuronal activity. We then demonstrate that the frequency of hippocampal theta driven by stimulation of the reticular formation also varies with a circadian period. Because this effect can be observed without having to feed the animal to encourage movement we were able to identify what stimulus entrains the circadian oscillation. We show that with reticular-activated recordings started at various times of the day the frequency of theta varies quasi-sinusoidally with a 25 h period and phase-aligned when referenced to the animal's regular feeding time, but not the recording start time. Furthermore, we show that theta frequency consistently varied with a circadian period when the data obtained from repeated recordings started at various times of the day were referenced to the start of food availability in the recording chamber. This pattern did not occur when data were referenced to the start of the recording session or to the actual time of day

  15. Optimal space communications techniques. [all digital phase locked loop for FM demodulation

    Science.gov (United States)

    Schilling, D. L.

    1973-01-01

    The design, development, and analysis are reported of a digital phase-locked loop (DPLL) for FM demodulation and threshold extension. One of the features of the developed DPLL is its synchronous, real time operation. The sampling frequency is constant and all the required arithmetic and logic operations are performed within one sampling period, generating an output sequence which is converted to analog form and filtered. An equation relating the sampling frequency to the carrier frequency must be satisfied to guarantee proper DPLL operation. The synchronous operation enables a time-shared operation of one DPLL to demodulate several FM signals simultaneously. In order to obtain information about the DPLL performance at low input signal-to-noise ratios, a model of an input noise spike was introduced, and the DPLL equation was solved using a digital computer. The spike model was successful in finding a second order DPLL which yielded a five db threshold extension beyond that of a first order DPLL.

  16. Magnetoresistance and Anti-Ferromagnetic Coupling in FM-Graphene-FM Trilayers

    Science.gov (United States)

    Cobas, Enrique D.; van't Erve, Olaf M. J.; Cheng, Shu-Fan; Jonker, Berend T.

    Both high-magnetoresistance(MR) minority spin filtering and anti-ferromagnetic (AFM) coupling have been predicted for FM|Graphene|FM vertical heterostructures. Our previous experiments demonstrated ordinary magnetoresistance in NiFe-Graphene-Co heterostructures and no evident AFM coupling. Here we present experimental results that confirm both MR minority spin filtering and AFM coupling in high-quality FM|Graphene|FM heterostructures. The heterostructures were fabricated by a combination of sputtering, chemical vapor deposition and electron beam evaporation. The stack was patterned into symmetric cross-bar structures using Ar ion milling. Measurements show negative magnetoresistance in excess of 10 percent, confirming spin-filtering, and weak anti-ferromagnetic coupling throughout the temperature range 15K to 300K. The temperature dependence of the MR was studied and found consistent with thermal excitation of spin waves in the ferromagnetic electrodes. Junction resistance-area products are in the range of 10 Ωcm2. These heterostructures provide a fast and low-power magnetic field sensor in the sub-100 Oe range and are a step towards high-MR low RA-product MRAM junctions.

  17. The Use of Polysymptomatic Distress Categories in the Evaluation of Fibromyalgia (FM) and FM Severity

    NARCIS (Netherlands)

    Wolfe, Frederick; Walitt, Brian T.; Rasker, Hans; Katz, Robert S.; Häuser, Winfried

    2015-01-01

    Objective The polysymptomatic distress (PSD) scale is derived from variables used in the 2010 American College of Rheumatology (ACR) fibromyalgia (FM) criteria modified for survey and clinical research. The scale is useful in measuring the effect of PSD over the full range of pain-related clinical s

  18. The Use of Polysymptomatic Distress Categories in the Evaluation of Fibromyalgia (FM) and FM Severity

    NARCIS (Netherlands)

    Wolfe, Frederick; Walitt, Brian T.; Rasker, Hans J.; Katz, Robert S.; Häuser, Winfried

    2015-01-01

    Objective The polysymptomatic distress (PSD) scale is derived from variables used in the 2010 American College of Rheumatology (ACR) fibromyalgia (FM) criteria modified for survey and clinical research. The scale is useful in measuring the effect of PSD over the full range of pain-related clinical

  19. Study Pulse Parameters versus Cavity Length for Both Dispersion Regimes in FM Mode Locked

    Directory of Open Access Journals (Sweden)

    Bushra Razooky Mhdi

    2015-03-01

    Full Text Available To demonstrate the effect of changing cavity length for  FM mode locked on pulse parameters and make comparison for both dispersion regime , a plot for each pulse parameter as Lr function are presented for normal and anomalous dispersion regimes. The analysis is based on the theoretical study and the results of numerical simulation using MATLAB. The effect of both normal and anomalous dispersion regimes on output pulses is investigate Fiber length effects on pulse parameters are investigated by driving the modulator into different values. A numerical solution for model equations using fourth-fifth order, Runge-Kutta method is performed through MATLAB 7.0 program. Fiber length effect on pulse parameters is investigated by driving the modulator into different values of lengths. Result shows that, the output pulse width from the FM mode locked equals to τ= 501ns anomalous regime and τ=518ns in normal regime.

  20. Modulation of Frequency Doubled DFB-Tapered Diode Lasers for Medical Treatment

    DEFF Research Database (Denmark)

    Christensen, Mathias; Hansen, Anders Kragh; Noordegraaf, Danny

    2017-01-01

    The use of visible lasers for medical treatments is on the rise, and together with this comes higher expectations for the laser systems. For many medical treatments, such as ophthalmology, doctors require pulse on demand operation together with a complete extinction of the light between pulses. We...... have demonstrated power modulation from 0.1 Hz to 10 kHz at 532 nm with a modulation depth above 97% by wavelength detuning of the laser diode. The laser diode is a 1064 nm monolithic device with a distributed feedback (DFB) laser as the master oscillator (MO), and a tapered power amplifier (PA...

  1. Photonic Implementation of 4-QAM/QPSK Electrical Modulation at Millimeter-Wave Frequency

    DEFF Research Database (Denmark)

    Yu, Xianbin; Jensen, Jesper Bevensee; Tafur Monroy, Idelfonso

    2008-01-01

    We propose a photonic method for generating millimeter-wave 4-QAM/QPSK modulated signals. The method is based on optical phase modulation by multilevel electrical signals and optical carrier-suppression. Simulation results are presented for 2.5 Gsymbol/s 4-QAM and QPSK signals at a 36 GHz carrier....... Furthermore, this method can be extended to generate millimeter-wave m-PSK signals and can be incorporated into broadband radio-over-fiber systems to support wireless/ wireline converged access network....

  2. Effect of modulated ultrahigh frequency field on behavior and hormone level in female rats under emotional stress

    Energy Technology Data Exchange (ETDEWEB)

    Rasulov, M.M.

    The effect of a modulated electromagnetic field (MEMF) (field frequency of 40 MHz and modulated frequency of 50 Hz, 1 h exposure daily for 30 days) on behavior and level of sexual hormones, determined from the length of the estrous cycle and of its separate phases, was studied in female Wistar rats subjected to sexual deprivation. The ratio of frequency of running to number of vertical positions (R:V) was used as an index. Activity of rats declined during the 1-h exposure to MEMF; this may indicate the direct effect of MEMF on the central nervous system. Analysis of behavior after MEMF treatments ceased showed that the R:V ratio increased from 3.2:1 to 3:1 in month 3 and reached 2:1 in month 5. The relative significance of sexual behavior (lordosis, licking of perineum) more than double in comparison with the initial level. The findings support the existence of individual differences in sensitivity to a UHF field. The data on the estrous cycle indicate the tranquilizing effect of a UHF field on the neuroendocrine system and the greater resistance of individual animals exposed to MEMF to the development of sexual neurosis. 12 references, 2 figures.

  3. Dual-function photonic integrated circuit for frequency octo-tupling or single-side-band modulation.

    Science.gov (United States)

    Hasan, Mehedi; Maldonado-Basilio, Ramón; Hall, Trevor J

    2015-06-01

    A dual-function photonic integrated circuit for microwave photonic applications is proposed. The circuit consists of four linear electro-optic phase modulators connected optically in parallel within a generalized Mach-Zehnder interferometer architecture. The photonic circuit is arranged to have two separate output ports. A first port provides frequency up-conversion of a microwave signal from the electrical to the optical domain; equivalently single-side-band modulation. A second port provides tunable millimeter wave carriers by frequency octo-tupling of an appropriate amplitude RF carrier. The circuit exploits the intrinsic relative phases between the ports of multi-mode interference couplers to provide substantially all the static optical phases needed. The operation of the proposed dual-function photonic integrated circuit is verified by computer simulations. The performance of the frequency octo-tupling and up-conversion functions is analyzed in terms of the electrical signal to harmonic distortion ratio and the optical single side band to unwanted harmonics ratio, respectively.

  4. Generation of high-frequency combs locked to atomic resonances by quantum phase modulation

    CERN Document Server

    Liu, Zuoye; Cavaletto, Stefano M; Harman, Zoltán; Keitel, Christoph H; Pfeifer, Thomas

    2013-01-01

    A general mechanism for the generation of frequency combs referenced to atomic resonances is put forward. The mechanism is based on the periodic phase control of a quantum system's dipole response. We develop an analytic description of the comb spectral structure, depending on both the atomic and the phase-control properties. We further suggest an experimental implementation of our scheme: Generating a frequency comb in the soft-x-ray spectral region, which can be realized with currently available techniques and radiation sources. The universality of this mechanism allows the generalization of frequency-comb technology to arbitrary frequencies, including the hard-x-ray regime by using reference transitions in highly charged ions.

  5. Frequency-modulated excitation of Rydberg potassium atoms by using B-spline

    Institute of Scientific and Technical Information of China (English)

    Li Xiao-Yong; Wang Guo-Li; Zhou Xiao-Xin

    2012-01-01

    By using the B-spline expansion technique and a model potential of the alkali atoms,the properties of frequencymodulated excitation of Rydberg potassium atoms in a static electric field and a microwave field are investigated by using the time-dependent two-level approach.We successfully reproduce the square wave oscillations in the low frequency,the stair step population oscillations in the intermediate frequency,and the multiphoton transitions in the high frequency with respect to the unmodulated Rabi frequency,which have been observed experimentally by Noel et al.[Phys.Rev.A 58 2265 (1998)].Furthermore,we also numerically obtain the discretized Rabi oscillations predicted in the Landau-Zener accumulation model.

  6. Frequency-domain equalization for OFDMA-based multiuser MIMO systems with improper modulation schemes

    Directory of Open Access Journals (Sweden)

    Wu Yi

    2011-01-01

    Full Text Available Abstract In this paper, we propose a novel transceiver structure for orthogonal frequency division multiple access-based uplink multiuser multiple-input multiple-output systems. The numerical results show that the proposed frequency-domain equalization schemes significantly outperform conventional linear minimum mean square error-based equalizers in terms of bit error rate performance with moderate increase in computational complexity.

  7. Adaptive Multicarrier Modulation: A Convenient Framework for Time-Frequency Processing in Wireless Communications

    OpenAIRE

    Keller, T.; Hanzo, L.

    2000-01-01

    A historical perspective of orthogonal frequency-division multiplexing (OFDM) is given with reference to its literature. Its advantages and disadvantages are reviewed, and its performance is characterized over highly dispersive channels. The effects of both time- and frequency-domain synchronization errors are quantified, and a range of solutions proposed in the recent literature are re-viewed. One of the main objectives of this review is to highlight the recent thinking behind adaptive bit a...

  8. Coherent cooling of atoms in a frequency-modulated standing laser wave: wave function and stochastic trajectory approaches

    CERN Document Server

    Argonov, Victor

    2013-01-01

    The wave function of a moderately cold atom in a stationary near-resonant standing light wave delocalizes very fast due to wave packet splitting. However, we show that frequency modulation of the field may suppress packet splitting for some atoms having specific velocities in a narrow range. These atoms remain localized in a small space for a long time. We demonstrate and explain this effect numerically and analytically. Also we demonstrate that modulated field can not only trap, but also cool the atoms. We perform a numerical experiment with a large atomic ensebmble having wide initial velocity and energy distribution. During the experiment, most of atoms leave the wave while trapped atoms have narrow energy distribution

  9. Dayside magnetospheric ULF wave frequency modulated by a solar wind dynamic pressure negative impulse

    Science.gov (United States)

    Shen, X. C.; Shi, Q. Q.; Zong, Q.-G.; Tian, A. M.; Nowada, M.; Sun, W. J.; Zhao, H. Y.; Hudson, M. K.; Wang, H. Z.; Fu, S. Y.; Pu, Z. Y.

    2017-02-01

    Ultralow frequency (ULF) waves play an important role in the transport of the solar wind energy to the magnetosphere. In this paper, we present a ULF wave event in the dayside magnetosphere which shows a sudden decrease in frequency from 3.1 to 2.3 mHz around 0756 UT on 11 January 2010, when a solar wind dynamic pressure drop (from ˜5 to ˜2 nPa) was observed simultaneously. The wave exits globally. The phase differences between electric and magnetic fields indicate that the compressional mode wave is standing before and after the wave frequency decrease. This result suggests that the ULF wave should be associated with a cavity mode and the frequency decrease might be induced by the change of the cavity size. A theoretical calculation was made to estimate the cavity mode frequency. The calculated wave frequency before/after the negative impulse is 3.8/2.6 mHz, which is consistent with the observations.

  10. Quantitative imaging of nanometric optical path length modulations by time-averaged heterodyne holography in coherent frequency-division multiplexing regime

    CERN Document Server

    Bruno, Francois; Lesaffre, Max; Verrier, Nicolas; Atlan, Michael

    2013-01-01

    We report a demonstration of amplitude and phase imaging of out-of-plane sinusoidal vibration at nanometer scales with a heterodyne holographic interferometer. Time-averaged holograms of a phase-modulated optical field are recorded with an exposure time much longer than the modulation period. Optical heterodyning, a frequency-conversion process aimed at shifting a given radiofrequency optical side band in the sensor bandwidth, is performed with an off-axis and frequency-shifted optical local oscillator. The originality of the proposed method is to make use of a multiplexed local oscillator to address several optical side bands into the temporal bandwidth of the sensor array. This process is called coherent frequency-division multiplexing. It enables simultaneous recording and pixel-to-pixel division of two side band holograms, which permits quantitative mapping of the modulation depth of local optical path lengths yielding small optical phase modulations. Additionally, a linear frequency chirp ensures the ret...

  11. A Broadband, Spectrally Flat, High Rep-rate Frequency Comb: Bandwidth Scaling and Flatness Enhancement of Phase Modulated CW through Cascaded Four-Wave Mixing

    CERN Document Server

    Supradeepa, V R

    2010-01-01

    We demonstrate a scheme to scale the bandwidth by several times while enhancing spectral flatness of frequency combs generated by intensity and phase modulation of CW lasers using cascaded four-wave mixing in highly nonlinear fiber.

  12. A bulk-controlled ring-VCO with 1/f-noise reduction for frequency ΔΣ modulator

    DEFF Research Database (Denmark)

    Tuan Vu, CAO; Wisland, Dag T.; Lande, Tor Sverre

    The paper introduces a bulk-controlled ring-VCO with a tail transistor utilizing flicker-noise (1/f-noise) reduction techniques for a frequency-based DeltaSigma modulator (FDSM). This VCO converts an analog input voltage to phase information under various bias conditions ranging from sub......-threshold to saturation. By using the 1/f-noise reduction circuit which is based on the switched bias technique, the simulations indicate that less noise is transferred to the output when the 1/f-noise reduction circuit is used. The phase noise of the proposed VCO is improved by 7.6% while maintaining tuning...

  13. Analysis of chaotic FM system synchronization for bistatic radar

    Science.gov (United States)

    Pappu, Chandra S.; Verdin, Berenice; Flores, Benjamin C.; Boehm, James; Debroux, Patrick

    2015-05-01

    We propose a scheme for bistatic radar that uses a chaotic system to generate a wideband FM signal that is reconstructed at the receiver via a conventional phase lock loop. The setup for the bistatic radar includes a 3 state variable drive oscillator at the transmitter and a response oscillator at the receiver. The challenge is in synchronizing the response oscillator of the radar receiver utilizing a scaled version of the transmitted signal sr(t, x) = αst(t, x) where x is one of three driver oscillator state variables and α is the scaling factor that accounts for antenna gain, system losses, and space propagation. For FM, we also assume that the instantaneous frequency of the received signal, xs, is a scaled version of the Lorenz variable x. Since this additional scaling factor may not be known a priori, the response oscillator must be able to accept the scaled version of x as an input. Thus, to achieve synchronization we utilize a generalized projective synchronization technique that introduces a controller term -μe where μ is a control factor and e is the difference between the response state variable xs and a scaled x. Since demodulation of sr(t) is required to reconstruct the chaotic state variable x, the phase lock loop imposes a limit on the minimum error e. We verify through simulations that, once synchronization is achieved, the short-time correlation of x and xs is high and that the self-noise in the correlation is negligible over long periods of time.

  14. Frequency modulated few-cycle optical pulse trains induced controllable ultrafast coherent population oscillations in three-level atomic systems

    CERN Document Server

    Kumar, Parvendra

    2012-01-01

    We report a study on the ultrafast coherent population oscillations (UCPO) in sodium atoms induced by the frequency modulated few-cycle optical pulse trains. The phenomenon of UCPO is investigated by numerically solving the appropriate density matrix equations beyond the rotating wave approximation. We demonstrate that the quantum state of the atoms and the frequency of UCPO may be controlled by controlling the number of pulses in the pulse trains and the pulse repetition time respectively. Moreover, the robustness of population transfer against the variation of laser pulse parameters is also investigated. The proposed scheme may be useful for the creation of atomic beam in selected quantum state for desired time duration and may have potential applications in ultrafast optical switching.

  15. High-frequency oscillation in the hippocampus of the behaving rat and its modulation by the histaminergic system.

    Science.gov (United States)

    Knoche, A; Yokoyama, H; Ponomarenko, A; Frisch, C; Huston, J; Haas, H L

    2003-01-01

    The histaminergic neurons located in the posterior hypothalamus modulate whole brain activity in a manner dependent on behavioral state. We have investigated their influence on high-frequency oscillation (200-Hz ripples) in the hippocampal CA1 region of freely moving rats. The occurrence of these ripples, assumed to be involved in memory trace formation, was markedly enhanced after injection of the H1-antagonists pyrilamine and ketotifen in a lateral ventricle, indicating a tonic activity of the histaminergic system. The H2- and H3-antagonists cimetidine and thioperamide were ineffective. We suggest a mediation of these effects through blocking the known histaminergic excitation of septal neurons. Histamine administered by the intracerebroventricular route had an inhibitory action on ripples. H1-receptor activation, which has been shown to inhibit learning and memory, thus shifts hippocampal activity away from high-frequency oscillation toward theta activity.

  16. Synchronization by the hand: The sight of gestures modulates low-frequency activity in brain responses to continuous speech

    Directory of Open Access Journals (Sweden)

    Emmanuel eBiau

    2015-09-01

    Full Text Available During social interactions, speakers often produce spontaneous gestures to accompany their speech. These coordinated body movements convey communicative intentions, and modulate how listeners perceive the message in a subtle, but important way. In the present perspective, we put the focus on the role that congruent non-verbal information from beat gestures may play in the neural responses to speech. Whilst delta-theta oscillatory brain responses reflect the time-frequency structure of the speech signal, we argue that beat gestures promote phase resetting at relevant word onsets. This mechanism may facilitate the anticipation of associated acoustic cues relevant for prosodic/syllabic-based segmentation in speech perception. We report recently published data supporting this hypothesis, and discuss the potential of beats (and gestures in general for further studies investigating continuous AV speech processing through low-frequency oscillations.

  17. Superfluid dynamics of 258Fm fission

    CERN Document Server

    Scamps, Guillaume; Lacroix, Denis

    2015-01-01

    Theoretical description of nuclear fission remains one of the major challenges of quantum many-body dynamics. The slow, mostly adiabatic motion through the fission barrier is followed by a fast, non-adiabatic descent of the potential between the fragments. The latter stage is essentially unexplored. However, it is crucial as it generates most of the excitation energy in the fragments. The superfluid dynamics in the latter stage of fission is obtained with the time-dependent Hartree-Fock theory including BCS dynamical pairing correlations. The fission modes of the 258Fm nucleus are studied. The resulting fission fragment characteristics show a good agreement with experimental data. Quantum shell effects are shown to play a crucial role in the dynamics and formation of the fragments. The importance of quantum fluctuations beyond the independent particle/quasi-particle picture is underlined and qualitatively studied.

  18. The frequency of hippocampal theta rhythm is modulated on a circadian period and is entrained by food availability.

    Directory of Open Access Journals (Sweden)

    Robert Gordon Keith Munn

    2015-03-01

    Full Text Available The hippocampal formation plays a critical role in the generation of episodic memory. While the encoding of the spatial and contextual components of memory have been extensively studied, how the hippocampus encodes temporal information, especially at long time intervals, is less well understood. The activity of place cells in hippocampus has previously been shown to be modulated at a circadian time-scale, entrained by a behavioral stimulus, but not entrained by light. The experimental procedures used in the previous study of this phenomenon, however, necessarily conflated two alternative entraining stimuli, the exposure to the recording environment and the availability of food, making it impossible to distinguish between these possibilities. Here we demonstrate that the frequency of theta-band hippocampal EEG varies with a circadian period in freely moving animals and that this periodicity mirrors changes in the firing rate of hippocampal neurons. Theta activity serves, therefore, as a proxy of circadian-modulated hippocampal neuronal activity. We then demonstrate that the frequency of hippocampal theta driven by stimulation of the reticular formation also varies with a circadian period. Because this effect can be observed without having to feed the animal to encourage movement we were able to identify what stimulus entrains the circadian oscillation. We show that with reticular-activated recordings started at various times of the day the frequency of theta varies quasi-sinusoidally with a 25 hour period and phase-aligned when referenced to the animal’s regular feeding time, but not the recording start time. Furthermore, we show that theta frequency consistently varied with a circadian period when the data obtained from repeated recordings started at various times of the day were referenced to the start of food availability in the recording chamber. This pattern did not occur when data were referenced to the start of the recording session or

  19. 47 CFR 74.1202 - Frequency assignment.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency assignment. 74.1202 Section 74.1202 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES EXPERIMENTAL RADIO... FM Broadcast Booster Stations § 74.1202 Frequency assignment. (a) An applicant for a new FM broadcast...

  20. 47 CFR 74.1261 - Frequency tolerance.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency tolerance. 74.1261 Section 74.1261 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES EXPERIMENTAL RADIO... FM Broadcast Booster Stations § 74.1261 Frequency tolerance. (a) The licensee of an FM translator...

  1. Frequency Selective Filtering of the Modulation Spectrum and its Impact on Consonant Identification

    DEFF Research Database (Denmark)

    Christiansen, Thomas Ulrich; Greenberg, Steven

    2005-01-01

    other. The modulation spectrum of each band was low-pass filtered at 24, 12, 6 and 3 Hz. Confusion matrices of the consonant-identification data were computed, and from these the amount of information transmitted for each of three phonetic feature dimensions – voicing, manner and place of articulation...... – was calculated for each condition. This form of analysis provides a simple means of determining whether information associated with each phonetic feature dimension combines linearly across the audio spectrum, and, if not, delineates a method for characterizing the (non-linear) nature of information integration....... In addition, the analysis provides a means to associate specific portions of the modulation spectrum with phonetic feature properties. Such analyses indicate that: (1) Accurate, robust decoding of place-of-articulation information requires broadband cross-spectral integration (2) Place...

  2. Resarch on the Future of FM in the Nordic Countries

    DEFF Research Database (Denmark)

    Jensen, Per Anker; Rasmussen, Birgitte; Andersen, Per Dannemand

    2012-01-01

    that the strategy reflects future needs and expectations among Nordic researchers and practitioners within the FM field. The foresight process included four elements: The first element was a preliminary survey of existing studies and foresight projects on the future for FM. In particular the survey included...... in the FM sector. As a third element the preliminary results of the foresight project were presented and discussed at a Nordic workshop as part of a Nordic FM conference arranged by CFM at DTU in August 2011. The fourth element was a Nordic Delphi-like questionnaire with the aim of identifying and ranking...

  3. Shaping frequency correlations of ultrafast pulse-pumped modulational instability in gas-filled hollow-core PCF

    CERN Document Server

    Finger, Martin A; Russell, Philip St J; Chekhova, Maria V

    2016-01-01

    We vary the time-frequency mode structure of ultrafast pulse-pumped modulational instability (MI) in an argon-filled hollow-core kagom\\'e-style PCF by adjusting the pressure, pump pulse chirp, fiber length and parametric gain. Compared to solid-core systems, the pressure dependent dispersion landscape brings increased flexibility to the tailoring of frequency correlations. The resulting mode content is characterized by measuring the multimode second-order correlation function g(2) and by directly observing frequency correlations in single-shot MI spectra. We show that, from such measurements, the shapes and weights of time-frequency Schmidt (TFS) modes can be extracted and that the number of modes directly influences the shot-to-shot pulse-energy and spectral-shape fluctuations in MI. Using this approach we are able to change the number of TFS modes from 1.3 (g(2) = 1.75) to 4 (g(2) = 1.25) using only a single fiber.

  4. Combined frequency modulated atomic force microscopy and scanning tunneling microscopy detection for multi-tip scanning probe microscopy applications

    Science.gov (United States)

    Morawski, Ireneusz; Spiegelberg, Richard; Korte, Stefan; Voigtländer, Bert

    2015-12-01

    A method which allows scanning tunneling microscopy (STM) tip biasing independent of the sample bias during frequency modulated atomic force microscopy (AFM) operation is presented. The AFM sensor is supplied by an electronic circuit combining both a frequency shift signal and a tunneling current signal by means of an inductive coupling. This solution enables a control of the tip potential independent of the sample potential. Individual tip biasing is specifically important in order to implement multi-tip STM/AFM applications. An extensional quartz sensor (needle sensor) with a conductive tip is applied to record simultaneously topography and conductivity of the sample. The high resonance frequency of the needle sensor (1 MHz) allows scanning of a large area of the surface being investigated in a reasonably short time. A recipe for the amplitude calibration which is based only on the frequency shift signal and does not require the tip being in contact is presented. Additionally, we show spectral measurements of the mechanical vibration noise of the scanning system used in the investigations.

  5. Ultralow-phase-noise millimetre-wave signal generator assisted with an electro-optics-modulator-based optical frequency comb.

    Science.gov (United States)

    Ishizawa, A; Nishikawa, T; Goto, T; Hitachi, K; Sogawa, T; Gotoh, H

    2016-05-17

    Low-noise millimetre-wave signals are valuable for digital sampling systems, arbitrary waveform generation for ultra-wideband communications, and coherent radar systems. However, the phase noise of widely used conventional signal generators (SGs) will increase as the millimetre-wave frequency increases. Our goal has been to improve commercially available SGs so that they provide a low-phase-noise millimetre-wave signal with assistance from an electro-optics-modulator-based optical frequency comb (EOM-OFC). Here, we show that the phase noise can be greatly reduced by bridging the vast frequency difference between the gigahertz and terahertz ranges with an EOM-OFC. The EOM-OFC serves as a liaison that magnifies the phase noise of the SG. With the EOM-OFC used as a phase noise "booster" for a millimetre-wave signal, the phase noise of widely used SGs can be reduced at an arbitrary frequency f (6 ≦ f ≦ 72 GHz).

  6. Low-level contrast statistics of natural images can modulate the frequency of event-related potentials (ERP in humans

    Directory of Open Access Journals (Sweden)

    Masoud Ghodrati

    2016-12-01

    Full Text Available Humans are fast and accurate in categorizing complex natural images. It is, however, unclear what features of visual information are exploited by brain to perceive the images with such speed and accuracy. It has been shown that low-level contrast statistics of natural scenes can explain the variance of amplitude of event-related potentials (ERP in response to rapidly presented images. In this study, we investigated the effect of these statistics on frequency content of ERPs. We recorded ERPs from human subjects, while they viewed natural images each presented for 70 ms. Our results showed that Weibull contrast statistics, as a biologically plausible model, explained the variance of ERPs the best, compared to other image statistics that we assessed. Our time-frequency analysis revealed a significant correlation between these statistics and ERPs’ power within theta frequency band (~3-7 Hz. This is interesting, as theta band is believed to be involved in context updating and semantic encoding. This correlation became significant at ~110 ms after stimulus onset, and peaked at 138 ms. Our results show that not only the amplitude but also the frequency of neural responses can be modulated with low-level contrast statistics of natural images and highlights their potential role in scene perception.

  7. Modulation of epileptic activity by deep brain stimulation: a model-based study of frequency-dependent effects

    Directory of Open Access Journals (Sweden)

    Faten eMina

    2013-07-01

    Full Text Available A number of studies showed that deep brain stimulation (DBS can modulate the activity in the epileptic brain and that a decrease of seizures can be achieved in responding patients. In most of these studies, the choice of stimulation parameters is critical to obtain desired clinical effects. In particular, the stimulation frequency is a key parameter that is difficult to tune. A reason is that our knowledge about the frequency-dependant mechanisms according to which DBS indirectly impacts the dynamics of pathological neuronal systems located in the neocortex is still limited. We address this issue using both computational modeling and intracerebral EEG (iEEG data.We developed a macroscopic (neural mass model of the thalamocortical network. In line with already-existing models, it includes interconnected neocortical pyramidal cells and interneurons, thalamocortical cells and reticular neurons. The novelty was to introduce, in the thalamic compartment, the biophysical effects of direct stimulation. Regarding clinical data, we used a quite unique data set recorded in a patient (drug-resistant epilepsy with a focal cortical dysplasia (FCD. In this patient, DBS strongly reduced the sustained epileptic activity of the FCD for low-frequency (LFS, < 2 Hz and high-frequency stimulation (HFS, > 70 Hz while intermediate-frequency stimulation (IFS, around 50 Hz had no effect.Signal processing, clustering and optimization techniques allowed us to identify the necessary conditions for reproducing, in the model, the observed frequency-dependent stimulation effects. Key elements which explain the suppression of epileptic activity in the FCD include a feed-forward inhibition and synaptic short-term depression of thalamocortical connections at LFS, and b inhibition of the thalamic output at HFS. Conversely, modeling results indicate that IFS favors thalamic oscillations and entrains epileptic dynamics.

  8. ERP correlates of letter identity and letter position are modulated by lexical frequency

    Science.gov (United States)

    Vergara-Martínez, Marta; Perea, Manuel; Gómez, Pablo; Swaab, Tamara Y.

    2013-01-01

    The encoding of letter position is a key aspect in all recently proposed models of visual-word recognition. We analyzed the impact of lexical frequency on letter position assignment by examining the temporal dynamics of lexical activation induced by pseudowords extracted from words of different frequencies. For each word (e.g., BRIDGE), we created two pseudowords: A transposed-letter (TL: BRIGDE) and a replaced-letter pseudoword (RL: BRITGE). ERPs were recorded while participants read words and pseudowords in two tasks: Semantic categorization (Experiment 1) and lexical decision (Experiment 2). For high-frequency stimuli, similar ERPs were obtained for words and TL-pseudowords, but the N400 component to words was reduced relative to RL-pseudowords, indicating less lexical/semantic activation. In contrast, TL- and RL-pseudowords created from low-frequency stimuli elicited similar ERPs. Behavioral responses in the lexical decision task paralleled this asymmetry. The present findings impose constraints on computational and neural models of visual-word recognition. PMID:23454070

  9. Frequency Selective Filtering of the Modulation Spectrum and its Impact on Consonant Identification

    DEFF Research Database (Denmark)

    Christiansen, Thomas Ulrich; Greenberg, Steven

    2009-01-01

    ] refers to the syllable-final liquid segment). Each syllable was processed so that only a portion of the original audio spectrum was present. Narrow (three-quarter octave) bands of speech, with center frequencies of 750 Hz, 1500 Hz and 3000 Hz, were presented individually and in combination with each...

  10. Logic and control module for the Fermilab booster beam damper

    Energy Technology Data Exchange (ETDEWEB)

    Sandberg, B.R.

    1977-01-01

    A logic and control module is included in the electronic system of the booster superdamper. This module produces a 9-bit digital word that controls the delay of beam bunch position information in the Fermilab booster synchrotron so that it arrives at the damping electrodes at the same time as the bunch of beam to be corrected. This delay word generator also has an output feature that only allows delay time decreases as the booster synchrotron frequency program increases monotonically. Such a feature guards against low-index incidental FM from affecting the delay computations.

  11. FM Stereo Radio Based on AVR MCU%AVR单片机的调频立体声收音机设计

    Institute of Scientific and Technical Information of China (English)

    何乃味

    2014-01-01

    This article describes a kind of FM radio which its controlling core is a low-power microcontroller ATmega8L and the MCU’s receiver is RDA5807P chip .The radio can read and write RDA5807P radio module through the I2 C data interface of by the microcon-troller ATmega8L .The radio can conduct search,volume control and other operations with buttons ,LCD displays the frequency receiv-er channels and the current volume size and other information.The design are gives the realization FM radio hardware circuit,the read/write RDA5807P radio module and an infrared remote control decoding program ideas.After several comparison tests,the results show that the radio can be listened to all the FM radio that provincial and local emission clearly and stably.%介绍一种以低功耗单片机 ATmega8L为控制核心,以 RDA5807P芯片作为 FM接收器的调频收音机。该收音机通过单片机 ATmega8L的 I2 C总线接口读写 RDA5807P 收音模块的数据,用按键及红外遥控器进行搜台、音量调节等操作。用 LCD显示接收频道的频率,当前音量大小等信息。设计中给出了实现 FM 调频收音机的硬件电路、读/写RDA5807 P收音模块及红外遥控解码程序的思路。经多次比对测试,该收音机可以清晰、稳定地收听省府及本地发射的所有调频电台。

  12. Modulation of the Left Prefrontal Cortex with High Frequency Repetitive Transcranial Magnetic Stimulation Facilitates Gait in Multiple Sclerosis

    Directory of Open Access Journals (Sweden)

    Amer M. Burhan

    2015-01-01

    Full Text Available Multiple Sclerosis (MS is a chronic central nervous system (CNS demyelinating disease. Gait abnormalities are common and disabling in patients with MS with limited treatment options available. Emerging evidence suggests a role of prefrontal attention networks in modulating gait. High-frequency repetitive transcranial magnetic stimulation (rTMS is known to enhance cortical excitability in stimulated cortex and its correlates. We investigated the effect of high-frequency left prefrontal rTMS on gait parameters in a 51-year-old Caucasian male with chronic relapsing/remitting MS with residual disabling attention and gait symptoms. Patient received 6 Hz, rTMS at 90% motor threshold using figure of eight coil centered on F3 location (using 10-20 electroencephalography (EEG lead localization system. GAITRite gait analysis system was used to collect objective gait measures before and after one session and in another occasion three consecutive daily sessions of rTMS. Two-tailed within subject repeated measure t-test showed significant enhancement in ambulation time, gait velocity, and cadence after three consecutive daily sessions of rTMS. Modulating left prefrontal cortex excitability using rTMS resulted in significant change in gait parameters after three sessions. To our knowledge, this is the first report that demonstrates the effect of rTMS applied to the prefrontal cortex on gait in MS patients.

  13. Implementation of the frequency-modulated sideband search method for gravitational waves from low mass X-ray binaries

    CERN Document Server

    Sammut, Letizia; Melatos, Andrew; Owen, Benjamin J

    2013-01-01

    We describe the practical implementation of the sideband search, a search for periodic gravitational waves from neutron stars in binary systems. The orbital motion of the source in its binary system causes frequency-modulation in the combination of matched filters known as the $\\mathcal{F}$-statistic. The sideband search is based on the incoherent summation of these frequency-modulated $\\mathcal{F}$-statistic sidebands. It provides a new detection statistic for sources in binary systems, called the $\\mathcal{C}$-statistic. The search is well suited to low-mass X-ray binaries, the brightest of which, called Sco X-1, is an ideal target candidate. For sources like Sco X-1, with well constrained orbital parameters, a slight variation on the search is possible. The extra orbital information can be used to approximately demodulate the data from the binary orbital motion in the coherent stage, before incoherently summing the now reduced number of sidebands. We investigate this approach and show that it improves the ...

  14. Use of modulated excitation signals in ultrasound. Part I: Basic concepts and expected benefits

    DEFF Research Database (Denmark)

    Misaridis, Thanassis; Jensen, Jørgen Arendt

    2005-01-01

    This paper, the first from a series of three papers on the application of coded excitation signals in medical ultrasound, discusses the basic principles and ultrasound-related problems of pulse compression. The concepts of signal modulation and matched filtering are given, and a simple model...... of attenuation relates the matched filter response with the ambiguity function, known from radar. Based on this analysis and the properties of the ambiguity function, the selection of coded waveforms suitable for ultrasound imaging is discussed. It is shown that linear frequency modulation (FM) signals have...... the best and most robust features for ultrasound imaging. Other coded signals such as nonlinear FM and binary complementary Golay codes also have been considered and characterized in terms of signal-to-noise ratio (SNR) and sensitivity to frequency shifts. Using the simulation program Field II, it is found...

  15. Periodic density modulation for quasi-phase-matching of optical frequency conversion is inefficient under shallow focusing and constant ambient pressure.

    Science.gov (United States)

    Hadas, Itai; Bahabad, Alon

    2016-09-01

    The two main mechanisms of a periodic density modulation relevant to nonlinear optical conversion in a gas medium are spatial modulations of the index of refraction and of the number of emitters. For a one-dimensional model neglecting focusing and using a constant ambient pressure, it is shown theoretically and demonstrated numerically that the effects of these two mechanisms during frequency conversion cancel each other exactly. Under the considered conditions, this makes density modulation inefficient for quasi-phase-matching an optical frequency conversion process. This result is particularly relevant for high-order harmonic generation.

  16. Fundamental-Frequency-Modulated Six-Level Diode-Clamped Multilevel Inverter for Three-Phase Stand-Alone Photovoltaic System

    Energy Technology Data Exchange (ETDEWEB)

    Ozdemir, Engin [ORNL; Ozdemir, Sule [Oak Ridge National Laboratory (ORNL); Tolbert, Leon M [ORNL

    2009-01-01

    This paper presents a fundamental-frequency-modulated diode-clamped multilevel inverter (DCMLI) scheme for a three-phase stand-alone photovoltaic (PV) system. The system consists of five series-connected PV modules, a six-level DCMLI generating fundamental-modulation staircase three-phase output voltages, and a three-phase induction motor as the load. In order to validate the proposed concept, simulation studies and experimental measurements using a small-scale laboratory prototype are also presented. The results show the feasibility of the fundamental frequency switching application in three-phase stand-alone PV power systems.

  17. Spectrum of the nonstationary electromyographic signal modelled with integral pulse frequency modulation and its application to estimating neural drive information.

    Science.gov (United States)

    Jiang, Ning; Parker, Philip A; Englehart, Kevin B

    2009-08-01

    The spectrum of nonstationary electromyographic signal (EMG) is investigated, from which the error for neural drive information estimation from nonstationary EMG is studied in terms of signal-to-noise ratio (SNR), in analytical, numerical simulation, and experimental work. The signal refers to the neural drive information embedded within the nonstationary EMG, and noise refers to other portions of EMG that induce error in the estimation. The analytical expressions for the SNRs of force-modulated EMG with both single and multiple motor units (MU) are derived based on a sinusoidal integral pulse frequency modulation (IPFM) model. It is shown that the previously developed SNR expressions for stationary (unmodulated) EMG are special cases of the formulas presented here. The SNR results obtained from numerical simulated EMG agree very well with the analytical result. Results from nonstationary (modulated) surface EMG obtained from seven subjects also match the analytical and simulation results reasonably well. The results obtained from this work establish an analytical framework in studying and estimating the neural drive information contained in the EMG in the context of anisotonic and isometric contractions. Through the analytical study, the effects of different physiological parameters are identified, thus providing theoretical guidelines for developing advanced signal processing methods for nonstationary EMG in applications such as prosthesis control.

  18. Electrodynamic Processes in Solar Magnetic Loops and their Relation to the Low-Frequency Modulations of Solar Microwave Emissions

    Science.gov (United States)

    Khodachenko, M. L.; Rucker, H. O.; Kislyakov, A. G.; Zaitsev, V. V.; Urpo, S.

    The spectral and temporal evolutions of the low-frequency (LF) pulsations modulating the solar microwave radiation (37 GHz) recorded at the Metsähovi Radio Observatory were studied by means of the data analysis algorithm based on a fast Fourier transformation with a sliding window. Attention is paid to the fact that the intensity of microwave radiation of solar flares, produced by the electron gyrosynchrotron mechanism, is dependent on a value of the background magnetic field (Dulk, 1985). Thus, slow variations of the magnetic field associated with disturbances of the electric current in a radiating source, should modulate the intensity of the microwave radiation. The dynamic spectra of the LF pulsations, quite often contain several spectral tracks, which can be interpreted as an indication that the radiation is produced in a system consisting of several closely located magnetic loops involved in a common global dynamical process. Application of the equivalent electric circuit models of the loops with inclusion of the effects of electromagnetic inductive interaction in groups of slowly growing current-carrying magnetic loops allows to explain and reproduce the main dynamical features of the observed LF modulation dynamic spectra. Detailed derivation of the equivalent electric circuit equation for a coronal magnetic loop is provided.

  19. Predicting speech intelligibility based on the signal-to-noise envelope power ratio after modulation-frequency selective processing.

    Science.gov (United States)

    Jørgensen, Søren; Dau, Torsten

    2011-09-01

    A model for predicting the intelligibility of processed noisy speech is proposed. The speech-based envelope power spectrum model has a similar structure as the model of Ewert and Dau [(2000). J. Acoust. Soc. Am. 108, 1181-1196], developed to account for modulation detection and masking data. The model estimates the speech-to-noise envelope power ratio, SNR(env), at the output of a modulation filterbank and relates this metric to speech intelligibility using the concept of an ideal observer. Predictions were compared to data on the intelligibility of speech presented in stationary speech-shaped noise. The model was further tested in conditions with noisy speech subjected to reverberation and spectral subtraction. Good agreement between predictions and data was found in all cases. For spectral subtraction, an analysis of the model's internal representation of the stimuli revealed that the predicted decrease of intelligibility was caused by the estimated noise envelope power exceeding that of the speech. The classical concept of the speech transmission index fails in this condition. The results strongly suggest that the signal-to-noise ratio at the output of a modulation frequency selective process provides a key measure of speech intelligibility.

  20. Effects of nonlinear phase modulation on quantum frequency conversion using four-wave mixing Bragg scattering

    DEFF Research Database (Denmark)

    Andersen, Lasse Mejling; McKinstrie, C. J.; Rottwitt, Karsten

    2013-01-01

    Recently, we solved the coupled-mode equations for Bragg scattering (BS) in the low- and high-conversion regimes, but without the effects of nonlinear phase modulation (NPM). We now present solutions and Green functions in the low-conversion regime that include NPM. We find that NPM does not change...... are still possible, even when the effects of NPM are included. Finally, the effects of using different input signals are considered, and we conclude that using the natural input modes of the system drastically increases the efficiency. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers...