DEMODULATION OF FREQUENCY OR SPACE MODULATED LIGHT.
LIGHT , DEMODULATION), (*OPTICAL COMMUNICATIONS, FREQUENCY MODULATION), (*FREQUENCY MODULATION, LIGHT ), OPTICAL TRACKING, BEAMS(ELECTROMAGNETIC), DEFLECTION, MICROWAVE FREQUENCY, ELECTRON BEAMS, PHOTOCATHODES
Wideband FM Demodulation and Multirate Frequency Transformations
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
Optimal space communications techniques. [all digital phase locked loop for FM demodulation
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.
Radio-frequency transparent demodulation for broadband hybrid wireless-optical links
DEFF Research Database (Denmark)
Zibar, Darko; Sambaraju, Rakesh; Alemany, Ruben
2010-01-01
A novel demodulation technique which is transparent to radio-frequency (RF) carrier frequency is presented and experimentally demonstrated for multigigabit wireless signals. The presented demodulation technique employs optical single-sideband filtering, coherent detection, and baseband digital si...
Demodulated low frequency currents from electrosurgical procedures.
Tucker, R D; Schmitt, O H; Sievert, C E; Silvis, S E
1984-07-01
Low frequency currents produced incidental to electrosurgical procedures are usually only a minor threat unless they are coupled directly into the heart through a catheter or a thoracic surgical procedure. However, should the low frequency blocking capacitors in the electrosurgical generator fail in the conducting state, extremely dangerous low frequency currents of many milliamperes may flow into the patient. Even with properly functioning capacitors, low frequencies up to several milliamperes may be produced by some generators. The results of this study show that the coagulation mode of operation produces greater amounts of low frequency currents than the "pure cutting" mode at the same power setting. These results also demonstrate that the higher the generator power output, the higher the magnitude of the low frequency currents.
Goovaerts, H G; Faes, T J; Raaijmakers, E; Heethaar, R M
1998-11-01
Design considerations and implementation of a multifrequency measuring channel for application in the field of bio-impedance measurement are discussed in this paper. The input amplifier has a differential configuration which is electrically isolated from the remaining circuits. Transformer coupling provides improved common mode rejection when compared to non-isolated input stages. The frequency characteristic of the section between input and demodulator is flat within +/- 0.1 dB between 4 kHz and 1024 kHz. The synchronous demodulator is based on a wideband switched video amplifier. In contrast to commonly used lock--in techniques, the carrier for demodulation is recovered from the input signal by means of a phase-locked loop. This method ensures zero phase shift with respect to the input signal and improves the accuracy of measurement. The system has been developed primarily for thoracic impedance cardiography (TIC) but has also successfully been applied in the field of total body bio-impedance analysis (BIA). At present an electrical impedance tomograph is under development based on the instrumentation described. Results regarding the measurement range and accuracy are given and some recordings of patient data are shown.
Wideband FM demodulation by injection-locked division of frequency deviation
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
BER Performance of Frequency Domain Differential Demodulation OFDM in Flat Fading Channel
Institute of Scientific and Technical Information of China (English)
SONG Lijun; TANG Youxi; LI Shaoqian; HUANG Shunji
2003-01-01
A closed form expression for the bit error rate (BER) performance of frequency domain differential demodulation(FDDD) for orthogonal frequency division multiplexing system in flat fading channel is derived. The performance is evaluated by computer simulation and compared with the time domain differential demodulation(TDDD). The results indicate that the performance of FDDD is better than that of TDDD, and the lower band of BER in the former is lower than that of the latter.
Institute of Scientific and Technical Information of China (English)
LIANGXin; HANGQinglin; XUWenlong
2004-01-01
With frequency offset being taken into account, the performance of an existing coherent M-ary differential phase shift keying (MDPSK) demodulator, which bases on multiple symbols observation, is analyzed in this paper. It is revealed that the frequency offset will induce phase offset in proportion to the frequency offset in recovered carrier, and degrade the performance of demodulation. Aiming at this, a simple modified scheme is proposed to compensate for the phase offset; and theoretical performance analysis and simulation are also provided to show good agreement. Both theoretical and simulation results show that the modified scheme is superior to the original one under frequency offset.
Improved PLL For FM Demodulator
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.
Cao, Zili; Lin, Weihao; Chen, Xinlin; Zeng, Bixin; Xu, Min
2017-02-01
We have presented a novel Single Snapshot Multiple Frequency Demodulation (SSMD) method enabling single snapshot wide field imaging of optical properties of turbid media in the Spatial Frequency Domain. SSMD makes use of the orthogonality of harmonic functions and extracts the modulation transfer function (MTF) at multiple modulation frequencies and of arbitrary orientations and amplitudes simultaneously from a single structured-illuminated image at once. SSMD not only increases significantly the data acquisition speed and reduces motion artifacts but also exhibits excellent noise suppression in imaging as well. The performance of SSMD-SFDI is demonstrated with experiments on both tissue mimicking phantoms and in vivo for recovering optical properties. SSMD is ideal in the implementation of a real-time spatial frequency domain imaging platform, which will open up SFDI for vast applications in, for example, mapping the optical properties of a dynamic turbid medium or monitoring fast temporal evolutions.
Gear Fault Diagnosis Based on Narrowband Demodulation with Frequency Shift and Spectrum Edit
Directory of Open Access Journals (Sweden)
Yu Guo
2016-09-01
Full Text Available To address the difficulties on the vibration feature extraction of gear localized faults for rotating machinery under varying speed conditions, an improved narrowband demodulation method with spectrum edit and frequency shift is proposed in the paper. The vibration signal is acquired and resampled at constant angle increments at first, by which the non-stationary signal is converted into a quasi-stationary signal in the angular domain to reduce the distortions caused by the speed fluctuations. Subsequently, the signal in the angular domain is processed by a synchronous average algorithm, where the noises can be eliminated effectively and the order components corresponding to the gear faults become prominent. Finally, the narrowband demodulation scheme with the spectrum edit and frequency shift is applied on the averaged signal. By using the spectrum edit, most of unconcerned components can be filtered out effectively. Moreover, the frequency shift property of the Fourier transform is employed in the proposed demodulation scheme to obtain a better phase demodulation result. Simulations and experiments support the proposed scheme positively.
Complex demodulation in VLBI estimation of high frequency Earth rotation components
Böhm, S.; Brzeziński, A.; Schuh, H.
2012-12-01
The spectrum of high frequency Earth rotation variations contains strong harmonic signal components mainly excited by ocean tides along with much weaker non-harmonic fluctuations driven by irregular processes like the diurnal thermal tides in the atmosphere and oceans. In order to properly investigate non-harmonic phenomena a representation in time domain is inevitable. We present a method, operating in time domain, which is easily applicable within Earth rotation estimation from Very Long Baseline Interferometry (VLBI). It enables the determination of diurnal and subdiurnal variations, and is still effective with merely diurnal parameter sampling. The features of complex demodulation are used in an extended parameterization of polar motion and universal time which was implemented into a dedicated version of the Vienna VLBI Software VieVS. The functionality of the approach was evaluated by comparing amplitudes and phases of harmonic variations at tidal periods (diurnal/semidiurnal), derived from demodulated Earth rotation parameters (ERP), estimated from hourly resolved VLBI ERP time series and taken from a recently published VLBI ERP model to the terms of the conventional model for ocean tidal effects in Earth rotation recommended by the International Earth Rotation and Reference System Service (IERS). The three sets of tidal terms derived from VLBI observations extensively agree among each other within the three-sigma level of the demodulation approach, which is below 6 μas for polar motion and universal time. They also coincide in terms of differences to the IERS model, where significant deviations primarily for several major tidal terms are apparent. An additional spectral analysis of the as well estimated demodulated ERP series of the ter- and quarterdiurnal frequency bands did not reveal any significant signal structure. The complex demodulation applied in VLBI parameter estimation could be demonstrated a suitable procedure for the reliable reproduction of
Shi, Juanjuan; Liang, Ming; Necsulescu, Dan-Sorin; Guan, Yunpeng
2016-04-01
The energy concentration level is an important indicator for time-frequency analysis (TFA). Weak energy concentration would result in time-frequency representation (TFR) diffusion and thus leading to ambiguous results or even misleading signal analysis results, particularly for nonstationary multicomponent signals. To improve the energy concentration level, this paper proposes a generalized stepwise demodulation transform (GSDT). The rationale of the proposed method is that (1) the generalized demodulation (GD) can map the original signal into an analytic signal with constant instantaneous frequency (IF) and improve the energy concentration level on time-frequency plane, and (2) focusing on a short window around the time instant of interest, a backward demodulation operation can recover the original frequency at the time instant without affecting the improved energy concentration level. By repeating the backward demodulation at every time instant of interest, the TFR of the entire signal can be attained with enhanced energy concentration level. With the GSDT, an iterative GSDT (IGSDT) is developed to analyze multicomponent signal that is subjected to different modulating sources for their constituent components. The IGSDT iteratively demodulates each constituent component to attain its TFR and the TFR of the whole signal is derived from superposing all the resulting TFRs of constituent components. The cross-term free and more energy concentrated TFR of the signal is, therefore, obtained, and the diffusion in the TFR can be reduced. The GSDT-based synchrosqueezing transform is also elaborated to further enhance the GSDT(IGSDT) yielded TFR. The effectiveness of the proposed method in TFA is tested using both simulated monocomponent and multicomponent signals. The application of the proposed method to bearing fault detection is explored. Bearing condition and fault pattern can be revealed by the proposed method resulting TFR. The main advantages of the proposed method
Firla, Marcin; Li, Zhong-Yang; Martin, Nadine; Pachaud, Christian; Barszcz, Tomasz
2016-12-01
This paper proposes advanced signal-processing techniques to improve condition monitoring of operating machines. The proposed methods use the results of a blind spectrum interpretation that includes harmonic and sideband series detection. The first contribution of this study is an algorithm for automatic association of harmonic and sideband series to characteristic fault frequencies according to a kinematic configuration. The approach proposed has the advantage of taking into account a possible slip of the rolling-element bearings. In the second part, we propose a full-band demodulation process from all sidebands that are relevant to the spectral estimation. To do so, a multi-rate filtering process in an iterative schema provides satisfying precision and stability over the targeted demodulation band, even for unsymmetrical and extremely narrow bands. After synchronous averaging, the filtered signal is demodulated for calculation of the amplitude and frequency modulation functions, and then any features that indicate faults. Finally, the proposed algorithms are validated on vibration signals measured on a test rig that was designed as part of the European Innovation Project 'KAStrion'. This rig simulates a wind turbine drive train at a smaller scale. The data show the robustness of the method for localizing and extracting a fault on the main bearing. The evolution of the proposed features is a good indicator of the fault severity.
Institute of Scientific and Technical Information of China (English)
杨玮萍; 郑宾; 张志刚; 郭华玲; 陈栋; 王余敬
2016-01-01
激光外差干涉信号属于宽带高频信号，针对这一特点，提出了一种新型的激光外差干涉信号的高频调制信号解调系统。在AD8302相位解调方法的基础上，锁相环的设计可以消除解调结果中的差频信号。结果表明，相比于MATLAB软件解调和AD8302直接解调，该解调系统可以更准确地解调出样品表面1 MHz的微振动信号。因此，本系统是一种有效可行的相位解调方法。%The laser heterodyne interference signals belong to the wideband and high-frequency signals. According to this characteristic,a new kind of high-frequency modulated signals demodulation system for laser heterodyne in⁃terference signals is proposed. Based on the method of phase demodulation with AD8302,the design of phase locked loop can eliminate the differential frequency signals in the demodulation results. The results show that this demodulation system can demodulate 1 MHz micro-vibration signal on the surface of the sample accurately,com⁃pared with the MATLAB software demodulation and AD8302 direct demodulation. Therefore,this system is an effec⁃tive and feasible method for phase demodulation.
Demodulation effect is observed in neurones by exposure to low frequency modulated microwaves
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.
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.
Nadeau, Kyle P.; Durkin, Anthony J.; Tromberg, Bruce J.
2014-05-01
We have developed a method for extracting spatial frequency information content from biological tissue, which is used to calculate tissue optical properties and determine tissue structural orientation. This demodulation method employs a two-dimensional Hilbert transform using a spiral phase function in Fourier space. The approach presented here allows for the determination of tissue optical properties using a single frame of data for each modulation frequency, increasing imaging speed by two to threefold versus conventional, three-phase spatial frequency domain imaging (SFDI). This new single-phase Hilbert transform approach recovers optical property and scattering orientation index values within 1% and 10% of three-phase SFDI, respectively. These results suggest that, using the Hilbert demodulation technique, SFDI data acquisition speed can be increased significantly while preserving data quality, which will help us move forward toward the implementation of a real-time SFDI platform.
High-Order Frequency-Locked Loops
DEFF Research Database (Denmark)
Golestan, Saeed; Guerrero, Josep M.; Quintero, Juan Carlos Vasquez
2017-01-01
In very recent years, some attempts for designing high-order frequency-locked loops (FLLs) have been made. Nevertheless, the advantages and disadvantages of these structures, particularly in comparison with a standard FLL and high-order phase-locked loops (PLLs), are rather unclear. This lack......) as well as a unification between FLLs and PLLs is presented....
van Doninck, A.; Dendoncker, M.; Adriaensen, F.; Delbeke, P.; Rolle, A.; Craey, T.; Krekels, S.
: This paper highlights a multi-channel, multi-frequency DVB-RCS compatible burst demodulator implementation in a System On Programmable Chip (SOPC) technology. The core of the demodulator architecture is a SOPC device with an ARM processor located internally in FPGA. The ARM processor performs the hard real time signal processing functions and is supported by a COTS standard PC based processor module running Linux/RT-Linux for the non-hard real-time demodulator functions. The implemented architecture differs completely from classic multi-channel solutions, in which the multi- channel functionality is realised by means of a multiple instantiation of the entire demodulator. The paper also discusses the followed methodology for the SOPC design. Keywords: DVB-RCS, multi-channel, multi-frequency, SOPC, FPGA, ARM, RT-Linux
Two novel automatic frequency tracking loops
Aguirre, Sergio; Hinedi, Sami
1989-01-01
Two automatic-frequency-control (AFC) loops are introduced and analyzed in detail. The algorithms are generalizations of the well known cross-product AFC loop with improved performance. The first estimator uses running overlapping discrete Fourier transforms to create a discriminator curve proportional to the frequency estimation error, whereas the second one preprocesses the received data and then uses an extended Kalman filter to estimate the input frequency. The algorithms are tested by computer simulations in a highly dynamic environment at low carrier/noise ratio (CNR). The algorithms are suboptimum tracking schemes with a larger frequency-error variance compared to an optimum strategy, but they offer simplicity of mechanization and a CNR with a very low operating threshold.
Frequency acquisition techniques for phase locked loop
Talbot, Daniel
2012-01-01
Many good phaselocked loops (PLL) books exist. However, how to acquire the input frequency from an unlocked state is rarely covered. This book explores the methods for achieving this locked state for a variety of conditions. Using a minimum of mathematics, it introduces engineers to performance limitations of phase/frequency detector based PLL, the quadricorrelator method for both continuous and sampled mode, sawtooth ramp-and-sample phase detector, self-sweeping self-extinguishing topology, and sweep methods using quadrature mixer based lock detection. Digital implementations versus analog are also considered.
Research of Frequency Discriminator on Frequency Lock Loops
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Frequency lock loops (FLL) discriminating algorithms for direct-sequence spread-spectrum are discussed. The existing algorithms can't solve the problem of data bit reversal during one pre-detection integral period. And when the initial frequency offset is large, the frequency discriminator can't work normally. To solve these problems, a new FLL discriminating algorithm is introduced. The least-squares discriminator is used in this new algorithm. As the least-squares discriminator has a short process unit period, the corresponding frequency discriminating range is large. And the data bit reversal just influence one process unit period, so the least-squares discriminated result will not be affected. Compared with traditional frequency discriminator, the least-squares algorithm can effectively solve the problem of data bit reversal and can endure larger initial frequency offset.
Digital Demodulator For Advanced Receiver
Sadr, Ramin; Hurd, William J.
1990-01-01
Complexity and cost reduced by new design for half-band filters. Digital demodulator designed for use in reception of phase- and amplitude-modulated digital signals of bandwidths up to 15 MHz on microwave carriers. System performs coherent demodulation in phase and in quadrature with carrier locked in phase to intermediate frequency of 10 MHz. Design suitable for fabrication in very-large-scale integrated circuitry. Principal innovative feature of demodulator is design of half-band digital low-pass filters that remove sum-frequency components.
Coherent Digital Demodulation of a Residual Carrier Signal Using IF Sampling
Sfeir, R.; Aguirre, S.; Hurd, W. J.
1984-01-01
An analysis is presented of a digital technique for the coherent demodulation of a residual carrier signal with a biphase modulated square wave subcarrier. The processing technique employs the concept of intermediate frequencies IF sampling. An optimum Costas loop is used for subcarrier demodulation and data-aided carrier tracking, i.e., combined Costas and residual carrier tracking. It is shown that the loops perform essentially the same as the corresponding analog loops in terms of signal-to-noise ratio and loop bandwidth. The sampling does not introduce biases or other significant effects on the loops, provided that the loop bandwidth is very small compared to the symbol rate, and that the number of samples per symbol is large compared to inverse loop bandwidth.
DEFF Research Database (Denmark)
Zibar, Darko
2007-01-01
We present a modelling technique and noise analysis of a clock recovery scheme based on an optoelectronic phase-locked loop. We treat the prob- lem using techniques from stochastic processes and stochastic differential equations. A set of stochastic differential (Langevin) equations describing......-locked loop with noise at a bit-rate of 160 Gb/s. It has been shown that it is important to reduce the time delay in the loop since it results in the increased timing jitter of the recovered clock signal. We also investigate the requirement for the free-running timing jitter of the local electrical......, optoelectronic phase-locked loop based clock recovery operating at 320 Gb/s is demonstrated. Optical regenerator with clock recovery, based on an optoelectronic phase- locked loop, is also described using techniques from stochastic calculus. An analytical expression for the power spectral density of the retimed...
VLSI digital PSK demodulator for space communication
Hansen, Flemming; Thomsen, Jan H.; Jacobsen, Freddy L.; Olsen, Karsten
1993-02-01
This paper describes the design of a BPSK/QPSK demodulator implemented using multirate digital signal processing in a CMOS ASIC. The demodulator is fully programmable via serial and parallel interfaces, and handles symbol rates from 125 sym/s to 4 Msym/s. It performs at less than 0.5 dB degradation from ideal BER vs. E(b)/N(o) characteristics. System design considerations lead to the choice of a complex IF scheme with sampling at four times the intermediate frequency, and a combined analog and digital matched filtering based on the pulselet concept. Signal processing algorithms include the Costas carrier phase error detector, the zero-crossing detector for timing error, and algorithms for lock detection and loop filtering. Simulations of the entire demodulator including the ASIC part is accomplished by proprietary software. The ASIC is manufactured in a radiation tolerant 1-micron CMOS gate array process using 34085 gates. The main application area is spaceborne coherent transponders.
Demodulator electronics for laser vibrometry
Dudzik, G.; Waz, A. T.; Kaczmarek, P. R.; Antonczak, A. J.; Sotor, J. Z.; Krzempek, K.; Sobon, G.; Abramski, K. M.
2012-06-01
One of the most important parts of a fiber-laser vibrometer is demodulation electronic section. The distortion, nonlinearity, offset and added noise of measured signal come from electronic circuits and they have direct influence on finale measuring results. Two main parameters of an investigated vibrating object: velocity V(t) and displacement s(t), influence of detected beat signals. They are: the Doppler frequency deviation f(t) and phase shift φ(t), respectively. Because of wide range of deviations it is difficult to use just one demodulator. That is the reason why we use three different types of demodulators. The first one is the IQ demodulator, which is the most sensitive one and its output is proportional to the displacement. Each IQ channel is sampled simultaneously by an analog to digital converter (ADC) integrated in a digital signal processor (DSP). The output signals from the two FM demodulators are proportional to the frequency deviation of heterodyne signals. They are sensitive directly to the velocity of the object. The main disadvantage of scattered light interferometry system is a "speckle effect", appearing in relatively large amplitude fluctuation of a heterodyne signal. To minimize "speckle effect" influence on quality of beat signals we applied the automatic gain control (AGC) system. Data acquisition, further signal processing (e.g. vibration frequency spectra) and presentation of results is realized by PC via USB interface.
Self-Mixing Demodulation for Coherent Phase-Sensitive OTDR System
Directory of Open Access Journals (Sweden)
Haijun He
2016-05-01
Full Text Available Phase-sensitive optical time domain reflectometry (Ф-OTDR attracts much attention due to its capability of telling the type and position of an intrusion simultaneously. In recent decades, coherent Ф-OTDR has been demonstrated to realize long-distance detection. For coherent Ф-OTDR, there are three typical demodulation schemes in the reported studies. However, they still cannot realize real-time monitoring to satisfy practical demands. A simple and effective demodulation method based on self-mixing has been put forward to demodulate the beat signal in coherent Ф-OTDR. It not only saves a local electrical oscillator and frequency locked loop, but also demodulates the beat signal without residual frequency. Several vibrations with different frequency were separately applied at the same location of a 42.5 km fiber. The spatial resolution of 10 m and frequency response range from 8 Hz to 980 Hz have been achieved. The precise location with signal-to-noise ratio of 21.4 dB and broadband measurement demonstrate the self-mixing scheme can demodulate the coherent Ф-OTDR signal effectively.
Frequency Control Loop for Drift Tube Linac
Energy Technology Data Exchange (ETDEWEB)
Kwon, Hyeok Jung; Kim, Han Sung; Seol, Kyung Tae; Song, Young Gi; Jang, Ji Ho; Cho, Yong Sub [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2013-10-15
In this paper, the preparation of the frequency tracking of the RCCS by connecting the RCCS to low level RF (LLRF) system is described. KOMAC 100-MeV proton accelerator is under operation and supply beam to users. We are developing frequency control function in the LLRF system to control the RCCS in frequency control mode. After the test in the test bench, the system will be applied to the 100-MeV DTL RCCS in order to supply better quality beam to users. A 100-MeV proton accelerator has been developed and the operation and beam service started at Korea Multipurpose Accelerator Complex (KOMAC) in June 2013. The accelerator consists of a 50-keV proton injector, a 3-MeV radio frequency quadrupole (RFQ) and 100-MeV drift tube linac (DTL). The resonance frequency of the DTL tanks are controlled by using the resonance frequency control cooling system (RCCS), which are installed at every each tank. Until now, the RCCS has been operating in constant temperature mode which means that the frequency was measured with respect to the RCCS supply temperature before the RF operation, and then the RCCS operates with that temperature throughout the whole operation. The constant temperature operation is simple but the RF stability is not good because many perturbations such as RCCS supply temperature error can cause a frequency change. To stabilize the system better, it is necessary to operate the RCCS in frequency tracking mode.
Open-loop frequency response for a chaotic masking system
Institute of Scientific and Technical Information of China (English)
Huang Xian-Gao; Yu Pei; Huang Wei
2006-01-01
In this paper, a new numerical simulation approach is proposed for the study of open-loop frequency response of a chaotic masking system. Using Chua's circuit and the Lorenz system as illustrative examples, we have shown that one can employ chaos synchronization to separate the feedback network from a chaotic masking system, and then use numerical simulation to obtain the open-loop synchronization response, the phase response, and the amplitude response of a chaotic masking system. Based on the analysis of the frequency response, we have also proved that changing the amplitude of the exciting (input) signal within normal working domain does not influence the frequency response of the chaotic masking system. The new numerical simulation method developed in this paper can be extended to consider the open-loop frequency response of other systems described by differential or difference equations.
Constant-Frequency Pulsed Phase-Locked-Loop Measuring Device
Yost, William T.; Cantrell, John H.; Kushnick, Peter W.
1992-01-01
Constant-frequency pulsed phase-locked-loop measuring device is sensitive to small changes in phase velocity and easily automated. Based on use of fixed-frequency oscillator in measuring small changes in ultrasonic phase velocity when sample exposed to such changes in environment as changes in pressure and temperature. Automatically balances electrical phase shifts against acoustical phase shifts to obtain accurate measurements of acoustical phase shifts.
2015-01-01
The present article relates in general to digital demodulation of Binary Frequency Shift Keying (BFSK). The objective of the present research is to obtain a new processing method for demodulating BFSK-signals in order to reduce hardware complexity in comparison with other methods reported. The solution proposed here makes use of the matched filter theory and curve segmentation algorithms. This paper describes the integration and configuration of a Sampler Correlator and curve segmentation blo...
Synchronous interferometric demodulation of Placido mires applied to corneal topography
Servin, Manuel
2012-01-01
This paper presents a novel digital interferometric method to demodulate Placido fringe patterns. This is a synchronous method which uses a computer-stored conic-wavefront as demodulating reference. Here we focuses on the experimental aspects to phase-demodulate Placido mires applied to corneal topography. This synchronous method is applied to two topographic Placido images and their de-modulated corneal-slope deformation is estimated. This conic-interferometric method is highly robust against typical "noisy" signals in Placido topography such as: reflected eyelashes and iris structures. That is because the eyelashes and the iris structure are high frequency "noisy" signals corrupting the reflected Placido mire, so they are filtered-out by this method. Digital synchronous interferometry is here applied for the first time to demodulate corneal topographic concentric-rings images (Patent pending at the USPTO).
Directory of Open Access Journals (Sweden)
Kaiyu Wang
2014-01-01
Full Text Available This paper presents an efficient all digital carrier recovery loop (ADCRL for quadrature phase shift keying (QPSK. The ADCRL combines classic closed-loop carrier recovery circuit, all digital Costas loop (ADCOL, with frequency feedward loop, maximum likelihood frequency estimator (MLFE so as to make the best use of the advantages of the two types of carrier recovery loops and obtain a more robust performance in the procedure of carrier recovery. Besides, considering that, for MLFE, the accurate estimation of frequency offset is associated with the linear characteristic of its frequency discriminator (FD, the Coordinate Rotation Digital Computer (CORDIC algorithm is introduced into the FD based on MLFE to unwrap linearly phase difference. The frequency offset contained within the phase difference unwrapped is estimated by the MLFE implemented just using some shifter and multiply-accumulate units to assist the ADCOL to lock quickly and precisely. The joint simulation results of ModelSim and MATLAB show that the performances of the proposed ADCRL in locked-in time and range are superior to those of the ADCOL. On the other hand, a systematic design procedure based on FPGA for the proposed ADCRL is also presented.
Wu, Te-Kao (Inventor)
1994-01-01
A multireflector antenna utilizes a frequency-selective surface (FSS) in a subreflector to allow signals in two different RF bands to be selectively reflected back into a main reflector and to allow signals in other RF bands to be transmitted through it to the main reflector for primary focus transmission. A first approach requires only one FSS at the subreflector which may be an array of double-square-loop conductive elements. A second approach uses two FSS's at the subreflector which may be an array of either double-square-loop (DSL) or double-ring (DR). In the case of DR elements, they may be advantageously arranged in a triangular array instead of the rectangular array for the DSL elements.
Digital demodulator for wide bandwidth SAR
DEFF Research Database (Denmark)
Jørgensen, Jørn Hjelm
2000-01-01
A novel approach to the design of efficient digital quadrature demodulators for wide bandwidth SAR systems is described. Efficiency is obtained by setting the intermediate frequency to 1/4 the ADC sampling frequency. One channel is made filter-free by synchronizing the local oscillator...... with the output decimator. The filter required by the other channel is optimized through global search using the system level performance metrics integrated sidelobe level ratio (ISLR) and peak sidelobe level ratio (PSLR)....
Planetary Gearbox Fault Diagnosis Using Envelope Manifold Demodulation
Weigang Wen; Gao, Robert X.; Weidong Cheng
2016-01-01
The important issue in planetary gear fault diagnosis is to extract the dependable fault characteristics from the noisy vibration signal of planetary gearbox. To address this critical problem, an envelope manifold demodulation method is proposed for planetary gear fault detection in the paper. This method combines complex wavelet, manifold learning, and frequency spectrogram to implement planetary gear fault characteristic extraction. The vibration signal of planetary gear is demodulated by w...
2016-01-01
The current article addresses digital implementation of new demodulation schemes for Binary Frequency Shift Keying (BFSK), and has two main objectives: of the description of the performance of the new processing method and its implementation on FPGA technology. Performance is analyzed by means of the total number of demodulated bits free of errors without noise, and by means of the BER parameter. The proposed method exhibits to have better performance than the solutions reported. Additionally...
Dvorak, Steven L.; Sternberg, Ben K.; Feng, Wanjie
2017-03-01
In this paper we discuss the design and verification of wide-band, multi-frequency, tuning circuits for large-moment Transmitter (TX) loops. Since these multi-frequency, tuned-TX loops allow for the simultaneous transmission of multiple frequencies at high-current levels, they are ideally suited for frequency-domain geophysical systems that collect data while moving, such as helicopter mounted systems. Furthermore, since multi-frequency tuners use the same TX loop for all frequencies, instead of using separate tuned-TX loops for each frequency, they allow for the use of larger moment TX loops. In this paper we discuss the design and simulation of one- and three-frequency tuned TX loops and then present measurement results for a three-frequency, tuned-TX loop.
A low-power ASK demodulator for inductively coupled implantable electronics
DEFF Research Database (Denmark)
Gudnason, Gunnar
2000-01-01
An amplitude shift keying (ASK) demodulator is presented which is suitable for implantable electronic devices that are powered through an inductive link. The demodulator has been tested with carrier frequencies in the range 1-15 MHz, covering most commonly used frequencies. Data rates up to several...
Nanometer frequency synthesis beyond the phase-locked loop
Xiu, Liming
2012-01-01
This text presents a latest technology in frequency synthesis. The technology includes three key components: Time-Average-Frequency, Flying-Adder architecture, and Digital-to-Frequency converter. The coverage presents the case, through real application examples, that this Flying-Adder technology creates a new frontier for modern IC design. In so doing, it also discusses the weaknesses of current frequency synthesis techniques in dealing with certain problems in modern IC design. The result is a complete picture of this technology for professional design engineers, researchers, and advanced students.
LOW-FREQUENCY MAGNETIC FIELD SHIELDING BY A CIRCULAR PASSIVE LOOP AND CLOSED SHELLS
Directory of Open Access Journals (Sweden)
V.S. Grinchenko
2016-05-01
Full Text Available Purpose. To analyze the shielding factors for a circular passive loop and conductive closed shells placed in a homogeneous low-frequency magnetic field. Methodology. We have obtained simplified expressions for the shielding factors for a circular passive loop and a thin spherical shell. In addition, we have developed the numerical model of a thin cubical shell in a magnetic field, which allows exploring its shielding characteristics. Results. We have obtained dependences of the shielding factors for passive loops and shells on the frequency of the external field. Analytically determined frequency of the external magnetic field, below which field shielding of a passive loop is expedient to use, above which it is advisable to use a shielding shell.
Frequency stability optimization of an OEO using phase-locked-loop and self-injection-locking
Fu, Rongrong; Jin, Xiaofeng; Zhu, Yanhong; Jin, Xiangdong; Yu, Xianbin; Zheng, Shilie; Chi, Hao; Zhang, Xianmin
2017-03-01
Frequency stability optimization of an X-band optoelectronic oscillator (OEO) using the technique of phase-locked loop (PLL) and dual loop self-injection-locking (DSIL) is proposed and demonstrated. The relationship between the loop transfer characteristics of a PLL and the phase noise of the oscillation signal is analyzed. The close-in phase noise and frequency overlapping Allan deviation (ADEV) of the OEO are optimized by properly choosing the bandwidth of the loop filter of the PLL. The phase noise of the OEO is suppressed by 41.5 dB at 100 Hz offset and 21.3 dB at 10 kHz offset with PLL and DSIL. The frequency overlapping ADEV achieved 7.03×10-12 at average time of 100 s, which is several orders of magnitude better than that of the DSIL OEO and the free-running OEO, proves the high oscillation stability of proposed scheme.
Full investigation of the resonant frequency servo loop for resonator fiber-optic gyro.
Ma, Huilian; Lu, Xiao; Yao, Linzhi; Yu, Xuhui; Jin, Zhonghe
2012-07-20
Resonator fiber-optic gyro (RFOG) is a high-accuracy inertial rotation sensor based on the Sagnac effect. A high-accuracy resonant frequency servo loop is indispensable for a high-performance RFOG. It is composed of a frequency discriminator, a loop filter, and a laser actuator. Influences of the loop parameters are fully developed. Optimized loop parameters are obtained by considering the noise reduction and wide dynamic performance of the RFOG. As a result, with the integration time of 10 s, the accuracy of the resonant frequency loop is increased to 0.02 Hz (1σ). It is equivalent to a rotation rate of 0.067°/h, which is close to the shot noise limit for the RFOG, while a minimum rotation of ±0.05°/s has been carried out simultaneously. These are the best results reported to date, to the best of our knowledge, for an RFOG using the miniature semiconductor laser that benefits from the optimization of the resonant frequency servo-loop parameters.
High-speed demodulation system of identical weak FBGs based on FDML wavelength swept laser
Wang, Yiming; Liu, Quan; Wang, Honghai; Hu, Chenchen; Zhang, Chun; Li, Zhengying
2017-04-01
An identical weak reflection FBGs demodulation system based on a FDML laser is proposed. The laser is developed to output a continuous wavelength-swept spectrum in the scanning frequency of 120 kHz over a spectral range of more than 10nm at 1.54 μm. Based on this high-speed wavelength-swept light and the optical transmission delay effect, the demodulation system obtains the location and wavelength information of all identical weak FBGs by the reflected spectrum within each scanning cycle. By accessing to a high-speed FPGA processing module, continuous demodulation of 120 kHz is realized. The system breakthroughs the bandwidth of the laser to expand the sensors capacity and greatly improves the demodulation speed of a TDM sensing network. The experiments show the system can distinguish and demodulate the identical weak FBGs and measure the 4 kHz vibration at 120 kHz demodulation speed.
Keymeulen, Didier; Ferguson, Michael I.; Fink, Wolfgang; Oks, Boris; Peay, Chris; Terrile, Richard; Cheng, Yen; Kim, Dennis; MacDonald, Eric; Foor, David
2005-01-01
We propose a tuning method for MEMS gyroscopes based on evolutionary computation to efficiently increase the sensitivity of MEMS gyroscopes through tuning. The tuning method was tested for the second generation JPL/Boeing Post-resonator MEMS gyroscope using the measurement of the frequency response of the MEMS device in open-loop operation. We also report on the development of a hardware platform for integrated tuning and closed loop operation of MEMS gyroscopes. The control of this device is implemented through a digital design on a Field Programmable Gate Array (FPGA). The hardware platform easily transitions to an embedded solution that allows for the miniaturization of the system to a single chip.
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.
Frequency translation loops for RF filtering : theory and design
Youssef, Shadi Shawky Tawfik
2013-01-01
Modern wireless transceivers are required to operate over a wide range of frequencies in order to support the multitude of currently available wireless standards. Wideband operation also enables future systems that aim for better utilization of the available spectrum through dynamic allocation. As s
Constant frequency pulsed phase-locked loop measuring device
Yost, William T. (Inventor); Kushnick, Peter W. (Inventor); Cantrell, John H. (Inventor)
1993-01-01
A measuring apparatus is presented that uses a fixed frequency oscillator to measure small changes in the phase velocity ultrasonic sound when a sample is exposed to environmental changes such as changes in pressure, temperature, etc. The invention automatically balances electrical phase shifts against the acoustical phase shifts in order to obtain an accurate measurement of electrical phase shifts.
Constant frequency pulsed phase-locked loop measuring device
Yost, William T.; Kushnick, Peter W.; Cantrell, John H.
1993-06-01
A measuring apparatus is presented that uses a fixed frequency oscillator to measure small changes in the phase velocity ultrasonic sound when a sample is exposed to environmental changes such as changes in pressure, temperature, etc. The invention automatically balances electrical phase shifts against the acoustical phase shifts in order to obtain an accurate measurement of electrical phase shifts.
Constant frequency pulsed phase-locked loop measuring device
Yost, William T.; Kushnick, Peter W.; Cantrell, John H.
1991-08-01
A measuring apparatus is presented that uses a fixed frequency oscillator to measure small changes in the phase velocity ultrasonic sound when a sample is exposed to environmental changes such as changes in pressure, temperature, etc. The invention automatically balances electrical phase shifts against the acoustical phase shifts in order to obtain an accurate measurement of electrical phase shifts.
Energy Technology Data Exchange (ETDEWEB)
Park, Kyung Mi; Seo, Yun Seok; Chun, Heoung Jae [Yonsei University, Seoul (Korea, Republic of); Hong, Ik Pyo [Kongju National University, Cheonan (Korea, Republic of); Park, Yong Bae [Ajoo University, Suwon (Korea, Republic of); Kim, Yoon Jae [Agency for defense development, Daejeon (Korea, Republic of)
2015-01-15
Residual stresses occur in frequency-selective surface (FSS)-embedded composite structures after co-curing due to differences between the coefficients of thermal expansion between composite skins and FSSs. Furthermore, the electromagnetic characteristics may be affected by the deformation of the FSS pattern by residual stresses. Therefore, we studied the changes in electromagnetic characteristics due to the deformation of FSS, using residual stresses to deform loop-type FSS-embedded hybrid composites. We considered the effects of loop-type FSS patterns of equal dimension as well as the stacking sequences of composite laminates on the electromagnetic characteristics of FSSs: Square loop, triangular loop and circular loop. The stacking sequences of composite laminates considered in this study were [0]{sub 8}, [0/90]{sub 4}, [+-45]{sub 4} and [0/+-45/90]{sub 2}. The FSS was located between composite laminates in the middle plane. To determine the residual stresses and deformations in the FSS embedded laminate structures, the thermal loading condition in the finite element analysis was induced by cooling the hybrid structures from 125 .deg. C to 20 .deg. C based on the cure cycle of the composite. Also, the electromagnetic reflection characteristics of the hybrid structures were predicted using deformed models by residual stresses, considering the effects of stacking sequence of composite laminates. The results showed that the maximum residual stresses and deformations were produced in the [0]{sub 8} composites with all three loop-types of FSS pattern. However, the maximum resonance frequency shifts occurred in the square and triangle loop-types with stacking sequence of [0]{sub 8} , while the maximum resonance frequency shift occurred in the circular loop-type with stacking sequence of [0/+-45/90]{sub 2}.
A Multi-Gigabit Parallel Demodulator and Its FPGA Implementation
Lin, Changxing; Zhang, Jian; Shao, Beibei
This letter presents the architecture of multi-gigabit parallel demodulator suitable for demodulating high order QAM modulated signal and easy to implement on FPGA platform. The parallel architecture is based on frequency domain implementation of matched filter and timing phase correction. Parallel FIFO based delete-keep algorithm is proposed for timing synchronization, while a kind of reduced constellation phase-frequency detector based parallel decision feedback PLL is designed for carrier synchronization. A fully pipelined parallel adaptive blind equalization algorithm is also proposed. Their parallel implementation structures suitable for FPGA platform are investigated. Besides, in the demonstration of 2Gbps demodulator for 16QAM modulation, the architecture is implemented and validated on a Xilinx V6 FPGA platform with performance loss less than 2dB.
Optimization of three-loop missile autopilot gain under crossover frequency constraint
Institute of Scientific and Technical Information of China (English)
M.A. ABD-ELATIF; Long-jun QIAN; Yu-ming BO
2016-01-01
The open-loop crossover frequency is pointed as an important parameter for practical autopilot design. Since different gain designs may achieve the same open-loop crossover frequency, it should be neither considered as a performance objective of the optimal autopilot design-schemes nor neglected. Besides, the main assignment of the autopilot is to drive the missile to track the acceleration commands, so the autopilot gain design should be evaluated directly according to the resultant tracking performance. For this purpose, an optimal design methodology of the three-loop missile autopilot is introduced based on constraint optimization technique, where the tracking performance is established analytically as the design objective and the open-loop crossover frequency is formed as inequality constraint function, both are manipulated in terms of stable characteristic parameters of the autopilot closed-loop. The proposed technique is implemented with the assistance of a numerical optimization algorithm which automatically adjusts the design parameters. Finally, numerical simulation results are provided to demonstrate the effectiveness and feasibility of the proposed approach compared with that in some references.
Enhancement of VCO Linearity and Phase Noise by Implementing Frequency Locked Loop
DEFF Research Database (Denmark)
Ayranci, E; Christensen, K; Andreani, Pietro
2007-01-01
This paper investigates the on-chip implementation of a frequency locked loop (FLL) over a VCO that decreases the phase noise and linearizes the transfer function. Implementation of the FLL inside a PLL is also investigated and a possible application is highlighted. Design of a special kind of low...... noise frequency detector without a reference frequency (frequency-to-voltage converter), which is the most critical component of the FLL, is also presented in a 0.25 mum BiCMOS process. Linearization and approximately 15 dBc/Hz phase noise suppression is demonstrated over a moderate phase noise LC VCO...
Hardware-in-the-loop (HIL) Test of Demand as Frequency Controlled Reserve (DFR)
DEFF Research Database (Denmark)
Wu, Qiuwei; Zimmermann, K.; Østergaard, Jacob;
2016-01-01
This paper presents the hardware-in-the-loop (HIL) test of the demand as frequency controlled reserve (DFR). The HIL test refers to a test in which parts of a pure simulation have been replaced by actual physical components. It is used to understand the behavior of a new device or controller...
Development of scalable frequency and power Phase-Locked Loop in 130nm CMOS technology
Firlej, M; Idzik, M; Moron, J; Swientek, K
2014-01-01
The design and measurements results of a prototype very low power Phase-Locked Loop (PLL) ASIC for applications in readout systems of particle physics detectors are presented. The PLL was fabricated in 130 nm CMOS technology. It was designed and simulated for frequency range 10 MHz–3.5 GHz. Four division factors i.e. 6, 8, 10 and 16 were implemented in the PLL feedback loop. The main PLL block-voltage controlled oscillator (VCO) should work in 16 frequency ranges/modes, switched either manually or automatically. Preliminary measurements done in frequency range 20 MHz–1.6 GHz showed that the ASIC is functional and generates proper clock signal. The automatic VCO mode switching, one of the main design goals, was positively verified. Power consumption of around 0.6mW was measured at 1 GHz for a division factor equal to 10.
de Boer, Betteco J; Peper, C Lieke E; Beek, Peter J
2011-06-20
In bimanual coordination, interactions between the limbs result in attraction to in-phase and antiphase coordination. Increasing movement frequency leads to decreasing stability of antiphase coordination, often resulting in a transition to the more stable in-phase pattern. It is unknown, however, how this frequency-induced loss of stability is engendered in terms of the interlimb interactions underwriting bimanual coordination. The present study was conducted to help resolve this issue. Using an established method (based on comparison of various unimanual and bimanual tasks involving both passive and active movements), three sources of interlimb interaction were dissociated: (1) integrated timing of feedforward signals, (2) afference-based correction of relative phase errors, and (3) phase entrainment by contralateral afference. Results indicated that phase entrainment strength remained unaffected by frequency and that the stabilizing effects of error correction and integrated timing decreased with increasing frequency. Their contributions, however, reflected an interesting interplay as frequency increased. For moderate frequencies coordinative stability was predominantly secured by integrated timing processes. However, at high frequencies, the stabilization of the antiphase pattern required combined contributions of both integrated timing and error correction. In sum, increasing frequency was found to induce a shift from predominantly open-loop control to more closed-loop control. The results may be accounted for by means of an internal forward model for sensorimotor integration in which the sensory signals are compared to values predicted on the basis of efference copies.
Ultra-high-frequency piecewise-linear chaos using delayed feedback loops
Cohen, Seth D.; Rontani, Damien; Gauthier, Daniel J.
2012-12-01
We report on an ultra-high-frequency (>1 GHz), piecewise-linear chaotic system designed from low-cost, commercially available electronic components. The system is composed of two electronic time-delayed feedback loops: A primary analog loop with a variable gain that produces multi-mode oscillations centered around 2 GHz and a secondary loop that switches the variable gain between two different values by means of a digital-like signal. We demonstrate experimentally and numerically that such an approach allows for the simultaneous generation of analog and digital chaos, where the digital chaos can be used to partition the system's attractor, forming the foundation for a symbolic dynamics with potential applications in noise-resilient communications and radar.
ALTERATIONS IN FREQUENCY OF ULNAR LOOPS AND ‘ATD’ ANGLE IN CONGENITAL HEART DISEASE
Directory of Open Access Journals (Sweden)
Jaywant
2016-01-01
Full Text Available INTRODUCTION Dermatoglyphics is a scientific study of epidermal ridge configuration on palm, soles and fingertips valuable for medico legal and genetic investigations. Dermatoglyphics form in utero during early gestation and may be influenced by genetic and environmental factors operating at that time. Present investigation was undertaken to study alterations in dermatoglyphic patterns with special reference to various congenital heart diseases (CHD. The study involved 102 cases of CHD and 100 cases of normal individuals. It was observed that percent frequency of ulnar loops significantly increased in CHD group as compared to control group. Mean 'atd' angle was also increased in CHD group as compared to control group indicating distal displacement of palmar axial triradius (t. Thus, rise in frequency of ulnar loops and increase in 'atd' angle can be considered as one of the diagnostic criteria for CHD.
An automatic frequency control loop using overlapping DFTs (Discrete Fourier Transforms)
Aguirre, S.
1988-01-01
An automatic frequency control (AFC) loop is introduced and analyzed in detail. The new scheme is a generalization of the well known Cross Product AFC loop that uses running overlapping discrete Fourier transforms (DFTs) to create a discriminator curve. Linear analysis is included and supported with computer simulations. The algorithm is tested in a low carrier to noise ratio (CNR) dynamic environment, and the probability of loss of lock is estimated via computer simulations. The algorithm discussed is a suboptimum tracking scheme with a larger frequency error variance compared to an optimum strategy, but offers simplicity of implementation and a very low operating threshold CNR. This technique can be applied during the carrier acquisition and re-acquisition process in the Advanced Receiver.
Real-time open-loop frequency response analysis of flight test data
Bosworth, J. T.; West, J. C.
1986-01-01
A technique has been developed to compare the open-loop frequency response of a flight test aircraft real time with linear analysis predictions. The result is direct feedback to the flight control systems engineer on the validity of predictions and adds confidence for proceeding with envelope expansion. Further, gain and phase margins can be tracked for trends in a manner similar to the techniques used by structural dynamics engineers in tracking structural modal damping.
Comparison between Cyclic Statistics and Envelope Demodulation%循环统计量分析与包络解调分析的对比
Institute of Scientific and Technical Information of China (English)
姜鸣; 陈进
2004-01-01
In this paper, demodulation performance of first-order cyclic statistics and second-order cyclic statistics for amplitude modulation signals is introduced. By theoretical research, it is proved that cyclic mean does not possess demodulation performance for amplitude modulation signals, but cyclic autocorrelation function can extract frequency components from amplitude modulation signals.Based on the above, both cyclic autocorrelation function and envelope demodulation based on Hilbert transform are compared. The results show that the two kinds of analysis methods have similar performance for demodulation, in the mean time it is pointed out that they also possess essential distinction, and cyclic autocorrelation function is better to demodulate amplitude modulation signals.
Directory of Open Access Journals (Sweden)
Zheng You
2010-07-01
Full Text Available Micro-cantilever sensors for mass detection using resonance frequency have attracted considerable attention over the last decade in the field of gas sensing. For such a sensing system, an oscillator circuit loop is conventionally used to actuate the micro-cantilever, and trace the frequency shifts. In this paper, gas experiments are introduced to investigate the mechanical resonance frequency shifts of the micro-cantilever within the circuit loop(mechanical resonance frequency, MRF and resonating frequency shifts of the electric signal in the oscillator circuit (system working frequency, SWF. A silicon beam with a piezoelectric zinc oxide layer is employed in the experiment, and a Self-Actuating-Detecting (SAD circuit loop is built to drive the micro-cantilever and to follow the frequency shifts. The differences between the two resonating frequencies and their shifts are discussed and analyzed, and a coefficientrelated to the two frequency shifts is confirmed.Micro-cantilever sensors for mass detection using resonance frequency have attracted considerable attention over the last decade in the field of gas sensing. For such a sensing system, an oscillator circuit loop is conventionally used to actuate the micro-cantilever, and trace the frequency shifts. In this paper, gas experiments are introduced to investigate the mechanical resonance frequency shifts of the micro-cantilever within the circuit loop(mechanical resonance frequency, MRF and resonating frequency shifts of the electric signal in the oscillator circuit (system working frequency, SWF. A silicon beam with a piezoelectric zinc oxide layer is employed in the experiment, and a Self-Actuating-Detecting (SAD circuit loop is built to drive the micro-cantilever and to follow the frequency shifts. The differences between the two resonating frequencies and their shifts are discussed and analyzed, and a coefficientrelated to the two frequency shifts is confirmed.
FORWARD MODELING OF PROPAGATING SLOW WAVES IN CORONAL LOOPS AND THEIR FREQUENCY-DEPENDENT DAMPING
Energy Technology Data Exchange (ETDEWEB)
Mandal, Sudip; Banerjee, Dipankar [Indian Institute of Astrophysics, Koramangala, Bangalore 560034 (India); Magyar, Norbert; Yuan, Ding; Doorsselaere, Tom Van, E-mail: sudip@iiap.res.in [Center for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, bus 2400, B-3001, Leuven (Belgium)
2016-03-20
Propagating slow waves in coronal loops exhibit a damping that depends upon the frequency of the waves. In this study we aim to investigate the relationship of the damping length (L{sub d}) with the frequency of the propagating wave. We present a 3D coronal loop model with uniform density and temperature and investigate the frequency-dependent damping mechanism for the four chosen wave periods. We include the thermal conduction to damp the waves as they propagate through the loop. The numerical model output has been forward modeled to generate synthetic images of SDO/AIA 171 and 193 Å channels. The use of forward modeling, which incorporates the atomic emission properties into the intensity images, allows us to directly compare our results with the real observations. The results show that the damping lengths vary linearly with the periods. We also measure the contributions of the emission properties on the damping lengths by using density values from the simulation. In addition to that we have also calculated the theoretical dependence of L{sub d} with wave periods and showed that it is consistent with the results we obtained from the numerical modeling and earlier observations.
Distributed acoustic sensing with Michelson interferometer demodulation
Liu, Xiaohui; Wang, Chen; Shang, Ying; Wang, Chang; Zhao, Wenan; Peng, Gangding; Wang, Hongzhong
2016-12-01
The distributed acoustic sensing (DAS) has been extensively studied and widely used. A distributed acoustic sensing system based on the unbalanced Michelson interferometer with phase generated carrier (PGC) demodulation was designed and tested. The system could directly obtain the phase, amplitude, frequency response, and location information of sound wave at the same time and measurement at all points along the sensing fiber simultaneously. Experiments showed that the system successfully measured the acoustic signals with a phase-pressure sensitivity about-148 dB (re rad/μPa) and frequency response ripple less than 1.5 dB. The further field experiment showed that the system could measure signals at all points along the sensing fiber simultaneously.
Distributed acoustic sensing with Michelson interferometer demodulation
Liu, Xiaohui; Wang, Chen; Shang, Ying; Wang, Chang; Zhao, Wenan; Peng, Gangding; Wang, Hongzhong
2017-09-01
The distributed acoustic sensing (DAS) has been extensively studied and widely used. A distributed acoustic sensing system based on the unbalanced Michelson interferometer with phase generated carrier (PGC) demodulation was designed and tested. The system could directly obtain the phase, amplitude, frequency response, and location information of sound wave at the same time and measurement at all points along the sensing fiber simultaneously. Experiments showed that the system successfully measured the acoustic signals with a phase-pressure sensitivity about-148 dB (re rad/μPa) and frequency response ripple less than 1.5 dB. The further field experiment showed that the system could measure signals at all points along the sensing fiber simultaneously.
Measurement of radial distortion based on frequency integration phase demodulation%应用频率积分相位解调测量径向畸变
Institute of Scientific and Technical Information of China (English)
杨初平; 刘建斌; 谭穗妍; 翁嘉文
2014-01-01
为了测量光学成像系统的径向畸变，采用载频条纹模板，应用瞬时频率积分法提取因径向畸变而产生的径向调制相位；推导了条纹径向调制相位与瞬时频率的关系式，并导出径向调制相位和径向畸变位移关系；采用小波频率估计提取畸变条纹径向瞬时频率，并对其进行积分获得畸变条纹的径向调制相位；应用径向调制相位和立方卷积插值算法对畸变图像进行了校正，得出了详细的理论分析和实验结果。结果表明，上述方法是可行的。%To measure the radial distortion in optical imaging systems , adopting the straight sinusoidal carrier-fringe pattern, the radial modulated phase resulting from radial distortion was extracted by means of instantaneous frequency integration .The formula between the instantaneous frequency and the radial modulated phase was deduced , and the conversion formula between the radial modulated phase and the radial distortion displacement was obtained . The instantaneous frequency of the distorted fringe pattern in the radial direction was calculated by using frequency estimation of Gabor wavelet transform , and integrated to obtain the radial modulated phase .The radial modulated phase and the cubic convolution interpolation algorithm were used to calibrate the distorted image .Experimental results demonstrate that the method is available .
Planetary Gearbox Fault Diagnosis Using Envelope Manifold Demodulation
Directory of Open Access Journals (Sweden)
Weigang Wen
2016-01-01
Full Text Available The important issue in planetary gear fault diagnosis is to extract the dependable fault characteristics from the noisy vibration signal of planetary gearbox. To address this critical problem, an envelope manifold demodulation method is proposed for planetary gear fault detection in the paper. This method combines complex wavelet, manifold learning, and frequency spectrogram to implement planetary gear fault characteristic extraction. The vibration signal of planetary gear is demodulated by wavelet enveloping. The envelope energy is adopted as an indicator to select meshing frequency band. Manifold learning is utilized to reduce the effect of noise within meshing frequency band. The fault characteristic frequency of the planetary gear is shown by spectrogram. The planetary gearbox model and test rig are established and experiments with planet gear faults are conducted for verification. All results of experiment analysis demonstrate its effectiveness and reliability.
Wieserman, W. R.; Schwarze, G. E.; Niedra, J. M.
1990-01-01
Limited experimental data exists for the specific core loss and dynamic B-H loops for soft magnetic materials for the combined conditions of high frequency and high temperature. This experimental study investigates the specific core loss and dynamic B-H loop characteristics of Supermalloy and Metglas 2605SC over the frequency range of 1 to 50 kHz and temperature range of 23 to 300 C under sinusoidal voltage excitation. The experimental setup used to conduct the investigation is described. The effects of the maximum magnetic flux density, frequency, and temperature on the specific core loss and on the size and shape of the B-H loops are examined.
2016-10-01
ARL-TR-7860 ● OCT 2016 US Army Research Laboratory Design and Calibration of the US Army Research Laboratory (ARL) Closed Loop...ARL-TR-7860 ● OCT 2016 US Army Research Laboratory Design and Calibration of the US Army Research Laboratory (ARL) Closed Loop Laboratory... Design and Calibration of the US Army Research Laboratory (ARL) Closed Loop Laboratory Radio Frequency (RF) Propagation Section 5a. CONTRACT NUMBER
Greenhall, C. A.
1996-01-01
The phase of a frequency standard that uses periodic interrogation and control of a local oscillator (LO) is degraded by a long-term random-walk component induced by downconversion of LO noise into the loop passband. The Dick formula for the noise level of this degradation is derived from an explicit solution of an LO control-loop model.
Error propagation in polarimetric demodulation
Ramos, A Asensio
2008-01-01
The polarization analysis of the light is typically carried out using modulation schemes. The light of unknown polarization state is passed through a set of known modulation optics and a detector is used to measure the total intensity passing the system. The modulation optics is modified several times and, with the aid of such several measurements, the unknown polarization state of the light can be inferred. How to find the optimal demodulation process has been investigated in the past. However, since the modulation matrix has to be measured for a given instrument and the optical elements can present problems of repeatability, some uncertainty is present in the elements of the modulation matrix and/or covariances between these elements. We analyze in detail this issue, presenting analytical formulae for calculating the covariance matrix produced by the propagation of such uncertainties on the demodulation matrix, on the inferred Stokes parameters and on the efficiency of the modulation process. We demonstrate...
Directory of Open Access Journals (Sweden)
ARUN, K.
2016-05-01
Full Text Available A modified digital signal processing procedure is described for the on-line estimation of DC, fundamental and harmonics of periodic signal. A frequency locked loop (FLL incorporated within the parallel structure of observers is proposed to accommodate a wide range of frequency drift. The error in frequency generated under drifting frequencies has been used for changing the sampling frequency of the composite observer, so that the number of samples per cycle of the periodic waveform remains constant. A standard coupled oscillator with automatic gain control is used as numerically controlled oscillator (NCO to generate the enabling pulses for the digital observer. The NCO gives an integer multiple of the fundamental frequency making it suitable for power quality applications. Another observer with DC and second harmonic blocks in the feedback path act as filter and reduces the double frequency content. A systematic study of the FLL is done and a method has been proposed to design the controller. The performance of FLL is validated through simulation and experimental studies. To illustrate applications of the new FLL, estimation of individual harmonics from nonlinear load and the design of a variable sampling resonant controller, for a single phase grid-connected inverter have been presented.
Constant frequency pulsed phase-locked-loop instrument for measurement of ultrasonic velocity
Energy Technology Data Exchange (ETDEWEB)
Yost, William T; Cantrell, John H; Kushnick, Peter W
1991-10-01
A new instrument based on a constant frequency pulsed phase-locked-loop (CFPPLL) concept has been developed to accurately measure the ultrasonicwavevelocity in liquids and changes in ultrasonicwavevelocity in solids and liquids. An analysis of the system shows that it is immune to many of the frequency-dependent effects that plague other techniques including the constant phase shifts of reflectors placed in the path of the ultrasonicwave.Measurements of the sound velocity in ultrapure water are used to confirm the analysis. The results are in excellent agreement with values from the literature, and establish that the CFPPLL provides a reliable, accurate way to measurevelocities, as well as for monitoring small changes in velocity without the sensitivity to frequency-dependent phase shifts common to other measurement systems. The estimated sensitivity to phase changes is better than a few parts in 10{sup 7}.
Constant frequency pulsed phase-locked-loop instrument for measurement of ultrasonic velocity
Yost, William T.; Cantrell, John H.; Kushnick, Peter W.
1991-10-01
A new instrument based on a constant-frequency pulsed phase-locked-loop (CFPPLL) concept has been developed to accurately measure the ultrasonic wave velocity in liquids and changes in ultrasonic wave velocity in solids and liquids. An analysis of the system shows that it is immune to many of the frequency-dependent effects that plague other techniques. Measurements of the sound velocity in ultrapure water are used to confirm the analysis. The results are in excellent agreement with values from the literature, and establish that the CFPPLL provides a reliable, accurate way to measure velocities, as well as for monitoring small changes in velocity without the sensitivity to frequency-dependent phase shifts common to other measurement systems. The estimated sensitivity to phase changes is better than a few parts in 10 to the 7th.
360-degrees profilometry using strip-light projection coupled to Fourier phase-demodulation.
Servin, Manuel; Padilla, Moises; Garnica, Guillermo
2016-01-11
360 degrees (360°) digitalization of three dimensional (3D) solids using a projected light-strip is a well-established technique in academic and commercial profilometers. These profilometers project a light-strip over the digitizing solid while the solid is rotated a full revolution or 360-degrees. Then, a computer program typically extracts the centroid of this light-strip, and by triangulation one obtains the shape of the solid. Here instead of using intensity-based light-strip centroid estimation, we propose to use Fourier phase-demodulation for 360° solid digitalization. The advantage of Fourier demodulation over strip-centroid estimation is that the accuracy of phase-demodulation linearly-increases with the fringe density, while in strip-light the centroid-estimation errors are independent. Here we proposed first to construct a carrier-frequency fringe-pattern by closely adding the individual light-strip images recorded while the solid is being rotated. Next, this high-density fringe-pattern is phase-demodulated using the standard Fourier technique. To test the feasibility of this Fourier demodulation approach, we have digitized two solids with increasing topographic complexity: a Rubik's cube and a plastic model of a human-skull. According to our results, phase demodulation based on the Fourier technique is less noisy than triangulation based on centroid light-strip estimation. Moreover, Fourier demodulation also provides the amplitude of the analytic signal which is a valuable information for the visualization of surface details.
Hardware-in-the-loop (HIL) Test of Demand as Frequency Controlled Reserve (DFR)
DEFF Research Database (Denmark)
Wu, Qiuwei; Zimmermann, K.; Østergaard, Jacob
2016-01-01
This paper presents the hardware-in-the-loop (HIL) test of the demand as frequency controlled reserve (DFR). The HIL test refers to a test in which parts of a pure simulation have been replaced by actual physical components. It is used to understand the behavior of a new device or controller....... The DFR has been tested by offline simulations to illustrate the efficacy of this technology. The DFR control logics have been implemented in the SmartBox. The HIL was conducted by having the SmartBox connected to the real time simulations and the performance of the SmartBox was tested with difference...
All-Digital Phase Locked Loop (ADPLL -A Review
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Neelu Jain
2013-01-01
Full Text Available The All-Digital Phase-Locked Loop (ADPLL is digital electronic circuit that are used in modern electronic communication systems like frequency synthesizer, modulator/demodulator etc. This paper presents a review of various ADPLL techniques. The range of input frequency of ADPLL is 40 to 98 MHz; the output frequency may be up to 2.92 to 4 GHz range. The components of ADPLL such as phase detector, loop filter, Voltage Controlled Oscillator have been discussed in detail. Various problems in Digital PLL like noise, leakage, parasitic element etc. can be removed with the help of All-Digital PLL. Various parameters of ADPLL like power consumption, jitter, input and output frequency have also been compared. Now a days, processors using ADPLL having frequency in GHz range are being used in mobile communication to increase the speed of the system.
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).
Simulation and Measurement of Medium-Frequency Signals Coupling From a Line to a Loop Antenna
Damiano, Nicholas W.; Li, Jingcheng; Zhou, Chenming; Brocker, Donovan E.; Qin, Yifeng; Werner, Douglas H.; Werner, Pingjuan L.
2016-01-01
The underground-mining environment can affect radio-signal propagation in various ways. Understanding these effects is especially critical in evaluating communications systems used during normal mining operations and during mine emergencies. One of these types of communications systems relies on medium-frequency (MF) radio frequencies. This paper presents the simulation and measurement results of recent National Institute for Occupational Safety and Health (NIOSH) research aimed at investigating MF coupling between a transmission line (TL) and a loop antenna in an underground coal mine. Two different types of measurements were completed: 1) line-current distribution and 2) line-to-antenna coupling. Measurements were taken underground in an experimental coal mine and on a specially designed surface test area. The results of these tests are characterized by current along a TL and voltage induced in the loop from a line. This paper concludes with a discussion of issues for MF TLs. These include electromagnetic fields at the ends of the TL, connection of the ends of the TL, the effect of other conductors underground, and the proximity of coal or earth. These results could help operators by providing examples of these challenges that may be experienced underground and a method by which to measure voltage induced by a line. PMID:27784954
A constant loop bandwidth fractional-N frequency synthesizer for GNSS receivers
Institute of Scientific and Technical Information of China (English)
Yin Xizhen; Xiao Shimao; Jin Yuhua; Wu Qiwu; Ma Chengyan; Ye Tianchun
2012-01-01
A constant loop bandwidth fractional-N frequency synthesizer for portable civilian global navigation satellite system (GNSS) receivers implemented in a 130 nm 1P6M CMOS process is introduced.Via discrete working regions,the LC-VCO obtains a wide tuning range with a simple structure and small VCO gain.Spur suppression technology is proposed to minimize the phase offset introduced by PFD and charge pumps.The optimized bandwidth is maintained by an auto loop calibration module to adjust the charge pump current when the PLL output frequency changes or the temperature varies.Measurement results show that this synthesizer attains an in-band phase noise lower than -93 dBc at a 10 kHz offset and a spur less than -70 dBc; the bandwidth varies by ± 3％ for all the GNSS signals.The whole synthesizer consumes 4.5 mA current from a 1 V supply,and its area (without the LO tested buffer) is 0.5 mm2.
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...
Greenhall, Charles A.
1996-01-01
The phase of a frequency standard that uses periodic interrogation and control of a local oscillator (LO) is degraded by a long-term random-walk component induced by downconversion of LO noise into the loop passband. The Dick formula for the noise level of this degradation can be derived from explicit solotions of two LO control-loop models. A summary of the derivations is given here.
Virtual unit delay for digital frequency adaptive T/4 delay phase-locked loop system
DEFF Research Database (Denmark)
Yang, Yongheng; Zhou, Keliang; Blaabjerg, Frede
2016-01-01
-controller/processor with a fixed sampling rate considering the cost and complexity, where the number of unit delays that have been adopted should be an integer. For instance, in conventional digital control systems, a single-phase T/4 Delay Phase-Locked Loop (PLL) system takes 50 unit delays (i.e., in a 50-Hz system...... Delay PLL system should be done in its implementation. This process will result in performance degradation in the digital control system, as the exactly required number of delays is not realized. Hence, in this paper, a Virtual Unit Delay (VUD) has been proposed to address such challenges to the digital...... T/4 Delay PLL system. The proposed VUD adopts linear interpolation polynomial to approximate the fractional delay induced by the varying grid frequency in such a way that the control performance is enhanced. The proposed VUD has been demonstrated on a digitally controlled T/4 Delay PLL system...
Analysis of Middle Frequency Resonance in DFIG System Considering Phase Locked Loop
DEFF Research Database (Denmark)
Song, Yipeng; Blaabjerg, Frede
2017-01-01
compensated weak network. Besides these two resonances, a Middle Frequency Resonance (MFR) between 200 Hz and 800 Hz may appear when the Phase Locked Loop (PLL) with fast control dynamics is applied. In order to analyze the MFR, the DFIG system impedance considering the PLL is studied based on the Vector...... Oriented Control (VOC) strategy in Rotor Side Converter (RSC) and Grid Side Converter (GSC). On the basis of the established impedance modeling of the DFIG system, it is found that the PLL with fast control dynamics may result in the occurrence of MFR due to a decreasing phase margin. The simulation...... results of both a 7.5 kW small scale DFIG system and a 2 MW large scale DFIG system are provided to validate the theoretical analysis of the MFR....
Directory of Open Access Journals (Sweden)
Jorge Torres Gómez
2016-04-01
Full Text Available The current article addresses digital implementation of new demodulation schemes for Binary Frequency Shift Keying (BFSK, and has two main objectives: of the description of the performance of the new processing method and its implementation on FPGA technology. Performance is analyzed by means of the total number of demodulated bits free of errors without noise, and by means of the BER parameter. The proposed method exhibits to have better performance than the solutions reported. Additionally, the solution obtained shows lower complexity than reported methods in regard to the total number of adders and multipliers. The implementation is described for FPGA systems, and the System Generator software is used for testing and simulating the results.
Directory of Open Access Journals (Sweden)
Atika Arshad
2015-05-01
Full Text Available The promising development of magnetic sensors in biomedical field demands an appropriate level of understanding of the magnetic properties of the materials used in their fabrication. To date only few of the types of magnetic materials are encountered where their magnetic properties, characterization techniques and magnetization behavior are yet to be explored more suitably in the light of their applications. This research work studies the characterization of materials by using a cost effective and simple circuit consisting of inductive transducer and an OP-AMP as a voltage integrator. In this approach the circuit was simulated using PSPICE and experiments have been conducted to achieve the desired results. The simulation and experimental results are obtained for three test materials namely iron, steel and plastic. The novelty lies in applying the simple circuit for material testing and characterization via obtaining simulation results and validating these results through experiment. The magnetic properties in low external magnetic field are studied with materials under test. The magnetization effect of a magneto-inductive sensor is detected in low frequency range for different magnetic core materials. The results have shown magnetization behaviour of magnetic materials due to the variation of permeability and magnetism. The resulted hysteresis loops appeared to have different shapes for different materials. The magnetic hysteresis loop found for iron core demonstrated a bigger coercive force and larger reversals of magnetism than these of steel core, thus obtaining its magnetic saturation at a larger magnetic field strength. The shape of the hysteresis loop itself is found to be varying upon the nature of the material in use. The resulted magnetization behaviors of the materials proved their possible applicability for use in sensing devices. The key concern of this work is found upon selecting the appropriate magnetic materials at the desired
DSP-based non-coherent dual detector demodulator for land mobile radio channels
Saulnier, Gary J.; Rafferty, William
1986-01-01
This paper outlines the development of a digital demodulator suitable for the non-coherent detection of various modulation formats including: Phase Shift Keying (PSK), Continuous Phase Frequency Shift Keying (CPFSK) and Frequency Modulation (FM). The demodulator design concept has been derived with a view towards a single integrated circuit (IC) implementation. Two detectors, one non-coherent and one differentially coherent, operate concurrently, providing data detection and automatic frequency control (AFC). Bit error rate results are provided which illustrate the receiver performance in white Gaussian noise.
Low Power Phase Locked Loop Frequency Synthesizer for 2.4 GHz Band Zigbee
Directory of Open Access Journals (Sweden)
Nesreen M.H. Ismail
2009-01-01
Full Text Available Problem statement: Wireless communication systems are required for many applications. There are different standards for these systems. IEEE 802.15.4 defines the communication system standard for zigbee. This study discussed designing one of the blocks of zigbee transceiver which is the Phase Locked Loop (PLL. A major target for any communication systems is saving battery power, especially for zigbee as it is meant to be a low cost communication system. Phase Locked Loop is responsible on carrier frequency selection in a communication system. It is the most power consumer block in the transceiver as well. The objective of this study was designing a low power fully integrated integer-N PLL frequency synthesizer targeting the 2.4 GHz band IEEE 802.15.4 Std zigbee. Approach: Minimizing total power consumption of PLL was achieved by introducing a novel design of Phase Frequency Detector (PFD and modifying the rest of the PLL blocks. The proposed PFD uses only 12 transistors and it preserved the main characteristics of the conventional PFD with a simple architecture. The Charge Pump (CP was single-ended source switch to save power and minimize mismatches. The Voltage Controlled Oscillator (VCO spans from 4.737-4.977 GHz band using LC resonator. The VCO worked at double the frequency band to avoid local oscillator leakage and feed through. The integer N divider used a 15/16 dual modulus. Results: The proposed PLL was designed using Silterra 0.18 um CMOS process. It consumed 3.2 mW with 1.8 voltage supply. Phase noise is-113.4 dBc Hz-1 at 1 MHz. The proposed PFD works up to 2.5 GHz with free dead zone. The Charge Pump (CP works with 20 uA. lock-in time is 25 us and total die area is 1×2 mm. All results were taken from extracted layout simulations. Conclusion: The results of this study indicated that a PLL can work with less power consumption and save the transceiver battery. The proposed PFD was suitable for high speed applications.
EXPERIMENTAL COMPARISON OF HOMODYNE DEMODULATION ALGORITHMS FOR PHASE FIBER-OPTIC SENSOR
Directory of Open Access Journals (Sweden)
M. N. Belikin
2015-11-01
Full Text Available Subject of Research. The paper presents the results of experimental comparative analysis of homodyne demodulation algorithms based on differential cross multiplying method and on arctangent method under the same conditions. The dependencies of parameters for the output signals on the optical radiation intensity are studied for the considered demodulation algorithms. Method. The prototype of single fiber optic phase interferometric sensor has been used for experimental comparison of signal demodulation algorithms. Main Results. We have found that homodyne demodulation based on arctangent method provides greater (by 7 dB at average signal-to-noise ratio of output signals over the frequency band of acoustic impact from 100 Hz to 500 Hz as compared to differential cross multiplying algorithms. We have demonstrated that no change in the output signal amplitude occurs for the studied range of values of the optical pulses amplitudes. Obtained results indicate that the homodyne demodulation based on arctangent method is most suitable for application in the phase fiber-optic sensors. It provides higher repeatability of their characteristics than the differential cross multiplying algorithm. Practical Significance. Algorithms of interferometric signals demodulation are widely used in phase fiber-optic sensors. Improvement of their characteristics has a positive effect on the performance of such sensors.
A novel demodulator/detector for digital and analog signals on LMR channels
Saulnier, Gary J.; Rafferty, William
1990-01-01
The design, implementation, and performance of an all-digital demodulator/detector suitable for differentially encoded phase-shift keying (DPSK), continuous-phase frequency-shift keying (CPFSK), frequency-shift keying (FSK), and analog FM are discussed. In this demodulator/detector, two detectors, one noncoherent and another differentially coherent, operate simultaneously to provide data detection and automatic frequency control (AFC). Test results indicate that the system provides improved performance over the conventional analog quadrature detector for two-period raised-cosine (2RC) CPFSK modulation in additive white Gaussian noise (AWGN) and Rayleigh fading channels. Being all-digital, the demodulator/detector is well suited for integrated circuit implementation. In addition, the system performs as well as the analog quadrature detector for analog FM voice transmissions, thereby maintaining full compatibility with analog land mobile radio (LMR) transmissions.
FSD-HSO Optimization Algorithm for Closed Fringes Interferogram Demodulation
Directory of Open Access Journals (Sweden)
Ulises H. Rodriguez-Marmolejo
2016-01-01
Full Text Available Due to the physical nature of the interference phenomenon, extracting the phase of an interferogram is a known sinusoidal modulation problem. In order to solve this problem, a new hybrid mathematical optimization model for phase extraction is established. The combination of frequency guide sequential demodulation and harmony search optimization algorithms is used for demodulating closed fringes patterns in order to find the phase of interferogram applications. The proposed algorithm is tested in four sets of different synthetic interferograms, finding a range of average relative error in phase reconstructions of 0.14–0.39 rad. For reference, experimental results are compared with the genetic algorithm optimization technique, obtaining a reduction in the error up to 0.1448 rad. Finally, the proposed algorithm is compared with a very known demodulation algorithm, using a real interferogram, obtaining a relative error of 1.561 rad. Results are shown in patterns with complex fringes distribution.
Abedini, A
2016-01-01
Longitudinal intensity oscillations along coronal loops that are interpreted as signatures of magneto-acoustic waves are observed frequently in different coronal structures. The aim of this paper is to estimate the physical parameters of the slow waves and the quantitative dependence of these parameters on their frequencies in the solar corona loops that are situated above active regions with the Atmospheric Imaging Assembly (AIA) onboard Solar Dynamic Observatory (SDO). The observed data on 2012-Feb-12, consisting of 300 images with an interval of 24 seconds in the 171 $\\rm{\\AA}$ and 193 $\\rm{\\AA}$ passbands is analyzed for evidence of propagating features as slow waves along the loop structures. Signatures of longitudinal intensity oscillations that are damped rapidly as they travel along the loop structures were found, with periods in the range of a few minutes to few tens of minutes. Also, the projected (apparent) phase speeds, projected damping lengths, damping times and damping qualities of filtered int...
High Frequency Amplitude Detector for GMI Magnetic Sensors
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Aktham Asfour
2014-12-01
Full Text Available A new concept of a high-frequency amplitude detector and demodulator for Giant-Magneto-Impedance (GMI sensors is presented. This concept combines a half wave rectifier, with outstanding capabilities and high speed, and a feedback approach that ensures the amplitude detection with easily adjustable gain. The developed detector is capable of measuring high-frequency and very low amplitude signals without the use of diode-based active rectifiers or analog multipliers. The performances of this detector are addressed throughout the paper. The full circuitry of the design is given, together with a comprehensive theoretical study of the concept and experimental validation. The detector has been used for the amplitude measurement of both single frequency and pulsed signals and for the demodulation of amplitude-modulated signals. It has also been successfully integrated in a GMI sensor prototype. Magnetic field and electrical current measurements in open- and closed-loop of this sensor have also been conducted.
Khodachenko, M. L.; Zaitsev, V. V.; Kislyakov, A. G.; Rucker, H. O.; Urpo, S.
2005-04-01
Low-frequency (LF) modulations of 37GHz microwave radiation during solar flares, recorded at the Metsähovi Radio Observatory, are considered. A fast Fourier transformation with a sliding window is used to obtain the dynamic spectra of the LF pulsations. We pay attention to the LFdynamic spectra having a specific multi-track structure, which is supposed to be an indication of a complex multi-loop composition of a flaring region. Application of the equivalent electric circuit models of the loops including the effects of electromagnetic inductive interaction in groups of slowly growing current-carrying magnetic loops allows us to explain and reproduce the main dynamical features of the observed LF modulation dynamic spectra. Each loop is considered as an equivalent electric circuit with variable parameters (resistance, capacitance and inductive coefficients) which depend on shape, scale, position of the loop with respect to other loops, as well as on the plasma parameters and value of the total longitudinal current in the magnetic tube.
The Rolling Bearing Fault Feature Extraction Based on the LMD and Envelope Demodulation
Directory of Open Access Journals (Sweden)
Jun Ma
2015-01-01
Full Text Available Since the working process of rolling bearings is a complex and nonstationary dynamic process, the common time and frequency characteristics of vibration signals are submerged in the noise. Thus, it is the key of fault diagnosis to extract the fault feature from vibration signal. Therefore, a fault feature extraction method for the rolling bearing based on the local mean decomposition (LMD and envelope demodulation is proposed. Firstly, decompose the original vibration signal by LMD to get a series of production functions (PFs. Then dispose the envelope demodulation analysis on PF component. Finally, perform Fourier Transform on the demodulation signals and judge failure condition according to the dominant frequency of the spectrum. The results show that the proposed method can correctly extract the fault characteristics to diagnose faults.
Study on digital correlation demodulation technology of micro quartz tuning fork gyroscope
Zhang, Zhixiong; Feng, Lihui; Sun, Yu-Nan
2010-11-01
A signal demodulation scheme for micro quartz tuning fork gyroscope based on digital correlation demodulation technology is proposed. In the operation of quartz gyroscope the reference signal should be in the resonance state with steady amplitude and the reference signal should be in-phase and has the same frequency with the driving signal. The quartz gyroscope signal processing platform is designed on the foundation of DEC6713 DSP development board successfully. The adaptive algorithm including the reference signal frequency tacking, the amplitude automatic gain controlling, the reference signal phase locking, and complex correlation demodulation are devised, and the algorithm is programmed. It is proved that the digital signal process scheme is feasible by means of experimentation.
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.
Energy Technology Data Exchange (ETDEWEB)
Butta, M.; Ripka, P. [Department of Measurement, Faculty of Electrical Engineering, Czech Technical University in Prague, Prague 16627 (Czech Republic); Infante, G.; Badini-Confalonieri, G. A.; Vazquez, M. [Instituto de Ciencia de Materiales de Madrid (CSIC), Campus de Cantoblanco, Madrid 28049 (Spain)
2009-08-15
A high-sensitivity ac hysteresis loop tracer has been developed to measure the low frequency hysteresis loop of soft magnetic materials. It has been applied successfully to characterize straight pieces of amorphous glass-covered microwires with metallic nucleus down to 1.5 {mu}m thick. Based on the electromagnetic induction law, the proposed design is extremely simple and exploits the capabilities of commercially available data acquisition cards together with digital signal processing in order to achieve high-sensitivity without the need of expensive analog equipment.
DEFF Research Database (Denmark)
Golestan, Saeed; Mousazadeh Mousavi, Seyyed-Yousef; Guerrero, Josep M.
2017-01-01
The implementation of a large number of single-phase phase-locked loops (PLLs) involves creating a fictitious quadrature signal. A popular approach for this purpose is using a second-order generalized integrator-based quadrature signal generator (SOGIQSG) because it results in an acceptable speed....../accuracy tradeoff. The SOGI-QSG based PLL (or briefly the SOGI-PLL), in its standard form, involves a frequency feedback loop for adjusting the SOGI resonance frequency under frequency drifts. Some recent research works have reported that the speed/accuracy tradeoff of the SOGI-PLL can be considerably enhanced......-based PLLs (FFSOGI-PLLs) to highlight their real advantages and disadvantages....
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.
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.
Feng, Zhipeng; Chen, Xiaowang; Wang, Tianyang
2017-07-01
Rolling bearings often work under variable speed conditions, resulting in nonstationary vibrations. How to effectively extract the time-varying fault frequency from nonstationary vibration signals is a key issue in rolling bearing fault diagnosis. To address this issue, a quality time-frequency analysis of excellent time-frequency readability and robust to noise is necessary. To this end, the concentration of frequency and time (ConceFT) method is exploited. Based on this time-frequency analysis method, and considering the modulation feature of rolling bearing vibrations, we propose joint time-varying amplitude and frequency demodulated spectra to reveal the time-varying fault characteristic frequency. Firstly, the optimal frequency band sensitive to rolling bearing fault is selected by spectral kurtosis. Then, both the amplitude envelope and instantaneous frequency of the sensitive signal component within the selected optimal frequency band are calculated. Next, the ConceFT method is applied to the amplitude envelope and instantaneous frequency to generate the time-varying amplitude and frequency demodulated spectra. Finally, rolling bearing fault can be diagnosed by analysis of the time-varying frequency revealed by the time-varying demodulated spectra. This method is free from complex time-varying sidebands, and is robust to noise interference. It is illustrated by numerical simulated signal analysis, and is further validated via lab experimental rolling bearing vibration signal analyses. The localized defects on both inner and outer race are successfully diagnosed.
Precise digital demodulation for fiber optic interferometer sensors
Medvedev, Andrei; Berezhnoi, Andrei; Kudryashov, Aleksei; Liokumovich, Leonid
2016-03-01
Different methods are used in the interferometer sensors for target signal extraction. Digital technologies provide new opportunities for precise signal detection. We have developed the principle of signal demodulation using an additional harmonic phase modulation and digital signal processing. The principle allows implementation of processing algorithms using different ratios between modulation and discretization frequencies. The expressions allowing calculation of the phase difference using the inverse trigonometric functions were derived. The method was realized in LabVIEW programming environment and was demonstrated for various signal shapes.
Multichannel demultiplexer/demodulator technologies for future satellite communication systems
Ivancic, William D.; Budinger, James M.; Staples, Edward J.; Abramovitz, Irwin; Courtois, Hector A.
1992-01-01
NASA-Lewis' Space Electronics Div. supports ongoing research in advanced satellite communication architectures, onboard processing, and technology development. Recent studies indicate that meshed VSAT (very small aperture terminal) satellite communication networks using FDMA (frequency division multiple access) uplinks and TDMA (time division multiplexed) downlinks are required to meet future communication needs. One of the critical advancements in such a satellite communication network is the multichannel demultiplexer/demodulator (MCDD). The progress is described which was made in MCDD development using either acousto-optical, optical, or digital technologies.
Digital Modulator and Demodulator IC for RFID Tag Employing DSSS and Barker Code
Directory of Open Access Journals (Sweden)
L. F. Rahman
2012-11-01
Full Text Available Radio frequency identification (RFID is lagging behind because of vendor specific solutions and expensiveimplementation cost. In particular, the reader is the most expensive part. A WiFi compatible tag was proposed to usethe WNIC as an RFID reader. However, no specific modulator or demodulator was suggested. This paper analyzesthe various IEEE 802.11 standards and their modulation and coding techniques keeping the desired properties of anRFID system in consideration. After the analysis, a digital modulator and demodulator for RFID tag in IEEE 802.11protocol employing Direct Sequence Spread-Spectrum (DSSS and coding is proposed. A MOD-11 synchronouscounter is designed for the 11-bit encoder which generates the desired Barker code. Data are multiplied with thisBarker code to modulate the data, and the received data are multiplied with the Barker code to demodulate them. Theproposed modulator and demodulator are implemented in 0.18μm CMOS technology. The simulation results showthat 1 bit is spread to 11 bits by the modulator and 11-bit received data are demodulated to 1 bit correctly. Theproposed design is simple, resistant to multipath fading and interference and offers the highest distance with thelowest BER for an RFID tag.
On-board multicarrier demodulator for mobile applications using DSP implementation
Yim, W. H.; Kwan, C. C. D.; Coakley, F. P.; Evans, B. G.
1990-11-01
This paper describes the design and implementation of an on-board multicarrier demodulator using commercial digital signal processors. This is for use in a mobile satellite communication system employing an up-link SCPC/FDMA scheme. Channels are separated by a flexible multistage digital filter bank followed by a channel multiplexed digital demodulator array. The cross/dot product design approach of error detector leads to a new QPSK frequency control algorithm that allows fast acquisition without special preamble pattern. Timing correction is performed digitally using an extended stack of polyphase sub-filters.
Wu, Qi; Okabe, Yoji
2015-02-01
Fiber Bragg grating (FBG) demodulated by an erbium fiber laser (EFL) has been used for ultrasonic detection recently. However, due to the inherent relaxation oscillation (RO) of the EFL, the detected ultrasonic signals have large deformations, especially in the low-frequency range. We proposed a novel data processing method to reconstruct an actual ultrasonic waveform. The noise spectrum was smoothed first; the actual ultrasonic spectrum was then obtained by deconvolution in order to mitigate the influence of the RO of the EFL. We proved by experiment that this waveform reconstruction method has high precision, and demonstrated that the FBG sensor demodulated by the EFL will have large practical applications in nondestructive testing.
Demodulation of diaphragm based acoustic sensor using Sagnac interferometer with stable phase bias.
Ma, Jun; Yu, Yongqin; Jin, Wei
2015-11-01
A stable phase demodulation system for diaphragm-based acoustic sensors is reported. The system is based on a modified fiber-optic Sagnac interferometer with a stable quadrature phase bias, which is independent of the parameters of the sensor head. The phase bias is achieved passively by introducing a nonreciprocal frequency shift between the counter-propagating waves, avoiding the use of complicated active servo-control. A 100 nm-thick graphite diaphragm-based acoustic sensor interrogated by the proposed demodulation system demonstrated a minimum detectable pressure level of ~450 µPa/Hz(1/2) and an output signal stability of less than 0.35 dB over an 8-hour period. The system may be useful as a universal phase demodulation unit for diaphragm-based acoustic sensors as well as other sensors operating in a reflection mode.
Research on the fault diagnosis of bearing based on wavelet and demodulation
Li, Jiapeng; Yuan, Yu
2017-05-01
As a most commonly-used machine part, antifriction bearing is extensively used in mechanical equipment. Vibration signal analysis is one of the methods to monitor and diagnose the running status of antifriction bearings. Therefore, using wavelet analysis for demising is of great importance in the engineering practice. This paper firstly presented the basic theory of wavelet analysis to study the transformation, decomposition and reconstruction of wavelet. In addition, edition software LabVIEW was adopted to conduct wavelet and demodulation upon the vibration signal of antifriction bearing collected. With the combination of Hilbert envelop demodulation analysis, the fault character frequencies of the demised signal were extracted to conduct fault diagnosis analysis, which serves as a reference for the wavelet and demodulation of the vibration signal in engineering practice.
On the Convergence Speed of Turbo Demodulation with Turbo Decoding
Haddad, Salim; Jezequel, Michel
2012-01-01
Iterative processing is widely adopted nowadays in modern wireless receivers for advanced channel codes like turbo and LDPC codes. Extension of this principle with an additional iterative feedback loop to the demapping function has proven to provide substantial error performance gain. However, the adoption of iterative demodulation with turbo decoding is constrained by the additional implied implementation complexity, heavily impacting latency and power consumption. In this paper, we analyze the convergence speed of these combined two iterative processes in order to determine the exact required number of iterations at each level. Extrinsic information transfer (EXIT) charts are used for a thorough analysis at different modulation orders and code rates. An original iteration scheduling is proposed reducing two demapping iterations with reasonable performance loss of less than 0.15 dB. Analyzing and normalizing the computational and memory access complexity, which directly impact latency and power consumption, ...
Directory of Open Access Journals (Sweden)
Songrong Luo
2015-01-01
Full Text Available When a local defect occurs in gearbox, the vibration signals present as the form of multicomponent amplitude modulation and frequency modulation (AM-FM. Demodulation analysis is an effective way for this kind of signal. A self-adaptive wavelet ridge demodulation method based on LCD is proposed in this paper. Firstly, multicomponent AM-FM signal is decomposed into series of intrinsic scale components (ISCs and the special intrinsic scale component is selected in order to decrease the lower frequency background noise. Secondly, the genetic algorithm is employed to optimize wavelet parameters according to the inherent characteristics of signal; thirdly, self-adaptive wavelet ridge demodulation wavelet for the selected ISC component is performed to get instantaneous amplitude (IA or instantaneous frequency (IF. Lastly, the characteristics frequency can be obtained to identify the working state or failure information from its spectrum. By two simulation signals, the proposed method was compared with various existing demodulation methods; the simulation results show that it has higher accuracy and higher noise tolerant performance than others. Furthermore, the proposed method was applied to incipient fault diagnosis for gearbox and the results show that it is simple and effective.
A UNIVERSAL ALGORITHM OF MODULATION AND DEMODULATION
Institute of Scientific and Technical Information of China (English)
Zhang Rui; Li Jiandong; Wu Jie
2002-01-01
A new universal algorithm of modulation and demodulation is presented to process most signals of digital phase-related modulation schemes such as M-DPSK, MSK and even some M-FSK with low modulation level. It can easily deal with modulation and demodulation of the signals with different modulation schemes and data rates by only setting a few input arguments of the versatile software modules. The computational complexity of the algorithm is far less than that of conventional methods. The average processing capacity of the algorithm is about 15instructions per symbol when processing DQPSK signals. It can be applied to software radios.
Open-loop frequency response analysis of a wind turbine using a high-order linear aeroelastic model
DEFF Research Database (Denmark)
Sønderby, Ivan Bergquist; Hansen, Morten Hartvig
2014-01-01
Wind turbine controllers are commonly designed on the basis of low-order linear models to capture the aeroelastic wind turbine response due to control actions and disturbances. This paper characterizes the aeroelastic wind turbine dynamics that influence the open-loop frequency response from gene......-minimum phase zeros below the frequency of the first drivetrain mode. To correctly predict the non-minimum phase zeros, it is essential to include lateral tower and blade flap degrees of freedom. Copyright © 2013 John Wiley & Sons, Ltd....
A linear coherent integrated receiver based on a broadband optical phase-locked loop
Ramaswamy, Anand
Optical Phase-Locked Loops (OPLL) have diverse applications in future communication systems. They can be used in high sensitivity homodyne phase-shift keying receivers for phase noise reduction, provided sufficient loop bandwidth is maintained. Alternative phase-locked loop applications include coherent synchronization of laser arrays and frequency synthesis by offset locking. In this work, a broadband OPLL based coherent receiver is used for linear phase demodulation. Phase modulated (PM) analog optical links have the potential to outperform conventional direct detection links. However, their progress has been stymied by the lack of a linear phase demodulator. We describe how feedback can be used to suppress non-linearities arising from the phase demodulation process. The receiver concept is demonstrated at low frequencies and is found to improve the Spurious Free Dynamic Range (SFDR) of an experimental analog link by over 20dB. In order to extend the operation of the receiver to microwave frequencies, latencies arising from physical delays in the feedback path need to be dramatically reduced. To facilitate this, monolithic and hybrid versions of the receiver based on compact integration of InP photonic integrated circuits (PIC) with InP and SiGe electronic integrated circuits (EIC) have been developed at UCSB. In this work, we develop novel measurement techniques to characterize the linearity of the individual components of the PIC, namely, the semiconductor photodiodes and optical phase modulators. We then demonstrate the operation of the receiver in a high power analog link. The OPLL based receiver has a bandwidth of 1.5GHz. The link gain and shot-noise limited SFDR at 300MHz are -2dB and 125dB-Hz2/3, respectively. Further, optical sampling downconversion is demonstrated as a viable technique to increase the operating frequency of the receiver beyond the baseband range.
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.
High Speed Wireless Signal Generation and Demodulation
DEFF Research Database (Denmark)
Caballero Jambrina, Antonio; Sambaraju, Rakesh; Zibar, Darko;
We present the experimental demonstration of high speed wireless generation, up to 40 Gb/s, in the 75-110 GHz wireless band. All-optical OFDM and photonic up-conversion are used for generation and single side-band modulation with digital coherent detection for demodulation....
Design of an All-Digital Synchronized Frequency Multiplier Based on a Dual-Loop (D/FLL Architecture
Directory of Open Access Journals (Sweden)
Maher Assaad
2012-01-01
Full Text Available This paper presents a new architecture for a synchronized frequency multiplier circuit. The proposed architecture is an all-digital dual-loop delay- and frequency-locked loops circuit, which has several advantages, namely, it does not have the jitter accumulation issue that is normally encountered in PLL and can be adapted easily for different FPGA families as well as implemented as an integrated circuit. Moreover, it can be used in supplying a clock reference for distributed digital processing systems as well as intra/interchip communication in system-on-chip (SoC. The proposed architecture is designed using the Verilog language and synthesized for the Altera DE2-70 development board. The experimental results validate the expected phase tracking as well as the synthesizing properties. For the measurement and validation purpose, an input reference signal in the range of 1.94–2.62 MHz was injected; the generated clock signal has a higher frequency, and it is in the range of 124.2–167.9 MHz with a frequency step (i.e., resolution of 0.168 MHz. The synthesized design requires 330 logic elements using the above Altera board.
Open-loop experiments of resonator micro-optic gyro
Institute of Scientific and Technical Information of China (English)
ZHANG Xu-lin; ZHOU Ke-jiang
2009-01-01
An open-loop resonator micro-optic gyro (R-MOG) with a 6 cm-long waveguide-type ring resonator is set up using the phase modulation spectroscopy technique. In the experiment, according to the test parameters of the resonator, the shot-noise-limited sensitivity is estimated to be 1.07×10-4 rad/s. From the test demodulation signal, the gyro dynamic range of ±7.0×103 rad/s is obtained. Using different phase modulation frequencies, the open-loop gyro output signal is observed when the equivalent gyro rotation is applied to the aconstic-optical modulators (AOMs). The sensitivity of the R-MOG can be increased by some countermeasures against system noise.
Sithamparanathan, Kandeepan; Piesiewicz, Radoslaw
In this paper we study and present some results on the performances of frequency tracking for Ka-band satellite communications in rain fading channels. The carrier frequency is tracked using a 2nd order hyperbolic phase detector based digital-phase locked loop (D-PLL). The hyperbolic D-PLL has the capability of extending the tracking range compared to the other D-PLL and hence can be designed such that to achieve low phase jitter performance for improved carrier tracking. We present the design and analysis of the D-PLL and show some simulation results on the frequency tracking performance for Ka-band rain fading channel. The results are compared with the non-fading noise only case and comparative analyses are made.
Yang, Yuan; Quan, Nannan; Bu, Jingjing; Li, Xueping; Yu, Ningmei
2016-09-26
High order modulation and demodulation technology can solve the frequency requirement between the wireless energy transmission and data communication. In order to achieve reliable wireless data communication based on high order modulation technology for visual prosthesis, this work proposed a Reed-Solomon (RS) error correcting code (ECC) circuit on the basis of differential amplitude and phase shift keying (DAPSK) soft demodulation. Firstly, recognizing the weakness of the traditional DAPSK soft demodulation algorithm based on division that is complex for hardware implementation, an improved phase soft demodulation algorithm for visual prosthesis to reduce the hardware complexity is put forward. Based on this new algorithm, an improved RS soft decoding method is hence proposed. In this new decoding method, the combination of Chase algorithm and hard decoding algorithms is used to achieve soft decoding. In order to meet the requirements of implantable visual prosthesis, the method to calculate reliability of symbol-level based on multiplication of bit reliability is derived, which reduces the testing vectors number of Chase algorithm. The proposed algorithms are verified by MATLAB simulation and FPGA experimental results. During MATLAB simulation, the biological channel attenuation property model is added into the ECC circuit. The data rate is 8 Mbps in the MATLAB simulation and FPGA experiments. MATLAB simulation results show that the improved phase soft demodulation algorithm proposed in this paper saves hardware resources without losing bit error rate (BER) performance. Compared with the traditional demodulation circuit, the coding gain of the ECC circuit has been improved by about 3 dB under the same BER of [Formula: see text]. The FPGA experimental results show that under the condition of data demodulation error with wireless coils 3 cm away, the system can correct it. The greater the distance, the higher the BER. Then we use a bit error rate analyzer to
Phase-locked-loop interferometry applied to aspheric testing with a computer-stored compensator.
Servin, M; Malacara, D; Rodriguez-Vera, R
1994-05-01
A recently developed technique for continuous-phase determination of interferograms with a digital phase-locked loop (PLL) is applied to the null testing of aspheres. Although this PLL demodulating scheme is also a synchronous or direct interferometric technique, the separate unwrapping process is not explicitly required. The unwrapping and the phase-detection processes are achieved simultaneously within the PLL. The proposed method uses a computer-generated holographic compensator. The holographic compensator does not need to be printed out by any means; it is calculated and used from the computer. This computer-stored compensator is used as the reference signal to phase demodulate a sample interferogram obtained from the asphere being tested. Consequently the demodulated phase contains information about the wave-front departures from the ideal computer-stored aspheric interferogram. Wave-front differences of ~ 1 λ are handled easily by the proposed PLL scheme. The maximum recorded frequency in the template's interferogram as well as in the sampled interferogram are assumed to be below the Nyquist frequency.
A wireless demodulation system for passive surface acoustic wave torque sensor
Ji, Xiaojun; Fan, Yanping; Qi, Hongli; Chen, Jing; Han, Tao; Cai, Ping
2014-12-01
Surface acoustic wave (SAW) resonators are utilized as torque sensors for their passive and wireless features. However, the response of a SAW torque sensor is difficult to detect because of the transient response duration and interruption of channel noise, which limit the application of SAW torque sensors. The sensitive mechanism and response function of a passive wireless SAW torque sensor are analyzed in this study. A novel demodulation system involving both hardware and software is developed for the SAW torque sensor. A clipping amplifier is utilized in the hardware to widen the dynamic response range and increase the length of the valid signal. Correlation extension and centroid algorithms are designed to lengthen the received signal and improve the estimation accuracy of the center frequency of the response signal, respectively. Meanwhile, a fast binary search algorithm is proposed to accelerate the scanning cycle according to the developed response function. Finally, the SAW torque sensor demodulation system is set up and SAW resonators with high sensitivity are fabricated on a quartz substrate. The presented demodulation system is tested, and a standard deviation of 0.28 kHz is achieved. This value is much smaller than that of classic and modern spectrum estimation methods. The sensitivity of resonance frequency shift versus torque on the shaft of the assembled senor is 2.03 kHz/Nm; the coefficient of determination is 0.999, and the linearity is 0.87%. Experimental results verify the validity and feasibility of the proposed SAW torque sensor demodulation system.
Energy Technology Data Exchange (ETDEWEB)
Liu, DongLin, E-mail: donglinliu@stu.xidian.edu.cn; Li, XiaoPing; Xie, Kai; Liu, ZhiWei [School of Aerospace Science and Technology, Xidian University, Xi' an 710071 (China)
2015-10-15
A high-speed vehicle flying through the atmosphere between 100 and 20 km may suffer from a “communication blackout.” In this paper, a low frequency system with an on-board loop antenna to receive signals is presented as a potential blackout mitigation method. Because the plasma sheath is in the near-field region of the loop antenna, the traditional scattering matrix method that is developed for the far-field region may overestimate the electromagnetic (EM) wave's attenuation. To estimate the EM wave's attenuation in the near-field region, EM interference (EMI) shielding theory is introduced. Experiments are conducted, and the results verify the EMI shielding theory's effectiveness. Simulations are also conducted with different plasma parameters, and the results obtained show that the EM wave's attenuation in the near-field region is far below than that in the far-field region. The EM wave's attenuation increases with the increase in electron density and decreases with the increase in collision frequency. The higher the frequency, the larger is the EM wave's attenuation. During the entire re-entry phase of a RAM-C module, the EM wave's attenuations are below 10 dB for EM waves with a frequency of 1 MHz and below 1 dB for EM waves with a frequency of 100 kHz. Therefore, the low frequency systems (e.g., Loran-C) may provide a way to transmit some key information to high-speed vehicles even during the communication “blackout” period.
Kudrin, Alexander V.; Ostafiychuk, Oleg M.; Zaboronkova, Tatyana M.
2017-08-01
Whistler wave radiation from a loop antenna located in a cylindrical duct with enhanced plasma density is considered in the case where the wave frequency is less than the lower hybrid frequency. Using the full-wave formulation, the total radiation resistance and the partial radiation resistances corresponding to guided eigenmodes of such a duct and unguided waves radiating to the background magnetoplasma are calculated and analyzed as functions of the plasma and source parameters. The emphasis is placed on the radiation characteristics of the considered source in the presence of an artificial near-antenna duct that can be created during active experiments in the ionosphere. Conditions are revealed under which the total radiation resistance is predominantly determined by the excitation of the eigenmodes of the duct. It is shown that the presence of an enhanced density duct can lead to a notable increase in the radiation resistance of a loop antenna in the discussed frequency range even if the duct is rather narrow and capable of guiding only a single low-order eigenmode. The results obtained can be helpful in understanding the basic features of excitation of the ducted whistlers and planning the related ionospheric and laboratory experiments.
Design, modeling, and analysis of multi-channel demultiplexer/demodulator
Lee, David D.; Woo, K. T.
1991-01-01
Traditionally, satellites have performed the function of a simple repeater. Newer data distribution satellite architectures, however, require demodulation of many frequency division multiplexed uplink channels by a single demultiplexer/demodulator unit, baseband processing and routing of individual voice/data circuits, and remodulation into time division multiplexed (TDM) downlink carriers. The TRW MCDD (Multichannel Demultiplexer/Multirate Demodulator) operates on a 37.4 MHz composite input signal. Individual channel data rates are either 64 Kbps or 2.048 Mbps. The wideband demultiplexer divides the input signal into 1.44 MHz segments containing either a single 2.048 Mbps channel or thirty two 64 Kbps channels. In the latter case, the narrowband demultiplexer further divides the single 1.44 MHz wideband channel into thirty two 45 KHz narrowband channels. With this approach the time domain Fast Fourier Transformation (FFT) channelizer processing capacity is matched well to the bandwidth and number of channels to be demultiplexed. By using a multirate demodulator fewer demodulators are required while achieving greater flexibility. Each demodulator can process a wideband channel or thirty two narrowband channels. Either all wideband channels, a mixture of wideband and narrowband channels, or all narrowband channels can be demodulated. The multirate demodulator approach also has lower nonrecurring costs since only one design and development effort is needed. TRW has developed a proof of concept (POC) model which fully demonstrates the signal processing fuctions of MCDD. It is capable of processing either three 2.048 Mbps channels or two 2.048 Mbps channels and thirty two 64 Kbps channels. An overview of important MCDD system engineering issues is presented as well as discussion on some of the Block Oriented System Simulation analyses performed for design verification and selection of operational parameters of the POC model. Systems engineering analysis of the POC
DEFF Research Database (Denmark)
Zibar, Darko; Sambaraju, Rakesh; Caballero Jambrina, Antonio
2011-01-01
We present a radio-frequency (RF) and bit-rate scalable technique for multigigabit wireless signal generation based on all-optical orthogonal frequency-division multiplexing (OFDM) and photonic up-conversion. Coherent detection supported by digital signal processing is used for signal demodulation...
Yingping, Chen; Zhiqian, Li
2015-05-01
A 5.0-V 2.0-A flyback power supply controller providing constant-voltage (CV) and constant-current (CC) output regulation without the use of an optical coupler is presented. Dual-close-loop control is proposed here due to its better regulation performance of tolerance over process and temperature compared with open loop control used in common. At the same time, the two modes, CC and CV, could switch to each other automatically and smoothly according to the output voltage level not sacrificing the regulation accuracy at the switching phase, which overcomes the drawback of the digital control scheme depending on a hysteresis comparator to change the mode. On-chip compensation using active capacitor multiplier technique is applied to stabilize the voltage loop, eliminate an additional package pin, and save on the die area. The system consumes as little as 100 mW at no-load condition without degrading the transient response performance by utilizing the adaptive switching frequency control mode. The proposed controller has been implemented in a commercial 0.35-μm 40-V BCD process, and the active chip area is 1.5 × 1.0 mm2. The total error of the output voltage due to line and load variations is less than ±1.7%.
Truszczynski, T
This thesis presents the author’s work during the internship at the European Laboratory for Particle Physics (CERN). The quadrature frequency converter is one of the modules that has been developed to upgrade the Proton Synchrotron RF system. Basic information about accelerators, fundamentals of IQ signal representation, mixing and phase shifting techniques are introduced. The development process of the converter is presented with the design details and measurements of the prototype board.
DEFF Research Database (Denmark)
Rodriguez, Pedro; Luna, Alvaro; Candela, Ignacio;
2011-01-01
This paper presents a new multiresonant frequency-adaptive synchronization method for grid-connected power converters that allows estimating not only the positive- and negative-sequence components of the power signal at the fundamental frequency but also other sequence components at other harmoni...
Directory of Open Access Journals (Sweden)
T. Musch
2003-01-01
Full Text Available The generation of analogue frequency ramps with non-fractional phase-locked-loops (PLL is a cost effective way of linearising varactor controlled oscillators (VCO. In case that the VCO shows a high phase-noise level, a single non-fractional PLL is not able to suppress the phase-noise of the VCO sufficiently. The reason for this is the limited loopbandwidth of the PLL. In the field of precise measurements a high phase-noise level is mostly not tolerable. Examples of VCO-types with an extremely high phase noise level are integrated millimetre wave oscillators based on GaAs-HEMT technology. Both, a low quality factor of the resonator and a high flicker-noise corner frequency of the transistors are the main reason for the poor phase-noise behaviour. On the other hand this oscillator type allows a cost effective implementation of a millimetre-wave VCO. Therefore, a cascaded two-loop structure is presented that is able to linearise a VCO and additionally to reduce its phase-noise significantly.
Directory of Open Access Journals (Sweden)
N. Belhaouchet
2008-03-01
Full Text Available Hysteresis current control is one of the simplest techniques used to control the magnitude and phase angle of motor current for motor drives systems. However, this technique presents several disadvantages such as operation at variable switching frequency which can reveal problems of filtering, interference between the phases in the case of the three-phase systems with insulated neutral connection or delta connection, and irregularity of the modulation pulses which especially causes an acoustic noise on the level of the machine for the high power drive. In this paper, a new technique is proposed for a variable-hysteresis-band controller based on dead beat control applied to three phase voltage source PWM inverters feeding AC motors. Its main aim is firstly ensure a constant switching frequency and secondly the synchronization of modulation pulses using the phase-locked-loop with loop gain compensation in order to ensure a better stability. The behavior of the proposed technique is verified by simulation.
VLSI digital demodulator co-processor
Stephen, Karen J.; Buznitsky, Mitchell A.; Lindsey, Mark J.
A demodulation coprocessor that incorporates into a single VLSI package a number of important arithmetic functions commonly encountered in demodulation processing is developed. The LD17 demodulator is designed for use in a digital modem as a companion to any of the commercially available digital signal processing (DSP) microprocessors. The LD17 includes an 8-b complex multiplier-accumulator (MAC), a programmable tone generator, a preintegrator, a dedicated noncoherent differential phase-shift keying (DPSK) calculator, and a program/data sequencer. By using a simple generic interface and small but powerful instruction set, the LD17 has the capability to operate in several architectural schemes with a minimum of glue logic. Speed, size, and power constraints will dictate which of these schemes is best for a particular application. The LD17 will be implemented in a 1.5-micron DLM CMOS gate array and packaged in an 84-pin JLCC. With the LD17 and its memory, the real-time processing compatibility of a typical DSP microprocessor can be extended to sampling rates from hundreds to thousands of kilosamples per second.
Li, Min; Xie, Fang; Ren, Junyu
2009-11-01
A fiber interferometric vibration measurement system which is based on demodulating the phase of a fiber Michelson interferometer which is made with a fiber 3dB-coupler is presented. In the work, the system employed the characteristics of fiber Brag gratings (FBGs) to interleave two fiber Michelson interferometers which share almost the same part of the main optical path. One of the fiber interferometers is used to stabilize the system, employing an electronic feedback loop to drive a piezoelectric actuator to tune the optical path of the reference beam in order to keep the interferometer in quadrature state. By this way, the low frequency drifts in the phase of the interferometric signals which are resulted from environmental disturbances are compensated for. The other one is used to perform the measurement task. By employing the characteristics of 3dB-coupler, the interferometric signals from the two outputs of the 3dB-couper are 180Âº out of phase. The two interferometric signals are input into an electronic processor and convert into currents, which are linear to the power of the optical interferometric light. The signals are collected by NI USB-5132 acquisition card and processed by a program in a personal computer. The measurement system is configured with fiber and fiber components which are integrated together. As the cutoff frequency of the feedback loop is 1.5Hz, the measurement system is capable of measuring vibration with frequencies bigger than 1.5Hz and the amplitude of the measured vibration is not limited.
Institute of Scientific and Technical Information of China (English)
雷能芳
2011-01-01
介绍了锁相环频率合成器的的组成及工作原理,并基于Simulink平台对双环锁相4倍频频率合成器进行了模型设计,仿真结果表明了设计的正确性及可行性.%The principle and the composition of Frequency Synthesizer Based on Phase-locked Loop is introduced, and the Simulink module of Fourth Frequency-Multiply Frequency synthesilzer with Double Phase-Lock Loops is designed. The correctness and feasibility of this design is verified by simulation result.
Reduction of AM-induced penalty in DPSK receivers by sum-square demodulation
DEFF Research Database (Denmark)
Nielsen, T. N.; Gliese, Ulrik Bo; Stubkjær, Kristian
1992-01-01
A DPSK (differential phase shift keying) demodulator which is insensitive to the amplitude modulation induced by semiconductor optical amplifier phase modulators is proposed. The demodulator consists of only two additional power dividers/combiners, compared to a traditional DPSK demodulator...
Designing All-Pole Filters for High-Frequency Phase-Locked Loops
Directory of Open Access Journals (Sweden)
Ricardo Bressan Pinheiro
2014-01-01
signals exchanged between the nodes of the networks and detected by PLLs. The necessity to improve clock precision that follows the bandwidth increase provoked the improvement of the filter component of the PLLs, avoiding instability and high-frequency components in the reference signals. Here, a technique of designing this kind of filter is presented, considering second-order filters, implying third-order PLLs. Simulations show that following this technique produces very fast tracking processes, enabling precise operation even for very high frequencies.
DEFF Research Database (Denmark)
Rodriguez, Pedro; Luna, Alvaro; Candela, Ignacio
2011-01-01
This paper presents a new multiresonant frequency-adaptive synchronization method for grid-connected power converters that allows estimating not only the positive- and negative-sequence components of the power signal at the fundamental frequency but also other sequence components at other harmonic......- and three-phase applications, deducing some key expressions regarding its stability and tuning. Moreover, the performance of the MSOGI-FLL is evaluated by both simulations and experiments to show its capability for detecting different harmonic components in a highly polluted grid scenario....
Sagnac interferometer based stable phase demodulation system for diaphragm based acoustic sensor
Ma, Jun; Yu, Yongqin; Jin, Wei
2015-07-01
A modified fiber-optic Sagnac interferometer with a stable π/2 phase bias is demonstrated for the demodulation of diaphragm-based acoustic sensors. The phase bias is obtained by introducing a nonreciprocal frequency shift between the counter-propagating waves. The system is passive and without complicated servo-control for phase stabilization. Interrogated by the proposed demodulation system, a 100 nm-thick graphite diaphragm-based acoustic sensor demonstrated a minimum detectable pressure level of ~ 450 μPa/Hz1/2 at the frequency of 5 kHz and the output signal stability is less than 0.35 dB over an 8-hour period.
Asymmetric propagation using enhanced self-demodulation in a chirped phononic crystal
Directory of Open Access Journals (Sweden)
A. Cebrecos
2016-12-01
Full Text Available Asymmetric propagation of acoustic waves is theoretically reported in a chirped phononic crystal made of the combination of two different nonlinear solids. The dispersion of the system is spatially dependent and allows the rainbow trapping inside the structure. Nonlinearity is used to activate the self-demodulation effect, which is enhanced due to the particular dispersion characteristics of the system. The performed numerical study reveals an efficient generation of the demodulated wave, up to 15% in terms of the pressure amplitude, as well as strong attenuation for undesired frequency components above the cut-off frequency. The obtained energy rectification ratio is in the order of 104 for the whole range of amplitudes employed in this work, indicating the robustness of the asymmetry and non-reciprocity of the proposed device for a wide operational range.
Analysis of Middle Frequency Resonance in DFIG System Considering Phase Locked Loop
DEFF Research Database (Denmark)
Song, Yipeng; Blaabjerg, Frede
2017-01-01
As the wind power technology develops, the Doubly Fed Induction Generator (DFIG) based wind power system, when connected to a weak network with large impedance, may suffer resonances, i.e., Sub- Synchronous Resonance (SSR) or High Frequency Resonance (HFR) when connected to the series or parallel...
Shi, Juanjuan; Liang, Ming; Guan, Yunpeng
2016-02-01
The conventional way for bearing fault diagnosis under variable rotational speed generally includes prefiltering, resampling based on shaft rotating frequency and order spectrum analysis. However, its application is confined by three major obstacles: a) knowledge-demanding parameter determination required by prefiltering, b) unavailable shaft rotating frequency for resampling as it is coupled with instantaneous fault characteristic frequency (IFCF) by a fault characteristic coefficient (FCC) which cannot be decided without knowing what fault actually exists, and c) complicated and error-prone resampling process. As such, we propose a new method to address these problems. The proposed method free from prefiltering and resampling mainly contains the following steps: a) extracting envelope by windowed fractal dimension (FD) transform, requiring no prefiltering, b) with the envelope signal, performing short time Fourier transform (STFT) to get a clear time frequency representation (TFR), from which the IFCF and the basic demodulator for generalized demodulation (GD) can be obtained, c) applying the generalized demodulation to the envelope signal with the current demodulator, converting the trajectory of the current time-frequency component into a linear path parallel to the time axis, d) frequency analyzing the demodulated signal, followed by searching the amplitude of the constant frequency where the linear path is situated. Updating demodulator via multiplying the basic demodulator by different real numbers (i.e., coefficient λ) and repeating the steps (c)-(d), the resampling-free order spectrum is then obtained. Based on the resulting spectrum, the final diagnosis decision can be made. The proposed method for its implementation on the example of simulated data is presented. Finally, experimental data are employed to validate the effectiveness of the proposed technique.
Firlej, M.; Fiutowski, T.; Idzik, M.; Moroń, J.; Świentek, K.
2015-12-01
The design and measurements results of a wide frequency range ultra-low power Phase-Locked Loop (PLL) for applications in readout systems of particle physics detectors are presented. The PLL was fabricated in a 130 nm CMOS technology. To allow the implementation of different data serialisation schemes multiple division factors (6, 8, 10, 16) were implemented in the PLL feedback loop. The main PLL block—VCO works in 16 frequency ranges/modes, switched either manually or automatically. A dedicated automatic frequency mode switching circuit was developed to allow simple frequency tuning. Although the PLL was designed and simulated for a frequency range of 30 MHz-3 GHz, due to the SLVS interface limits, the measurements were done only up to 1.3 GHz. The full PLL functionality was experimentally verified, confirming a very low and frequency scalable power consumption (0.7 mW at 1 GHz).
Yin, Mojuan; Huang, Shenghong; Lu, Baole; Chen, Haowei; Ren, Zhaoyu; Bai, Jintao
2013-09-20
A high-slope-efficiency single-frequency (SF) ytterbium-doped fiber laser, based on a Sagnac loop mirror filter (LMF), was demonstrated. It combined a simple linear cavity with a Sagnac LMF that acted as a narrow-bandwidth filter to select the longitudinal modes. And we introduced a polarization controller to restrain the spatial hole burning effect in the linear cavity. The system could operate at a stable SF oscillating at 1064 nm with the obtained maximum output power of 32 mW. The slope efficiency was found to be primarily dependent on the reflectivity of the fiber Bragg grating. The slope efficiency of multi-longitudinal modes was higher than 45%, and the highest slope efficiency of the single longitudinal mode we achieved was 33.8%. The power stability and spectrum stability were <2% and <0.1%, respectively, and the signal-to-noise ratio measured was around 60 dB.
Directory of Open Access Journals (Sweden)
A. L. Senyavskiy
2015-01-01
Full Text Available The article analyzes the robustness of the digital demodulator of the signal with the lowest frequency shift keying at a subcarrier frequency with respect to non-Gaussian interference type of atmospheric, industrial noise and interfering frequency -and phase-shift keyed signals. This type of demodulator is used for the transmission of navigation data in the systems of air traffic control with automatic dependent surveillance.
非协同突发信号的检测与解调%Detection and Demodulation of Burst Signal for Non-cooperative Communication
Institute of Scientific and Technical Information of China (English)
魏宇培; 梁先明; 廖龙灵
2015-01-01
According to the waveform protocol and frame structure of the Third Generation Maritime Satellite Communication,energy detection is combined with matching filter to realize burst signal detection,then fre-quency estimation and phase estimation is performed according to the result of signals detection. And then signal demodulation is realized through combining initialization phase estimation with phase locked loop ( PLL) . Both theoretical deduction and simulation indicate the method adapts to lower signal-to-noise ratio ( SNR) , higher frequency offset and bigger dynamic range. Signal detection probability approaches to 100 percent,and the demodulation bit error rate(BER) is under 2í10-3 when the Eb/N0 is above 10 dB.%根据典型的海事三代卫星通信帧格式，首先采用能量检测算法结合匹配滤波法进行有效的突发信号的检测，然后根据信号检测的结果进行了突发信号的频率估计和初相估计，再采用初相注入结合锁相环的方式实现突发信号的解调。理论推导和计算仿真表明，该方法能够适应较低信噪比、较大频偏和起伏动态的影响，当信噪比大于10 dB时，信号检测概率基本达到100%，解调误码率低于2×10-3。
Institute of Scientific and Technical Information of China (English)
Jun He; Fang Li; Hao Xiao; Yu-Liang Liu
2008-01-01
A novel fiber Bragg grating (FBG) sensor array system based on digital phase generated carrier (PGC) demodulation and reference compensation method is proposed and set up. Experimental results confirm that the digital PGC demodulation can be used for wavelength-division-multiplexed FBG sensor array and the reference compensation method can reduce the environmental interference by approximately 40 dB in the frequency range from 20 Hz to 2 kHz. The minimum detectable wavelength-shift of the sensor system is 1×10-3 pm/Hz1/2.
Alem, W. K.
1977-01-01
A modulation technique for a three-channel communication link is introduced. The structure of the modulator is such as to form an unbalanced quadriphase signal wherein the high rate data stream is bi-phase modulated on the in-phase carrier component, while the sum of the two lower rate signals is bi-phase modulated on the quadrature component of the same carrier. The sum of the two lower signals is, in turn, formed by modulating with the respective data streams the in-phase and the quadrature components of a square wave subcarrier. At the demodulator, the tracking of the carrier and the subcarrier is performed by two independent Costas loops. The demodulation of the high data rate signal is carried out after establishing the carrier reference signal, while the lower rate signals are demodulated after the subcarrier loop recovers the subcarrier. In this paper, the performance of the two loops is analyzed and the expressions for the tracking errors are derived. Finally, a numerical example pertaining to the Space Shuttle-to-TDRS Ku-band link is presented for illustration.
Energy Technology Data Exchange (ETDEWEB)
Garrison, Sean [Univ. of Missouri, Rolla, MO (United States)
2009-05-21
Engineers from a government-owned engineering and manufacturing facility were contracted by government-owned research laboratory to design and build an S-band telemetry transmitter using Radio Frequency Integrated Circuit (RFIC) technology packaged in a Low-Temperature Co-fired Ceramic (LTCC) Multi-Chip Module. The integrated circuit technology chosen for the Phase-Locked Loop Frequency Synthesizer portion of the telemetry transmitter was a 0.25 um CMOS process that utilizes a sapphire substrate and is fabricated by Peregrine Semiconductor corporation. This thesis work details the design of the Voltage Controlled Oscillator (VCO) portion of the PLL frequency synthesizer and constitutes an fully integrated VCO core circuit and a high-isolation buffer amplifier. The high-isolation buffer amplifier was designed to provide 16 dB of gain for 2200-3495 MHz as well as 60 dB of isolation for the oscillator core to provide immunity to frequency pulling due to RF load mismatch. Actual measurements of the amplifier gain and isolation showed the gain was approximately 5 dB lower than the simulated gain when all bond-wire and test substrate parasitics were taken into account. The isolation measurements were shown to be 28 dB at the high end of the frequency band but the measurement was more than likely compromised due to the aforementioned bond-wire and test substrate parasitics. The S-band oscillator discussed in this work was designed to operate over a frequency range of 2200 to 2300 MHz with a minimum output power of 0 dBm with a phase-noise of -92 dBc/Hz at a 100 kHz offset from the carrier. The tuning range was measured to be from 2215 MHz to 2330 MHz with a minimum output power of -7 dBm over the measured frequency range. A phase-noise of -90 dBc was measured at a 100 kHz offset from the carrier.
Measuring vibration by using fiber Bragg grating and demodulating it by blazed grating
Institute of Scientific and Technical Information of China (English)
Xiaojin Guo(郭晓金); Zongmin Yin(殷宗敏); Ning Song(宋宁)
2004-01-01
A method of measuring vibration by using fiber Bragg grating (FBG) and demodulating the spectrum by blazed grating is introduced. The sensor system is made of a simple supported beam with a FBG adhered to its upper surface. A blazed grating is used to demodulate the changing spectrum that is got from the sensor system, and a line charge-coupled device (CCD) is used to accept the diffraction spectrum.Through analyzing the number of the CCD's pixels, we can get the amplitude of vibration and the change of the temperature. The experimental results show that the vibration amplitude of the exciter matches the detected signal under the stable frequency. The temperature shift and vibration signal are also successfully separated.
Demodulation in tissue, the relevant parameters and the implications for limiting exposure.
Silny, Jiri
2007-06-01
In the biomedical literature there are a number of reports that speculate about possible effects in the body due to the demodulation of electromagnetic fields. However, only few interactions in amplitude-modulated or even pulse-modulated electromagnetic waves are fundamentally plausible and have been demonstrated to occur in humans. The following observations fall into this specific category: thermal effects of amplitude- or pulse-modulated microwaves; demodulation of amplitude- or pulse-modulated electromagnetic waves in cell membranes; and demodulation of amplitude- or pulse-modulated electromagnetic fields in the electronics of implants such as cardiac pacemakers or cardioverter defibrillators. The possible consequences of these effects for the organism, their probability of occurrence in everyday life field conditions, and, consequently, the implications for limiting exposure are very different. Microwave hearing is a harmless effect which is perceived by humans only in strong fields with high peak power densities of more than 100 mW cm(-2). In normal residential or occupational environments the peak power density of even the strongest microwave sources is only around 1 mW cm(-2). Demodulation of pulse-modulated electromagnetic fields in the cell membranes decreases the stimulation threshold of nerves and muscles and can introduce numerous adverse effects ranging from perception of pain to dangerous cardiac fibrillations. The stimulation and demodulation effects are restricted to carrier frequencies up to several MHz. In experiments with 900 and 1,800 MHz packets with lengths of up to 100 ms and applied powers of up to 100 W, neither a direct stimulation of superficial nerves and muscles nor the conditioning of an electrical current stimulus could be confirmed. Pulse-modulated electromagnetic waves are demodulated in the electronic circuits of implants and can inhibit cardiac pacemakers and introduce cardiac arrest in this way. The highest sensitivity results
Institute of Scientific and Technical Information of China (English)
薛青娜
2012-01-01
载波同步是相干解调通信系统中必不可少的组成部分,常用锁相环技术予以实现.System Generator是一款理想的FPGA开发软件,它提供了FPGA和simulink仿真软件的接口,可以把simulink中的模型自动转换成位流文件,以便下载到FPGA中,实现FPGA硬件设计的自动化.采用数字锁相环技术,在simulink中利用System Generator建立QPSK调制系统的模型,并仿真以验证锁相环技术的性能.仿真结果表明,通过合理设置参数,数字锁相环能很好地获取同频同相的载波分量,实现通信系统的正确解调.%Carrier synchronization technique is an essential component in coherent demodulation communication systems,which are typically implemented by PLL(Phase -Locked Loop). System Generator is an ideal FPGA development software,which provides interface for FPGA and simulink. The model can be automatically converted to bit - stream file in System Generator in order to download to FPGA, achieving the FPGA hardware design automation. In this paper, digital PLL technology is used to model a QPSK modulation system in simulink by System Generator and verify the PLL performance through the simulation. The results show that, digital PLL is an excellent technique to generate the local carrier with identical frequency and phase, and demodulate receiving signals correctly by setting reasonable parameters.
Advanced technology for a satellite multichannel demultiplexer/demodulator
Abramovitz, Irwin J.; Flechsig, Drew E.; Matteis, Richard M., Jr.
1994-01-01
Satellite on-board processing is needed to efficiently service multiple users while at the same time minimizing earth station complexity. The processing satellite receives a wideband uplink at 30 GHz and down-converts it to a suitable intermediate frequency. A multichannel demultiplexer then separates the composite signal into discrete channels. Each channel is then demodulated by bulk demodulators, with the baseband signals routed to the downlink processor for retransmission to the receiving earth stations. This type of processing circumvents many of the difficulties associated with traditional bent-pipe repeater satellites. Uplink signal distortion and interference are not retransmitted on the downlink. Downlink power can be allocated in accordance with user needs, independent of uplink transmissions. This allows the uplink users to employ different data rates as well as different modulation and coding schemes. In addition, all downlink users have a common frequency standard and symbol clock on the satellite, which is useful for network synchronization in time division multiple access schemes. The purpose of this program is to demonstrate the concept of an optically implemented multichannel demultiplexer (MCD). A proof-of-concept (POC) model has been developed which has the ability to receive a 40 MHz wide composite signal consisting of up to 1000 40 kHz QPSK modulated channels and perform the demultiplexing process. In addition a set of special test equipment (STE) has been configured to evaluate the performance of the POC model. The optical MCD is realized as an acousto-optic spectrum analyzer utilizing the capability of Bragg cells to perform the required channelization. These Bragg cells receive an optical input from a laser source and an RF input (the signal). The Bragg interaction causes optical output diffractions at angles proportional to the RF input frequency. These discrete diffractions are optically detected and output to individual demodulators for
A Fast π/4-DQPSK Demodulation Arithmetic and Realization
Institute of Scientific and Technical Information of China (English)
ZHOU Guo-yong; ZHONG Hong-sheng; WANG Jun-mei
2004-01-01
The modulated signals of π /4-DQPSK can be demodulated with the differenced method,and the technology has been used in the communication. The traditional demodulated method needs a lot of calculation. In this paper, a new method based on fast arithmetic digital demodulation of DQPSK is presented. The new method only uses the sign of the modulated signal instead of digital signal through the A/D in the traditional method. With the new method, the system has higher speed, and can save some hardware in the FPGA. An experiment of the new method with the DQPSK is given in this paper.
Qin, Jianhuan; Huang, Zhiming; Ge, Yujian; Hou, Yun; Chu, Junhao
2009-03-01
Dual-modulated spectroscopy is one of the most powerful methods in the measurement of modulation spectroscopy. Here we develop a tandem lock-in amplifier (LIA) based on digital signal processor to implement a novel algorithm of tandem demodulation. The theoretical analysis of demodulation algorithm is presented, and the implementation of this tandem LIA is described in detail. Compared to the traditional demodulating way with two LIAs in cascade, this tandem LIA eliminates the extra quantization error of redundant analog-to-digital and digital-to-analog conversions and removes the limitation to the time constant in the commercial LIA, hence lowers the requirement of frequency ratio in dual-modulated spectroscopy. The applications are given as examples in the photoreflectance (PR) measurements of GaAs (100) thin film and GaSb bulk material, respectively, at the different optical energy regions. The experimental results indicate that this tandem is well capable of PR spectra measurement with good PR lineshapes and reasonable signal noise ratio. A brief comparison of GaAs PR results between tandem LIA and two LIAs is made to prove the efficiency and advantages of the tandem LIA.
Connord, V; Mehdaoui, B; Tan, R P; Carrey, J; Respaud, M
2014-09-01
A setup for measuring the high-frequency hysteresis loops of magnetic samples is described. An alternating magnetic field in the range 6-100 kHz with amplitude up to 80 mT is produced by a Litz wire coil. The latter is air-cooled using a forced-air approach so no water flow is required to run the setup. High-frequency hysteresis loops are measured using a system of pick-up coils and numerical integration of signals. Reproducible measurements are obtained in the frequency range of 6-56 kHz. Measurement examples on ferrite cylinders and on iron oxide nanoparticle ferrofluids are shown. Comparison with other measurement methods of the hysteresis loop area (complex susceptibility, quasi-static hysteresis loops, and calorific measurements) is provided and shows the coherency of the results obtained with this setup. This setup is well adapted to the magnetic characterization of colloidal solutions of magnetic nanoparticles for magnetic hyperthermia applications.
PN acquisition demodulator achieves automatic synchronization of a telemetry channel
Couvillon, L.
1966-01-01
Data demodulator for automatic sync acquisition provides an automatic means for obtaining initial word and bit synchronization in a pulse-code-modulated/phase-shift-keyed digital communications system.
DEFF Research Database (Denmark)
Serban, I.; Teodorescu, Remus; Marinescu, C.
2012-01-01
This paper presents an original hardware-in-the-loop (HIL) solution for real-time testing and optimization of the frequency control mechanism in autonomous microgrids (MG), when battery energy storage systems (BESS) are integrated along classical and RES-based generators to stabilize the frequency...... in terms of active power, and therefore the need of improving the MG power reserve by adding energy storage systems is often demanded. The proposed HIL solution aims to improve the design of the BESS frequency control systems according to the MG characteristics, being based on aggregated models...
Institute of Scientific and Technical Information of China (English)
向劲松; 潘乐春; 张苗苗; 张孝雷
2011-01-01
Optical phase-locked loop(OPLL) is often used in space coherent optical communication as the traditional way to achieve the phase synchronous. But the OPLL is affected by the Doppler frequency shift, so in this paper, we use an open-loop compensation technology based on DSP to compensate the Doppler frequency shift, and apply it to a recursive demodulate system, demodulating the next data according to the previous data information. Simulation results show that the open-loop compensation technology based on DSP is able to compensate the Doppler frequency shift, and allow the space coherent optical communication system to demodulate without any optical phase-locked loop, and the performance of the system can approach the ideal status which Doppler frequency shift is completely compensated.%目前通常采用光锁相环(optical phase-locked loop,OPLL)完成空间相干光通信中的相位同步.针对光锁相环性能受空间通信终端间多普勒频移影响的不足,采用基于数字信号处理(digital singnal procesor,DSP)的开环方法补偿多普勒频移,并将开环补偿方法应用于一种递推解调系统中,根据前一时刻的数据信息进行后一时刻的数据解调.仿真结果表明:采用基于DSP的开环补偿方法可以补偿多普勒频移,使空间相干光通信系统不使用光锁相环,且性能接近多普勒频移被完全补偿的理想状态.
8PSK Demodulator for New Generation DVB-S2
Botticchio, T.; Burzigotti, P.; de Gaudenzi, R.; Luise, M.; Martinez, A.; Richichi, F.; Tabacco, P.
This article describes the architecture and the performance of a robust and near Shannon limit 8PSK Demodulator aimed in term of complexity for symbol rate from 11Mbaud to 27.5Mbaud. Being very accurate in terms of the residual jitter for carrier and clock, the Demodulator is aimed for use of Pragmatic Turbo Trellis Codes. A possible structure-reuse for a multi-modulation has been also investigated accordingly with the future satellite broadcasting and contribution services.
Singular value demodulation of phase-shifted holograms
Lopes, Fernando
2015-01-01
We report on phase-shifted holographic interferogram demodulation by singular value decomposition. Numerical processing of optically-acquired interferograms over several modulation periods was performed in two steps : 1- rendering of off-axis complex-valued holograms by Fresnel transformation of the interferograms; 2- eigenvalue spectrum assessment of the lag-covariance matrix of hologram pixels. Experimental results in low-light recording conditions were compared with demodulation by Fourier analysis, in the presence of random phase drifts.
Demodulation for multi vortex beams based on composite diffraction hologram
Zhang, Weibin; Li, Yingchun; Sun, Tengfen; Shao, Wei; Zhu, Fuquan; Wang, YingYing
2016-12-01
While projecting a Gaussian beam onto the spatial light modulator (SLM) which has loaded a composite hologram, several vortex beams can be generated at one time. On the contrary, while projecting the corresponding vortex beam onto the hologram, the Gaussian beam can be restored, realizing the demodulation of vortex beam. In traditional optical communication systems, a hologram can only demodulate one incident vortex beam. In this paper, a vortex beam demodulation method based on composite diffraction hologram is proposed, which can demodulate several incident vortex beams with only one hologram. An experimental system is set up in this paper which achieves the generation, transmission and demodulation experiments of vortex beams with 64QAM-OFDM signals. After a series of offline processing on the demodulated Gaussian beam, constellation and bit error rates (BER) of each subcarrier for OFDM signals are acquired. The experimental results show that good system performance can be achieved with this method as the BERs of all subcarriers are under the FEC threshold.
Directory of Open Access Journals (Sweden)
Hua-Qing Wang
2014-01-01
Full Text Available Vibration signals of rolling element bearings faults are usually immersed in background noise, which makes it difficult to detect the faults. Wavelet-based methods being used commonly can reduce some types of noise, but there is still plenty of room for improvement due to the insufficient sparseness of vibration signals in wavelet domain. In this work, in order to eliminate noise and enhance the weak fault detection, a new kind of peak-based approach combined with multiscale decomposition and envelope demodulation is developed. First, to preserve effective middle-low frequency signals while making high frequency noise more significant, a peak-based piecewise recombination is utilized to convert middle frequency components into low frequency ones. The newly generated signal becomes so smoother that it will have a sparser representation in wavelet domain. Then a noise threshold is applied after wavelet multiscale decomposition, followed by inverse wavelet transform and backward peak-based piecewise transform. Finally, the amplitude of fault characteristic frequency is enhanced by means of envelope demodulation. The effectiveness of the proposed method is validated by rolling bearings faults experiments. Compared with traditional wavelet-based analysis, experimental results show that fault features can be enhanced significantly and detected easily by the proposed method.
Digital Synthetic-heterodyne Interferometric Demodulation Based on Embedded System
Institute of Scientific and Technical Information of China (English)
MENG Ju; WANG Jin-hai; CHEN Cai-he; ZHANG Cheng
2006-01-01
Optical fiber acceleration seismometer as an important instrument can offer high sensitivity,anti-jamming and non-touched advantage which has an extensive application field. Its signal processing ability will decide whole system's performance to some extent because it will affect directly the factors such as resolving power,precision and dynamic range. The signal processing is usually realized by analog circuits which was more inferior in stability,flexibility and anti-jamming to digital processing system. A digital processing system of optical fiber acceleration seismometer has been designed based on the embedded system design scheme. Synthetic-heterodyne demodulation has been studied,and signal processing has been realized. The double processors of ARM and DSP are employed to implement respectively the system control and signal processing,and to provide the output interfaces such as LCD,DAC and Ethernet interface. This system can vary with the measured signal in real time and linearly,and its work frequency bandwidth is between 10 Hz and 1 kHz. The system has better anti-jamming ability and can work normally when the SNR is 40 dB.
Flexible black phosphorus ambipolar transistors, circuits and AM demodulator.
Zhu, Weinan; Yogeesh, Maruthi N; Yang, Shixuan; Aldave, Sandra H; Kim, Joon-Seok; Sonde, Sushant; Tao, Li; Lu, Nanshu; Akinwande, Deji
2015-03-11
High-mobility two-dimensional (2D) semiconductors are desirable for high-performance mechanically flexible nanoelectronics. In this work, we report the first flexible black phosphorus (BP) field-effect transistors (FETs) with electron and hole mobilities superior to what has been previously achieved with other more studied flexible layered semiconducting transistors such as MoS2 and WSe2. Encapsulated bottom-gated BP ambipolar FETs on flexible polyimide afforded maximum carrier mobility of about 310 cm(2)/V·s with field-effect current modulation exceeding 3 orders of magnitude. The device ambipolar functionality and high-mobility were employed to realize essential circuits of electronic systems for flexible technology including ambipolar digital inverter, frequency doubler, and analog amplifiers featuring voltage gain higher than other reported layered semiconductor flexible amplifiers. In addition, we demonstrate the first flexible BP amplitude-modulated (AM) demodulator, an active stage useful for radio receivers, based on a single ambipolar BP transistor, which results in audible signals when connected to a loudspeaker or earphone. Moreover, the BP transistors feature mechanical robustness up to 2% uniaxial tensile strain and up to 5000 bending cycles.
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.
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.
Performance analysis of digital FM demodulators for fading channels in the threshold region
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.
Chip design of a 5.8-GHz fractional-N frequency synthesizer with a tunable Gm-C loop filter
Institute of Scientific and Technical Information of China (English)
Huang Jhin-Fang; Liu Ron-Yi; Lai Wen-Cheng; Shin Chun-Wei; Hsu Chien-Ming
2012-01-01
This paper proposes a novel Gm-C loop filter insteai of a conventional passive loop filter used in a phase-locked loop.The innovative advantage of the proposed architecture is tunable loop filter bandwidth and hence the process variations of passive elements of resistance R and capacitance C can be overcome and the chip area is greatly reduced.Furthermore,the MASH 1-1-1 sigma-delta (Σ△) modulator is adopted for performing the fractional division number and hence improves the phase noise as well.Measured results show that the locked phase noise is -114.1 dBc/Hz with lower Gm-C bandwidth and -111.7 dBm/C with higher Gm-C bandwidth at 1 MHz offset from carrier of 5.68 GHz.Including pads and built-in Gm-C filter,the chip area of the proposed frequency synthesizer is 1.06 mm2.The output power is -8.69 dBm at 5.68 GHz and consumes 56 mW with an off-chip buffer from 1.8-V supply voltage.
Michelson interferometer vibrometer using self-correcting synthetic-heterodyne demodulation.
Connelly, Michael J; Galeti, José Henrique; Kitano, Cláudio
2015-06-20
Synthetic-heterodyne demodulation is a useful technique for dynamic displacement and velocity detection in interferometric sensors, as it can provide an output signal that is immune to interferometric drift. With the advent of cost-effective, high-speed real-time signal-processing systems and software, processing of the complex signals encountered in interferometry has become more feasible. In synthetic heterodyne, to obtain the actual dynamic displacement or vibration of the object under test requires knowledge of the interferometer visibility and also the argument of two Bessel functions. In this paper, a method is described for determining the former and setting the Bessel function argument to a set value, which ensures maximum sensitivity. Conventional synthetic-heterodyne demodulation requires the use of two in-phase local oscillators; however, the relative phase of these oscillators relative to the interferometric signal is unknown. It is shown that, by using two additional quadrature local oscillators, a demodulated signal can be obtained that is independent of this phase difference. The experimental interferometer is a Michelson configuration using a visible single-mode laser, whose current is sinusoidally modulated at a frequency of 20 kHz. The detected interferometer output is acquired using a 250 kHz analog-to-digital converter and processed in real time. The system is used to measure the displacement sensitivity frequency response and linearity of a piezoelectric mirror shifter over a range of 500 Hz to 10 kHz. The experimental results show good agreement with two data-obtained independent techniques: the signal coincidence and denominated n-commuted Pernick method.
A Novel Method of Edge Filter Linear Demodulation Using Long Period Grating in Fiber Sensor System
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
A novel method of linear demodulation based on edge filter is presented. An experimental system is built up in which LPG is used as the edge filter. We achieve linear demodulation with a bandwidth of 5nm.
Rancang Bangun Demodulator FSK 1200 Baud untuk Perangkat Receiver Payload Satelit IiNUSAT-01
Directory of Open Access Journals (Sweden)
Iwan Hendrianto
2012-09-01
Full Text Available Satelit merupakan suatu space segment yang berfungsi sebagai repeater dari ground segment (stasiun bumi dapat menerima dan memancarkan kembali sinyal dari stasiun bumi untuk komunikasi data yang memiliki dimensi terbatas (nano satelit. Salah satu bagian dari payload satelit adalah demodulator yang berfungsi mengembalikan sinyal hasil modulasi ke bentuk semula. Dalam makalah ini membahas perancangan dan pemembuatan perangkat demodulator FSK 1200 baud beserta pengujiannya. Demodulator ini dibuat dalam dua rangkaian yaitu demodulator dengan TCM 3105 dan demodulator dengan ADF 7021. Untuk hasil uji demodulator TCM 3105 telah teruji dan bisa mendemodulasikan sinyal yang dikirim dengan baik, pengiriman data teks dengan menggunakan media radio juga memperoleh hasil yang baik. Sedangkan pengujian demodulator ADF 7021 juga dapat mendemodulasikan dengan sinyal yang dikirim dengan baik hanya saja umur pakainya tidak terlalu lama. Dari hasil seluruh pengujian maka demodulator dengan TCM 3105 mimiliki kinerja yang baik dan bisa digunakan komukasi pada satelit Iinusat-01.
On optimal soft-decision demodulation. [in digital communication system
Lee, L.-N.
1976-01-01
A necessary condition is derived for optimal J-ary coherent demodulation of M-ary (M greater than 2) signals. Optimality is defined as maximality of the symmetric cutoff rate of the resulting discrete memoryless channel. Using a counterexample, it is shown that the condition derived is generally not sufficient for optimality. This condition is employed as the basis for an iterative optimization method to find the optimal demodulator decision regions from an initial 'good guess'. In general, these regions are found to be bounded by hyperplanes in likelihood space; the corresponding regions in signal space are found to have hyperplane asymptotes for the important case of additive white Gaussian noise. Some examples are presented, showing that the regions in signal space bounded by these asymptotic hyperplanes define demodulator decision regions that are virtually optimal.
Tucker, Eric; D' Archangel, Jeffrey; Raschke, Markus B; Boreman, Glenn
2015-05-04
Mid-infrared scattering scanning near-field optical microscopy, in combination with far-field infrared spectroscopy, and simulations, was employed to investigate the effect of mutual-element coupling towards the edge of arrays of loop elements acting as frequency selective surfaces (FSSs). Two different square loop arrays on ZnS over a ground plane, resonant at 10.3 µm, were investigated. One array had elements that were closely spaced while the other array had elements with greater inter-element spacing. In addition to the dipolar resonance, we observed a new emergent resonance associated with the edge of the closely-spaced array as a finite size effect, due to the broken translational invariance.
Linearity optimization of edge filter demodulators in FBGs
Li, Dong-Sheng; Sui, Qing-Mei; Cao, Yu-Qiang
2008-05-01
A kind of electric circuit is improved to optimize the linearity of edge filter demodulators in FBGs. By using a logarithm amplifier and an extraction operation, the linear range of optimized edge filter demodulators has been broadened effectively, and the requirement of optical filter’s linear range has been reduced. Theoretical analyses and the simulation results indicated that the linear range of optimized edge filter demodulator’s covers the whole transition region of the edge filter, while a strict linearity of the optical filter is not necessary.
NOVEL FIBER GRATING SENSOR DEMODULATION TECHNIQUE BASED ON OPTICAL WAVELET FILTERING
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The optical wavelet filter is designed. It can filter and choose frequency swiftly. It can realize demodulation of distributed fiber Bragg grating(FBG) measurement system. Its scanning resolution and scanning period depend on wavelet function. Wavelet function is controlled by computer. Compared to conventional scan filter, optical wavelet filtering has some advantages such as simple structure, high scan frequency, high resolution and good linearity. At last, the error of optical wavelet filter scanning procedure is analyzed. Scanning step length refers to the shifting of optical wavelet window's central frequency. It affects system precision directly. If scanning step length is different, the measured signal is different. The methods of reducing step length guarantee scanning periodic time are presented.
Padilla, Moises; Garnica, Guillermo
2016-01-01
In this paper we apply the frequency transfer function (FTF) formalism to analyze the red, green and blue (RGB) phase-shifting fringe-projection profilometry technique. The phase-shifted fringe patterns in RGB fringe projection are typically corrupted by crosstalk because the sensitivity curves of most projection-recording systems overlap. Crosstalk distortion needs to be compensated in order to obtain high quality measurements. We study phase-demodulation methods for null/mild, moderate, and severe levels of RGB crosstalk. For null/mild crosstalk, we can estimate the searched phase-map using Bruning's 3-step phase-shifting algorithm (PSA). For moderate crosstalk, the RGB recorded data is usually preprocessed before feeding it into Bruning's PSA; alternatively, in this paper we propose a computationally more efficient approach, which combines crosstalk compensation and phase-demodulation into a single process. For severe RGB crosstalk, we expect non-sinusoidal fringes' profiles (distorting harmonics) and sign...
Servin, Manuel; Garnica, Guillermo
2015-01-01
360-degrees digitalization of three-dimensional (3D) solids using a projected light-strip is a well established technique. These profilometers project a light-strip over the solid under analysis while the solid is rotated a full revolution. Then a computer program typically extracts the centroid of this light-strip, and by triangulation one obtains the shape of the solid. Here instead of using intensity-based strip centroid estimation, we propose to use Fourier phase-demodulation. This 360-degrees profilometer first constructs a carrier-frequency fringe-pattern by closely adding individual light-strip images. Secondly this high-density fringe-pattern is phase-demodulated using the standard Fourier technique.
Research on the Comprehensive Demodulation of Gear Tooth Crack Early Fault
Institute of Scientific and Technical Information of China (English)
CUI Lingli; DING Fang; GAO Lixin; ZHANG Jianyu
2006-01-01
The component of gear vibration signal is very complex, when a localized tooth defect such as a tooth crack is present, the engagement of the cracked tooth will induce an impulsive change with comparatively low energy to the gear mesh signal and the background noise. This paper presents a new comprehensive demodulation method which combined with amplitude envelop demodulation and phase demodulation to extract gear crack early fault. A mathematical model of gear vibration signal contain crack fault is put forward. Simulation results based on this model show that the new comprehensive demodulation method is more effective in finding fault and judging fault level then conventional single amplitude demodulation at present.
Gottardi, Luciano; Gao, Jan-R; Hartog, Roland den; Hijmering, Richard; Hoevers, Henk; Khosropanah, Pourya; de Korte, Piet; van der Kuur, Jan; Lindeman, Mark; Ridder, Marcel
2016-01-01
SRON is developing the Frequency Domain Multiplexing (FDM) readout and the ultra low NEP TES bolometers array for the infrared spectrometer SAFARI on board of the Japanese space mission SPICA. The FDM prototype of the instrument requires critical and complex optimizations. For single pixel characterization under AC bias we are developing a simple FDM system working in the frequency range from 1 to 5 MHz, based on the open loop read-out of a linearized two-stage SQUID amplifier and high Q lithographic LC resonators. We describe the details of the experimental set-up required to achieve low power loading (< 1 fW) and low noise (NEP $\\sim 10^{-19} W/Hz^{1/2}$) in the TES bolometers. We conclude the paper by comparing the performance of a $4 \\cdot 10^{-19} W/Hz^{1/2}$ TES bolometer measured under DC and AC bias.
Jung, Kwangyun; Kang, Jinho; Hunziker, Stephan; Min, Chang-Ki; Kim, Jungwon
2013-01-01
We demonstrate a remote microwave/radio-frequency (RF) transfer technique based on the stabilization of a fiber link using a fiber-loop optical-microwave phase detector (FLOM-PD). This method compensates for the excess phase fluctuations introduced in fiber transfer by direct phase comparison between the optical pulse train reflected from the remote site and the local microwave/RF signal using the FLOM-PD. This enables sub-fs resolution and long-term stable link stabilization while having wide timing detection range and less demand in fiber dispersion compensation. The demonstrated relative frequency instability between 2.856-GHz RF oscillators separated by a 2.3-km fiber link is $7.6 \\times 10^{-18}$ and $6.5 \\times 10^{-19}$ at 1000 s and 82500 s averaging time, respectively.
Wind Turbine Gearbox Fault Diagnosis Based on Improved EEMD and Hilbert Square Demodulation
Directory of Open Access Journals (Sweden)
Huanguo Chen
2017-01-01
Full Text Available The rapid expansion of wind farms has accelerated research into improving the reliability of wind turbines to reduce operational and maintenance costs. A critical component in wind turbine drive-trains is the gearbox, which is prone to different types of failures due to long-term operation under tough environments, variable speeds and alternating loads. To detect gearbox fault early, a method is proposed for an effective fault diagnosis by using improved ensemble empirical mode decomposition (EEMD and Hilbert square demodulation (HSD. The method was verified numerically by implementing the scheme on the vibration signals measured from bearing and gear test rigs. In the implementation process, the following steps were identified as being important: (1 in order to increase the accuracy of EEMD, a criterion of selecting the proper resampling frequency for raw vibration signals was developed; (2 to select the fault related intrinsic mode function (IMF that had the biggest kurtosis index value, the resampled signal was decomposed into a series of IMFs; (3 the selected IMF was demodulated by means of HSD, and fault feature information could finally be obtained. The experimental results demonstrate the merit of the proposed method in gearbox fault diagnosis.
Realization of OFDM modulation and demodulation for visible light communication based on FPGA
Wu, Chun-hui; Gao, Zong-yu; Li, Hong-lei; Chen, Xiong-bin; Mao, Xu-rui; Lu, Hui-min; Wang, Jian-ping; He, Lin; Cui, Shi-gang; Chen, Hong-da
2017-01-01
In order to ensure stable, correct and real-time high-speed transmission of indoor visible light communication (VLC), the key modulation and demodulation technologies of orthogonal frequency division multiplexing (OFDM) are studied in this paper. The time-domain synchronization, frequency synchronization and channel equalization of receiver are analyzed and optimized by utilizing short and long training preamble. Moreover, field programmable gate array (FPGA) development board (Xilinx Kintex-7) and Verilog hardware description language are used to realize the design of proposed OFDM-VLC system. Simulation and experiment both verify the feasibility of the hardware designs of this system. The proposed OFDM-based VLC system can process signal in real-time, which can be used in actual VLC application systems.
FPGA IMPLEMENTATION OF LOW POWER DIGITAL FREQUENCY
Directory of Open Access Journals (Sweden)
K. R. Rekha,
2010-10-01
Full Text Available In this Paper we are presenting a new FPGA approach to design an optimized use a Digital Frequency Synthesizer (DDFS in our system to generate a sampled sinusoidal wave of frequency. The major advantage of Digital Frequency Synthesizer (DFS is that its output frequency, phase and amplitude can be precisely and rapidly manipulated under the control of a DSP. Other inherent DFS attributes include the ability to tune with extremely fine frequency and phase resolution and to rapidly “hop” between the frequencies. These combined characteristics have made this technology popular in military, radar and communications systems. The digital circuits used to implementsignal processing functions do not suffer the effects of thermal drifts, aging and component variations associated with their analog counterparts. The implementation of digital functional blocks makes it possible to achieve a high degree of system integration. Recent advances in IC fabrication technology, particularly the CMOS technology coupled with advanced DSP algorithms and architectures provide possible single chip solutions to complex communication and signal processing sub-systems such as modulators, demodulators, local oscillators, and programmable clock generators, cellular base stations, up converters, down converters, power line communication,wireless local loop base stations etc .
Development of high precision digital driver of acoustic-optical frequency shifter for ROG
Zhang, Rong; Kong, Mei; Xu, Yameng
2016-10-01
We develop a high precision digital driver of the acoustic-optical frequency shifter (AOFS) based on the parallel direct digital synthesizer (DDS) technology. We use an atomic clock as the phase-locked loop (PLL) reference clock, and the PLL is realized by a dual digital phase-locked loop. A DDS sampling clock up to 320 MHz with a frequency stability as low as 10-12 Hz is obtained. By constructing the RF signal measurement system, it is measured that the frequency output range of the AOFS-driver is 52-58 MHz, the center frequency of the band-pass filter is 55 MHz, the ripple in the band is less than 1 dB@3MHz, the single channel output power is up to 0.3 W, the frequency stability is 1 ppb (1 hour duration), and the frequency-shift precision is 0.1 Hz. The obtained frequency stability has two orders of improvement compared to that of the analog AOFS-drivers. For the designed binary frequency shift keying (2-FSK) and binary phase shift keying (2-PSK) modulation system, the demodulating frequency of the input TTL synchronous level signal is up to 10 kHz. The designed digital-bus coding/decoding system is compatible with many conventional digital bus protocols. It can interface with the ROG signal detecting software through the integrated drive electronics (IDE) and exchange data with the two DDS frequency-shift channels through the signal detecting software.
Directory of Open Access Journals (Sweden)
S. U. Jen
2014-12-01
Full Text Available Frequency dependence of magnetostrictive phenomenon of as-cast 2605SA1 ribbon was studied. We applied a sinusoidal sweeping field (H, with a fixed frequency (f, along length (L of the ribbon, and simultaneously recorded the longitudinal magnetostriction (λ∥ and the transverse magnetostriction (λ⊥ as a function of time (t, respectively. f was varied from 0.07 to 122 Hz. In the low-f case (f =0.07 Hz, we observed the frequency-doubling (FD feature in λ∥(t and λ⊥(t curves; i.e., only even harmonic magnetostrictive signals showed up. In the high-f case (f = 122 Hz, we observed the no-frequency-doubling (NFD feature; i.e., both odd and even harmonic magnetostrictive signals showed up. A theory, based on the balance among various torques acting on magnetization, is developed to explain the f dependence of the magnetostriction phenomenon observed. From this theory, we conclude that only when the reflection symmetry of the system is reserved, i.e., when the equivalent easy axis (EEA is perpendicular to L, will λ∥(t and λ⊥(t have the true-frequency-doubling (TFD feature. However, for the as-cast 2605SA1 ribbon, EEA is not perpendicular to L. Thus, strictly speaking, we should observe the NFD feature only. Nevertheless, in the low-f limit, we can show that the FD feature is somewhat allowed under the condition, b/α being close to 1, where b and α are the two parameters used in the theory. From experimental data, this condition is met for as-cast 2605SA1. To make a distinction from TFD, this low-f feature is called close-frequency-doubling (CFD in this paper. In general, the theory explains all the experimental results fairly well.
A new coherent demodulation technique for land-mobile satellite communications
Yoshida, Shousei; Tomita, Hideho
1990-01-01
An advanced coherent demodulation technique is described for land mobile satellite (LMS) communications. The proposed technique features a combined narrow/wind band dual open loop carrier phase estimator, which is effectively able to compensate the fast carrier phase fluctuation by fading with sacrificing a phase slip rate. Also included is the realization of quick carrier and clock reacquisition after shadowing by taking open loop structure. Its bit error rate (BER) performance is superior to that of existing detection schemes, showing a BER of 1 x 10(exp -2) at 6.3 dB E sub b/N sub o over the Rician channel with 10 dB C/M and 200 Hz (1/16 modulation rate) fading pitch f sub d for QPSK. The proposed scheme consists of a fast response carrier recovery and a quick bit timing recovery with an interpolation. An experimental terminal model was developed to evaluate its performance at fading conditions. The results are quite satisfactory, giving prospects for future LMS applications.
Comparative analysis of modulation and demodulation methods of the control signals of rail line
Directory of Open Access Journals (Sweden)
K.V.Goncharov
2012-12-01
Full Text Available Introduction: One of the ways of increasing the noise stability rail circuit is the use more informative waveform of control signal. Use in rail circuit modulated signals gives several informative selective traits in relatively narrow spectrum. The study of features of various modulation and demodulation methods with considering operating conditions of rail circuits is urgent. Purpose: the search for more informative forms of rail line control signal, the search for improved methods of signal processing of control current. Methods: For carrying out researches the method of signals decomposition in Fourier series and the simulation with the method of statistical tests have been sed. Results: Spectrum of frequency shift signal is wider than the spectrum of amplitude shift and phase shift signals by an amount equal to twice the frequency deviation. The research of correlation coherent and incoherent reception methods of rail line control signal has been carried out. In this case, we used the following models of interferences: white Gaussian noise, random pulse sequence and sinusoidal interference. It has been found that the transition from amplitude to frequency shift keying reduces signal/noise ratio by 2...4 dB, depending from the signal level and the type of noise. Losing amplitude shift keying receiver compared with the phase shift keying receiver is 5...6 dB. Conclusions: The use of more advanced methods of modulation and demodulation improves noise stability of rail circuit. When using correlation methods reception phase shift keying provides the best noise stability, and amplitude – the worst.
Design and Development of an Automated Demodulator Calibration Station
2009-12-01
demodulator board, and versatility for future modifications and bread -boarding. Several validation tests were conducted to verify the hardware and...unlimited help and advice. I am especially grateful to Mr. Robert D. Broadston, Lab Director for the ECE Microwave Lab. He has made available his support...amazing; he is truly a man of all trades. My sincere thanks go in particular to Mr. Jiheon Ryu, a very experienced microwave engineer from Korea
Directory of Open Access Journals (Sweden)
Zeinab eBirjandian
2013-11-01
Full Text Available The inhibition of excitatory (pyramidal neurons directly dampens their activity resulting in a suppression of neural network output. The inhibition of inhibitory cells is more complex. Inhibitory drive is known to gate neural network synchrony, but there is also a widely held view that it may augment excitability by reducing inhibitory cell activity, a process termed disinhibition. Surprisingly, however, disinhibition has never been demonstrated to be an important mechanism that augments or drives the activity of excitatory neurons in a functioning neural circuit. Using voltage sensitive dye imaging (VSDI we show that 20-80 Hz stimulus trains, (beta-gamma activation, of the olfactory cortex pyramidal cells in layer II leads to a subsequent reduction in inhibitory interneuron activity that augments the efficacy of the initial stimulus. This disinhibition occurs with a lag of about 150-250 ms after the initial excitation of the layer 2 pyramidal cell layer. In addition activation of the endopiriform nucleus also arises just before the disinhibitory phase with a lag of about 40-80 ms. Preventing the spread of action potentials from layer II stopped the excitation of the endopiriform nucleus, abolished the disinhibitory activity and reduced the excitation of layer II cells. After the induction of experimental epilepsy the disinhibition was more intense with a concomitant increase in excitatory cell activity. Our observations provide the first evidence of feed forward disinhibition loop that augments excitatory neurotransmission, a mechanism that could play an important role in the development of epileptic seizures.
Yim, Wan Hung
Economical operation of future satellite systems for mobile communications can only be fulfilled by using dedicated on-board processing satellites, which would allow both cheap earth terminals and lower space segment costs. With on-board modems and codecs, the up-link and down-link can be optimized separately. An attractive scheme is to use frequency-division multiple access/single chanel per carrier (FDMA/SCPC) on the up-link and time division multiplexing (TDM) on the down-link. This scheme allows mobile terminals to transmit a narrow band, low power signal, resulting in smaller dishes and high power amplifiers (HPA's) with lower output power. On the up-link, there are hundreds to thousands of FDM channels to be demodulated on-board. The most promising approach is the use of all-digital multicarrier demodulators (MCD's), where analog and digital hardware are efficiently shared among channels, and digital signal processing (DSP) is used at an early stage to take advantage of very large scale integration (VLSI) implementation. A MCD consists of a channellizer for separation of frequency division multiplexing (FDM) channels, followed by individual modulators for each channel. Major research areas in MCD's are in multirate DSP, and the optimal estimation for synchronization, which form the basis of the thesis. Complex signal theories are central to the development of structured approaches for the sampling and processing of bandpass signals, which are the foundations in both channellizer and demodulator design. In multirate DSP, polyphase theories replace many ad-hoc, tedious and error-prone design procedures. For example, a polyphase-matrix deep space network frequency and timing system (DFT) channellizer includes all efficient filter bank techniques as special cases. Also, a polyphase-lattice filter is derived, not only for sampling rate conversion, but also capable of sampling phase variation, which is required for symbol timing adjustment in all
Complex Demodulation for Bearing Fault Detection
1989-10-01
components are filtered, using a digital, zero phase filter . A frequency domain representation of the filtered signal is shown in Figure 3. Digital...filtering can be seen as the convolution of the heterodyned signal with the impulse response of the zero phase filter . The resulting function {W) is then...given by, W = V H (4) where * denotes convolution and (H) is the impulse response of the zero phase filter . This can be rewritten using the convolution
Fiber grating sensor demodulation technique using a linear array of photodetectors
Jun, Tao; Lei, Mu; Ping, Du
2008-12-01
The article describes the theory, characters and performance of the linear array of photodetectors includes CCD, PDA, CMOS and InGaAs, presents fiber grating sensor demodulation technique using linear InGaAs array and designs the demodulation system based on this technique. Furthermore, the system is used to measure the strain and temperature respectively, and prove the system have a good practicability. The demodulation system has a high resolution and measurement precision, changes the size of traditional Fiber Grating Sensors demodulation system essentially, and realizes basically the intelligence of the FBG sensors and lays a foundation for the industrialization of the FBG sensors.
Demodulator for Chaotic Secure Communication Based on Proportional-integral Feedback Design
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
A scheme of chaotic secure communication based on the parameter modula tion and the inversion of a chaotic dynamical system is analyzed. According to this scheme,information signal is modulated by a bifurcation parameter of the transmitter,which is in chaotic state.In the receiver,a proportional integral feedback demodulator is used to demodulate the information signal,which only uses the available synchronizing error as well as stateness of receiver. The purpose of this demodulator is proposed to overcome the influence of differentiation oper ation, nonlinear part and singularities in chaotic system. Numerical simulation is proposed to show the effectiveness of this demodulator.
Shang, Ying; Yang, Yuan-Hong; Wang, Chen; Liu, Xiao-Hui; Wang, Chang; Peng, Gang-Ding
2016-06-01
We propose a demodulated signal distribution theory for a self-interfered distributed acoustic sensing system. The distribution region of Rayleigh backscattering including the acoustic sensing signal in the sensing fiber is investigated theoretically under different combinations of both the path difference and pulse width Additionally we determine the optimal solution between the path difference and pulse width to obtain the maximum phase change per unit length. We experimentally test this theory and realize a good acoustic pressure phase sensitivity of -150 dB re rad/(μPa·m) of fiber in the frequency range from 200 Hz to 1 kHz.
Levesque, Philippe; Sawan, Mohamad
2009-08-01
A fully hardware-based real-time digital wideband quadrature demodulation processor based on the Hilbert transform is proposed to process ultrasound radio frequency signals. The presented architecture combines 2 finite impulse response (FIR) filters to process in-phase and quadrature signals and includes a piecewise linear approximation architecture that performs the required square root operations. The proposed implementation enables flexibility to support different transducers with its ability to load on-the-fly different FIR filter coefficient sets. The complexity and accuracy of the demodulator processor are analyzed with simulated RF data; a normalized residual sum-of-squares cost function is used for comparison with the Matlab Hilbert function. Three implementations are integrated into a hand-held ultrasound system for experimental accuracy and performance evaluation. Real-time images were acquired from a reference phantom, demonstrating the feasibility of using the presented architecture to perform real-time digital quadrature demodulation of ultrasonic signal echoes. Experimental results show that the implementation, using only 2942 slices and 3 dedicated digital multipliers of a low-cost and low-power field-programmable gate array (FPGA) is accurate relative to a comparable software- based system; axial and lateral resolution of 1 mm and 2 mm, respectively, were obtained with a 12-mm piezoelectric transducer without postprocessing. Because the processing and sampling rates are the same, high-frequency ultrasound signals can be processed as well. For a 15-frame-per-second display, the hand-held ultrasonic imaging-processing core (FPGA, memory) requires only 45 mW (dynamic) when using a 5-MHz single-element piezoelectric transducer.
Iterative Demodulation and Decoding Scheme with 16QAM
Institute of Scientific and Technical Information of China (English)
LIU Lin-nan; KUANG Jing-ming; LI Ming; FEI Ze-song
2006-01-01
Iterative demodulation and decoding scheme is analyzed and modulation labeling is considered to be one of the crucial factors to this scheme. By analyzing the existent mapping design criterion, four aspects are found as the key techniques for choosing a label mapping. Based on this discovery, a novel mapping design criterion is proposed and two label mappings are searched according to it. Simulation results show that the performance of BICM-ID using the novel mappings is better than the former ones. The extrinsic information transfer(EXIT) chart is introduced and it is used to evaluate the proposed mapping design criteria.
Institute of Scientific and Technical Information of China (English)
刘小军; 石玉; 赵宝林
2011-01-01
According to Jiles-Atherton ferromagnetic hysteresis theory and Hammerstein configuration we presented a Pspice circuit model of high frequency dynamic magnetic hysteresis loop. A Second-order low-pass filter has been inserted into the equivalent Pspice circuit of Jiles-Atherton mathematic model to capture the changes of magnetic hysteresis loop with frequency to analog the high frequency dynamic magnetic hysteresis loop approximately. The simulated magnetic hysteresis loop using this Pspice circuit model is preferably fitted with the measured result in frequency up to 300kHz.%根据Jiles-Atherton铁磁磁滞理论和Hammerstein结构宏模型提出了一种高频动态磁滞回线的PSpice电路模型.将二阶低通滤波器插入Jiles-Atherton数学模型的等效PSpice电路中,追踪磁滞回线随频率的变化,近似地模拟高频动态磁滞回线.经实验论证,用该PSpice电路模型仿真所得磁滞回线与实际测试结果在频率高达300kHz时仍然能较好符合.
Institute of Scientific and Technical Information of China (English)
Wu Zhaohui; Zhang Xu; Liang Zhiming; Li Bin
2012-01-01
A new BPSK demodulator was presented.By using a clock multiplier with very simple circuit structure to replace the analog multiplier in the traditional BPSK demodulator,the circuit structure of the demodulator became simpler and hence its power consumption became lower.Simpler structure and lower power will make the designed demodulator more suitable for use in an internal single chip design for a wireless implantable neural recording system.The proposed BPSK demodulator was implemented by Global Foundries 0.35 μm CMOS technology with a 3.3 V power supply.The designed chip area is only 0.07 mm2 and the power consumption is 0.5 mW.The test results show that it can work correctly.
Zhaohui, Wu; Xu, Zhang; Zhiming, Liang; Bin, Li
2012-05-01
A new BPSK demodulator was presented. By using a clock multiplier with very simple circuit structure to replace the analog multiplier in the traditional BPSK demodulator, the circuit structure of the demodulator became simpler and hence its power consumption became lower. Simpler structure and lower power will make the designed demodulator more suitable for use in an internal single chip design for a wireless implantable neural recording system. The proposed BPSK demodulator was implemented by Global Foundries 0.35 μm CMOS technology with a 3.3 V power supply. The designed chip area is only 0.07 mm2 and the power consumption is 0.5 mW. The test results show that it can work correctly.
基于MATLAB的交流电源频率调节环路仿真%Simulation of Frequency Regulation Loop for AC Power Supply Based on MATLAB
Institute of Scientific and Technical Information of China (English)
刘爱元; 刘持胜; 戴洪德
2013-01-01
Based on the introduction of components and principles of frequency regulation loop of constant fre⁃quency AC power supply, mathematic model of frequency modulation system was established. In this paper, the simulation with parameters changed under the state of middling rotate speed and middling load of the engine was discussed with emphasis. The simulation results showed that the change of system parameters would affect the dynamic and static characteristics of the system. The simulation results have good application value.% 在介绍某型恒频交流电源频率调节环路的组成和工作原理的基础上，分析了频率调节环路各组成部分的数学模型，建立了频率调节环路总的数学模型。文章重点讨论了某型发动机在中转速中负载状态下，改变滤波整形放大电路频率调节环路前向通道和反馈通道参数对系统动静态特性产生的影响。利用MATLAB仿真工具对系统进行了变参数仿真，得出了相应的仿真曲线，并对仿真结果进行了动静态特性分析。该仿真结果具有很好的应用价值。
Optimum modulation and demodulation matrices for solar polarimetry.
del Toro Iniesta, J C; Collados, M
2000-04-01
Both temporal and/or spatial modulation are mandatory in current solar polarimetry [Appl. Opt. 24, 3893 (1985); 26, 3838 (1987)]. The modulating and demodulating processes are mathematically described by matrices O and D, respectively, on whose structure the accuracy of Stokes parameter measurements depend. We demonstrate, based on the definition of polarimetric efficiency [Instituto de Astrofísica de Canarias Internal Report (1994); ASP Conf. Ser. 184, 3 (1999)], that the maximum efficiencies of an ideal polarimeter are unity for Stokes I and for (Q(2) + U(2) + V(2))(1/2) and that this occurs if and only if O(T)O is diagonal; given a general (possibly nonideal) modulation matrix O, the optimum demodulation matrix turns out to be D = (O(T)O)(-1)O(T); and the maximum efficiencies in the nonideal case are given by the rms value of the column elements of matrix O and are reached by modulation matrices such that O(T)O is diagonal. From these analytical results we distill two recipes useful in the practical design of polarimeters. Their usefulness is illustrated by discussing cases of currently available solar polarimeters. Although specifically devoted to solar polarimetry, the results here may be applied in practically all other branches of science for which polarimetric measurements are needed.
Soft demodulation to the optical pulse position modulated signals
Zhou, Tian-hua; Chen, Wei-biao
2009-07-01
The optical Pulse Position Modulation (PPM) is applied widely in Free Space Optical communication (FSO) with the low average power and the high peak power. The transmitted PPM information depends on the location of the coming optical pulse signals in fixed period. Both receiver and transmitter should been kept in time slot synchronization and frame synchronization in demodulation. Because the channel is very complex, the received optical pulse width will be stretched randomly. We design and realize one digital PPM modulation receiver with high sensitivity using the technology of PMT, A/D converter, and DSP. It is suitable to the total digital optical receiver with random time slots and random pulse width. The paper will mainly discuss the realization of the soft demodulation behind A/D converter. The key of PPM digital soft modulation is the establishment of the synchronization that involves the segment synchronization, the fame synchronization and the bit synchronization. The synchronization can be obtained by seeking for the frame head in data frames. Based on the estimation of received waveform characteristics, we adopt a matched filter without the best factors firstly. Thereafter, their errors will be self-adapted while finding the synchronization head. Considering the real-time need, we choose the reduced mode of maximum likelihood function judgment finally. In the experiments, results with high sensitivity and low bit error rate have been achieved.
Barbaro, V.; Bartolini, P.; Calcagnini, G.; Censi, F.; Beard, B.; Ruggera, P.; Witters, D.
2003-06-01
The aim of this study was to investigate the mechanisms by which the radiated radiofrequency (RF) GSM (global system for mobile communication) signal may affect pacemaker (PM) function. We measured the signal at the output of the sensing amplifier of PMs with various configurations of low-pass filters. We used three versions of the same PM model: one with a block capacitor which short circuits high-frequency signals; one with a ceramic feedthrough capacitor, a hermetically sealed mechanism connecting the internal electronics to the external connection block, and one with both. The PMs had been modified to have an electrical shielded connection to the output of the sensing amplifier. For each PM, the output of the sensing amplifier was monitored under exposure to modulated and non-modulated RF signals, and to GSM signals (900 and 1800 MHz). Non-modulated RF signals did not alter the response of the PM sensing amplifier. Modulated RF signals showed that the block capacitor did not succeed in short circuiting the RF signal, which is somehow demodulated by the PM internal non-linear circuit elements. Such a demodulation phenomenon poses a critical problem because digital cellular phones use extremely low-frequency modulation (as low as 2 Hz), which can be mistaken for normal heartbeat.
Effect of self-demodulation on the subharmonic response of contrast agent microbubbles.
Daeichin, V; Faez, T; Renaud, G; Bosch, J G; van der Steen, A F W; de Jong, N
2012-06-21
Subharmonic (SH) emission from the ultrasound contrast agent (UCA) is of interest since it is produced only by the UCA and not by tissue, opposite to harmonic imaging modes where both tissue and microbubble show harmonics. In this work, the use of the self-demodulation (S-D) signal as a means of microbubble excitation at the SH frequency to enhance the SH emission of UCA is studied. The S-D wave is a low-frequency signal produced by the weak nonlinear propagation of an ultrasound wave. It is proportional to the second time derivative of the squared envelope of the transmitted signal. A diluted population of BR14 UCA (Bracco Research SA, Geneva, Switzerland) was insonified by a 10 MHz transducer focused at 76 mm firing bursts with different envelopes, durations and peak pressure amplitudes. The center frequency of the S-D signal changes from low frequencies (around 0.5 MHz) toward the transmitted frequency (10 MHz) by modifying the envelope function from gaussian to rectangular. For 6 and 20 transmitted cycles, the SH response is enhanced up to 25 and 22 dB, respectively, when using a rectangular envelope instead of a gaussian one. The experimental results are confirmed by the numerical simulation. The effects of the excitation duration and pressure amplitude are also studied. This study shows that a suitable design of the envelope of the transmit excitation to generate a S-D signal at the SH frequency can enhance the SH emission of UCA, and the SH imaging is feasible at high frequencies with a shorter transmit burst (six-cycle) and low acoustic pressure (∼100 KPa).
Directory of Open Access Journals (Sweden)
A. V. Volkov
2015-07-01
Full Text Available Subject of Research. Important feature of homodyne demodulation method based on the arctangent function approach is the phase shift between the reference oscillator signal and the interference signal. This phenomenon is caused by propagation delays of impulses in the optical interferometric sensor scheme and the analog low-pass filter in front of the phase modulator which produces the reference oscillator signal phase delay. There is multiplying of the reference oscillator signal and the interference signal in this homodyne demodulation scheme during its processing, and the phase shift between these signals leads to a distortion of the output signal. This paper deals with the findings of the phase shift influence of the reference oscillator signal by the output signal of the demodulation scheme at various parameters of the interference signal. Estimation of required accuracy is given of the phase shift compensation for the specified level distortion of the output signal. Method. Mathematical model is proposed in MATLAB. In this model, interference signal with changing parameters by a set of rules is passed through the considered demodulation scheme. This gives the possibility to obtain the dependences of the output signal amplitude from the reference oscillator signal phase shift, the operating point of the interferometer, the depth of phase modulation and amplitude of the measured phase signal. Results obtained during the simulation showed the need to compensate the reference oscillator signal phase shift. To assess this shift in the current homodyne demodulation scheme the original method of its determination has been proposed. The method is based on the transmission of the interference signal and the oscillator signal via one and the same band-pass filter that separates the phase modulation carrier frequency. According to the phase delay between the receiving signals, the value of the reference oscillator signal phase shift can be judged on
The Design of Phase-Locked-Loop Circuit for Precision Capacitance Micrometer
Directory of Open Access Journals (Sweden)
Li Shujie
2016-01-01
Full Text Available High precision non-contact micrometer is normally divided into three categories: inductance micrometer, capacitance micrometer and optical interferometer micrometer. The capacitance micrometer is widely used because it has high performance to price ratio. With the improvement of automation level, precision of capacitance micrometer is required higher and higher. Generally, capacitance micrometer consists of the capacitance sensor, capacitance/voltage conversion circuit, and modulation and demodulation circuits. However, due to the existing of resistors, capacitors and other components in the circuit, the phase shift of the carrier signal and the modulated signal might occur. In this case, the specific value of phase shift cannot be determined. Therefore, error caused by the phase shift cannot be eliminated. This will reduce the accuracy of micrometer. In this design, in order to eliminate the impact of the phase shift, the phase-locked-loop (PLL circuit is employed. Through the experiment, the function of tracking the input signal phase and frequency is achieved by the phase-locked-loop circuit. This signal processing method can also be applied to tuber electrical resistance tomography system and other precision measurement circuit.
Millimeter-Wave Heterodyne Six-Port Receiver： New Implementation and Demodulation Results
Institute of Scientific and Technical Information of China (English)
D Hammou; E. Moldovan; S.O. Tatu
2011-01-01
This paper presents a new implementation of a millimeter-wave heterodyne receiver based on six-port technology. The six-port model is implemented in Advanced Design System （ADS） using S-parameter measurements for realistic advanced simulation of a short-range 60 GHz wireless link. Millimeter-wave frequency conversion is performed using a six-port down-converter. The second frequency conversion is performed using conventional means because of low IF. A comparison between the proposed receiver and a conventional balanced millimeter-wave mixer shows that the proposed receiver improves conversion loss and I/Q phase stability over the local oscillator （LO） and RF power ranges. The results of demodulating a V-band quadrature phase-shift keying （QPSK） signal at a high data rate of 100 Mb/s-1 Gb/s are discussed. The results of a bit error rate （BER） and error vector magnitude （EVM） analysis prove that the proposed architecture can be successfully used for wireless link transmission up to 10 m.
Sweep Distortion Removal from THz Images via Blind Demodulation
Aghasi, Alireza; Redo-Sanchez, Albert; Romberg, Justin; Raskar, Ramesh
2016-01-01
Heavy sweep distortion induced by alignments and inter-reflections of layers of a sample is a major burden in recovering 2D and 3D information in time resolved spectral imaging. This problem cannot be addressed by conventional denoising and signal processing techniques as it heavily depends on the physics of the acquisition. Here we propose and implement an algorithmic framework based on low-rank matrix recovery and alternating minimization that exploits the forward model for THz acquisition. The method allows recovering the original signal in spite of the presence of temporal-spatial distortions. We address a blind-demodulation problem, where based on several observations of the sample texture modulated by an undesired sweep pattern, the two classes of signals are separated. The performance of the method is examined in both synthetic and experimental data, and the successful reconstructions are demonstrated. The proposed general scheme can be implemented to advance inspection and imaging applications in THz ...
QPSK Modulator and Demodulator Using FPGA for SDR
Directory of Open Access Journals (Sweden)
Mandadkar Mukesh
2014-04-01
Full Text Available A software-defined radio (SDR allows for digital communication systems to simply accept more complicated coding and modulation technologies, which is enormously vital in meeting the ever-increasing demands of the wireless communication industry. An SDR has been constructed, using the Simulink tool, and implemented on the SPARTEN-3E Field Programmable Gate Array (FPGA development kit. The modulation scheme used in the system is Quadrature Phase-Shift Keying (QPSK. In the first step to realize the whole modulation and demodulation schemes using MATLAB Simulink. The format of a VHDL program is built around the concept of BLOCKS which are the basic building units of a VHDL design. The results showed that the proposed method can greatly improve the developing efficiency, shorten developing period and reduce costs.
Demodulation improvement analysis of FEC quasi-coherent CPM
Norris, James A.; Nieto, John W.
2014-05-01
Continuous Phase Modulation (CPM) schemes are advantageous for low-power radios. The constant envelope transmit signal is more efficient for both linear and non-linear amplifier architectures. A standard, coherent CPM receiver can take advantage of modulation memory and is more complex than a coherent Phase Shift Keyed receiver. But the CPM signal can be demodulated non-coherently and still take advantage of the trellis structure inherent in the modulation. Prior analyses of several different non-coherent CPM schemes have been provided with many providing coherent or near coherent performance. In this paper we will discuss a new, reduced complexity decoder that improves upon the noncoherent performance. In addition, this new algorithm generates soft decision metrics that allow the addition of a forward error correction scheme (an outer code) with coherent equivalent performance gains.
Digital PSK to BiO-L demodulator for 2 sup nx(bit rate) carrier
Shull, T. A.
1979-01-01
A phase shift key (PSK) to BiO-L demodulator which uses standard digital integrated circuits is discussed. The demodulator produces NRZ-L, bit clock, and BiO-L outputs from digital PSK input signals for which the carrier is a 2 to the Nth multiple of the bit rate. Various bit and carrier rates which are accommodated by changing various component values within the demodulator are described. The use of the unit for sinusoidal inputs as well as digital inputs is discussed.
A demodulation method of Temperature-Spectrum width based on Chirped fiber grating
Directory of Open Access Journals (Sweden)
Chen Si
2016-01-01
Full Text Available Based on spectral reflection characteristics of chirped FBGs, a demodulation method for complex temperature fields is proposed in this paper. Relationships between the reflective spectrums and the temperatures are investigated through theoretical analyses. Testing results are acquired from a FBG sensing model which is designed according to the newly-developed method. A simulation to get the relationships between reflective spectrums and temperatures is set which shows that this demodulation method is feasible and its demodulation precision is beyond +/−1°C. The method provides a new method for analyzing complex temperature fields.
Performance of quasi-optimum digital FM demodulators for fading channels
Dharamsi, M. T.; Gupta, S. C.
1975-01-01
This paper deals with the problem of digital demodulation of FM signals transmitted over Rayleigh and Rician fading channels. The Rayleigh and Rician fading channels are represented by two quadrature multiplicative nonzero mean white Gaussian processes in addition to an additive zero-mean white Gaussian noise. Quasi-optimum digital baseband demodulation algorithms using various nonlinear estimation techniques are derived. The digital demodulator structures are then simulated on a digital computer for an FM system with first order message spectrum for various values of the parameters for Rayleigh and Rician channels.
Directory of Open Access Journals (Sweden)
Wei Luo
2017-05-01
Full Text Available The control system of a doubly-fed adjustable-speed pumped-storage hydropower plant needs phase-locked loops (PLLs to obtain the phase angle of grid voltage. The main drawback of a comb-filter-based phase-locked loop (CF-PLL is the slow dynamic response. This paper presents a modified comb-filter-based phase-locked loop (MCF-PLL by improving the pole-zero pattern of the comb filter, and gives the parameters’ setting method of the controller, based on the discrete model of MCF-PLL. In order to improve the disturbance resistibility of MCF-PLL when the power grid’s frequency changes, this paper proposes a frequency-adaptive modified, comb-filter-based, phase-locked loop (FAMCF-PLL and its digital implementation scheme. Experimental results show that FAMCF-PLL has good steady-state and dynamic performance under distorted grid conditions. Furthermore, FAMCF-PLL can determine the phase angle of the grid voltage, which is locked when it is applied to a doubly-fed adjustable-speed pumped-storage hydropower experimental platform.
Energy Technology Data Exchange (ETDEWEB)
Kohut, P. [Brookhaven National Lab., Upton, NY (United States)
1994-07-01
The major objective of the Surry internal flood analysis was to provide an improved understanding of the core damage scenarios arising from internal flood-related events. The mean core damage frequency of the Surry plant due to internal flood events during mid-loop operations is 4.8E-06 per year, and the 5th and 95th percentiles are 2.2E-07 and 1.8E-05 per year, respectively. Some limited sensitivity calculations were performed on three plant improvement options. The most significant result involves modifications of intake-level structure on the canal, which reduced core damage frequency contribution from floods in mid-loop by about 75%.
Energy Technology Data Exchange (ETDEWEB)
Yin, Yan
1999-06-15
The project is to design and bench test a multi-channel single shot transient electrical or optical pulses or pulse trains. A special gating function has been used to select a specific pulse for detail measurement. A study has been done to learn the dynamic physics in the recirculative loop. The proposed technique has been able to let signal circulate more than 1000 turns in the recirculative loop.
CMOS锁相环中快速鉴相鉴频器的设计%Design of Fast Phase/Frequency Detector for the CMOS Phase-Locked Loops
Institute of Scientific and Technical Information of China (English)
任正权; 李龙镇
2011-01-01
摘要：为了实现高速锁相环电路，通过分析经典CMOS锁相环的鉴相鉴频器，针对其延迟时间过长的问题，设计了可用于CMOS锁相环中的快速鉴相鉴频器．整个电路采用了0．13μmCMOS工艺，通过HSpice仿真软件测试表明，该快速鉴相鉴频器与经典鉴相鉴频器相比，延迟时间可以缩短一半．%To implement high speed phase-locked loops circuit, on the basis of analyzing the conventional phase/frequency detector of CMOS phase-locked loops, a fast phase/frequency detector is designed for the CMOS phase-locked loops to reduce the delay time. The circuit is designed by using the 0. 13 μm CMOS process and HSpice simulating results show that the designed fast phase/frequency detector can reduce half de- lay time.
Simultaneous Polarization Demultiplexing and Demodulation of PolMux-DPSK Signals in a Silicon Chip
DEFF Research Database (Denmark)
Huang, Bo; Ding, Yunhong; Ou, Haiyan;
2013-01-01
Simultaneous polarization demultiplexing and demodulation of PolMux-DPSK signals is demonstrated using a polarization splitter and rotator together with a single microring resonator on a silicon chip. System experimental results validate the concept....
Ma, Xudong
2008-01-01
In this paper, we consider the demodulation and equalization problem of differential Impulse Radio (IR) Ultra-WideBand (UWB) Systems with Inter-Symbol-Interference (ISI). The differential IR UWB systems have been extensively discussed recently. The advantage of differential IR UWB systems include simple receiver frontend structure. One challenge in the demodulation and equalization of such systems with ISI is that the systems have a rather complex model. The input and output signals of the systems follow a second-order Volterra model. Furthermore, the noise at the output is data dependent. In this paper, we propose a reduced-complexity joint demodulation and equalization algorithm. The algorithm is based on reformulating the nearest neighborhood decoding problem into a mixed quadratic programming and utilizing a semi-definite relaxation. The numerical results show that the proposed demodulation and equalization algorithm has low computational complexity, and at the same time, has almost the same error probabi...
The modulation and demodulation module of a high resolution MOEMS accelerometer
Jiao, Xufen; Bai, Jian; Lu, Qianbo; Lou, Shuqi
2016-02-01
A MOEMS accelerometer with high precision based on grating interferometer is demonstrated in this paper. In order to increase the signal-to-noise ratio (SNR) and accuracy, a specific modulator and an orthogonal phase-lock demodulator are proposed. Phase modulation is introduced to this accelerometer by applying a sinusoidal signal to a piezoelectric translator (PZT) amounted to the accelerometer. Phase demodulation module consists of a circuit design and a digital design. In the circuit design, the modulated light intensity signal is converted to a voltage signal and processed. In the digital part, the demodulator is mainly composed of a Band Pass Filter, two Phase-Sensitive Detectors, a phase shifter, and two Low Pass Filters based on virtual instrument. Simulation results indicate that this approach can decrease the noise greatly, and the SNR of this demodulator is 50dB and the relative error is less than 4%.
Zhang, Yan; Tang, Baoping; Liu, Ziran; Chen, Rengxiang
2016-02-01
Fault diagnosis of rolling element bearings is important for improving mechanical system reliability and performance. Vibration signals contain a wealth of complex information useful for state monitoring and fault diagnosis. However, any fault-related impulses in the original signal are often severely tainted by various noises and the interfering vibrations caused by other machine elements. Narrow-band amplitude demodulation has been an effective technique to detect bearing faults by identifying bearing fault characteristic frequencies. To achieve this, the key step is to remove the corrupting noise and interference, and to enhance the weak signatures of the bearing fault. In this paper, a new method based on adaptive wavelet filtering and spectral subtraction is proposed for fault diagnosis in bearings. First, to eliminate the frequency associated with interfering vibrations, the vibration signal is bandpass filtered with a Morlet wavelet filter whose parameters (i.e. center frequency and bandwidth) are selected in separate steps. An alternative and efficient method of determining the center frequency is proposed that utilizes the statistical information contained in the production functions (PFs). The bandwidth parameter is optimized using a local ‘greedy’ scheme along with Shannon wavelet entropy criterion. Then, to further reduce the residual in-band noise in the filtered signal, a spectral subtraction procedure is elaborated after wavelet filtering. Instead of resorting to a reference signal as in the majority of papers in the literature, the new method estimates the power spectral density of the in-band noise from the associated PF. The effectiveness of the proposed method is validated using simulated data, test rig data, and vibration data recorded from the transmission system of a helicopter. The experimental results and comparisons with other methods indicate that the proposed method is an effective approach to detecting the fault-related impulses
Demodulating the Response of Optical Fibre Long-Period Gratings: Genetic Algorithm Approach
Institute of Scientific and Technical Information of China (English)
P. S. André; R. A. Sá. Ferreira; C. M. L. Correia; H. Kalinowshy; XIN Xiang-Jun; J. L. Pinto
2006-01-01
@@ The extraction of the physical parameters of long period gratings from the spectral response is not an easy process. We present a demodulation technique to synthesize the physical parameters of a long period grating recorded in an optical fibre. The demodulation is achieved through the implementation of a genetic algorithm.The extracted parameters are in agreement with the typical values known for long period gratings.
Compact and Athermal DQPSK Demodulator with Silica-Based Planar Lightwave Circuit
Nasu, Yusuke; Sakamaki, Yohei; Hattori, Kuninori; Kamei, Shin; Hashimoto, Toshikazu; Saida, Takashi; Takahashi, Hiroshi; Inoue, Yasuyuki
We present a full description of a polarization-independent athermal differential quadrature phase shift keying (DQPSK) demodulator that employs silica-based planar lightwave circuit (PLC) technology. Silica-based PLC DQPSK demodulator has good characteristics including low polarization dependence, mass producibility, etc. However delay line interferometer (DLI) of demodulator had the large temperature dependence of its optical characteristics, so it required large power consumption to stabilize the chip temperature by the thermo-electric cooler (TEC). We previously made a quick report about an athermal DLI to reduce a power consumption by removing the TEC. In this paper, we focus on the details of the design and the fabrication method we used to achieve the athermal characteristics, and we describe the thermal stability of the signal demodulation and the reliability of our demodulator. We described two athermalization methods; the athermalization of the transmission spectrum and the athermalization of the polarization property. These methods were successfully demonstrated with keeping a high extinction ratio and a small footprint by introducing a novel interwoven DLI configuration. This configuration can also limit the degradation of the polarization dependent phase shift (PDf) to less than 1/10 that with the conventional configuration when the phase shifters on the waveguide are driven. We used our demodulator and examined its demodulation performance for a 43Gbit/s DQPSK signal. We also verified its long-term reliability and thermal stability against the rapid temperature change. As a result, we confirmed that our athermal demodulator performed sufficiently well for use in DQPSK systems.
Directory of Open Access Journals (Sweden)
Syedul Amin
2013-04-01
Full Text Available Both the Radio Frequency Identification (RFID and Wireless Fidelity (WiFi are popular and ubiquitous technologies. However, RFID is lagging behind due to vendor specific solutions and excessive reader cost. A WiFi compatible IEEE 802.11 RFID tag can eliminate the reader. A digital modulator and demodulator for the reader-less RFID tag in IEEE 802.11 protocol employing Direct Sequence Spread Spectrum (DSSS and Barker code are proposed in this paper. To generate the 11-bit Barker code, MOD-11 synchronous counter and encoder are designed by utilizing only four D flip-flops instead of preloading the code sequence in multiple registers. For modulation, data are multiplied with this Barker code and for demodulation, the received data are multiplied with the same Barker code. Designed in 0.18 µm CMOS technology, the minimum, average and maximum power consumptions are 3.64 nA, 17.64 µA and 7.61 mA, respectively. The simulation results show the correct functionality of the modulator and demodulator where 1 bit is spread to 11 bits and 11 bits received data are de-spread to 1 bit, respectively. The design would help to implement the modulator and demodulator for the reader-less RFID tag with resistance to multi-path fading and interference and covering the highest distance with lower Bit Error Rate (BER.
Ren, Qianyu; Li, Junhong; Hong, Yingping; Jia, Pinggang; Xiong, Jijun
2017-09-01
A new demodulation algorithm of the fiber-optic Fabry-Perot cavity length based on the phase generated carrier (PGC) is proposed in this paper, which can be applied in the high-temperature pressure sensor. This new algorithm based on arc tangent function outputs two orthogonal signals by utilizing an optical system, which is designed based on the field-programmable gate array (FPGA) to overcome the range limit of the original PGC arc tangent function demodulation algorithm. The simulation and analysis are also carried on. According to the analysis of demodulation speed and precision, the simulation of different numbers of sampling points, and measurement results of the pressure sensor, the arc tangent function demodulation method has good demodulation results: 1 MHz processing speed of single data and less than 1% error showing practical feasibility in the fiber-optic Fabry-Perot cavity length demodulation of the Fabry-Perot high-temperature pressure sensor.
Institute of Scientific and Technical Information of China (English)
王俊; 孙昕
2012-01-01
To meet the high dynamic environment, global navigation satellite system receivers often combine frequency-locked loop with phase-locked loop to track carrier. An improvement on cross-product automatic frequency control loop, which is commonly used, is proposed. The new loop adopts the switch between two identification methods. As a result, it can overcome the data ambiguity and expand the frequency discrimination range 4 times while maintaining the same tracking accuracy. The main factors affecting the tracking accuracy include noise tracking error and dynamic stress error. It is found that there is a greater gap between the traditional theory of thermal noise error and actual results. Using loop linear approximation and considering the relevance of noises in identification results, the new thermal noise tracking error equation is derived. The new value is less than one-fifth of traditional theoretical analysis. Finally, the analysis of frequency discrimination range and thermal noise tracking error is proved by simulation results.%为了适应高动态环境,导航接收机常采取锁频环和锁相环联合工作实现载波跟踪.对其中较常用的的叉积自动频率跟踪环提出改进,利用两种方法切换实现频率鉴别.改进后算法克服了数据位模糊,并且使鉴频范围扩大了4倍,同时保持跟踪精度不变.影响跟踪精度的因素主要包括热噪声误差和动态应力误差,经研究发现其中热噪声误差的传统理论分析结果与实际有较大差距.利用环路线性化近似处理,并且考虑鉴别噪声间的相关性,经重新推导得到锁频环路的热噪声跟踪误差低于传统理论分析结果的1/5.通过仿真对锁频环鉴频范围和热噪声跟踪误差分析的正确性进行了验证.
HIRFL数字化高频低电平控制系统研究%Research of Digital Low Level Radio Frequency Control System for HIRFL
Institute of Scientific and Technical Information of China (English)
丛岩; 许哲; 李刚; 王贤武; 孙列鹏; 仪孝平
2012-01-01
In order to ensure that the beam quality is well enough, we need to precisely control the frequen- cy, amplitude and phase of cavity electric field. Traditional control system consists of amplitude loop and phase loop. And these two loops control amplitude and phase stability respectively. The digital low level radio frequency （LLRF） system, which uses advanced digital control technology, needs only one feed-back loop to control amplitude and phase stability. The phase control precision and stability of the system are higher than the traditional control system. The LLRF system is based on field programmable gate array （FPGA） and digital signal processing （DSP）, and implemented by direct digital frequency synthesis （DDS） and digital orthogonal modulation and demodulation （I/Q） technology. The digital LLRF system has been tested in a long-term stability and high-power experiments. The amplitude deviation is lower than ± 1 , and phase control accuracy is within ±1.
Energy Technology Data Exchange (ETDEWEB)
Garcia-Juarez, A; Gomez-Colin, M R; Rojas-Hernandez, A G [Universidad de Sonora (Mexico); Zaldivar-Huerta, I E; Aguayo-Rodriguez, G [Instituto Nacional de Astrofisica, Optica y Electronica (Mexico); Rodriguez-Asomoza, J, E-mail: agarcia@cifus.uson.mx [Universidad de las Americas-Puebla (Mexico)
2011-01-01
An optical communications system using a couple microstrip antennas for distributing point to point analog TV with coherent demodulation based on optical heterodyne in close vicinity is reported in this paper. In the proposed experimental setup, two optical waves at different wavelengths are mixed and applied to a photodetector. Then a beat signal with a frequency equivalent to the spacing of the two wavelengths is obtained at the output of the photodetector. This signal corresponds to a microwave signal located at 1.25 GHz, which it is used as a microwave carrier in the transmitter and as a local oscillator in the receiver of our optical communication system. The feasibility of this technique is demonstrated transmitting a TV signal of 66-72 MHz.
García-Juárez, A.; Zaldívar-Huerta, I. E.; Aguayo-Rodríguez, G.; Rodríguez-Asomoza, J.; Gómez-Colín, M. R.; Rojas-Hernández, A. G.
2011-01-01
An optical communications system using a couple microstrip antennas for distributing point to point analog TV with coherent demodulation based on optical heterodyne in close vicinity is reported in this paper. In the proposed experimental setup, two optical waves at different wavelengths are mixed and applied to a photodetector. Then a beat signal with a frequency equivalent to the spacing of the two wavelengths is obtained at the output of the photodetector. This signal corresponds to a microwave signal located at 1.25 GHz, which it is used as a microwave carrier in the transmitter and as a local oscillator in the receiver of our optical communication system. The feasibility of this technique is demonstrated transmitting a TV signal of 66-72MHz.
Synchronous phase demodulation algorithm for conic carrier Hartmann topographer
Gonzalez, Adonai; Rivera, Mariano; Servin, Manuel; Legarda-Saenz, Ricardo; Dalmau, Oscar; Martinez, Amalia
2015-04-01
In this paper, a theoretical analysis of a new algorithm for measuring phase objects (PO) is presented. The algorithm analyses images captured with a modified Hartmann plate. The proposed method demodulates a signal with a conic-wavefront carrier by using synchronous interferometric techniques. Typically a Hartmann plate is a mask with an array of holes, the proposal is to replace those holes with a series of circular concentric rings created by a conic carrier, named Conic Hartmann plate mask (CHM). The proposed algorithm computes a dense correspondence between the pattern source and its interferogram on the PO. This dense correspondence is computed as the phase change of the refracted waveform with respect to the reference one. This approach is more robust than standard techniques that computes the center of each spot in order to estimate its position; which involves pattern recognition and segmentation tasks, something normal in a typical Hartmann test. We show in this work that the new method overcomes different problems such as irregular background illumination, spots overlapping with pupil border and spots matching due to rapid changes on the surface slopes. This work shows a general procedure for radial derivatives integration based on base functions. As far as the authors know, the here presented demonstration has not been reported before. In particular, we show that Zernike polynomials are suitable for PO. Numerical experiments with real and simulated data demonstrate the algorithm performance.
Evaluation of bit errors in different types demodulation discrete signals
Directory of Open Access Journals (Sweden)
V. M. Kychak
2015-12-01
Full Text Available Introduction. The introduction describes the main characteristics of bit errors. These sources of bit errors in discrete channels. Also listed scientists who worked on the study opportunities monitoring bit error in discrete channels. The main purpose of the article is to conduct research and theoretical modeling of processes in discrete channels to control error measurement and forecasting parameter BER bit error depending on the signal/noise ratio. Theoretical analysis. A comparison of some types of digital modulation for effective use in systems transmitting information. Comparisons were made using the correlation function, power spectral density and distance between signals. It was proved that through this you can control the real value of bit error (BER for each type of modulation. Important here is the dependence of the BER signal/noise ratio in the test communication channel. Determined that efficiency could be described bit error probability value of the output of the receiver, which is determined by the expression (4. Control parameters BER modulation in digital signals. At this paragraph the examples of control parameter BER at different modulation signals. The simulation results show that with an increase in the signal/noise bit error probability for different types of demodulation will decrease.
Measurement of epithermal neutrons by a coherent demodulation technique
Horiuchi, N; Takahashi, H; Kobayashi, H; Harasawa, S
2000-01-01
Epithermal neutrons have been measured using a neutron dosimeter via a coherent demodulation technique. This dosimeter consists of CsI(Tl)-photodiode scintillation detectors, four of which are coupled to neutron-gamma converting foils of various sizes. Neutron-gamma converting foils of In, Au and Co materials were used, each of which has a large capture cross section which peaks in the epithermal neutron energy region. The type of foil was selected according to the material properties that best correspond to the energy of the epithermal neutrons to be measured. In addition, the proposed technique was applied using Au-foils in order to measure the Cd ratio. The validity of the proposed technique was examined using an sup 2 sup 4 sup 1 Am-Be source placed in a testing stack of polyethylene blocks, and the results were compared with the theoretical values calculated by the Monte Carlo calculation. Finally, the dosimeter was applied for measuring epithermal neutrons and the Cd ratio in an experimental beam-tube o...
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)
Wielgosz, A.; Brzeziński, A.; Böhm, S.
2016-12-01
The complex demodulation (CD) algorithm is an efficient tool for extracting the diurnal and subdiurnal components of Earth rotation from the routine VLBI observations (Brzeziński, 2012). This algorithm was implemented by Böhm et al (2012b) into a dedicated version of the VLBI analysis software VieVs. The authors processed around 3700 geodetic 24-hour observing sessions in 1984.0-2010.5 and estimated simultaneously the time series of the long period components as well as diurnal, semidiurnal, terdiurnal and quarterdiurnal components of polar motion (PM) and universal time UT1. This paper describes the tests of the CD algorithm by checking consistency of the low frequency components of PM and UT1 estimated by VieVS CD and those from the IERS and IVS combined solutions. Moreover, the retrograde diurnal component of PM demodulated from VLBI observations has been compared to the celestial pole offsets series included in the IERS and IVS solutions. We found for all three components a good agreement of the results based on the CD approach and those based on the standard parameterization recommended by the IERS Conventions (IERS, 2010) and applied by the IERS and IVS. We conclude that an application of the CD parameterization in VLBI data analysis does not change those components of EOP which are included in the standard adjustment, while enabling simultaneous estimation of the high frequency components from the routine VLBI observations. Moreover, we deem that the CD algorithm can also be implemented in analysis of other space geodetic observations, like GNSS or SLR, enabling retrieval of subdiurnal signals in EOP from the past data.
Zhao, Dezun; Li, Jianyong; Cheng, Weidong; Wen, Weigang
2016-09-01
Multi-fault detection of the rolling element bearing under time-varying rotational speed presents a challenging issue due to its complexity, disproportion and interaction. Computed order analysis (COA) is one of the most effective approaches to remove the influences of speed fluctuation, and detect all the features of multi-fault. However, many interference components in the envelope order spectrum may lead to false diagnosis results, in addition, the deficiencies of computational accuracy and efficiency also cannot be neglected. To address these issues, a novel method for compound faults detection of rolling element bearing based on the generalized demodulation (GD) algorithm is proposed in this paper. The main idea of the proposed method is to exploit the unique property of the generalized demodulation algorithm in transforming an interested instantaneous frequency trajectory of compound faults bearing signal into a line paralleling to the time axis, and then the FFT algorithm can be directly applied to the transformed signal. This novel method does not need angular resampling algorithm which is the key step of the computed order analysis, and is hence free from the deficiencies of computational error and efficiency. On the other hand, it only acts on the instantaneous fault characteristic frequency trends in envelope signal of multi-fault bearing which include rich fault information, and is hence free from irrelevant items interferences. Both simulated and experimental faulty bearing signal analysis validate that the proposed method is effective and reliable on the compound faults detection of rolling element bearing under variable rotational speed conditions. The comprehensive comparison with the computed order analysis further shows that the proposed method produces higher accurate results in less computation time.
DEFF Research Database (Denmark)
Kim, T.-Y.; Hanawa, M.; Kim, Sun-Jong
2006-01-01
We propose and demonstrate a novel optical differential phase-shift keying (DPSK) demodulator with an optically tunable phase shifter. The proposed DPSK demodulator is implemented by using a pi-phase-shifted fiber Bragg grating and an Yb3+-Al3+ codoped optical fiber. A 10-Gb/s DPSK signal was suc...... was successfully demodulated by the proposed demodulator, showing clearly open eye diagrams as well as bit-error-free performance. Moreover, the phase of delayed optical signal can be tuned by the phase shifter that is controlled by a pumping light at around 980nm....
A FBG pulse wave demodulation method based on PCF modal interference filter
Zhang, Cheng; Xu, Shan; Shen, Ziqi; Zhao, Junfa; Miao, Changyun; Bai, Hua
2016-10-01
Fiber optic sensor embedded in textiles has been a new direction of researching smart wearable technology. Pulse signal which is generated by heart beat contains vast amounts of physio-pathological information about the cardiovascular system. Therefore, the research for textile-based fiber optic sensor which can detect pulse wave has far-reaching effects on early discovery and timely treatment of cardiovascular diseases. A novel wavelength demodulation method based on photonic crystal fiber (PCF) modal interference filter is proposed for the purpose of developing FBG pulse wave sensing system embedded in smart clothing. The mechanism of the PCF modal interference and the principle of wavelength demodulation based on In-line Mach-Zehnder interferometer (In-line MZI) are analyzed in theory. The fabricated PCF modal interferometer has the advantages of good repeatability and low temperature sensitivity of 3.5pm/°C from 25°C to 60°C. The designed demodulation system can achieve linear demodulation in the range of 2nm, with the wavelength resolution of 2.2pm and the wavelength sensitivity of 0.055nm-1. The actual experiments' result indicates that the pulse wave can be well detected by this demodulation method, which is in accordance with the commercial demodulation instrument (SM130) and more sensitive than the traditional piezoelectric pulse sensor. This demodulation method provides important references for the research of smart clothing based on fiber grating sensor embedded in textiles and accelerates the developments of wearable fiber optic sensors technology.
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.
DEFF Research Database (Denmark)
Guerrero Gonzalez, Neil; Zibar, Darko; Caballero Jambrina, Antonio;
2010-01-01
Highest reported bit rate of 2.5 Gb/s for optically phase modulated radio-over-fiber (RoF) link, employing digital coherent detection, is demonstrated. Demodulation of 3$,times,$ 2.5 Gb/s quadrature phase-shift keying modulated wavelength-division-multiplexed RoF channels is achieved after 79 km ...... of transmission through deployed fiber. Error-free performance (bit-error rate corresponding to $10^{{-}4}$) is achieved using a digital coherent receiver in combination with a $K$-means algorithm for radio-frequency phase recovery....
DEFF Research Database (Denmark)
Guerrero Gonzalez, Neil; Zibar, Darko; Caballero Jambrina, Antonio
2010-01-01
Highest reported bit rate of 2.5 Gb/s for optically phase modulated radio-over-fiber (RoF) link, employing digital coherent detection, is demonstrated. Demodulation of 3$,times,$ 2.5 Gb/s quadrature phase-shift keying modulated wavelength-division-multiplexed RoF channels is achieved after 79 km...... of transmission through deployed fiber. Error-free performance (bit-error rate corresponding to $10^{{-}4}$) is achieved using a digital coherent receiver in combination with a $K$-means algorithm for radio-frequency phase recovery....
Loop electrosurgical excisional procedure.
Mayeaux, E J; Harper, M B
1993-02-01
Loop electrosurgical excisional procedure, or LEEP, also known as loop diathermy treatment, loop excision of the transformation zone (LETZ), and large loop excision of the transformation zone (LLETZ), is a new technique for outpatient diagnosis and treatment of dysplastic cervical lesions. This procedure produces good specimens for cytologic evaluation, carries a low risk of affecting childbearing ability, and is likely to replace cryotherapy or laser treatment for cervical neoplasias. LEEP uses low-current, high-frequency electrical generators and thin stainless steel or tungsten loops to excise either lesions or the entire transformation zone. Complication rates are comparable to cryotherapy or laser treatment methods and include bleeding, incomplete removal of the lesion, and cervical stenosis. Compared with other methods, the advantages of LEEP include: removal of abnormal tissue in a manner permitting cytologic study, low cost, ease of acquiring necessary skills, and the ability to treat lesions with fewer visits. Patient acceptance of the procedure is high. Widespread use of LEEP by family physicians can be expected.
Shao, Xin; Liu, Fu-Gui; Chen, Wen-Liang
2013-12-01
According to the modulation signal applied on laser diodes, wavelength modulation spectroscopy (WMS) can be divided into continuous wave (CW) WMS and quasi-continuous wave (QCW) WMS. In order to deeply compare CW-WMS and QCW-WMS, we used a specific software-realized lock-in amplifier for continuous and quasi-continuous modulation signal demodulation. The invalid signal in quasi-continuous modulation spectrum was filtered off, and then the effective detection signal was demodulated to obtain the second harmonic signal (WMS-2f). It was compared with the 2f signal demodulated continuous laser modulation spectrum with software. The results show that while the same system parameters are set, the signal-to-noise of the quasi-continuous modulation spectrum is 5% higher than the continuous modulation spectrum with software demodulation measurements, and the detection limit is 11.3% lower. And without the invalid signal in quasi-continuous modulation spectrum, the standard WMS-2f signal can be demodulated, which has potential to be used for the investigation of gas absorption profile. This work has provided accurate reference for selections of the laser modulation spectroscopy.
Drago, Salvatore; Sebastiano, Fabio; Leenaerts, Dominicus Martinus Wilhelmus; Breems, Lucien Johannes; Nauta, Bram
2016-01-01
A low power frequency synthesiser circuit (30) for a radio transceiver, the synthesiser circuit comprising: a digital controlled oscillator configured to generate an output signal having a frequency controlled by an input digital control word (DCW); a feedback loop connected between an output and an
Energy Technology Data Exchange (ETDEWEB)
Warne, Larry Kevin; Lucero, Larry Martin; Langston, William L.; Salazar, Robert Austin; Coleman, Phillip Dale; Basilio, Lorena I.; Bacon, Larry Donald
2012-05-01
This report estimates inductively-coupled energy to a low-impedance load in a loop-to-loop arrangement. Both analytical models and full-wave numerical simulations are used and the resulting fields, coupled powers and energies are compared. The energies are simply estimated from the coupled powers through approximations to the energy theorem. The transmitter loop is taken to be either a circular geometry or a rectangular-loop (stripline-type) geometry that was used in an experimental setup. Simple magnetic field models are constructed and used to estimate the mutual inductance to the receiving loop, which is taken to be circular with one or several turns. Circuit elements are estimated and used to determine the coupled current and power (an equivalent antenna picture is also given). These results are compared to an electromagnetic simulation of the transmitter geometry. Simple approximate relations are also given to estimate coupled energy from the power. The effect of additional loads in the form of attached leads, forming transmission lines, are considered. The results are summarized in a set of susceptibility-type curves. Finally, we also consider drives to the cables themselves and the resulting common-to-differential mode currents in the load.
Zhang, Hongtao; Yang, Shangming; Fan, Lingling; Wang, Pengfei; Zhao, Xilin; Wang, Zhenhua; Cui, Hong-Liang
2010-04-01
In this paper we report a scheme of low-cost, small-size differential electrical converter to change analog trigger signals into digital trigger signals. This converter successfully resolves the incompatibility between the digital trigger mode of NI (National Instruments) data acquisition card PCI 5105 in Measurement Studio development environment for a demodulator and the requirement from instability of spectra of fiber Bragg grating (FBG) sensors. The instability is caused by intrinsic drifts of FFP-TF inside this high speed demodulator. The obtained results of frequency response about the converter have clearly demonstrated that this method is effective when the frequency of trigger signal is less than 3,000 Hz. This converter can satisfy the current requirements of demodulator based on FFP-TF, since mostly actual working scanning frequency of FFP-TF is less than 1,000 Hz. This method may be recommended to resolve similar problems for other NI customers who have developed their data acquisition system based on Measurement Studio.
Directory of Open Access Journals (Sweden)
Laura eRay
2015-09-01
Full Text Available A spindle detection method was developed that: 1 extracts the signal of interest (i.e., spindle-related phasic changes in sigma relative to ongoing background sigma activity using complex demodulation, 2 accounts for variations of spindle characteristics across the night, scalp derivations and between individuals, and 3 employs a minimum number of sometimes arbitrary, user-defined parameters. Complex demodulation was used to extract instantaneous power in the spindle band. To account for intra- and inter-individual differences, the signal was z-score transformed using a 60s sliding window, per channel, over the course of the recording. Spindle events were detected with a z-score threshold corresponding to a low probability (e.g., 99th percentile. Spindle characteristics, such as amplitude, duration and oscillatory frequency, were derived for each individual spindle following detection, which permits spindles to be subsequently and flexibly categorized as slow or fast spindles from a single detection pass. Spindles were automatically detected in 15 young healthy subjects. Two experts manually identified spindles from C3 during Stage 2 sleep, from each recording; one employing conventional guidelines, and the other, identifying spindles with the aid of a sigma (11-16 Hz filtered channel. These spindles were then compared between raters and to the automated detection to identify the presence of true positives, true negatives, false positives and false negatives. This method of automated spindle detection resolves or avoids many of the limitations that complicate automated spindle detection, and performs well compared to a group of non-experts, and importantly, has good external validity with respect to the extant literature in terms of the characteristics of automatically detected spindles.
Digital Readout System for Micromachined Gyroscope and Analysis for its Demodulation Algorithm
Institute of Scientific and Technical Information of China (English)
ZHOU Bin; GAO Zhong-yu; CHEN Huai; ZHANG Rong; CHEN Zhi-yong
2006-01-01
A new digital readout system for micromachined gyroscope has been proposed to implement flexible parameter adiustment,improve the control performance of gyroscope,and make error compensation.By digitalizing the output of the gyroscope,this system uses a floatingtype digital signal processor(DSP)to process the signal demodulation and achieve the feedback conffol of the gyroscope.Therefore.the small change of capacitance in the micromachined gyroscope Can be detected.A new demodulation algorithm of least mean square demodulation(LMSD)has been developed inside DSP Simulation and measurement results show that LMSD Can improve 29%of the noise performance compared with the typical multiplication method.In air pressure.a kind ofvibration-wheel micmmachined over the 100-Hz bandwidth by using this digital readout technology.
A simple delay-line 4-PPM demodulator with near-optimum performance.
Stevens, M L; Boroson, D M
2012-02-27
We describe a simple 4-PPM demodulator that uses analog delay lines and simple 1-bit comparators to determine the least-significant bit and most-significant bit of the 4-PPM encoded data without additional digital signal processing. We show that with good optical filtering the comparator-based demodulator can theoretically operate with sensitivity only 0.23 dB from the optimum 4-ary receiver. We describe as an example of this approach the demodulator built for the Lunar Laser Communication Demonstration and show measured performance within 1.1 dB of the expected sensitivity. The technique is extendable to higher-order, and higher-symbol-rate orthogonal modulation formats.
Multi-Channel 40 Gbit/s NRZ-DPSK demodulation using a single silicon microring resonator
DEFF Research Database (Denmark)
Ding, Yunhong; Xu, Jing; Peucheret, Christophe;
2010-01-01
We demonstrate simultaneous demodulation of multiple 40 Gbit/s WDM NRZ-DPSK channels using a single silicon microring resonator with FSR of 100 GHz. Bit error measurements show very good performances for both through and drop demodulations for all channels...
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.
PWM Switching Frequency Effects on Eddy Current Sensors for Magnetically Suspended Flywheel Systems
Jansen, Ralph; Lebron, Ramon; Dever, Timothy P.; Birchenough, Arthur G.
2003-01-01
A flywheel magnetic bearing (MB) pulse width modulated power amplifier (PWM) configuration is selected to minimize noise generated by the PWMs in the flywheel position sensor system. Two types of noise are addressed: beat frequency noise caused by variations in PWM switching frequencies, and demodulation noise caused by demodulation of high order harmonics of the switching voltage into the MB control band. Beat frequency noise is eliminated by synchronizing the PWM switch frequencies, and demodulation noise is minimized by selection of a switching frequency which does not have harmonics at the carrier frequency of the sensor. The recommended MB PWM system has five synchronized PWMs switching at a non-integer harmonic of the sensor carrier.
Zhou, Kejiang; Rao, Qi; Zhang, Minjie; Hu, Keke; Ruan, Yefeng
2017-09-01
An analog method to modulate and demodulate fiber-optic interferometric sensors employing a linear variable differential transformer signal conditioner to generate sine modulation wave and demodulate phase-modulated signal from the photodetector’s output is presented in this letter. No external lock-in amplifiers or digital components are used in this design. All the necessary components for signal processing are integrated in a single analog electronic microchip AD698, which reduces the system’s complexity significantly. After implementation on an interferometric fiber-optic gyroscope as an example, this method demonstrates a bias stability of 0.063 deg h-1 (i.e. 0.220 µrad).
PGC digital real-time demodulation system of fiber laser hydrophone%光纤激光水听器的PGC实时全数字解调系统
Institute of Scientific and Technical Information of China (English)
李玉; 黄俊斌; 谢顺依; 顾宏灿; 李日忠; 谭波
2012-01-01
The PGC demodulation principle of fiber laser hydrophone based on Michelson interferometer was introduced. Then, mathematical deductions and simulations were carried out through which to analyze the frequency difference between the modulation signal and the mixing frequency signal. The difference is one of the error-induced factors. To solve this problem. A resolution was provided for designing a digital real time demodulation system with sampling rate of 1 MHz based on DSP by using PGC method. An experiment was done on the demodulation of an acoustic signal with the frequency of 800 Hz. The result shows that the waveforms of demodulated acoustic signal are ideal.%概述了基于麦克尔逊干涉仪的光纤激光水听器的相位载波零差法(PGC)调制解调原理,通过数学推导及仿真,分析了调制信号和混频信号的频差是导致全数字化解调结果错误的主要因素之一.针对该诱导因素提供了可行的解决方案,并实现了基于DSP的1 MHz采样频率下使用PGC方法的全数字实时解调系统.对低频水声波段800Hz水声信号进行解调,实验结果表明:解调信号波形良好.
A True Open-Loop Synchronization Technique
DEFF Research Database (Denmark)
Golestan, Saeed; Vidal, Ana; Yepes, Alejandro G.
2016-01-01
to worsen in the presence of frequency drifts. To deal with this problem, two approaches are often recommended in the literature: Adapting OLS techniques to grid frequency variations by feeding back the frequency estimated by them or using the frequency estimated by a secondary frequency detector...... in a parallel manner. In the presence of the frequency feedback loop, nevertheless, the OLS technique may not be truly open-loop, which makes a deep study of stability necessary. Using the secondary frequency detector, on the other hand, increases the computational effort and implementation complexity. Another...
Improving the Angular Resolution of Coded-Mask Telescopes by Direct Demodulation
Institute of Scientific and Technical Information of China (English)
Zong-Jun Shen; Jian-Feng Zhou
2008-01-01
We develop a new procedure to improve the angular resolution of coded-mask telescopes by the Direct Demodulation Method (DDM). DDM has been applied to both real and simulated data of INTEGRAL/IBIS. The angular resolution of IBIS/ISGRI has been improved from about 13' to 2'.
Zhao, Yanshuang; Liu, Yanlei; Zhang, Jianzhong; Yang, Jun; Canning, John; Peng, G. D.; Chen, Yujin; Yuan, Libo
2015-09-01
We propose a simultaneous demodulation scheme of polarization mode coupling and fiber Bragg grating in a polarization maintaining fiber based on a white light interferometer. A polarization maintaining fiber with two inscribed fiber Bragg gratings is used to demonstrate the feasibility.
Elastic envelope inversion using multicomponent seismic data without low frequency
2014-01-01
Low frequency is a key issue to reduce the nonlinearity of elastic full waveform inversion. Hence, the lack of low frequency in recorded seismic data is one of the most challenging problems in elastic full waveform inversion. Theoretical derivations and numerical analysis are presented in this paper to show that envelope operator can retrieve strong low frequency modulation signal demodulated in multicomponent data, no matter what the frequency bands of the data is. With the be...
Energy Technology Data Exchange (ETDEWEB)
Chu, T.L.; Musicki, Z.; Kohut, P.; Yang, J.; Bozoki, G.; Hsu, C.J.; Diamond, D.J. [Brookhaven National Lab., Upton, NY (United States); Bley, D.; Johnson, D. [PLG Inc., Newport Beach, CA (United States); Holmes, B. [AEA Technology, Dorset (United Kingdom)] [and others
1994-06-01
Traditionally, probabilistic risk assessments (PRA) of severe accidents in nuclear power plants have considered initiating events potentially occurring only during full power operation. Some previous screening analyses that were performed for other modes of operation suggested that risks during those modes were small relative to full power operation. However, more recent studies and operational experience have implied that accidents during low power and shutdown could be significant contributors to risk. Two plants, Surry (pressurized water reactor) and Grand Gulf (boiling water reactor), were selected as the plants to be studied. The objectives of the program are to assess the risks of severe accidents initiated during plant operational states other than full power operation and to compare the estimated core damage frequencies, important accident sequences and other qualitative and quantitative results with those accidents initiated during full power operation as assessed in NUREG-1150. The scope of the program includes that of a level-3 PRA. In phase 2, mid-loop operation was selected as the plant configuration to be analyzed based on the results of the phase 1 study. The objective of the phase 2 study is to perform a detailed analysis of the potential accident scenarios that may occur during mid-loop operation, and compare the results with those of NUREG-1150. The scope of the level-1 study includes plant damage state analysis, and uncertainty analysis. Volume 1 summarizes the results of the study. Internal events analysis is documented in Volume 2. It also contains an appendix that documents the part of the phase 1 study that has to do with POSs other than mid-loop operation. Internal fire and internal flood analyses are documented in Volumes 3 and 4. A separate study on seismic analysis, documented in Volume 5, was performed for the NRC by Future Resources Associates, Inc. Volume 6 documents the accident progression, source terms, and consequence analysis.
Energy Technology Data Exchange (ETDEWEB)
Chu, T.L.; Musicki, Z.; Kohut, P.; Yang, J.; Bozoki, G.; Hsu, C.J.; Diamond, D.J.; Wong, S.M. [Brookhaven National Lab., Upton, NY (United States); Bley, D.; Johnson, D. [PLG Inc., Newport Beach, CA (United States)] [and others
1994-06-01
Traditionally, probabilistic risk assessments (PRA) of severe accidents in nuclear power plants have considered initiating events potentially occurring only during full power operation. Some previous screening analyses that were performed for other modes of operation suggested that risks during those modes were small relative to full power operation. However, more recent studies and operational experience have implied that accidents during low power and shutdown could be significant contributors to risk. Two plants, Surry (pressurized water reactor) and Grand Gulf (boiling water reactor), were selected as the plants to be studied. The objectives of the program are to assess the risks of severe accidents initiated during plant operational states other than full power operation and to compare the estimated core damage frequencies, important accident sequences and other qualitative and quantitative results with those accidents initiated during full power operation as assessed in NUREG-1150. The scope of the program includes that of a level-3 PRA. In phase 2, mid-loop operation was selected as the plant configuration to be analyzed based on the results of the phase 1 study. The objective of the phase 2 study is to perform a detailed analysis of the potential accident scenarios that may occur during mid-loop operation, and compare the results with those of NUREG-1150. The scope of the level-1 study includes plant damage state analysis, and uncertainty analysis. Volume 1 summarizes the results of the study. Internal events analysis is documented in Volume 2. It also contains an appendix that documents the part of the phase 1 study that has to do with POSs other than mid-loop operation. Internal fire and internal flood analyses are documented in Volumes 3 and 4. A separate study on seismic analysis, documented in Volume 5, was performed for the NRC by Future Resources Associates, Inc. Volume 6 documents the accident progression, source terms, and consequence analysis.
Design and Development of Amplitude and phase measurement of RF signal with Digital I-Q Demodulator
Soni, Dipal; Rajnish, Kumar; Verma, Sriprakash; Patel, Hriday; Trivedi, Rajesh; Mukherjee, Aparajita
2017-04-01
ITER-India, working as a nodal agency from India for ITER project [1], is responsible to deliver one of the packages, called Ion Cyclotron Heating & Current Drive (ICH&CD) - Radio Frequency Power Sources (RFPS). RFPS is having two cascaded amplifier chains (10 kW, 130 kW & 1.5 MW) combined to get 2.5 MW RF power output. Directional couplers are inserted at the output of each stage to extract forward power and reflected power as samples for measurement of amplitude and phase. Using passive mixer, forward power and reflected power are down converted to 1MHz Intermediate frequency (IF). This IF signal is used as an input to the Digital IQ Demodulator (DIQDM). DIQDM is realized using National Instruments make PXI hardware & LabVIEW software tool. In this paper, Amplitude and Phase measurement of RF signal with DIQDM technique is described. Also test results with dummy signals and signal generated from low power RF systems is discussed here.
Wireless fiber laser sensor combining photonic generation beat frequency demodulation technology
Liu, Shengchun; Gu, Rong; Yu, Xiujuan; Yin, Zuowei; Chen, Xiangfei
2011-12-01
A simple wireless-fiber laser sensor is proposed base on directly photonic generation of microwave beat signal. In this scheme, a multi-longitudinal modes fiber laser is formed by two fiber Bragg gratings and a section of erbium-doped fiber. Two same 2G-GSM mobile antennas are used as wireless transmitter and receiver. By this method, the real-time monitoring of fiber laser sensors can be achieved through over ultra-long distance. This technique offers a simple, all-electrical and cheap way for fiber sensor information accessing wireless net. The experiment result shows the root mean square deviations of the sensor are about 4.7 μɛ and 6.7 μɛ at 2.38 GHz before and after wireless transmission, respectively.
Lin, Jiachuan; Xi, Lixia; Li, Jianrui; Zhang, Xiaoguang; Zhang, Xia; Niazi, Shahab Ahmad
2014-04-07
In this paper, an improved multi-carrier generation scheme based on single-side-band recirculating frequency shifter with optical finite impulse response (FIR) filter for amplified spontaneous emission (ASE) noise suppression is proposed and experimentally demonstrated. The carrier-to-noise-ratio (CNR) instead of tone-to-noise-ratio (TNR) is introduced to more reasonably and exactly evaluate the signal-to-noise-ratio of a multi-carrier source with non-flat noise floor. We have experimentally attain the worst case CNR of 22.5dB and 19.1dB for generated 50 and 69 flat low noise carriers, which has shown significant improvement than the previous cited works based on recirculating frequency shifter.
Institute of Scientific and Technical Information of China (English)
刘桂花; 曹小娇; 王卫
2015-01-01
One of the main electrical characteristics of weak grid is the high grid impedance, which will easily lead to grid voltage waveform distortion. Distorted grid voltage can resultin deviation or failure of the phase-locked loop of photovoltaic (PV) inverter, and power quality will deteriorate. In order to tackle this problem, targeting on the LC-type PV inverter,a synchronization method is proposed based on the second order generalized integrator frequency locked loop (SOGI-FLL). Initially, the impact of various grid states, especially the weak grid, on the inverter is analyzed. Then the operation principle of SOGI-FLL and its implementation method are set forth in detail. Simulation and experimental results demonstrate the validity of this synchronization method in grid voltage disturbance and zero-crossing oscillation. This synchronization method has strong robustness and adaptability for grid voltage changes. Compared with the conventional zero-crossing synchronization method, the SOGI-FLL synchronization method can improve the reliability of grid-connected PV inverters under weak grid.%弱电网的主要电气特性之一为高电网阻抗.高电网阻抗易导致电网电压波形畸变,畸变的电网电压会使光伏并网逆变器锁相环出现偏差甚至失效,并导致并网电能质量变差.针对这一问题,以LC型单相光伏并网逆变器为研究对象,提出采用基于2阶广义积分器锁频环(second order generalized integrator frequency locked loop,SOGI-FLL)同步方法来实现逆变器与弱电网的同步.在分析不同电网状态尤其是弱电网对逆变器影响的基础上,详细阐述SOGI-FLL的工作原理和实现方法.仿真和实验结果表明,该同步方法在电网电压扰动及过零点震荡情况下均可稳定可靠工作,对电网电压变化具有较强的鲁棒性和适应性,与传统过零同步方法相比,SOGI-FLL同步方法可提高弱电网下光伏并网逆变器的可靠性.
基于WNN的环形球栅扭矩传感器的信号解调%Signal demodulation of ring ball grating torque sensor based on WNN
Institute of Scientific and Technical Information of China (English)
吴永烽; 喻洪麟; 何安国
2011-01-01
Aiming at the status that the signal demodulation effect of ring ball grating torque sensor is not obvious with common methods, a demodulation method based on wavelet neural networks (WNN) is put forward. According to the localization property of time and frequency domains and the translation invariant property of undecimated wavelet transform, the preprocessed signal of the sensor is decomposed with multiple resolutions, and the signal is reconstructed with wavelet under the intervention of neural network. A WNN model is constructed and the algorithm program is realized on laboratory virtual instrument engineering workbench ( Lab VIEW) platform. With the test platform, demodulation experiments are carried out on corresponding sensor signals when the shaft continuously rotates along the same direction, rotates along alternate directions and is knocked. Experiment results indicate that the demodulation effect and reliability are very well.%针对常用方法对环形球栅扭矩传感器信号的解调效果不明显的状况,提出基于小波神经网络的解调方法.利用非抽样小波变换的时频局部化特性和平移不变性,对预处理后的传感器信号进行多分辨率分解,并在神经网络的干预下进行小波重构.构建了小波神经网络模型,并在LabVIEW中编程实现了该算法.在测试平台中分别对同向转动机械轴、来回换向转动机械轴以及对机械轴敲击时所对应的传感器信号进行解调实验,其结果表明解调的效果好,可靠性高.
Energy Technology Data Exchange (ETDEWEB)
Chu, T.L.; Musicki, Z.; Kohut, P. [Brookhaven National Lab., Upton, NY (United States)] [and others
1994-06-01
During 1989, the Nuclear Regulatory Commission (NRC) initiated an extensive program to carefully examine the Potential risks during low Power and shutdown operations. The program includes two parallel projects being performed by Brookhaven National Laboratory (BNL) and Sandia National Laboratories (SNL). Two plants, Surry (pressurized water reactor) and Grand Gulf (boiling water reactor), were selected as the Plants to be studied. The objectives of the program are to assess the risks of severe accidents initiated during plant operational states other than full power operation and to compare the estimated core damage frequencies, important accident sequences and other qualitative and quantitative results with those accidents initiated during full power operation as assessed in NUREG-1150. The objective of this report is to document the approach utilized in the Surry plant and discuss the results obtained. A parallel report for the Grand Gulf plant is prepared by SNL. This study shows that the core-damage frequency during mid-loop operation at the Surry plant is comparable to that of power operation. We recognize that there is very large uncertainty in the human error probabilities in this study. This study identified that only a few procedures are available for mitigating accidents that may occur during shutdown. Procedures written specifically for shutdown accidents would be useful. This document, Volume 2, Pt. 2 provides appendices A through D of this report.
Energy Technology Data Exchange (ETDEWEB)
Chu, T.L.; Musicki, Z.; Kohut, P. [Brookhaven National Lab., Upton, NY (United States)] [and others
1994-06-01
During 1989, the Nuclear Regulatory Commission (NRC) initiated an extensive program to carefully examine the potential risks during low power and shutdown operations. The program includes two parallel projects being performed by Brookhaven National Laboratory (BNL) and Sandia National Laboratories (SNL). Two plants, Surry (pressurized water reactor) and Grand Gulf (boiling water reactor), were selected as the plants to be studied. The objectives of the program are to assess the risks of severe accidents initiated during plant operational states other than full power operation and to compare the estimated core damage frequencies, important accident sequences and other qualitative and quantitative results with those accidents initiated during full power operation as assessed in NUREG-1150. The objective of this report is to document the approach utilized in the Surry plant and discuss the results obtained. A parallel report for the Grand Gulf plant is prepared by SNL. This study shows that the core-damage frequency during mid-loop operation at the Surry plant is comparable to that of power operation. The authors recognize that there is very large uncertainty in the human error probabilities in this study. This study identified that only a few procedures are available for mitigating accidents that may occur during shutdown. Procedures written specifically for shutdown accidents would be useful.
Two AFC Loops For Low CNR And High Dynamics
Hinedi, Sami M.; Aguirre, Sergio
1992-01-01
Two alternative digital automatic-frequency-control (AFC) loops proposed to acquire (or reacquire) and track frequency of received carrier radio signal. Intended for use where carrier-to-noise ratios (CNR's) low and carrier frequency characterized by high Doppler shift and Doppler rate because of high relative speed and acceleration, respectively, between transmitter and receiver. Either AFC loops used in place of phase-locked loop. New loop concepts integrate ideas from classical spectrum-estimation, digital-phase-locked-loop, and Kalman-Filter theories.
Institute of Scientific and Technical Information of China (English)
王本庆; 曾昭林
2015-01-01
针对多进制Chirp-rate调制的通信系统解调算法由于基函数的正交性差导致实现复杂且性能不佳的特点，提出采用基于双正交Fourier变换的解调算法多进制的Chirp-rate调制行正交解调，解决了不同调频率的Chirp信号相互正交的问题，解调后可以得到信号调频率密度谱。BFT算法特点是信号在双正交基下展开，对多LFM信号分析不需要搜索，没有交叉项，特别适合对不同调频斜率组成的多LFM信号进行调频斜率分析。仿真表明其基于双正交Fourier变换的多进制Chirp-rate键控调制的解调算法具有接近MFSK误码率的性能。%According to the communication system and demodulation algorithm for M-ary Chirp-rate modulation due to the orthogonality of basis functions due to poor implementation complexity and poor performance, put forward using Chirp-rate modulation demodulation algorithm for orthogonal demodulating M-ary double orthogonal Fourier transform based on Chirp, to solve the signals of different frequency rate are orthogonal, the demodulated signal was FM density spectrum. The characteristics of the BFT algorithm is carried out in two orthogonal signal, the analysis on the multi LFM signal does not need to search, no cross terms, especially suitable for the analysis of multi LFM signal modulation slope composed of different frequency rate. Simulation results show that the demodulation algorithm for M-ary biorthogonal transform Chirp-rate key Fourier modulation based on BER performance close to MFSK.
Joint Demodulation of Low-Entropy Narrowband Cochannel Signals
2006-12-01
Decoding Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 xvi LIST OF ACRONYMS AIS Automatic Identification System AWGN additive...impulse response FPGA Field Programmable Gate Array FSK frequency shift keying GMSK Gaussian minimum shift keying GPP general purpose processor xvii GSM ...Global System for Mobile Communications ( GSM ) cell phone systems. Murota examines spectrum manipulation of minimum-shift keying (MSK) by introducing
Digital carrier demodulator employing components working beyond normal limits
Hurd, William J. (Inventor); Sadr, Ramin (Inventor)
1990-01-01
In a digital device, having an input comprised of a digital sample stream at a frequency F, a method is disclosed for employing a component designed to work at a frequency less than F. The method, in general, is comprised of the following steps: dividing the digital sample stream into odd and even digital samples streams each at a frequency of F/2; passing one of the digital sample streams through the component designed to work at a frequency less than F where the component responds only to the odd or even digital samples in one of the digital sample streams; delaying the other digital sample streams for the time it takes the digital sample stream to pass through the component; and adding the one digital sample stream after passing through the component with the other delayed digital sample streams. In the specific example, the component is a finite impulse response filter of the order ((N + 1)/2) and the delaying step comprised passing the other digital sample streams through a shift register for a time (in sampling periods) of ((N + 1)/2) + r, where r is a pipline delay through the finite impulse response filter.
Paul, Clayton R
2010-01-01
"Inductance is an unprecedented text, thoroughly discussing "loop" inductance as well as the increasingly important "partial" inductance. These concepts and their proper calculation are crucial in designing modern high-speed digital systems. World-renowned leader in electromagnetics Clayton Paul provides the knowledge and tools necessary to understand and calculate inductance." "With the present and increasing emphasis on high-speed digital systems and high-frequency analog systems, it is imperative that system designers develop an intimate understanding of the concepts and methods in this book. Inductance is a much-needed textbook designed for senior and graduate-level engineering students, as well as a hands-on guide for working engineers and professionals engaged in the design of high-speed digital and high-frequency analog systems."--Jacket.
An Analysis of Modified Demodulation-Based Grid Voltage Parameter Estimator
DEFF Research Database (Denmark)
Golestan, Saeed; Guerrero, Josep M.
2015-01-01
Generally speaking, designing single-phase phaselocked loops (PLLs) is more complicated than three-phase ones, as their implementation often involves the generation of a fictitious orthogonal signal for the frame transformation. In recent years, many approaches to generate the orthogonal signal...... have been proposed, the simplest perhaps being the transfer delay based method. In the transfer delay based PLL (TD-PLL), the orthogonal signal is generated by delaying the original singlephase signal by T=4 (one-quarter of a period). The phase shift caused by the transfer delay block, however......, will not be exactly 90 under off-nominal grid frequencies, which results in errors in the estimated quantities by the TD-PLL. To alleviate this issue, an improved version of TD-PLL, called the non-frequency dependent TD-PLL (NTD-PLL), has recently been proposed. The NTD-PLL uses another T=4 delay unit in its feedback...
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
A Single Chip VLSI Implementation of a QPSK/SQPSK Demodulator for a VSAT Receiver Station
Kwatra, S. C.; King, Brent
1995-01-01
This thesis presents a VLSI implementation of a QPSK/SQPSK demodulator. It is designed to be employed in a VSAT earth station that utilizes the FDMA/TDM link. A single chip architecture is used to enable this chip to be easily employed in the VSAT system. This demodulator contains lowpass filters, integrate and dump units, unique word detectors, a timing recovery unit, a phase recovery unit and a down conversion unit. The design stages start with a functional representation of the system by using the C programming language. Then it progresses into a register based representation using the VHDL language. The layout components are designed based on these VHDL models and simulated. Component generators are developed for the adder, multiplier, read-only memory and serial access memory in order to shorten the design time. These sub-components are then block routed to form the main components of the system. The main components are block routed to form the final demodulator.
Lin, Cheng; Zhu, Yong; Wei, Wei; Zhang, Jie; Tian, Li; Xu, Zu-Wen
2013-05-01
An all-optical quartz-enhanced photoacoustic spectroscopy system, based on the F-P demodulation, for trace gas detection in the open environment was proposed. In quartz-enhanced photoacoustic spectroscopy (QEPAS), an optical fiber Fabry-Perot method was used to replace the conventional electronic demodulation method. The photoacoustic signal was obtained by demodulating the variation of the Fabry-Perot cavity between the quartz tuning fork side and the fiber face. An experimental system was setup. The experiment for detection of water vapour in the open environment was carried on. A normalized noise equivalent absorption coefficient of 2.80 x 10(-7) cm(-1) x W x Hz(-1/2) was achieved. The result demonstrated that the sensitivity of the all-optical quartz-enhanced photoacoustic spectroscopy system is about 2.6 times higher than that of the conventional QEPAS system. The all-optical quartz-enhanced photoacoustic spectroscopy system is immune to electromagnetic interference, safe in flammable and explosive gas detection, suitable for high temperature and high humidity environments and realizable for long distance, multi-point and network sensing.
The DPSK Signal Noncoherent Demodulation Receiver Based on the Duffing Oscillators Array
Fu, Yongqing; Li, Yanan; Zhang, Lin; Li, Xingyuan
2016-12-01
Chaotic communication requires the knowledge of corresponding phase relationship between the primary phase of Duffing oscillator’s internal driving force and the primary phase of the undetected signal. Currently, there is no method of noncoherent demodulation for DPSK (Differential Phase Shift Keying) signal and mobile communication signal by Duffing oscillator. To solve this problem, this study presents a noncoherent demodulation method based on the Duffing oscillators array and Duffing oscillator optimization. We first present the model of Duffing oscillator and its sensitivity to undetected signal primary phase. Then the zone partition is proposed to identify the Duffing oscillator’s phase trajectory, and subsequently, the mathematical model and implementation method of the Duffing oscillators array are outlined. Thirdly, the Duffing oscillator optimization and its adaptive strobe technique are proposed, also their application to DPSK signal noncoherent demodulation are discussed. Finally, the design of new concept DPSK chaotic digital receiver based on the Duffing oscillators array is presented, together with its simulation results obtained by using SystemView simulation platform. The simulation results suggest that the new concept receiver based on the Duffing oscillator optimization of Duffing oscillators array owns better SNR (signal-to-noise ratio) threshold property than typical existing receivers (chaotic or nonchaotic) in the AWGN (additive white Gaussian noise) channel and multipath Rayleigh fading channel. In addition, the new concept receiver may detect mobile communication signal.
Directory of Open Access Journals (Sweden)
M. V. Mekhrengin
2015-03-01
Full Text Available Modified phase-generated carrier homodyne demodulation technique for fiber-optic sensors is presented. Nowadays phase-generated carrier homodyne demodulation technique is one of the most widespread. One of its drawbacks is the temperature dependence of the output signal because of the modulator scale factor temperature dependence. In order to compensate this dependence an automatic adjustment of the phase modulation depth is necessary. To achieve the result, additional harmonics analysis is used with the help of the Bessel functions. For this purpose the known demodulation scheme is added with the branch, where interferometric signal is multiplied by the third harmonic of the modulation signal. The deviation of optimal ratio of odd harmonics is used as a feedback signal for adjusting the modulation depth. Unwanted emissions arise in the feedback signal, when the third harmonic possesses a value close to zero. To eliminate unwanted emission in the feedback signal, the principle scheme is added with one more branch, where interferometric signal is multiplied by the forth harmonic of the modulation signal. The deviation of optimal ratio of even harmonics is used as a feedback signal alternately with the deviation of optimal ratio of odd harmonics. A mathematical model of the algorithm is designed using the MATLAB package. Results of modeling have confirmed that suggested method gives the possibility for an automatic adjustment of the phase modulation depth and makes it possible to compensate temperature dependence for the modulator scale factor and output signal magnitude.
On-chip WDM mode-division multiplexing interconnection with optional demodulation function.
Ye, Mengyuan; Yu, Yu; Chen, Guanyu; Luo, Yuchan; Zhang, Xinliang
2015-12-14
We propose and fabricate a wavelength-division-multiplexing (WDM) compatible and multi-functional mode-division-multiplexing (MDM) integrated circuit, which can perform the mode conversion and multiplexing for the incoming multipath WDM signals, avoiding the wavelength conflict. An phase-to-intensity demodulation function can be optionally applied within the circuit while performing the mode multiplexing. For demonstration, 4 × 10 Gb/s non-return-to-zero differential phase shift keying (NRZ-DPSK) signals are successfully processed, with open and clear eye diagrams. Measured bit error ratio (BER) results show less than 1 dB receive sensitivity variation for three modes and four wavelengths with demodulation. In the case without demodulation, the average power penalties at 4 wavelengths are -1.5, -3 and -3.5 dB for TE₀-TE₀, TE₀-TE₁ and TE₀-TE₂ mode conversions, respectively. The proposed flexible scheme can be used at the interface of long-haul and on-chip communication systems.
Yan, Bing-Nan; Liu, Chong-Xin; Ni, Jun-Kang; Zhao, Liang
2016-10-01
In order to grasp the downhole situation immediately, logging while drilling (LWD) technology is adopted. One of the LWD technologies, called acoustic telemetry, can be successfully applied to modern drilling. It is critical for acoustic telemetry technology that the signal is successfully transmitted to the ground. In this paper, binary phase shift keying (BPSK) is used to modulate carrier waves for the transmission and a new BPSK demodulation scheme based on Duffing chaos is investigated. Firstly, a high-order system is given in order to enhance the signal detection capability and it is realized through building a virtual circuit using an electronic workbench (EWB). Secondly, a new BPSK demodulation scheme is proposed based on the intermittent chaos phenomena of the new Duffing system. Finally, a system variable crossing zero-point equidistance method is proposed to obtain the phase difference between the system and the BPSK signal. Then it is determined that the digital signal transmitted from the bottom of the well is ‘0’ or ‘1’. The simulation results show that the demodulation method is feasible. Project supported by the National Natural Science Foundation of China (Grant No. 51177117) and the National Key Science & Technology Special Projects, China (Grant No. 2011ZX05021-005).
Investigation of Continuously Variable Slope Delta Modulator/Demodulator Compatability.
1980-12-01
20 d,"mO Test Signal) 4 stp Ize Pratio -J-l Li] c4 u FnoR~e mx -,cli - td 32k/ I’.’: (2 .Bm’ et i~ l z s tep g ize Ratio MJismatc(_h Bd FREQUENCY ( HZJ ...1-b/s SZample Rate (-20 dBr,.O Test Signal) 77 Time Gonstant ’.’isrnatch * f7 - Mtche d Q .0025 0 .0 0. 9> 14J liot FREQUENCY ( HZJ Fipure 50 a . CVSD...APPENDIX rl Total t’,ar-onic i tor’i w’. -r -,,,t ,ntl Po’..’r PROGRAM DTHD(I PUT,OUTPUT,TAPES-INPUT.TAPE6-OUTPUT,PLOT) CT_---- -- - TD US. INPUT POER
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.
Goodaire, EG; Polcino Milies, C
1996-01-01
For the past ten years, alternative loop rings have intrigued mathematicians from a wide cross-section of modern algebra. As a consequence, the theory of alternative loop rings has grown tremendously. One of the main developments is the complete characterization of loops which have an alternative but not associative, loop ring. Furthermore, there is a very close relationship between the algebraic structures of loop rings and of group rings over 2-groups. Another major topic of research is the study of the unit loop of the integral loop ring. Here the interaction between loop rings and group ri
Redinbo, Robert
1994-01-01
Fault tolerance features in the first three major subsystems appearing in the next generation of communications satellites are described. These satellites will contain extensive but efficient high-speed processing and switching capabilities to support the low signal strengths associated with very small aperture terminals. The terminals' numerous data channels are combined through frequency division multiplexing (FDM) on the up-links and are protected individually by forward error-correcting (FEC) binary convolutional codes. The front-end processing resources, demultiplexer, demodulators, and FEC decoders extract all data channels which are then switched individually, multiplexed, and remodulated before retransmission to earth terminals through narrow beam spot antennas. Algorithm based fault tolerance (ABFT) techniques, which relate real number parity values with data flows and operations, are used to protect the data processing operations. The additional checking features utilize resources that can be substituted for normal processing elements when resource reconfiguration is required to replace a failed unit.
SFFT based phase demodulation for faster interference fringes analysis
Lee, Chen-Yu; Hsu, Kuan-Yu; Lee, Chih-Kung
2016-03-01
Try to take advantages of the high-resolution CCD/CMOS developed over the years for real-time three-dimensional deformation/geometry metrology system development, Fourier transform (FT) based algorithms have been integrated to convert interference fringes to wrapped phase maps and then to unwrapped phase maps. All of which led to easy implementation of the algorithms developed over the years to achieve extremely efficient FT computation. Sparse Fast Fourier Transform (SFFT) that only calculating the non-zero coefficient in frequency domain, includes calculations of imaginary part and log, was implemented to further accelerate the computation rate for the above-mentioned FT based operations. Coupling the SFFT accelerated phase map computation approach with Michelson interferometer and Electronic Speckle Pattern Interferometry (ESPI) for near real-time three-dimensional deformation measurement led to the newly developed system. The directions of object deformation are revealed by performing FT to the interference fringes obtained with pre-introduced spatial carrier frequency, which provides a way to retrieve the phase maps by using a single rather than several intensity maps. With only one image frame needed, the interference fringes caused by the deformation could be recorded for off-line phase maps computation if the computation efforts are longer than the recording frame rate. To apply the SFFT algorithm on phase retrieval, a conceptual framework was presented. The benefit of using SFFT as compared to FT was also demonstrated.
An estimator-predictor approach to PLL loop filter design
Statman, Joseph I.; Hurd, William J.
1990-01-01
The design of digital phase locked loops (DPLL) using estimation theory concepts in the selection of a loop filter is presented. The key concept, that the DPLL closed-loop transfer function is decomposed into an estimator and a predictor, is discussed. The estimator provides recursive estimates of phase, frequency, and higher-order derivatives, and the predictor compensates for the transport lag inherent in the loop.
Institute of Scientific and Technical Information of China (English)
李明艳; 张宇; 苏光; 鞠蕊; 邓春霞; 张凡; 杨文静; 杨雪梅; 王敬; 王春敏
2012-01-01
目的 探讨高频电波刀术(LEEP术)对宫颈上皮内瘤(CIN)Ⅰ合并宫颈人乳头状瘤病毒(HPV)感染的治疗效果.方法 选择符合入组标准CIN Ⅰ伴HPV感染患者60例,分成两组.治疗组(30例)采用LEEP术；观察组(30例)不做治疗.3个月后复查TCT、HPV和阴道镜点活检,首次复查后每6个月复查TCT、HPV和阴道镜点活检,随访2年.观察两组C1N Ⅰ转归情况及HPV清除率.结果 LEEP术治疗组ClN Ⅰ显效率/HPV转阴率第3、6、12、24个月分别为60.0％/46.7％、70.0％/56.67％ 、76.7％/73.3％ 、86.7％/83.3％;观察组为30.0％/16.7％、36.7％/30.0％、46.7％/ 36.7％、63.3％/50.0％,治疗组优于观察组,差异有统计学意义(P＜0.01).结论 LEEP术能有效破坏宫颈表面病灶,抑制CINI进展复发,是诊断和治疗CIN安全有效的方法,能提高HPV清除率.%Objective To evaluate the role of high frequency loop electrosurgical excision procedure in the treatment of cervical intraepithelial neoplasia (CINI). Methods An analysis was conducted in 367 patients with ASC or cervical intraepithelial neoplasia preliminarily diagnosed by Liquid-based thin-layer cytology technique selected from 19397 patients between June, 2008 and February, 2010 at Chuiyangliu Hospital.Sixty patients with cervical intraepithelial neoplasia were caused by by human papilloma virus infection. They were divided into two groups, one with 30 patients treated by loop electrosurgical excision procedure and another with 30 patients without treatment. Two groups underwent liquid-based cytology test, colposcopie assessment and the cervical cells for HPV genotype testing by the polymerase chain reaction (PCR) respectively at 3rd, 6th, 12th, 18th, 24th months after treatment. Prognosis and clearing rate of HPV of the two groups were evaluated. Results The effective rate of treatment of CIN I and the HPV clearing rate was 60.0%/46.7%、70.0%/56.7%、76.7%/73.3%,86.7%/83.3% and 30.0%/16.7%,36.7%/30
Single frame profilometry with rapid phase demodulation on colour-coded fringes
Yee, Cong Kai; Yen, Kin Sam
2017-08-01
Digital fringe profilometry is a non-contact surface profiling technique with huge potential at real-time dynamic whole-field measurement. However, this technique is usually bottlenecked at the phase demodulation and unwrapping during fringe analysis. This paper proposes a single frame profilometry system that used direct arccosine function demodulation on colour-coded sinusoidal fringes to simplify the fringe analysis process. Since the range of arccosine function output is restricted from 0 to π, the intensity gradient was used along with arccosine function to demodulate the fringe intensity levels into wrapped phase map (0-2π). The projected fringes were coloured in red, green and blue according to the De Bruijn's sequence. The fringe order was identified directly from the colours of three consecutive fringes by matching to the De Bruijn's sequence to unwrap the wrapped phase map into continuous phase map. The phase differences between the continuous phase maps of reference plane and object surface were then obtained and related to the equipment setup position using trigonometry to rebuild the 3D model. The proposed method was tested experimentally by reconstructing three physical objects. Although the reconstructed surface contained phase errors due to gamma non-linearity, the geometrical shapes of the objects can be reconstructed with reasonable accuracy and consistency. The percentage deviations of dimensions in x, y and z-axis were 1.24%, -1.96% and -2.30% respectively. Meanwhile the uncertainties of dimensions in x, y and z-axis were ±0.15%, ±0.24% and ±1.07% respectively at 95% confidence level.
The Statistical Loop Analyzer (SLA)
Lindsey, W. C.
1985-01-01
The statistical loop analyzer (SLA) is designed to automatically measure the acquisition, tracking and frequency stability performance characteristics of symbol synchronizers, code synchronizers, carrier tracking loops, and coherent transponders. Automated phase lock and system level tests can also be made using the SLA. Standard baseband, carrier and spread spectrum modulation techniques can be accomodated. Through the SLA's phase error jitter and cycle slip measurements the acquisition and tracking thresholds of the unit under test are determined; any false phase and frequency lock events are statistically analyzed and reported in the SLA output in probabilistic terms. Automated signal drop out tests can be performed in order to trouble shoot algorithms and evaluate the reacquisition statistics of the unit under test. Cycle slip rates and cycle slip probabilities can be measured using the SLA. These measurements, combined with bit error probability measurements, are all that are needed to fully characterize the acquisition and tracking performance of a digital communication system.
Asymmetric acoustic propagation of wave packets via the self-demodulation effect
Devaux, Thibaut; Richoux, Olivier; Pagneux, Vincent
2015-01-01
This article presents the experimental characterization of nonreciprocal elastic wave transmission in a single-mode elastic waveguide. This asymmetric system is obtained by coupling a selection layer with a conversion layer: the selection component is provided by a phononic crystal, while the conversion is achieved by a nonlinear self-demodulation effect in a 3D unconsolidated granular medium. A quantitative experimental study of this acoustic rectifier indicates a high rectifying ratio, up to $10^6$, with wide band (10 kHz) and an audible effect. Moreover, this system allows for wave-packet rectification and extends the future applications of asymmetric systems.
Demodulating Subsampled Direct Sequence Spread Spectrum Signals using Compressive Signal Processing
DEFF Research Database (Denmark)
Fyhn, Karsten; Arildsen, Thomas; Larsen, Torben
2012-01-01
We show that to lower the sampling rate in a spread spectrum communication system using Direct Sequence Spread Spectrum (DSSS), compressive signal processing can be applied to demodulate the received signal. This may lead to a decrease in the power consumption or the manufacturing price of wireless...... theoretical work is exemplified with a numerical experiment using the IEEE 802.15.4 standard’s 2.4GHz band specification. The numerical results support our theoretical indings and indicate that compressive sensing may be used successfully in spread spectrum communication systems. The results obtained here may...
An all-digital demodulation scheme for DVB-S2
Wang, Qiong; Zhan, Yafeng; Lu, Jianhua
2005-11-01
In this paper, an all-digital demodulation scheme which is compliant with the second generation digital video broadcasting via satellites (DVB-S2) is presented. It works well for several modulation modes supported by DVB-S2 even under rather low signal-to-noise ratio (SNR). All algorithms adopted in this scheme have been described in detail and their computer simulation results have been shown. The symbol error rate (SER) performance from simulations is very close to the theoretical one.
Institute of Scientific and Technical Information of China (English)
Tingting Liu; Jie Cui; Desheng Chen; Ling Xiao; Dexing Sun
2008-01-01
2Optical fiber interferometric sensors based on [3 × 3] couplers have been used in many fields. A new technique is proposed to demodulate output signals of this kind of sensors. The technique recovers the signal of interest by fitting coefficients of elliptic (Lissajous) curves between each fiber pair. Different from other approaches, this technique eliminates the dependence on the idealization of [3 × 3] coupler, provides enhanced tolerance to the variance of photoelectric converters, and is anti-polarization in a certain extent. The main algorithm has been successfully demonstrated both by numerical simulation and experimental result.
Omura, J. K.; Simon, M. K.
1982-01-01
A theory for deducing and predicting the performance of transmitter/receivers for bandwidth efficient modulations suitable for use on the nonlinear satellite channel is presented. The underlying principle used throughout is the development of receiver structures based on the maximum likelihood decision rule and aproximations to it. The bit error probability transfer function bounds developed in great detail in Part 4 is applied to these modulation/demodulation techniques. The effects of the various degrees of receiver mismatch are considered both theoretically and by numerous illustrative examples.
A Synthetic Quadrature Phase Detector/Demodulator for Fourier Transform Transform Spectrometers
Campbell, Joel
2008-01-01
A method is developed to demodulate (velocity correct) Fourier transform spectrometer (FTS) data that is taken with an analog to digital converter that digitizes equally spaced in time. This method makes it possible to use simple low cost, high resolution audio digitizers to record high quality data without the need for an event timer or quadrature laser hardware, and makes it possible to use a metrology laser of any wavelength. The reduced parts count and simplicity implementation makes it an attractive alternative in space based applications when compared to previous methods such as the Brault algorithm.
Development of a suspended-mass RSE interferometer using third harmonic demodulation
Miyakawa, O; Heinzel, G; Kawamura, S
2002-01-01
The most important point of a resonant sideband extraction (RSE) experiment is the signal extraction for control of the interferometer. We proposed a new signal-sensing method for the single modulation scheme. This method uses the third harmonic demodulation (THD) with a particular asymmetry in the interferometer which makes the third-order sidebands vanish at the detecting port. We have successfully locked a suspended-mass RSE interferometer for the first time by the THD method. The transfer function of the interferometer was measured to confirm the RSE effect.
A method for closed loop automatic tuning of PID controllers
Directory of Open Access Journals (Sweden)
Tor S. Schei
1992-07-01
Full Text Available A simple method for the automatic tuning of PID controllers in closed loop is proposed. A limit cycle is generated through a nonlinear feedback path from the process output to the controller reference signal. The frequency of this oscillation is above the crossover frequency and below the critical frequency of the loop transfer function. The amplitude and frequency of the oscillation are estimated and the control parameters are adjusted iteratively such that the closed loop transfer function from the controller reference to the process output attains a specified amplitude at the oscillation frequency.
Baumeister, Barbara
2009-01-01
We continue the work by Aschbacher, Kinyon and Phillips [AKP] as well as of Glauberman [Glaub1,2] by describing the structure of the finite Bruck loops. We show essentially that a finite Bruck loop $X$ is the direct product of a Bruck loop of odd order with either a soluble Bruck loop of 2-power order or a product of loops related to the groups $PSL_2(q)$, $q= 9$ or $q \\geq 5$ a Fermat prime. The latter possibillity does occur as is shown in [Nag1, BS]. As corollaries we obtain versions of Sylow's, Lagrange's and Hall's Theorems for loops.
Servin, Manuel
2012-01-01
This paper presents a digital interferometric method to demodulate Placido fringe patterns. This method uses a computer-stored conic-wavefront as reference carrier. Even though, Placido mires are widely used in corneal topographers. This is not however a paper on corneal topography and/or its clinical use. This paper focuses on the theoretical aspects to phase-demodulate Placido mires using synchronous interferometric techniques. Placido patterns may also be applied to test optical wavefronts using a Placido-Hartmann opaque plate with periodic annular apertures. This test is sensitive to the radial slope of the measuring wavefront. Another wavefront testing approach may use a Placido-Hartmann-Shack screen with a periodic array of toroidal lenslets. This periodic screen is sensitive to the wavefront's radial-slope at the focal plane of the lenslets. In brief, digital interferometric methods are herein applied for the first time to demodulate conic-carrier Placido images. Finally it should be mentioned that thi...
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.
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.
Institute of Scientific and Technical Information of China (English)
王光鼎; 游福初; 房建成
2012-01-01
介绍了接收卫星信号的数字中频接收机载波同步跟踪关键技术，针对高机动环境下载波同步需要解决的捕获带宽、捕获速度与跟踪精度的矛盾，综合利用了传统数字锁频环路（DFLL）和数字锁相环路（DPLL）的优点，设计了一种适合高机动环境下数字中频接收机的锁频联合锁相环工作的环路方案。并利用计算机仿真分析结果，证明了该方案的可行性和优越性，为ADC＋FPGA＋DSP框架下卫星信号数字中频接收机软硬件实现提供了设计依据。%The carrier synchronization track technique of digital intermediate frequency receiving machine is introduced, which is important for receiving the signal of satellites. In the seriously dynamic situation, the inconsistency among the bandwidth, velocity and precision of capture for carrier synchronization should be resolved. Integrating the traditional FDLL and DPLL, a new loop project is designed, which frequency lock associated with phase lock, and it＇ s suitable for digital intermediate frequency receiving machine in seriously dynamic situation. The analysis and simulation by computer is carried out, and the feasibility and advantage are proved. Then the hardware framework with ADC ＋ FPGA ＋ DSP for digital intermediate frequency receiving machine of satellite signal is well-founded.
参量声源自解调信号失真研究%Research on self-demodulated signal distortion of parametric sound source
Institute of Scientific and Technical Information of China (English)
杨天文; 黄大贵; 陈敏; 张富东; 陈祥
2013-01-01
The distortion problem of the self-demodulated signal of parametric sound source is analyzed theoretically according to the “Berktay far-field solution”,and the theoretical analysis result is verified with some related experiments.The results show that the “Berktay far-field solution” can predict the fundamental frequency and difference frequency at an acceptable precision;but for the main factors that cause signal distortion,such as second-order harmonic wave and sum-frequency wave,the prediction errors are too large to be accepted,which means that the “Berktay far-field solution” can not be used as the theoretical basis for analyzing the distortion.The difference frequency signal is not the main factor causing the distortion of the self-demodulated signal of parametric sound source; and the effective approach to reduce the distortion is to reduce the second-order harmonic and sum-frequency components,which can suppress the quantity and amplitude of the harmful frequency components effectively.This study reveals the main factors contributing to the self-demodulated signal distortion and their varying rule,which can provide a helpful reference for investigating the signal processing methods of parametric sound source.%针对参量声源自解调信号失真问题,根据“Berktay远场解”对其进行了理论分析,并通过实验对理论分析结果进行了验证,发现:“Berktay远场解”对自解调信号中的基频、差频可以较准确地预测,而对导致信号失真的主要因素如二次谐波、和频等的预测误差很大,不能作为失真分析的精确依据;差频不是导致参量声源自解调信号失真的主要原因,降低失真的有效途径是减小自解调信号中二次谐波、和频分量,从而使有害频率成分的数量及幅值得到有效抑制.本项研究揭示了导致参量声源自解调信号失真的主要因素及其变化规律,可为参量声源信号处理方法的研究提供有益参考.
Institute of Scientific and Technical Information of China (English)
Zhuo-Xi Huo; Jian-Feng Zhou
2013-01-01
The hard X-ray modulation telescope (HXMT) mission is mainly devoted to performing an all-sky survey at 1-250 keV with both high sensitivity and high spatial resolution.The observed data reduction as well as the image reconstruction for HXMT can be achieved by using the direct demodulation method (DDM).However the original DDM is too computationally expensive for multi-dimensional data with high resolution to be employed for HXMT data.We propose an accelerated direct demodulation method especially adapted for data from HXMT.Simulations are also presented to demonstrate this method.
Damped transverse oscillations of interacting coronal loops
Soler, Roberto
2015-01-01
Damped transverse oscillations of magnetic loops are routinely observed in the solar corona. This phenomenon is interpreted as standing kink magnetohydrodynamic waves, which are damped by resonant absorption owing to plasma inhomogeneity across the magnetic field. The periods and damping times of these oscillations can be used to probe the physical conditions of the coronal medium. Some observations suggest that interaction between neighboring oscillating loops in an active region may be important and can modify the properties of the oscillations compared to those of an isolated loop. Here we theoretically investigate resonantly damped transverse oscillations of interacting non-uniform coronal loops. We provide a semi-analytic method, based on the T-matrix theory of scattering, to compute the frequencies and damping rates of collective oscillations of an arbitrary configuration of parallel cylindrical loops. The effect of resonant damping is included in the T-matrix scheme in the thin boundary approximation. ...
An amplitude modulation/demodulation scheme for whisker-based texture perception.
Boubenec, Yves; Claverie, Laure Nayelie; Shulz, Daniel E; Debrégeas, Georges
2014-08-13
Whisking rodents can discriminate finely textured objects using their vibrissae. The biomechanical and neural processes underlying such sensory tasks remain elusive. Here we combine the use of model micropatterned substrates and high-resolution videography of rats' whiskers during tactile exploration to study how texture information is mechanically encoded in the whisker motion. A biomechanical modeling of the whisker is developed, which yields quantitative predictions of the spectral and temporal characteristics of the observed whisker kinetics, for any given topography. These texture-induced whisker vibrations are then replayed via a multiwhisker stimulator while recording neuronal responses in the barrel field of the primary somatosensory cortex (S1bf). These results provide a comprehensive description of the transduction process at play during fine texture sensing in rats. They suggest that the sensory system operates through a vibratory amplitude modulation/demodulation scheme. Fine textural properties are encoded in the time-varying envelope of the whisker-resonant vibrations. This quantity is then recovered by neural demodulation, as it effectively drives the spiking-rate signal of a large fraction of S1 cortical neurons. This encoding/decoding scheme is shown to be robust against variations in exploratory conditions, such as the scanning speed or pad-to-substrate distance, thus allowing for reliable tactile discrimination in realistic conditions. Copyright © 2014 the authors 0270-6474/14/3410832-12$15.00/0.
Realization of 16-channel digital PGC demodulator for fiber laser sensor array
Energy Technology Data Exchange (ETDEWEB)
Wang Lin; He Jun; Li Fang; Liu Yuliang, E-mail: wlcas@semi.ac.cn [Optoelectronics System Laboratory, Institute of Semiconductors, Chinese Academy of Sciences, PO Box 912, Beijing 100083 (China)
2011-02-01
This paper describes a 16-element DFB FL (distributed feedback fiber laser) sensor array system interrogated by NI-PXI-based (PCI extensions for Instrumentation) digital PGC (phase generated carrier) technique. The lasing wavelengths of the DFB FLs are changed by the external strains or temperatures, and hence they can be used as sensors by detecting the wavelength shifts. An unbalanced MI (Michelson interferometer) is employed in the sensor array system to amplify the wavelength shifts of DFB FL sensors to detectable phase shifts. The output phase signals of the MI are separated into different channels by a DWDM, and then detected by a low-noise photodiode array. The digital PGC algorithm is realized on a PXI platform (NI, National Instruments), which consists of three FPGA (Field Programmable Gate Array) modules and a high performance system controller. The normalization of the interference fringe is proposed and realized in this paper to reduce the influence of the light intensity fluctuations, and a trigger mechanism is introduced into the digital multi-channel PGC demodulation scheme to synchronize the date among different channels. A 16-element DFB fiber laser sensor array system has been set up in the experiment and the demodulated results have demonstrated a minimum detectable wavelength shift of 1x10{sup -6} pmA/{radical}Hz, a linearity of as high as 0.9994, and a dynamic range of 110dB-100Hz.
Shoupeng, Song; Zhou, Jiang
2017-03-01
Converting ultrasonic signal to ultrasonic pulse stream is the key step of finite rate of innovation (FRI) sparse sampling. At present, ultrasonic pulse-stream-forming techniques are mainly based on digital algorithms. No hardware circuit that can achieve it has been reported. This paper proposes a new quadrature demodulation (QD) based circuit implementation method for forming an ultrasonic pulse stream. Elaborating on FRI sparse sampling theory, the process of ultrasonic signal is explained, followed by a discussion and analysis of ultrasonic pulse-stream-forming methods. In contrast to ultrasonic signal envelope extracting techniques, a quadrature demodulation method (QDM) is proposed. Simulation experiments were performed to determine its performance at various signal-to-noise ratios (SNRs). The circuit was then designed, with mixing module, oscillator, low pass filter (LPF), and root of square sum module. Finally, application experiments were carried out on pipeline sample ultrasonic flaw testing. The experimental results indicate that the QDM can accurately convert ultrasonic signal to ultrasonic pulse stream, and reverse the original signal information, such as pulse width, amplitude, and time of arrival. This technique lays the foundation for ultrasonic signal FRI sparse sampling directly with hardware circuitry.
Demodulation of a fiber Fabry-Perot strain rosette using white light interferometry
Zuliani, Gary Louis
Fiber optic sensors are starting to be used in specialty application areas where electrical sensors are usually found, such as in aircraft and spacecraft. Fiber optic sensor technology has advantages over its electronic counterparts including small size and weight, immunity to electromagnetic interference, and ruggedness. The use of fiber interferometers as sensors is reviewed along with methods for demodulating their signals. The principles of path-matched differential interferometry and coherence multiplexing are demonstrated and applied to the design and construction of a system that simultaneously demodulates three fiber Fabry-Perot (FFP) interferometers. The FFP's formed the arms of a delta rosette which were bonded to the surface of an aluminum cantilevered beam and were illuminated with one broadband light source. The receiving interferometer consisted of a bulk Michelson interferometer with three distinct optical paths. A charge coupled device array was used as the detector allowing fringe shifts to be counted on a television monitor. Tensor measurements were made and found to be in good agreement when compared to those obtained from electrical strain gages.
Pseudonoise code tracking loop
Laflame, D. T. (Inventor)
1980-01-01
A delay-locked loop is presented for tracking a pseudonoise (PN) reference code in an incoming communication signal. The loop is less sensitive to gain imbalances, which can otherwise introduce timing errors in the PN reference code formed by the loop.
Instantaneous and Frequency-Warped Signal Processing Techniques for Auditory Source Separation.
Wang, Avery Li-Chun
This thesis summarizes several contributions to the areas of signal processing and auditory source separation. The philosophy of Frequency-Warped Signal Processing is introduced as a means for separating the AM and FM contributions to the bandwidth of a complex-valued, frequency-varying sinusoid p (n), transforming it into a signal with slowly-varying parameters. This transformation facilitates the removal of p (n) from an additive mixture while minimizing the amount of damage done to other signal components. The average winding rate of a complex-valued phasor is explored as an estimate of the instantaneous frequency. Theorems are provided showing the robustness of this measure. To implement frequency tracking, a Frequency-Locked Loop algorithm is introduced which uses the complex winding error to update its frequency estimate. The input signal is dynamically demodulated and filtered to extract the envelope. This envelope may then be remodulated to reconstruct the target partial, which may be subtracted from the original signal mixture to yield a new, quickly-adapting form of notch filtering. Enhancements to the basic tracker are made which, under certain conditions, attain the Cramer -Rao bound for the instantaneous frequency estimate. To improve tracking, the novel idea of Harmonic -Locked Loop tracking, using N harmonically constrained trackers, is introduced for tracking signals, such as voices and certain musical instruments. The estimated fundamental frequency is computed from a maximum-likelihood weighting of the N tracking estimates, making it highly robust. The result is that harmonic signals, such as voices, can be isolated from complex mixtures in the presence of other spectrally overlapping signals. Additionally, since phase information is preserved, the resynthesized harmonic signals may be removed from the original mixtures with relatively little damage to the residual signal. Finally, a new methodology is given for designing linear-phase FIR filters
Parallel Digital Phase-Locked Loops
Sadr, Ramin; Shah, Biren N.; Hinedi, Sami M.
1995-01-01
Wide-band microwave receivers of proposed type include digital phase-locked loops in which band-pass filtering and down-conversion of input signals implemented by banks of multirate digital filters operating in parallel. Called "parallel digital phase-locked loops" to distinguish them from other digital phase-locked loops. Systems conceived as cost-effective solution to problem of filtering signals at high sampling rates needed to accommodate wide input frequency bands. Each of M filters process 1/M of spectrum of signal.
The instantaneous frequency rate spectrogram
Czarnecki, Krzysztof
2016-01-01
An accelerogram of the instantaneous phase of signal components referred to as an instantaneous frequency rate spectrogram (IFRS) is presented as a joint time-frequency distribution. The distribution is directly obtained by processing the short-time Fourier transform (STFT) locally. A novel approach to amplitude demodulation based upon the reassignment method is introduced as a useful by-product. Additionally, an estimator of energy density versus the instantaneous frequency rate (IFR) is proposed and referred to as the IFR profile. The energy density is estimated based upon both the classical energy spectrogram and the IFRS smoothened by the median filter. Moreover, the impact of an analyzing window width, additive white Gaussian noise and observation time is tested. Finally, the introduced method is used for the analysis of the acoustic emission of an automotive engine. The recording of the engine of a Lamborghini Gallardo is analyzed as an example.
Institute of Scientific and Technical Information of China (English)
程军圣; 杨怡; 杨宇
2012-01-01
为了提取多分量调幅调频信号的幅值和频率信息,提出了基于局部均值分解(local mean decomposition,简称LMD)的能量算子解调机械故障诊断方法.该方法先利用LMD将机械调制信号分解成若干个乘积函数(production function,简称PF)分量,然后对每一个PF分量进行能量算子解调,获得信号的幅值和频率信息进行故障诊断.利用该方法对仿真信号以及轴承和齿轮故障振动信号进行实验研究的结果表明,基于LMD的能量算子解调方法能够有效地提取机械故障振动信号特征.%An energy operator demodulating approach based on LMD (local mean decomposition) is applied to rotating machinery fault diagnosis. In this approach, LMD method is used to decompose a multi-component AM-FM signal into a number of production functions (PF) firstly; then, the energy operator demodulating is applied to each PF and the amplitudes and frequencies of a multi-component AM-FM signal are extracted for mechanical fault diagnosis. The proposed approach has been applied to simulated signal and bearings and gears fault diagnosis. The analysis results show that the energy operator demodulating approach based on LMD can extract the characteristics of mechanical fault vibration signals efficiently.
GTE Lenkurt, San Carlos, CA.
Twelve articles dealing with telecommunications systems are presented. The articles are for the most part considerations of some of the potential uses and of the technical problems of communication networks used for commercial and educational purposes. Among the topics are the application of communication technology to control pollution, the CATV…
Supersymmetric Wilson loops at two loops
Bassetto, Antonio; Pucci, Fabrizio; Seminara, Domenico
2008-01-01
We study the quantum properties of certain BPS Wilson loops in ${\\cal N}=4$ supersymmetric Yang-Mills theory. They belong to a general family, introduced recently, in which the addition of particular scalar couplings endows generic loops on $S^3$ with a fraction of supersymmetry. When restricted to $S^2$, their quantum average has been further conjectured to be exactly computed by the matrix model governing the zero-instanton sector of YM$_2$ on the sphere. We perform a complete two-loop analysis on a class of cusped Wilson loops lying on a two-dimensional sphere, finding perfect agreement with the conjecture. The perturbative computation reproduces the matrix-model expectation through a highly non-trivial interplay between ladder diagrams and self-energies/vertex contributions, suggesting the existence of a localization procedure.
Kan WU; Shum, Ping
2010-01-01
The phase noise and intensity noise of a pulse train are theoretically analyzed in the demodulation measurement. The effect of pulse asymmetry is discussed for the first time using Fourier series. Experimentally, photodetectors with different bandwidth and incident power levels are compared to achieve minimum pulse distortion.
Chaotic dynamics of frequency combs generated with continuously pumped nonlinear microresonators
Matsko, Andrey B; Savchenkov, Anatoliy A; Maleki, Lute
2012-01-01
We theoretically and experimentally investigate the chaotic regime of optical frequency combs generated in nonlinear ring microresonators pumped with continuous wave light. We show that the chaotic regime reveals itself, in an apparently counter-intuitive way, by a flat top symmetric envelope of the frequency spectrum, when observed by means of an optical spectrum analyzer. The comb demodulated on a fast photodiode produces a noisy radio frequency signal with an spectral width significantly exceeding the linear bandwidth of the microresonator mode.
Self-oscillating loop based piezoelectric power converter
DEFF Research Database (Denmark)
2013-01-01
The present invention relates to a piezoelectric power converter comprising an input driver electrically coupled directly to an input or primary electrode of the piezoelectric transformer without any intervening series or parallel inductor. A feedback loop is operatively coupled between an output...... voltage of the piezoelectric transformer and the input driver to provide a self-oscillation loop around a primary section of the piezoelectric transformer oscillating at an excitation frequency. Electrical characteristics of the feedback loop are configured to set the excitation frequency of the self......- oscillation loop within a zero-voltage-switching (ZVS) operation range of the piezoelectric transformer....
Towards the Realization of Graphene Based Flexible Radio Frequency Receiver
Directory of Open Access Journals (Sweden)
Maruthi N. Yogeesh
2015-11-01
Full Text Available We report on our progress and development of high speed flexible graphene field effect transistors (GFETs with high electron and hole mobilities (~3000 cm2/V·s, and intrinsic transit frequency in the microwave GHz regime. We also describe the design and fabrication of flexible graphene based radio frequency system. This RF communication system consists of graphite patch antenna at 2.4 GHz, graphene based frequency translation block (frequency doubler and AM demodulator and graphene speaker. The communication blocks are utilized to demonstrate graphene based amplitude modulated (AM radio receiver operating at 2.4 GHz.
A Phase Noise Analysis Method for Millimeter-Wave Passive Imager BHU-2D-U Frequency Synthesizer
Jin Zhang; Cheng Zheng; Xianxun Yao; Baohua Yang
2013-01-01
A nontrivial phase noise analysis method is proposed for frequency synthesizer of a passive millimeter-wave synthetic aperture interferometric radiometer (SAIR) imager for concealed weapon detections on human bodies with high imaging rates. The frequency synthesizer provides local oscillator signals for both millimeter-wave front ends and intermediate frequency IQ demodulators for the SAIR system. The influence of synthesizer phase noise in different offset frequency ranges on the visibility ...
Chen, Jian; Dutton, Zachary; Lazarus, Richard; Guha, Saikat
2011-01-01
The quantum states of two laser pulses---coherent states---are never mutually orthogonal, making perfect discrimination impossible. Even so, coherent states can achieve the ultimate quantum limit for capacity of a classical channel, the Holevo capacity. Attaining this requires the receiver to make joint-detection measurements on long codeword blocks, optical implementations of which remain unknown. We report the first experimental demonstration of a joint-detection receiver, demodulating quaternary pulse-position-modulation (PPM) codewords at a word error rate of up to 40% (2.2 dB) below that attained with direct-detection, the largest error-rate improvement over the standard quantum limit reported to date. This is accomplished with a conditional nulling receiver, which uses optimized-amplitude coherent pulse nulling, single photon detection and quantum feedforward. We further show how this translates into coding complexity improvements for practical PPM systems, such as in deep-space communication. We antici...
Diversity of photonic differentiators based on flexible demodulation of phase signals
Ao-ling, Zheng; Lei, Lei; Ting, Yang; Xin-Liang, Zhang
2013-01-01
We theoretically prove a multifunctional photonic differentiation (DIFF) scheme based on phase demodulation using two cascaded linear filters. The photonic DIFF has a diversity of output forms, such as 1st order intensity DIFF, 1st order field DIFF and its inversion, 2nd order field DIFF, dependent on the relative shift between the optical carrier and the filter's resonant notches. As a proof, we also experimentally demonstrate the DIFF diversity using a phase modulator and two delay interferometers (DIs). The calculated average deviation is less than 7% for all DIFF waveforms. Our schemes show the advantages of flexible DIFF functions and forms, which may have different optical applications. For example, high order field differentiators can be used to generate complex temporal waveforms. And intensity differentiators are useful for ultra-wideband pulse generation.
Acquisition times of carrier tracking sampled data phase-locked loops
Aguirre, S.
1986-01-01
Phase acquisition times of type II and III loops typical of the Advanced Receiver are studied by computer simulations when the loops are disturbed by gaussian noise. Reliable estimates are obtained by running 5000 trials for each combination of loop signal-to-noise ratio (SNR) and frequency offset. The probabilities of acquisition are shown versus time from start of acquisition for various loop SNRs and frequency offsets. For frequency offsets smaller than one-fourth of the loop bandwidth and for loop SNRs of 10 dB and higher, the loops acquire with probability 0.99 within 2.5 B sub L for type II loops and within 7/B sub L for type III loops.
Blanco-Pillado, Jose J; Shlaer, Benjamin
2015-01-01
We analyze the shapes of cosmic string loops found in large-scale simulations of an expanding-universe string network. The simulation does not include gravitational back reaction, but we model that process by smoothing the loop using Lorentzian convolution. We find that loops at formation consist of generally straight segments separated by kinks. We do not see cusps or any cusp-like structure at the scale of the entire loop, although we do see very small regions of string that move with large Lorentz boosts. However, smoothing of the string almost always introduces two cusps on each loop. The smoothing process does not lead to any significant fragmentation of loops that were in non-self-intersecting trajectories before smoothing.
Blok, Rieuwert J
2011-01-01
In 1974 Orin Chein discovered a new family of Moufang loops which are now called Chein loops. Such a loop can be created from any group $W$ together with $\\mathbb{Z}_2$ by a variation on a semi-direct product. We study these loops in the case where $W$ is a Coxeter group and show that it has what we call a Chein-Coxeter system, a small set of generators of order 2, together with a set of relations closely related to the Coxeter relations and Chein relations. As a result we are able to give amalgam presentations for Coxeter-Chein loops. This is to our knowledge the first such presentation for a Moufang loop.
Blok, Rieuwert J.; Gagola III, Stephen
2011-01-01
In 1974 Orin Chein discovered a new family of Moufang loops which are now called Chein loops. Such a loop can be created from any group $W$ together with $\\mathbb{Z}_2$ by a variation on a semi-direct product. We study these loops in the case where $W$ is a Coxeter group and show that it has what we call a Chein-Coxeter system, a small set of generators of order 2, together with a set of relations closely related to the Coxeter relations and Chein relations. As a result we are able to give am...
Observational Evidence for Loop-Loop Interaction
Guiping, W.; Guangli, H.; Yuhua, T.; Aoao, X.
2004-01-01
Through analysis of the data including the hard x-ray(BASTE) microwave(NoRP) and magnetogram(MDI from SOHO) as well as the images of soft x-ray(YHKOH) and EIT(SOHO) on Apr. 151998 solar flare in the active region 8203(N30W12) we found: (1) there are similar quasi period oscillation in the profile of hard x-ray flux (25-5050-100keV) and microwave flux(1GHz) with duration of 85+/-25s every peak includes two sub-peak structures; (2) in the preheat phase of the flare active magnetic field changes apparently and a s-pole spot emerges ; (3) several EIT and soft x-ray loops exist and turn into bright . All of these may suggest that loop-loop interaction indeed exist. Through reconnection the electrons may be accelerated and the hard x-ray and microwave emission take place.
Neuron-like dynamics of a phase-locked loop
Matrosov, Valery V.; Mishchenko, Mikhail A.; Shalfeev, Vladimir D.
2013-10-01
Dynamics of two coupled phase-controlled generators based on phase-locked loop systems with a high frequency filter in the control loop was studied. It was found that beating modes are synchronized in the systems and shown that different synchronization states form an overlapping structure in parameters space of the coupled systems. Usage of the phase-locked loop as a neuron-like element is proposed.
Directory of Open Access Journals (Sweden)
Pamela J. Perez
2014-08-01
Full Text Available The looping of DNA provides a means of communication between sequentially distant genomic sites that operate in tandem to express, copy, and repair the information encoded in the DNA base sequence. The short loops implicated in the expression of bacterial genes suggest that molecular factors other than the naturally stiff double helix are involved in bringing the interacting sites into close spatial proximity. New computational techniques that take direct account of the three-dimensional structures and fluctuations of protein and DNA allow us to examine the likely means of enhancing such communication. Here, we describe the application of these approaches to the looping of a 92 base-pair DNA segment between the headpieces of the tetrameric Escherichia coli Lac repressor protein. The distortions of the double helix induced by a second protein—the nonspecific nucleoid protein HU—increase the computed likelihood of looping by several orders of magnitude over that of DNA alone. Large-scale deformations of the repressor, sequence-dependent features in the DNA loop, and deformability of the DNA operators also enhance looping, although to lesser degrees. The correspondence between the predicted looping propensities and the ease of looping derived from gene-expression and single-molecule measurements lends credence to the derived structural picture.
基于软件无线电的RFID解调方法研究%Research of RFID Demodulation Method Based on Softwave Radio
Institute of Scientific and Technical Information of China (English)
张松华
2015-01-01
提出了一种基于软件无线电的RFID解调方法。该方法采用非相干解调技术实现了RFID调制信号的解调。与相干解调技术相比，该方法具有原理简单，在解调过程中无需恢复载波等优点。仿真结果表明，该方法对2ASK和2FSK信号达到很好的解调效果。%This paper proposes a demodulation method of RFID based on softwave radio. The method demo-duates modulated signal of RFID with Noncoherent demodulation. Compared with coherent demodulation, it has advantages of simple principle and avoiding carrier recovery. Simulation proves that it is valid in demodulating 2ASK and 2FSK.
Testing loop quantum cosmology
Wilson-Ewing, Edward
2017-03-01
Loop quantum cosmology predicts that quantum gravity effects resolve the big-bang singularity and replace it by a cosmic bounce. Furthermore, loop quantum cosmology can also modify the form of primordial cosmological perturbations, for example by reducing power at large scales in inflationary models or by suppressing the tensor-to-scalar ratio in the matter bounce scenario; these two effects are potential observational tests for loop quantum cosmology. In this article, I review these predictions and others, and also briefly discuss three open problems in loop quantum cosmology: its relation to loop quantum gravity, the trans-Planckian problem, and a possible transition from a Lorentzian to a Euclidean space-time around the bounce point.
Institute of Scientific and Technical Information of China (English)
马爽; 吴志勇; 高世杰; 耿天文; 吴佳彬
2016-01-01
In order to improve the performance of PPM demodulation system, we proposed an improved digital phase⁃locked loop to extract slot synchronization clock and a fast frame synchronization extraction scheme. On the basis of traditional digital phase⁃locked loop, the digital filter and FIFO buffer unit are added. The results show that the slot synchronization clock can be precisely adjusted. The adjustment accuracy is 0.25π. The jitter of slot synchronization clock is only 1.5 ns in 10 Mbps. Finally the system achieves atmospheric laser communication in 10 Mbps.%为进一步提高PPM解调的性能，系统以FPGA为主控单元，提出了一种改进的数字锁相环提取时隙同步时钟和快速帧同步提取方案，在传统的数字锁相环中添加了数字滤波器和FIFO缓存单元．结果表明：系统能够精确地调整时隙时钟，调整精度达到0．25π，10 Mbps信号的时隙时钟的抖动量仅为1．5 ns，最终系统实现了10 Mbps的大气激光通信．
Xia, Ji; Wang, Qi; Liu, Xu; Luo, Hong
2015-07-09
An optical fiber current sensor based on Fabry-Perot interferometer using a fiber Bragg grating demodulation is proposed. Magnetic fluid is used as a sensitive medium in fiber optical Fabry-Perot (F-P) cavity for the optical characteristic of magnetic-controlled refractive index. A Fiber Bragg grating (FBG) is connected after the F-P interferometer which is used to reflect the optical power at the Bragg wavelength of the interference transmission spectrum. The corresponding reflective power of the FBG will change with different external current intensity, due to the shift on the interference spectrum of the F-P interferometer. The sensing probe has the advantages of convenient measurement for its demodulation, low cost and high current measurement accuracy on account of its sensing structure. Experimental results show that an optimal sensitivity of 0.8522 nw/A and measurement resolution of 0.001 A is obtained with a FBG at 1550 nm with 99% reflectivity.
Mattison, Scott P; Shelton, Ryan L; Maxson, Ryan T; Applegate, Brian E
2013-01-01
A four dimensional data set of the cardiac cycle of a zebrafish embryo was acquired using postacquisition synchronization of real time photoacoustic b-scans. Utilizing an off-axis photoacoustic microscopy (OA-PAM) setup, we have expanded upon our previous work with OA-PAM to develop a system that can sustain 100 kHz line rates while demodulating the bipolar photoacoustic signal in real-time. Real-time processing was accomplished by quadrature demodulation on a Field Programmable Gate Array (FPGA) in line with the signal digitizer. Simulated data acquisition verified the system is capable of real-time processing up to a line rate of 1 MHz. Galvanometer-scanning of the excitation laser inside the focus of the ultrasonic transducer enables real data acquisition of a 200 by 200 by 200 pixel, volumetric data set across a 2 millimeter field of view at a rate of 2.5 Hz.
Current source and digital demodulation technique in EIT system based on FPGA%一种基于FPGA的EIT电流源和数字解调方法
Institute of Scientific and Technical Information of China (English)
郝会玲; 赵德春; 沙洪
2012-01-01
Objective A general experiment platform of electrical impedance tomography(EIT) based on field programmable gate array(FPGA) was designed to meet the requirements of EIT digital measurement.A digital current source and the research on digital demodulation method was completed.Methods For construction of the experiment platform,DDS module,D/A and A/D interface module,digital demodulation module and RS-232 communication module were all integrated in one FPGA chip.Results The source can provide multi-frequency excitation signals of 2 mA in the range of 6.1-390.6 kHz.The output impedance of the source was higher than 190 kΩ.Both the real and the virtual information of measured impedance could be extracted.Conclusion Measurements based on bioimpedance-equivalent circuit model verified the validity of the platform.The research results of this paper provides a foundation for the construction of a practical EIT system.%目的 依据数字化电阻抗断层成像(EIT)硬件系统的要求,构建了基于现场可编程门阵列(FPGA)的通用型EIT硬件实验平台,完成了直接数字频率合成(DDS)的电流源和数字解调方法研究.方法 实验平台以FPGA芯片为核心,集成了DDS模块、D/A及A/D接口模块、数字解调模块和RS-232数据通信等模块.结果 电流源可在6.1～390.6 kHz范围输出多频激励信号,输出阻抗大于190 kΩ,电流峰峰值为2 mA.数字解调模块可同时提取被测阻抗的实部和虚部信息.结论 采用生物组织等效模型进行的模拟测试验证了本研究系统工作的有效性,为实用化EIT系统的建立奠定了基础.
The Demodulation of weak FSK Signal Based on Duffing Oscillator%基于Duffing振子的微弱FSK信号解调
Institute of Scientific and Technical Information of China (English)
万云朝; 刘才斌; 朱传明
2012-01-01
The method of detecting weak signal based on Duffing oscillator is widely concerned due to its low SNR detection limit.However,it depends on identify the change of phase diagram,and there isn＇t an efficient method to achieve it.In this paper,a new method is proposed to demodulate FSK signal based on Duffing oscillator.It distinguishes two frequencies through the comparison of variance of Duffing oscillator output series,the experiment proves it could detect FSK signal efficiently and is superior to the traditional methods.%基于Duffing振子的信号检测方法由于对微弱信号的检测效果好而受到广泛关注。现有的方法都依赖于对系统状态的准确判断,但目前并没有一种快速准确的系统状态判断方法。本文将Duffing振子应用于FSK信号的解调,通过比较Duffing振子输出序列的方差值,达到解调FSK信号的目的。实验表明该方法能有效检测FSK信号,并且检测效果优于传统的非相干检测方法。
Printed Multi-Turn Loop Antennas for RF Biotelemetry
Simons, Rainee N.; Hall, David G.; Miranda, Felix A.
2007-01-01
Printed multi-turn loop antennas have been designed for contactless powering of, and reception of radio signals transmitted by, surgically implantable biotelemetric sensor units operating at frequencies in the vicinity of 300 MHz.
Padilla, J. M.; Servin, M.; Garnica, G.
2015-05-01
Here we describe a 2-projectors and 1-camera setup for profilometry of discontinuous solids by means of co-phased demodulation of projected fringes and red, green, and blue (RGB) multichannel operation. The dual projection configuration for this profilometer is proposed to solve efficiently specular regions and self-occluding shadows due to discontinuities, which are the main drawbacks for a 1-projector 1-camera configuration. This is because the regions where shadows and specular reflections are generated, and the fringe contrast drops to zero, are in general different for each projection direction; thus, the resulting fringe patterns will have complementary phase information. Multichannel RGB operation allows us to work simultaneously with both projectors and to record independently the complementary fringe patterns phase-modulated by the 3D profile of the object under study. In other words, color encoding/decoding reduces the acquisition time respect to one-at-a-time grayscale operation and, in principle, enables the study of dynamic phenomena. The co-phased demodulation method implemented in this work benefits from the complex (analytic) nature of the output signals estimated with most phase demodulation methods (such as the Fourier method, and temporal phaseshifting algorithms). This allowed us to straightforwardly generate a single phase-map well-defined for the entire area of interest. Finally we assessed our proposed profilometry setup by measuring a fractured spherical cap made of (uncoated) expanded polystyrene. The results were satisfactory but in the authors' opinion this must be considered a preliminary report.
Natively unstructured loops differ from other loops.
Directory of Open Access Journals (Sweden)
Avner Schlessinger
2007-07-01
Full Text Available Natively unstructured or disordered protein regions may increase the functional complexity of an organism; they are particularly abundant in eukaryotes and often evade structure determination. Many computational methods predict unstructured regions by training on outliers in otherwise well-ordered structures. Here, we introduce an approach that uses a neural network in a very different and novel way. We hypothesize that very long contiguous segments with nonregular secondary structure (NORS regions differ significantly from regular, well-structured loops, and that a method detecting such features could predict natively unstructured regions. Training our new method, NORSnet, on predicted information rather than on experimental data yielded three major advantages: it removed the overlap between testing and training, it systematically covered entire proteomes, and it explicitly focused on one particular aspect of unstructured regions with a simple structural interpretation, namely that they are loops. Our hypothesis was correct: well-structured and unstructured loops differ so substantially that NORSnet succeeded in their distinction. Benchmarks on previously used and new experimental data of unstructured regions revealed that NORSnet performed very well. Although it was not the best single prediction method, NORSnet was sufficiently accurate to flag unstructured regions in proteins that were previously not annotated. In one application, NORSnet revealed previously undetected unstructured regions in putative targets for structural genomics and may thereby contribute to increasing structural coverage of large eukaryotic families. NORSnet found unstructured regions more often in domain boundaries than expected at random. In another application, we estimated that 50%-70% of all worm proteins observed to have more than seven protein-protein interaction partners have unstructured regions. The comparative analysis between NORSnet and DISOPRED2 suggested
Natively unstructured loops differ from other loops.
Schlessinger, Avner; Liu, Jinfeng; Rost, Burkhard
2007-07-01
Natively unstructured or disordered protein regions may increase the functional complexity of an organism; they are particularly abundant in eukaryotes and often evade structure determination. Many computational methods predict unstructured regions by training on outliers in otherwise well-ordered structures. Here, we introduce an approach that uses a neural network in a very different and novel way. We hypothesize that very long contiguous segments with nonregular secondary structure (NORS regions) differ significantly from regular, well-structured loops, and that a method detecting such features could predict natively unstructured regions. Training our new method, NORSnet, on predicted information rather than on experimental data yielded three major advantages: it removed the overlap between testing and training, it systematically covered entire proteomes, and it explicitly focused on one particular aspect of unstructured regions with a simple structural interpretation, namely that they are loops. Our hypothesis was correct: well-structured and unstructured loops differ so substantially that NORSnet succeeded in their distinction. Benchmarks on previously used and new experimental data of unstructured regions revealed that NORSnet performed very well. Although it was not the best single prediction method, NORSnet was sufficiently accurate to flag unstructured regions in proteins that were previously not annotated. In one application, NORSnet revealed previously undetected unstructured regions in putative targets for structural genomics and may thereby contribute to increasing structural coverage of large eukaryotic families. NORSnet found unstructured regions more often in domain boundaries than expected at random. In another application, we estimated that 50%-70% of all worm proteins observed to have more than seven protein-protein interaction partners have unstructured regions. The comparative analysis between NORSnet and DISOPRED2 suggested that long
Introduction to Loop Heat Pipes
Ku, Jentung
2015-01-01
This is the presentation file for the short course Introduction to Loop Heat Pipes, to be conducted at the 2015 Thermal Fluids and Analysis Workshop, August 3-7, 2015, Silver Spring, Maryland. This course will discuss operating principles and performance characteristics of a loop heat pipe. Topics include: 1) pressure profiles in the loop; 2) loop operating temperature; 3) operating temperature control; 4) loop startup; 4) loop shutdown; 5) loop transient behaviors; 6) sizing of loop components and determination of fluid inventory; 7) analytical modeling; 8) examples of flight applications; and 9) recent LHP developments.
Transfigured Loop Shaping Controller and its Application to Underwater Vehicle
Institute of Scientific and Technical Information of China (English)
Xian-Ku Zhang; Yi-Cheng Jin
2005-01-01
A kind of transfigured loop shaping controller is presented in this paper. A transfigured loop shaping system puts a controller K in a feedback loop, while putting the dc gain of the controller K on the reference signal line. It is shown through frequency domain analysis and simulation that a transfigured controller can improve the dynamic behavior of a system. The transfigured loop shaping controller method is simple and effective and corresponds to the mixed sensitivity method of robust control theory, which improves the behavior of a system by iterative tuning of weighting functions. Satisfactory control results are obtained when it is applied to the design of an underwater vehicle.
Time Optimal Synchronization Procedure and Associated Feedback Loops
Angoletta, Maria Elena; CERN. Geneva. ATS Department
2016-01-01
A procedure to increase the speed of currently used synchronization loops in a synchrotron by an order of magnitude is presented. Beams dynamics constraint imposes an upper limit on excursions in stable phase angle, and the procedure presented exploits this limit to arrive in the synchronized state from an arbitrary initial state in the fastest possible way. Detailed corrector design for beam phase loop, differential frequency loop and final synchronization loop is also presented. Finally, an overview of the synchronization methods currently deployed in some other CERN’s machines is provided, together with a brief comparison with the newly proposed time-optimal algorithm.
Bojowald, Martin
2013-01-01
Inhomogeneous space-times in loop quantum cosmology have come under better control with recent advances in effective methods. Even highly inhomogeneous situations, for which multiverse scenarios provide extreme examples, can now be considered at least qualitatively.
... part of the stomach) and operations for extreme obesity As a complication of inflammatory bowel disease Diseases such as diabetes or scleroderma may slow down movement in a segment of the intestine, leading to blind loop syndrome.
Brzoska, A M; Negele, J W; Thies, M
2004-01-01
A phenomenological analysis of the distribution of Wilson loops in SU(2) Yang-Mills theory is presented in which Wilson loop distributions are described as the result of a diffusion process on the group manifold. It is shown that, in the absence of forces, diffusion implies Casimir scaling and, conversely, exact Casimir scaling implies free diffusion. Screening processes occur if diffusion takes place in a potential. The crucial distinction between screening of fundamental and adjoint loops is formulated as a symmetry property related to the center symmetry of the underlying gauge theory. The results are expressed in terms of an effective Wilson loop action and compared with various limits of SU(2) Yang-Mills theory.
Neuberger, H
2010-01-01
The generating function for all antisymmetric characters of a Wilson loop matrix in SU(N) Yang Mills theory is the partition function of a fermion living on the curve describing the loop. This generalizes to fermion subsystems living on higher dimensional submanifolds, for example, surfaces. This write-up also contains some extra background, in response to some questions raised during the oral presentation.
Phase locked loops design, simulation, and applications
Best, Roland E
2007-01-01
The Definitive Introduction to Phase-Locked Loops, Complete with Software for Designing Wireless Circuits! The Sixth Edition of Roland Best's classic Phase-Locked Loops has been updated to equip you with today's definitive introduction to PLL design, complete with powerful PLL design and simulation software written by the author. Filled with all the latest PLL advances, this celebrated sourcebook now includes new chapters on frequency synthesis…CAD for PLLs…mixed-signal PLLs…all-digital PLLs…and software PLLs_plus a new collection of sample communications applications. An essential tool for achieving cutting-edge PLL design, the Sixth Edition of Phase-Locked Loops features: A wealth of easy-to-use methods for designing phase-locked loops Over 200 detailed illustrations New to this edition: new chapters on frequency synthesis, including fractional-N PLL frequency synthesizers using sigma-delta modulators; CAD for PLLs, mixed-signal PLLs, all-digital PLLs, and software PLLs; new PLL communications ap...
60-GHz CMOS phase-locked loops
Cheema, Hammad M; van Roermund, Arthur HM
2010-01-01
The promising high data rate wireless applications at millimeter wave frequencies in general and 60 GHz in particular have gained much attention in recent years. However, challenges related to circuit, layout and measurements during mm-wave CMOS IC design have to be overcome before they can become viable for mass market. ""60-GHz CMOS Phase-Locked Loops"" focusing on phase-locked loops for 60 GHz wireless transceivers elaborates these challenges and proposes solutions for them. The system level design to circuit level implementation of the complete PLL, along with separate implementations of i
Li, Hongqiang; Zhou, Wenqian; Liu, Yu; Dong, Xiaye; Zhang, Cheng; Miao, Changyun; Zhang, Meiling; Li, Enbang; Tang, Chunxiao
2014-01-01
An arrayed waveguide grating (AWG) demodulation integration microsystem is investigated in this study. The system consists of a C-band on-chip LED, a 2 × 2 silicon nanowire-based coupler, a fiber Bragg grating (FBG) array, a 1 × 8 AWG, and a photoelectric detector array. The coupler and AWG are made from silicon-on-insulator wafers using electron beam exposure and response-coupled plasma technology. Experimental results show that the excess loss in the MMI coupler with a footprint of 6 × 100 μm2 is 0.5423 dB. The 1 × 8 AWG with a footprint of 267 × 381 μm2 and a waveguide width of 0.4 μm exhibits a central channel loss of −3.18 dB, insertion loss non-uniformity of −1.34 dB, and crosstalk level of −23.1 dB. The entire system is preliminarily tested. Wavelength measurement precision is observed to reach 0.001 nm. The wavelength sensitivity of each FBG is between 0.04 and 0.06 nm/dB. PMID:24797561
A derivative based simplified phase tracker for a single fringe pattern demodulation
Deepan, B.; Quan, C.; Tay, C. J.
2016-08-01
In this paper, a novel fringe demodulation method for the estimation of phase and its first-order derivative from a closed-fringe interferogram is proposed. The proposed method determines the phase derivatives in both x&y directions from fringe orientation and density. The phase derivatives are subsequently used to determine phase values using a novel simplified phase tracker. In the phase tracking model, the complexity of the cost function is reduced using predetermined derivatives so computation time required for phase tracking is reduced considerably. The proposed model is more robust while dealing with saddle points in fringes than the conventional phase tracker model. Hence it does not require any specialized scanning strategy. The proposed method is validated with simulated and experimental fringe patterns (obtained using electronic speckle pattern interferometry and optical holographic interferometry) and a comparison study is carried out with conventional regularized phase tracker. The simulation results show that the proposed method has good accuracy and requires less computation time than existing phase-tracking algorithms. The experimental results demonstrate the robustness of the proposed method against speckle noise and its practical applicability for static and dynamic applications.
An Energy Demodulation Based Fiber Optic Sensing System for Landslide Early-Warning
Directory of Open Access Journals (Sweden)
Xing Wang
2017-07-01
Full Text Available To help reduce the impact of geo-hazards, an innovative landslide early-warning technology based on an energy demodulation-based fiber optic sensing (FOS-LW for short technology, is introduced in this paper. FOS-LW measures the energy change in a sensing fiber at the segment of micro-bending, which can be caused by landslide movements, and automatically raises an alarm as soon as the measured signal intensity in the fiber reaches a pre-set threshold. Based on the sensing of micro-bending losses in the fiber optics, a two-event sensing algorithm has been developed for the landslide early-warning. The feasibility of the FOS-LW technology is verified through laboratory simulation and field tests. The result shows that FOS-LW has some unique features—such as the graded alarm, real-time responses, remote monitoring, low cost and passive optical network—and can be applied in the early-warning of landslides.
Lize, Yannick K; Christen, Louis; Nazarathy, Moshe; Nuccio, Scott; Wu, Xiaoxia; Willner, Alan E; Kashyap, Raman
2007-05-28
We present an optical multipath error correction technique for differentially encoded modulation formats such as differential-phase-shift-keying (DPSK) and differential polarization shift keying (DPolSK) for fiber-based and free-space communication. This multipath error correction method combines optical and electronic logic gates. The scheme can easily be implemented using commercially available interferometers and high speed logic gates and does not require any data overhead therefore does not affect the effective bandwidth of the transmitted data. It is not merely compatible but also complementary to error correction codes commonly used in optical transmission systems such as forward-error-correction (FEC). The technique consists of separating the demodulation at the receiver in multiple paths. Each path consists of a Mach-Zehnder interferometer with a different integer bit delay used in each path. Some basic logic operations follow and the three paths are compared using a simple majority vote algorithm. Experimental results show that the scheme improves receiver sensitivity by 1.5 dB at BER of 10(-3),in back-to-back configuration. Numerical results indicate a 1.6 dB improvement in the presence of Chromatic Dispersion for a 25% increase in tolerance for a 3dB penalty from +/-1220 ps/nm to +/-1520 ps/nm. and a 0.35 dB improvement for back-to-back operation.
Rapid extraction of the phase shift of the cold-atom interferometer via phase demodulation
Institute of Scientific and Technical Information of China (English)
程冰; 王兆英; 许翱鹏; 王启宇; 林强
2015-01-01
Generally, the phase of the cold-atom interferometer is extracted from the atomic interference fringe, which can be obtained by scanning the chirp rate of the Raman lasers at a given interrogation time T . If mapping the phase shift for each T with a series of measurements, the extraction time is limited by the protocol of each T measurement, and therefore increases dramatically when doing fine mapping with a small step of T . Here we present a new method for rapid extraction of the phase shift via phase demodulation. By using this method, the systematic shifts can be mapped though the whole interference area. This method enables quick diagnostics of the potential cause of the phase shift in specific time. We demonstrate experimentally that this method is effective for the evaluation of the systematic errors of the cold atomic gravimeter. The systematic phase error induced by the quadratic Zeeman effect in the free-falling region is extracted by this method. The measured results correspond well with the theoretic prediction and also agree with the results obtained by the fringe fitting method for each T .
Genetic Programming with Simple Loops
Institute of Scientific and Technical Information of China (English)
QI Yuesheng; WANG Baozhong; KANG Lishan
1999-01-01
A kind of loop function LoopN inGenetic Programming (GP) is proposed.Different from other forms of loopfunction, such as While-Do and Repeat-Until, LoopNtakes only oneargument as its loop body and makes its loop body simply run N times,soinfinite loops will never happen. The problem of how to avoid too manylayers ofloops in Genetic Programming is also solved. The advantage ofLoopN in GP is shown bythe computational results in solving the mowerproblem.
Closed-loop approach to thermodynamics
Goupil, C; Herbert, E; Benenti, G; D'Angelo, Y; Lecoeur, Ph
2016-01-01
We present the closed-loop approach to linear nonequilibrium thermodynamics considering a generic heat engine dissipatively connected to two temperature baths. The system is usually quite generally characterized by two parameters: the output power $P$ and the conversion efficiency $\\eta$, to which we add a third one, the working frequency $\\omega$. We establish that a detailed understanding of the effects of the dissipative coupling on the energy conversion process, necessitates the knowledge of only two quantities: the system's feedback factor $\\beta$ and its open-loop gain $A_{0}$, the product of which, $A_{0}\\beta$, characterizes the interplay between the efficiency, the output power and the operating rate of the system. The feedback loop approach thus provides a versatile and economical, hence efficient, tool for the study of any conversion engine operation for which a feedback factor may be defined as illustrated with a thermoelectric system.
Closed-loop approach to thermodynamics
Goupil, C.; Ouerdane, H.; Herbert, E.; Benenti, G.; D'Angelo, Y.; Lecoeur, Ph.
2016-09-01
We present the closed-loop approach to linear nonequilibrium thermodynamics considering a generic heat engine dissipatively connected to two temperature baths. The system is usually quite generally characterized by two parameters: the output power P and the conversion efficiency η , to which we add a third one, the working frequency ω . We establish that a detailed understanding of the effects of the dissipative coupling on the energy conversion process requires only knowing two quantities: the system's feedback factor β and its open-loop gain A0, which product A0β characterizes the interplay between the efficiency, the output power, and the operating rate of the system. By raising the abstract hermodynamic analysis to a higher level, the feedback loop approach provides a versatile and economical, hence fairly efficient, tool for the study of any conversion engine operation for which a feedback factor can be defined.
Optimized Design of the Shielded-Loop Resonator
DEFF Research Database (Denmark)
Stensgaard, Anders
1996-01-01
The shielded-loop resonator is known to have low capacitive sample loss due to perfect balancing. We present a new analysis of the unbalanced driven shielded-loop resonator that calculates the resonance frequencies and also determines some design considerations. The analysis enables us to optimiz...... the use of this resonator. Theory and design considerations are shown to agree with observations in measurements on two coils, with various sizes and frequencies......The shielded-loop resonator is known to have low capacitive sample loss due to perfect balancing. We present a new analysis of the unbalanced driven shielded-loop resonator that calculates the resonance frequencies and also determines some design considerations. The analysis enables us to optimize...
Institute of Scientific and Technical Information of China (English)
邢浩江; 张东来; 李铁才; 王子才
2012-01-01
针对目前光伏并网逆变器存在基波电压定向偏差、直流电压崩溃以及逆变器并网对电网产生冲击的问题,提出一种基于电网电压基波锁相环技术的三环控制方法,应用于单级式光伏并网逆变器,提高逆变器输出性能,并实现柔性并网.该方法首先基于电网电压基波的锁相环技术,实现对电网电压基波分量定向,定向效果取决于锁相环的设计性能;其次采用三环控制结构避免直流电压崩溃问题,减小输出电流总谐波因数;最后采用合理的并网控制逻辑,实现光伏逆变器柔性并网.实验验证了该方法的可行性,可提高系统动态响应实时性与稳态跟踪精度,实现系统高可靠运行.%In allusion to orientation deviation of grid fundamental frequency voltage and DC voltage collapse of existing grid-connecting photovoltaic (PV) inverter and the impact to power grid due to grid-connection of photovoltaic inverter, a three-loop control method based on phase-locked loop (PLL) control for grid fundamental frequency voltage was proposed and applied to single-stage grid-connecting PV inverter to improve output performance of the inverter and implement flexible grid-connection. Firstly, based on PLL control for grid fundamental frequency voltage, the orientation of grid fundamental frequency voltage was performed and the effect of the orientation was dependent on the designed performance of the PLL; secondly, the three loop-control structure was adopted to avoid DC voltage collapse and decrease total harmonic factor of output current; finally reasonable grid-connecting control logic was adopted to implement flexible grid-connection of PV inverter. The feasibility of the proposed method was verified by experiments, and experiment results showed that using the proposed method both real-time performance of dynamic response and steady state tracking accuracy could be improved.
Institute of Scientific and Technical Information of China (English)
郇浩; 陶选如; 陶然; 程小康; 董朝; 李鹏飞
2014-01-01
To reach a compromise between efficient dynamic performance and high tracking accuracy of carrier tracking loop in high-dynamic circumstance which results in large Doppler frequency and Doppler frequency rate-of-change, a fast maximum likelihood estimation method of Doppler frequency rate-of-change is proposed in this paper, and the estimation value is utilized to aid the carrier tracking loop. First, it is pointed out that the maximum likelihood estimation method of Doppler frequency and Doppler frequency rate-of-change is equivalent to the Fractional Fourier Fransform (FrFT). Second, the estimation method of Doppler frequency rate-of-change, which combines the instant self-correlation and the segmental Discrete Fourier Transform (DFT) is proposed to solve the large two-dimensional search calculation amount of the Doppler frequency and Doppler frequency rate-of-change, and the received coarse estimation value is applied to narrow down the search range. Finally, the estimation value is used in the carrier tracking loop to reduce the dynamic stress and improve the tracking accuracy. Theoretical analysis and computer simulation show that the search calculation amount falls to 5.25 percent of the original amount with Signal to Noise Ratio (SNR)-30 dB, and the Root Mean Sguare Error(RMSE) of frequency tracked is only 8.46 Hz/s, compared with the traditional carrier tracking method the tracking sensitivity can be improved more than 3 dB.%高动态环境下接收信号含有较大的多普勒频率及其变化率，传统载波跟踪方法难以在高动态应力和跟踪精度两方面取得较好折中，针对这一问题该文提出一种多普勒频率变化率快速最大似然估计方法，并利用估计值辅助载波跟踪环路。首先指出了多普勒频率及其变化率的最大似然估计可等效采用分数阶傅里叶变换(FrFT)来实现；其次，针对频率及其变化率2维搜索运算量大的问题，提出一种瞬时自相关与分段离
Demodulation and Simulation of VOR Signal Based on Software Radio%基于软件无线电原理VOR信号解调与仿真
Institute of Scientific and Technical Information of China (English)
张建明
2013-01-01
According to the brief introduction of the VOR principle and signal characteristics, the demodulation of VOR signal is analyzed based on the principle of software radio. The demodulations include reference phase signal demodulation and variable phase signal demodulation The calculation of azimuth angle and voice information are realized and the system is simulated rely on the analysis by applying MATLAB software. Some factors which have the influence on the precision of signal demodulation are put out in this paper, the foundations are provided for the design of VOR receiver.%通过简要介绍VOR系统原理及信号特性，基于软件无线电原理对VOR信号解调作了较详细的分析，其中包括基准相位信号解调、可变相位信号的解调，实现角度及音频信息的解算，并进行了系统仿真，对影响信号解调精度的因素做了分析，为 VOR 接收机的设计提供了依据。
Radio Pulsating Structures with Coronal Loop Contraction
Kallunki, J.; Pohjolainen, S.
2012-10-01
We present a multi-wavelength study of a solar eruption event on 20 July 2004, comprising observations in Hα, EUV, soft X-rays, and in radio waves with a wide frequency range. The analyzed data show both oscillatory patterns and shock wave signatures during the impulsive phase of the flare. At the same time, large-scale EUV loops located above the active region were observed to contract. Quasi-periodic pulsations with ˜ 10 and ˜ 15 s oscillation periods were detected both in microwave - millimeter waves and in decimeter - meter waves. Our calculations show that MHD oscillations in the large EUV loops - but not likely in the largest contracting loops - could have produced the observed periodicity in radio emission, by triggering periodic magnetic reconnection and accelerating particles. As the plasma emission in decimeter - meter waves traces the accelerated particle beams and the microwave emission shows a typical gyrosynchrotron flux spectrum (emission created by trapped electrons within the flare loop), we find that the particles responsible for the two different types of emission could have been accelerated in the same process. Radio imaging of the pulsed decimetric - metric emission and the shock-generated radio type II burst in the same wavelength range suggest a rather complex scenario for the emission processes and locations. The observed locations cannot be explained by the standard model of flare loops with an erupting plasmoid located above them, driving a shock wave at the CME front.
Bena, I; Kosower, D A; Roiban, R; Bena, Iosif; Bern, Zvi; Kosower, David A.; Roiban, Radu
2004-01-01
We elucidate the one-loop twistor-space structure corresponding to momentum-space MHV diagrams. We also discuss the infrared divergences, and argue that only a limited set of MHV diagrams contain them. We show how to introduce a twistor-space regulator corresponding to dimensional regularization for the infrared-divergent diagrams. We also evaluate explicitly the `holomorphic anomaly' pointed out by Cachazo, Svrcek, and Witten, and use the result to define modified differential operators which can be used to probe the twistor-space structure of one-loop amplitudes.
Closed Loop Subspace Identification
Directory of Open Access Journals (Sweden)
Geir W. Nilsen
2005-07-01
Full Text Available A new three step closed loop subspace identifications algorithm based on an already existing algorithm and the Kalman filter properties is presented. The Kalman filter contains noise free states which implies that the states and innovation are uneorre lated. The idea is that a Kalman filter found by a good subspace identification algorithm will give an output which is sufficiently uncorrelated with the noise on the output of the actual process. Using feedback from the output of the estimated Kalman filter in the closed loop system a subspace identification algorithm can be used to estimate an unbiased model.
Chiou, Dah-Wei
2014-01-01
This article presents an "in-a-nutshell" yet self-contained introductory review on loop quantum gravity (LQG) -- a background-independent, nonperturbative approach to a consistent quantum theory of gravity. Instead of rigorous and systematic derivations, it aims to provide a general picture of LQG, placing emphasis on the fundamental ideas and their significance. The canonical formulation of LQG, as the central topic of the article, is presented in a logically orderly fashion with moderate details, while the spin foam theory, black hole thermodynamics, and loop quantum cosmology are covered briefly. Current directions and open issues are also summarized.
Sensing and Demodulation of Special Long-Period Fiber Gratings Induced by Scanning CO2 Laser Pulses
Directory of Open Access Journals (Sweden)
Tao Zhu
2012-01-01
Full Text Available A review of long-period fiber gratings (LPFGs with special structures induced by scanning CO2 laser pulses in single mode fiber (SMF is presented in this paper. In the first part, the special structures and fabrication methods of LPFGs are demonstrated in detail. Next, the special LPFG-based sensors are demonstrated, such as refractive index sensor, strain sensor with temperature compensation, and torsion sensor without temperature crosstalking. Finally, several investigation methods including intensity, wavelength shift, and fiber ring laser demodulation are discussed.
Directory of Open Access Journals (Sweden)
Rovelli Carlo
1998-01-01
Full Text Available The problem of finding the quantum theory of the gravitational field, and thus understanding what is quantum spacetime, is still open. One of the most active of the current approaches is loop quantum gravity. Loop quantum gravity is a mathematically well-defined, non-perturbative and background independent quantization of general relativity, with its conventional matter couplings. Research in loop quantum gravity today forms a vast area, ranging from mathematical foundations to physical applications. Among the most significant results obtained are: (i The computation of the physical spectra of geometrical quantities such as area and volume, which yields quantitative predictions on Planck-scale physics. (ii A derivation of the Bekenstein-Hawking black hole entropy formula. (iii An intriguing physical picture of the microstructure of quantum physical space, characterized by a polymer-like Planck scale discreteness. This discreteness emerges naturally from the quantum theory and provides a mathematically well-defined realization of Wheeler's intuition of a spacetime ``foam''. Long standing open problems within the approach (lack of a scalar product, over-completeness of the loop basis, implementation of reality conditions have been fully solved. The weak part of the approach is the treatment of the dynamics: at present there exist several proposals, which are intensely debated. Here, I provide a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.
Reversible hysteresis loop tuning
Berger, A.; Binek, Ch.; Margulies, D. T.; Moser, A.; Fullerton, E. E.
2006-02-01
We utilize antiferromagnetically coupled bilayer structures to magnetically tune hysteresis loop properties. Key element of this approach is the non-overlapping switching field distribution of the two magnetic layers that make up the system: a hard magnetic CoPtCrB layer (HL) and a soft magnetic CoCr layer (SL). Both layers are coupled antiferromagnetically through an only 0.6-nm-thick Ru interlayer. The non-overlapping switching field distribution allows the measurement of magnetization reversal in the SL at low fields while keeping the magnetization state of the HL unperturbed. Applying an appropriate high field or high field sequence changes the magnetic state of the HL, which then influences the SL magnetization reversal due to the interlayer coupling. In this way, the position and shape of the SL hysteresis loop can be changed or tuned in a fully reversible and highly effective manner. Here, we study specifically how the SL hysteresis loop characteristics change as we move the HL through an entire high field hysteresis loop sequence.
Servin, M; Garnica, G; Estrada, J C; Quiroga, A
2013-10-21
Fringe projection profilometry is a well-known technique to digitize 3-dimensional (3D) objects and it is widely used in robotic vision and industrial inspection. Probably the single most important problem in single-camera, single-projection profilometry are the shadows and specular reflections generated by the 3D object under analysis. Here a single-camera along with N-fringe-projections is (digital) coherent demodulated in a single-step, solving the shadows and specular reflections problem. Co-phased profilometry coherently phase-demodulates a whole set of N-fringe-pattern perspectives in a single demodulation and unwrapping process. The mathematical theory behind digital co-phasing N-fringe-patterns is mathematically similar to co-phasing a segmented N-mirror telescope.
SEMICONDUCTOR INTEGRATED CIRCUITS: A low power automatic gain control loop for a receiver
Guofeng, Li; Zhiqing, Geng; Nanjian, Wu
2010-09-01
This paper proposes a new structure to lower the power consumption of a variable gain amplifier (VGA) and keep the linearity of the VGA unchanged. The structure is used in a high rate amplitude-shift keying (ASK) based IF-stage. It includes an automatic gain control (AGC) loop and ASK demodulator. The AGC mainly consists of six-stage VGAs. The IF-stage is realized in 0.18 μm CMOS technology. The measurement results show that the power consumption of the whole system is very low. The system consumes 730 μA while operating at 1.8 V. The minimum ASK signal the system could detect is 0.7 mV (peak to peak amplitude).
Fast-sausage oscillations in coronal loops with smooth boundary
Lopin, I.; Nagorny, I.
2014-12-01
Aims: The effect of the transition layer (shell) in nonuniform coronal loops with a continuous radial density profile on the properties of fast-sausage modes are studied analytically and numerically. Methods: We modeled the coronal waveguide as a structured tube consisting of a cord and a transition region (shell) embedded within a magnetic uniform environment. The derived general dispersion relation was investigated analytically and numerically in the context of frequency, cut-off wave number, and the damping rate of fast-sausage oscillations for various values of loop parameters. Results: The frequency of the global fast-sausage mode in the loops with a diffuse (or smooth) boundary is determined mainly by the external Alfvén speed and longitudinal wave number. The damping rate of such a mode can be relatively low. The model of coronal loop with diffuse boundary can support a comparatively low-frequency, global fast-sausage mode of detectable quality without involving extremely low values of the density contrast. The effect of thin transition layer (corresponds to the loops with steep boundary) is negligible and produces small reductions of oscillation frequency and relative damping rate in comparison with the case of step-function density profile. Seismological application of obtained results gives the estimated Alfvén speed outside the flaring loop about 3.25 Mm/s.
Fingerprints of Galactic Loop I on the Cosmic Microwave Background
DEFF Research Database (Denmark)
Liu, Hao; Mertsch, Philipp; Sarkar, Subir
2014-01-01
We investigate possible imprints of galactic foreground structures such as the "radio loops" in the derived maps of the cosmic microwave background. Surprisingly, there is evidence for these not only at radio frequencies through their synchrotron radiation, but also at microwave frequencies where...
Fingerprints of Galactic Loop I on the Cosmic Microwave Background
DEFF Research Database (Denmark)
Liu, Hao; Mertsch, Philipp; Sarkar, Subir
2014-01-01
We investigate possible imprints of galactic foreground structures such as the "radio loops" in the derived maps of the cosmic microwave background. Surprisingly, there is evidence for these not only at radio frequencies through their synchrotron radiation, but also at microwave frequencies where...... due to primordial gravitational waves from inflation....
Two-loop and n-loop eikonal vertex corrections
Kidonakis, Nikolaos
2003-01-01
I present calculations of two-loop vertex corrections with massive and massless partons in the eikonal approximation. I show that the $n$-loop result for the UV poles can be given in terms of the one-loop calculation.
DEFF Research Database (Denmark)
Guerrero Gonzalez, Neil; Caballero Jambrina, Antonio; Amaya Fernández, Ferney Orlando
2009-01-01
Highest reported bit rate of 2.5 Gbit/s for optically phase modulated radio-over-fibre link employing coherent detection is demonstrated. Demodulation of 3·2.5 Gbit/s QPSK modulated WDM channels, is achieved after 79km of transmission through deployed fiber.......Highest reported bit rate of 2.5 Gbit/s for optically phase modulated radio-over-fibre link employing coherent detection is demonstrated. Demodulation of 3·2.5 Gbit/s QPSK modulated WDM channels, is achieved after 79km of transmission through deployed fiber....
All-digital signal-processing open-loop fiber-optic gyroscope with enlarged dynamic range.
Wang, Qin; Yang, Chuanchuan; Wang, Xinyue; Wang, Ziyu
2013-12-15
We propose and realize a new open-loop fiber-optic gyroscope (FOG) with an all-digital signal-processing (DSP) system where an all-digital phase-locked loop is employed for digital demodulation to eliminate the variation of the source intensity and suppress the bias drift. A Sagnac phase-shift tracking method is proposed to enlarge the dynamic range, and, with its aid, a new open-loop FOG, which can achieve a large dynamic range and high sensitivity at the same time, is realized. The experimental results show that compared with the conventional open-loop FOG with the same fiber coil and optical devices, the proposed FOG reduces the bias instability from 0.259 to 0.018 deg/h, and the angle random walk from 0.031 to 0.006 deg/h(1/2), moreover, enlarges the dynamic range to ±360 deg/s, exceeding the maximum dynamic range ±63 deg/s of the conventional open-loop FOG.
Near-Field Loop Antenna for the UHF RFID Reader
Institute of Scientific and Technical Information of China (English)
Peng Yang; Yan Li; Li-Jun Jiang; Feng Yang
2011-01-01
A loop antenna for near field readers is proposed.Through periodic interdigital capacitors,the phase of the current on the loop is compensated and kept in phase.Hence,a loop with a perimeter of one wavelength at 900 MHz achieves a uniform near magnetic field distribution inside the loop.A novel method is proposed to evaluate the performance of the coplanar waveguide (CPW) to coplanar stripline (CPS) transition,which is used as a balun for the feeding network in this paper.This loop antenna has a 70 MHz operating bandwidth and 12 cm maximum reading range when the output power is 24 dBm,which is suitable for most near field radio frequency identification (RFID) applications.
Franetič, Damir
2015-01-01
We study loop near-rings, a generalization of near-rings, where the additive structure is not necessarily associative. We introduce local loop near-rings and prove a useful detection principle for localness.
Directory of Open Access Journals (Sweden)
Ahmad Ghasemloonia
2011-01-01
Full Text Available The role of gears in industry for speed and torque variation purposes is obvious. The gearbox diagnostic methods have been improved quickly in recent years. In this paper, two of the newest methods, the resonance demodulation technique (R.D, and the instantaneous power spectrum technique (IPS are applied to gearbox vibration signals and their capabilities in fault detection are compared. Yet, the important role of time averaging should not be dispensed with, as it is the primary step for both techniques. In the present study, the mathematical method of these techniques, according to the mathematical vibration model of gears, is introduced, these techniques are applied to the test rig data, and finally the results of both methods are compared. The results indicate that in each method, the location of fault can be estimated and it is located in the same angular position in both methods. The IPS method is applicable to severe faults, whereas the resonance demodulation technique is a simple tool to recognize the fault at each severity and at the early stages of fault generation.
Directory of Open Access Journals (Sweden)
Ji Xia
2015-07-01
Full Text Available An optical fiber current sensor based on Fabry-Perot interferometer using a fiber Bragg grating demodulation is proposed. Magnetic fluid is used as a sensitive medium in fiber optical Fabry-Perot (F-P cavity for the optical characteristic of magnetic-controlled refractive index. A Fiber Bragg grating (FBG is connected after the F-P interferometer which is used to reflect the optical power at the Bragg wavelength of the interference transmission spectrum. The corresponding reflective power of the FBG will change with different external current intensity, due to the shift on the interference spectrum of the F-P interferometer. The sensing probe has the advantages of convenient measurement for its demodulation, low cost and high current measurement accuracy on account of its sensing structure. Experimental results show that an optimal sensitivity of 0.8522 nw/A and measurement resolution of 0.001 A is obtained with a FBG at 1550 nm with 99% reflectivity.
Griego, J R
1995-01-01
Some features of extended loops are considered. In particular, the behaviour under diffeomorphism transformations of the wavefunctions with support on the extended loop space are studied. The basis of a method to obtain analytical expressions of diffeomorphism invariants via extended loops are settled. Applications to knot theory and quantum gravity are considered.
DEFF Research Database (Denmark)
Prosman, Ernst-Jan; Wæhrens, Brian Vejrum; Liotta, Giacomo
2017-01-01
Replacing virgin materials with waste materials, a practice known as Industrial Symbiosis (IS), has been identified as a key strategy for closing material loops. This article adopts a critical view on geographic proximity and external coordinators – two key enablers of IS. By ‘uncovering’ a case...... where both enablers are absent, this study seeks to explore firm-level challenges of IS. We adopt an exploratory case study approach at a cement manufacturer who engages in cross-border IS without the support of external coordinators. Our research presents insights into two key areas of IS: 1) setting...... for geographic proximity and external coordinators. In doing so, our insights into firm-level challenges of long-distance IS exchanges contribute to closing global material loops by increasing the number of potential circular pathways....
Loop quantum gravity and black hole entropy quantization
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
Using the spin networks and the asymptotic quasinormal mode frequencies of black holes given by loop quantum gravity,the minimum horizon area gap is obtained.Then the quantum area spectrum of black holes is derived and the black hole entropy is a realized quantization.The results show that the black hole entropy given by loop quantum gravity is in full accord with the Bekenstein-Hawking entropy with a suitable Immirzi.
Loop quantum gravity and black hole entropy quantization
Institute of Scientific and Technical Information of China (English)
LI ChuanAn; JIANG JiJian; SU JiuQing
2009-01-01
Using the spin networks and the asymptotic quasinormal mode frequencies of black holes given by loop quantum gravity, the minimum horizon area gap is obtained. Then the quantum area spectrum of black holes is derived and the black hole entropy is a realized quantization. The results show that the black hole entropy given by loop quantum gravity is in full accord with the Bekenstein-Hawking entropy with a suitable Immirzi.
Designing Estimator/Predictor Digital Phase-Locked Loops
Statman, J. I.; Hurd, W. J.
1988-01-01
Signal delays in equipment compensated automatically. New approach to design of digital phase-locked loop (DPLL) incorporates concepts from estimation theory and involves decomposition of closed-loop transfer function into estimator and predictor. Estimator provides recursive estimates of phase, frequency, and higher order derivatives of phase with respect to time, while predictor compensates for delay, called "transport lag," caused by PLL equipment and by DPLL computations.
Self-oscillating loop based piezoelectric power converter
Rødgaard, Martin Schøler; Andersen, Michael A. E.; Esbern, Andreas; Meyer, Kasper Sinding
2013-01-01
The present invention relates to a piezoelectric power converter comprising an input driver electrically coupled directly to an input or primary electrode of the piezoelectric transformer without any intervening series or parallel inductor. A feedback loop is operatively coupled between an output voltage of the piezoelectric transformer and the input driver to provide a self-oscillation loop around a primary section of the piezoelectric transformer oscillating at an excitation frequency. Elec...
Directory of Open Access Journals (Sweden)
Bojowald Martin
2008-07-01
Full Text Available Quantum gravity is expected to be necessary in order to understand situations in which classical general relativity breaks down. In particular in cosmology one has to deal with initial singularities, i.e., the fact that the backward evolution of a classical spacetime inevitably comes to an end after a finite amount of proper time. This presents a breakdown of the classical picture and requires an extended theory for a meaningful description. Since small length scales and high curvatures are involved, quantum effects must play a role. Not only the singularity itself but also the surrounding spacetime is then modified. One particular theory is loop quantum cosmology, an application of loop quantum gravity to homogeneous systems, which removes classical singularities. Its implications can be studied at different levels. The main effects are introduced into effective classical equations, which allow one to avoid the interpretational problems of quantum theory. They give rise to new kinds of early-universe phenomenology with applications to inflation and cyclic models. To resolve classical singularities and to understand the structure of geometry around them, the quantum description is necessary. Classical evolution is then replaced by a difference equation for a wave function, which allows an extension of quantum spacetime beyond classical singularities. One main question is how these homogeneous scenarios are related to full loop quantum gravity, which can be dealt with at the level of distributional symmetric states. Finally, the new structure of spacetime arising in loop quantum gravity and its application to cosmology sheds light on more general issues, such as the nature of time.
Directory of Open Access Journals (Sweden)
Bojowald Martin
2005-12-01
Full Text Available Quantum gravity is expected to be necessary in order to understand situations where classical general relativity breaks down. In particular in cosmology one has to deal with initial singularities, i.e., the fact that the backward evolution of a classical space-time inevitably comes to an end after a finite amount of proper time. This presents a breakdown of the classical picture and requires an extended theory for a meaningful description. Since small length scales and high curvatures are involved, quantum effects must play a role. Not only the singularity itself but also the surrounding space-time is then modified. One particular realization is loop quantum cosmology, an application of loop quantum gravity to homogeneous systems, which removes classical singularities. Its implications can be studied at different levels. Main effects are introduced into effective classical equations which allow to avoid interpretational problems of quantum theory. They give rise to new kinds of early universe phenomenology with applications to inflation and cyclic models. To resolve classical singularities and to understand the structure of geometry around them, the quantum description is necessary. Classical evolution is then replaced by a difference equation for a wave function which allows to extend space-time beyond classical singularities. One main question is how these homogeneous scenarios are related to full loop quantum gravity, which can be dealt with at the level of distributional symmetric states. Finally, the new structure of space-time arising in loop quantum gravity and its application to cosmology sheds new light on more general issues such as time.
Energy Technology Data Exchange (ETDEWEB)
Schaffer, Jr.; W.F.
1958-04-30
The schedule for the installation of the PAR slurry loop experiment in the South Facility of the ORR has been reviewed and revised. The design, fabrications and Installation is approximately two weeks behind schedule at this time due to many factors; however, indications are that this time can be made up. Design is estimated to be 75% complete, fabrication 32% complete and installation 12% complete.
The new BNL AGS phase, radial and synchronization loops
Energy Technology Data Exchange (ETDEWEB)
Onillon, E.; Brennan, J.M.
1996-07-01
The AGS and the RHIC must be synchronized before bunch-to-bucket transfer of the beam. A feedback loop has been designed and an improvement has been made to the AGS phase and radial loops. In both cases, the design uses a state variable representation to achieve greater stability and smaller errors. The state variables are beam phase, frequency and radius , the integral of the difference between the radius and its reference and the phase deviation of the bunch from the synchronous phase. Furthermore, the feedback gains are programmed as a function of the beam parameters to keep the same loop performances through the acceleration cycle.
Verification of Loop Diagnostics
Winebarger, A.; Lionello, R.; Mok, Y.; Linker, J.; Mikic, Z.
2014-01-01
Many different techniques have been used to characterize the plasma in the solar corona: density-sensitive spectral line ratios are used to infer the density, the evolution of coronal structures in different passbands is used to infer the temperature evolution, and the simultaneous intensities measured in multiple passbands are used to determine the emission measure. All these analysis techniques assume that the intensity of the structures can be isolated through background subtraction. In this paper, we use simulated observations from a 3D hydrodynamic simulation of a coronal active region to verify these diagnostics. The density and temperature from the simulation are used to generate images in several passbands and spectral lines. We identify loop structures in the simulated images and calculate the loop background. We then determine the density, temperature and emission measure distribution as a function of time from the observations and compare with the true temperature and density of the loop. We find that the overall characteristics of the temperature, density, and emission measure are recovered by the analysis methods, but the details of the true temperature and density are not. For instance, the emission measure curves calculated from the simulated observations are much broader than the true emission measure distribution, though the average temperature evolution is similar. These differences are due, in part, to inadequate background subtraction, but also indicate a limitation of the analysis methods.
Cosmic string loop microlensing
Bloomfield, Jolyon K.; Chernoff, David F.
2014-06-01
Cosmic superstring loops within the galaxy microlens background point sources lying close to the observer-string line of sight. For suitable alignments, multiple paths coexist and the (achromatic) flux enhancement is a factor of two. We explore this unique type of lensing by numerically solving for geodesics that extend from source to observer as they pass near an oscillating string. We characterize the duration of the flux doubling and the scale of the image splitting. We probe and confirm the existence of a variety of fundamental effects predicted from previous analyses of the static infinite straight string: the deficit angle, the Kaiser-Stebbins effect, and the scale of the impact parameter required to produce microlensing. Our quantitative results for dynamical loops vary by O(1) factors with respect to estimates based on infinite straight strings for a given impact parameter. A number of new features are identified in the computed microlensing solutions. Our results suggest that optical microlensing can offer a new and potentially powerful methodology for searches for superstring loop relics of the inflationary era.
Institute of Scientific and Technical Information of China (English)
孙绍华; 刘博; 贲洪奇; 孟涛; 张金永
2014-01-01
为了应对电网发生电压跌落、频率突变、谐波污染等电网畸变条件，该文为并网逆变器提供了一种新的基于快速正负序分离算法的自适应锁频环同步技术。基于自适应陷波器的锁频环本质上是一个2阶陷波器，加上非线性微分方程后可以实现基波频率跟踪，实现电网信号的同步，前提条件是电网无扰动和谐波。电网发生畸变时，为了抑制扰动和谐波，提出了一种快速正负序分离算法，结合自适应陷波器，改进后的自适应锁频环同步技术利用简单的矩阵运算，可以在5个采样周期内实现正、负序分量及各次谐波的快速分离。与1/4周期延时的传统锁相环相比，该方法无需压控振荡器，无需比例积分参数调试，简化了系统的结构，实现了频率的自动跟踪，消除了系统检测误差，提高了系统的动态性能。文中对所提锁频方案进行了详细的理论分析，最后仿真和实验结果验证了所提方法的可行性及良好的暂态特性。%This paper investigates and presents a new adaptive frequency locked loop synchronization scheme based on fast positive-negative sequences decomposition for grid-connected power converters under distorted grid conditions, such as voltage dip, frequency change and harmonic distortion and so on. The frequency locked loop (FLL) based on adaptive notch filter (ANF) is a second-order notch filter that is further furnished with a nonlinear differential equation to track the fundamental frequency of the grid signal without disturbances or harmonics. For noise reduction purpose under distorted grid conditions, a fast positive-negative sequences decomposition (FPNSD) algorithm is proposed;collaborating with ANF, the modified ANF-based synchronization technique can extract the positive-negative sequences and low order harmonics exactly in 5 sampling periods by matrix operation. Unlike the traditional algorithm based on
Control-structure interaction in precision pointing servo loops
Spanos, John T.
1989-01-01
The control-structure interaction problem is addressed via stability analysis of a generic linear servo loop model. With the plant described by the rigid body mode and a single elastic mode, structural flexibility is categorized into one of three types: (1) appendage, (2) in-the-loop minimum phase, and (3) in-the-loop nonminimum phase. Closing the loop with proportional-derivative (PD) control action and introducing sensor roll-off dynamics in the feedback path, stability conditions are obtained. Trade studies are conducted with modal frequency, modal participation, modal damping, loop bandwidth, and sensor bandwidth treated as free parameters. Results indicate that appendage modes are most likely to produce instability if they are near the sensor rolloff, whereas in-the-loop modes are most dangerous near the loop bandwidth. The main goal of this paper is to provide a fundamental understanding of the control-structure interaction problem so that it may benefit the design of complex spacecraft and pointing system servo loops. In this framework, the JPL Pathfinder gimbal pointer is considered as an example.
Space vector control strategy fixed-frequency hysteresis loop APF%有源电力滤波器的定频滞环空间矢量控制策略研究
Institute of Scientific and Technical Information of China (English)
薛博文
2015-01-01
本文通过基于空间电压矢量（SVPWM）滞环电流控制策略，搭建了以DSP2407控制芯片为控制核心、定频滞环SVPWM为控制策略的有源电力滤波器控制系统，针对两种负载做了无功补偿实验，同时分析了在该控制策略下有源电力滤波器的补偿效果。实验结果验证了定频滞环SVPWM控制策略理论的正确性及可行性。%In this paper, based on space voltage vector (SVPWM) hysteresis current control strategy, built to DSP2407 control chip to control the core, fixed-frequency hysteresis SVPWM control strategy for active power filter control system, made for two kinds of load reactive power compensation experiments, and analyzes the compensation effect of the control strategy under APF. The experimental results demonstrate the fixed-frequency hysteresis SVPWM control strategy correctness and feasibility of the theory.
LoopIng: a template-based tool for predicting the structure of protein loops.
Messih, Mario Abdel
2015-08-06
Predicting the structure of protein loops is very challenging, mainly because they are not necessarily subject to strong evolutionary pressure. This implies that, unlike the rest of the protein, standard homology modeling techniques are not very effective in modeling their structure. However, loops are often involved in protein function, hence inferring their structure is important for predicting protein structure as well as function.We describe a method, LoopIng, based on the Random Forest automated learning technique, which, given a target loop, selects a structural template for it from a database of loop candidates. Compared to the most recently available methods, LoopIng is able to achieve similar accuracy for short loops (4-10 residues) and significant enhancements for long loops (11-20 residues). The quality of the predictions is robust to errors that unavoidably affect the stem regions when these are modeled. The method returns a confidence score for the predicted template loops and has the advantage of being very fast (on average: 1 min/loop).www.biocomputing.it/loopinganna.tramontano@uniroma1.itSupplementary data are available at Bioinformatics online.
CHOI, J.; Yi, M. J.; Sasaki, Y.; Son, J.; Nam, M. J.
2015-12-01
Most of mineral mines in Korea are located in rugged mountain area embedding small-scale anomalies. Loop-loop EM survey system can be a better choice for exploring those mines because no ground contact is required and portable loops are freely positioned. Survey design is very important for detecting small amount of mineral deposits efficiently and spatial limits of survey lines should be considered. Along a same survey line, surveys with different separations between a transmitter and a receiver are applicable. EM responses are calculated in a layered-earth model embedding magnetic anomalies and analyses considering electric conductivity and magnetic permeability are made for the loop-loop EM survey data. Combining EM dataset with multi-frequency and multi-separation slightly enhanced a reconstructed image. Loop-loop EM survey using PROMOIS system was conducted on a small magnetite mine. Inversion with and without considering magnetic permeability was conducted for EM data with multi-frequency and multi-separation between a transmitter and a receiver.
Institute of Scientific and Technical Information of China (English)
孙杨; 李桀; 井晓荣; 王超; 梁秦川; 李焕发; 张华; 高国栋
2011-01-01
目的 探讨低、高频闭环电刺激对氯化铁癫痫模型大鼠的治疗效果.方法 给予SD大鼠头颅额、顶、枕部铺设硬膜外电极6枚,用立体定向方法在大鼠感觉运动皮质区注入氯化铁溶液,建立癫痫模型,分别给予低频刺激(1Hz)和高频刺激(100Hz),同时给予8小时脑电监测.分析大鼠8小时内发作总次数和发作总时间.结果 低频和高频电刺激均能抑制大鼠的癫痫发作,而高频与低频刺激在治疗效果上无明显统计学差异.结论 低频刺激为较佳的刺激方式.%Objective Comparison between therapeutic effects of low- and high- frequency electric closed-loop stimulation on the ferric chloride-induced seizures in rats. Methods SD rats respectively received implantation of 6 epidural electrodes placed in frontal parietal and occipital regions of cranium. To establish an acute epilepsy model, FeC13 was injected into sensori motor cortxe of rats with stereotactic technique. Were given low- frequency stimulation (1 Hz) and high-frequency stimulation (100Hz),while giving eight hours EEG monitoring. Analysis of rats duration time and number of seizures. Results The duration time and number of seizures in 1 - Hzor 100-Hz groups was apparently shorter than that in the control group. The high frequency and low frequency stimulation in the treatment effect was no significant difference. Conclusion Comparison with high-frequency stimulation, low-frequency stimulation is better for Clinical application.
Adjust or Synchronize LM2586/88 Switching Frequency
Institute of Scientific and Technical Information of China (English)
2003-01-01
INTRODUCTIONSwitching frequency is a very important parameter in switchingpower converters. As the switching frequency increases, the physicalsize of magnetic elements and other components in the circuit reducesignificantly. Switching frequency also plays a great role incontrol loop gain and compensation design. Switching frequency determinesthe maximum allowable bandwidth of the control loop.Switching frequency is also important parameter for EMI and noiseissues. The EMI spectrum is a direct function of the switching fre-
A cryo-amplifier working in a double loop-flux locked loop scheme for SQUID readout of TES detectors
Torrioli, Guido; Bastia, Paolo; Piro, Luigi; Macculi, Claudio; Colasanti, Luca
2010-07-01
In this paper we report on a novel SQUID readout scheme, called Double Loop-Flux Locked loop (DL-FLL), that we are investigating in the frame of ASI and ESA technological development contracts. This scheme is based on the realization of a cryogenic amplifier which is used in order to readout TES detectors in the Frequency Division Multiplexing technique, where high loop-gain is required up to few MHz. Loop-gain in feedback systems is, usually, limited by the propagation delay of the signals traveling in the loop because of the distance between the feedback loop elements. This problem is particularly evident in the case of SQUID systems, where the elements of the feedback loop are placed both at cryogenic and room temperature. To solve this issue we propose a low power dissipation cryo-amplifier capable to work at cryogenic temperatures so that it can be placed close to the SQUID realizing a local cryogenic loop. The adoption of the DL-FLL scheme allows to simplify considerably the cryo-amplifier which, being AC-coupled, don't require the features of a precision DC-coupled amplifier and can be made with a limited number of electronic components and with a consequent reduction of power dissipation.
Trusiak, Maciej; Patorski, Krzysztof; Sluzewski, Lukasz; Sunderland, Zofia
2016-04-01
In this contribution we evaluate single and two-shot techniques, namely the Hilbert spiral transform (HST) and the Gram-Schmidt orthonormalization (GSO) in terms of phase demodulation accuracy in the complex fringe patterns analysis (i.e., with strong background/contrast variations, severe noise, considerable local gradients of fringe shape/orientation). Both methods are aided by the novel Hilbert-Huang transform (HHT) processing to adaptively reduce demodulation errors. The HST utilizes a spiral phase function and a spatial fringe orientation map to demodulate phase of complex fringes. It is especially susceptible to uneven bias term and noise. The HHT method realizes bias/noise suppression adaptively with outstanding accuracy. The GSO is a fast two-shot fringe-shape-robust phase demodulation scheme. It treats two arbitrarily phase shifted interferograms as vectors and conducts orthogonal projection of one vector onto another. The GSO is susceptible to background, contrast and noise fluctuations, however. The HHT method is perfectly suitable to perform efficient pre-filtering. Both methods (HHT-HST and HHT-GSO) are proven versatile and robust to fringe pattern defects using simulation and experiment.
Institute of Scientific and Technical Information of China (English)
刘志刚; 李国锋; 王宁会
2012-01-01
为了满足交联聚乙烯（XLPE）电缆对检测电源的要求,设计了一种采用两个高频高压变压器作为升压变压器的超低频高压电源。详细阐述了系统的硬件设计及软件控制策略,优化了变压器的结构及绝缘,大大缩小了变压器的体积及质量,减小了变压器的分布参数。并根据电路拓扑的特点,首次采用先进的三闭环控制技术,动态地对高频部分及低频部分的输出进行了监控与调整,减小了高频高压变压器分布参数对电源性能的影响。同时对采样数据采取了分段化的处理方法,大大减小了程序的计算量,使它能够应用于单片机控制。采用所设计的35kV/0.1Hz电源对电气特性等效于XLPE电缆的高压电容（1.5μF）进行了实验,其总谐波畸变率（THD）为2.76%,完全满足IEEE 400.2标准对总谐波畸变率〈5%的要求。实验结果验证了理论的可行性与正确性。%A novel topology and the control strategy of the very-low-frequency（VLF） high voltage generator are introduced to meet the requirements of XLPE cable test.Design parameters of the system hardware and the control strategy of the system software are presented.The structure and the insulation of the transformer are optimized.As a result,the volume and the weight are decreased obviously.According to the topology of the circuit,the cutting edge of three-closed-loop control technology is first applied in VLF high voltage power supply.The output voltage and the secondary voltage are timely monitored and regulated,so that the influence of distributed parameter is reduced effectively.Simultaneously,the principle of segmental data processing is applied in data processing.Thereby,the calculation complexity is decreased significantly.The 35 kV/0.1 Hz power supply is used to test a 1.5 μF capacitor.Total harmonic distortion is 2.76% which can meet the requirements of IEEE 400.6 standard.The experimental results verify the accuracy and
Improving Loop Dependence Analysis
DEFF Research Database (Denmark)
Jensen, Nicklas Bo; Karlsson, Sven
2017-01-01
Programmers can no longer depend on new processors to have significantly improved single-thread performance. Instead, gains have to come from other sources such as the compiler and its optimization passes. Advanced passes make use of information on the dependencies related to loops. We improve...... the quality of that information by reusing the information given by the programmer for parallelization. We have implemented a prototype based on GCC into which we also add a new optimization pass. Our approach improves the amount of correctly classified dependencies resulting in 46% average improvement...
Dassau, E; Atlas, E; Phillip, M
2011-02-01
Closed-loop algorithms can be found in every aspect of everyday modern life. Automation and control are used constantly to provide safety and to improve quality of life. Closed-loop systems and algorithms can be found in home appliances, automobiles, aviation and more. Can one imagine nowadays driving a car without ABS, cruise control or even anti-sliding control? Similar principles of automation and control can be used in the management of diabetes mellitus (DM). The idea of an algorithmic/technological way to control glycaemia is not new and has been researched for more than four decades. However, recent improvements in both glucose-sensing technology and insulin delivery together with advanced control and systems engineering made this dream of an artificial pancreas possible. The artificial pancreas may be the next big step in the treatment of DM since the use of insulin analogues. An artificial pancreas can be described as internal or external devices that use continuous glucose measurements to automatically manage exogenous insulin delivery with or without other hormones in an attempt to restore glucose regulation in individuals with DM using a control algorithm. This device as described can be internal or external; can use different types of control algorithms with bi-hormonal or uni-hormonal design; and can utilise different ways to administer them. The different designs and implementations have transitioned recently from in silico simulations to clinical evaluation stage with practical applications in mind. This may mark the beginning of a new era in diabetes management with the introduction of semi-closed-loop systems that can prevent or minimise nocturnal hypoglycaemia, to hybrid systems that will manage blood glucose (BG) levels with minimal user intervention to finally fully automated systems that will take the user out of the loop. More and more clinical trials will be needed for the artificial pancreas to become a reality but initial encouraging
基于GNU Radio的单边带解调方式的研究%Research on SSB Demodulation Methods Based on GNU Radio
Institute of Scientific and Technical Information of China (English)
张晓; 孙运强; 姚爱琴
2016-01-01
通过GNU Radio软件平台和RTL⁃SDR硬件设备搭建软件无线电开发平台，对短波单边带解调算法进行仿真研究。介绍了GNU Radio平台及 RTL⁃SDR 的功能及结构，基于软件无线电的思想，利用其数字正交解调算法，在GRC平台上对短波频段单边带解调方法进行了仿真测试研究。测试结果表明了此解调算法的可行性，并且与模拟解调相比其实时性好，且平台搭建简单方便。%The software defined radio ( SDR ) platform is built based on GNU Radio software platform and RTL⁃SDR hardware equipment to perform simulation research on shortwave single sideband demodulation algorithm.This paper introduces the functions and structure of GNU Radio platform and RTL⁃SDR.Based on SDR idea,the digital orthogonal demodulation algorithm is used to perform simulation test research on shortwave single sideband demodulation method at GRC platform. The simulation test results show that this demodulation algorithm has feasibility,high real⁃time performance compared with analog demodulation and simple platform construction convenient for simulation test research.
MECHANICAL DEMODULATION OF HYDRODYNAMIC STIMULI PERFORMED BY THE LATERAL-LINE ORGAN
van Netten, S.M.; KHANNA, SM
1993-01-01
Tonic displacements of the fish lateral line cupula were observed during stimulation of the organ with amplitude-modulated water motion. The modulation frequency was fixed at 2.4 Hz and the carrier frequency was varied from 25 to 500 Hz. The time wave-forms of the cupular displacement.at carrier fre
MECHANICAL DEMODULATION OF HYDRODYNAMIC STIMULI PERFORMED BY THE LATERAL-LINE ORGAN
van Netten, S.M.; KHANNA, SM
1993-01-01
Tonic displacements of the fish lateral line cupula were observed during stimulation of the organ with amplitude-modulated water motion. The modulation frequency was fixed at 2.4 Hz and the carrier frequency was varied from 25 to 500 Hz. The time wave-forms of the cupular displacement.at carrier
Loop expansion and the bosonic representation of loop quantum gravity
Bianchi, E.; Guglielmon, J.; Hackl, L.; Yokomizo, N.
2016-10-01
We introduce a new loop expansion that provides a resolution of the identity in the Hilbert space of loop quantum gravity on a fixed graph. We work in the bosonic representation obtained by the canonical quantization of the spinorial formalism. The resolution of the identity gives a tool for implementing the projection of states in the full bosonic representation onto the space of solutions to the Gauss and area matching constraints of loop quantum gravity. This procedure is particularly efficient in the semiclassical regime, leading to explicit expressions for the loop expansions of coherent, heat kernel and squeezed states.
Loop expansion and the bosonic representation of loop quantum gravity
Bianchi, Eugenio; Hackl, Lucas; Yokomizo, Nelson
2016-01-01
We introduce a new loop expansion that provides a resolution of the identity in the Hilbert space of loop quantum gravity on a fixed graph. We work in the bosonic representation obtained by the canonical quantization of the spinorial formalism. The resolution of the identity gives a tool for implementing the projection of states in the full bosonic representation onto the space of solutions to the Gauss and area matching constraints of loop quantum gravity. This procedure is particularly efficient in the semiclassical regime, leading to explicit expressions for the loop expansions of coherent, heat kernel and squeezed states.
Institute of Scientific and Technical Information of China (English)
张占锋; 樊艳芳; 王一波; 王环
2016-01-01
电网不对称故障时,光伏发电系统中的负序分量和谐波分量会影响并网逆变器中的锁相环及控制算法.文章提出一种具有自适应滤波的双二阶广义积分锁频环技术,用于电网电压和并网电流正负序分量的提取以及电网电压同步信号的检测,并将该技术引入到正负序双电流环控制策略,通过优化不平衡控制策略中锁相环的方法,提升光伏并网逆变器整个控制系统应对电网不对称故障的能力.通过Matlab/Simulink软件平台搭建基于DSOGI-FLL锁频环的光伏并网发电系统模型并进行了仿真研究,结果表明,文章控制策略在电网不对称故障时有助于消除有功功率的2倍频波动以及抑制并网电流中的谐波分量.%Negative sequence and harmonic components of PV power generation system had an important influence on phase locked-loop and control algorithm of grid-connected inverter under grid asymmetrical fault.Based on the above problems,in order to extract positive-negative sequence components of grid voltage and grid-connected current and detect the synchronization signal of grid voltage,this paper proposed a double second-order generalized integrator frequency-locked loop (DSOGI-FLL) technology with adaptive filtering.And the technology was introduced into the positive-negative sequence dual current control strategy.The method of optimizing phase-locked loop in unbalanced control strategy improved the whole control system's ability of PV grid-connected inverter to cope with gird asymmetric fault.The grid-connected PV power generation system based on DSOGI-FLL was simulated by using Matlab/Simulink software.The results showed thatThis method contributes to eliminate the 2 harmonic wave of active power and restrain the harmonic component of grid-connected current under grid asymmetrical fault.
High-resolution ADC operation up to 19.6 GHz clock frequency
Mukhanov, O. A.; Semenov, V. K.; Vernik, I. V.; Kadin, A. M.; Filippov, T. V.; Gupta, D.; Brock, D. K.; Rochwarger, I.; Polyakov, Y. A.
2001-12-01
We have designed, fabricated and tested the second-generation (2G) design of a high-resolution, dynamically programmable analog-to-digital converter (ADC) for radar and communications applications. The ADC chip uses the phase modulation-demodulation architecture and on-chip digital filtering. The 2G ADC design has been substantially enhanced. Both ADC front-end modulator and demodulator, as well as decimation digital filter, have been redesigned for operation at 20 GHz. Test results of this 6000 Josephson junction 2G ADC chip at clock frequencies up to 19.6 GHz are described. These test results were compared to the results of ADC functional simulation using MATLAB.
High temperature storage loop :
Energy Technology Data Exchange (ETDEWEB)
Gill, David Dennis; Kolb, William J.
2013-07-01
A three year plan for thermal energy storage (TES) research was created at Sandia National Laboratories in the spring of 2012. This plan included a strategic goal of providing test capability for Sandia and for the nation in which to evaluate high temperature storage (>650ÀC) technology. The plan was to scope, design, and build a flow loop that would be compatible with a multitude of high temperature heat transfer/storage fluids. The High Temperature Storage Loop (HTSL) would be reconfigurable so that it was useful for not only storage testing, but also for high temperature receiver testing and high efficiency power cycle testing as well. In that way, HTSL was part of a much larger strategy for Sandia to provide a research and testing platform that would be integral for the evaluation of individual technologies funded under the SunShot program. DOEs SunShot program seeks to reduce the price of solar technologies to 6/kWhr to be cost competitive with carbon-based fuels. The HTSL project sought to provide evaluation capability for these SunShot supported technologies. This report includes the scoping, design, and budgetary costing aspects of this effort
High temperature storage loop :
Energy Technology Data Exchange (ETDEWEB)
Gill, David Dennis; Kolb, William J.
2013-07-01
A three year plan for thermal energy storage (TES) research was created at Sandia National Laboratories in the spring of 2012. This plan included a strategic goal of providing test capability for Sandia and for the nation in which to evaluate high temperature storage (>650ÀC) technology. The plan was to scope, design, and build a flow loop that would be compatible with a multitude of high temperature heat transfer/storage fluids. The High Temperature Storage Loop (HTSL) would be reconfigurable so that it was useful for not only storage testing, but also for high temperature receiver testing and high efficiency power cycle testing as well. In that way, HTSL was part of a much larger strategy for Sandia to provide a research and testing platform that would be integral for the evaluation of individual technologies funded under the SunShot program. DOEs SunShot program seeks to reduce the price of solar technologies to 6/kWhr to be cost competitive with carbon-based fuels. The HTSL project sought to provide evaluation capability for these SunShot supported technologies. This report includes the scoping, design, and budgetary costing aspects of this effort
Optimized Carrier Tracking Loop Design for Real-Time High-Dynamics GNSS Receivers
Directory of Open Access Journals (Sweden)
Pedro A. Roncagliolo
2012-01-01
Full Text Available Carrier phase estimation in real-time Global Navigation Satellite System (GNSS receivers is usually performed by tracking loops due to their very low computational complexity. We show that a careful design of these loops allows them to operate properly in high-dynamics environments, that is, accelerations up to 40 g or more. Their phase and frequency discriminators and loop filter are derived considering the digital nature of the loop inputs. Based on these ideas, we propose a new loop structure named Unambiguous Frequency-Aided Phase-Locked Loop (UFA-PLL. In terms of tracking capacity and noise resistance UFA-PLL has the same advantages of frequently used coupled-loop schemes, but it is simpler to design and to implement. Moreover, it can keep phase lock in situations where other loops cannot. The loop design is completed selecting the correlation time and loop bandwidth that minimize the pull-out probability, without relying on typical rules of thumb. Optimal and efficient ways to smooth the phase estimates are also presented. Hence, high-quality phase measurements—usually exploited in offline and quasistatic applications—become practical for real-time and high-dynamics receivers. Experiments with fixed-point implementations of the proposed loops and actual radio signals are also shown.
Energy Technology Data Exchange (ETDEWEB)
Chu, T.L.; Musicki, Z.; Kohut, P.; Yang, J.; Bozoki, G.; Hsu, C.J.; Diamond, D.J. [Brookhaven National Lab., Upton, NY (United States); Bley, D.; Johnson, D. [PLG Inc., Newport Beach, CA (United States); Holmes, B. [AEA Technology, Dorset (United Kingdom)] [and others
1994-06-01
Traditionally, probabilistic risk assessments (PRA) of severe accidents in nuclear power plants have considered initiating events potentially occurring only during full power operation. Some previous screening analyses that were performed for other modes of operation suggested that risks during those modes were small relative to full power operation. However, more recent studies and operational experience have implied that accidents during low power and shutdown could be significant contributors to risk. During 1989, the Nuclear Regulatory Commission (NRC) initiated an extensive program to carefully examine the potential risks during low power and shutdown operations. The program includes two parallel projects being performed by Brookhaven National Lab. (BNL) and Sandia National Labs. (SNL). Two plants, Surry (pressurized water reactor) and Grand Gulf (boiling water reactor), were selected as the plants to be studied. The objectives of the program are to assess the risks of severe accidents initiated during plant operational states other than full power operation and to compare the estimated core damage frequencies, important accident sequences and other qualitative and quantitative results with those accidents initiated during full power operation as assessed in NUREG-1150. The objective of this volume of the report is to document the approach utilized in the level-1 internal events PRA for the Surry plant, and discuss the results obtained. A phased approach was used in the level-1 program. In phase 1, which was completed in Fall 1991, a coarse screening analysis examining accidents initiated by internal events (including internal fire and flood) was performed for all plant operational states (POSs). The objective of the phase 1 study was to identify potential vulnerable plant configurations, to characterize (on a high, medium, or low basis) the potential core damage accident scenarios, and to provide a foundation for a detailed phase 2 analysis.
Institute of Scientific and Technical Information of China (English)
杨小云
2014-01-01
目的：探讨宫颈上皮内瘤样病变高频电波刀环形电切术治疗的围术期护理效果。方法选取2011年6月~2013年6月需于本院进行高频电波刀环形电切术治疗的宫颈上皮内瘤样病变患者110例，按数字随机法将患者分为观察组和对照组，每组55例。患者均进行常规高频电波刀环形电切术治疗。对照组采取常规护理，观察组采取围术期整体护理。比较两组的治疗效果、平均住院时间、并发症发生情况以及患者满意度。结果观察组治愈率为96.36%，高于对照组的83.64%，差异有统计学意义(P<0.05)。与对照组比较，观察组平均住院时间缩短，总并发症发生率降低，患者满意度提高，差异有统计学意义(P<0.05)。结论围术期整体护理有利于患者的治疗，可缩短患者的住院时间，减少各类并发症的发生并提高患者的满意度，值得临床推广应用。%Objective To investigate the effect of applying perioperative nursing after the high frequency electrosurgical knife loop electrosurgical excision of cervical intraepithelial neoplasia. Methods 110 patients with cervical intraepithe-lial neoplasia received high frequency electrosurgical knife loop electrosurgical excision in our hospital from June 2011 to June 2013 were selected and divided into the observation group and the control group according to the random number method,with 55 patients in each group.All the patients were received conventional high frequency electrosurgi-cal knife loop electrosurgical excision.The control group were received conventional nursing and the observation group were received perioperative holistic nursing.The treatment effects,average hospital stay,complications and patient satis-faction of the two groups were compared. Results The cure rate of the observation group was 96.36%,which was higher than 83.64% of the control group,with significant difference (P<0.05).Compared with the control group
Condition Monitoring of Control Loops
Horch, Alexander
2000-01-01
The main concern of this work is the development of methodsfor automatic condition monitoring of control loops withapplication to the process industry. By condition monitoringboth detection and diagnosis of malfunctioning control loops isunderstood, using normal operating data and a minimum amount ofprocess knowledge. The use of indices for quantifying loop performance is dealtwith in the first part of the thesis. The starting point is anindex proposed by Harris (1989). This index has been mo...
Loop Heat Pipe Startup Behaviors
Ku, Jentung
2016-01-01
A loop heat pipe must start successfully before it can commence its service. The startup transient represents one of the most complex phenomena in the loop heat pipe operation. This paper discusses various aspects of loop heat pipe startup behaviors. Topics include the four startup scenarios, the initial fluid distribution between the evaporator and reservoir that determines the startup scenario, factors that affect the fluid distribution between the evaporator and reservoir, difficulties encountered during the low power startup, and methods to enhance the startup success. Also addressed are the pressure spike and pressure surge during the startup transient, and repeated cycles of loop startup and shutdown under certain conditions.
Geometry and Dynamics of Vortex Loops at Superfluid Phase Transitions
Williams, Gary A.
2004-03-01
The geometrical properties of thermally-excited vortex loops near a superfluid phase transition can be deduced from the dynamics of the transition. The frictional force on a loop is proportional to the total length of the vortex core, and hence depends on the fractal Hausdorff dimension DH of the random-walking core. By comparing the results for the loop dynamics with the dynamic-scaling predictions of Halperin and Hohenberg for the relaxation time, we find DH = (D+2)/2 = 2.5 in D = 3 dimensions, if the dynamic exponent is z = D/2. Computing the frequency-dependence of the superfluid density and comparing with the dynamic scaling of Fisher, Fisher, and Huse gives just the same value. Since Shenoy and co-workers have found precisely the same DH from a Flory-scaling analysis of the loop random walk, our results show that Shenoy's theory is exact if dynamic scaling is exact.
Energy Technology Data Exchange (ETDEWEB)
Pei, L.; Klebaner, A.; Theilacker, J.; Soyars, W.; Martinez, A.; Bossert, R.; DeGraff, B.; Darve, C.; /Fermilab
2011-06-01
The Horizontal Test Stand (HTS) SRF Cavity and Cryomodule 1 (CM1) of eight 9-cell, 1.3GHz SRF cavities are operating at Fermilab. For the cryogenic control system, how to hold liquid level constant in the cryostat by regulation of its Joule-Thompson JT-valve is very important after cryostat cool down to 2.0 K. The 72-cell cryostat liquid level response generally takes a long time delay after regulating its JT-valve; therefore, typical PID control loop should result in some cryostat parameter oscillations. This paper presents a type of PID parameter self-optimal and Time-Delay control method used to reduce cryogenic system parameters oscillation.
Pei, L; Theilacker, J; Soyars, W; Martinez, A; Bossert, R; DeGraff, B; Darve, C
2012-01-01
The Horizontal Test Stand (HTS) SRF Cavity and Cryomodule 1 (CM1) of eight 9-cell, 1.3GHz SRF cavities are operating at Fermilab. For the cryogenic control system, how to hold liquid level constant in the cryostat by regulation of its Joule-Thompson JT-valve is very important after cryostat cool down to 2.0 K. The 72-cell cryostat liquid level response generally takes a long time delay after regulating its JT-valve; therefore, typical PID control loop should result in some cryostat parameter oscillations. This paper presents a type of PID parameter self-optimal and Time-Delay control method used to reduce cryogenic system parameters' oscillation.
Energy Technology Data Exchange (ETDEWEB)
Chesi, Stefano [Department of Physics, McGill University, Montreal, Quebec H3A 2T8 (Canada); CEMS, RIKEN, Wako, Saitama 351-0198 (Japan); Jaffe, Arthur [Harvard University, Cambridge, Massachusetts 02138 (United States); Department of Physics, University of Basel, Basel (Switzerland); Institute for Theoretical Physics, ETH Zürich, Zürich (Switzerland); Loss, Daniel [CEMS, RIKEN, Wako, Saitama 351-0198 (Japan); Department of Physics, University of Basel, Basel (Switzerland); Pedrocchi, Fabio L. [Department of Physics, University of Basel, Basel (Switzerland)
2013-11-15
We investigate the role that vortex loops play in characterizing eigenstates of interacting Majoranas. We give some general results and then focus on ladder Hamiltonian examples as a test of further ideas. Two methods yield exact results: (i) A mapping of certain spin Hamiltonians to quartic interactions of Majoranas shows that the spectra of these two examples coincide. (ii) In cases with reflection-symmetric Hamiltonians, we use reflection positivity for Majoranas to characterize vortices in the ground states. Two additional methods suggest wider applicability of these results: (iii) Numerical evidence suggests similar behavior for certain systems without reflection symmetry. (iv) A perturbative analysis also suggests similar behavior without the assumption of reflection symmetry.
Directory of Open Access Journals (Sweden)
Rovelli Carlo
2008-07-01
Full Text Available The problem of describing the quantum behavior of gravity, and thus understanding quantum spacetime, is still open. Loop quantum gravity is a well-developed approach to this problem. It is a mathematically well-defined background-independent quantization of general relativity, with its conventional matter couplings. Today research in loop quantum gravity forms a vast area, ranging from mathematical foundations to physical applications. Among the most significant results obtained so far are: (i The computation of the spectra of geometrical quantities such as area and volume, which yield tentative quantitative predictions for Planck-scale physics. (ii A physical picture of the microstructure of quantum spacetime, characterized by Planck-scale discreteness. Discreteness emerges as a standard quantum effect from the discrete spectra, and provides a mathematical realization of Wheeler’s “spacetime foam” intuition. (iii Control of spacetime singularities, such as those in the interior of black holes and the cosmological one. This, in particular, has opened up the possibility of a theoretical investigation into the very early universe and the spacetime regions beyond the Big Bang. (iv A derivation of the Bekenstein–Hawking black-hole entropy. (v Low-energy calculations, yielding n-point functions well defined in a background-independent context. The theory is at the roots of, or strictly related to, a number of formalisms that have been developed for describing background-independent quantum field theory, such as spin foams, group field theory, causal spin networks, and others. I give here a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.
Single frequency semiconductor lasers
Fang, Zujie; Chen, Gaoting; Qu, Ronghui
2017-01-01
This book systematically introduces the single frequency semiconductor laser, which is widely used in many vital advanced technologies, such as the laser cooling of atoms and atomic clock, high-precision measurements and spectroscopy, coherent optical communications, and advanced optical sensors. It presents both the fundamentals and characteristics of semiconductor lasers, including basic F-P structure and monolithic integrated structures; interprets laser noises and their measurements; and explains mechanisms and technologies relating to the main aspects of single frequency lasers, including external cavity lasers, frequency stabilization technologies, frequency sweeping, optical phase locked loops, and so on. It paints a clear, physical picture of related technologies and reviews new developments in the field as well. It will be a useful reference to graduate students, researchers, and engineers in the field.
Chen, Xiaowang; Feng, Zhipeng
2016-12-01
Planetary gearboxes are widely used in many sorts of machinery, for its large transmission ratio and high load bearing capacity in a compact structure. Their fault diagnosis relies on effective identification of fault characteristic frequencies. However, in addition to the vibration complexity caused by intricate mechanical kinematics, volatile external conditions result in time-varying running speed and/or load, and therefore nonstationary vibration signals. This usually leads to time-varying complex fault characteristics, and adds difficulty to planetary gearbox fault diagnosis. Time-frequency analysis is an effective approach to extracting the frequency components and their time variation of nonstationary signals. Nevertheless, the commonly used time-frequency analysis methods suffer from poor time-frequency resolution as well as outer and inner interferences, which hinder accurate identification of time-varying fault characteristic frequencies. Although time-frequency reassignment improves the time-frequency readability, it is essentially subject to the constraints of mono-component and symmetric time-frequency distribution about true instantaneous frequency. Hence, it is still susceptible to erroneous energy reallocation or even generates pseudo interferences, particularly for multi-component signals of highly nonlinear instantaneous frequency. In this paper, to overcome the limitations of time-frequency reassignment, we propose an improvement with fine time-frequency resolution and free from interferences for highly nonstationary multi-component signals, by exploiting the merits of iterative generalized demodulation. The signal is firstly decomposed into mono-components of constant frequency by iterative generalized demodulation. Time-frequency reassignment is then applied to each generalized demodulated mono-component, obtaining a fine time-frequency distribution. Finally, the time-frequency distribution of each signal component is restored and superposed to
A Novel Controller for Model with Combined LFC and AVR Loops of Single Area Power System
Gupta, Monika; Srivastava, Smriti; Gupta, J. R. P.
2016-03-01
In this study, a novel controller is designed to study low frequency oscillations for load frequency control (LFC) and voltage control of a single area power system. For more accuracy in dynamic and steady state responses, mutual effects between LFC and automatic voltage regulation (AVR) loops are investigated in a combined simulink model of LFC and AVR loops. The effectiveness of the proposed controller is first simulated on model with LFC loop alone. The proposed controller is a hybrid of neural network and fast traversal filters. The proposed hybrid controller requires less number of samples for training of weights, thus making the system fast. To study the coupling effects of AVR and LFC loops, dynamic performance of a complete system model for low frequency oscillation studies comprising of mechanical and electrical loops is done with the proposed controller.
Phenomenology of loop quantum cosmology
Sakellariadou, Mairi
2010-01-01
After introducing the basic ingredients of Loop Quantum Cosmology, I will briefly discuss some of its phenomenological aspects. Those can give some useful insight about the full Loop Quantum Gravity theory and provide an answer to some long-standing questions in early universe cosmology.
RCD+: Fast loop modeling server.
López-Blanco, José Ramón; Canosa-Valls, Alejandro Jesús; Li, Yaohang; Chacón, Pablo
2016-07-08
Modeling loops is a critical and challenging step in protein modeling and prediction. We have developed a quick online service (http://rcd.chaconlab.org) for ab initio loop modeling combining a coarse-grained conformational search with a full-atom refinement. Our original Random Coordinate Descent (RCD) loop closure algorithm has been greatly improved to enrich the sampling distribution towards near-native conformations. These improvements include a new workflow optimization, MPI-parallelization and fast backbone angle sampling based on neighbor-dependent Ramachandran probability distributions. The server starts by efficiently searching the vast conformational space from only the loop sequence information and the environment atomic coordinates. The generated closed loop models are subsequently ranked using a fast distance-orientation dependent energy filter. Top ranked loops are refined with the Rosetta energy function to obtain accurate all-atom predictions that can be interactively inspected in an user-friendly web interface. Using standard benchmarks, the average root mean squared deviation (RMSD) is 0.8 and 1.4 Å for 8 and 12 residues loops, respectively, in the challenging modeling scenario in where the side chains of the loop environment are fully remodeled. These results are not only very competitive compared to those obtained with public state of the art methods, but also they are obtained ∼10-fold faster. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.
Laflame, D. T.
1980-01-01
Delay-locked loop tracks pseudonoise codes without introducing dc timing errors, because it is not sensitive to gain imbalance between signal processing arms. "Early" and "late" reference codes pass in combined form through both arms, and each arm acts on both codes. Circuit accomodates 1 dB weaker input signals with tracking ability equal to that of tau-dither loops.
Loop groups and noncommutative geometry
Carpi, Sebastiano
2015-01-01
We describe the representation theory of loop groups in terms of K-theory and noncommutative geometry. This is done by constructing suitable spectral triples associated with the level l projective unitary positive-energy representations of any given loop group LG. The construction is based on certain supersymmetric conformal field theory models associated with LG.
Brane Couplings from Bulk Loops
Georgi, Howard; Grant, Aaron K.; Hailu, Girma
2000-01-01
We compute loop corrections to the effective action of a field theory on a five-dimensional $S_1/Z_2$ orbifold. We find that the quantum loop effects of interactions in the bulk produce infinite contributions that require renormalization by four-dimensional couplings on the orbifold fixed planes. Thus bulk couplings give rise to renormalization group running of brane couplings.
Higher dimensional loop quantum cosmology
Zhang, Xiangdong
2016-07-01
Loop quantum cosmology (LQC) is the symmetric sector of loop quantum gravity. In this paper, we generalize the structure of loop quantum cosmology to the theories with arbitrary spacetime dimensions. The isotropic and homogeneous cosmological model in n+1 dimensions is quantized by the loop quantization method. Interestingly, we find that the underlying quantum theories are divided into two qualitatively different sectors according to spacetime dimensions. The effective Hamiltonian and modified dynamical equations of n+1 dimensional LQC are obtained. Moreover, our results indicate that the classical big bang singularity is resolved in arbitrary spacetime dimensions by a quantum bounce. We also briefly discuss the similarities and differences between the n+1 dimensional model and the 3+1 dimensional one. Our model serves as a first example of higher dimensional loop quantum cosmology and offers the possibility to investigate quantum gravity effects in higher dimensional cosmology.
Design and Performance Evaluation of a Dual Antenna Joint Carrier Tracking Loop
Directory of Open Access Journals (Sweden)
Wenfei Guo
2015-10-01
Full Text Available In order to track the carrier phases of Global Navigation Satellite Systems (GNSS signals in signal degraded environments, a dual antenna joint carrier tracking loop is proposed and evaluated. This proposed tracking loop processes inputs from two antennas, namely the master antenna and the slave antenna. The master antenna captures signals in open-sky environments, while the slave antenna capture signals in degraded environments. In this architecture, a Phase Lock Loop (PLL is adopted as a master loop to track the carrier phase of the open-sky signals. The Doppler frequency estimated by this master loop is utilized to assist weak carrier tracking in the slave loop. As both antennas experience similar signal dynamics due to satellite motion and clock frequency variations, a much narrower loop bandwidth and possibly a longer coherent integration can be adopted to track the weak signals in slave channels, by utilizing the Doppler aid from master channels. PLL tracking performance is affected by the satellite/user dynamics, clock instability, and thermal noise. In this paper, their impacts on the proposed phase tracking loop are analyzed and verified by both simulation and field data. Theoretical analysis and experimental results show that the proposed loop structure can track degraded signals (i.e., 18 dB-Hz with a very narrow loop bandwidth (i.e., 0.5 Hz and a TCXO clock.
Design and Performance Evaluation of a Dual Antenna Joint Carrier Tracking Loop.
Guo, Wenfei; Lin, Tao; Niu, Xiaoji; Shi, Chuang; Zhang, Hongping
2015-10-01
In order to track the carrier phases of Global Navigation Satellite Systems (GNSS) signals in signal degraded environments, a dual antenna joint carrier tracking loop is proposed and evaluated. This proposed tracking loop processes inputs from two antennas, namely the master antenna and the slave antenna. The master antenna captures signals in open-sky environments, while the slave antenna capture signals in degraded environments. In this architecture, a Phase Lock Loop (PLL) is adopted as a master loop to track the carrier phase of the open-sky signals. The Doppler frequency estimated by this master loop is utilized to assist weak carrier tracking in the slave loop. As both antennas experience similar signal dynamics due to satellite motion and clock frequency variations, a much narrower loop bandwidth and possibly a longer coherent integration can be adopted to track the weak signals in slave channels, by utilizing the Doppler aid from master channels. PLL tracking performance is affected by the satellite/user dynamics, clock instability, and thermal noise. In this paper, their impacts on the proposed phase tracking loop are analyzed and verified by both simulation and field data. Theoretical analysis and experimental results show that the proposed loop structure can track degraded signals (i.e., 18 dB-Hz) with a very narrow loop bandwidth (i.e., 0.5 Hz) and a TCXO clock.
Arteaga, Oriol; Baldrís, Marta; Antó, Joan; Canillas, Adolf; Pascual, Esther; Bertran, Enric
2014-04-01
In this paper we describe a new Mueller matrix (MM) microscope that generalizes and makes quantitative the polarized light microscopy technique. In this instrument all the elements of the MU are simultaneously determined from the analysis in the frequency domain of the time-dependent intensity of the light beam at every pixel of the camera. The variations in intensity are created by the two compensators continuously rotating at different angular frequencies. A typical measurement is completed in a little over one minute and it can be applied to any visible wavelength. Some examples are presented to demonstrate the capabilities of the instrument.
Energy Technology Data Exchange (ETDEWEB)
Ladd-Lively, Jennifer L [ORNL
2008-10-01
The objectives of the work discussed in this report were to: (1) develop a flow loop that would simulate the purified uranium-bearing aqueous stream exiting the solvent extraction process in a natural uranium conversion plant (NUCP); (2) develop a test plan that would simulate normal operation and disturbances that could be anticipated in an NUCP; (3) use the flow loop to test commercially available flowmeters for use as safeguards monitors; and (4) recommend a flowmeter for production-scale testing at an NUCP. There has been interest in safeguarding conversion plants because the intermediate products [uranium dioxide (UO{sub 2}), uranium tetrafluoride (UF{sub 4}), and uranium hexafluoride (UF{sub 6})] are all suitable uranium feedstocks for producing special nuclear materials. Furthermore, if safeguards are not applied virtually any nuclear weapons program can obtain these feedstocks without detection by the International Atomic Energy Agency (IAEA). Historically, IAEA had not implemented safeguards until the purified UF{sub 6} product was declared as feedstock for enrichment plants. H. A. Elayat et al. provide a basic definition of a safeguards system: 'The function of a safeguards system on a chemical conversion plant is in general terms to verify that no useful nuclear material is being diverted to use in a nuclear weapons program'. The IAEA now considers all highly purified uranium compounds as candidates for safeguarding. DOE is currently interested in 'developing instruments, tools, strategies, and methods that could be of use to the IAEA in the application of safeguards' for materials found in the front end of the nuclear fuel cycle-prior to the production of the uranium hexafluoride or oxides that have been the traditional starting point for IAEA safeguards. Several national laboratories, including Oak Ridge, Los Alamos, Lawrence Livermore, and Brookhaven, have been involved in developing tools or techniques for safeguarding conversion
Wang, Xu; Saberi, Ali; Grip, H°avard Fjær; Stoorvogel, Antonie Arij
2013-01-01
In this paper, we study the disturbance response of open-loop neutrally stable linear systems with saturating linear feedback controller. It is shown that the closed-loop states remain bounded if the disturbances con- sists of those signals that do not have large sustained frequency components
On equivalent radius of curvature for PWL geometrical modeling a loop antenna
CSIR Research Space (South Africa)
Lysko, AA
2012-11-01
Full Text Available A circular loop antenna is often numerically modeled using a regular polygon. This approach is simple and robust, yet it alters the circumference of the loop and may thus shift the resonance frequency in the numerical model. This letter introduces a...
OFDM Demodulation Design and Implementation Based on Software Ratio Module%基于软件无线电的OFDM解调模块的设计与实现
Institute of Scientific and Technical Information of China (English)
谭美玲; 周胜源
2012-01-01
In view of the IEEE802.11a standard for OFDM modulation and demodulation principle, together with the idea of Sofeware Defined Radio (SDR), some parts of OFDM demodulation module are presented by using the System Generator tool under the MATLAB/Simulink circumstance. It is just to make clear, with some emphasis about the design methods and simulation of the normalization, FFT demodulation and 16QAM demodulation modules. The simulation results show that these demodulation modules can demodulate the OFDM signal correctly.%针对IEEE802.11a标准中OFDM调制解调原理,结合软件无线电的思想,采用高效率的System Generator软件,对OFDM部分的解调模块进行设计与实现.设计中采用16QAM对数据符号进行调制,可以有效地降低系统误码率.仿真结果表明,所设计的OFDM解调模块具有较高的可靠性.
2014-03-27
research classifies successful jamming when the adaptive modulation changes order over subsequent frames indicating higher interference levels as seen by...timing synchronization for OFDM,” IEEE Transactions on Communications, vol. 45, no. 12, pp. 1613–1621, 1997. [24] F. Gini and G. Giannakis, “Frequency
Microcirculation monitoring with real time spatial frequency domain imaging
Chen, Xinlin; Cao, Zili; Lin, Weihao; Zhu, Danfeng; Zhu, Xiuwei; Zeng, Bixin; Xu, M.
2017-01-01
We present a spatial frequency domain imaging (SFDI) study of local hemodynamics in the forearm of healthy volunteers performing paced breathing. Real time Single Snapshot Multiple Frequency Demodulation - Spatial Frequency Domain Imaging (SSMD-SFDI) was used to map the optical properties of the subsurface of the forearm continuously. The oscillations of the concentrations of deoxy- and oxyhemoglobin at the subsurface of the forearm induced by paced breathing are found to be close to out-of-phase, attributed to the dominance of the blood flow modulation by paced breathing. The properties of local microcirculation including the blood transit times through capillaries and venules are extracted by fitting to Simplified Hemodynamics Model. Our preliminary results suggest that the real time SSMD-SFDI platform may serve as one effective imaging modality for microcirculation monitoring.
Chirikjian, Gregory S
2011-01-01
Proteins fold from a highly disordered state into a highly ordered one. Traditionally, the folding problem has been stated as one of predicting "the" tertiary structure from sequential information. However, new evidence suggests that the ensemble of unfolded forms may not be as disordered as once believed, and that the native form of many proteins may not be described by a single conformation, but rather an ensemble of its own. Quantifying the relative disorder in the folded and unfolded ensembles as an entropy difference may therefore shed light on the folding process. One issue that clouds discussions of "entropy" is that many different kinds of entropy can be defined: entropy associated with overall translational and rotational Brownian motion, configurational entropy, vibrational entropy, conformational entropy computed in internal or Cartesian coordinates (which can even be different from each other), conformational entropy computed on a lattice, each of the above with different solvation and solvent models, thermodynamic entropy measured experimentally, etc. The focus of this work is the conformational entropy of coil/loop regions in proteins. New mathematical modeling tools for the approximation of changes in conformational entropy during transition from unfolded to folded ensembles are introduced. In particular, models for computing lower and upper bounds on entropy for polymer models of polypeptide coils both with and without end constraints are presented. The methods reviewed here include kinematics (the mathematics of rigid-body motions), classical statistical mechanics, and information theory.
Freidel, Laurent; Pranzetti, Daniele
2016-01-01
In this work we study canonical gravity in finite regions for which we introduce a generalisation of the Gibbons-Hawking boundary term including the Immirzi parameter. We study the canonical formulation on a spacelike hypersuface with a boundary sphere and show how the presence of this term leads to an unprecedented type of degrees of freedom coming from the restoration of the gauge and diffeomorphism symmetry at the boundary. In the presence of a loop quantum gravity state, these boundary degrees of freedom localize along a set of punctures on the boundary sphere. We demonstrate that these degrees of freedom are effectively described by auxiliary strings with a 3-dimensional internal target space attached to each puncture. We show that the string currents represent the local frame field, that the string angular momenta represent the area flux and that the string stress tensor represents the two dimensional metric on the boundary of the region of interest. Finally, we show that the commutators of these broken...
Resonance for loop homology of spheres
Hingston, Nancy
2011-01-01
A Riemannian or Finsler metric on a compact manifold M gives rise to a length function on the free loop space \\Lambda M, whose critical points are the closed geodesics in the given metric. If X is a homology class on \\Lambda M, the minimax critical level cr(X) is a critical value. Let M be a sphere of dimension >2, and fix a metric g and a coefficient field G. We prove that the limit as deg(X) goes to infinity of cr(X)/deg(X) exists. We call this limit the "global mean frequency" of M. As a consequence we derive resonance statements for closed geodesics on spheres; in particular either all homology on \\Lambda M of sufficiently high degreee lies hanging on closed geodesics whose mean frequency (average index / length) equals the global mean frequency, or there is a sequence of infinitely many closed geodesics whose mean frequencies converge to the global mean frequency. The proof uses the Chas-Sullivan product and results of Goresky-Hingston [GH].
Gartland, Peter Lanier
2016-01-01
For the past 40 years, acoustic sensing has been a major avenue for the growth of interfero- metric fiber-optic sensors. Fiber-optic acoustic sensors have found uses in military, commer- cial, and medical applications. An interferometric fiber-optic acoustic sensor is presented utilizing the Michelson interferometer configuration with Faraday mirrors to eliminate po- larization fading. A 3 X 3 coupler is used as the beamsplitting component, and a symmetric demodulation algorith...
压缩采样接收机抗ADC非线性影响的分析%Analysis of Random Demodulator Receiver Against ADC Nonlinearity
Institute of Scientific and Technical Information of China (English)
王庆国; 王华力; 曾显华
2015-01-01
For the wideband digital receiver is susceptible to Analog to Digital Converter(ADC)nonlinear influence,Research random demodulation receiver performance under the influence of the ADC nonlinear. This paper was based on deep understanding the working principle of Random Demodulation,modeled reasonably to ADC nonlinearity,analyzed how ADC nonlinearity impact the random demodulation.Comparing to traditional digital receiver,Random demodulation had a better robustness to ADC nonlinearity because of the reconstruction algorithm.Simulation results verified the above theoretical analysis.%针对宽带数字接收机易受模拟数字转换器（ ADC ）非线性的影响，研究压缩采样接收机在模拟数字转换器非线性影响下的性能。在深入剖析随机解调原理的基础上，通过对模拟数字转换器非线性的合理建模，分析了模拟数字转换器非线性因素对压缩采样接收机性能的影响。对比于传统数字接收机，压缩采样接收机得益于重构算法的优越性对模拟数字转换器非线性因素影响有更好的鲁棒性。仿真结果验证了上述理论分析。
Hard Loops, Soft Loops, and High Density Effective Field Theory
Schäfer, T
2003-01-01
We study several issues related to the use of effective field theories in QCD at large baryon density. We show that the power counting is complicated by the appearance of two scales inside loop integrals. Hard dense loops involve the large scale $mu^2$ and lead to phenomena such as screening and damping at the scale $gmu$. Soft loops only involve small scales and lead to superfluidity and non-Fermi liquid behavior at exponentially small scales. Four-fermion operators in the effective theory are suppressed by powers of $1/mu$, but they get enhanced by hard loops. As a consequence their contribution to the pairing gap is only suppressed by powers of the coupling constant, and not powers of $1/mu$. We determine the coefficients of four-fermion operators in the effective theory by matching quark-quark scattering amplitudes. Finally, we introduce a perturbative scheme for computing corrections to the gap parameter in the superfluid phase
Performance evaluation of Type-3 PLLs under wide variation in input voltage and frequency
DEFF Research Database (Denmark)
Aravind, C. K.; Rani, B.Indu; Chakkarapani, M.
2017-01-01
This paper presents a detailed analysis of Type-3 PLL under wide variation in input voltage and frequency. Using small signal modeling, the performance of both single loop and dual loop type-3 PLL for variation in input voltage and frequency is studied. The analysis shows that for the same...... bandwidth, both the single loop and dual loop Type-3 PLL exhibit similar dynamics provided the supply voltage is balanced. However, under voltage sag conditions, dual loop PLL shows improved dynamic response without affecting its stability. Further, the tracking time is reduced as the feed forward frequency...... is a function of supply frequency. To improve the filtering characteristics under frequency deviations, a dual loop Type 3 adaptive PLL which accurately tracks the phase and frequency of the input signal under wide frequency deviations is developed. Simulations are carried out in MATLAB and experimentally...
Frequency Agile Wideband Phase Lock Loops for RF-FPGAs
2013-03-01
defined radios (SDRs) (Borremans [9]), newer standards requiring low integrated phase noise ( WiMAX , LTE) (Tasca [10]), HomeRF SWAP networking...protocol (Willingham [3]), and WiMedia for UWB (Lanka [6]). Note that WiMAX , LTE, and WiMedia examples are research efforts reporting good performance to
Radial propagators and Wilson loops
Leupold, S; Leupold, Stefan; Weigert, Heribert
1996-01-01
We present a relation which connects the propagator in the radial (Fock-Schwinger) gauge with a gauge invariant Wilson loop. It is closely related to the well-known field strength formula and can be used to calculate the radial gauge propagator. The result is shown to diverge in four-dimensional space even for free fields, its singular nature is however naturally explained using the renormalization properties of Wilson loops with cusps and self-intersections. Using this observation we provide a consistent regularization scheme to facilitate loop calculations. Finally we compare our results with previous approaches to derive a propagator in Fock-Schwinger gauge.
Institute of Scientific and Technical Information of China (English)
侯世英; 张诣
2011-01-01
Aiming at the problems that classic phase-locked loop (PLL) has low response speed and detection accuracy under frequency offset of network voltage conditions, a novel analog signal PLL based on coordinate transformation is proposed, and based on the PLL, the model of three-phase voltage source pulse width modulation (PWM) rectifier is built. The rectifier adopts the modulation method of space vector pulse width modulation(SVPWM). According to the circuit topology of the PWM rectifier, the framework of control strategy is given. Also the circuit topology and working principle of PLL are analyzed. Finally, a simulation is done through the Matlab. Simulation results show that the PLL can track the network frequency so well that it can realize phase locking. And the novel PLL can also achieve phase locking under the condition of frequency drift of three-phase network voltage.%为了解决在电网电压出现频率偏移时,传统锁相环响应速度慢、锁相精度差的问题,提出一种基于坐标变换理论的新型模拟信号锁相环,并建立了基于模拟信号锁相环的三相电压型PWM整流器模型.该整流器采用空间矢量脉宽调制(Space Vector Pulse Width Modulation,SVPWM).在对所提PwM整流器的基本拓扑进行分析的基础上,给出了控制策略框图,并分析了新型锁相环的电路结构和工作原理.通过Matlab对所建模型进行了仿真.仿真结果表明:模拟信号锁相环能够快速跟踪系统频率的变化,实现锁相功能.同时,在三相电网电压频率出现小范围漂移情况下,新型锁相环也能够准确锁相.
Global periodic attractor of a class of third-order phase-locked loop
Institute of Scientific and Technical Information of China (English)
林源渠
1997-01-01
The uniform boundedness and existence of a global periodic attractor for a third-order phase-locked loop with general phase detector characteristics and frequency modulation input is proved under some parametric conditions.
Extended Lock Range Zero-Crossing Digital Phase-Locked Loop with Time Delay
Nasir Qassim
2005-01-01
The input frequency limit of the conventional zero-crossing digital phase-locked loop (ZCDPLL) is due to the operating time of the digital circuitry inside the feedback loop. A solution that has been previously suggested is the introduction of a time delay in the feedback path of the loop to allow the digital circuits to complete their sample processing before the next sample is received. However, this added delay will limit the stable operation range and hence lock range of the loop. The ob...
Phase-Locked Loop using a comb filter with fractional delay
Griñó Cubero, Robert; Mughal, Umair Najeeb
2011-01-01
A Phase Locked Loop is a feedback system combining a Voltage Controlled Oscillator and a Phase Comparator These are connected so that the oscillator maintains a constant phase angle relative to a reference signal. Phase locked loops can be used, for example to generate stable output frequency signals from a fixed frequency signal. A Comb Filter is a kind of Notch Filter (Non Recursive Filter) that is normally used to remove the harmonic terms from a particular signal. In this Design, a ...
Product Integrals and Wilson loops
Karp, R L
2001-01-01
Using product integrals we review the unambiguous mathematical representation of Wilson line and Wilson loop operators, including their behavior under gauge transformations and the non-abelian Stokes theorem. Interesting consistency conditions among Wilson lines are also presented.
Thermal fluctuations in loop cosmology
Magueijo, J; Magueijo, Joao; Singh, Parampreet
2007-01-01
Quantum gravitational effects in loop quantum cosmology lead to a resolution of the initial singularity and have the potential to solve the horizon problem and generate a quasi scale-invariant spectrum of density fluctuations. We consider loop modifications to the behavior of the inverse scale factor below a critical scale in closed models and assume a purely thermal origin for the fluctuations. We show that the no-go results for scale invariance in classical thermal models can be evaded even if we just consider modifications to the background (zeroth order) gravitational dynamics. Since a complete and systematic treatment of the perturbed Einstein equations in loop cosmology is still lacking, we simply parameterize their expected modifications. These change quantitatively, but not qualitatively, our conclusions. We thus urge the community to more fully work out this complex aspect of loop cosmology, since the full picture would not only fix the free parameters of the theory, but also provide a model for a no...
Loop Quantum Cosmology Gravitational Baryogenesis
Odintsov, S D
2016-01-01
Loop Quantum Cosmology is an appealing quantum completion of classical cosmology, which brings along various theoretical features which in many cases offer remedy or modify various classical cosmology aspects. In this paper we address the gravitational baryogenesis mechanism in the context of Loop Quantum Cosmology. As we demonstrate, when Loop Quantum Cosmology effects are taken into account in the resulting Friedmann equations for a flat Friedmann-Robertson-Walker Universe, then even for a radiation dominated Universe, the predicted baryon-to-entropy ratio from the gravitational baryogenesis mechanism is non-zero, in contrast to the Einstein-Hilbert case, in which case the baryon-to-entropy ratio is zero. We also discuss various other cases apart from the radiation domination case, and we discuss how the baryon-to-entropy ratio is affected from the parameters of the quantum theory. In addition, we use illustrative exact solutions of Loop Quantum Cosmology and we investigate under which circumstances the bar...
Continuous smearing of Wilson Loops
Lohmayer, Robert
2011-01-01
Continuum smearing was introduced in section 4.1 of JHEP03, 064 (2006) as a meaningful continuum analogue of the well known set of lattice techniques by the same name. Here we apply continuous smearing in continuous space-time to Wilson loops in order to clarify what it does in the context of field theory and also in the context of the loop calculus of the Makeenko-Migdal equation.
The Projectile inside the Loop
Varieschi, Gabriele U.
2005-01-01
In this paper we describe an alternative use of the loop-the-loop apparatus, which can be used to study an interesting case of projectile motion. We also present an effective way to perform and analyze these experiments, by using video capture software together with a digital video camera. These experiments can be integrated into classroom demonstrations for general physics courses, or become part of laboratory activities.
Introduction to Loop Quantum Gravity
Mercuri, Simone
2010-01-01
The questions I have been asked during the 5th International School on Field Theory and Gravitation, have compelled me to give an account of the premises that I consider important for a beginner's approach to Loop Quantum Gravity. After a description of some general arguments and an introduction to the canonical theory of gravity, I review the background independent approach to quantum gravity, giving only a brief survey of Loop Quantum Gravity.
Bifurcations of nontwisted heteroclinic loop
Institute of Scientific and Technical Information of China (English)
田清平; 朱德明
2000-01-01
Bifurcations of nontwisted and fine heteroclinic loops are studied for higher dimensional systems. The existence and its associated existing regions are given for the 1-hom orbit and the 1-per orbit, respectively, and bifurcation surfaces of the two-fold periodic orbit are also obtained. At last, these bifurcation results are applied to the fine heteroclinic loop for the planar system, which leads to some new and interesting results.
宽带8PSK解调高速数传接收机设计*%Design of a High Data Rate Receiver with Wideband 8PSK Demodulation
Institute of Scientific and Technical Information of China (English)
刘景元
2013-01-01
Because of the thermal noise,large Doppler and intersymbol interference in a satellite communication link,high data rate receiver(HDR)with 8-Phase Shift Keying(8PSK)demodulation is used in tracking and data relay satellite system(TDRSS). A wideband 8PSK demodulation technology is proposed. The technology employs Gardner algorithm as timing synchronizer,Maximum Likelihood(ML)Decision-Directed(DD)method as phase detector and a fractionally spaced constant modulus algorithm(FS-CMA)equalization to improve demodulation performance.A receiver based on the technology is implemented by using field programmable gate array (FPGA) and a 600 Megabits per second(Mbps)8PSK signal has been tested. According to the theoretical approach,the demodulation loss difference between tested value and theoretical value is less than 2 dB when the Bit Error Rate (BER)ranges 1 × 10-3 to 1 × 10-8 . China′s new generation TDRSS can employ the receiver as its wideband 8PSK demodulator.% 受卫星信道热噪声、多普勒、畸变影响，传统八进制相位键控(8PSK)接收机性能不佳，速率不高，较少应用于航天测控通信系统.针对这一问题，设计并实现了一种基于FPGA的航天测控系统宽带8PSK解调高速数传接收机，采用Gardner算法实现时钟恢复，利用基于最大似然估计的鉴相算法完成载波同步，并用分数间隔的并行恒模均衡算法提高接收性能.该技术已应用于某接收系统并实现了600 Mb/s 8PSK信号解调，误码率在1×10-3~1×10-8之间时，解调损失与理论值不超过2 d B.宽带8 P S K解调高速数传接收机可为我国二代中继系统提供支持.
Modelling of Closed Loop Class E Inverter Based Induction Heater
Directory of Open Access Journals (Sweden)
S. Arumugam
2011-01-01
Full Text Available This study presents simulation of class E inverter based induction heater system using simulink. DC is converted into high frequency AC using class E inverter. This high frequency AC is used for induction heating. Closed loop systems are modeled and they are simulated using Mat lab Simulink.The results of closed loop systems are presented. The proposed amplifier with two series-parallel resonant load networks will allow sinusoidal output voltage to be achieved by associating with the positive and negative quasi-sinusoidal waveforms. The complementarily activated configuration will provide continuous high-ripple-frequency inputcurrent waveforms; this approach significantly reduces electromagnetic interference and requires very little filtering. With the symmetry of the push-pull Class-E Circuit, there is the additional benefit that the even harmonics are suppressed at the load, and thus there are fewer harmonic distortions.
Abid, Abdulbasit
2013-03-01
This paper presents a thorough discussion of the proposed field-programmable gate array (FPGA) implementation for fringe pattern demodulation using the one-dimensional continuous wavelet transform (1D-CWT) algorithm. This algorithm is also known as wavelet transform profilometry. Initially, the 1D-CWT is programmed using the C programming language and compiled into VHDL using the ImpulseC tool. This VHDL code is implemented on the Altera Cyclone IV GX EP4CGX150DF31C7 FPGA. A fringe pattern image with a size of 512×512 pixels is presented to the FPGA, which processes the image using the 1D-CWT algorithm. The FPGA requires approximately 100 ms to process the image and produce a wrapped phase map. For performance comparison purposes, the 1D-CWT algorithm is programmed using the C language. The C code is then compiled using the Intel compiler version 13.0. The compiled code is run on a Dell Precision state-of-the-art workstation. The time required to process the fringe pattern image is approximately 1 s. In order to further reduce the execution time, the 1D-CWT is reprogramed using Intel Integrated Primitive Performance (IPP) Library Version 7.1. The execution time was reduced to approximately 650 ms. This confirms that at least sixfold speedup was gained using FPGA implementation over a state-of-the-art workstation that executes heavily optimized implementation of the 1D-CWT algorithm.
Higher-order modulations of fs laser pulses for GHz frequency domain photon migration system.
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.
Thermal-Diffusivity-Based Frequency References in Standard CMOS
Kashmiri, S.M.
2012-01-01
In recent years, a lot of research has been devoted to the realization of accurate integrated frequency references. A thermal-diffusivity-based (TD) frequency reference provides an alternative method of on-chip frequency generation in standard CMOS technology. A frequency-locked loop locks the
Thermal-Diffusivity-Based Frequency References in Standard CMOS
Kashmiri, S.M.
2012-01-01
In recent years, a lot of research has been devoted to the realization of accurate integrated frequency references. A thermal-diffusivity-based (TD) frequency reference provides an alternative method of on-chip frequency generation in standard CMOS technology. A frequency-locked loop locks the outpu
Linearized broadband optical detector: study and implementation of optical phase-locked loop
Murakowski, Janusz; Schneider, Garrett J.; Schuetz, Christopher A.; Shi, Shouyuan; Prather, Dennis W.
2013-12-01
Optical phase-locked loop (OPLL) is used to improve the linearity of an optical link for transmission of analog signals. The finite loop delay and the presence of a low-pass filter, required for stable loop operation, lead to a nontrivial frequency response. Here, the linearity improvement in OPLL is investigated, and simple relation among the loop delay, the open-loop gain, and the loop-filter bandwidth that must be satisfied for stable operation of the OPLL is found. This relation is used to determine the fundamental limit on spur-free dynamic range (SFDR) improvement that OPLL can offer over a conventional Mach-Zehnder (MZ)-type detector.
Robot impedance control and passivity analysis with inner torque and velocity feedback loops
Institute of Scientific and Technical Information of China (English)
Michele FOCCHI; Gustavo A MEDRANO-CERDA; Thiago BOAVENTURA; Marco FRIGERIO; Claudio SEMINI; Jonas BUCHLI; Darwin G CALDWELL
2016-01-01
Impedance control is a well-established technique to control interaction forces in robotics. However, real implementations of impedance control with an inner loop may suffer from several limitations. In particular, the viable range of stable stiffness and damping values can be strongly affected by the bandwidth of the inner control loops (e.g., a torque loop) as well as by the filtering and sampling frequency. This paper provides an extensive analysis on how these aspects influence the stability region of impedance parameters as well as the passivity of the system. This will be supported by both simulations and experimental data. Moreover, a methodology for designing joint impedance controllers based on an inner torque loop and a positive velocity feedback loop will be presented. The goal of the velocity feedback is to increase (given the constraints to preserve stability) the bandwidth of the torque loop without the need of a complex controller.
The impacting filter bank design for MCP-EBPSK multicarrier demodulation%用于多路MCP-EBPSK信号解调的冲击滤波器组设计
Institute of Scientific and Technical Information of China (English)
陈志敏; 吴乐南; 陈贤卿
2012-01-01
修正的随机极性连续相位扩展的二元相移键控调制(MCP-EBPSK)通过随机化调制指数的符号,并加入功率谱调节系数,进一步降低了连续相位扩展的二元相移键控(CP-EBPSK)调制信号功率谱中的线谱分量,使得功率谱占用带宽更窄,信息传输更加的高效高速.多载波作为高频谱利用率的复用调制方式,与MCP-EBPSK结合势必会带来更高的系统性能,因此本文对用于解调单路MCP-EBPSK信号的冲击滤波器进行初步改进,通过添加陷波零点来抑制旁路干扰,设计出带陷波的冲击滤波器组.引入量子粒子群优化算法对加入陷波的冲击滤波器组进行优化得到滤波器组系数,仿真显示即使时频混叠的子载波间不满足正交关系,利用各冲击滤波器中心频率处极陡峭的陷波选频特性依然可以实现各子载波的正确解调.因此,设计的冲击滤波器组可以用于子载波无保护间隔的多路MCP-EBPSK信号解调.%The modified pseudo-random extended binary phase shift keying with continous phase ( MCP-EBPSK) could effectively reduce the spectral line compared with the continuous phase extended BPSK( CP-EBPSK) , which could narrow the power spectrum by adding the modified coefficients and randomizing the sign of the modulation index of CP-EBPSK, finally realized the efficient and high data rate transmission. Multiplexing as a high spectral efficiency technique, combined with the MCP-EBPSK would certainly bring better performance. In this paper we improved the impacting filter and designed the filter bank by adding zeros to the impacting filters at the notch frequencies to depress the inter-channel interference (ICI). Use the QPSO (Quantum-behaved Particle Swarm Optimization) algorithm to obtain the filter bank's parameters, the simulation shown that though the subcarriers were time-frequency aliasing and nonorthogonal, the impacting filter bank could separate the composite signal and demodulated properly
Arbitrary optical frequency synthesis traced to an optical frequency comb
Cai, Zihang; Zhang, Weipeng; Yang, Honglei; Li, Yan; Wei, Haoyun
2016-11-01
An arbitrary optical frequency synthesizer with a broad tuning range and high frequency accuracy is presented. The system includes an external cavity diode laser (ECDL) as the output laser, an Erbium-doped optical frequency comb being a frequency reference, and a control module. The optical frequency from the synthesizer can be continuously tuned by the large-scale trans-tooth switch and the fine intra-tooth adjustment. Robust feedback control by regulating the current and PZT voltage enables the ECDL to phase-lock to the Erbium-doped optical frequency comb, therefore to keep stable frequency output. In the meanwhile, the absolute frequency of the synthesizer is determined by the repetition rate, the offset frequency and the beat frequency. All the phase lock loops in the system are traced back to a Rubidium clock. A powerful and friendly software is developed to make the operation convenient by integrating the functions of frequency setting, tuning, tracing, locking and measuring into a LabVIEW interface. The output frequency tuning span and the uncertainty of the system are evaluated as >6 THz and Ring-Down Spectroscopy.
Bol loops of odd prime exponent
Foguel, Tuval
2009-01-01
Although any finite Bol loop of odd prime exponent is solvable, we show there exist such Bol loops with trivial center. We also construct finitely generated, infinite, simple Bruck loops of odd prime exponent for sufficiently large primes. This shows that the Burnside problem for Bruck loops has a negative answer.
Classifying Finitely Generated Indecomposable RA Loops
Cornelissen, Mariana
2012-01-01
In 1995, E. Jespers, G. Leal and C. Polcino Milies classified all finite ring alternative loops (RA loops for short) which are not direct products of proper subloops. In this paper we extend this result to finitely generated RA loops and provide an explicit description of all such loops.
Kalman Orbit Optimized Loop Tracking
Young, Lawrence E.; Meehan, Thomas K.
2011-01-01
Under certain conditions of low signal power and/or high noise, there is insufficient signal to noise ratio (SNR) to close tracking loops with individual signals on orbiting Global Navigation Satellite System (GNSS) receivers. In addition, the processing power available from flight computers is not great enough to implement a conventional ultra-tight coupling tracking loop. This work provides a method to track GNSS signals at very low SNR without the penalty of requiring very high processor throughput to calculate the loop parameters. The Kalman Orbit-Optimized Loop (KOOL) tracking approach constitutes a filter with a dynamic model and using the aggregate of information from all tracked GNSS signals to close the tracking loop for each signal. For applications where there is not a good dynamic model, such as very low orbits where atmospheric drag models may not be adequate to achieve the required accuracy, aiding from an IMU (inertial measurement unit) or other sensor will be added. The KOOL approach is based on research JPL has done to allow signal recovery from weak and scintillating signals observed during the use of GPS signals for limb sounding of the Earth s atmosphere. That approach uses the onboard PVT (position, velocity, time) solution to generate predictions for the range, range rate, and acceleration of the low-SNR signal. The low- SNR signal data are captured by a directed open loop. KOOL builds on the previous open loop tracking by including feedback and observable generation from the weak-signal channels so that the MSR receiver will continue to track and provide PVT, range, and Doppler data, even when all channels have low SNR.
Tran, Lan; El-Araby, Esam; Namazi, Nader
2013-09-01
Free-Space Optical (FSO) communications is a vital area of research due to its important advantages of providing a very large bandwidth and relatively low cost of implementation. One of the inherent limitations on the quality of an FSO communication link is the degradation of the received beam due to atmospheric turbulence. This paper is concerned with prototyping a wavelet-based algorithm to remove or reduce the effect of the scintillation noise and other unwanted signal on an FSO link that uses analog frequency modulation. The applicability of these concepts will be demonstrated by providing a real-time prototype using reconfigurable hardware, namely Field Programmable Gate Arrays (FPGA), and high-level design tools such as System Generator for DSP from Xilinx. Our proposed prototype was realized on the Virtex-6 FPGA ML605 board using the XC6VLX240T-1FFG1156 device.
Study of the Open Loop and Closed Loop Oscillator Techniques
Energy Technology Data Exchange (ETDEWEB)
Imel, George R. [Idaho State Univ., Pocatello, ID (United States); Baker, Benjamin [Idaho National Lab. (INL), Idaho Falls, ID (United States); Riley, Tony [Knolls Atomic Power Lab. (KAPL), Schenectady, NY (United States); Langbehn, Adam [Puget Sound Naval Base, Bremerton, WA (United States); Aryal, Harishchandra [Idaho State Univ., Pocatello, ID (United States); Benzerga, M. Lamine [Idaho State Univ., Pocatello, ID (United States)
2015-04-11
This report presents the progress and completion of a five-year study undertaken at Idaho State University of the measurement of very small worth reactivity samples comparing open and closed loop oscillator techniques.The study conclusively demonstrated the equivalency of the two techniques with regard to uncertainties in reactivity values, i.e., limited by reactor noise. As those results are thoroughly documented in recent publications, in this report we will concentrate on the support work that was necessary. For example, we describe in some detail the construction and calibration of a pilot rod for the closed loop system. We discuss the campaign to measure the required reactor parameters necessary for inverse-kinetics. Finally, we briefly discuss the transfer of the open loop technique to other reactor systems.
BPS Wilson Loops on S^2 at Higher Loops
Young, Donovan
2008-01-01
We consider supersymmetric Wilson loops of the variety constructed by Drukker, Giombi, Ricci, and Trancanelli, whose spatial contours lie on a two-sphere. Working to second order in the 't Hooft coupling in planar N=4 Supersymmetric Yang-Mills Theory (SYM), we compute the vacuum expectation value of a wavy-latitude and of a loop composed of two longitudes. We evaluate the resulting integrals numerically and find that the results are consistent with the zero-instanton sector calculation of Wilson loops in 2-d Yang-Mills on S^2 performed by Bassetto and Griguolo. We also consider the connected correlator of two distinct latitudes to third order in the 't Hooft coupling in planar N=4 SYM. We compare the result in the limit where the latitudes become coincident to a perturbative calculation in 2-d Yang-Mills on S^2 using a light-cone Wu-Mandelstam-Leibbrandt prescription. The two calculations produce differing results.
Generalized loop space and TMDs
Directory of Open Access Journals (Sweden)
Mertens Tom
2014-06-01
Full Text Available The Standard Model describes the three (of four basic interactions known in Nature in terms of the quantum fields which are constituted by representations of special unitary gauge groups of symmetry. However, the physical observables do not always coincide with the fundamental degrees of freedom of the Standard Model. Therefore it can be useful to switch to the loop space representation of the gauge theory, where the variables are inherently gauge invariant but the degrees of freedom are absorbed in the path/loop dependence. Over-completeness of this space requires the introduction of an equivalence relation which is provided by Wilson loop functionals operating on piecewise regular paths. It is well known that certain Wilson loops show the same singularity structure as some Transverse Momentum Dependent PDFs (TMDs, which are not renormalizable by the common methods due to exactly this singularity structure. By introducing geometrical operators, like the area-derivative, we were able to derive an evolution equation for these Wilson loops and we hope to apply this method in the future to find some renormalization schemes for TMDs.
Loop coupled resonator optical waveguides.
Song, Junfeng; Luo, Lian-Wee; Luo, Xianshu; Zhou, Haifeng; Tu, Xiaoguang; Jia, Lianxi; Fang, Qing; Lo, Guo-Qiang
2014-10-06
We propose a novel coupled resonator optical waveguide (CROW) structure that is made up of a waveguide loop. We theoretically investigate the forbidden band and conduction band conditions in an infinite periodic lattice. We also discuss the reflection- and transmission- spectra, group delay in finite periodic structures. Light has a larger group delay at the band edge in a periodic structure. The flat band pass filter and flat-top group delay can be realized in a non-periodic structure. Scattering matrix method is used to calculate the effects of waveguide loss on the optical characteristics of these structures. We also introduce a tunable coupling loop waveguide to compensate for the fabrication variations since the coupling coefficient of the directional coupler in the loop waveguide is a critical factor in determining the characteristics of a loop CROW. The loop CROW structure is suitable for a wide range of applications such as band pass filters, high Q microcavity, and optical buffers and so on.
Unzipping DNA by a periodic force: hysteresis loop area and its scaling.
Kapri, Rajeev
2014-12-01
Using Monte Carlo simulations, we study the hysteresis in the unzipping of double-stranded DNA whose ends are subjected to a time-dependent periodic force with frequency (ω) and amplitude (G). For the static force, i.e., ω→0, the DNA is in equilibrium with no hysteresis. On increasing ω, the area of the hysteresis loop initially increases and becomes maximum at frequency ω*(G), which depends on the force amplitude G. If the frequency is increased further, we find that for lower amplitudes the loop area decreases monotonically to zero, but for higher amplitudes it has an oscillatory component. The height of subsequent peaks decreases, and finally the loop area becomes zero at very high frequencies. The number of peaks depends on the length of the DNA. We give a simple analysis to estimate the frequencies at which maxima and minima occur in the loop area. We find that the area of the hysteresis loop scales as 1/ω in the high-frequency regime, whereas it scales as G(α)ω(β) with exponents α=1 and β=5/4 at low frequencies. The values of the exponents α and β are different from the exponents reported earlier based on the hysteresis of small hairpins.
Vertically Polarized Omnidirectional Printed Slot Loop AntennaPrinted Slot Loop Antenna (invited)
DEFF Research Database (Denmark)
Kammersgaard, Nikolaj Peter Iversen; Kvist, Søren Helstrup; Thaysen, Jesper
2015-01-01
A novel verticall A novel vertically polarized dpolarize , omnidirection omnidirectional l , printed slot loop antenna h sprinted slot loop antenna has been designed, simulated, fabricated, and measured. The slot loop works as a magnetic loop. The loop is loaded with inductors to insure uniform...
Carrier-separating demodulation of phase shifting self-mixing interferometry
Tao, Yufeng; Wang, Ming; Xia, Wei
2017-03-01
A carrier separating method associated with noise-elimination had been introduced into a sinusoidal phase-shifting self-mixing interferometer. The conventional sinusoidal phase shifting self-mixing interferometry was developed into a more competitive instrument with high computing efficiency and nanometer accuracy of λ / 100 in dynamical vibration measurement. The high slew rate electro-optic modulator induced a sinusoidal phase carrier with ultralow insertion loss in this paper. In order to extract phase-shift quickly and precisely, this paper employed the carrier-separating to directly generate quadrature signals without complicated frequency domain transforms. Moreover, most noises were evaluated and suppressed by a noise-elimination technology synthesizing empirical mode decomposition with wavelet transform. The overall laser system was described and inherent advantages such as high computational efficiency and decreased nonlinear errors of the established system were demonstrated. The experiment implemented on a high precision PZT (positioning accuracy was better than 1 nm) and compared with laser Doppler velocity meter. The good agreement of two instruments shown that the short-term resolution had improved from 10 nm to 1.5 nm in dynamic vibration measurement with reduced time expense. This was useful in precision measurement to improve the SMI with same sampling rate. The proposed signal processing was performed in pure time-domain requiring no preprocessing electronic circuits.
A simple frequency sweep linearization method for FM density profile reflectometry
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.
Fiber Bragg-grating strain sensor interrogation using laser radio-frequency modulation.
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.
Laser Metrology Heterodyne Phase-Locked Loop
Loya, Frank; Halverson, Peter
2009-01-01
A method reduces sensitivity to noise in a signal from a laser heterodyne interferometer. The phase-locked loop (PLL) removes glitches that occur in a zero-crossing detector s output [that can happen if the signal-to-noise ratio (SNR) of the heterodyne signal is low] by the use of an internal oscillator that produces a square-wave signal at a frequency that is inherently close to the heterodyne frequency. It also contains phase-locking circuits that lock the phase of the oscillator to the output of the zero-crossing detector. Because the PLL output is an oscillator signal, it is glitch-free. This enables the ability to make accurate phase measurements in spite of low SNR, creates an immunity to phase error caused by shifts in the heterodyne frequency (i.e. if the target moves causing Doppler shift), and maintains a valid phase even when the signal drops out for brief periods of time, such as when the laser is blocked by a stray object.
A comprehensive sensitivity analysis of central-loop MRS data
Behroozmand, Ahmad; Auken, Esben; Dalgaard, Esben; Rejkjaer, Simon
2014-05-01
In this study we investigate the sensitivity analysis of separated-loop magnetic resonance sounding (MRS) data and, in light of deploying a separate MRS receiver system from the transmitter system, compare the parameter determination of the central-loop with the conventional coincident-loop MRS data. MRS, also called surface NMR, has emerged as a promising surface-based geophysical technique for groundwater investigations, as it provides a direct estimate of the water content and, through empirical relations, is linked to hydraulic properties of the subsurface such as hydraulic conductivity. The method works based on the physical principle of NMR during which a large volume of protons of the water molecules in the subsurface is excited at the specific Larmor frequency. The measurement consists of a large wire loop deployed on the surface which typically acts as both a transmitter and a receiver, the so-called coincident-loop configuration. An alternating current is passed through the loop deployed and the superposition of signals from all precessing protons within the investigated volume is measured in a receiver loop; a decaying NMR signal called Free Induction Decay (FID). To provide depth information, the FID signal is measured for a series of pulse moments (Q; product of current amplitude and transmitting pulse length) during which different earth volumes are excited. One of the main and inevitable limitations of MRS measurements is a relatively long measurement dead time, i.e. a non-zero time between the end of the energizing pulse and the beginning of the measurement, which makes it difficult, and in some places impossible, to record MRS signal from fine-grained geologic units and limits the application of advanced pulse sequences. Therefore, one of the current research activities is the idea of building separate receiver units, which will diminish the dead time. In light of that, the aims of this study are twofold: 1) Using a forward modeling approach, the
All digital pulsewidth control loop
Huang, Hong-Yi; Jan, Shiun-Dian; Pu, Ruei-Iun
2013-03-01
This work presents an all-digital pulsewidth control loop (ADPWCL). The proposed system accepts a wide range of input duty cycles and performs a fast correction to the target output pulsewidth. An all-digital delay-locked loop (DLL) with fast locking time using a simplified time to digital converter and a new differential two-step delay element is proposed. The area of the delay element is much smaller than that in conventional designs, while having the same delay range. A test chip is verified in a 0.18-µm CMOS process. The measured duty cycle ranges from 4% to 98% with 7-bit resolution.
Loop quantum cosmology: Recent progress
Indian Academy of Sciences (India)
Martin Bojowald
2004-10-01
Aspects of the full theory of loop quantum gravity can be studied in a simpler context by reducing to symmetric models like cosmological ones. This leads to several applications where loop effects play a significant role when one is sensitive to the quantum regime. As a consequence, the structure of and the approach to classical singularities are very different from general relativity. The quantum theory is free of singularities, and there are new phenomenological scenarios for the evolution of the very early universe such as inflation. We give an overview of the main effects, focussing on recent results obtained by different groups.
Loop quantum geometry: a primer
Energy Technology Data Exchange (ETDEWEB)
Corichi, Alejandro [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, A. Postal 70-543, Mexico D.F. 04510 (Mexico)
2005-01-15
This is the written version of a lecture given at the 'VI Mexican School of Gravitation and Mathematical Physics' (Nov 21-27, 2004, Playa del Carmen, Mexico), introducing the basics of Loop Quantum Geometry. The purpose of the written contribution is to provide a Primer version, that is, a first entry into Loop Quantum Gravity and to present at the same time a friendly guide to the existing pedagogical literature on the subject. This account is geared towards graduate students and non-experts interested in learning the basics of the subject.
LISA Pathfinder: OPD loop characterisation
Born, Michael; LPF Collaboration
2017-05-01
The optical metrology system (OMS) of the LISA Pathfinder mission is measuring the distance between two free-floating test masses with unprecedented precision. One of the four OMS heterodyne interferometers reads out the phase difference between the reference and the measurement laser beam. This phase from the reference interferometer is common to all other longitudinal interferometer read outs and therefore subtracted. In addition, the phase is fed back via the digital optical pathlength difference (OPD) control loop to keep it close to zero. Here, we analyse the loop parameters and compare them to on-ground measurement results.
Loop Quantum Geometry: A primer
Corichi, Alejandro
2005-01-01
This is the written version of a lecture given at the ``VI Mexican School of Gravitation and Mathematical Physics" (Nov 21-27, 2004, Playa del Carmen, Mexico), introducing the basics of Loop Quantum Geometry. The purpose of the written contribution is to provide a Primer version, that is, a first entry into Loop Quantum Gravity and to present at the same time a friendly guide to the existing pedagogical literature on the subject. This account is geared towards graduate students and non-expert...
Frequency domain analysis of noise in autoregulated gene circuits
Simpson, Michael L.; Cox, Chris D.; Sayler, Gary S.
2003-01-01
We describe a frequency domain technique for the analysis of intrinsic noise within negatively autoregulated gene circuits. This approach is based on the transfer function around the feedback loop (loop transmission) and the equivalent noise bandwidth of the system. The loop transmission, T, is shown to be a determining factor of the dynamics and the noise behavior of autoregulated gene circuits, and this T-based technique provides a simple and flexible method for the analysis of noise arisin...
Offset phase locking of noisy diode lasers aided by frequency division
Ivanov, E. N.; Esnault, F.-X.; Donley, E. A.
2011-08-01
For heterodyne phase locking, frequency division of the beat note between two oscillators can improve the reliability of the phase lock and the quality of the phase synchronization. Frequency division can also reduce the size, weight, power, and cost of the instrument by excluding the microwave synthesizer from the control loop when the heterodyne offset frequency is large (5 to 10 GHz). We have experimentally tested the use of a frequency divider in an optical phase-lock loop and compared the achieved level of residual phase fluctuations between two diode lasers with that achieved without the use of a frequency divider. The two methods achieve comparable phase stability provided that sufficient loop gain is maintained after frequency division to preserve the required bandwidth. We have also numerically analyzed the noise properties and internal dynamics of phase-locked loops subjected to a high level of phase fluctuations, and our modeling confirms the expected benefits of having an in-loop frequency divider.
Design and verification of large-moment transmitter loops for geophysical applications
Sternberg, Ben K.; Dvorak, Steven L.; Feng, Wanjie
2017-01-01
In this paper we discuss the modeling, design and verification of large-moment transmitter (TX) loops for geophysical applications. We first develop two equivalent circuit models for TX loops. We show that the equivalent inductance can be predicted using one of two empirical formulas. The stray capacitance of the loop is then calculated using the measured self-resonant frequency and the loop inductance. We model the losses associated with both the skin effect and the dissipation factor in both of these equivalent circuits. We find that the two equivalent circuit models produce the same results provided that the dissipation factor is small. Next we compare the measured input impedances for three TX loops that were constructed with different wire configurations with the equivalent circuit model. We found excellent agreement between the measured and simulated results after adjusting the dissipation factor. Since the skin effect and dissipation factor yield good agreement with measurements, the proximity effect is negligible in the three TX loops that we tested. We found that the effects of the dissipation factor dominated those of the skin effect when the wires were relatively close together. When the wires were widely separated, then the skin effect was the dominant loss mechanism. We also found that loops with wider wire separations exhibited higher self-resonant frequencies and better high-frequency performance.
An Anti-multipath Frequency Hopped Communication Technique in Shallow-water Acoustic Channels
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
This paper introduces a frequency-hopped (FH) communication system to anti-intersymbol interferences (ISI) caused by the multipath propagation in shallow-water acoustic channels, and uses high-speed digital signal processor (DSP) and serial ADC (MAX121) chip to demodulate received signal efficiently based Fast Fourier Transform (FFT) algorithm. The field experimental results show: a data rate of 1Kbit/s with the bit error rates on the order of 10-4 is demonstrated at 2000 m in the shallow-water acoustic channel of Xiamen harbor, and the key techniques of the system is analyzed in the paper.
Institute of Scientific and Technical Information of China (English)
魏世朋; 张天骐; 白娟; 余熙
2011-01-01
Concerning the high BER and the phase ambiguity of the π/4-DQPSK signal's traditional demodulation method in low SNR, the demodulation method based on duffing oscillator arrays was studied.π/4-DQPSK signal's 8 phases correspond with the 8 points in its constellation figure, firstly, the constellation is divided into 4 overlapping regions and each region contains 3 phases, then we put the π/4-DQPSK into the Duffing oscillator arrays as the tested signal, we can know which regions the current ir/4-DQPSK is in from he power spectrum entropy of Duffing oscillator arrays's output signal. Later, use a set of decision rules to decide which point the current signal belong and recovered the I, Q branch signals. Finally, use the differential decoding and parallel /serial conversion to recover the digital information which we sent out. The simulation results show that this demodulation method is suitable for demodulating the π/4-DQPSK signal in Gaussian channel and Rice channel.%首次提出了微弱π/4-DQPSK信号Duffing振子阵列的解调算法,并用计算机对此算法进行了相应的仿真验证,同时还创造性地提出了星座图重叠划分,功率谱熵计算阵列和Duffing振子码元分界点搜寻器.先将π/4-DQPSK星座图的8个点划分成相重叠的四个区域,然后用功率谱熵来判定不同区域内Duffing振子的不同响应,最后依据当前时刻Duffing振子阵列的不同响应来断定所传送的数字信息.计算机仿真结果表明,本算法切实可行,在高斯信道中解调信噪比最低可达-15.6 dB.