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Acquirement and enhancement of remote speech signals

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Optoelectronics Letters 2017年第4期13卷 275-278页

作者： LIU Tao GUO Jin ZHANG He-yong YAN Chun-hui WANG Can-jin Changchun Institute of Optics Fine Mechanics and Physics Chinese Academy of Sciences Changchun 130033 China University of Chinese Academy of Science Beijing 100049 China

To address the challenges of non-cooperative and remote acoustic detection, an all-fiber laser Doppler vibrometer(LDV) is established. The all-fiber LDV system can offer the advantages of smaller size, lightweight design and robust structure, hence it is a better fit for remote speech detection. In order to improve the performance and the efficiency of LDV for long-range hearing, the speech enhancement technology based on optimally modified log-spectral amplitude(OM-LSA) algorithm is used. The experimental results show that the comprehensible speech signals within the range of 150 m can be obtained by the proposed LDV. The signal-to-noise ratio(SNR) and mean opinion score(MOS) of the LDV speech signal can be increased by 100% and 27%, respectively, by using the speech enhancement technology. This all-fiber LDV, which combines the speech enhancement technology, can meet the practical demand in engineering.

关键词： Audition Fiber lasers Laser Doppler velocimeters signal to noise ratio Speech Speech enhancement

Implementation of a Novel Algorithm on Acoustic Doppler Current Profiler signal Processing System

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Transactions of Tianjin University 2005年第4期11卷 299-302页

作者：朱昊刘文耀 Key Laboratory of Opto-Electronics Information and Technical Science of Ministry of Education School of Precision Instruments and Opto-Electronic Engineering Tianjin University Tianjin 300072 China

Acoustic Doppler current profiler （ADCP） uses acoustic energy directed along narrow beams for current measurement. In conventional method, the quantity of sampling affects the precision of fast Fourier transform （FFT） algorithm, and the algorithm needs a large amount of data to process. A novel frequency *** least mean square （ELMS） algorithm for a single complex sinusoid in complex white Gaussian noise, is proposed in ADCP system. As sampling frequency equals 120 krad/s and the sampling number equals 240. the minimum resolving is 0. 5 krad/s. All variances keep 11.11%. ELMS algorithm needs less data than FFT. And the robust algorithm can estimate the spectrum true value to 99.9% when the signal to noise ratio （SNR） is equal to 0 dB. Experiments prove that the estimation values will diverge much from the ideal when SNR is less than -6 dB.

关键词： acoustic Doppler current profiler: fast Fourier transform Gaussian noise enhanced least mean square signal to noise ratio

Numerical analysis on an OOK-NRZ visible light communication system based on a single white LED

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Optoelectronics Letters 2011年第5期7卷 376-379页

作者：贾永坡叶玮琳田崇文全相印王嘉琪宋占伟郑传涛 State Key Laboratory on Integrated Optoelectronics College of Electronic Science and Engineering Jilin University

An OOK-NRZ visible light communication (VLC) system is designed by using a single white LED and a 550 nm visible photodetector. The emitting model of the single LED is established, and the general expression of the detector's output signals under OOK modulation is deduced. With the selected LED, detector and other related parameters, the designed communication system is optimized and its performance is analyzed. The optimized communication distance between the LED and the detector is 0.54 m at the communication bit rate of 1 Mbit/s. With the best communication distance, when the signal-to-noise ratio (SNR) is larger than 6.5 dB, the bit error rate (BER) can drop to 10-4. The analytical model and theory presented in this paper can be of certain practical meanings in the design of similar communication systems.

关键词： Bit error rate Communication systems Detectors Light Mathematical models Numerical analysis Optical communication Optimization signal to noise ratio

signal reconstructing least-squares algorithm for chirp signal parameters estimation

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Signal reconstructing least-squares algorithm for chirp sign...

Automatic Digital Modulation Recognition Based on Support Vector Machines

2006 8th International Conference on signal Processing

作者： Liangchen Zhou Jianyu Yang Bin Tang Nanjun Li School of Electronic Engineering University of Electronic Science and Technology of China

ISBN: (纸本)0780397371

＜正＞In this paper,we proposed signal reconstructing least-square（SRLS） technique for estimating the chirp rate and initial frequency of chirp *** technique is simplicity,accuracy,and ease of on-line or off-line *** low input signal-to-noise ratio,the estimates are unbiased and achieve CramerRao bound（CRB）.Simulation demonstrated the effectiveness and peformance.

关键词： Chirp Parameter estimation Frequency estimation Phase estimation signal to noise ratio Radar signal processing Maximum likelihood estimation Time frequency analysis Covariance matrix Phase noise

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Automatic Digital Modulation Recognition Based on Support Ve...

Optimization algorithm of near-eye light field displays based on human visual characteristics

2005 International Conference on Neural Networks and Brain(ICNN&B’05)

作者： Zhilu Wu Xuexia Wang Zhenzhen Gao Guanghui Ren School of Electronics and Information Technology Harbin Institute of Technology

ISBN: (纸本)0780394224

＜正＞This paper presents a method based on support vector machines（SVMs） for recognizing digital modulation signals in the presence of additive white Gaussian *** a powerful method for pattern recognition,SVMs with radial basis function（RBF） kernels are incorporated to form the multi-class recognition system which employs the conventional features of each signal obtained from its amplitude,frequency, and phase *** simulations of different types of band-limited digitally modulated signals corrupted by Gaussian white noise have been carried out to measure the performance of the classification *** simulation results that the accuracy rate of this method is at lest 85.67% show that the recognition method based on SVMs is effective. And the performance of the automatic recognition method is very satisfactory with high overall success rates even in a low signal to noise ratio（SNR） environment.

关键词： Digital modulation Support vector machines Pattern recognition signal to noise ratio Additive white noise Kernel Frequency Computer simulation White noise noise measurement

来源： cnki会议评论

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Chinese Optics Letters 2016年第4期14卷 24-28页

作者：丁俊刘玛丽钟擎李海峰刘旭 State Key Lab.of Modern Optical Instrumentation Department of Optical EngineeringZhejiang University

The number of layers and the resolution of liquid crystal displays （LCDs） limit the reconstruction fidelity of near- eye light field displays based on multilayer LCDs. Because the eye＇s resolution capability is different for central vision and peripheral vision, the fidelity can be improved by setting different weights for different areas. First we employ the eye＇s modulation transfer function （MTF） to acquire the limiting resolution angle. Then, due to the inverse relationship between the limiting angle and the weight values, the weighted function related to retinal eccentricity is calculated. In combination with the linear least-squares algorithm, the peak signal-to-noise ratio （PSNR） of the reconstructed scene is raised. The simulation results indicate that the weighted optimization algorithm can improve the image fidelity and reconstruction accuracy.

关键词： Algorithms Liquid crystal displays Optimization signal to noise ratio

Long-range laser ranging using superconducting nanowire single-photon detectors

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Chinese Optics Letters 2016年第7期14卷 42-46页

作者：薛莉李明张蜡宝翟东升李祝莲康琳李语强伏红林明名张森陶旭熊耀恒吴培亨 Key Laboratory for Space Object Measurements Beijing Institute of Tracking and Telecommunications TechnologyBeijing 100094China Research Institute of Superconductor Electronics Nanjing UniversityNanjing 210093China Yunnan Observatory Chinese Academy of SciencesKunming 650011China Changchun Institute of Optics Fine Mechanics and PhysicsChinese Academy of SciencesChangchun 130033China

We demonstrate laser-ranging results for non-cooperative targets at ranges of 237 m and 19 km using superconducting nanowire single-photon detectors （SSPD）. We upgrade the kilohertz rate laser-ranging system with a newly developed SSPD module, and the equivalent detection diameter is enlarged to 50 gm with a fiber and micro-lenses. Both retroreflectors and non-cooperative surfaces of aluminum foil, a solar panel, and a concrete panel at distances of 237 m and 19 km, whose echoes are of single-photon level, are ranged with sub-centimeter precision. Experimental signal-to-noise ratio curves with the product of quantum efficiency and system transmittance are obtained, which indicates that our system, with an average laser power of 0.8 W and a receiving aperture of 1.2 m, may be capable for space debris ranging at a distance of 800 km. This work suggests that SSPDs have the potential to be used for space debris surveillance.

关键词： Avalanche photodiodes Concrete slabs Microlenses Nanowires Photodetectors Photons Precast concrete signal to noise ratio Space debris

Optical heterodyne Herriott-type multipass laser absorption spectrometer

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Chinese Optics Letters 2015年第1期13卷 97-99页

作者：李传亮刘路路邱选兵魏计林邓伦华陈扬骎 Department of Physics School of Applied ScienceTaiyuan University of Science and Technology State Key Laboratory of Precision Spectroscopy East China Normal University

We present a Herriott-type multipass laser absorption spectrometer enhanced by optical heterodyne detection. The proposal is demonstrated by measuring the spectra of water vapor molecule in the region from 12247.6873 to 12249.6954 cm^-1. Compared with direct absorption spectroscopy, the signal-to-noise ratio is improved nearly one magnitude of factor by combining with the optical heterodyne spectroscopy and extra weak absorption lines are observed. The minimum detectable absorption is estimated at 4.36×10^-8 cm^-1 and the measured line shape dominated by Doppler broadening can be precisely recovered by direct transformation of experimental optical heterodyne spectral profile.

关键词： Absorption spectroscopy Heterodyning signal to noise ratio

Tunable femtosecond pulse source from 1.6 to 2.3 μm with 100 kW peak power in an all-fiber system

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Chinese Optics Letters 2016年第9期14卷 58-61页

作者：王鹏师红星谭方舟王璞 National Center of Laser Technology Institute of Laser Engineering Beijing University of Technology

We report a simple and compact all-fiber laser system that is capable of generating widely tunable femtosecond pulses from 1.6 to 2.32 μm. The pulses are produced by utilizing the soliton self-frequency shift in a highly nonlinear fiber pumped by an Er-doped mode-locked fiber laser. Two stages of single-clad Tm：fiber amplifiers are used to amplify the pulses to a higher pulse energy of 10.9 n J with pulse width of 94 fs, and corresponding to peak power of 105 kW at around 1.93 μm. Running a few hours, the all-fiber laser system exhibits exceptional stability with a signal-to-noise ratio as high as 70 dB.

关键词： Electromagnetic pulse Fiber amplifiers Fiber lasers Fibers Nonlinear optics Optical pumping Pumping (laser) signal to noise ratio Ultrafast lasers Ultrashort pulses