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32nd IEEE International Conference on Acoustics, Speech and Signal Processing

作者： Coker, Jonathan D. Tewfik, Ahmed H. Univ Minnesota Dept Elect & Comp Engn Minneapolis MN 55455 USA

ISBN: (纸本)1424407281

We derive a family of sequences which obey a characteristic-phase constraint as it applies to finite sequences. We show these sequences are special cases of the well-known Welti sequences. We construct a transmit waveform which allows extremely efficient decomposition, whose outputs are simultaneously interpretable as adjacent correlation-filter outputs, and as lossless input signal representations. We discuss implementation of receive and transmit functions.

关键词： synthetic aperture radar pulse compression methods wavelet transform

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Characteristic Phase E-Sequences in Efficient pulse-compression methods using Discrete Wavelet Decomposition

Characteristic Phase E-Sequences in Efficient Pulse-Compress...

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International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： Jonathan D. Coker Ahmed H. Tewfik Department of Electrical and Computer Engineering University of Minnesota USA

关键词： Discrete wavelet transforms Signal processing pulse compression methods Very large scale integration Circuits Hardware Propagation losses Signal representations Wavelet transforms Impedance matching

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COMPRESSIVELY STRAINED 1.3-MU-M INASP/INP AND GAINASP/INP MULTIPLE-QUANTUM-WELL LASERS FOR HIGH-SPEED PARALLEL DATA-TRANSMISSION SYSTEMS

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IEEE JOURNAL OF QUANTUM ELECTRONICS 1993年第6期29卷 1536-1543页

作者： FUKUSHIMA, T KASUKAWA, A IWASE, M NAMEGAYA, T SHIBATA, M Furukawa Electric Company Limited Yokohama Japan

Turn-on delay times in the pulse response of compressively strained InAsP/InP double quantum well (DQW) lasers and GaInAsP/InP multiple quantum well (MQW) lasers emitting at 1.3 mum were investigated. The InAsP/InP DQW lasers with 200 mum cavity length and high reflection coating achieved both a very low threshold current of 1.8 mA and a small turn-on delay time (200 ps), even under a bias-less 30 mA pulse current. These are suitable performances for parallel digital data transmitters. Other conventional types of lasers, such as compressively strained or lattice-matched GaInAsP MQW lasers and GaInAsP double-heterostructure (DH) lasers, were also fabricated and compared. It was observed that the carrier lifetime was enhanced for InAsP DQW lasers and strained GaInAsP MQW lasers when it was compared to the lattice-matched GaInAsP MQW lasers and conventional double-heterostructure lasers. To explain this increase in the carrier life-time, the effect of the carrier transport on the carrier life-time was studied. Finally, the additional power penalty due to the laser turn-on delay was simulated and discussed.

关键词： Indium phosphide Quantum well devices Charge carrier lifetime Optical pulses pulse compression methods Coatings Threshold current Delay effects DH-HEMTs Power lasers

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STUDIES ON THE SELF-INITIATED AND LASER-INITIATED DISCHARGE CHARACTERISTICS AT DIELECTRIC GAS INTERFACES

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IEEE TRANSACTIONS ON PLASMA SCIENCE 1989年第4期17卷 588-594页

作者： FOO, KS SUDARSHAN, TS UNIV S CAROLINA DEPT ELECT & COMP ENGNCOLUMBIASC 29208

Two main issues are discussed: (i) the study of arc initiation and propagation in a compressed nitrogen gas spark-gap, initiated by a low-energy (90 mu J) pulsed N/sub 2/ laser (600 ps FWHM) and (ii) the modification of the discharge characteristics due to the presence of a solid insulating space made of Plexiglas (PMMA). The studies are carried out over a pressure range of 0.1 to 0.4 MPa, and for space diameters of 1, 4 and 6 cm, in a planar uniform field gap with 1-cm spacing. Coordinated measurements of discharge current and luminosity with nanosecond response times provide data on discharge current and luminosity risetimes, delay times to the onset of discharge from the instant of laser initiation, and the threshold (minimum) voltage for the onset of discharge due to laser initiation. The results point to some basic processes involving the interaction of the insular surface with : (a) the electron avalanches in the formative stage, and (b) the streamer in the discharge growth phase leading to full conduction. The results demonstrate that the insulator surface impedes the development of both the avalanche and streamer phases of the discharge development.< >

关键词： Gas lasers Delay Surface discharges Optical propagation Nitrogen Spark gaps Optical pulses pulse compression methods Solid lasers Gas insulation

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HIGH compression RATIO BACKWARD RAMAN CONVERSION FOR HIGH-BRIGHTNESS EXCIMER-LASER SYSTEMS

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IEEE JOURNAL OF QUANTUM ELECTRONICS 1993年第7期29卷 2251-2258页

作者： NISHIOKA, H KIMURA, K UEDA, K TAKUMA, H Institute for Laser Science University of Electro-Communications Chofu Japan

A new scheme of backward Raman pulse compression, in which the backward first Stokes pulse is amplified under stationary conditions and the backward second Stokes under transient conditions by choosing an appropriate Raman medium, is proposed. The compression factor and efficiency are improved by insertion of selective absorbers for the second Stokes component. The feasibility of such a scheme is demonstrated by an experiment in which a 249 nm UV pulse of 20 ns duration has been compressed into a 30-ps pulse with an power gain of 150 and energy conversion efficiency of 22%. Higher compression ratio and higher efficiency is expected by under improved conditions.

关键词： Brightness Optical pulses pulse amplifiers Laser excitation Brillouin scattering pulse compression methods Pump lasers Stimulated emission Optical pulse compression Laser beams

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The relation between range sampling rate, system bandwidth, and variance reduction in spectral averaging for meteorological radar

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IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 1996年第3期34卷 612-618页

作者： Urkowitz, H Katz, SL Government Electronic Systems Lockheed Martin Moorestown NJ USA

Periodograms are frequently used in radar meteorology to get spectral moments of weather echo. Each range trace is sampled and the set of samples at each of the specific ranges is used to obtain a pulse-to-pulse periodogram from which the spectral moments are estimated. Over some range interval, the separate periodograms would be averaged to get smoother estimates to be reported. The averaging will reduce the variance of the spectral estimates but the resulting variance is not quite inversely proportional to the number of periodograms because of the correlation introduced by a sampling rate that preserves range resolution. We derive the equivalent number M(eq) of uncorrelated range-samples when M range samples are actually averaged. The factors involved are the 3-dB system half-bandwidth W, the number M, and the range sampling frequency f(s). The formula is M(eq) = M[1 + 2 (r=1)Sigma(M-1) (1-r/M) exp(-28.48r(2)W(2)/f(s)(2))](-1). A table is provided of M(eq) versus M.

关键词： Sampling methods Bandwidth Frequency Filters Meteorological radar pulse compression methods Spectral analysis Transfer functions Fourier transforms Discrete Fourier transforms

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AMBIGUITY FUNCTION OF QUADRIPHASE CODED RADAR pulse

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IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS 1989年第6期25卷 848-853页

作者： LEVANON, N FREEDMAN, A ELTA ELECTR IND ASHDODISRAEL

Taylor\'s quadriphase coding (J.W. Taylor, Jr. and H.J. Blinchikoff, ibid., vol.23, no.2, p.156-70, Mar. 1988) is investigated for nonzero Doppler shifts. While the zero-Doppler cut of the ambiguity function (i.e. the autocorrelation) strongly resembles that of the corresponding biphase code, the remaining ambiguity function differs considerably. The ambiguity function of quadriphase code 13 is typified by a diagonal ridge as found in linear FM signals. The ambiguity function of quadriphase code 28A resembles the three parallel ridges of Frank code 16.

关键词： Autocorrelation Frequency Doppler radar Electronics industry Doppler shift pulse compression methods Switches Signal generators Delay lines Narrowband

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ADAPTIVE CANCELER AND pulse COMPRESSOR INTERACTIONS

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IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS 1991年第2期27卷 331-342页

作者： GERLACH, K Radar Division Naval Research Laboratory Inc. Washington D.C. DC USA

Performance results for the sidelobe level of a compressed pulse that has been preprocessed through an adaptive canceler are obtained. The adaptive canceler is implemented using the sampled matrix inversion (SMI) algorithm. Because of finite sampling, the quiescent compressed pulse sidelobe levels are degraded due to the preprocessing of the main channel input data stream (the uncompressed pulse) through an adaptive canceler. If N is the number of input canceler channels (main and auxiliaries) and K is the number of independent samples per channel, then it is shown that K/N can be significantly greater than one in order to retain sidelobes that are close to the original quiescent sidelobe level (with no adaptive canceler). Also it is shown that the maximum level of degradation is independent of whether pulse compression occurs before or after the adaptive canceler if the uncompressed pulse is completely contained within the K samples that are used to calculate the canceler weights. Furthermore, this same analysis can be used to predict the canceler noise power level which is induced by having the desired signal present in the canceler weight calculation.

关键词： pulse compression methods Degradation Noise cancellation Radar detection Matched filters Clutter Working environment noise Tellurium Laboratories Signal analysis

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WEIGHT EFFECTS ON THE PERIODIC AMBIGUITY FUNCTION

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IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS 1995年第1期31卷 182-193页

作者： GETZ, B LEVANON, N Tel-Aviv University Israel

CW radar signals and processors are discussed. The use of the periodic ambiguity function (PAF) to analyze the delay-Doppler performance of CW signals and their corresponding correlation receivers, is extended to include weight function effects. This work provides tools which can predict the delay-Doppler response of almost any phase-coded CW radar. Examples demonstrate that a combination of CW signals having perfect periodic autocorrelation, a matched reference signal with a large number of modulation periods and a smooth weight function, can create a delay-Doppler response with extremely low sidelobes, strongly resembling the response of a coherent pulse train.

关键词： Autocorrelation Delay effects pulse modulation Doppler radar Signal analysis pulse compression methods Phase modulation Frequency modulation Radar signal processing Signal processing

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Trajectory deviations in airborne SAR: Analysis and compensation

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IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS 1999年第3期35卷 997-1009页

作者： Fornaro, G CNR Ist Ric Elettromagnetismo & Componenti Elettr I-80124 Naples Italy

This paper concerns the analysis and compensation of trajectory deviations in airborne synthetic aperture radar (SAR) systems. Analysis of the received data spectrum is carried out with respect to the system geometry in the presence of linear, sinusoidal, and general aircraft displacements. This shows that trajectory deviations generally produce spectral replicas along the azimuth frequency that strongly impair the quality of the focused image. Based on the derived model, we explain the rationale of the motion compensation (MOCO) strategy that must be applied at the SAR processing stage in order to limit the resolution loss. To this end aberration terms are separated into range space invariant and variant components. The former can be accounted for either in a preprocessing step or efficiently at range compression stage. The latter needs a prior accommodation of range migration effect. We design the procedure for efficient inclusion of the MOCO within a high precision Scaled PT based SAR processing algorithm. Finally, we present results on simulated data aimed at validating the whole analysis and the proposed procedure.

关键词： Synthetic aperture radar Azimuth Focusing pulse compression methods pulse modulation Chirp Motion compensation Layout Airplanes Signal resolution

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