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Double-characters detection of nonlinear frequency modulated signals based on FRFT

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Science china(Information Sciences) 2011年第1期54卷 136-145页

作者： XU ShuWen,SHUI PengLang & YANG xiaoChao national laboratory of radar signal processing,xidian university,xi’an 710071,china 1. national laboratory of radar signal processing Xidian University Xi’an 710071 China

In many practical applications,signals to be detected are unknown nonlinear frequency modulated (FM)and are corrupted by strong *** phase histories of the nonlinear FM signals are assumed to be unknown smooth functions of time,which are usually poorly modeled or cannot be modeled at all by a small number of *** of the lack of phase model,a nonparametric detection method is proposed based on successive fractional Fourier transform and double-characters *** detection process goes in three ***,an image is constructed by the fractional Fourier transforms of successive angles in one period. Then,the threshold procedure is utilized to transform the image into a binary *** the multiple median filtering,the binary image is refined where the isolated noise pixels are ***,two complementary features are extracted from the refined image,and a double-characters detector is proposed to decide whether the target is present or *** simulation experiments to three polynomial phase signals with different orders and a sinusoidal phase signal show that the proposed detection method is effective and robust.

关键词： fractional Fourier transform double-characters detector nonparametric detection multiple median filtering

Generalized adaptive subspace detector for range-Doppler spread target with high resolution radar

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Science china(Information Sciences) 2011年第1期54卷 172-181页

作者： DAI FengZhou,LIU HongWei & WU ShunJun national lab of radar signal processing,xidian university,xi’an 710068,china 1. national lab of radar signal processing Xidian University Xi’an 710068 China

A generalized adaptive subspace detector for range-Doppler spread target(RDST-GASD)in the non-Gaussian clutter is derived in this *** subspace model of multi-pulse wideband radar target returns is established in the frequency-slow time *** clutters are modeled as nonhomogeneous spherically invariant random vectors(SIRVs);that is,the power of the clutter is different from one range cell to *** clutter covariance matrix is estimated with the secondary *** constant false alarm rate(CFAR)property of RDST-GASD with respect to both the power and the covariance matrix of the clutter is demonstrated *** that there is target range walking across range cells during a coherent processing interval(CPI)for wideband radar,the RDST-GASD does range alignment to the multiple returns of the target in a *** a result,the coherent integration is implemented and the detection performance is improved.

关键词： high resolution radar range-Doppler spread target range walking SIRV adaptive subspace de- tector

Correlation analysis of target echoes using distributed transmit array

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Science china(Information Sciences) 2010年第9期53卷 1860-1868页

作者： JIN Ming*,LIAO GuiSheng & LI Jun national laboratory of radar signal processing,xidian university,xi’an 710071,china 1. national laboratory of radar signal processing Xidian University Xi’an 710071 China

Transmit diversity multiple-input multiple-output(MIMO) radars decorrelate target echoes on distributed transmit array,and then through closely spaced receivers array estimate the angles of multiple targets using the received target echoes without separating transmitted *** this paper,the target echoes correlation is analyzed under Swerling I and Ⅱ target model *** results show that:(1) Target echoes are uncorrelated under Swerling II model;(2) under Swerling I model,in order to decrease the correlation of target echoes by increasing the number of transmitters,it is required that the normalized covariance matrices of the signals before and after the transmitter number increases should satisfy a relation given in this ***,the results are verified by computer simulations of the target echoes correlation and angles estimation performance.

关键词： multiple-input multiple-output(MIMO) radar transmit diversity target echoes decorrelation

Time-frequency characteristics based motion estimation and imaging for high speed spinning targets via narrowband waveforms

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Science china(Information Sciences) 2010年第8期53卷 1628-1640页

作者： ZHANG Lei , LI YaChao, LIU Yan, xiNG MengDao & BAO Zheng national lab for radar signal processing, xidian university, xi’an 710071, china 1. national lab for radar signal processing Xidian University Xi’an 710071 China

This paper focuses on the motion parameters estimation and inversed synthetic aperture radar (ISAR) imaging for the high-speed spinning targets via the time-frequency characteristics. Assuming that the translational motion is compensated with the available motion compensation techniques, then the residual part of translational motion and the spinning motion are estimated with high precision based on the timefrequency characteristics. Combining with the procedure of the motion estimation, a novel coherent timefrequency spectrum intensity redistribution method, coherent single range Doppler interferometry (CSRDI), is proposed, which provides higher resolution and sustain lower signal to noise rate (SNR) than the current approach. Numerical simulation confirms the validity and high precision of the proposed approaches.

关键词： ISAR time-frequency characteristics CSRDI motion estimation high speed spinning targets

Generating dense and super-resolution ISAR image by combining bandwidth extrapolation and compressive sensing

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Science china(Information Sciences) 2011年第10期54卷 2158-2169页

作者： QUAN YingHui ,ZHANG Lei,GUO Rui,xiNG MengDao & BAO Zheng national Key lab for radar signal processing,xidian university,xi’an 710071,china 1. national Key lab for radar signal processing Xidian University Xi’an 710071 China

Recent developing compressive sensing (CS) theory indicates that it is possible to obtain precise recovery of a sparse signal from very limited measurements,which provides a new way for data acquisition and signal processing as nature signals usually involve some degree of *** this paper,we present an algorithm for inversed synthetic aperture radar (ISAR) imaging with super resolution by combining CS and bandwidth extrapolation (BWE) *** ISAR imaging,the backscattering field of target is usually contributed by a few strong scattering centers,whose number is much less than that of image ***,CS is intuitively suitable for constructing super resolution ISAR *** to CS theory,the number of extracted dominating scatterers relies on the signal length,which indicates that if only limited data is available,it is difficult to generate dense ISAR image robustly by CS,and some signal components tend to *** soften this constraint,BWE is combined with CS imaging to increase the degree of freedom of signal while preserving its coherence.A refined CS-based formation for ISAR image-resolution enhancement is then *** real and simulated data experiments are performed to evaluate the proposed approach,and an example of using this technique demonstrates the enhanced image resolution in application of maneuvering target imaging.

关键词： inverse synthetic aperture radar (ISAR) compressive sensing (CS) bandwidth extrapolation (BWE) super resolution

Fast algorithm based on triplet Markov fields for unsupervised multi-class segmentation of SAR images

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Science china(Information Sciences) 2011年第7期54卷 1524-1533页

作者： WU Yan 1,WANG xin 1,xiAO Ping 2,GAN Lu 1,LIU ChunYan 1 & LI Ming 3 1 School of Electronics Engineering,xidian university,xi’an 710071,china 2 Shaanxi Bureau of Surveying & Mapping,xi’an 710054,china 3.national Key laboratory of radar signal processing,xidian university,xi’an 710071,china 1. School of Electronics Engineering Xidian University Xi’an 710071 China2. Shaanxi Bureau of Surveying & Mapping Xi’an 710054 China3. National Key Laboratory of Radar Signal Processing Xidian University Xi’an 710071 China

Non-Gaussian triplet Markov fields (TMF) model is suitable for dealing with multi-class segmentation of non-stationary and non-Gaussian synthetic aperture radar (SAR) *** the complexity of the model and algorithm,as well as the requirement of real-time,and robust and efficient processing of SAR images,a fast algorithm based on TMF for unsupervised multi-class segmentation of SAR images is proposed in this *** the speckle noise in SAR images,numerical characteristic,threshold selection and QuadTree decomposition criterion are researched *** the new method,a SAR image can quickly be mapped into an edge-based pixon-representation,which results in a coarse decomposition in smooth regions,and a fine decomposition in *** by combining TMF model with the pixon-representation of SAR image,a new potential energy function of TMF based on pixon-representation is ***,the segmentation is finished by Bayesian maximum posterior mode (MPM).The effectiveness of the fast TMF algorithm is demonstrated by applying it to simulated data and real SAR images.

关键词： pixon-representation of SAR image QuadTree decomposition new potential energy function triplet Markov fields multi-class segmentation

Target classification with low-resolution radar based on dispersion situations of eigenvalue spectra

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Science china(Information Sciences) 2010年第7期53卷 1446-1460页

作者： CHEN Feng, LIU HongWei, DU Lan & BAO Zheng national laboratory of radar signal processing, xidian university, xi’an 710071, china 1. national laboratory of radar signal processing Xidian University Xi’an 710071 China

Most low-resolution radar systems, especially ground surveillance radar systems, work at relatively low pulse repeat frequency (PRF) and with short time-on-target (TOT) (duration in scanning). Low PRF leads to Doppler ambiguity and short TOT results in low Doppler resolution, which poses a problem to target classification with low-resolution radar based on the jet engine modulation (JEM) characteristic of radar echo. From the pattern classification viewpoint, we propose a method of using dispersion situations of JEM eigenvalue spectra to categorize aeroplanes into three kinds, namely turbojet aircraft, prop aircraft and helicopter. We analyze the mathematical model of JEM echoes consisting of a series of line spectra and regard them as a sum of several series of harmonious waves. Classification features can be extracted based on the harmonious wave sum model. Some schemes for extracting features from echoes within or between pulses are proposed. Low-dimensional features are extracted to reduce computation burden. Our methods do not compensate for the fuselage echoes and are insensitive to the variation of fuselage Doppler. The feasibility of our methods is demonstrated by simulation experiment.

关键词： jet engine modulation (JEM) low-resolution radar low pulse repeat frequency (PRF) short time-on-target (TOT) target classification

ISAR imaging via sparse frequency-stepped chirp signal

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Science china(Information Sciences) 2012年第4期55卷 877-888页

作者： WANG Hongxian,LIANG Yi,xiNG MengDao & ZHANG ShouHong national Key laboratory of radar signal processing,xidian university,xi’an 710071,china 1. national Key laboratory of radar signal processing Xidian University Xi’an 710071 China

Frequency-stepped chirp signal can simplify the designation of radar ***,it has a shortcoming of Doppler ambiguity for high-speed moving ***,it is of great significance to study how to increase its equivalent pulse repeat *** back scattering field of the ISAR target has strong sparsity;that is to say,most energy is contributed merely by a few scattering ***,based on the theory of the sparse signal representation,a novel method for ISAR imaging via sparse frequency-stepped chirp signals is proposed by analyzing the signal model of the *** the proposed method,part of sub-pulses of the frequency-stepped chirp signal is randomly selected to transmit,and then the 2D high-resolution image of the target can be constructed by sparse signal *** the cost of computational resources,the method can effectively resolve the problem of Doppler ambiguity,decrease the sidelobes and obtain a super-resolution ***,the validity of the proposed approach is confirmed by the results of numerical simulations and real data.

关键词： inverse synthetic aperture radar (ISAR) radar imaging sparse signal representation frequency-stepped (FS)

A cumulant-based parameter estimation algorithm for near-field sources

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Progress in Natural Science:Materials International 2007年第8期17卷 900-905页

作者： Liang Junli~(1,2*) Yang Shuyuan~(1,2) Zhang Junying~3 (1.Institute of Acoustics,Chinese Academy of Sciences,Beijing 100080,china 2.Graduate School,Chinese Academy of Sciences,Beijing 100039,china 3.national laboratory of radar signal processing,xidian university,xi'an 710071,china) [a]Institute of Acoustics Chinese Academy of Sciences Beijing China [b]Graduate School Chinese Academy of Sciences Beijing China [c]national laboratary of radar signal processing Xidian University Xi'an China

To efficiently use the array aperture and avoid the complicated parameter pairing computation,this paper proposes a new cumulant-based algorithm for localizing near-field narrowband ***,this algorithm proposes a symmetric uniform linear ar- ray (ULA),and constructs three cumulant matrices by using the fourth-order cumulants of some properly chosen sensor outputs;second- ly,unlike the conventional parallel factor (PARAFAC) analysis models in data or subspace domain,it forms a three-way array (TWA) in the fourth-order cumulant domain using the three matrices,and analyzes the uniqueness of its low-rank decomposition;thirdly,it jointly estimates the frequency,the direction-of-arrival (DOA),and the range of each near-field source from the matrices via the low-rank de- composition of the *** simulation results are presented to validate the performance of our proposed method.

关键词： array signal processing localization cumulant parallel factor (PARAFAC) analysis three-way array (TWA)