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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

An approach to forward looking FMCW radar imaging based on two-dimensional Chirp-Z transform

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Science china(Information Sciences) 2010年第8期53卷 1653-1665页

作者： LIANG Yi 1 , WANG Hongxian 1 , ZHANG Long 1,2 & BAO Zheng 1 1 national key Lab of radar signal processing, xidian university, xi’an 710071, china 2 xi’an Polytechnic university, xi’an 710048, china 1. national key Lab of radar signal processing Xidian University Xi’an 710071 China2. Xi’an Polytechnic University Xi’an 710048 China

Airborne forward looking radar imaging, which is an important work mode of imaging radar system, has many advantages combined with frequency modulated continuous wave (FMCW) technology. This paper studies the configuration with one central antenna element for signal transmitting and other antenna elements for signal receiving. According to its imaging geometry, the analytical expression of the received signal for forward looking imaging radar based on FMCW is given. By performing the equivalent phase center principle, the received signal is equalized to the case of system configuration with antenna both for transmitting and receiving signals. The Doppler frequency shift effect, induced by the platform’s continuous motion while radar transmits and receives signals, is analyzed in detail and the approximate compensation method is shown. Based on this, a novel method for forward looking FMCW radar imaging is developed, which adopts two-dimensional Chirp-Z transform to implement scaling operation. Also the complete derivation process of the algorithm and the expression of each compensation factor are presented. The whole algorithm only includes FFT and complex multiplication, with interpolation free, and is easy to implement in reality. Simulation results verify the correctness of the analysis and the validity of the proposed algorithm.

关键词： forward looking radar imaging FMCW Chirp-Z transform

A novel algorithm of artificial immune system for high-dimensional function numerical optimization

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Progress in Natural Science:Materials International 2005年第5期15卷 463-471页

作者： DU Haifeng 1,2*, GONG Maoguo1, JIAO Licheng1 and LIU Ruochen1(1. Institute of Intelligent Information processing and key laboratory of radar signal processing, xidian university, xi'an 710071, china 2. School of Mechanical Engineering, xi'an Jiaotong university, xi'an 710049, china) Institute of Intelligent Information processing and key laboratory of radar signal processing Xidian University Xi''an 710071 China School of Mechanical Engineering Xi''an Jiaotong University Xi''an 710049 China

Based on the clonal selection theory and immune memory theory, a novel artificial immune system algorithm, immune memory clonal programming algorithm (IMCPA), is put forward. Using the theorem of Markov chain, it is proved that IMCPA is convergent. Compared with some other evolutionary programming algorithms (like Breeder genetic algorithm), IMCPA is shown to be an evolutionary strategy capable of solving complex machine learning tasks, like high-dimensional function optimization, which maintains the diversity of the population and avoids prematurity to some extent, and has a higher convergence speed.

关键词： clonal selection immune memory artificial immune system evolutionary algorithms Markov chain.

Performance improvement in multi-ship imaging for ScanSAR based on sparse representation

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Science china(Information Sciences) 2012年第8期55卷 1860-1875页

作者： XU Gang1,SHENG JiaLian1,ZHANG Lei1&xiNG MengDao1,2 1N ational key laboratory of radar signal processing,xidian university,xi'an 710071,china 2national key laboratory of Microwave Imaging,Institute of Electronics,Chinese Academy of Sciences,Beijing 100080,china 1. national key laboratory of radar signal processing Xidian University Xi’an 710071 China2. National Key Laboratory of Microwave Imaging Institute of Electronics Chinese Academy of Sciences Beijing 100080 China

There is always a compromise between unambiguous wide-swath imaging and high cross-range resolution owing to the constraint of minimum antenna area for conventional single-channel spaceborne synthetic aperture radar(SAR)*** overcome the inherent systemic limitation,multi-channel SAR imaging has been ***,this still suffers from various problems such as high system *** simplify the system structure,a novel algorithm for high resolution multi-ship ScanSAR imaging based on sparse representation is proposed in this paper,where the SAR imaging model is established via maximum a posterior estimation by utilizing the sparsity prior of multi-ship *** the scheme,a wide swath is generated in the ScanSAR mode by continuously switching the radar footprint between ***,high crossrange resolution is realized from sparse subapertures by exploiting the sparsity feature of multi-ship *** particular,the SAR observation operator is constructed approximately as the inverse of conventional SAR imaging and then high resolution SAR imaging including range cell migration compensation is achieved by solving the *** with multi-channel SAR imaging,the system complexity is effectively reduced in the ScanSAR *** addition,enhancement of the cross-range resolution is realized by incorporating the sparsity prior with sparse *** a result,the amount of data is effectively *** based on measured data have been carried out to confirm the effectiveness and validity of the proposed algorithm.

关键词： synthetic aperture radar(SAR) ScanSAR wide-swath sparse representation high resolution

Parameter estimation of moving targets in the SAR system with a low PRF sampling rate

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Science china(Information Sciences) 2012年第2期55卷 337-347页

作者： LIU Yan,WU QiSong,SUN GuangCai,xiNG MengDao,LIU BaoChang & BAO Zhengkey laboratory for radar signal processing,xidian university,xi’an 710071,china 1. key laboratory for radar signal processing Xidian University Xi’an 710071 China

In the synthetic aperture radar(SAR)system with low pulse repetition frequency(PRF)sampling,it is difficult for the motion parameters estimation of the moving targets,because of the Doppler spectrum ambiguity and Doppler centroid frequency ambiguity of the echo *** that moving targets are sparsely distributed in the observed scene,their positions and velocities can be reconstructed by using the compressed sensing(CS)*** this paper,the range-walk correction are implemented by the keystone transform and the sparse range-walk correction(SRWC),then the CS technique is proposed to reconstruct motion parameters by processing the azimuth signals of the moving *** using the simulated and real data are performed,and the results confirm the validity of the proposed method.

关键词： synthetic aperture radar(SAR) moving target motion parameter estimation keystone transform sparse range-walk correction(SRWC) compressed sensing(CS)

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

A new family of windows——convolution windows and their applications

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Science china(Technological Sciences) 2005年第4期48卷 468-480页

作者： ZHANG Jieqiu1,2, LIANG Changhong1 & CHEN Yanpu3 1. Department of Applied Math. & Phys., College of Science, Airforce Engineering university, xi’an 710051, china 2. national key laboratory of Antennas and Microwave Technology, xidian university, xi’an 710071, china 3. Computer Center, xi’an Communication College, xi’an 710106, china 1. Department of Applied Math. & Phys. College of Science Airforce Engineering University 710051 Xi’an China 2. national key laboratory of Antennas and Microwave Technology Xidian University 710071 Xi’an China 3. Computer Center Xi’an Communication College 710106 Xi’an China

A new family of windows is constructed by convolutions via a few rectangular windows with same time width and is thus referred to as convolution windows. The expressions of the second-order up to the eighth-order convolution windows in both the time and frequency domains are derived. Their applications in high accuracy harmonic analysis of periodic signals are investigated. Comparisons between the proposed windows and some known windows with the same width shows that, when the synchronous deviation of data sampling is slight, the proposed ones have the least effect of spectral leakage. Therefore, the new windows are well suited for high accuracy harmonic analysis and parameter estimation for periodic signals. The error analysis and computer simulations show that the estimation errors, corresponding to frequency, amplitude and phase of every harmonic component of a signal, are proportional to the pth power of the relative frequency deviation in case of the pth-order convolution window is applied to windowing signal of approximately p cycles. By introducing real time adjustment in sampling interval, the proposed algorithm can adaptively trace signal frequency and lead to less sampling synchronous deviation. The proposed approach has the advantages of easy implementation and high measure precision and can be used in harmonic analysis of quasi-periodic signals whose fundamental frequency drifts slowly with time.

关键词： signal processing harmonic analysis window function convolution window synchronous error spoctral leakage

维普期刊数据库

SAR image despeckling based on edge detection and nonsubsampled second generation bandelets

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Journal of Systems Engineering and Electronics 2009年第3期20卷 519-526页

作者： Zhang Wenge~(1,2),Liu Fang~(1,2),Jiao Licheng~(2,3)& Gao xinbo~(2,3) 1.School of Computer Science and Technology,xidian Univ.,xi’an 710071,P.R.china 2.key Lab.of Intelligent Perception and Image Understanding of Ministry of Education of china,xi’an 710071,P.R.china 3.Inst,of Intelligent Information processing,xidian Univ.,xi’an 710071,P.R.china School of Computer Science and Technology Xidian Univ. Xi'an 710071 P. R. China key Lab. of Intelligent Perception and Image Understanding of Ministry of Education of china Xi'an 710071 P. R. China key Lab. of Intelligent Perception and Image Understanding of Ministry of Education of china Xi'an 710071 P. R. China Inst. of Intelligent Information processing Xidian Univ. Xi'an 710071 P. R. China

To preserve the sharp features and details of the synthetic aperture radar （SAR） image effectively when despeckling, a despeckling algorithm with edge detection in nonsubsampled second generation bandelet transform （NSBT） domain is proposed. First, the Canny operator is utilized to detect and remove edges from the SAR image. Then the NSBT which has an optimal approximation to the edges of images and a hard thresholding rule are used to approximate the details while despeckling the edge-removed image. Finally, the removed edges are added to the reconstructed image. As the edges axe detected and protected, and the NSBT is used, the proposed algorithm reaches the state-of-the-art effect which realizes both despeckling and preserving edges and details simultaneously. Experimental results show that both the subjective visual effect and the mainly objective performance indexes of the proposed algorithm outperform that of both Bayesian wavelet shrinkage with edge detection and Bayesian least square-Gaussian scale mixture （BLS-GSM）.

关键词： computer image processing synthetic aperture radar speckle edge detection nonsubsampled second generation bandelet transform Canny operator threshold shrinkage.

维普期刊数据库

Asynchronous cooperative communication systems:A survey on signal designs

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Science china(Information Sciences) 2011年第8期54卷 1547-1561页

作者： WANG HuiMing 1,2 & xiA xiangGen 3 1 School of Electronic and Information Engineering, xi’an Jiaotong university, xi’an 710049,china 2 State key laboratory of Integrated Services Networks, xidian university,xi’an 710049, china 3 Department of Electrical and Computer Engineering,university of Delaware,Newark,DE 19716,USA 1. School of Electronic and Information Engineering Xi’an Jiaotong University Xi’an 710049 China2. State Key Laboratory of Integrated Services Networks Xidian University Xi’an 710049 China3. Department of Electrical and Computer Engineering University of Delaware Newark DE 19716 USA

Cooperative communications is a promising technique for future high speed wireless *** systems may be formulated as virtual multi-input multi-output (MIMO) systems where spatial/cooperetive diversity is a key advantage. However,different from MIMO systems,one of the major chal- lenges for cooperative communications systems is that the cooperative transmissions in cooperative systems may be neither time nor frequency synchronized,since the transmissions are from multiple cooperative nodes at different *** existing signal designs for co-located MIMO systems may not be able to collect the cooperative diversity in cooperative communications *** paper gives an overview of recent research efforts on combating the time and frequency asynchronism of the cooperative communication *** focus on the signal designs (or space-time codings/modulations) to achieve full cooperative diversity,and summarize some of the resent distributed space-timing coding and space-frequency coding techniques to combat timing errors and frequency offsets,and in the meantime to achieve full cooperative diversity,in both one-way and two-way cooperative networks.

关键词： cooperative communications time and frequency offsets space-time coding space-frequency codes full cooperative diversity linear receiver