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LFM Radar Source Passive Localization Algorithm Based on range migration

Journal of Beijing Institute of Technology 2024年第2期33卷 130-140页

作者： Dandan Li Deyi Wang Hao Huan Beijing Key Laboratory of Fractional Signals and Systems School of Information and ElectronicsBeijing Institute of TechnologyBeijing 100081China Beijing Aerospace Automatic Control Institute Beijing 100854China

Traditional single-satellite passive localization algorithms are influenced by frequency and angle measurement accuracies,resulting in error estimation of emitter position on the order of kilometers.Subsequently,a single-satellite localization algorithm based on passive synthetic aper-ture(PSA)was introduced,enabling high-precision positioning.However,its estimation of azimuth and range distance is considerably affected by the residual frequency offset(RFO)of uncoopera-tive system transceivers.Furthermore,it requires data containing a satellite flying over the radia-tion source for RFO search.After estimating the RFO,an accurate estimation of azimuth and range distance can be carried out,which is difficult to achieve in practical situations.An LFM radar source passive localization algorithm based on range migration is proposed to address the dif-ficulty in estimating frequency offset.The algorithm first provides a rough estimate of the pulse repetition time(PRT).It processes intercepted signals through range compression,range interpola-tion,and polynomial fitting to obtain range migration observations.Subsequently,it uses the changing information of range migration and an accurate PRT to formulate a system of nonlinear equations,obtaining the emitter position and a more accurate PRT through a two-step localization algorithm.Frequency offset only induces a fixed offset in range migration,which does not affect the changing information.This algorithm can also achieve high-precision localization in squint scenar-ios.Finally,the effectiveness of this algorithm is verified through simulations.

关键词： passive localization range migration residual frequency offset

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High Accuracy Velocity Measurement Based on Keystone Transform Using Entropy Minimization

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Chinese Journal of Electronics 2016年第4期25卷 774-778页

作者： DAI Zuoning ZHANG Xinggan FANG Hui BAI Yechao School of Electronic Science and Engineering Nanjing University State Key Laboratory of Millimeter Waves

Velocity measurement is a basic task of radars.The target velocity is usually estimated according to the Doppler frequency shift.While traditional Doppler methods are unsuitable for high-speed targets,since the serious range migration between adjacent echoes causes phase wrapping.The serious range migration also interferes the coherent integration to improve the accuracy of the velocity estimation.A velocity measurement method based on Keystone transform using entropy minimization is studied to solve this problem.This method applies Keystone transform to the echo to calculate the ambiguity degree with the help of entropy minimization.The proposed algorithm estimates the ambiguity degree with no error at a wider range of SNR than the traditional method.The ambiguous Doppler frequency is obtained according to the slow time.Theoretical analyses and simulations show that this method has very high precision.

关键词： Entropy minimization Keystone transform range migration Velocity measurement

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Azimuth space-variant properties of BiSAR with nonequal velocities

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Journal of Systems Engineering and Electronics 2008年第5期19卷 919-922页

作者： Yang Yonghong Pi Yiming School of Electronic Engineering Univ. of Electronic Science and Technology of China Chengdu 610054 P. R. China

Bistatic SAR possesses characteristic of the azimuth space-variant when the velocities of transmitter and receiver are not equal. The geometric model of BiSAR with the parallel trajectories and the nonequal platform velocities is presented. Analyzing the motion relationship of transmitter and receiver, the formula of azimuth spacevariant is derived in time domain. Via Taylor polynomial expansions, the azimuth space-variant is factorized by four terms： zero-order, first-order, second-order, and third-order term. And, their impacts on impulse response are illuminated. Some characteristics about azimuth space-variant of airborne BiSAR case are exhibited by simulation experiments, and these simulated results are coincident with the formulae of azimuth space-variant.

关键词： bistatic SAR range migration azimuth space-variant imaging formation algorithm.

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A Novel Parameter Estimation Method for Maneuvering Target Based on DCF-RFRFT

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Chinese Journal of Electronics 2017年第6期26卷 1315-1318页

作者： YANG Gang TIAN Jing WU Shuang CUI Wei WU Siliang School of Information and Electronics Beijing Institute of Technology Beijing Institute of Remote Sensing Equipment

To resolve the range migration and Doppler frequency spread, a new parameter estimation method, namely Dual-carrier frequency-Radon fractional Fourier transform(DCF-RFRFT), is proposed based on the dual-carrier frequency radar data. In this method,dual-carrier frequency radar data is constructed in the range frequency domain and a new signal is constructed by multiplying one with the complex conjugate of the other.Radon fractional Fourier transform(RFRFT) is performed to obtain the estimates of velocity and acceleration. This method does not need any prior-knowledge of targets and can resolve the Doppler ambiguity problem. The simulation results demonstrate the effectiveness of the proposed algorithm.

关键词： range migration Doppler frequency spread Radon fractional fourier transform(RFRFT)

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A Novel Long-Time Coherent Integration Method for Moving Target Detection

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Journal of Beijing Institute of Technology 2021年第4期30卷 340-351页

作者： Xia Bai Yan Wang Juan Zhao Ran Tao School of Information and Electronics Beijing Institute of TechnologyBeijing 100081China

Long-time coherent integration(LTCI)can remarkably improve the detection ability of radar for moving target.To increase the processing efficiency,this paper proposes a novel LTCI method based on segment time reversing transform(STRT)and chirp z-transform(CZT).In this method,STRT operation is first presented to estimate the Doppler ambiguity factor,and keystone transform(KT)is used to correct the whole range migration(RM).Then,CZT and non-uniform fast Fourier transform(NUFFT)are used to estimate the parameters as well as correct the second and third order Doppler frequency migration(DFM).Compared with the existing methods,the proposed method can achieve RM correction and DFM correction without repetitive operation.The effectiveness of the proposed method is validated by both simulated and real data.

关键词： long-time coherent integration range migration Doppler frequency migration

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PRF-ambiguity resolution for SAR by contrast minimization in range-Doppler domain

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Frontiers of Electrical and Electronic Engineering in China 2007年第3期2卷 302-306页

作者： YU Mingcheng XU Jia PENG Yingning Department of Electronic Engineering Tsinghua UniversityBeijing 100084China

An algorithm was developed to accurately estimate the Doppler centroid,which is needed for high-quality synthetic aperture radar(SAR)image formation by resolving the SAR pulse repetition frequency(PRF)ambiguity.The algorithm uses the SAR range migration to resolve the PRF-ambiguity by searching for a PRF-ambiguity number that minimizes the intensity contrast in the range-Doppler domain.Experimental results show that the approach,compared with traditional methods for resolving the SAR PRF ambiguity,is more suitable for both high contrast scenes such as urban areas and low contrast scenes such as mountains.Moreover,the approach is more computationally efficient for there are no time-consuming correlations or fast Fourier transform(FFT)operations needed in the range-Doppler domain and only part of the range cells are used in the calculation.

关键词： SAR PRF-ambiguity resolution range migration range-Doppler domain scene contrast

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