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Study On Ground Moving Target Information Acquisition Based On Multi-channel SAR System

Posted on:2013-01-17Degree:DoctorType:Dissertation
Country:ChinaCandidate:M XiaFull Text:PDF
GTID:1228330395455452Subject:Communication and Information System
Abstract/Summary:PDF Full Text Request
Due to its all-weather, all day/night and long range, radar imaging technique canenhance radar’s information acquisition capability greatly, thus exhibits great value inboth civilian and military applications. It provides strange change for targetidentification. At the same time, it is also a landmark for development of radartechniques. Ground Moving Target Indication (GMTI) is a necessary function of theSAR system, especially in military SAR application and signal processing. Since two ormore antennas (channels) can provide more degrees of freedom, multi-channelalong-track SAR has powerful ability to suppress clutter and distinguish targets movingon land or water from surface clutters over a large area. Thus it has been usedextensively in air-to-ground surveillance and reconnaissance. The primary contributionsof this dissertation, which is devoted to the above aspects, are summarized as below:1. In order to obtain a number of horizontal and vertical phase center information,a novel spaceborne SAR-GMTI with three-channel is proposed, which is based onslant-placed baseline and displaced phase center antenna. The compensation functionfor equivalent phase center with slant-placed baseline is analyzed. New constraint of thesystem and analysis of blind velocity relative to slant-placed antenna are also given.2. Aiming at channel errors in multi-channel SAR-GMTI, the influence of errorson clutter suppression and moving target detection is analyzed. A novel method ofamplitude and phase errors calculation is presented based on the PN code. It transmits aPN code from calibration source, and use decorrelation to get amplitude and phaseerrors in each receiving channel. Finally, Kalman filter is applied to eliminate the effectof noise. Compared with the traditional Fourier transform, the proposed method hasbetter effects in the case of low SNR.3. Multi-channel SAR-GMTI has a good character of clutter cancellation, it is notonly able to detect slow moving targets, but also on the target parameter estimation andpositioning processing. Therefore, the errors of multi-channel SAR-GMTI wereanalyzed in detail. Based on the multiple-input multiple-output synthetic aperture radar,an approach with dual-satellites dual frequency for detection, imaging and parametersestimation of the ground fast moving target is proposed. General two-order keystonetransform is employed to eliminate range migration, modified discrete chirp-Fouriertransform and least waveform entropy are applied to Doppler parameters estimation. Forthe Doppler ambiguity of fast moving target, velocity can be obtained by search ofdifferent frequency data. 4. Different from the target of uniform motion, moving target makes cubic phasewhen it has acceleration. It affects clutter suppression and Doppler parameter estimation,so a parameter estimation method based on cubic phase compensation is proposed.Based on the analysis of signal model, phase compensation is achieved by dechirp andone-dimensional search in time-chirp distribution. And velocity estimation is proposedbased on the cubic phase compensation.5. A bistatic SAR-GMTI system which is the combination of geosynchronoussatellite and airborne dual-channel SAR is researched. According to the analysis ofmoving target signal characteristics, new compensation function and matched filter areconstructed by FrFT. The problem of imaging affected by time and frequencyasynchronization is analyzed in detail. Based on the signal geometry, motion errorinfluence on parameters of moving target is deduced, and the correspondingcompensation factors are also proposed. Especially for the case when relief and squintcannot be ignored, offset error compensation and an effective compensation methodwere obtained.
Keywords/Search Tags:Synthetic Aperture Radar (SAR), ground moving target indication(GMTI), multi-channel, displaced phase center antenna, amplitude and phaseerrors, motion error, phase compensation, parameter estimation, keystonetransformation, bistatic
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