| Ground Moving Target Indication(GMTI) using Spacebome Radar(SBR) gives the opportunity for large scale surveillance,spying,and target tracking,position.It is specially valuable for military application.Utilizing the space domain sampling character of multi-channel radar and distributed radar for GMTI is attractive to researchers.Since SBR GMTI system is a multilevel and complex large-scale system concerning broad technology,many challenges about signal processing and system design will be encountered.It is significant and valuable to study it.With the spaceborne GMTI radar as the background,this dissertation focuses on four crucial techniques:the GMTI signal modeling & simulation,GMTI signal processing,distributed SAR-GMTI system performance analysis,distributed SAR-GMTI optimum formation design.In the second chapter,SBR GMTI signal modeling & simulation are researched. Based on the small facet model and the scatter characteristic of the rough terrain,3-D ground scene clutter model is established.The received signal expression of clutter and moving target are formulated.The moving target imaging character is tested.The simulation method of receive signal and GMTI procession flow are discussed comprehensively,and an integrated distributed spaceborne SAR-GMTI simulation software is established.The software will be usefull for the deeper research in GMTI procession algorithms and optimum system design.In the third chapter,SBR GMTI signal processing algorithms for Short coherent pulses integrated(CPI) multi-channel Pulse Doppler(PD) mode,long CPI multichannel SAR imaging mode and distributed SAR-GMTI are researched separately.The ground clutter characteristic of bistatic spaceborne GMTI radar in PD mode is analyzed. The clutter rank is forecasted with considering the bistatic style,beam synchronization, earth rotation,and the directional array pattern.Several nonstationary clutter suppression algorithms dependent on range are researched,and cascade signal processing is used to enhance the efficiency and improve the performance.The natural difference of the STAP signal models for PD and SAR modes is analyzed,and the effects of CPI on clutter statistical character and power spectrum are discovered. Several distributed SAR-GMTI algorithms,such as ATI,two kinds of adaptive filters in image domain,are compared essentially.Proper modification is made to ATI.In the fourth chapter,the detection performance of the distributed spaceborne SAR-GMTI is analyzed.Instead of beginning the research from the phase errors models as the traditional way,we start the research from the more essential matter.A comprehensive expression of the correlation coefficient with time and frequency synchronization errors is given.The influence of synchronization error and some other system parameters are discussed.System parameters requirements for two kinds of interferometric systems,InSAR and GMTI,are compared.This will give powerful theoretical supports for distributed spaceborne SAR-GMTI system design.In the fifth chapter,optimal formation design for SAR-GMTI is studied.Based on the research of signal processing and detection performance analysis,the joint criterion, which combines the detectable velocity percent with the effective system cycle is presented.GMTI performances of some classical formations,such as the Cartwheel, Pendulum,SAR-Train and so on,are evaluated by it.For along-track formation,the optimum baseline configuration is obtained based on the orthogonal signal theory.It has some advantages than Uniform Linear Arrays and Minimum Redundancy Arrays.For 3-D formation,the mathematic model of the optimal object is drawn,and the searching range is established by the requirement for the radar signal detection and the knowledge of the orbit control.As a result,an optimum 3-D formation consisting of 3 small satellites is found through genetic algorithm.
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