Research On Imaging And Moving Target Detection Technology Of Bistatic SAR With Geosynchronous Illuminator

With Geosynchronous(GEO)synthetic aperture radar(SAR)as the illuminator,and airborne platform or Low-earth-orbit(LEO)SAR platform as the receiver,GEO bistatic SAR(GEO Bi SAR)is a new kind of bistatic SAR system,which has the advantages of wide beam coverage,flexible bistatic or multistatic configuration and strong anti-detection capability of receiver,etc.These characteristics make GEO Bi SAR highly valuable in both military and civil applications.Imaging performance and bistatic geometry configuration,echo characteristics,imaging algorithms are the basic and critical elements for GEO Bi SAR imaging and moving target detection.Focusing on the above researches,this dissertation presents theory analysis,method research and simulation verification.The main contents are as follows1.The relation between imaging performance and GEO Bi SAR observation geometry is established.After that,the geometry design method based on genetic algorithm for GEO Bi SAR is proposed.The proper GEO Bi SAR geometry with optimal imaging performance can be automatically generated by the multiobjective optimization method,which lays the theoretical foundation for GEO Bi SAR high resolution imaging.2.The two-step nonlinear chirp scaling(NLCS)imaging method is proposed.The total Doppler bandwidth of the imaging scene is decreased through Doppler centroid equalization by the first step NLCS processing,thus the number of required receiving channels for unambiguous reconstruction is reduced.The second step NLCS processing is applied to equalize the high-order space variant Doppler parameters.With the proposed frequency-domain imaging method,the problem of 2-D space variance and Doppler ambiguities in GEO spaceborne-airborne bistatic SAR has been solved.3.The weighted fast factorized backprojection imaging algorithm is proposed.The ambiguities introduced by the non-uniform sampling of the multichannel in azimuth can be suppressed by multichannel weighting.This method can achieve accurate time-domain focusing for GEO spaceborne-airborne bistatic SAR with high efficiency.4.The unambiguous imaging method based on sparse recovery and multireceiving is proposed.By using the multireceiving channels information in each iterative process of the compressed sensing recovery method,the unambiguous image of GEO-LEO bistatic SAR can be obtained where the number of required receiving channels can be greatly reduced.5.The simultaneous moving target detection and imaging method is proposed.The problem of accurate separation of moving target and clutter,precise estimation of moving target velocity is solved by the joint optimization method consisting of alternating direction method of multipliers and particle swarm optimization method.The detection and accurate focusing of moving target for GEO spaceborne-airborne bistatic SAR can be achieved.The above models and methods are validated by theory analysis and simulation experiments.The simulation results verify that the proposed methods can handle the problems of ambiguous imaging and moving target detection under the circumstances of 2-D space variance and Doppler ambiguities,which can achieve efficient and accurate imaging for GEO Bi SAR.