Research On High-orbit SAR Moving Target Detection And Imaging Technology Based On Multi-channel Processing

Large-scale and long-term regional monitoring puts forward higher requirements for spaceborne synthetic aperture radar.The high-orbit SAR is characterized by its wide beam coverage,geographical constraints,and all-weather working all day.The detection of moving targets has unique advantages and broad application prospects.Based on the high-altitude SAR platform,this thesis develops ground(sea surface)moving target detection and imaging technology based on multi-channel processing.The main research work is as follows:1.Aiming at the problem that the ground moving target is easy to cause the distance and the Doppler movement of the echo,the high-orbit SAR moving target detection and imaging technology combined with DPCA and generalized keystone transform is proposed.Firstly,the signals received by the two channels are pulse-compressed,DPCA processing is performed in the data Doppler domain to suppress the clutter,then the moving target detection and parameter estimation are performed,and the generalized Keystone transform is performed according to the estimated parameters to correct the distance movement caused by the target motion.And Doppler walks,and finally through the Fourier transform for coherent accumulation to complete the moving target imaging.The point target imaging simulation verifies the effectiveness of the proposed method.2.Aiming at the slow moving target of the sea surface,a sea surface ship target detection and imaging technology based on high-rail platform is proposed.Firstly,starting from the high-orbit SAR moving target echo modeling,the conventional echo processing of the echo data received by the two channels is performed to complete the image registration and channel equalization.On this basis,the clutter suppression is performed and the double-threshold constant false alarm detection is performed.The moving target is estimated;the distance velocity of the target is estimated by the interference phase,and the azimuth velocity of the target is estimated by the minimum entropy method,and finally the moving target is re-imaged by the azimuth velocity.Point target and scene imaging simulations verify the effectiveness of the proposed method.3.Aiming at the problem that the distance of the moving target may exceed the maximum detectable speed of the system,the parameter estimation will be blurred.A method of using dual frequency and multi-channel unequal spacing to solve the speed blur is proposed.For the dual-frequency solution speed blur,the equivalent carrier frequency is used to compensate the constraint of the maximum detectable speed,thereby improving the maximum detectable speed of the original system and eliminating the speed blur.At the same time,a method of unequal spacing solution speed blur is designed.By setting the spacing of multiple channels reasonably,two fuzzy speed sets are obtained,and the unblurred speed is obtained by registration comparison.The moving target parameter estimation experiment verifies the effectiveness of the proposed method.