Study On Moving Target Imaging In Multichannel Synthetic Aperture Radar

Azimuth multichannel technology is one of the most important technical way to achieve a high resolution and wide swath(HRWS)with spaceborne synthetic aperture radar(SAR).The traditional azimuth multichannel reconstruction and imaging approach are unable to process the echo of the moving target due to the obvious difference between the moving target and the fixed target in the slant range history and Doppler history.In order to resolve this problem,this thesis focuses on the imaging approach of the moving targets in azimuth multichannel beam steering mode,squint mode and bistatic mode.1?The azimuth multichannel reconstruction method of the moving target based on azimuth de-ramping is proposed for azimuth beam steering mode,which solves the Doppler spectral aliasing caused by azimuth beam steering through azimuth de-ramping and uses the spectral energy distribution of the moving target to estimate the slant range velocity of the moving target.Meanwhile,an improved azimuth multichannel reconstruction filter is used to solve azimuth non-uniform sampling problem of the moving target.Finally,the simulation results on point targets validate the proposed approach.2?The moving target imaging approach based on two-dimensional frequency domain de-ramp processing method in azimuth multichannel squint mode is proposed to address the problem that the additional Doppler bandwidth due to squint angle affects the azimuth multichannel reconstruction of moving targets.The method solves the Doppler aliasing problem caused by the additional bandwidth of squinted angle through a two-dimensional spectral de-ramping process,compensates for the azimuth multichannel imbalance caused by the moving target velocity through a improve azimuth multichannel reconstruction matrix,and analyses the clutter suppression capability in the case of channel redundancy.Finally,the simulation results on point targets validate the proposed approach.3 ? According to echo signal model of the moving target in the GEO(Geosynchronous)spaceborne–airborne bistatic synthetic aperture radar,an imaging approach of the moving target is proposed based on azimuth nonlinear chirp scaling in GEO spaceborne–airborne bistatic synthetic aperture radar mode,which solves the range offset deviation between channels by the space-varying range cell migration correction,and the azimuth nonlinear chirp scaling processing is used to avoid Doppler spectrum aliasing.Meanwhile,the equivalent single-channel echo is obtained by the improved azimuth multichannel reconstruction matrix.According to the echo characteristics of the moving target,the imaging approach of a large scene including moving targets is presented.Finally,the simulation results on point targets and distributed targets validate the proposed approach.