Research On Multi-channel SAR-GMTI Method Based On Compressed Sensing

Synthetic Aperture Radar(SAR)system has the abilities of wide-area and far-distance observation in all-day and all-weather condition.With the deep research on SAR system,Ground Moving Target Indication(GMTI)has a promising application prospects in military,civilization and other fields.In recent years,with the development of radar technology,system with single antenna has stepped into the age of multi-dimensionality observation with the systems of multi-antenna.This improvement would greatly improve the performance of the traditional radar systems and the ability of information sensing.However,in the background of multi-dimensionality observation,the huge amount of data that needs to be storaged and transmitted caused a heavy burden for SAR system.This thesis is concerned with the GMTI method based on Compressed Sensing(CS)for multi-antenna SAR system.The main contributions of this thesis are as follows:Due to the reconstruction error between channels and the sampling rate is limited by the sparsity level of the echo signal,the performance of clutter suppression decreases.Based on the above issue,the Distributed Compressive Sensing(DCS)theory is introduced into the research of radar moving target indication system with the features that the echo signals between channels is highly correlated.The echo signals need to be vectorized after sparse sampling.The vectorized signal is reconstructed by constructing a joint sparse observation matrix.First of all,the joint sparse reconstruction method can achieve the separation of the common part and the new part of the echo signals between different channels without the inter-channel clutter suppression.And then,the minimum sparsity level required by the joint processing is much smaller than that required by the basic CS method.When in the situation that the data rate is extremely low,the DCS processing method still achieve the moving target indication well.Results of simulation and experimental data show that this method can effectively achieve the ground motion target indication with low data rate,even in the situation that the SNR is extremely low.For the problem of time-consuming in reconstruction algorithms when solving large scale problem,an accelerated IHT reconstruction algorithm is introduced.By constructing the multi-channel moving target echo signal model,the phase compensation and imageregistration of the multi-channel target signal need to be done after sparse reconstruction.Firstly,clutter suppression is achieved by using Displaced Phase Center Antenna(DPCA)technology,Along Track Interferometric(ATI)technology and the combination of the two methods respectively.Secondly,the Go Dec algorithm,the sparse and low rank joint moving target indication method is introduced.This method can separate the clutter with low rank characteristic and the moving target with sparse characteristic effectively,even in the condition with noise.After reconstructing in azimuth,the target signal SAR imaging is achieved.The performance of the clutter suppression methods is testified by simulations and measured data.Finally,the influences of moving target on SAR imaging are discussed and the estimation of along-track velocity is achieved.