Research On Waveform Design,High Resolution Imaging And Micro-Motion Parameters Estimation Technology Of MIMO SAR

Synthetic aperture radar(SAR)has been widely used as a frontier technology in the field of microwave remote sensing,and it plays an important role in the national economy and military reconnaissance.The traditional single channel SAR constraints by the system,there are serious limitations on the performance of imaging and estimation of micromotion parameters.The multichannel SAR with single input and multiple output can ease constraints,but the freedom degree of system is equal to the number of receiving antennas,therefore the multichannel SAR performance is restricted by the size and load limit of the radar platform.Multiple input multiple output(MIMO)SAR can obtain much more equivalent observation channels than the number of actual antennas through the operation of multi antenna transceiver,which brings new opportunities and challenges.For MIMO SAR,this paper focus on its waveform design,high resolution imaging and micro-motion parameters estimation technology research,which can provide some constructive reference for understanding,design and application of MIMO SAR.The main research work includes the following aspects:According to the relevant waveform characteristics demand for MIMO SAR high resolution imaging,such as high time bandwidth product,low PAPR,good Doppler tolerance.A new waveform design criteria based on the MIMO SAR generalized ambiguity function(GAF)is proposed.For the sub-chirp combination waveform,two waveform design methods based on MIMO SAR GAF are proposed.The first one is the waveform design method using genetic algorithm,and the other one is the waveform design method using chaotic mapping.Compared with the method in the literature,the methods presented in this paper are more operational and the designed waveforms perform better in MIMO SAR imaging.For the azimuth ambiguity problem caused by along track MIMO SAR nonuniform azimuth sampling,this paper establishes the signal model of MIMO SAR azimuth nonuniform sampling,then introduces three kinds of conventional spectrum reconstruction methods for nonuniform sampling: filter band algorithm,the space-time adaptive processing algorithm and periodic nonuniform sampling algorithm(PNUA).The internal relation and equivalence of the three methods is analyzed.According to big computation load shortcoming of the PNUA reconstruction method,two fast methods are proposed,which are the method based on non-uniform fast Fourier transform(NUFFT)and the method based on basis mismatch.Through analyzing the performance of the two fast methods,we can draw the conclusion that the method based on NUFFT has accurate calculation but still needs large amount of calculation,and the method based on basis mismatch greatly reduces amount of calculation,but applies only to sampling nonuniform degree is low.Finally,the method selection strategy under different application conditions is put forward.Accoding to the opportunity of MIMO SAR range resolution enhancement,based on the wave number shift principle,two MIMO SAR schemes for high range resolution enhancement are proposed in this paper.Firstly,according to the cross track multi-carrier MIMO SAR,combined with the multi band echo data synthesis from the same equivalent phase center and spectrum shifting from the different equivalent phase center,high bandwidth signal is obtained for achieving high range resolution.Secondly,for cross track MIMO SAR with the same carrier frequency,the MIMO SAR range super-resolution method based on state space algorithm is proposed when the spectral shifting exceeds the signal bandwidth.According to the application requirements of MIMO SAR estimation of micromotion parameters,the micro-Doppler effect MIMO SAR of two kinds of micro-motion,three-dimensional vibration and three-dimensional rotation,is analyzed.Since the microDoppler frequency form of three-dimensional rotation is complex,it brought problem in realizing rotation parameter estimation.For three-dimensional rotation,the derivation of approximate micro-Doppler formula with a single cosine function is given.The MIMO SAR micro-motion parameter estimation method is presented,and the influence of the MIMO SAR configuration for micro-motion parameter estimation is discussed in the simulation session.