Research On High Resolution 3D Imaging Methods Of Spaceborne Airborne Bistatic Linear Array SAR

Spaceborne Airborne-Bistatic Linear Array SAR(SA-BiLASAR)is a new concept and a new system SAR that combines the advantages of Spaceborne Airborne-Bistatic SAR(SA-BiSAR)and Linear Array SAR(LASAR)and has important application value.In mechanism,SA-BiLASAR is capable of high-resolution three-dimensional(3D)imaging from multiple perspectives,such as forward and backward view,forward view and side view.It breaks through the limitation of traditional side view SAR imaging mode and can realize 3D imaging of observation targets.The emerging theory of compressed sensing indicates that if the original signal is sparse or compressible,the original signal can be recovered by measuring signals far lower than the traditional Nyquist sampling rat.And the sparser the original signal is,the less observational data is needed.Therefore,in view of the shortcomings of the traditional imaging theory and methods in the new system of SA-BiLASAR imaging,SA-BiLASAR 3D imaging can be well combined with the sparse signal processing theory.In the airborne receiving system,only the sparse linear array antenna is used to receive the echo,and then the sparse signal reconstruction method is used to achieve the high-precision 3D imaging of the sparse target.This paper mainly introduces a new system of SAR-SA-BiLASAR,and studies the high precision 3D imaging method of SA-BiLASAR.The main research contents and innovations of this paper are as follows:1.The basic theory of compressed sensing and SA-BiLASAR 3D imaging are briefly described.Firstly,the basic theory of compressed sensing is introduced.At the same time,the geometric model of linear array 3D SAR and the echo measurement model based on compressed sensing are introduced.Secondly,on the basis of the above basic theories,the geometric model and linear echo measurement model of the new 3D imaging SA-BiLASAR system combining SA-BiSAR and LASAR were constructed,and the classical theoretical resolution of SA-BiLASAR system was analyzed.Finally,two traditional SAR imaging algorithms are introduced for SA-BiLASAR 3D imaging,namely,3D range doppler(RD)algorithm and 3D backward projection(BP)algorithm.2.SA-BiLASAR 3D high resolution sparse imaging algorithm is studied.Firstly,the principles and processes of several common algorithms of sparse imaging algorithm are briefly described.Combined with the SA-BiLASAR imaging model,three algorithms that are suitable for its 3D high resolution sparse imaging are studied,including the orthogonal matching(OMP)algorithm based on greedy tracking algorithms,Sparsity Bayesian Recovery via Iterative Minimum(SBRIM)algorithm and Approximate Message Passing(AMP)algorithm based on Bayesian reconstruction algorithm class.Then,through different simulation experimental models and simulation experimental results,the performance of the above algorithms is compared,analyzed and verified.In addition,aiming at the problems of the above sparse imaging algorithm such as the spatial distortion of imaging geometry in the 3D imaging of equidistant slices of SA-BiLASAR,combined with the geometric model of SA-BiLASAR and the 3D imaging principle of equidistant slices,a geometric distortion correction method suitable for SA-BiLASAR equidistant slices is proposed in this paper,and its effectiveness is verified by simulation experiments.3.The motion error and compensation method of SA-BiLASAR are studied.Firstly,the influence of common error forms on SAR imaging is analyzed,and the motion error model of SA-BiLASAR is derived.Then,in view of the traditional self-focusing algorithm cannot be applied in SA-BiLASAR 3D imaging,a Sparse Autofocus via Bayesian Learning Iterative Maximum(SABLIM)algorithm is mainly studied,and its performance and applicable conditions are analyzed.Finally,to further improve the 3D self-focusing imaging quality of SA-BiLASAR,a SA-BiLASAR motion error estimation and compensation algorithm based on the combination of minimum mean square error criterion and maximum sharpness criterion is proposed in this paper.The validity is verified by simulation experiments and measured experiments.