Phase Error Analysis And Sparse Refocus Processing Of Moving Targets In Airborne SAR

Synthetic Aperture Radar(SAR)is a class of radar imaging system with all-day and all-weather capability,and is widely used in both military and civil applications.Currently,research on airborne SAR imaging processing of stationary target echoes has been gradually improved.However,when there are moving targets with unknown motion in the irradiated scene,the SAR imaging results often also show geometric distortion and scattering,requiring refocusing.To solve these problems,this paper investigates the derivation of the Polar Format Algorithm phase error model for moving targets,and then implements the refocusing of sparsely sampled data in conjunction with Compressed Sensing.The main research areas of this thesis includeFirstly,the airborne SAR moving target echo signal model is introduced,starting from the construction of the echo signal model,and the impact brought by the moving target on SAR imaging and the reasons for its generation are analyzed.Secondly,the keystone transform-based SAR moving target imaging algorithm is analyzed,introducing the basic principle of the transform,the way to implement the keystone transform and the process of the keystone transform-based SAR imaging algorithm,and the two-dimensional matched filtering after the keystone transform can realize the moving target focused imaging.The experimental results show that the keystone transform-based moving target imaging algorithm can effectively achieve focused imaging of moving targets.Subsequently,the dual-base airborne SAR moving target dual-base PFA imaging process and the derivation and analysis of the moving target scattering phase error are introduced,proposing the use of the stepwise inversion method to re-derive the moving target phase error,and constructing a matched filter to directly compensate the whole phase according to the phase error formula,which can compensate not only the azimuthal upward scattering,but also part of the residual distance ward scattering and distance migration.Finally,the effectiveness of the method is verified through simulation experiments.Finally,according to the characteristic of SAR echo signal possessing sparsity,the SAR moving target image reconstruction is proposed to be realized by the compressive-aware reconstruction method.Firstly,starting from constructing the mathematical model of SAR echo signal,the compressive-aware reconstruction algorithm is derived to realize the SAR moving target image refocusing,and according to the PFA moving target phase error signal model,a dictionary of phase error matrix is established as the observation of the compressive-aware recovery algorithm The Iterative shrinkage threshold algorithm is used to achieve moving target image reconstruction.Finally,the effectiveness of the ISTA algorithm for moving target image refocusing is verified by experimental simulation.