Target Reconstruction Method For SAR Based On Phase Retrieval Theory

Synthetic Aperture Radar(SAR) plays an important role in remote sensing, early warning, reconnaissance, alert and many other fields with the advantage of all-weather,full-time, long-range and high-resolution for targets imaging. For the coherent imaging SAR system, there is close connection between SAR imaging result and the phase of the received SAR raw data, and the accurate phase synchronization of the received SAR raw data is the key to well-focused SAR images. However, due to the influence of platform random motion and electromagnetic propagation in turbulent media, there exist phase errors in the received SAR raw data, which cause image defocus. Therefore, the study for phase compensation of SAR data caused by the above reasons is significant.This paper studies the SAR target reconstruction method based on phase retrieval(PR) theory. The major contents and innovation of this thesis are as follows:Firstly, the research background and significance, research status of SAR phase compensation method, the basic principle of SAR imaging and range Doppler algorithm(RDA) are introduced, the effect of radar platform random motion and electromagnetic propagation in turbulent media for the SAR echo characteristics are analyzed, and the phase gradient autofocus(PGA) algorithm is introduced.Secondly, the principle, development and application of PR algorithm are described,two classical PR algorithms(Error-Reduction Algorithm and Hybrid Input-Output Algorithm) are introduced. In consideration of the shortcomings of classical PR algorithm applied to SAR signal phase recovery, an improved PR algorithmoversampling smoothness(OSS) algorithm is proposed in order to solve the SAR signal phase recovery problem, the feasibility of PR algorithm applied to SAR target reconstruction is analyzed, the superiority of OSS algorithm applied to SAR data is verified by contrasting with the PGA algorithm.Finally, the specific forms of SAR phase errors are introduced, the SAR target recovery results that recovered by OSS algorithm and the classical PR algorithm respectively are compared by the simulation. The effect of changing the filter parameter? for SAR target recovery is analyzed, the comparison results are provided bythe computer simulation data. Compared with the recovery results which the corrupted phase of the Fourier transform of the intensity image is not used in the iterative process,the recovery results that the corrupted phase is used are much better. At the same time,the effectiveness of this method is demonstrated by the computer simulated data.