SAR Imaging Of Moving Target Using Two Dimensional Autofocus

Synthetic aperture radar(SAR)is a coherent imaging system,which can provide high azimuth resolution by coherently processing multiple echo pulses.After decades of development,SAR imaging of stationary targets is becoming more and more mature.With increasing resolution of SAR imaging,high resolution imaging of ground moving targets has become a hot topic in recent years.Due to uncertainty on target's motion,SAR processing can't compensate for the two-dimensional(2-D)phase error of moving targets completely.Therefore,moving targets SAR images often appear 2-D defocused.To obtain accurate refocused images,we need to refocus the defocused moving targets in SAR images.In this paper,a 2-D autofocus method for refocusing defocused moving targets is presented by exploiting the analytical relationship between the 2-D phase error and APE.The proposed approach offers obvious advantages in both computational efficiency and estimation accuracy.The main work of this paper is as follows:Chapter 1 is the introduction.Starting from the research background and significance,this paper reviews the SAR skills and its origin.Then,analyzes the domestic and foreign research status of SAR imaging technology and SAR autofocus technology,and introduces the main work and structure of this paper.Chapter 2 is the study of PFA.First is to introduce the principle of PFA imaging,and introduced the PFA geometric model,then introduced the PFA imaging algorithms based on the scale transform as the basis of the error analysis in the fourth chapter.Chapter 3 established the model of moving target echo is established.Based on that,azimuth displacement,azimuth defocusing and range cell migration of moving target caused by self-motion are analyzed and verified by simulation experiments.Then introduced the ISAR technology in moving target processing and autofocus algorithm,also analyze their shortcomings.Chapter 4 is the study of 2-D autofocus method The new method only requires a direct estimate of APE,while the residual 2-D phase error is computed directly from the estimated APE by exploiting the analytical relationship between the 2-D phase error and APE.The simulation experiment also proved the proposed approach offers clear advantages in both computational efficiency and estimation accuracy.And how to compensate the signal when the signal exists PRF ambiguity.Finally,concluding remarks on the full text of the work are summarized,and prospect the problems needs to be further study.