Study On Wavefront Curvature Compensation And Motion Compensation Of Spotlight SAR

Spotlight Synthetic Aperture Radar is a common working mode of SAR,During the spotlight SAR data collection the antenna beam is pointed towards thescene to provide an extended sequence of radar echo measurements. So it providesthe better azimuth resolution.The Polar Format Algorithm (PFA) as a classic algorithm for spotlight SAR,Because of its algorithm is simple and easy to implement in engineering, so it hasbeen widely used. In the process of applying the PFA algorithm to achievemeasured spotlight SAR imaging data, Faced with three major problems:(1). Howto implement the interpolation processing of squint mode.(2). How to compensatethe wavefront curvature effect in polar format imagery.(3). How to solve thedefocusing and distortion that caused by imprecision of the measured data andnon-ideal Motion of platforms. This paper is mainly to solve these three problems,The main contents are following:1. Introduce the process spotlight SAR echo data acquisition and storage,Analysis of the characteristics of the echo signal. Finally, it is the GPS datapreprocessing.2. Interpolation processing as a key part of the PFA algorithm, This paperanalyzes the interpolation process of broadside mode and squint mode.3. Imprecision of the measured data and non-ideal Motion of platforms alsocause the defocusing and distortion of image, so motion compensation is required.This paper introduce the technology of range alignment which was also used in theISAR imaging processing, Realization of the translational error compensation.Then introduce the classic autofocus algorithm: PGA, MD. And analyze theshortcomings of traditional self-focusing algorithm. Introduce the provedalgorithm: MD-PGA algorithm, To Improve the focusing effect.4. Deducing the formula of phase error caused by unrealistic assumption ofstrictly plannar wavefront, and analyzing the impact in the imaging process. Thespace-variant post-filtering approach to compensate the wavefront curvature effectin polar format imagery is presented in this paper, for improving the quality of theimage.