基于修正斜距模型的GEO SAR远地点的CS成像算法

A Chirp Scaling Algorithm Based on Modified Range Model at Apogee in GEO SAR

针对地球同步轨道SAR(GEO SAR)卫星的轨道曲率大,若使用传统直线斜距模型,将不能正确地描述卫星处于远地点时场景目标的"近远近"斜距历程,建立了一种曲率为负的修正斜距模型.该模型能够准确地描述远地点目标的斜距历程;基于该修正的斜距模型精确地推导了GEO SAR远地点回波信号的二维频谱表达式,并给出了一种适用于GEO SAR远地点成像的修正CS成像算法;在方位向成像处理时补偿随距离线性变化速度引起的空变相位,实现GEO SAR较宽的成像幅宽的聚焦处理.并通过场景尺寸为100 km×100 km点阵的GEO SAR成像处理,验证了该基于修正斜距模型的CS成像算法的有效性.

In geosynchronous synthetic aperture radar（GEO SAR）,due to the high orbit curvature,the traditional slant range mode cannot descript the ＂near-far-near＂ slant range history at apogee.This paper presented a modified range model in which curvature was negative to descript the range history at apogee in GEO SAR accurately.Based on the modified model,an accurate two-dimension spectrum of GEO SAR echo was obtained.Then,a modified ChirpScaling algorithm for apogee in GEO SAR was presented.At the same time,in order to focus wide swath in GEO SAR,the phase error caused by the linear variation of velocity in range direction can be compensated in azimuth processing.Finally,the simulation result of a large scene（100 km X 100 km） proves that the CS algorithm based on the modified range model can achieve the focusing image of GEO SAR at apogee.