一种适用于GEO SAR远地点的改进SRC算法

针对地球同步轨道合成孔径雷达在远地点采用原有的等效直线模型速度和斜视角会出现复数,以及"Stop-and-Go"假设不成立的问题,进行了二次距离压缩算法(SRC)的改进,提出了一种新的信号模型,修正了成像算法中的补偿函数,而且采用高阶近似的方法得到了精确的方位向调频率,改进了方位向压缩函数.结果表明改进的二次距离压缩算法可以在合成孔径时间100s内聚焦远地点40km×40km的场景,且场景边缘点的峰值旁瓣比和积分旁瓣比与理论值非常接近.

A Modified Secondary Range Compression Algorithm at Apogee in GRO SAR

It is known that computing the right range is very complex in geosynchronous orbit (GEO) synthetic aperture radar (SAR) for the factors that, firstly, the velocity and the slant angle at apogee fitted by the line trajectory model are the complex numbers and, secondly, "Stop-and-Go" assumption will brings about a range error. This paper explores the range issue and proposes a new range mode. It was found that the problem of complex number could be avoided by adopting the norm to express the range and the impacts of "Stop-and-Go" assumption might be considered in the modified range model. Based on the new range model, the expression of two-dimensional echo in frequency domain was deduced and the compensation function in the course of imaging algorithm was improved. Further, an accurate azimuth compression function was modified by means of a high-order chirp rate in azimuth. The result shows that a 40 km×40 km scene can be focused very well under the synthetic aperture time (SAT) of 100 s by the improved secondary range compression (SRC), and the peak side-lobe ratio (PSLR) and integrated side-lobe ratio (ISLR) of the edge points are very near to the theoretical value.