近前视弹载SAR的改进后向投影成像算法

针对现有的弹载合成孔径雷达(SAR)大斜视算法所处理的斜视角度受限,传统的后向投影(BP)算法运算量大以及已有的快速后向投影算法不能进行并行处理等问题,提出了一种适于并行处理的近前视弹载SAR的改进后向投影算法.首先根据近前视弹载SAR的几何关系,建立回波信号模型,然后在距离方向上对弹载SAR扫描场景进行等间隔分割,在合并子孔径的同时分裂图像,达到所需图像精度时停止合并和分裂,再相干叠加反向投影到扫描场景的分割小区域内的回波,这样就会得到扫描区域的弹载SAR图像.对于各个条带可以采取并行处理来分别成像,可以进一步提高成像速度.最后利用仿真回波数据和实测回波数据对本文改进算法进行验证,通过与其他算法的比较,证明了本文改进算法可以处理高达86°的近前视场景,并且处理速度大大快于传统BP算法的处理速度,再配合并行处理划分的条带,处理速度会快于现有的改进BP算法的处理速度. 

Improved back-projection imaging algorithm for approximate forward looking missile-borne SAR

In order to solve the problems that the existing high squint missile-borne synthetic aperture radar (SAR) algorithm can not deal with too high squint angle, and that the calculated amount of traditional back-projection (BP) imaging algorithm is too large, as well as that the current fast BP algorithm can not process the echo data in parallel, an improved approximate forward looking missile-borne SAR back-projection imaging algorithm which can process echo data in parallel was proposed. According to geometrical relationship of approximate forward looking missile-borne SAR, an echo signal model was established. And the imaging area was divided to equidistance strip in range along the distance direction. The image was split when merging sub aperture, and the splitting and merging did not stop until the accuracy of image met the requirements. Next the raw echo data was back projected to each strip for coherent integration, and then the missile-borne SAR image was obtained. If these strips were processed for imaging in parallel, the imaging speed would be further improved. Finally, results of simulation echo data and real echo data validate that the improved algorithm can deal with approximate forward looking scene with 86° squint angle, and it can greatly improve the computation speed compared with that of traditional BP algorithm. Moreover, the computation speed is faster than that of other improved BP algorithms by processing those strips in parallel.