变波门大斜视滑动聚束SAR成像关键技术分析

大斜视高分辨率SAR成像中，改变开启波门的操作可以在保证距离测绘带宽度的情况下减小录取回波的数据率，滑动聚束的扫描模式可以在保证高分辨率的情况下扩大方位场景范围。但是变波门后只能获得交错的距离徙动曲线，而滑动聚束的扫描方式容易引起方位模糊。该文研究了变波门大斜视滑动聚束模式下SAR成像的关键技术，提出分子孔径升采样的解模糊算法以及基于空域波束分割的二级极坐标格式算法(PFA)，将对波门变化的补偿融入运动补偿处理的过程中，通过先波束分割后子图像拼接的方法突破了PFA平面波前的近似对成像场景尺寸的限制，显著扩大了传统PFA的有效成像场景范围，使其适用于大斜视滑动聚束模式下的大场景成像。实测数据处理表明了算法对大场景变波门数据的有效性。

Research on Key Technique of Highly Squinted Sliding Spotlight SAR Imaging with Varied Receiving Range Bin

In highly squinted and high resolution SAR, the data receiving range bin can be continually adjusted to minimize the sampled data in echo collection, but the staggered range cell migration needs extra processing to be eliminated. To enlarge the imaging scene size with a relatively high resolution, sliding spotlight working mode could be used, yet this mode may cause azimuth ambiguity. In this paper, the key technique of highly squinted sliding spotlight SAR imaging with varied receiving range bin is investigated, a sub-aperture based upsampling ambiguity-resolving method is utilized and a new beam segmentation based 2-step PFA method is proposed, which incorporates the stagger compensation to the procedure of motion compensation. The method performs beam segmentation via digital spotlighting preprocessing firstly to generate multiple full-resolution phase histories of smaller image patches, which allow the approximation of planar wavefront in traditional PFA. PFA is used to produce focused fine resolution image for each small patch．Finally, all focused image patches are seamed together to get a full image. This divide-and-conquer approach breaks the image size limit in traditional PFA, and extensively enlarges the valid focused scene suitable for sliding spotlight mode. This new algorithm is validated to be effective and efficient via real data experiments．