高轨星机BiSAR分辨率分析及成像参数优化设计

Method for GEO Spaceborne-airborne BiSAR Resolution Analysis and Imaging Parameters Optimal Design

高轨SAR具有覆盖范围广,重访时间短的优势。但是如果采用高轨SAR卫星同时作为发射机和接收机,不能充分发挥高轨SAR的这些优点。采用飞机或低轨卫星作为接收机平台不但能够更灵活地针对目标区域成像,而且分辨率也将大大提高。但是星机双基SAR(BiSAR)的几何构型复杂,难以直观地获知任意几何构型BiSAR的分辨率特性。该文从BiSAR基平面分辨率出发,根据几何构型得到基平面分辨率与地平面分辨率之间的几何关系,解析地表示出了BiSAR在地平面上的分辨率形状。据此可以评估BiSAR系统的分辨力,并且能够通过优化设计系统带宽和合成孔径时间两个参数使得BiSAR系统能够实现更好的分辨率特性。最后,仿真结果验证了方法的有效性。

The GEO SAR has its own features such as wide coverage and short revisit time. However, when the GEO SAR is both used as a transmitter and a receiver, its advantages is not well exploited. If an airplane or a LEO satellite is adopted as a platform of the receiver, not only the interesting regions can be observed flexibly, but also finer resolution can be achieved. However, the geometry of the BiSAR is complicated, so it is not easy to acquire how much resolution an arbitrary BiSAR system can reach. Thus starting with the resolution on the basic plane of a BiSAR system, and combined with the resolution’s projection relation between the basic plane and the plane tangent to the earth’s surface, the resolution shape’s expression on the ground can be got finally. Based on the expression, the resolution of a BiSAR system can be assessed, and finer resolution can be realized through optimizing two parameters, including signal bandwidth and synthetic aperture time. Finally, the simulation results validate the effectiveness of the proposed method.