编队卫星SAR回波多普勒频率特性分析

Analysis of Doppler Characteristics in Formation Flying Satellite-borne SAR

针对以编队小卫星为平台的合成孔径雷达(SAR)应用系统,给出了一种推导多普勒频率解析公式的方法。该方法利用编队卫星与地面目标之间的空间几何关系及编队卫星之间的相对运动,以SAR系统参数、主星轨道根数、编队构形及目标运动参数等为前提条件,通过多个坐标系之间的相互转换,将地面目标与编队卫星的运动矢量统一在地心赤道坐标系内推导了目标回波的多普勒频率表达式。分析了回波多普勒中心频率及多普勒调频斜率的特性,通过仿真验证了从星轨道根数计算公式及多普勒频率计算公式的正确性,为进一步研究编队卫星SAR系统参数设计和选择奠定了基础。

For the formation flying satellite-borne SAR system, a set of analytical formulas on Doppler frequency is presented. The method is based on spatial configuration and relative movement between the formation flying satellites and targets on the earth, and considers SAR systemic parameters, orbital elements of main satellite, formation configuration and movement parameters of target as known condition. By mutual conversion between all kinds of reference frames, the kinetic vectors between targets on the earth and the formation flying satellites are uniformly characterized in the earth-centered Inertial reference frame, and then the formulas on Doppler frequency of target echo are derived. The characteristics of Doppler centroid and Doppler frequency rate are analysed in the paper. Simulation results show the validity of the formulas on the orbital elements of companion satellites and Doppler frequency of target on the earth. The work is significant for system design and performance analysis of the formation flying satellite-borne SAR.