编队卫星InSAR系统的相位同步分析

Analyses of Phase Synchronization on InSAR System Based on Formation-Flying Satellites

编队卫星InSAR系统属多基雷达系统,依靠编队卫星构型形成干涉所需的基线。一发多收工作模式下的编队卫星InSAR高程测量系统,协同工作的雷达间必须建立时间同步、相位同步和空间同步,其同步精度将影响InSAR系统的功能与性能。三大同步中,相位同步误差直接影响SAR复影像的相位误差,从而影响系统的高程测量精度。本文根据编队卫星条件下SAR成像的要求,对相位同步的要求进行了分析,并给出了由于相位不同步所引起的相位误差对InSAR高程测量精度影响。分析结果表明,编队卫星InSAR系统对于相位同步的要求包含两个方面:一是为保证被动雷达能够对回波实现相参成像,在整个合成孔径时间内,主动和被动两个雷达在载波相位上必须保持确定和可知的关系,且其差值随系统距离向分辨率的不同必须限定在一定范围内;二是在整个干涉数据的录取时间里,主动和被动两个雷达载波相位同步误差不能超过高程测量的精度要求所允许的误差。

The InSAR system based on formation-flying satellites is a multi-radar system, which depends on the satellites formation to form the baselines needed by the interferometry. For this system, time synchronization, phase synchronization and spaee synehronization should be established by the cooperated radars with each other. The precision of three synchronizations will influence the systematic function and performance of the InSAR system. The error of phase synchronization among the three synchronizations will affect the phase error of SAR SLC image directly, and influenee the elevation measurement precision sequentially. In this paper, the requirements on phase synchronization are analysed based on the need of the SAR imaging under the eondition of formation-fly- ing satellites, the influences on the elevation measurement precision due to the loss of phase synchronization are also given. The results show that the requirements on phase synchronization inelude two facets, firstly, the carrier frequencys of master/slave radars should keep certain relationship within synthetie aperture to assure the SAR ima- ging to be done successfully, and the carrier frequency differenee must be restricted to a determinate range which depends on different slant range resolutions. Secondly, the phase synchronization error can not overrun a limit which is requested by elevation aceuracy demand during the whole interferometrie data acquirement time.