GEO SAR天线波束指向定标中的误差分析

GEO SAR因其超宽测绘带和超长的合成孔径时间，导致低轨SAR波束指向定标方法不再适用，进而采取基于多脉冲分时比幅的波束指向定标方法。本文针对该指向定标方法，结合GEO SAR星地几何关系，对卫星姿态变化、三维系统性误差以及波束指向定标方法中接收机信噪比和通道增益稳定性引入的指向误差进行了详细的推导和仿真分析。仿真结果表明，0.003°的姿态测量误差会引入0.003°的距离向指向误差和0.0033°的方位向指向误差；三维系统性误差是导致天线波束指向变化的主要误差源；当SNR≥35 dB、通道增益稳定性优于1 dB时，GEO SAR波束指向定标方法引入的指向误差小于0.001°。

Error Analysis of GEO SAR Antenna Beam Pointing Calibration

Due to the wide mapping band and long synthetic aperture time of GEO SAR, the antenna beam pointing calibration methods applied in LEO SAR are no longer applicable, then the beam pointing calibration method based on multi?pulse time?sharing amplitude comparison is adopted. In this paper, aiming at this beam pointing calibration method, based on the geometrical relationship of satellite and earth, the pointing error introduced by the attitude measurement errors, three?dimensional systematic error and the receiver SNR and channel gain stability are analyzed in detail. The simulation results show that the attitude measurement errors of 0.003° will introduce 0.003° pointing error in elevation and 0.0033° pointing error in azimuth; the three?dimensional systematic error is the main factor of antenna beam pointing deviation; when the SNR is more than 35 dB and the channel gain stability is better than 1 dB, the pointing error introduced by GEO SAR beam pointing calibration method is less than 0.001°.