地球同步轨道SAR对频率源稳定度的指标分析

Analysis of Oscillator Stability Index in Geosynchronous SAR

地球同步轨道SAR大的回波延时和长的合成孔径时间使得频率源稳定度对SAR成像指标的影响不能像低轨星载SAR一样可忽略,成为制约地球同步轨道SAR系统实现的关键问题之一。本文首先给出频率源相噪模型,在此基础上采用数值积分的方法分析载波相噪对地球同步轨道SAR成像指标积分旁瓣比的影响。信号仿真分析结果表明:典型频率源仅能够满足5 m方位分辨率L波段地球同步轨道SAR系统的要求,但当工作频段提高、系统合成孔径时间增加时,积分旁瓣比将恶化,需要稳定度更高的频率源。

The large echo delay time and long azimuth synthetic aperture in geosynchronous SAR makes the influence of oscillator stability on SAR imaging. It can not be neglected as in the low orbit spaceborne SAR which is a key problem in the implementation of the geosynchronous SAR system. The oscillator phase noise model is introduced,and a numerical integral method is used to analyze the influence of carrier phase noise on geosynchronous SAR ISLR. The integral results show that the typical oscillator only meets the oscillator stability requirements of a L band geosynchronous SAR system with 5 meter azimuth resolution. The ISLR will be degraded under higher carrier frequency and longer synthetic aperture time,thus a higher stable oscillator must be used in Geosynchronous SAR system.