星地双基地SAR时频同步技术研究

摘要

This paper researches the estimation method of the time and frequency synchronization errors of SS-BisSAR (Space-surface Bistatic SAR) based only on the direct signal and discusses the estimation precision. Firstly the model of direct signal is built and analyzed and the traditional method to estimate the Doppler centroid frequency is modified to fit the case in SS-BisSAR and in this way, the estimation method of synchronization error is proposed. Finally the relation between the SNR of signal and the estimation precision is derived and analyzed. The conclusion shows that, only utilizing the direct signal, the estimation method is feasible. As the precision of estimation is affected by the SNR, carrier frequency and signal bandwidth, etc. So, the system parameters should be reasonably designed to realize a high precision estimation in order to compensate the errors and improve the imaging quality of SS-BisSAR.%本文研究了只依靠直达波信号的星地双基地SAR的时频同步误差估计方法并对估计精度进行了讨论.首先对直达波信号进行建模和分析,再对传统的基于幅度的多普勒中心频率的估计方法在双基地SAR情况下进行了估计结果的修正,从而提出了一种时频同步误差的估计方法.最后推导并分析了接收信号的信噪比、系统载频和带宽等因素与估计精度的定量关系.结果表明,当先验信息较少时,仅通过直达波数据进行同步误差的估计是可行的.由于误差估计精度由信号的信噪比、信号带宽和载频频率等因素共同决定.因此,需要对系统参数进行合理的设计,以实现高精度的误差估计,从而实现同步误差的补偿,提高双基地SAR的成像质量.