提高双通道低频SAR干涉图性能的方法

沿航向干涉法是一种检测运动目标简单易行的有效方法。在低频双通道SAR系统中,为了保证干涉性能,不仅要考虑降低图像相干性的各类误差,还要考虑实时成像过程中残留的RFI对通道图像的影响。本文首先与高频系统中的误差进行比较,分析了影响低频双通道SAR系统的主要误差及其特点;其次分析了RFI对干涉图干扰的基本原理与特征,进而提出了一种提高双通道低频SAR干涉图性能的误差校正方法。该方法充分考虑了低频SAR系统的接收机频率特性误差、天线方向图误差、干涉相位误差及图像配准误差,利用基于方位时域距离频域干涉图的中值滤波器能够有效抑制具有窄带特性、时变性和空变性的RFI信号。国内首批机载双通道低频SAR实测数据验证了该方法的有效性与可靠性。该算法运算简单,效率高,适合对沿航向干涉法的实时处理。

A Method to Improve the Performance of the Along-Track Interference Image in Dual-Channel Low Frequency SAR

Along track interferometry(ATI) is an easy and efficient method to detect ground moving targets.In low frequency synthetic aperture radar(SAR) system,it is necessary to consider not only kinds of errors that will reduce the coherence of image pairs,but also the unsuppressed radio-frequency interference(RFI) left from the real-time imaging.This paper first analyzes the characteristic of each error in low frequency dual-channel SAR,comparing to those in the high frequency band system,and then analyzes the principle and characteristic of RFI on the interferometric image.A method to improve the performance of along-track interferometric image in low frequency SAR has been proposed further.This method can compensate the difference of receiver frequency,the difference of beam pattern,interferometric error and coregistration error,and use median filters in the azimuth-time range-frequency domain interferometric image to suppress the residual RFI with narrow bandwidth,varying with slow time and radiation angle.The first domestic real data with dual-channel low frequency SAR system has tested the effectiveness and feasibility of this method.It has shown that this method can be operated easily and efficiently with low computation,which is suitable for the real time processing of ATI.