基于联合滤波的SAR射频干扰抑制方法

A Combined Filtering Method for Radio Frequency Interference in SAR Data

面对日益复杂的空间电磁环境,合成孔径雷达(Synthetic Aperture Radar,SAR)容易受到射频干扰(Radio Frequency Interference,RFI)的影响,从而严重影响图像的判读和解译。尤其是低波段(例如P波段)SAR系统,由于频段内存在大量的电视广播信号,更容易受到RFI的影响。在建立了射频干扰信号模型的基础上,根据RFI信号的高功率、窄频带特点,提出了一种基于联合滤波的RFI抑制方法。该方法结合了传统的陷波法和子空间投影法在SAR射频干扰抑制方面的优点。其基本思想是:首先利用子空间投影法,将回波投影到目标信号子空间,获得参考信号,根据该参考信号,利用3δ准则判别出回波中存在的干扰信号,进行陷波、赋值处理。这样既降低了子空间投影法在抑制干扰过程中由于信号子空间判断误差而引入的虚警,又为陷波处理提供更准确的判别门限和更优的权值,可有效提升干扰抑制效果。仿真结果验证了该方法的干扰抑制效果优于子空间投影法及传统频域陷波法。

Faced with an increasingly complex electromagnetic environment of space,synthetic aperture radar（SAR）is susceptible to the influence of the radio frequency interference（RFI）signals,thus seriously affecting the SAR image interpretation.This is even worse for the low-frequency-band SAR systems（P-band for example）which are disturbed by a lot of television broadcasting signals.Based on the model and characteristics of the RFI signals,ajoint RFI suppression method is proposed.This method combines the advantages of traditional notch method and subspace projection method in SAR RF interference suppression.The basic idea is as follows.First,project the echo onto the target echo signal subspace to obtain a reference signal by using the subspace projection method.Second,based on the reference signal,detect the RFI signal from the echo by using the 3δrule and carry out the notching and assignment process.This not only reduces the false-alarm probability that introduced by the subspace projection method during the interference suppression process,but also provides a more accurate determination threshold and a better weight for notching,which can effectively enhance the interference suppression effect.The simulation results show that the proposed method is better than the subspace projecting method and the notch method.