RFI Suppression for SAR Systems Based on Removed Spectrum Iterative Adaptive Approach

Wei Xu,Weida Xing,Chonghua Fang,Zhiqi Gao,Weixian Tan,Pingping Huang

doi:10.3390/rs12213520

Abstract

A synthetic aperture radar (SAR) system can be seriously contaminated by radio frequency systems because of working in the same microwave frequency bands, which would degrade the SAR image quality and affect the accuracy of image interpretation. In this paper, a novel radio frequency interference (RFI) suppression approach including RFI identification, band-stop filtering and a removed spectrum iterative adaptive approach (RSIAA) is proposed. First, the smoothing process is added before RFI signal detection to improve the RFI detection capacity. Afterwards, the band-stop filtering with a broaden factor is proposed to mitigate the residual RFI, and it ensures the accuracy of the following removed spectrum recovery by the RSIAA. Finally, the removed spectrum components are estimated from available adjacent spectrum data by the RSIAA in turn to obtain the desired range spectra. Compared with the conventional range frequency filtering method for RFI suppression, the capacity of the weak RFI signal detection is improved, and the increased sidelobes due to the discontinuous spectra are well suppressed. Simulation experiments on both simulated SAR raw data, Gaofen-3 and Sentinel-1 SAR raw data validate the proposed RFI suppression approach.

Highlights

Synthetic aperture radar (SAR) is an active microwave remote sensing instrument for Earth’s surface observation, and it can be widely utilized in both military surveillance and civilian exploration [1]
synthetic aperture radar (SAR) systems have an inherent capability of anti-interference, radio frequency interference (RFI) signals with characteristics of a one-way propagation path and long working time can severely degrade the quality of the desired SAR images [2,3,4]
According to the interference bandwidth to the SAR signal bandwidth ratio, RFI can be divided into narrow-band interference (NBI) and wide-band interference (WBI)

Summary

Introduction

Synthetic aperture radar (SAR) is an active microwave remote sensing instrument for Earth’s surface observation, and it can be widely utilized in both military surveillance and civilian exploration [1]. A novel RFI suppression method including RFI identification, frequency band-stop filtering and the removed spectrum iterative adaptive approach (RSIAA) is proposed. The advantages of the proposed approach can be summarized in three aspects: (1) the more accurate weak RFI detection capacity after the spectrum smoothing process; (2) the better residual RFI suppression effect due to the introduced broadening factor; (3) the improved SAR image quality after the removed spectrum estimation by the IAA. Since all these processing operations could be implemented by a pulse-by-pulse behavior, another important advantage of the proposed approach is the effectiveness to deal with the azimuth time-variant RFI signals. Two-Dimensional Signal to Noise Ratio Peak Side Lobe Ratio Integral Side Lobe Ratio

Interference Formulation and Analysis

M1MHHz zRFRIFI 4 4MMHHzzRRFFI I

Results