Radio Frequency Interference Suppression in Low-Frequency Wideband Synthetic Aperture Radar Systems

Abstract:
A Low-Frequency Synthetic Aperture Radar (LF-SAR) can be capable of foliage or ground penetration, leading to a range of applications including the detection of man-made objects concealed by foliage and Earth observation remote sensing. This paper addresses the problem of Radio Frequency Interference (RFI) suppression when operating a wideband LF-SAR in the UHF/VHF bands. The effectiveness of the Wiener filter in removing RFI is demonstrated through its application to real world LF-SAR data. It is shown that through the use of the Wiener filter a significant reduction in the sidelobe levels of the point spread function can be achieved, compared to those obtained using the LMS algorithm. However, in the presence of strong RFI the image quality may be degraded due to the introduction of wide notches into the frequency spectrum. In a comparison of interpolation algorithms used to reconstruct the missing data, a novel approach based on Autoregressive modelling is found to provide the best image quality, which can be close to that of the original undegraded image.