Narrowband RFI Suppression Based on Gaussian Function for UWB Synthetic Aperture Radar

Abstract

Ultra-wideband synthetic aperture radar (UWB SAR) working at very high frequency or ultrahigh frequency (VHF/UHF) not only has the characteristics of all-weather, all-weather operation and high-resolution imaging, but also has the strong penetration capability, which can detect and image the concealed target under the vegetation. However, there are a large number of radio frequency interference (RFI) signals in the VHF/UHF band. The UWB SAR system will also receive the RFI signal when receiving the target echo signal, which will seriously affect the detection ability and imaging quality of the UWB SAR. The frequency domain notch method is one of the most common methods of the RFI suppression in the UWB SAR imaging, which transforms each pulse echo signal to the range frequency domain to concentrate the energy of the RFI signal and set the threshold to suppress the RFI signal. But the RFI suppression performance of frequency domain notch method depends heavily on the interference threshold, and the RFI suppression of each pulse echo separately will always lead to a large amount of the residual interference. Thus, a narrowband RFI suppression method based on Gaussian function for the UWB SAR is proposed in this paper. Because the RFI signal has the narrowband characteristic, the proposed narrowband RFI suppression method based on Gaussian function transforming the echo signal into two-dimensional frequency domain, which can concentrate the energy of the RFI signal further than that into range frequency domain only, so that the RFI signal can be extracted by the Gaussian function and then eliminated. The simulation results show that the narrowband RFI suppression method based on the Gaussian function has the better effect of the RFI suppression than the frequency domain notch method.