High Angular Resolution RFI Localization in Synthetic Aperture Interferometric Radiometers Using Direction-of-Arrival Estimation

Radio-frequency interference (RFI) seriously affects the retrieval of geophysical parameters from the measurements of microwave radiometers. An accurate geolocation of the RFI is crucial to effectively switch off illegal transmitters. In this letter, a new RFI localization method is proposed to improve the achievable angular resolution by using beamforming and direction-of-arrival (DOA) estimation techniques. The proposed RFI localization techniques can be employed in synthetic aperture interferometric radiometers, such as the European Space Agency (ESA) Soil Moisture and Ocean Salinity (SMOS) mission. Two DOA estimation techniques are tested for the RFI localization: Capon and MUSIC. The feasibility of these methods is demonstrated with SMOS data. In the test results, the MUSIC beamforming shows a better performance of RFI localization than the SMOS Fourier imaging and the Capon, in terms of accuracy and resolution.