Degree-of-Polarization-Based Radio Frequency Interference Detection for Synthetic Aperture Radar

In microwave remote sensing, radio frequency interference (RFI) caused by other microwave systems has been a critical issue. RFI degrades the quality of synthetic aperture radar (SAR) images and disturbs phase and polarimetric information. Therefore, RFI must be detected and mitigated correctly to analyze SAR data accurately. In this paper, we propose a novel RFI detection method based on the polarization states of received signals in either the time or frequency domain. Our study demonstrates that RFI from artificial sources is often more polarized than radar echoes from natural scatterers. We use the degree of polarization (DoP) to measure the polarization states and detect highly-polarized RFI. The simulation results indicate that the proposed method was more accurate than the conventional power-spectrum-based methods and improved the detection limit by 4 dB compared to the conventional method based on the similarity between polarizations. We demonstrate the effectiveness of the proposed method by using data obtained by Phased Array type L-band Synthetic Aperture Radar (PAL-SAR) aboard Advanced Land Observing Satellite (ALOS).