Mitigation of Radio Frequency Interference in HFSWR Using Fractional Fourier Transform Based Filtering Algorithms

The detection performance of high-frequency surface wave radar (HFSWR) is highly susceptible to radio frequency interference (RFI). The fact that external RFIs will turn into a chirp signal and the fractional Fourier transform (FRFT) is a potent tool to analyze the chirp signal, motivates us to use FRFT in interference mitigation. In this letter, two new RFI suppression schemes are proposed, of which one is based on hybrid used of FRFT and autoregressive (AR) linear prediction algorithm, another is based on joint FRFT and recursive least squares (RLS) adaptive filtering algorithm. The simulation result indicates that the proposed schemes can effectively mitigate external RFIs even when the interferences cover Bragg peaks. The experimental result shows that the proposed schemes can effectively suppress RFI without losing echoes, and the signal to noise-plus-interference ratio is improved by 6 dB on average after RFI suppression.