Using SVD-FRFT Filtering to Suppress First-Order Sea Clutter in HFSWR

This letter presents a novel signal processing method for HF surface wave radar that offers a solution to suppress significant sea clutter interference. Conventional clutter rejection methods, when the target signal and first-order sea clutter are mixed in the Doppler spectrum, tend to eliminate both the target signal and clutter without distinction. To address this problem, the frequency-modulated difference between the target signal and clutter is considered. Target echoes can be characterized as a linear-frequency modulation signal in long coherent time, while first-order sea clutter can be regarded as a superposition of several single-frequency signals. Based on the hybrid use of singular value decomposition (SVD) and the fractional Fourier transform (FRFT), SVD-FRFT filtering is conducted to suppress the components of the first-order sea clutter without impairing the target signals. The effectiveness of this method is illustrated by simulation and experimental results. It is further demonstrated that SVD-FRFT filtering can improve the signal-to-clutter ratio (SCR) to up to 40 dB for different SCRs.