Research On Suppressing Of Radio-Frequency Interference In HF Radar

Radio Frequency Interference (RFI) can greatly degrade the performance of High-Frequency GWR. In this paper, methods of suppressing RFI in HF GWR are studied. By analyzing the characteristic of RFI, the model of interference is established, and two methods are presented to process RFI. One is a detect-eliminate-interpolate method processed in time domain, the other is a MTI filtering method processed in Doppler domain.Since RFI presents instantaneous and singularity characteristics in a sampling period of HF GWR, a detect-eliminate-interpolate method is presented. Firstly those sampling points when RFI performing are detected via Wigner-Ville Distribution(WVD) and Wavelet transformation, and then they are set to zero. To reduce the range sidelobe caused by notch window, AR model based interpolation is utilized. When RFI is relatively weak, this method performs well. But when RFI becomes strong, this method will invalidate due to useful signal energy's losing.The MTI filtering method is based on the fact that RFI represents strong pertinence along range bins in Doppler spectrum. By separate covariance matrix of received signal into signal-space and noise-space, RFI is suppressed while sea echoes and target echoes are reserved.Computer simulation and experiment prove that these methods are valid. Average SNR improvement can be about 10dB.