Dense radio frequency interference suppression in HF radars

Radio frequency interference (RFI) is often a major problem in high-frequency (HF) radar operation, and until now, few existing methods worked very well to suppress dense RFI. In this letter, a theoretical analysis of the range-domain correlation of RFI in HF chirp radar is presented, and the relation between the correlation functions of RFI in range and fast time domain is given; based on this, a new method for RFI suppression is developed. The echo signals at the reserved range bins are used to construct an interference subspace, and then, the signals at the range bins of interest are projected onto its orthogonal subspace to suppress the RFI. When applied to radar signal processing, the method suppressed dense nighttime RFI effectively. It greatly improves the radar´s detection performance in dense RFI.