Nonstationary HF interference rejection in adaptive arrays

A high frequency (HF) skywave over-the-horizon (OTH) radar can operate at long ranges, and over very wide areas, by exploiting the ability of the ionosphere to reflect HF signals. This mechanism, allowing long-distance propagation of radio waves, may similarly enable the reception of unwanted radio frequency interference (RFI), capable of severely degrading both skywave and groundwave radar performance. The quality of HF communication links is similarly limited by RFI transmissions from other users in the crowded HF band (3-30 MHz). This paper analyses the statistical performance of various adaptive beamforming algorithms in terms of nonstationary HF interference cancellation using data collected by the receiving array at the Jindalee Facility Alice Springs (JFAS) OTH radar in Australia.