Null phase-shift polarization filter for high frequency radar radio interference suppressing

Radio interference suppressing is a main problem to be solved in high frequency (HF) radar system. To effectively cancel the interference, the parameters of the polarization filter should timely adapt to the variation of the polarization of the interference, which may impact the amplitude and phase of the desired signal passing through the same polarization filter during the coherent integration time (CIT) and render the enhancement of the signal integration a failure. To avoid this, a null phase-shift polarization (NPSP) filter is proposed in recent years. Based on the principle of the NPSP filter, a simplified NPSP is proposed in this paper. The interference can be suppressed completely while the target signal remains without distortion. Some applications of HF radars for suppressing the radio interference are introduced. Simulation results from the experimentally derived data indicate that the proposed NPSP filter is effective in HF radar or other coherent systems.