Spread Doppler Clutter Mitigation for Oth Radar by Physics- Assisted Adaptive Processing

The detection performance of skywave HF over-the-horizon radars is fundamentally limited by ionospheric motion which causes spreading of surface clutter returns in Doppler space. This paper exploits a model for HF propagation through ionospheric irregularities based on a thin phase screen formulation which is used to derive the Doppler spread and the spatio-temporal dependence in the received field due to ionospheric motion. This paper presents an adaptive space-time processing approach for mitigating the range-coincident main-lobe spread Doppler clutter (SDC). This method exploits the temporal correlation between main-lobe and side-lobe returns of the received field using reference beams for clutter cancellation in directions predicted by the thin-phase screen propagation model. Initial processing on simulated SDC data with injection of a simulated target shows that this approach can provide a target-to-clutter ratio improvement greater than 10 dB.