Modified Space-Time Adaptive Processing with first-order bragg lines kept in HFSWR

High Frequency Surface Wave Radar (HFSWR) can perform the functions of ocean environment monitoring, target detection, and target tracking over the horizon. However, its system performance is always limited by the severe ionospheric clutter environment. The ionospheric clutter generally can cover a few Doppler units and a few angle units. Consequently, Bragg lines masked by the ionospheric clutter are difficult to be recognized. In this paper, we exploit the Space-Time Adaptive Processing method to the HFSWR signal processing, and propose a strategy of choosing Protected Doppler Units to improve the Joint Domain Localised (JDL) algorithm. The results with measured data show that the modified JDL algorithm is effective and the Bragg lines masked by ionospheric can be recognized more easily.