Spread-Doppler clutter cancellation in high frequency hybrid sky-surface wave radar

In High Frequency (HF) hybrid sky-surface wave radars, the spread-Doppler clutter (SDC) severely deteriorates the detection performance of low-velocity surface vessels. To suppress SDC, a large number of training samples are usually needed which can be hardly satisfied due to the heterogeneous clutter environment. In this paper, a space-frequency cascaded approach is proposed to suppress SDC using training samples from only one range cell. The proposed method involves two components. First, a frequency domain minimum variance distortionless response (MVDR) weight is designed to cancel the SDC. Second, the spatial orthogonal projection matrix is constructed to estimate clutter covariance matrix, where the signal of interest has been excluded from the training data. According to the experimental results, the proposed method can obtain a more accurate estimation of the clutter characteristics with limited training data and thus achieve better clutter suppression performance.