Robust DOA Estimation Under Batched Clutter Suppression in Passive Radar

In passive radar, the target echo component in the reference channel is an overlooked potential threat. This component will severely affect the direction-of-arrival (DOA) estimation results via the clutter suppression step. Passive radar often relies on clutter suppression to attenuate the masking effect of the target caused by clutter sidelobe, and batched clutter suppression is one of its key strategies. When considering the batched clutter suppression, the target echo component in the reference channel has a complex effect on the DOA estimation. In this article, the mechanism of this effect is analytically derived in both time and frequency domains, and the results show the limitations of the existing studies. We propose a robust DOA estimation algorithm that is robust to both time and frequency-domain cases. The frequency-domain version relies on the frequency-domain 2-D cross correlation, for which we give a fast calculation. We note the nonorthogonal problem in clutter subspace extension, and furthermore, provide an improved scheme to mitigate its adverse effect on DOA estimation. Finally, we validate the effectiveness and robustness of the proposed algorithm by simulation and measured passive radar data.