Joint Channel Estimation and Zero-Doppler Clutter Suppression for Passive Radar under Multiplicative Distortions via Regularized ECA

In this paper, we consider the problem of suppressing the zero-Doppler clutters for the passive radar operating under the multiplicative channel. In this scenario, channel distortion leads to the inconsistency between the echo and the reference signal, which deteriorates the performance of the conventional temporal clutter suppression algorithm. In this work, we propose a novel temporal method which can jointly estimate the channel distortion and suppress the zero-Doppler clutter. The proposed method modifies the conventional extended cancellation algorithm (ECA) by imposing two additional regularization items. The proposed optimization problem is non-convex and it is solved by a sequential iteration approach. In particular, we decompose the original formulation into a smoothing regularization problem, which is for channel estimation, and a ridge regression, which is for clutter suppression. A final solution is achieved by iterating between these two regularized regression problems. The numerical results show that the proposed method can effectively estimate the channel distortion and can significantly improve the performance of the clutter suppression compared with the conventional ECA.