DOA Estimation Considering Effect of Adaptive Clutter Rejection in Passive Radar

In a passive radar, when the reference antenna is set to receive a direct-path signal, target signals will be inevitably mixed in the reference channel due to the antenna pattern. In this case, adaptive clutter cancellation in the temporal domain will affect the target steering vector due to the correlation between the target signal in the reference and surveillance channels, which results in a direction of arrival (DOA) estimation bias. The spatial-domain adaptive clutter rejection will also cause a similar influence. To solve this problem, in this article, we derive and analyze the effect of the adaptive clutter rejection on the target steering vector. Two kinds of DOA estimation methods are hence proposed to correct the estimation bias. The applicable boundaries of these two methods are also discussed. Simulations and real radar data show that the proposed methods can correct the DOA bias caused by adaptive clutter rejection, thereby improving the location accuracy in a passive radar.