Maximum‐likelihood angle estimator for multi‐channel FM‐radio‐based passive coherent location

Frequency‐modulation‐based (FM‐based) passive coherent location (PCL) systems can estimate the target location/velocity by exploiting a single FM channel. In order to improve the performance of PCL systems, multi‐channel‐single‐transmitter setup‐based PCL systems have been studied recently. However, it has not yet been considered for direction of arrival estimation based on the multi‐channel configuration. Thus, the authors propose a maximum‐likelihood angle estimator exploiting the multiple FM‐radio channels and derive the Cramer‐Rao bound for verifying the convergence of the proposed method in the sense of root‐mean‐square error (RMSE). In addition, they propose a target association algorithm for solving the ambiguity problem in selecting the steering vectors of each target. Computer simulations are included to show the estimation performance of the proposed method and to compare the RMSE of the single‐channel case with that of the multi‐channel case.