Iterative Calibration and Direction-of-Arrival Estimation for Uniform Circular Arrays affected by Mutual Coupling

This letter presents an iterative method to estimate directions of arrival (DOA) of plane wave signals impinging on a Uniform Circular Array (UCA), accounting for the possible presence of mutual coupling (MC). After a tailored transformation that maps the data gathered by the UCA into a Virtual Uniform Linear Array (VULA), the mutual coupling effect is modeled via gain and phase errors affecting the resulting VULA. Therefore, a Coordinate Descent (CD) iterative procedure is designed to approximate the maximum likelihood (ML) estimates of the VULA calibration factors and of the sources power. Leveraging the resulting calibrated VULA array manifold, the DOAs are obtained using the Estimation of Signal Parameters via Rotational Invariant Technique (ESPRIT). Simulation results demonstrate the superior performance of the proposed method with respect to the baseline uncalibrated ESPRIT, in terms of DOA estimation accuracy in the presence of mutual coupling, making it viable to be implemented in actual sensing systems due to its moderate computational complexity.