An optimal robust adaptive beamforming in the presence of unknown mutual coupling

An optimal robust adaptive beamformer in the presence of unknown mutual coupling is proposed. In this proposed beamformer, envelopes of the received signals in the presence of unknown mutual coupling and their corresponding powers can be estimated by utilizing the Toeplitz characteristics of the mutual coupling matrix. Both of them are used to reconstruct the interference-plus-noise covariance matrix in a novel expression. A subspace orthogonal to the interference space can be obtained by performing the eigenvalue decomposition on this reconstructed matrix. Hence, the desired signal and the noise are retained by projecting the observed data to this orthogonal space. Finally, the optimal weight vector is obtained by passing the desired signal with the maximum output power criterion. The proposed method maintains excellent performance in the presence of unknown mutual coupling and the simulation results are consistent with the theoretical analysis.