Novel robust adaptive beamforming against unknown mutual coupling

Mutual coupling effects among the array elements can degrade the performance of the beamformer seriously. In this paper, we propose a novel robust adaptive beamforming method, which is robust against unknown mutual coupling. The main idea is to reconstruct the interference-plus-noise covariance matrix (IPNCM) with the estimated eigenvector and eigenvalue corresponding to the interference. The eigenvector lies in the intersection of two special subspaces. The first subspace is the signal-plus-interference (SPI) subspace got from the sample covariance matrix (SCM). The second subspace, which is interference subspace, can be obtained by integrating the conduction matrix in each interference angular sector. According to the correlation between the estimated eigenvector and SPI subspace, the eigenvalues corresponding to each interference are determined. Therefore, the IPNCM is reconstructed. The desired signal steering vector (SV) is estimated by a similar method. Simulation results show that the proposed beamformer outperforms other methods in the presence of unknown mutual coupling.