Modified Robust Capon Beamforming with Approximate Orthogonal Projection onto the Signal-Plus-Interference Subspace

Abstract

In this paper, a new robust adaptive beamforming technique based on a modification of the robust Capon beamforming approach is introduced. It is shown that this technique leads to an approximate eigenspace projection-based array steering vector estimation. The steering vector is estimated as an approximation for the orthogonal projection of the presumed steering vector of the desired signal onto the signal-plus-interference subspace. Also, it is demonstrated that the optimal diagonal loading factor corresponds to the minimum of the estimated beamformer output power. Furthermore, the formulation of the proposed method provides the possibility of estimating the direction-of-arrival of the desired signal. This estimation is then used to update the presumed steering vector. An important virtue of the proposed method is its better or comparable performance with less computational complexity than the recent existing methods.