A robust adaptive beamforming method based on iterative optimization algorithm

It is well known that the steering vector mismatch caused by estimating direction of arrival (DOA) error or array mutual coupling degrades severely the performance of adaptive beamforming. In this paper, we propose an adaptive robust beamforming algorithm to deal with this problem. The coupling coefficient between any two antenna elements can be calculated, and in the case of an uniform linear array, these coefficients can be represented by a symmetric Toeplitz matrix. The robust beamforming algorithm takes advantage of this specific structure of the symmetric Toeplitz matrix. Based on the criterion of maximum signal-to-interference-plus-noise ratio, the beamforming problem is transformed into an unconstrained optimization problem. A rough estimate of the DOA and power of desired signal are the only prior information of the proposed approach. The numerical simulations show that the proposed method can alleviate evidently the steering vector mismatch and ultimately improves the robustness of adaptive beamformers even encountering large DOA mismatch.