Novel robust beamformers for coherent interference suppression with direction-of-arrival estimation errors

Two novel robust beamformers for the reception of a desired signal in the presence of both coherent interferences and direction-of-arrival (DOA) estimation errors are proposed. In the first method, the worst-case constraint and the soft-response constraint (WCSC) are combined together to maintain a distortionless response for the desired signal, while suppressing the coherent interferences with robustness against the DOA estimation errors. Further improvement of the output signal-to-interference-plus-noise ratio (SINR) for the WCSC beamformer can be achieved by removing the desired signal in the received data with a subtraction operation, which is the second method, denoted as SWCSC. In this method, a new array data vector is obtained by first dividing the original data vector into two sub-vectors and then subtracting one sub-vector from the other. From this new data vector, the optimum weight coefficients are obtained and then applied to one of the original sub-vectors. Simulations show that the proposed beamformers can achieve a much better performance in terms of output SINR than the existing ones.