A Novel Robust Wideband Beamformer With Frequency Invariance Constraints

A novel RB-WC-FI-FB (robust worst-case frequency invariance forward-backward) wideband beamformer is proposed in this paper. It is developed to improve the robustness against estimation errors of direction of arrival (DOA) and limited sample number, as well as reduce the number of constraints. By incorporating forward-backward estimation and worst-case performance optimization method into the linearly constrained minimum variance (LCMV) beamformer, the RB-WC-FB (robust worst-case forward-backward) beamformer is developed. However, there still exists a problem of over-constrained in the RB-WC-FB beamformer. To overcome this, a response variation (RV) element is introduced. Due to an increased number of degrees of freedom for interference suppression, a higher SINR can be obtained by the RB-WC-FI-FB beamformer. The RB-WC-FI-FB beamformer is formulated as a second-order cone (SOC) programming convex optimization problem that can be solved efficiently using interior point methods. Simulation results show that the proposed beamformer has higher SINR compared with earlier robust beamforming techniques.