Broadband constant beamwidth beamforming for suppressing mainlobe and sidelobe interferences

The constant beamwidth beamforming is a key technique and research focus in the broadband array signal processing. However, most conventional methods can only satisfy constant mainlobe width and the performance will degrade severely when mainlobe and sidelobe interferences exist. To overcome this problem, a broadband constant beamwidth beamforming for suppressing mainlobe and sidelobe interferences is proposed. In the proposed method, the modified blocking matrices of different frequency bins are firstly constructed for mainlobe interference cancellation in the data domain, afterward, the minimum variance distortionless response (MVDR) beamformer and Zatman method are adopted to determine the adaptive weight vector of the reference frequency for robust interference suppression. Finally, the adaptive weight vectors of the other frequency bins are calculated using second-order cone programming (SOCP). The proposed method can form the same mainlobe width and null characteristics over the entire design frequency range. The effectiveness of the proposed method is verified by numerical simulations.