A frequency-invariant beamforming method for a logarithmically arranged biconical vector hydrophone array

To address the low element utilization of biconical arrays in ship noise measuring systems, this study proposes a logarithmically distributed biconical array configuration and a corresponding constant beam width beamforming (CBB) method. The method begins by calculating optimal element positions using the continuous array beam pattern equation. Subsequently, a compensation function is derived to achieve a frequency-invariant beam pattern from the modal-domain beam pattern equation. Finally, the compensation function is converted into a filter to achieve CBB. The effectiveness of the proposed method is validated through simulation experiments. Compared to the traditional nested array method, the proposed approach achieves at least 6 dB of additional array gain. The proposed beamforming method is decoupled from the weighted vector design in traditional beamforming problems. This allows users to design a beam pattern based on engineering requirements while ensuring frequency invariance. Furthermore, the proposed method can be applied to vector arrays, resulting in better performance than traditional scalar arrays. The proposed method reduces broadband processing errors by over 45% compared to the nested method, making it suitable for various broadband array signal processing scenarios. These include measuring the radiated noise of underwater targets, estimating the arrival direction of broadband waves, and identifying underwater targets.