Phase-Mode Circular Multi-channel Hydrophone with Super Directivity

A new model for the super directional circular multi-channel hydrophone based on the concept of phase-mode is presented in this paper. In this new model, the phase-mode strength calculated via boundary element method and the mode coefficients determined by desired directivity were used to obtain the directivity forming weights for each channel of the hydrophone. Therefore, the synthesized super directivity could be formed. The mathematical analysis of maximum directivity index for the phase-mode hydrophone is also presented. Computer simulations and water-tank experiments for the proposed hydrophone were carried out. The experimental results show that the phase-mode hydrophone owns a good super directivity, which is impossible for conventional methods using the same small-size hydrophone. For the low phase-mode order, the measured directivities are consist with the theoretical ones very well. For the cases of higher phase mode orders, the measured directivities are still much better compared with the conventional ones, although not match the theoretical ones perfectly due to the higher error sensitivity.