Beamforming for Circular Array Based on Mode Decomposition of Sound Field

A general mode decomposition beamformer for circular array is presented in this paper. In the proposed beamformer, the mode components of incoming wave are extracted via decomposing the sound field around the circular array. Then the synthesized beampattern is obtained by using the mode components and corresponding mode coefficients. The framework of the beamformer which we call it Mode Decomposition Beamformer (MDB for short) is presented. In the framework, the beamforming for the circular array is composed of three independent sections. Due to the mode decomposition for the sound field, we succeed in applying the linear array weights in the beamforming for circular array, such as Dolph-Chebshev weights, and we name the corresponding beamformer DC-MDB. The results of computer simulations and lake-experiments for a 24-element ring array indicate that the measured beampatterns obtained by MDB are consistent with the desired beampattern. So are the results of the DC-MDB case. Moreover, the obtained measured beampatterns are much better than the conventional beampatterns.