Beamforming for Small-Spacing Acoustic Vector Sensor Array Using Optimal Beampattern Synthesis Technique

Abstract

Traditional low-frequency acoustic senor arrays will always be very large and not easy to be implemented. So it is meaningful to study small-spacing underwater acoustic sensor arrays. The superdirectivity beamforming technique can achieve high array gains for sensor arrays with small apertures, and we study superdirectivity beamforming for small-spacing acoustic vector sensor (AVS) arrays in this letter. We use the beampattern synthesis technique and establish the optimization problem by both considering the approximation of the beampattern to a Dirac delta function and constraint for white noise gain of the beamformer. The superdirectivity beamformers for AVS arrays are then obtained by solving this optimization problem. Simulation results show that the proposed method can achieve high directivity factors for small-spacing AVS arrays. Experimental results of an AVS array with aperture being less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{1}\,\text{m}$</tex-math></inline-formula> are also presented in this letter and around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{7.9}\,\text{dB}$</tex-math></inline-formula> array gain is obtained at the frequency of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{200}\,\text{Hz}$</tex-math></inline-formula> .