Electronic steering for a microphone array by sub-band phase compensation

Directional microphones are widely used in spatial filtering applications. The directivity and steering capabilities are usually realized using arrays of sensors connected to a digital processor. In general, these techniques are very complicated and expensive. In this work a continuous-time electronic steering technique for microphone array based on sub-band phase compensation is presented. It can be realized by means of analogue electronics, selecting gain and phase value for each sensor as a function of look direction. First, the spatial performance of the proposed microphone is analyzed at a single frequency. Then, the frequency range of interest is divided into several sub-bands according to the desired frequency resolution, and the weights are designed independently for each sub-band frequency. The paper presents a theoretical formulation of the proposed methods, and a numerical simulation showing that the performance of the proposed microphone is comparable to that of a conventional delay-and-sum beamformer.