Filter-and-sum beamformer with adjustable filter characteristics

In this paper we introduce a polynomial filter structure for filterand-sum beamforming applied to microphone array application. The structure is a multi-dimensional extension of well-known Farrow structure, which has mainly been used for fractional delay filtering and interpolation of 1-D signals. The proposed method enables an easy, smooth, and efficient control of beamforming filter characteristic by adjusting only a single control variable e.g. for dynamic beam steering. The optimization method for polynomial beamforming filter design is presented and illustrated with simulations of beamforming filter characteristics. The design example is given for a linear array of four omni-directional microphones and a polynomial FIR filter with 20-tap delay lines.