Designs and implementations of broadband beamformers

Designs and implementations of broadband beamformers are reviewed and discussed. Broadband beamforming includes Discrete Fourier Transform (DFT) implementation of a frequency-domain beamformer and Finite Impulse Response (FIR) implementation of a time-domain beamformer. The designs of weights at each frequency bin for the DFT beamformer and that of FIR filters associated with each sensor for the FIR beamformer are introduced. Performance analysis and comparisons of several typical approaches to them are presented. A unified approach, i.e., multiple-constrained approach, to narrow-band beamformer is provided and is extended to the FIR implementation of broadband case. The unified approaches include the existing individual approaches as their special cases, which leads to much more flexible designs. Design examples of broadband robust adaptive beamformer with constant mainlobe response and controlled sidelobes are given to illustrate the behavior.