Frequency invariant beamformer using a single set of IIR filter coefficients

A technique for designing a frequency invariant (FI) beamformer using multirate and infinite impulse response (IIR) zero-phase filters is presented. Such a frequency invariant beamforming is applied to a non-uniform linear array (NULA), resulting in far-field responses that are approximately constant over the wide design bandwidth. A single set of IIR filter coefficients is obtained from the equivalence between the aperture distribution and the filter response. Beam steering is performed through the use of additional delays for each antenna element.