Frequency invariant beamformer using a single set of IIR filter coefficients and multirate techniques

A technique for designing a frequency invariant (FI) beamformer using multirate 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 bandwidth of design. A single set of IIR filter coefficients is obtained from the equivalence between the aperture distribution and the filter response. In addition, interpolation with trapezoid integration is applied to enhance the frequency invariant pattern approximation. Beam steering is performed through the use of additional delays for each antenna element