Broadband Beamforming Using 2D Trapezoidal Filters and Nested Arrays

A broadband beamforming technique using 2D trapezoidal filters (TFs) and nested arrays is proposed. Each subarray feeds into a subband beamformer processing an octave frequency band. Using subsampling in space and time all frequency subbands are transformed into the same frequency range in the 2D frequency domain. This allows using the same 2D trapezoidal filter design for all subbands. The advantage of using nested arrays is that the effective aperture for low temporal frequencies is larger than in the case of using a Uniform Linear Array (ULA) with the same number of array elements. This leads to a better spatial selectivity at low frequencies than using ULAs. The performance of the proposed beamformer is illustrated and evaluated using simulations.