Order calibrated functional beamforming for constant mainlobe width

This paper introduces a beamformer with constant mainlobe width over a given frequency range based on the well-known Functional Beamforming. In fact, one of the main issues with Conventional and Functional Beamforming is the worsening of spatial resolution towards lower frequencies. The idea pre-sented here is to exploit the order (exponent in its typical formulation) of Functional Beamforming as a leverage to maintain the same mainlobe width for different analysis frequencies. A strategy for accurately measure the mainlobe size is described and exploited for characterizing any array used in the beamform-ing analysis. An order calibration procedure, which boils down to the estimation of two fitting coefficients describing the proper beamformer order, is proposed. The procedure resulted useful to achieve a constant mainlobe size across a given frequency range. The validity of the whole approach is demonstrated on both synthesized and experimental data.(c) 2022 Elsevier Ltd. All rights reserved.