Robust beamformer weight design for broadband matched-field processsing

Matched-field beamforming has been proposed for localizing wideband acoustic sources in uncertain underwater channels. While adaptive matched-field beamforming provides adequate sidelobe suppression for stronger sources, at low signal-to-noise ratios it converges to its quiescent response, in this case the Bartlett beamformer, which has unacceptably high sidelobe levels. In this paper, a design method is presented for reducing non-adaptive matched-field beamformer sidelobe levels given a sufficiently large observation-time-bandwidth product. The proposed α-beamformer incoherently averages narrowband matched-field beamformer output power over the signal band after a trade-off has been performed at each frequency to achieve better sidelobe suppression at the expense of some reduction in gain against diffuse noise. Simulations and results with Mediterranean vertical array data indicate that the wideband α-beamformer can provide improved sidelobe suppression versus conventional techniques