Robust adaptive nulling in matched field processing

Abstract

Nulling out sources of interference is a major goal of adaptive array processing. For moving interferers, null-broadening is a useful technique to reduce the interference. A null-broadening approach has been recently developed for planewave beamforming [R. J. Mailloux, Electron. Lett. 31, 771–772 (1995)] [M. Zatman, ibid. 31, 2141–2142 (1995)] to cover the angular extent of the motion. One way to achieve this is to introduce the effects of dispersion into a covariance matrix, which is equivalent to averaging the covariance matrix over a finite bandwidth in frequency. In this study, the null-broadening approach is extended to the matched field processing (MFP) in an ocean waveguide, based on an MV processor with a white noise constraint. In particular, the null-broadening in range is accomplished through using waveguide invariant properties. Simulations as well as the SWELLEX-96 experimental data clearly demonstrate the null-broadening effect.