Performance analysis for a short vertical array in a shallow-water waveguide

Abstract

Vertical line array (VLA) has been widely used for field data collection in underwater acoustics. The performance of VLA strongly depends on: (1) the signal processing approach used, (2) the environmental knowledge, (3) the signal-to-noise ratio (S/N), and (4) the configuration of the array (length, position, curvature). In this paper, we concentrate our investigation on the length effect. Theoretical analysis has been done for a short array in a Pekeris shallow-water waveguide. For lower frequency in shallow water, the information provided by a VLA can be described by the capability of mode decomposition, which is determined by the spectrum of the eigenvalue of the ‘‘covariance matrix’’ of the field sampled by the VLA. The approximate decay behavior of the spectrum is calculated analytically for short array. It is shown that the estimated eigenvalues are very close to the exact eigenvalues. The indicator of the performance used in this paper is the number of ‘‘S,’’ which represents the dimension of the ‘‘signal space,’’ and can be easily determined by the spectrum decay law.