Reverberation rejection via modeforming with a vertical line array

Abstract

The concept of modeforming with a vertical line array for active target detection in a reverberation-limited shallow-water environment is explored. The concept is based on the hypothesis that, in certain environments, the reverberation field is due to subbottom scattering and the reverberant energy is carried by the higher order modes; on the other hand, the targets in the water column are contained in the lower order modes. Under these conditions, isolation of a low-order mode, or a selected set of modes, with a vertical array could substantially increase the target-to-reverberation ratio. The optimum mode depends greatly on the environmental conditions and the depth of the target. Modeforming is achieved by deriving a spatial filter function that depends on the receiving array and the local environment.