Analysis of split-beam spatial coherence statistics for discerning compact from non-compact littoral sonar clutter

Abstract

Active sonar systems operating in the littoral environment are often reverberation-limited, which impacts detection performance by reducing the effective signal-to-noise ratio. Additionally, irregularities in the environment lead to excessive false alarms commonly referred to as sonar clutter. Clutter is found in all environments, but shallow-water littoral regions have been observed to be especially challenging. The irregularities that cause sonar clutter can have spatial scales ranging from much smaller to much greater than the dimensions of the sonar resolution cell. This talk will discuss physical interpretation and experimental assessment of signal statistics related to the transverse horizontal spatial coherence of reverberation estimated via split-beam processed data obtained from a line array. Multiple boundary interaction in shallow water depths and spatial variability randomize reverberation and may allow the use of Gaussian noise models. While match-filtered signal intensity is an optimal detection statistic in a Gaussian noise environment, spatial reverberation coherence statistics may provide complimentary information of the spatial scale of clutter features relative to the width of the beampattern. It is found these statistics may be used to help discern clutter types that are spatially compact from those that are non-compact when compared to the width of the sonar resolution cell.