Study of the relative sonar performance of incoherent and coherent processing against echo fading in shallow water

The problem of echo fading and the inherent time- and frequency-diversity reception provided by coherent processing is discussed, leading to a description of an experimental investigation into the shallow-water performance of a coherent processor. A statistical analysis of the results clearly demonstrates the benefits of coherent processing in reducing the effects of echo fading and providing a significant improvement in the probability of detection of a target sphere compared with that provided by a simple energy detector system of equivalent bandwidth and, hence, nominally equivalent reverberation-limited performance.