Propagation focusing in the context of clutter statistics.

Abstract

Fluctuations in reverberation (clutter) from scatterers at long range in shallow water can be affected by many mechanisms. Their statistics, in particular the scintillation index, depend not only on the statistics of the scatterers (their physical distribution, shape, orientation, etc.) but on the outward and return propagation paths. Focusing effects due to forward scattering from weak undulations in the seabed will be presented. Existing Fresnel–Kirchhoff theory for monostatic, vertical incidence on a two‐dimensional surface is adapted to demonstrate the behavior of the intensity’s scintillation index in bistatic geometry. In addition, using a simulation of bistatic geometry and a one‐dimensional surface, the intensity statistics are extended to include autocorrelation function and probability distribution. Bistatic geometries include source and receiver moving with constant separation, and moving source with fixed receiver. Fairly modest vertical undulations can result in significant fluctuation due to reflection focusing with scintillation indices possibly greater than unity.