Transmission intensity in shallow oceans, and implications for passive tracking

Abstract

The behavior of incoherent total‐field intensity is considered for a moving cw source in shallow water. The ocean channel is assumed isospeed, with a planar perfectly reflecting surface and a planar lossy bottom. The source is located at constant depth on a linear path, and the receiver is fixed on the bottom. An expression for incoherent total‐field intensity is derived in terms of source‐motion and environmental parameters. For a bottom with uniform loss per ray reflection, an approximation for intensity using special functions is developed and analyzed. The behavior of this novel approximation with respect to variations in source parameters such as range, depth, and speed, as well as bottom loss variations, suggests its usefulness for prediction of source motion. Two properties of the approximation, peak curvature and peak width, are selected as source motion descriptors. Both are shown to be relatively sensitive to changes in source parameters and insensitive to bottom loss variations. We apply our descriptors to an example, and discuss their use in supplementing existing passive tracking methods. [Work supported by ONR.]