Time/frequency spread for bistatic geometries

Abstract

The overall goal of this work is to develop a functional characterization of, and empirical models for, high-frequency, broadband acoustic propagation through a shallow ocean channel. One important aspect of this characterization is the time/frequency spread, which quantifies how much signals spread in time and frequency as they propagate. Because time and frequency spread are random quantities which vary from pulse to pulse, time/frequency spread must be characterized using a second-order statistic, e.g., the scattering function, which is the expected value of the mean-square spreading function. The scattering function has been measured in the following ocean environments: sandy gravel bottom, isovelocity sound speed profile (SSP); rough rock bottom, slightly downward-refracting SSP; and mud bottom, upward-refracting SSP. A statistical model for the scattering function is being developed for these environments based upon radial basis function decompositions of the scattering function estimates. The ultimate use of a scattering function model will be with simulation to assess and optimize acoustic receiver performance. [Work is sponsored by the Office of Naval Research Ocean Acoustics Program.]