ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

2aUW2. Theoretical approaches for computing FAT spreads.

Diana F. McCammon

Appl. Res. Lab. and the Graduate Prog. in Acoust., Penn State Univ., P.O. Box 30, State College, PA 16804

FAT (frequency, angle, and time) spreading is approached theoretically through the Helmholtz integral equation for scattering from random rough surfaces. Using the Kirchhoff approximation, angle spread is readily found to be related to the probability of surface slopes. Various approximate evaluations are discussed for modeling time spread, from numerical ray tracing to integrals over pulse shapes. Solving for the half-power points of the intensity shows the link between angle and time spread. Frequency spread functions are discussed, illustrating the difficulty of using Fresnel phase approximations for higher-order corrections to the Doppler shift.