4aSA1. Angular dependence of Bloch wavepackets.

Session: Thursday Morning, May 16

Time: 8:15

Author: Charles F. Gaumond
Author: David Drumheller
Location: Naval Res. Lab., Code 7140, Washington, DC 20375-5350


The contribution to an echo by a particular scattering mechanism, which occupies a specific region in the time-frequency or time-scale domains, is defined as a wavepacket [N. Yen, J. Acoust. Soc. Am. 81, 1841--1850 (1987)]. Previous studies have isolated wavepackets generated by specular reflection, Bragg reflection and Bloch waves in backscattered echoes from a ribbed, finite cylinder at a few discrete target aspect angles. For this target, the echoes mainly contain components from specular reflection and Bloch waves in the frequency region near ka(approximately equal to)5. These two kinds of wavepackets are experimentally extracted in the time-scale domain over the angular range from 10(degrees) to 70(degrees). The time extents and spectra of these wavepackets are shown to vary with target aspect angle. This angular dependence is shown to be related to physical mechanisms. [Work supported by NRL 6.2 funds.]

from ASA 131st Meeting, Indianapolis, May 1996