ASA 125th Meeting Ottawa 1993 May

2aUW12. Scattering of superpositions of localized waves from spheres.

Des Power

Rod Donnelly

Faculty of Eng., Memorial Univ., St. John's, NF A1B 3X5, Canada

Localized wave (LW) solutions of the homogeneous wave equation can represent either focused or extended pulses, depending on the choice of a free parameter present in the solution. One can form finite energy superpositions, with respect to this parameter, and one such superposition, known as a modified power spectrum (MPS) pulse, has been extensively studied [R. W. Ziolkowski, Phys. Rev. A 39, 2005--2032 (1989)]. In particular, the enhanced near-field LW propagation effect has been demonstrated by others, in the context of multi-time-derivative transmit/receive systems [R. W. Ziolkowski and D. K. Lewis, J. Appl. Phys. 68, 6083--6086 (1990)]. The LW solutions are broadband, so it is perhaps to be expected that one could use this property, along with the enhanced focusing characteristic, to extract target parameters when scattering LW superpositions from objects. The acoustic MPS pulse backscattered spectra from a number of different sized steel and aluminum spheres will be presented. It will be demonstrated that these spectra can be used to extract target size information. [Work supported by NSERC.]