### ASA 125th Meeting Ottawa 1993 May

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

**Des Power
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Rod Donnelly
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*Faculty of Eng., Memorial Univ., St. John's, NF A1B 3X5, Canada
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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.]