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Retrofocusing of acoustic wave fields by iterated time reversal
KTH, Superseded Departments, Electromagnetic Theory.ORCID iD: 0000-0001-7269-5241
2004 (English)In: SIAM Journal on Applied Mathematics, ISSN 0036-1399, E-ISSN 1095-712X, Vol. 64, no 6, 1954-1986 p.Article in journal (Refereed) Published
Abstract [en]

In the present paper an iterative time-reversal algorithm that retrofocuses an acoustic wave field to its controllable part is established. For a fixed temporal support, i.e., transducer excitation time, the algorithm generates an optimal retrofocusing in the least-squares sense. Thus the iterative time-reversal algorithm reduces the temporal support of the excitation from the requirement of negligible remaining energy to the requirement of controllability. The time-reversal retrofocusing is analyzed from a boundary-control perspective where time reversal is used to steer the acoustic wave field towards a desired state. The wave field is controlled by transducers located at subsets of the boundary, i.e., the controllable part of the boundary. The time-reversal cavity and time-reversal mirror cases are analyzed. In the cavity case, the transducers generate a locally plane wave in the fundamental mode through a set of ducts. Numerical examples are given to illustrate the convergence of the iterative time-reversal algorithm. In the mirror case, a homogeneous half space is considered. For this case the analytic expression for the retrofocused wave field is given for finite temporal support. It is shown that the mirror case does not have the same degree of steering as the cavity case. It is also shown that the pressure can be perfectly retrofocused for infinite temporal support. Two examples are given that indicate that the influence of the evanescent part of the wave field is small.

Place, publisher, year, edition, pages
2004. Vol. 64, no 6, 1954-1986 p.
Keyword [en]
time reversal, retrofocusing, wave splitting, acoustic, mirrors
National Category
URN: urn:nbn:se:kth:diva-23761DOI: 10.1137/s0036139903426964ISI: 000224122400006ScopusID: 2-s2.0-11044226943OAI: diva2:342460
QC 20100525 QC 20111102Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2011-11-02Bibliographically approved

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Jonsson, B. Lars G.
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