title: Characterization of an elastic target in a shallow water waveguide by decomposition of the time-reversal operator.
abstract: This paper reports the results of an investigation into extracting of the backscattered frequency signature of a target in a waveguide. Retrieving the target signature is difficult because it is blurred by waveguide reflections and modal interference. It is shown that the decomposition of the time-reversal operator method provides a solution to this problem. Using a modal theory, this paper shows that the first singular value associated with a target is proportional to the backscattering form function. It is linked to the waveguide geometry through a factor that weakly depends on frequency as long as the target is far from the boundaries. Using the same approach, the second singular value is shown to be proportional to the second derivative of the angular form function which is a relevant parameter for target identification. Within this framework the coupling between two targets is considered. Small scale experimental studies are performed in the 3.5 MHz frequency range for 3 mm spheres in a 28 mm deep and 570 mm long waveguide and confirm the theoretical results.
authors.affiliation: Laboratoire Ondes et Acoustique, Universite Denis Diderot Paris 7, UMRS CNRS 7587, ESPCI, 10 rue Vauquelin, 75231 Paris Cedex 05, France. franck.philippe@espci.fr
authors.forename: Franck D
authors.initials: FD
authors.lastname: Philippe
authors.forename: Claire
authors.initials: C
authors.lastname: Prada
authors.forename: Julien
authors.initials: J
authors.lastname: de Rosny
authors.forename: Dominique
authors.initials: D
authors.lastname: Clorennec
authors.forename: Jean-Gabriel
authors.initials: JG
authors.lastname: Minonzio
authors.forename: Mathias
authors.initials: M
authors.lastname: Fink
mesh_terms: D000162:Acoustics; D004548:Elasticity; D008962:Models, Theoretical; D009038:Motion; D013016:Sound; D013018:Sound Spectrography; D013232:Steel / Q000737:chemistry; D013499:Surface Properties; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D013232:Steel