Inverse problem in wave scattering with an acoustic time-reversal mirror

A time-reversal mirror (TRM) utilizes time-reversal invariance of the wave equation. Acoustic TRM are made of large transducer arrays allowing the incident acoustic field to be sampled, time-reversed, and re-emitted. Such a process allows an original way of studying acoustical sources. This paper describes an application of TRM to the characterization of an extended scatterer illuminated by a broad band pulse. The ability of TRM to time-reverse separately each scattered wave permits one to isolate spatially and temporally the equivalent sources of the extended scatterer. We investigate more particularly the problem of a cylindrical scatterer: we show that TRM allows to characterize simply the different sources of backscattered waves and especially the mode conversion of the incident wave into circumferential waves. Besides, we show that the iterative time reversal process allows one to generate any particular circumferential wave