Iterative time reversal in the ocean

The iterative time-reversal process focusing on the strongest scatterer in a multitarget medium has been described theoretically in terms of eigenvalu es and eigenvectors of a time-reversal operator K*K in ultrasonics [Prada e t. al. J. Acoust. Soc. Am. 97, 62-71 (1995)]. In this paper, we extend the concept of iterative-time-reversal to waveguide propagation in the ocean. F or a single target, the iterative time-reversal process results in a minor improvement in spatial focusing. However, data from a recent experiment in the Mediterranean Sea [Kuperman et al., J. Acoust. Soc. Am. 103, 25-40 (199 8)] illustrates the importance of the waveguide and source transducer chara cteristics even in the single target case. When the ocean contains several reflectors, iterative time-reversal focuses on the target corresponding to the largest eigenvalue of the time-reversal operator, which depends not onl y on the reflectivity of the targets, but also on the complex propagation e ffects between the targets and time-reversal mirror. Analysis of the experi mental data for a single target and simulation results with multiple target s in the ocean are presented. (C) 1999 Acoustical Society of America. [S000 1-4966(99)02306-1].