Active waveguide Green's function estimation with application to time-reversal focusing without a probe source in a range-independent waveguide

International audienceA method is introduced for using a pair of vertical line transducer arrays (VLAs) to produce time-reversal (TR) foci at any location in a range-independent shallow-ocean waveguide without the need for a probe source. Modal theory suggests that the acoustic response sampled between a pair of VLAs separated by a range R can be repeatedly iterated to estimate the acoustic response at ranges that are integer multiples of R. When combined with the frequency-based variable-range-TR method, the process results in a virtual sampling of the acoustic response over long distances that can be applied to both passive and active shallow-ocean acoustic imaging. Here, the technique is applied to active time-reversal focusing. Array geometry effects are explored and simulation and experimental results are presented