Abstract:

The efficiency of an iterative time reversal process in the ocean has been demonstrated in an experiment conducted in the Mediterranean Sea during April 1996. [See Kuperman et al. in this session.] The iterative time reversal process consisted of initiating a 50-ms pulse with equal amplitudes on all elements from SRA to VRA, capturing the signal at 75-m depth on a single hydrophone of VRA, and retransmitting it from SRT at the same depth to SRA, reversing the received signal in time and retransmitting it from all the SRA sources back to VRA. This process was repeated many times over an hour. Although this was not the intended mode of operation of iterative phase conjugation as in the free-field case with many scatterers [Prada et al., J. Acoust. Soc. Am. 90, 1119--1129 (1991)], it shows that an iterative process can enhance the focusing of a single target in the ocean. Comparisons of data with simulations and theoretical analysis will be presented and discussed.