Adaptive Reverberation Nulling Using a Time Reversal Mirror

摘要

The major problem for active sonar systems operating in shallow water is the detection of target in the presence of severe bottom reverberation. The focusing capability of a time reversal mirror (TRM) suggest two different approaches to this problem. First, a TRM focuses acoustic energy on a target enhancing the target echo while shadowing the boundaries below and above the focus in an acoustic waveguide, thereby reducing reverberation. The resulting echo-to-reverberation enhancement has been demonstrated experimentally in the 3-4 kHz band in shallow water. The second approach is reverberation nulling to enhance target detectability since focusing and nulling are complementary. The idea is to minimize the acoustic energy incident on the corresponding scattering interface by applying an excitation weight vector which is orthogonal to the time-gated reverberation focusing vector. Both numerical simulations and experimental results illustrate the potential of reverberation nulling using a time reversal mirror.