A study on the focusing property of time reversal waves in shallow water

The focusing property of time reversal waves (phase conjugate waves) in shallow water or the deep sea has been discussed based on simulations of the normal mode method. In this study, the focusing property of time reversal waves was verified through tank experiments and it was concluded that time reversal waves enable acoustic waves to be converged to the focus. Further, the simulation results qualitatively concurred with the experimental results. This study also investigated how the configuration of the elements of the Time Reversal Mirror (TRM) array affects the focusing property, and the following matters were clarified: The signal received at the focus is not disrupted when the number of elements in the TRM array is reduced. Even if the TRM array is tilted or the heights of its elements are steadily shifted, the signal received at the focus is not disrupted. However, if the tilting or the height-shifting is not stationary, the time reversal waves lose their focusing property. Even a horizontal TRM array can generate time reversal waves if it is of adequate length.