Spatial resolution of time-reversal arrays in shallow water

A series of time-reversal experiments was performed in shallow water includ ing a range-dependent slope environment. Time-reversal arrays implemented w ith center frequencies of 445 and 3500 Hz achieved sharp focal regions up t o ranges of 30 and 13 km, respectively in 110-130-m shallow water. In this paper, resolution expressions are derived using an image method to describe the focal sizes achieved with time-reversal arrays in various ocean enviro nments. Analysis for the measured data indicates that the focal size approa ches the diffraction limit of an array for given waveguide conditions, i.e. , waveguide geometry and attenuation. The measured focal size has implicati ons for the maximum achievable resolution of linear matched-field processin g which is a computational implementation of the time-reversal process. (C) 2001 Acoustical Society of America.