Virtual time-reversal processing for source localization in shallow water

Matched-field processing (MFP) is a forward propagation process that consists of systematically placing a test point source at each point of a search grid, computing the replica vectors on the array and then correlating these replicas with the data from the real source. It will cost much time to calculate all these replica vectors corresponding to the search grids. Time-reversal processing (TRP) is an implementation of MFP where the ocean itself is used to construct the replica field. This paper introduces a virtual time-reversal processing (VTRP) that is implemented electronically at the receiver array and simulates the kind of processing that would be done by an actual TRP during the reciprocal propagation stage. Apart from MFP, VTRP is a back-propagation process which exploits the properties of reciprocity and superposition. Thus, the calculation of the replica surface generated by each virtual source at the corresponding array element location can be speeded up by matrix manipulation. As a result, the localization surface of VTRP can be formed faster than that of MFP. The performance of VTRP for source localization is validated through the numerical simulations.