Multipath compensation in shallow-water environments using a virtual receiver

An acoustic technique for compensation of signal distortion due to propagation is developed in analogy with an astronomical technique in which light from a bright "guide star" is used to correct atmospheric aberration of weaker objects that are nearby in the angular sense. The acoustic technique investigated here uses a vertical array to receive both the signal from a broadband "guide source" and an unknown "objective source" which propagates over a partially shared path. The algorithm is a spatial-temporal cross correlation of the two signals and is termed a "virtual receiver" as the output approximates the signal that the unknown source would produce at the location of the guide source. By strategically locating the guide source, many of the distorting effects of an unknown propagation region can be removed, including mode coupling and multipaths. The virtual receiver can also be combined with matched field processing techniques to estimate the unknown source location. Results are given for a variety of numerical experiments in both the time and frequency domains. The numerical simulations are used to illustrate the virtual receiver algorithm in range-dependent shallow water environments exhibiting lossy propagation and mode coupling. (C) 1997 Acoustical Society of America. [S0001-4966(97)04011-3].