Passive phase conjugation for underwater communication

Active phase conjugation requires an array capable of both transmitting and receiving. A field incident on the array can be refocused both in space and time at the location of the original source. To do acoustic communication, an additional step in the processing is introduced; prior to backpropagation, the measured probe field is first convolved with a data stream. The direction of communication is from the active array to the location of the original point source. By contrast, in passive phase conjugation [D. R. Jackson et al., J. Acoust. Soc. Am. 108, 2607 (2000)] the direction of communication is from the point source to the passive array. Further results from an experiment conducted in Puget Sound are presented. The effects of array curvature and truncation are discussed. [Work supported by ONR.]