Experimental testing of passive phase conjugation for underwater acoustic communication

This paper describes the results of an underwater acoustic communications experiment to apply passive phase conjugation for the reception of a phase shift keyed digital data stream. The experiment took place in May 2000 in Puget Sound, Washington State. A single point source of 10 kHz bandwidth centered at 12.5 kHz transmitted over distances up to 2.5 km to a vertical array, first using a probe and followed by a data signal. The probe response was measured and used as a spatial matched filter or passive phase conjugator, by the receiver. Delay spread approached 20 msec with a very sparse structure. The experimental results show the efficacy of the spatial matched filter for removing the multipath introduced by the acoustic channel.