A High Frequency Phase Conjugation Array

A phase conjugation array (time-reversal mirror) time reverses the incident signal and precisely returns it to its original source location. A high frequency (~3.5 kHz) phase conjugation array (HFPCA) has been designed, fabricated, and deployed at sea in two experiments (July 1999 and May/June 2000) conducted jointly with the NATO SACLANT Undersea Research Centre. The HFPCA consists of 29 source/receive transducers equally-spaced over an aperture of 78 m and operating nominally in the 3-4 kHz band, an underwater pressure case containing the source/receive electronics, and a surface buoy providing battery power, system control, and wireless local area network (LAN) connectivity. On receive, the sampling rate for each channel is fs = 12 kHz. On transmit, an arbitrary waveform can be transmitted independently from each transducer (10.7 sec maximum duration) at a maximum source level of 180 dB re 1 μPa per transducer. The wireless LAN enables received data segments to be telemetered to the support ship up to 30 km away for immediate processing. Transmit waveforms (e.g. time reversed versions of the received data segments) also can be telemetered to the surface buoy for downloading into the electronics and transmission.