An Experiment On Passive Synthetic Aperture Time Reversal Communications In Shallow Water

Abstract

Time reversal can focus in both time and space. The temporal focusing properties have been used in underwater acoustics communications. Typical passive time reversal communication experiments use a vertical array of receivers and a sound source. The property of a horizontal time reversal array that it focuses well in the temporal domain indicates the utilization of synthetic aperture time reversal. Passive synthetic aperture processing repeats emitting same signals during the cruising and records the received signal using one or more receivers. Passive synthetic aperture time reversal communication techniques are presented and applied to results from a sea trail. The experiment consisted of a towed hydrophone and a vertical array. During the experiment, a probe signal is emitted to sample the transmit function then be used by time reversal processing. Due to the moving of the hydrophone, Doppler shift compensation and receive wave forms synchronization must be performed before the time reversal processing. The signal‐to‐noise ratio is increased and the temporal side lobes are decreased in the time reversal process. Additional communication algorithms can be appended after the time reversal process to increase performance. The result from the at‐sea experiment confirms the ability of passive synthetic time reversal communications.