Undersea remote sensing with acoustic communications waveforms

Coherence under varied circumstances is compared for two classes of waveform: linear FM chirps (a conventional sonar waveform) and binary phase shift keyed messages (a conventional acoustic communications waveform). All but the waveforms' time domain structure is kept constant during the comparison. Both modeled results as well as data from a large undersea array of hydrophones are presented. Parameters considered include bandwidth, pulse length, range from transmitter, and ray path. We find that if the ray interacts with the ocean surface, the resulting Doppler shift quickly destroys coherence for the BPSK waveform, which is highly Doppler intolerant. However, additional processing can mitigate this issue, and remote sensing with acoustic communications networks is a topic of interest.