Impact of the ocean acoustic transfer function on the coherence of undersea propagations

Multipath propagation, in conjunction with source motion, creates a splitting and spreading of the received source-signal energy over the time register time scale-factor (ambiguity) plane. This splitting of the received signal energy is manifested as correlation interactions between both; the set of eigenray signal arrivals (comprising the multipaths) at each receiving sensor, and the set of eigenray signal correlation pairs comprising two (or more) sensors. The more tightly the sets of eigenray signals are clustered in the ambiguity plane, the stronger will be the signal component interactions at each sensor and the less will be the expected correlation degradation between sensors. However, the greater will be the variance. Conversely, the more diffuse the clustering, the weaker will be the signal component interactions and the greater will be the expected intersensor coherence degradation. Also, the less will be the variance. Criteria which define the degree of signal component interactions in terms of the signal and the ocean transfer function parameters have been defined and are displayed in graphical form.