Using phase conjugation for underwater acoustic communication: Design guidelines

Broadband phase conjugation using a time-reversal mirror may be used to focus acoustic waves in inhomogeneous media. This technique has been successfully applied in the ocean over distances of a few kilometers, stimulating research into possible applications. In this paper, a time-reversal mirror is considered as a device for mitigating intersymbol interference in coherent communication, hence reducing the complexity of underwater receivers. Approximate expressions are obtained relating its focusing power with key array and environmental parameters. These provide guidelines for designing actual phase-conjugate arrays. Results obtained for a monochromatic source are then extended to broadband signals used in digital communication in order to predict the evolution of intersymbol interference in the vicinity of the focal point.