Theoretical Model and Experiments of Focused Phased Array for Cross-Medium Communication in Misaligned Transmitter/Receiver Scenarios

Direct communication across the water-air interface has attracted wide attention because of its potential applications in integrated air-sea networking. In this article, three different cross-medium communication systems have been proposed, including line-of-sight (LOS) optical links, laser-induced acoustic (LIA) systems, and translational acoustic radio frequency (TARF) systems. However, LOS optical links are sensitive to turbid water, misalignment of the transmitters/receivers, and the influence of surface waves. LIA systems are unstable with poor repeatability. TARF systems require the alignment of transmitters/receivers. Moreover, in situations where the location of detection points is required to be frequently moved for flexible communication, LOS optical links, and TARF systems both failed. This article proposes a cross-medium focused phased array (CMFPA) model, which is a multiple-input single-output system, to enlarge the detection area and increase the overall wave amplitude at the water surface. Theoretical analyses and experimental results indicate that the CMFPA can relax the requirement of precise alignment between communication nodes and improve performance in cross-medium communication when compared to a single-input single-output system. The study is expected to provide a foundation for cross-medium communication between underwater and airborne nodes in misaligned transmitters/receivers scenarios.