Wireless underwater power and data transfer

This work investigates whether a contactless, wireless underwater coupling could be developed for underwater sensor networks. This requires the wireless transmission of power from the sensor hub to the transducer module, and the two-way wireless data communication between hub and transducer. Results from a trial deployment of systems with conventional waterproof couplings show that these are a major shortcoming of existing systems. Experiments are conducted which demonstrate that a Zigbee transceiver, operating in the 2.4GHz band, can communicate with low error rates up to 40mm at low RF power (-25dBm) and up to 70mm at higher power (-3 dBm) in seawater. Ranges are slightly higher in fresh water. Inductive power transfer, using a split transformer design, can transmit low power, in the 50-100mW range with efficiency of approximately 50%, demonstrating that wireless sensor couplings are feasible.