In underwater applications, such as underwater robots, autonomous underwater vehicles (AUVs), and remotely operated vehicles (ROVs), magnetic-field coupled wireless power transfer (MC-WPT) enables the transmission of electrical energy without electric contact, improving the flexibility and security of power transfer. Underwater electrical devices and base stations must achieve long-distance and high-power wireless power transfer while realizing high-speed bidirectional wireless information exchange to enable command transmission, data feedback, and closed-loop control. Many scholars have researched shared-channel magnetic-field coupled underwater simultaneous wireless power and information transfer (MC-USWPIT) technology. However, there is still a gap between the transmission distance, power transfer capacity, information transfer speed, and the requirements of engineering applications. Therefore, this paper proposes an underwater simultaneous wireless power and information transfer system with a coplanar double-coil coupler. The research focuses on rapid wireless power replenishment and high-speed bidirectional information transmission for AUVs in seawater. The goal is to achieve high-power energy transfer and high-speed bidirectional information transmission over long transmission distances.

The coupler with a coplanar double-coil and the MC-USWPIT system topology are proposed. Using the relay coil for information transmission reduces the voltage stress on the information transmission circuit and helps mitigate the crosstalk between the power and information transfer channels. By employing an injecting information method with a series of LC circuits in the information transmission channel, the LC circuit is fully compensated at the power transmission frequency. Furthermore, smaller capacitance-blocking capacitors further reduce the crosstalk between the power transmission channel and the information transmission channel, as well as the voltage stress on the information transmission channel, thereby reducing the difficulty of system design.

Subsequently, the system is analyzed and modeled, and equivalent circuit models for the power and information transfer channels are provided. A parameter design method for the MC-USWPIT system is proposed. The method reduces the eddy current losses induced by the seawater and minimizes the impact of high-power energy transmission on the information transfer speed. It enables the simultaneous improvement of transmission distance, power transfer capacity, and information transfer speed in a frequency-division multiplexed MC- USWPIT system.

Finally, a 5 kW experimental setup in simulated seawater is constructed. In an environment with a seawater conductivity of 4.15 S/m, the system achieved a transmission distance of 50 cm, an output power of 5.33 kW, and an information transfer speed of 5.68 Mbit/s. Furthermore, under varying seawater conductivities (4, 5, and 6 S/m) and transmission distances (30, 40, and 50 cm), the system still demonstrates good power transfer performance and high information transfer speed. The experimental results confirm that the proposed MC-USWPIT system and method can effectively improve the transmission distance, power transfer capability, and bidirectional information transfer speed in simulated seawater.