A Mechanical Transmitter for Undersea Magnetic Induction Communication
Yu Liu, Shuhong Gong, Qian Liu, Muyu Hou
Abstract
The radio waves commonly used in terrestrial wireless communication are severely absorbed by the conductive seawater. However, the low-frequency magnetic fields can penetrate a much farther distance in seawater to realize wireless communication by magnetic induction (MI). An electromagnetic coil is generally used as a magnetic field generator, but it will consume excessive power when generating a strong magnetic field to achieve long-range communication. Instead, this study investigated the use of a motor-driven rotating permanent magnet as a mechanical transmitter for undersea MI communication. The frequency-dependent power consumption and the power-efficient operating frequency range of the mechanical transmitter were analyzed. To establish the undersea MI communication channel model, we derived exact analytic expressions for the fields generated by a rotating permanent magnet in seawater and explored the path loss of the undersea MI channel. A prototype mechanical transmitter using a cylindrical rare-earth magnet (Nd–Fe–B) with a diameter of 4 cm and a length of 15 cm driven by a servo motor was created, which consumes only about 2.74% of the power of the equivalent coil at 30 Hz. The surface-to-undersea MI communication using this prototype mechanical transmitter was demonstrated at a distance of 10 m.