Electromagnetic induction

Oceanography

Magnetic field

Electrical engineering

Physics

Channel (broadcasting)

Geology

Engineering

Magnet

Underwater acoustic communication

Materials science

Acoustics

Electromagnetic coil

Computer science

Transmitter

Wireless

Quantum mechanics

Telecommunications

Underwater

IEEE Transactions on Antennas and Propagation

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.

A Mechanical Transmitter for Undersea Magnetic Induction Communication