A portable transmitter based on permanent magnets for low-frequency communications in multi-scenario with complex media

There are various advantages of low-frequency (LF) wireless communications such as stable propagation characteristics and low transmission attenuation, especially in lossy media. However, conventional LF especially ELF (extremely low frequency) transmitters have the bottleneck of excessive size and power consumption. Hence, this work proposes an LF signal transmitter based on rotating permanent magnets with miniaturization and portability to address the problem. Firstly, a theoretically analytical model of the transmitter's radiation performance considering size factors and different working methods is established, which provides a more accurate model for the calculation of the magnetic field around the transmitter. Then, a prototype is developed and a test platform is established. Finally, this work explores the potential to apply the proposed rotating magnet-based transmitter (RMBT) in various industrial scenarios. The communication experiments in multi-scenario with complex media are conducted in this work, which completed LF signal transmissions and reception in 20 m air-seawater path (the deepest depth of underwater path in this field up to date). The results verify that RMBT is capable of communication in complex media and different electromagnetic environments, especially under harsh electromagnetic conditions (such as seawater, coal and concrete). RMBT proposed in this work provides a novel strategy for the next research of LF communications in the undersea and underground scenarios.