Model and Design of a Novel Low-Frequency Magnetic Signal Transmitter Based on Rotating Electret

The ultralow-frequency/very-low-frequency (ULF/VLF) band communication is stable and worldwide, which can penetrate into sea or underground with slight loss. It plays an irreplaceable role in oceanic great-depth communication, distant navigation, and geologic examination. In a conventional ULF/VLF transmission system, in order to effectively emit electromagnetic (EM) waves, the length of the transmitter should be close to the wavelength of the radiation signals. As a result, there are problems of complex structure, huge volume, and large power consumption in conventional LF transmitting system. Therefore, this work introduced a mechanical ULF/VLF transmitter designed with mechanically rotating electret to greatly reduce the size, and a generated magnetic field model based on finite-element method (FEM) is established to carry out the relevant analysis. The characteristics of the magnetic signals generated by electret-based transmitter such as direction and frequency are studied in detail. At the same time, the influence of relevant parameters such as size, rotation speed, electret material, and the number of layers on the magnetic signals is analyzed as well. What is more, the effect of lossy media and the propagation distance on the transmitter’s performance are also discussed. This work will lay the foundation for future system tests involving the implementation of efficient, small form-factor, mechanically actuated LF transmitters.