Because of its stable propagation characteristics and small attenuation in the medium, low-frequency (LF) electromagnetic wave can penetrate into the sea and underground with small loss. Although its transmission bandwidth is narrow, which limits its application range, it has irreplaceable wide applications in long-distance navigation, communication and frequency release, especially in underwater communication. Therefore, the study of low frequency/very low frequency (LF/VLF) propagation is of great theoretical and military value. In the LF/VLF communication systems, the transmitting antenna is an extremely important part, and its performance has an important influence on the whole system. However, the wavelength of the LF electromagnetic wave is very long. In order to obtain the ideal radiation effect, the traditional method needs a huge transmitting antenna system, which is too large in size and power consumption. Therefore, it will be a disruptive innovation in the field to realize a technology that can significantly reduce the size the existing LF/VLF information network communication system.
In view of this, in this paper we propose a kind of LF/VLF signal transmitting antenna in which an excitation device is used to drive the polarization charge of the electret to move mechanically. By accelerating the charge to form a conductive alternating electromagnetic field which can generate and radiate electromagnetic wave, under the excitation of the wave source, it carries the energy and information in the form of energy flow and propagates in a certain medium. Then, through using the magnetic field receiving system to measure the magnetic field vector in the electromagnetic wave, the effective LF/VLF signal can be obtained, thus achieving the high electromagnetic wave effective radiation which overturns the restriction that the antenna size needs to be comparable to the wave length of the radiation signal in the traditional LF navigation communication system. At the same time, an analytical model of magnetic field propagation is established based on this structure, and the influence of antenna size, shape and other relevant parameters on the performance of antenna communication are studied as well. In order to reduce the loss of accuracy and improve the calculation speed, it is necessary to choose the correct analytical model and the appropriate parameters of magnetic field generated by the mechanical antenna according to the actual situation. The research work is of great significance for designing and optimizing mechanical antennas.
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