Research progress of small low-frequency transmitting antenna

Low-frequency electromagnetic waves have the characteristics of long propagation distance, strong resistance to electromagnetic pulse interference, and slow attenuation in seawater and other media. However, conventional low-frequency transmitting antennas have problems such as bulkiness, high power consumption, and low efficiency, which are not conducive to the performance of low-frequency electromagnetic waves. The mechanical antenna is a new type of low-frequency transmitting antenna that generates time-varying electromagnetic field radiation through the mechanical movement of electric charges or magnetic dipoles. The new radiation principle enables mechanical antennas to break the constraints on the physical size of electromagnetic waves in the traditional antenna field, thereby achieving low-frequency communication with a smaller size and higher efficiency, providing a subversive solution to scenarios such as submarine communication and through-the-earth communication. In recent years, mechanical antennas have attracted much attention and become a hot research topic in the field of low-frequency communication. In this paper, we briefly review the development history, development direction, and existing problems of traditional large-scale land-based low-frequency transmit antennas and persistent mobile low-frequency transmit antennas; we mention the details of the working principles and recent research progress of different mechanical antenna implementations including electret, permanent magnet and piezoelectric mechanical antennas; we compare and analyze the radiation performance, innovations, advantages and disadvantages of each specific implementation scheme; and we also discuss the characteristics of the existing frequency modulation, amplitude modulation, polarization modulation and other signal modulation methods of mechanical antennas and the application schemes of several signal modulation methods of different types of mechanical antennas; finally, we prospect the research direction of mechanical antennas in the next stage. At present, the feasibility of the mechanical antenna scheme has been verified theoretically and experimentally, but it is limited by the antenna volume, power consumption, driving device and other factors, and the radiation intensity of the mechanical antenna is limited. We believe that the research in the field of mechanical antennas in the next stage will focus on the design of antennas for achieving longer communication distances at the sacrifice of certain small and light weight indicators, and innovative signal loading and modulation methods to improve communication rates will also be worth paying attention to in the field of mechanical antennas.