Research On ELF-ULF Mechanical Communication Antenna

Cross-media wireless communication technology is an important part of communication technology.It has broad application prospects in marine data collection,pollution monitoring,disaster prevention,communication between unmanned submarines,natural resource exploration,underwater collaborative scientific data collection.Research on portable miniaturized low-frequency antennas is a major development trend of underwater wireless electromagnetic wave communication in the current and future.For traditional antennas,the size is often on the same order as the wavelength of the radio wave.Because the wavelength of ELF-ULF(3-3k Hz)is several kilometers,the antenna covers a large area,the cost of laying is huge and the concealment is poor.They are all permanently installed,which brings many difficulties to the manufacture of the antenna.The mechanical antenna introduced in this thesis may be a new idea to solve the miniaturization of low-frequency antennas.Instead of using a metal antenna,the permanent magnet mechanical movement method can be used to generate an alternating electric field or magnetic field equivalent to that of a traditional antenna,and the electromagnetic wave can still be emitted like a traditional antenna.In this thesis,the mechanical antenna is deduced theoretically,and the permanent magnet with fixed axis is used as the basic structure.Relevant expressions such as the radiation equation of the mechanical communication antenna,the magnetic field in the near and far regions,the electric field intensity distribution,the radiated power and the energy flow density are obtained.According to the derivation,the induction field generated by the rotating permanent magnet is similar to the static magnetic field,and is only affected by the magnetic permeability of the surrounding environment.Through numerical simulation,the parameters that affect the propagation performance are obtained,and through finite element simulation,the shape of the magnetic field and electric field excited by the mechanical antenna in three-dimensional free space is explored,obtained the three-dimensional magnetic field and electric field distribution map of the antenna.According to the previous theoretical basis,the prototype of the mechanical antenna principle is divided into two parts: the transmitting module and the receiving module for design and manufacture.The transmitting module includes the material selection and processing of the transmitting unit,designing the motion mode of the transmitting unit and manufacturing the mechanical drive device;the receiving module includes the selection and production of the receiving coil parameters,drawing and debugging the pre-amplifier circuit,low-frequency power amplifier circuit,eighth-order Pass filter circuit.When the principle prototype is completed,the information loading technology under mechanical inertial constraints is studied.Signal modulation is performed on the mechanical movement of the transmitting unit by using a mechanical drive device,three signal modulation schemes are designed,and experiments are conducted to find the most suitable information loading method for the mechanical antenna.Based on the mechanical antenna principle prototype designed and manufactured above,a field test experiment with a relatively complex environment is conducted.The selected test scenarios are divided into ordinary outdoor scenarios and cross-media communication scenarios.By performing a short-time Fourier transform on the received signal,a timespectrum graph and a signal-to-noise ratio are obtained.The analysis of the experimental results and data verifies that the mechanical antenna is feasible in the cross-media communication scenario.It provides a new way to solve the problem of miniaturization of transmission antennas and is of great significance to the development of low-frequency communications.