Research On Magnetic Mechanical Antenna

Ultra-low frequency(SLF)and very low frequency(VLF)electromagnetic waves are widely used in military and civilian fields such as submarine communications and geodetic surveys because of low attenuation characteristics in conductive media.The traditional low-frequency electromagnetic wave transmitter is a dipole antenna based on Maxwell's equations.It is limited by the operating wavelength.The antenna is large in size and difficult to maintain and install.Therefore,the problem of the size in the low band is a hot issue in the electromagnetic fields.Although some researchers hope to increase the radiation efficiency by loading capacitors or using antenna arrays to reduce the size of the antenna,the working principle is still to use the electric oscillator to radiate,so the miniaturization effect is not obvious.In this paper,a type of magnetic mechanical antenna is proposed,which uses mechanical motion to generate time-varying magnetic field,no longer uses the electric vibrator for radiation,and can enhance the radiation efficiency by increasing the magnetic field of the magnetic object.The size of the antenna is also not limited by the wavelength.The operating frequency of the antenna can be set by the rotation speed,which is of great significance for the study of the low frequency antenna.Firstly,this paper expounds the principle of magnetic mechanical antenna from Maxwell's equations,vector superposition method and electromagnetic duality,and analyzes the near-field electromagnetic characteristics and far-field electromagnetic characteristics of magnetic mechanical antenna in the free space.The proof method is used to obtain the electromagnetic field distribution law of the rotating magnetic dipole.The consistency of the three derivation methods also proves thecorrectness of the theoretical derivation.Secondly,the equivalent model of the rotating magnetic dipole is obtained by vector superposition method.The near-field and far-field characteristics of the rotating magnetic dipole are obtained by simulation software.The simulation results and analysis of the near-field characteristics of the rotating magnetic dipole are obtained.The results were compared to demonstrate that the near-field derivation of the magnetic mechanical antenna is correct.At the same time,the simulaiton results of the far-field radiation characteristics of the rotating magnetic dipole are compared with analytical results.The simulation results are in agreement with the analytical results and the conclusion is drawn.Then,the results is verified by the rotating magnetic field existing when the motor is working.When the motor is working,a rotating magnetic field is generated inside the shell.The amplitude of magnetic field is constant.In the free space,the electromagnetic field distribution in different directions and the electromagnetic field distribution at different distances in the same direction were verified in the free space.The experimental results were compared with the analytical results and the conclusions were drawn.Further,through the long-distance motor test,low-frequency signal can be received at 100 meters and 60 meters of the rectangular corridor in the semi-open space,indicating that the high-speed rotating electrical machine can work as a magnetic mechanical transmitting antenna.Finally,the paper summarizes working content.The magnetic mechanical antenna designed in this paper provides a new idea and method for research of low frequency antenna.It can be applied in many communication occasions such as mine communication and underwater communication in the future.