Research On Key Technologies Of Acoustic Excitation Low Frequency Magnetoelectric Antenna

Low frequency electromagnetic wave has the characteristics of long propagation distance,strong anti-electromagnetic pulse interference ability and low propagation loss,and is widely used in the fields of ground/water penetration communication,geological exploration and military.The traditional low-frequency transmitting system is a dipole antenna based on electromagnetic resonance.Limited by the wavelength of electromagnetic wave,the transmitting system is bulky,difficult to install,expensive to maintain and poor mobility.Researchers use vehicle-mounted,ship-borne,airborne,and space-borne maneuvers to improve the mobility of the low-frequency launch system.The low frequency antennas of these persistent maneuvering modes are radiated by electric oscillator,which cannot change the problem of the large size of the low frequency transmitting system.Acoustic excitation low-frequency magnetoelectric antenna uses acoustic resonance instead of electromagnetic resonance.The size of the antenna is determined by the wavelength of acoustic wave,and is not limited by the wavelength of electromagnetic wave.The acoustic resonance frequency is the working frequency of the antenna,which provides an idea for the miniaturization of lowfrequency transmission system.The multi-physical finite element model of acoustically excited magnetoelectric antenna is established,and the coupling simulation of "electric-mechanic-magnetic" is realized.The conversion of electrical energy and mechanical energy is realized by the coupling of solid mechanical field and static electric field.The working mode of the antenna is analyzed,and the working frequency of the antenna and the stress distribution of the magnetostrictive layer are obtained.The mechanical energy and magnetic energy can be converted by the coupling of solid mechanical field and micromagnetic field,and the absorption law of elastic wave energy of magnetostrictive material is obtained.The average radiation power of the antenna is derived by using the constitutive relation of magnetostrictive material and electromagnetic boundary conditions.Combined with the simulation results,the influence of the thickness of the magnetostrictive layer on the average radiation power of the antenna is obtained.The optimal thickness ratio between the magnetostrictive layer and the piezoelectric layer is 1:1,which provides a reference for the development of the antenna.The radiation performance of the antenna under different thickness ratios of laminated materials and different resonant modes is explored.The influence of different resonant modes on the optimal bias magnetic field is explored under the condition of the optimal thickness ratio of laminated materials.The working mode of the antenna is measured by laser vibration meter,and the correctness of the working mode obtained by finite element simulation is verified.As the thickness of magnetostrictive layer increases,the resonant frequencies of bending resonance,length shear wave resonance and width Lamb wave resonance all shift upward,and the measured results are basically consistent with the simulation results.When the thickness ratio of magnetostrictive layer to piezoelectric layer is 1:1,the radiation intensity of antenna is maximum.The basic parameters,such as direction pattern and efficiency,characterizing the length shear wave resonance,verify the hypothesis that the radiation of magnetoelectric antenna is similar to that of dipole antenna.The results show that the acoustic excitation low-frequency magnetoelectric antenna has advantages in volume and efficiency,which provides a scheme for the miniaturization of low-frequency transmission system.