A Research Of Wideband Antenna Based On Magneto-dielectric Material

With the rapid development of wireless communication technology,different kinds of communication equipment are developing in the direction of miniaturization.Antennas,serve as important components of wireless transmission path,have attracted great attention on miniaturization.By means of loading magnetic materials with high permittivity and high permeability,the dimensions of antenna can be greatly reduced.In this paper,electromagnetic parameters of magnetic materials are calculated properly and the microstrip antennas loaded with magnetic dielectric materials are designed.The main contents of this dissertation are as follows:Firstly,the domestic and international research status of magnetic materials used in antenna design and the influence of attached magnetic materials on antenna performance with different loading methods are introduced.Then briefly introduce the principle of effective medium theory,the physical properties of usual magnetic materials and the basic performance parameters of antenna.Secondly,the equivalent electromagnetic parameters of magnetic composite materials are calculated by combining the Landau-Lifshitz-Gilbert equation and effective medium theory.Therefore,the composite materials with iron particles,nanocrystalline particles or ferrite particles included are taken as research objects to confirm that the aforementioned theories are efficient to calculate the equivalent electromagnetic parameters of composite materials.Thirdly,a rectangular microstrip antenna covered with magnetic material is designed.The dimensions of the antenna can be calculated accurately by using the transmission line model.The simulation results show that the resonance frequency of the antenna reduce more with larger electromagnetic parameters or thicker loading of the magnetic materials,which is conducive to the miniaturization design of the antenna and has little impact on antenna gain and efficiency.By covering a layer of magnetic material on the microstrip patch,the resonant frequency of the antenna reduce from 2.45 GHz to 2GHz,the antenna gain reaches more than 4dB in the working frequency range,and the efficiency can be kept above 80%,which achieves the design requirement.Finally,a monopole microstrip antenna based on magnetic material with a microstrip feed line is proposed,and the branches attached to the microstrip line are used for impedance matching.Two loading forms of magnetic material substrate-loading and magnetic material covering are simulated.Nevertheless,the magnetic material used as an antenna substrate leads to a worse impedance matching characteristic of the antenna.In the other way,the covering of magnetic material can sufficiently reduce the resonant frequency of the antenna,and the miniaturization design of the antenna can be realized.The radiation pattern of the antenna with magnetic material covered is basically similar to the original antenna with no magnetic material loading,and the patterns at H-plane are almost omnidirectional.This kind of antenna possesses good radiation characteristics.