Research On Broadband Circularly Polarized Microstrip Antenna Based On Ferrite Materials

With the rapid advancement of today’s social informatization transf ormation and the rapid development of radio technology,the demand for antennas in all walks of life is increasing,and the requirements are constantly improving,which has spawned the development trend of circular polarization,integration and functional diversification of antennas.Microstrip antennas are widely used due to their advantages of low profile,variety,low cost,and easy fabrication,but they have the disadvantage of narrow operating frequency bands.In this paper,aiming at the narrow frequency band of the microstrip antenna,a method of widening the bandwidth of the microstrip antenna by using the spatial multi-resonance structure is used to design a broadband stacked microstrip antenna based on ferrite materials.Then,starting from the physical fabrication and the practical application of the antenna,a low-profile broadband microstrip antenna is designed by adopting the planar multi-resonant structure instead of the spatial multi-resonant structure to widen the bandwidth of the antenna.Finally,starting from the requirements of circular polarization antenna for the application of electronic information system,the low profile broadband microstrip antenna is arrayed by using the method of feed network,and a broadband circular polarization laminated microstrip antenna is designed.The specific work of this paper is as follows:1.A broadband stacked microstrip antenna with near coupling feed based on ferrite material is designed.Considering that ferrite material as the substrate of microstrip antenna is not easy to drill and copper plating,the designed antenna is fed by adjacent coupling.The radiation antenna is composed of two layers of substrates.The top substrate is made of ferrite material.The front of the substrate is a circular radiation patch,which is fed through the feeder on the front of the bottom substrate.Aiming at the problem of narrow frequency band,starting from the idea of antenna space multi resonance structure,a coating is added directly above the radiation antenna,and an air layer with a certain height is reserved between the coating and the radiation antenna,which effectively expands the bandwidth of the antenna.The designed antenna has a relative bandwidth of 19.1%,and the resonant frequency is5.45 GHz.The maximum gain of the antenna at this frequency is 8.12 d Bi.The gain of the whole antenna is increased by 23.5% compared with that of the antenna without metamaterial coating,and the frequency of the antenna can move to high frequency with the increase of external magnetic field,realizing the reconfigurability of frequency.2.A planar multi resonant low profile broadband microstrip antenna based on ferrite material is designed,and an elliptical parasitic patch is added around the circular patch to reduce the impact of environmental changes on the antenna performance,and avoid the change of dielectric constant and the reduction of antenna performance caused by a certain air gap between the ferrite substrate and the cladding of the broadband laminated microstrip antenna when the antenna is used in a humid environment.The measured data of the antenna are in good agreement with the simulation results,indicating that it can work in the range of 4.75 GHz to 5.73 GHz,with an absolute bandwidth of 980 MHz and a relat ive bandwidth of 18.7%.The highest measured gain of the antenna is not less than 9d Bi in the frequency band.While realizing the broadband expansion of the antenna,a low profile in size is achieved,the height of the antenna is reduced from the original 7.8mm to 3.275 mm,and the designed antenna retains the characteristics of frequency reconfiguration.3.A broadband circularly polarized microstrip antenna is designed,which replaces the bottom feeder substrate of the antenna with a feed network based on ferrite material,and realizes the circular polarization of the antenna.The back of the feeding network is closely attached to a FR4 substrate,and the feeding substrate is gap-coupled and fed through the gap on the back of the feeding network substrate,and then the ferrite substrate is fed by proximity coupling through the four ports of the feeding network.The measured data of the antenna are in good agreement with the simulation results.Resonance points are generated at the frequency points of 4.3GHz and 4.7Ghz,and the designed antenna works in the frequency range of 4.2GHz to4.8GHz,with 13% broadband and the highest gain of 12.4d Bi at the same time.,and circular polarization can also be achieved near the frequency point of 4.7 GHz.The designed antenna realizes circular polarization while realizing broadband,and realizes antenna polarization reconfiguration while retaining antenna frequency reconfiguration.