Researches On Low-profile Yagi-Uda Antenna Based On Open-cavity Magnetic Dipole

With the rapid development of wireless communication technology,communication platform equipment is gradually miniaturized and planarization,and the available space of antenna decreases accordingly.With the increasing number of communication equipment and the complex communication environment,the antenna,as an important transceiver component in the wireless communication system,needs to have the characteristics of high gain,lowprofile and conformal.Therefore,the high gain and low-profile antenna is still the focus of many researches.Compared with the horizontal polarized antenna,the vertical polarized antenna has smaller radiation aperture in the vertical direction due to the requirement of limited profile,so it is difficult to achieve high gain.In this paper,the gain of the effective radiation area is increased by the effective use of the aperture in the horizontal direction based on the structure of the open-cavity magnetic dipole under the condition of the profile limitation.Based on open-cavity magnetic dipole and Yagi-Uda antenna,two kinds of antennas are designed and proposed in this paper.1?Analysis of low-profile,gain enhanced omnidirectional Yagi-Uda antenna: the center-fed circular patch antenna has characteristics of low-profile and monopole-like omnidirectional radiation pattern.However,the radiation patterns' beam tilt with the sizelimited ground plane,suffering from small omnidirectional azimuth gain.In order to increase the omnidirectional azimuth gain,the annual omnidirectional director is proposed basing on the structure of open-cavity magnetic dipole.Several directors cooperating with the driven element realized by improved center-fed circular patch form the proposed antenna.Measured results show that the prototype can realize-10-d B impedance bandwidth of 13%(4.72-5.42 GHz)and gain of 3.72 d Bi at 5.34 GHz with good omnidirectivity.Compared with that of the driven element only,the omnidirectional azimuth gain is significantly improved within the bandwidth,with the maximum gain being enhanced from-4.2 to 3.72 d Bi at 5.34 GHz.Because the array is axisymmetric and symmetric about the azimuth plane,a radiation pattern symmetric in both the azimuth and elevation planes can be realized.This proposed gain enhanced and low-profile omnidirectional Yagi-Uda antenna has advantages of good omnidirectivity,simple structure,convenience for manufacture and it can be integrated with many communication equipment easily.This antenna can be a candidate for a portable 5G Sub-6GHz wireless channel measurement application.2?Research of low-profile,high gain structure-integrated dual-polarized Yagi-Uda antenna: based on the basic structure of open-cavity magnetic dipole,the structure-integrated dual-polarized driven element,director and reflector can be proposed respectively,and then the Yagi-Uda antenna be designed.The driven element of proposed antenna consists of a pair of open-cavity magnetic dipoles.The vertical-polarization(VP)and horizontal-polarization(HP)can be excited by feeding differentially in special positions.Besides,dual orthogonal polarizations are integrated in the single structure.Directors and reflectors are adopted to enhance gain of driven element.The dual-polarizations can be integrated in the proposed antenna,and the high gain end-fire radiation pattern also obtained.A 3-element(Ant.I)and 7-element antenna(Ant.II)are designed,fabricated,and measured to verify the design.The operation bandwidth of Ant.I is from 4.11 to 4.83 GHz(18.2%)with ports isolation higher than30 d B,and gains of VP and HP are from 5 to 7.1 d Bi and 5.6 to 6.4 d Bi,respectively.The Ant.II can operate from 4.02 to 4.78 GHz(15.2%)with ports isolation higher than 30 d B and the measured gain of VP is from 7.8 to 8.34 d Bi and gain of HP varies from 8.9 to 10.3 d Bi.Compared with other dual-polarized antennas,this antenna can realize VP and HP in one structure with high isolation and low-profile.The antenna has the characteristics of low-profile,high gain and integrated-structure,which can greatly reduce the space of antenna and the number of antenna's units,and provide a technical design scheme for the low-profile,high gain end-fire antenna of Sub-6GHz.