| As an essential part of the communication system,the base station antenna has attracted more and more people's attention.So the research of miniaturization,low profile,multi-polarization and low cost of it has become the hotspots of recent years.In this paper,the main work and achievements are proposed as follows:1)A novel compact dual-polarized gradually open coupling feed antenna for base station application is presented in this paper.The antenna is mainly composed of two tapered feeding structures,a circular radiator with four sector slots and a reflector.The tapered feeding structure is fed by the stepped microstrip lines connected with coaxial cable.Performance of the antenna can be improved by optimizing the key geometric parameters of the antenna.The optimal antenna design only occupies a volume of120mm×120mm×32.8mm,and is validated by simulation and measurement,which agree with each other in the results.The measured results show that the antenna can achieve impedance bandwidth of 46.6% for |S11|<-15 d B at least from 1.71 GHz to 2.75 GHz,and the isolation between the two ports with different polarizations is higher than 30 d B,and the front-to-back ratio are more than 24 d B both ports,the average gain achieved is around 8d B.Finally,an eight-element array is proposed and it can satisfy the application requirements verified by simulation.2)Two low-profile dual-polarized base station antennas are designed by using AMC reflectors instead of traditional metal reflectors,and the AMC reflectors of the antennas are composed of an AMC surface,a metal ground plane and an air substrate between them.The first base station antenna consists of an orthogonal petal-shaped dipole,a feed structure,and an AMC reflector formed by a 7 x 7 periodic patch unit,the height of it is reduced to 18.8mm.Simulation results show that the operating frequency range is from 1.69 GHz to 2.71 GHz with |S11|<-10 d B,the isolation of the two ports is better than 20 d B.In order to improve the feeding structure andincrease the isolation of the antenna,a series of improvements are carried out,such as the height of antenna is slightly increased to 21.6mm,the design on the unit cell of the AMC plane is simplified,and the feeding structure of the antenna is changed.Finally the bandwidth of the second antenna is widened,which can cover 1.6 GHz to 2.95 GHz frequency band,the isolation is greater than 30 d B and the antenna have stable radiation mode.3)It is well known that the radiation patterns of the dual-polarization base station antenna are important features in design,but commonly the electromagnetic simulation design software cannot directly give the ±45?polarization patterns of the antenna in the horizontal and vertical planes.In order to correctly obtain the radiation pattern of the ±45 dual-polarized base station antenna designed in this paper,we analyze the synthesis method of the ±45? dual-polarization radiation patterns of the base station antenna theoretically firstly,and than under the condition of knowing the ? and ?electric field components in spherical coordinate,the expressions of the±45? polarization components of the composite field are given.The calculation method is verified by a measurement model of base station antenna simulated in the CST electromagnetic simulation software.The simulation and calculation results agree highly with each other,indicating that the presented calculation method is reliable and correct. |
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