Research And Design Of Dual-polarized Base Station Antennas In Mobile Communication Systems

With the development of mobile communication technology,the requirements for base station antennas are gradually improving,especially the widely used dual-polarized antennas in base station antennas.Generally speaking,to judge the performance of a dual-polarized antenna,we need to pay attention to the indicators of bandwidth,inter-port isolation,gain and cross-polarization.In this paper,based on the investigation of existing base station antennas,several different structures of dual-polarized antennas are designed,and some solutions are proposed for the problems of narrow bandwidth,poor inter-port isolation and low gain of the traditional scheme,and the metasurface structure is introduced and studied in depth.The main work and innovations carried out in this paper for the design problems of dual-polarized antennas applied to mobile communication base stations are as follows:Firstly,a dual-polarized microstrip patch antenna with continuous current band structure is designed for the problem of poor isolation in traditional dual-polarized antennas,the resonant frequencies of both polarization ports of this antenna cover 3.43 to 3.57GHz,and the isolation degree between ports in resonant frequency|₂₁|is improved from-18d B of traditional dual-polarized microstrip antenna to around-25d B.In addition,a dual-polarized microstrip slot antenna with an isolation band is designed,the resonant frequencies of both polarization ports of the antenna are 2.38 to 4.60GHz,with a bandwidth of 2.22GHz,and the isolation degree between the ports in the resonant frequency band|₂₁|is improved from-10d B of conventional dual-polarized slot antennas to around-20d B.Secondly,based on the principles of slot-coupled feed and dual-polarized antenna,a slot-coupled dual-polarized antenna is designed,and solutions are proposed for its narrow bandwidth,low inter-port isolation and low gain.By introducing techniques of heterogeneous feed,hybrid feed and loading parasitic unit,a hybrid-fed dual-polarized antenna loaded with parasitic unit is ultimately obtained.Test results show that the resonant frequency of both polarization ports of the antenna covers 3.38 to 3.68GHz,with a bandwidth of 300MHz,the isolation between the ports in the resonant frequency band|₂₁|is below-30d B,and the antenna gain at the center frequency reaches 4.58d Bi,the cross-polarization ratios of the horizontal and vertical polarization ports are35.7d B and 35.1d B,respectively.Finally,two antenna designs based on metasurface structure are proposed using the characteristics of in-phase reflection of metasurface structures.One is a dual-polarized metasurface antenna designed by using the metasurface structure as a direct radiator,which consists of 4×4square patches.Simulation results show that the resonant frequencies of both polarization ports of this antenna cover 3.37 to 3.62GHz with a bandwidth of 250MHz,and the inter-port isolation degree|₂₁|is basically around-18d B within the resonant frequency,and the antenna gain at the center frequency is 6.35d Bi.Second,the metasurface structure is used as a reflector,and combined with the hybrid-fed dual-polarization antenna proposed in the previous paper.A hybrid-fed dual-polarized antenna with metasurface coverage is designed,and the metasurface unit consists of 5×5square patches.Test results show that the resonant frequencies of both polarization ports of the antenna cover 3.35 to 3.70GHz,with a bandwidth of 350MHz,the isolation between the ports in the resonant band|₂₁|is below-30d B,and the antenna gain at the center frequency reaches5.32d Bi,the cross-polarization ratios of the horizontal and vertical polarization ports are 29.0d B and 28.7d B,respectively.