| With the commercialization of the fifth generation mobile communication system,the multi-system coexistence of 2G / 3G / LTE / 5G has become the main development trend of the modern communications in China.At the same time,in order to solve the problems of insufficient channel capacity and incomplete signal coverage,the 5G communication system will use a heterogeneous network consisting of macro base stations,micro base stations,pico base stations,and femto base stations,which causes the number of base stations to increase exponentially,making the space for installing antenna tighter.Multiband dual-polarized antenna can not only cover multiple working bands at the same time,but also resist the effects of multi-path fading and increase system capacity,which has become one of the research hotspots for base station antennas.Therefore,it is of great significance and value to study multi-band dual-polarized antennas and arrays for 5G base station.The main research contents are as follows:1.Aiming at the problem of multi-system sharing antenna and sky resources shortage,the upper and lower band elements with wide band and miniaturization chracter are proposed.Firstly,by adopting loop dipole,parasitic patch and metal pillar,the upper band antenna effectively expands the bandwidth and realizes miniaturization.The test results show that this antenna has good isolation(>30 d B)and stable pattern(65.5 ?5.5)in the wide band of 2210-3630 MHz.Then,based on the miniaturization scheme of employing wide dipole,cut angle and bent antenna,the bowl-shaped lower band antenna with small radiating aperture 140 mm ? 140 mm is proposed.And its antenna two-element array realizes good radiation performance over the wideband of 670-1080 MHz.2.In order to solve the difficult of wavelength interval between upper and lower band antennas for 5G increase,a compact dual-band dual-polarized array is designed for macro base stations.Firstly,six upper band elements are evenly distributed inside and between two lower band elements,proposing a novel design scheme for multiband array.Subsequently,the performance of this array is improved by raising the upper band array and introducing some structures,such as defective ground and metal baffles.The simulation results show that the isolation of dual bands 698-960 MHz and 2.1-3.8 GHz is respectively greater than 22 d B and 28 d B,meanwhile,the horizontal plane half-power beam widths are 65.95 4.45?? oand 64.75 4.75?? o.3.In response to the conundrms of insufficient bandwidth and radiation unstable pattern,two dual-band dual-polarized electromagnetic dipole antennas for 5G micro base stations are proposed.Firstly,by properly designing the radiating structure and feeding network,dual-wideband and dual-polarized character is obtained.Then,a parasitic patch is loaded above this antenna for reducing the upper band.Finally,we analyze and optimize it for solve the unstable radiation pattern in upper band and other issues.The test results show that the proposed antennas completely cover 4G main-band(2.3-2.7GHz)and 5G midband(3.3-3.6GHz and 4.8-5.0GHz),moreover,high isolation and stable radiation are achieve over the dual-wideband.In summary,these two multi-band dual-polarized antennas proposed in this thesis are consistent with the development trend of base station antennas of multi-band,broadband and miniaturization,providing partial references for designing 5G base station antennas. |
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