| With the development of the fifth generation(5G)mobile communication techniques and Internet of Things,massive users will be linked to the mobile communication network.To enhance the capacity and quality of the network,more base stations need to be built and more frequency channels need to be adopted.The antenna is a critical component of a base station and its performances of bandwidths and radiation patterns have much influence on the communication quality.To reduce the construction cost of the base station and increase the network capacity,base station antennas are required with a wide bandwidth,small volume,low cross polarization,high gain,etc.In this thesis,base station antennas with a wide bandwidth and dual polarization have been studied and designed.The main work is given in the following:(1)An antenna for 5G base stations covering n40/n41/n78 bands has been proposed.The proposed antenna consists of two pair of orthogonal rectangular planar dipoles with two chamfers.The horizontal dipoles are fed with a balun,which is perpendicular to them.The total electric size of the proposed antenna is 0.87×0.6×0.25λ_L~3.Measurement results show that the proposed antenna has a bandwidth of 2-3.95 GHz,coupling lower than-25 d B,peak gain of 8.36 d Bi,cross-polarization discrimination(XPD)higher than22 d B,front-to-back ratio(FBR)better than 24 d B,and stable half-power beamwidth(HPBW)of 60°-72°in the whole operating band.Compared with the existing base station antennas,the proposed antenna has a wider bandwidth and a stabler HPBW.(2)An antenna covering 2G/3G/4G/5G multi-band has been proposed for multi-standard base station systems.The double-sided printed process is adopted in the hexagonal radiating arms.By slotting the radiating arms inside and loading rectangular patches,the size has been reduced and the bandwidth has been widened.The total electric size of the proposed antenna is only 0.57×0.57×0.17λ_L~3.Measurement results show that the proposed antenna has a bandwidth of 1.75-3.75 GHz,coupling lower than-16 d B,peak gain of 6.99 d Bi,XPD higher than 17 d B,FBR better than 25 d B,and stable HPBW of 67°-76°in the whole operating band.Compared with the existing base station antennas covering similar frequency bands,the proposed antenna has a smaller size in a wide frequency band.(3)An antenna element covering 2G/3G/4G/5G multi-band has been proposed for multi-standard system base station,which obtains a consistent HPBW during a broad bandwidth.Based on the antenna element,a linear array has been proposed.The dipole arms of the proposed antenna element are designed with a dual-hexagon shape.By loading parasitic patches and adjusting the distance between two dipole arms,the bandwidth of the proposed antenna element has been broadened.The reflector is designed with an open-box shape and the inverted L-shaped metal sidewall is loaded around the planar reflector to keep the HPBW consistent during the operating band.The total electric size of the proposed antenna element is 0.81×0.81×0.2λ_L~3.Measurement results show that the proposed antenna has a bandwidth of 1.7-3.8 GHz,coupling lower than-25 d B,peak gain of 9.3 d Bi,XPD higher than 24 d B,FBR better than 26 d B,and stable HPBW of 56°-63°in the whole operating band.Base on the antenna element,a1×4 uniform linear array has been designed with an element spacing of 85 mm,which total electric size is 2.04×0.82×0.16λ_L~3.Measurement results show that the proposed antenna has a bandwidth of 1.7-4.2 GHz,coupling lower than-22 d B,peak gain of 15.42d Bi,XPD higher than 20 d B,FBR better than 20 d B,and stable HPBW of 56°-63°in the whole operating band.Compared with existing 2G/3G/4G/5G base station antennas,the proposed antenna element has a wider bandwidth and a smaller fluctuation range of the HPBW.Moreover,the proposed antenna array provides a wider bandwidth than the existing ones. |
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