Research On Dual-polarized Base Station Antenna In Mobile Communication System

Along with communication technology,the commercial application of the fifth generation mobile communication system will begin in the near future.As the key component of mobile communication system,the research and design of base station antenna for 5G communication application has become a research focus in recent years.Throughout the research status of 5G antenna technology at home and abroad and the related technical requirements of MIMO system,the base station antenna for 5G system should have the working characteristics of broadband,high isolation,high gain and miniaturization to achieve the high-speed,low delay,large capacity and beam aggregation.With the commercial application of 5G technology in 2020,2G,3G,4G and 5G communication systems will coexist in the future.Considering the shortage of base station space,the serious coupling between antennas on the base station platform and the high cost of network maintenance in the later stage,the communication system places higher requirements on the performance of base station antenna.It not only requires the antenna to obtain smaller size under the premise of achieving the same working characteristics,but also requires the antenna to be broadband and integrated and intelligent for some fields.On the basis of the introduction of the research background,research significance and development status worldwide of base station antenna,combined with the key technologies of mobile communication system and the related research projects during the postgraduate period,this thesis proposes four dual-polarized base station antennas.First of all,a miniaturized dual-polarized base station antenna is designed to solve the problem of serious mutual coupling in the same working frequency band between antennas of MIMO antenna array working in 2G,3G and 4G frequency bands(1.71 GHz-2.69 GHz)with a small column spacing.By loading the parasitic ring and angular metal structures,the transverse dimension of the main radiation structure of the antenna unit is reduced by 43.4%.The designed miniaturized antenna is extended to a 1×4 MIMO antenna array with a column spacing of 90 mm(0.66?₀).Compared with the reference MIMO antenna array,the same polarization isolation of the edge element in the proposed MIMO antenna array is increased by 3.8 d B in 45%of the relative bandwidth,and the same polarization isolation of the middle element is increased by 3.3 d B,which has important reference value for the broadband same frequency decoupling of MIMO antenna array with small column spacing,especially for base station antenna array.Secondly,in view of the requirements of improving the wind resistance of the antenna and saving the space of the station site in the construction of the base station,a broadband dual-polarized base station antenna with a small reflector is designed,which works in 2G,3G and4G frequency bands.By loading the parasitic ring structure and the director structure,the transverse dimension of the reflector of the designed base station antenna is only 70 mm×70 mm(0.51?₀×0.51?₀).The size of the whole antenna is 70 mm×70 mm×68 mm(0.51?₀×0.51?₀×0.5?₀).Then,the broadband dual-polarized base station antenna covering 2G/3G/4G and IMT frequency bands(1.4 GHz-2.7 GHz)is studied.Aiming at the problems of narrow bandwidth and low isolation of existing base station antennas,a broadband dual-polarized base station antenna based on differential monopoles is proposed.The antenna uses two pairs of orthogonal differential monopoles as the main radiation structure,and each monopole is realized by the combination of a trapezoid structure and a rectangular structure to adjust the impedance of the antenna.In a wide frequency band,the proposed antenna can achieve better impedance matching characteristics.The measured bandwidth of the antenna is 1.3 GHz-2.8GHz when the differential reflection coefficients are less than-15 d B,and the relative bandwidth is 73.2%.The measured differential transmission coefficient of the antenna is less than-34 d B in the band of 1.4 GHz-2.7 GHz,and the gain is 7.4 d Bi-8.6 d Bi.It can be seen that the designed antenna has wide impedance bandwidth,high isolation and relatively stable radiation characteristics in the working band.Finally,a dual-band and dual-polarized base station antenna array is designed for 4G band and sub-6 GHz band based on the practical application requirements of base station antenna in the early stage of 5G.First of all,a dual-band and dual-polarized base station antenna unit with a profile of 0.195?₀ is designed by modifying the end of arms of the cross dipoles into the shape of an arrow,digging arc slots on the arms of dipoles and opening rectangular slots on the feeding floors.Otherwise,in order to improve the gain of the antenna and obtain the required beam width,a 2×2 antenna array composed of the designed antenna is proposed.Two four-way power dividers are designed on the reflector to feed the antenna array.At last,the feasibility of the design scheme is verified through processing and actual measurement.The measured results indicate that the antenna has good voltage standing wave ratio,high isolation,high gain and stable radiation characteristics in the frequency bands of 2.3 GHz-2.7 GHz and 3.4 GHz-3.8 GHz.