Research On Miniaturized Wideband Dual-polarized 5G Base Station Antennas

Since 2019,5G mobile communication technology has been exerted an important role in many fields,such as automatic driving,remote diagnosis,and large-scale device interconnection.As the top position of the wireless communication system,the performance of the 5G base station antennas are directly related to the quality of the communication system.5G base station antennas that meet the requirements are urgently needed in engineering.Therefore,the performance of miniaturization,broadband,high isolation and low profile of 5G base station antennas are focused in this thesis.Firstly,the background and significance of the research are discussed,then the relevant basic theory related to this research is given,and then the research work of thesis is described.The main research contents can be summarized as follows:(1)Research on differentially fed broadband dual-polarized base station antennaThe 5G base station antennas for multi-band shared and high isolation are envisioned in communication system.Therefore,a differentially fed broadband dual-polarized base station antenna is studied in this thesis.The input impedance of the antenna and the coupling between the adjacent dipole arms are changed by adopting double-layer metal dipole patches and introducing chamfers between adjacent dipole arms.The impedance bandwidth of the antenna is 3.2-5.7 GHz and can cover the N77,N78,N79 frequency bands of 5G Sub-6 GHz.The overall size of the antenna is 0.67λ_L×0.67λ_L×0.2λ_L(λ_L is the wavelength at the center frequency of 3.2-5.7 GHz).Meanwhile,the high isolation characteristic of the antenna is realized by the cross-shaped differential feed structure,and the port isolation is greater than 39 d B.In addition,the half-power beamwidth of the antenna is 66±5.5°,and the gain of the antenna is 8.2±0.4 d Bi.The measured and simulated results of the antenna are in good agreement.(2)Research on low profile dual-polarized base station antenna loaded with AMCThe communication system is expected to achieve miniaturization in antenna size.How to design the low-profile dual-polaried antenna without losing its electrical performance is an urgent problem to be solved in engineering.Therefore,a low-profile dual-polarized base station antenna loaded with AMC is studied in this thesis.The dipole arms of the antenna are bent inwards,and the actual physical length of the dipole arms are increased without increasing the extra structure,so that the dimension of the antenna is reduced.Moreover,the T-shaped coupling microstrip line is also conducive to broaden the operating bandwidth of the antenna,and the antenna can be applied in the N78 band of 5G Sub-6 GHz.Then,the traditional metal ground is replaced by an artificial magnetic conductor reflector,so that the profile height of the antenna is only 0.16λc(λc is the wavelength at the center frequency of3.1-4.0 GHz).Finally,the impedance bandwidth of the antenna is 3.1-4.0 GHz,and the isolation between ports is higher than 29 d B.In addition,the measured gain of the antenna is 7.5±0.3 d Bi,and the half-power beamwidth is 66±3°.The measured and simulated results of the antenna are in good agreement.(3)Research on dual-polarized folded dipole array base station antennaThe bandwidth,isolation and profile height of the aforementioned two antennas are studied separately.However,low-gain antennas will affect long-distance communication when the transceiver equipment remains unchanged.In order to solve this problem,a four-element linear array antenna that uses a dual-polarized folded dipole base station antenna as an element is designed,which covers the N77,N78 frequency bands of 5G Sub-6 GHz.The element of antenna is different from the traditional crossed dipole,the four folded dipoles of the antenna are located on the same surface and form a circular radiator.When one of the folded dipoles is excited,the four folded dipoles are excited as a whole.Finally,the operating bandwidth of the antenna element is 3.2-4.36 GHz,and the isolation is better than 25 d B.On this basis,a four-element linear array is designed.After optimizing the spacing of the antenna elements,the measured operating frequency bands of port 1 and 2 of the final array antenna are 3.2-4.28 GHz and 3.13-4.3 GHz,and the port isolation is higher than 24 d B.In addition,the array gain reaches 13.6-14.9 d Bi,and the half-power beamwidth is 62±2.5°in the horizontal plane.The measured results of antenna element and array are basically consistent with the simulated results.At the end of the thesis,the research content is summarized and the direction for further research are pointed out.