Research Of 5G Dual-band And Shared-aperture Base Station Antenna Elements And Arrays

To meet the diverse needs of users,the fifth-generation(5G)mobile communication system needs to coexist with the 2G/3G/4G system.For better network coverage and quality,operators requested more critical specifications for dual-polarized base station antennas with compact size,multi-band and high port-to-port isolation.In the 5G sub-6 GHz base station system,multi-band antennas with high selectivity between different bands have also become an increasingly urgent requirement in complex electromagnetic environments.In addition,covering two or more operating bands with smaller aperture is also the focus of research.This thesis makes an intensive study of dual-band and shared-aperture base station antenna elements and arrays.The specific research contents are as follows:(1)This chapter presents a compact ±45° dual-band and dual-polarized antenna.The proposed dual-band antenna consists of an upper-band(4.8-5 GHz)cross-dipole embedded into a lower-band(3.4-3.6 GHz)magneto-electric(ME)dipole.Without using extra filtering circuit,filtering response can be realized in the upper-band and lower-band antennas.Therefore,mutual coupling between the two antennas can be suppressed intrinsically and the cross-band port-toport isolation is higher than 25 d B.And both the lower-band and upper-band antenna elements have stable broadside radiation patterns and wider 3 d B beamwidth.Moreover,the upper-band element is completely embedded in the lower-band element,and the communication of two operating bands can be realized without additional space.At the same time,loading a slot on the radiator of the lower-band element can not only reduce the mutual coupling with the upperband antenna,increase the cross-band port-to-port isolation in the upper-band,but also improve the S-parameters of the lower-band element.These works have been published in 2020 IEEE International Symposium on Antennas and Propagation.(2)A novel dual-band ±45° dual-polarized antenna element and subarray are proposed in this chapter.The dual-band element is completed by embedding a higher-band(HB)crossshaped filtering dipole antenna embedded into a lower-band(LB)bowl-shaped filtering dipole antenna.The filtering performance is integrated into the dual-band and HB antenna elements to obtain a high cross-band isolation.The proposed antenna subarray consists of 8×1 dual-band elements,7×1 higher-band(HB)elements,and a metal reflector.By combining dual-band and HB elements interleaved with each other,wide beam-scanning range can be realized in the two operating bands.The proposed subarray is simulated and optimized to achieve better antenna subarray performance.The reflection coefficient in passband is good.And it has more than 30 d B cross-band port-to-port isolation in dual-band element and more than 25 d B cross-band portto-port isolation in antenna subarray,realizing high cross-band port-to-port isolation and wide beam scanning range.(3)A novel dual-band ±45° dual-polarized 5G massive multiple-input-multiple-output(MIMO)antenna array is proposed in this chapter.The proposed MIMO antenna consists of8×4 dual-band elements,7×4 higher-band(HB)elements,and a metal reflector.It is composed of four subarrays placed side by side.The large MIMO antenna is processed and measured.The measured results show that the proposed antenna array has two operating bands of 3.36-3.7 and4.6-5.3 GHz for |S11|<-10 d B.The cross-band port-to-port isolation is higher than 25 d B.The measured beam scanning angle of the antenna array is from-55° to +55° in these two operating bands,and the realized gain is over 15 d Bi across the operating bands.The proposed antenna array is a good candidate for 5G multi-band base station applications,due to its advantages of simple structure,high cross-band isolation,and wide-range beam scanning.These works have been submitted to IEEE Transactions on Antennas and Propagation.In this thesis,the decoupling method based on the filtering antenna and the space layout of interlacing dual-band and higher-band elements are detailed.The antennas are fabricated and measured to show the validity and operability of the proposed designs.The proposed designs show the advantages of high cross-band isolation and wide beam scanning,which are potential in wireless applications.