Study On Mobile Terminal Antennas For 4G And 5G Applications

As the wireless communication technology evolves rapidly,the fourth generation(4G)communication technology has been widely used in mobile system.In order to further realize high speed,efficiency,low latency and high reliability for wireless communication,the fifth generation(5G)communication technology has become one of the focus of current research.As the key component of mobile communication system,the antenna system in terminal faces many challenges.On the one hand,as terminal equipment develops towards miniaturization and thinness,the space left for antenna design is very limited.On the other hand,for terminal MIMO antenna system,it is necessary to achieve high isolation,low correlation between antenna elements.Based on 4G and 5G terminal communication requirements,4G terminal antenna element,4G dual-element MIMO terminal antenna and 5G multi-element terminal antenna are studied in this thesis.The main contents are arranged as follows: 1.Based on composite right/left-handed transmission line,two different antenna elements for 4G terminal applications are designed,both of which can cover two broad band in limited space.From measured results,the-6-d B reflection coefficient of each antenna element can cover LTE700/2300/2500,GSM850/900/1800/1900 and UMTS2100 bands.30% and 35% antenna efficiencies can be realized in the operating bands.In addition,a dual-element MIMO antenna array is designed using the above antenna element.By combining the defected ground structures and shorting parasitic branches,the isolations in the lower and higher bands are significantly improved.Besides,the radiation and MIMO performance of the dual-element MIMO antenna are also analyzed by using radiation pattern,efficiency,envelope correlation coefficient and so on.2.Two multi-element MIMO antenna arrays for 5G terminals are designed.The first is an eight-port dual-polarized low-profile MIMO antenna based on characteristic mode theory,which can operate at 3.5-GHz band.The proposed MIMO antenna can be integrated with the back cover of terminal devices,which reserves sufficient space for other antennas.This design includes four slot antenna pairs,and two ports on each antenna pair can excite two orthogonal polarization modes to obtain better isolation.The second is a dual-band eightelement MIMO antenna based on multi-mode decoupling technology.The antenna can work in 3.6-GHz and 4.9-GHz frequency bands.Due to the coplanar design of the antennas and decoupling structures,zero clearance can be achieved.By utilizing coupling-fed dual-loop structure,the antenna element can generate two resonant modes.In order to improve the isolation in the operating bands,multi-mode decoupling structures are introduced between the antenna elements.By generating multiple decoupling resonance modes,the isolations of 15.5d B and 19 d B are achieved in the lower and higher bands respectively.The above two MIMO array can realize good operating performance in a compact space,which can be applied to 5G mobile terminal devices.