Research On Multiband And MIMO Antennas For 5G Mobile Terminal Applications

With the rapid development of the mobile communication industry,5G communication has been deployed or put on the work schedule by major communication giants in the world.Mobile terminal devices such as smart wearable terminal devices,mobile phones and tablets have strong demands of new antenna technologies to achieve high-speed and high-quality services,therefore,people have put forward higher requirements on the size and performance of mobile terminal antennas.Multiple-input and multiple-out(MIMO)technology,as a crucial technology in the field of wireless communication,has the unique advantages of improving wireless channel capacity,spectrum utilization and data transmission rate without increasing bandwidth and antenna transmission power.However,how to achieve antenna's miniaturization with multi-band/wideband support and reduce coupling between multiple antennas in a very small space is a very critical issue.This thesis firstly summarized the MIMO antenna designs and limitations in the previous published work,then,proposed three new MIMO antennas to address the existing design challenges and implementations especially for 5G applications.The main contributions of this thesis include the following:Firstly,a wearable watch antenna that covers the 5G and GPS frequency bands is designed.The metal frame and the PCB ground are used as radiators.By adding short-circuiting bar and slots at appropriate positions,multi-band functionalities are generated.Sufficient bandwidth is achieved to cover the 5G bands at 7/42/43/ 4.9-GHz and GPS L1 band(1.575 GHz)for wearable device applications;Secondly,a 5G/WLAN 8-port MIMO mobile phone antenna system for smart phone terminal model is designed.It consists of two monopole-type WLAN antennas and six miniaturized PIFA-type 5G antennas.The WLAN antenna supports WLAN bands a/b/g/n(2.4 and 5 GHz)and 5G antenna supports bands B42/43(3.4-3.8 GHz),Therefore,this antenna system achieves a very compact design to support 2×2 WLAN MIMO and 6×6 sub-6GHz 5G MIMO.Finally,an ultra-wideband 8x8 MIMO antenna system is designed to cover global sub-6GHz bands(3.4-5 GHz)for 5G mobile phone applications.To improve isolation between MIMO antenna elements,the decoupling techniques with parasitic branches are proposed in the center of the mobile phone.This antenna system has been fully studied via simulation and measurement,both Indicates that the MIMO antenna system works well and has good potential for 5G mobile terminal applications.