Research On High Performance Handheld Mobile Terminal Antennas In Complex Electromagnetic Environment

Unmanned aerial vehicles(UAVs),smart wearable devices,and mobile phones are deemed as handheld mobile terminals.With the development of mobile communications,the frequency range of the handheld mobile terminals are expanding rapidly.The operating bands need to cover the WLANs(wireless local area networks)bands,the GPS(Global Positioning System)bands,and the 2/3/4/5 G bands.Also,the electromagnetic environment of the handset antenna is more and more severe.In this doctoral dissertation,the researches are carried out on handheld mobile terminal antennas incomplex electromagnetic environment.Also,the studies force on the directional radiation characteristic,the wide-band characteristic,the miniaturization technique,and the decoupling technique.And six antennas are proposed in this doctoral dissertation.(1)Firstly,a dual-band directional antenna is proposed for unmanned aerial vehicles applications with a 0.8-mm low profile as well as 15-dB F/B ratios.Also,the feeding technology is discussed during the measurement process and a new method is proposed to deal with the asymmetry of the coaxial feeding without balun.The current along the outer side of the outer conductor together with that along the dipole can be treat as whole radiation source.In this way,the asymmetry of the radiation patterns can be suppressed.(2)Secondly,antenna designs for metal shell/frame handsets are also studied.A dual-band antenna operating at WLAN and GPS bands is proposed,utilizing the metal shell of the handset as part of the radiator.During the design process,the metallic components such as USB,cameras,and telephones receiver are taken into consideration;Based on the characteristic mode analysis about the metal frame of the handset,another handset antenna covering the 824-960 MHz and 1710-2690 MHz bands without extra radiation strips is also proposed.Three RF switches are introduced to tune the frequencies of certain resonant mode;Then a mode control method is introduced to achieve wider bandwidth(699-960 MHz and 1710-2690 MHz)for metal frame handset with only 1-mm metal clearance.The proposed mode control method can tune the resonant frequency of certain mode respectively,which is of great significance to achieve wide-band characteristic;Also,to achieve antenna miniaturization,another metal frame handset antenna is introduced using the mode control method as well as the coupling feed technique.The 0.25? loop mode can be excited together with the traditional 0.5? loop mode,which can cover the 824-960 MHz and 1710-2690 MHz with only 41-mm metal frame.The miniaturization makes is possible to arrange other antennas for 5G applications in the future.(3)Finally,a co-located self-neutralized antenna pairs with complementary radiation patterns are proposed for 5G MIMO(Multiple Input Multiple Output)applications.The co-located antenna pairs can achieve high isolations by the proposed self-neutralized mechanism.The isolations of the co-located antenna pairs are better than 25 dB.Also,the complementary radiation patterns of the antenna pairs enable the ECCs are lower than 0.1.Then,4/8/10 MIMO antenna systems are also studied by simulation.The impactsof hand-held scenarios are also studied to verify theirs practical performances.