| In the past ten years,mobile communication technology has developed rapidly.Today,5G is a hot spot in the communications industry,and related technologies are rapidly developing and popularizing.As the most important device to transmitting and receiving electromagnetic signals,smartphone antennas have been constantly evolving.In the beginning,only 2G frequency band was needed to be supported to meet the needs of making calls and sending messages.Later,as the rise of the Internet,mobile phone antennas were required to support 3G or even 4G frequency bands.Nowadays,with the rapid development of 5G networks,high-speed and low-latency experience became an attractive performance.Thus,smartphone antennas need to cover more and more frequency bands.On the other hand,due to the rise of "full screen" designs on mobile devices in recent years,the ground clearance of the smartphone antennas was greatly reduced.What's more,mobile phones need to use metal frame to improve the robustness and aesthetics of the mobile devices.These limitations have brought severe challenges to the design of mobile phone antennas.Therefore,how to further increase the bandwidth of the smartphone antenna with small ground clearance and metal frame to cover 4G/5G or even more frequency bands has obvious research significance.The second chapter of this thesis introduces the research background and briefly summarizes the development of smartphone antennas.Subsequently,the related theories of multipleinput multiple-output(MIMO)antennas are introduced,and the relationship between the layout of the MIMO antenna on the mobile phone is briefly analyzed.Finally,based on the above technical and theoretical analysis,three small ground clearance mobile phone antennas with metal frames for 4G/5G frequency bands are designed.The third chapter shows a metal frame smartphone antenna for 4G/5G operation.Three different antenna structures are fed separately.The low-band structure uses a bending Tshaped grounding stub as the main radiation structure,and the matching circuit is used for impedance matching to meet the coverage of the 698-960 MHz band.The mid-band structure is an IFA antenna with a parasitic element and a matching circuit,finally meets 1710-2690 MHz band coverage.A composite split ring structure is used in the high-band structure to cover the 3300-5000 MHz band.The ground clearance of each antenna structure is 2mm,which has the potential to be used in the future 5G smartphone.The fourth chapter shows a deca-band metal frame reconfigurable MIMO smartphone antenna for 4G/5G operation.By utilizing a switch loading on a floor branches,the lowband structure can cover the 698-770 MHz and 770-960 MHz bands,respectively.Four loop antennas are placed near to the low and mid-band structures.By generating high-order modes on the ground clearance of the low and mid-band structures to broaden the high-band bandwidth which covers the 3300-4200 MHz band.The low-band and mid-band structures forms 2×2 MIMO array respectively,and the high-band structures forms 4×4 MIMO array.The ground clearance of each antenna structures is 2 mm.The antenna has a wide band coverage of LTE700,GSM850,GSM900,DCS,PCS,UMTS,LTE2300,LTE2500,N77,N78 bands.It is suitable for mobile devices to the future 5G communication system.The fifth chapter shows a deca-band metal frame MIMO smartphone antenna with small ground clearance for 4G/5G/WLAN(Wireless Local Area Network)operation.The ground clearance of the antenna is compressed to 1.5mm.The low-band(824-960MHz)and midband(1710-2690MHz/3300-3800MHz)structures forms 2×2 MIMO array.Four slot antennas are combined to the low and mid-band structures to broaden the high-band bandwidth and form the high-band structures,which also forms 4×4 MIMO array and meet the coverage of 4800-5825 MHz band.The measured performance of the antenna is good,and it has the potential to be used in future 5G metal frame mobile phones. |
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