| Based on the requirements of handsome appearance and stable performance for the smartphones, metal boundary smartphone got more and more favor of the users and has become a major trend in the mobile phone market at present.However, the influence of the metal boundary for the antenna can not be ignored. Obviously, when the boundary is metallized, there is plenty pieces of metal around the antenna. The presence of these metal parts not only enhance the coupling between the antenna, but also heavily constraint the effective radiation of the antenna. Thereby they will reduce the performance of the antenna. The multi-band MIMO antenna technology for metal boundary smartphone reduces the space available for the antenna to a large extent.Additionally, the coupling between the antenna elements and ground increase the difficulty of design for the multi-band MIMO antennas for the all-metal boundary smartphone greatly.Based on a series of questions of multi-band MIMO antenna for the metal boundary smartphone, firstly, the existing designs for the all-metal boundary smartphone will be analyzed In this paper. Combined with the current domestic and international research results, the distributed characteristics of the metal boundary and the decoupling techniques will be analyzed, providing the necessary theoretical basis for multi-band MIMO antenna design.Secondly, Based on the traditional decoupling techniques and existing research results for metal frame smartphone antenna, a seven-band MIMO antenna for the metal-frame smartphone has been introduced. By the coupling feed technology to couple and excite the metal frame to cover the GSM850, the proposed MIMO antenna design obtains the required bandwidth.Thirdly, a seven-band miniaturized MIMO antenna for the metal-frame smartphone is presented. It takes advantage of the characteristics the metal frame fully. Moreover,occupying a narrow no-ground clearance of 44.5×5 mm2, the design achieves the narrow-frame and metal frame simultaneously.Finally, combined with the miniaturization for smartphone antenna, a seven-band MIMO antenna for all-metal boundary smartphone is presented in this paper. Theprogram contains two types of antenna modes: loop antenna mode and slot antenna mode. By combining the two antenna modes, the desired antenna design covers the LTE/WWAN(GSM850/900/1800/1900/UMTS2100/LTE2300/2500)band operations.The three MIMO antenna solutions were fabricated and tested in this paper. The data shows the performance of the antenna can satisfy the industry requirements for smartpone antenna. At the same time, the performance of antennas with hand loaded and the SAR values of antennas with head model are also simulated. The efficiency and SAR values also satisfy the requirements, which prove the significance of the research for the MIMO antenna for all-metal boundary smartphone. |
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