A switchable antenna array is presented for upcoming 4G/5G massive multiple-input multiple-output (MIMO) smartphone applications. The designed antenna is constructed of two modules of the antenna array, namely, a switchable 2 × 2 MIMO 4G antenna module with frequency and circular polarization diversities and a 6 × 6 MIMO 5G antenna module with pattern diversity. Each element in the 4G and 5G modules is fed using by a microstrip line with a tuning slot on the ground plane, consisting of a spiral patch and a short-ended C-shaped stab as parasitic element on the non-metal frame. An area of 22 × 9.3 mm² is occupied with each element on the ground plane. Spatial diversity and polarization techniques are used for these antenna elements with the purpose of the reduced coupling effects and enhanced isolation can be achieved. The module of 4G antenna can be work and switch between two operating bands of LTE-2500 and 5G band by embedding a PIN diode in the structure of antenna element, while the 5G antenna module can be operate in the 3.4–3.6 GHz and could meet the request of upcoming 5G application. The proposed MIMO antenna array is fabricated and tested. Measured isolation of the proposed antenna is more than 15.2 dB in the ON and OFF states of the PIN diodes without applying of any decoupling structures. Furthermore, measured antenna efficiency, radiation pattern, envelop correlation coefficient, and ergodic channel capacity over the desired bands are also verified in this article.

中文翻译：

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适用于 LTE 和 5G 应用的具有频率捷变和极化分集的大规模 MIMO 框架天线

为即将到来的 4G/5G 大规模多输入多输出 (MIMO) 智能手机应用提供了一种可切换天线阵列。设计的天线由天线阵列的两个模块构成，即具有频率和圆极化分集的可切换 2×2 MIMO 4G 天线模块和具有方向图分集的 6×6 MIMO 5G 天线模块。4G 和 5G 模块中的每个元件都由一条微带线供电，在地平面上有一个调谐槽，由一个螺旋贴片和一个短端 C 形刺作为非金属框架上的寄生元件。面积 22 × 9.3 mm ²被地平面上的每个元素占用。空间分集和极化技术用于这些天线元件，目的是降低耦合效应并增强隔离度。通过在天线振子结构中嵌入PIN二极管，4G天线模块可以工作并在LTE-2500和5G频段两个工作频段之间切换，而5G天线模块可以工作在3.4-3.6GHz，可以满足即将到来的 5G 应用的要求。制造并测试了所提出的 MIMO 天线阵列。在不应用任何去耦结构的情况下，在 PIN 二极管的 ON 和 OFF 状态下，所建议天线的测量隔离度超过 15.2 dB。此外，测量的天线效率、辐射方向图、包络相关系数、