In this letter, a dual-band 8 × 8 multiple-input–multiple-output (MIMO) antenna that operates in the sub-6 GHz spectrum for future 5G MIMO smartphone applications is presented. The design consists of a fully grounded plane with closely spaced orthogonal pairs of antennas placed symmetrically along the long edges and on the corners of the smartphone. The orthogonal pairs are connected by a 7.8 mm short neutral line for mutual coupling reduction at both bands. Each antenna element consists of a folded monopole with dimensions 17.85 × 5 mm$^2$ and can operate in 3100–3850 MHz for the low band and 4800–6000 MHz for the high band ($|$$S_{11}$$|$ $< $ 10 dB). The fabricated antenna prototype is tested and offers good performance in terms of envelope correlation coefficient (ECC), mean effective gain (MEG), total efficiency, and channel capacity. Finally, the user effects on the antenna and the specific absorption rate (SAR) are also presented.

中文翻译：

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用于 5G 智能手机的低于 6 GHz 双频 8x8 MIMO 天线

在这封信中，介绍了一种双频 8 × 8 多输入多输出 (MIMO) 天线，该天线在低于 6 GHz 的频谱中运行，适用于未来的 5G MIMO 智能手机应用。该设计由一个完全接地的平面和紧密间隔的正交天线对组成，这些天线对沿着智能手机的长边和角落对称放置。正交对通过 7.8 毫米短中性线连接，以减少两个频段的相互耦合。每个天线元件由尺寸为 17.85 × 5 mm 的折叠单极子组成$^2$ 并且可以在低频段的 3100-3850 MHz 和高频段的 4800-6000 MHz 下运行（$|$$S_{11}$$|$ $< $10 分贝）。制造的天线原型经过测试，在包络相关系数 (ECC)、平均有效增益 (MEG)、总效率和信道容量方面具有良好的性能。最后，还介绍了用户对天线和比吸收率 (SAR) 的影响。