In this article, compact inverted F-antennas (IFAs) operating in the 3.5 GHz band is proposed for future 5G smartphone applications. The conventional IFA is modified to make the structure compact and efficient. The additional IFAs are aligned in face-to-face configuration to reduce the coupling between them up to some extent. Furthermore, a novel decoupling element is incorporated between antenna pairs to effectively enhance the isolation. As a result, the proposed building block exhibits isolation higher than 28.2 dB between two adjacent ports. Based on highly isolated building blocks, a 4 × 4 and 8 × 8 multi-input multi-output (MIMO) antenna array is designed and investigated which is operated in 3.5 GHz (LTE band 42). The proposed 8 × 8 MIMO antenna array has four compact building blocks and reserves sufficient space for integrating other antennas such as 2G/3G/4G antennas. To validate the simulated results, a prototype of the proposed antenna is fabricated and tested. Over the entire operating frequency, the fabricated 8 × 8 MIMO antenna array obtain high isolation of more than 27.3 dB, and high antenna efficiency (>61%). Also, its corresponding measured envelope correlation coefficients are lower than 0.04 and channel capacity was about 39.1–40.6 bps/Hz. The measured results show that the proposed MIMO antenna array is a good candidate for future fifth-generation smartphone applications.

中文翻译：

---

适用于 5G 智能手机应用的 8 × 8 多输入多输出天线阵列的紧凑型高隔离构建块

在本文中，针对未来的 5G 智能手机应用，提出了在 3.5 GHz 频段运行的紧凑型倒 F 天线 (IFA)。对传统的IFA进行了修改，使结构紧凑高效。额外的 IFA 以面对面的配置对齐，以在一定程度上减少它们之间的耦合。此外，在天线对之间加入了一种新颖的去耦元件，以有效增强隔离度。因此，建议的构建块在两个相邻端口之间表现出高于 28.2 dB 的隔离度。基于高度隔离的构建块，设计并研究了 4 × 4 和 8 × 8 多输入多输出 (MIMO) 天线阵列，该天线阵列在 3.5 GHz（LTE 频段 42）下运行。拟议的 8 × 8 MIMO 天线阵列具有四个紧凑的构建块，并为集成其他天线（如 2G/3G/4G 天线）预留了足够的空间。为了验证仿真结果，我们制作并测试了所提出天线的原型。在整个工作频率上，制造的8×8 MIMO天线阵列获得了超过27.3 dB的高隔离度和高天线效率（> 61％）。此外，其相应的测量包络相关系数低于 0.04，信道容量约为 39.1–40.6 bps/Hz。测量结果表明，所提出的 MIMO 天线阵列是未来第五代智能手机应用的良好候选者。制作的8×8 MIMO天线阵列获得超过27.3 dB的高隔离度和高天线效率（>61%）。此外，其相应的测量包络相关系数低于 0.04，信道容量约为 39.1–40.6 bps/Hz。测量结果表明，所提出的 MIMO 天线阵列是未来第五代智能手机应用的良好候选者。制作的8×8 MIMO天线阵列获得超过27.3 dB的高隔离度和高天线效率（>61%）。此外，其相应的测量包络相关系数低于 0.04，信道容量约为 39.1–40.6 bps/Hz。测量结果表明，所提出的 MIMO 天线阵列是未来第五代智能手机应用的良好候选者。