# Minimized Triple-Band Eight-Element Antenna Array for 5G Metal-frame Smartphone Applications
## 5 Conclusions  
In this paper, a minimized triple-band eight-element antenna array covering 3.3-3.8 GHz, 4.8-5 GHz, and 5.15-5.925 GHz has been proposed. The single antenna element consists of an S-shaped feeding strip and an L-shaped radiation strip on the metal frame. The size of a single antenna element is only 6.5 mm \(\times\) 7 mm, which is the innovation point of this paper. The measured total efficiencies are larger than 70%, and the isolations are better than 13 dB, respectively. The antenna was verified by both simulation and measurement. The proposed antenna element has the advantage of comprehensive performance under the minimum size. Therefore, it is a good candidate for 5G mobile handsets.  
Conceptualization, J.H.; methodology, T.H.L.; data curation, Z.C.; investigation, Q.C.; writing--original draft preparation, J.H.; writing--review and editing, T.H.L. and G.L.; supervision and funding acquisition, G.L. All authors have read and agreed to the published version of the manuscript.  
This work was funded in part by the Science and Technology Department of Zhejiang Province under Grant No. LGG19F010009, the National Natural Science Foundation of China under Grant No. 61671330, and Wenzhou Municipal Science and Technology Program under Grant No. C20170005 and No. 2018 ZG019. The work of [PERSON] was supported by the 2021-2025 National Measurement System Programme of the U.K. Government's Department for Business, Energy and Industrial Strategy, through the Science Theme Reference EMT21 of that Programme.  
The data presented in this study are available on request from the corresponding author.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Reference** &
\begin{tabular}{c} **Operating Band** \\ **(GHz)** \\ \end{tabular} & **Isolation(dB)** & **ECC** & **Efficiency (\%)** & **Size(mm\({}^{3}\))** \\ \hline
[5] &
\begin{tabular}{c} 3.4–3.8 \\ 4.8–5 (\(-6\) dB) \\ \end{tabular} & \textgreater{}15.5 & \textless{}0.06 & 40–85 & \(15.2\times 7\times 0.8\) \\ \hline
[6] &
\begin{tabular}{c} 3.3–3.6 \\ 4.8–5 (\(-10\) dB) \\ \end{tabular} & \textgreater{}12 & \textless{}0.15 & \textgreater{}45 & \(10.6\times 5.3\times 0.8\) \\ \hline
[7] &
\begin{tabular}{c} 3.4–3.6 \\ 4.8–5.1 (\(-6\) dB) \\ \end{tabular} & \textgreater{}11.5 & \textless{}0.05 & 40–85 & \(15\times 7\times 0.8\) \\ \hline
[8] &
\begin{tabular}{c} 3.4–3.6 \\ 5.15–5.925 (\(-10\) dB) \\ \end{tabular} & \textgreater{}11.2 & \textless{}0.08 & 51–59 & \(10\times 10\times 0.8\) \\ \hline
[9] &
\begin{tabular}{c} 3.3–4.2 \\ 4.8–5 (\(-6\) dB) \\ \end{tabular} & \textgreater{}10 & \textless{}0.1 & 53.8–79.1 & \(18.6\times 7\times 0.8\) \\ \hline
[10] &
\begin{tabular}{c} 3.4–3.6 (\(-6\) dB) \\ 5.72–5.875 (\(-10\) dB) \\ \end{tabular} & \textgreater{}17.1 & \textless{}0.045 & 45–62 & \(14.9\times 7\times 0.8\) \\ \hline
[11] &
\begin{tabular}{c} 3.3–3.8 \\ 4.8–5 \\ 5.15–5.925 (\(-10\) dB) \\ \end{tabular} & \textgreater{}18 & \textless{}0.06 & 60–75 & \(15.8\times 7\times 0.8\) \\ \hline
[13] & \
\begin{tabular}{c} 3.3–6 (\(-10\) dB) \\ \end{tabular} & \textgreater{}10 & \textless{}0.1 & 40–70 & \(13.9\times 7\times 0.8\) \\ \hline Pro. &
\begin{tabular}{c} 3.3–3.8 \\ 4.8–5 \\ 5.15–5.925 (\(-6\) dB) \\ \end{tabular} & \textgreater{}13 & \textless{}0.1 & \textgreater{}70 & \(6.5\times 7\times 0.8\) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Comparison of the 5G MIMO smartphone antennas.