# Compact Sub 6 GHz Dual Band Twelve-Element MIMO Antenna for 5G Metal-Rimmed Smartphone Applications
## 7 Conclusions
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Ref.**} & \multirow{2}{*}{**Total Size (mm\({}^{3}\))**} & \multirow{2}{*}{**Element Size (mm\({}^{2}\))**} & \multirow{2}{*}{**Metal-Frame**} & \multirow{2}{*}{\
\begin{tabular}{c} **Operating** \\ **Bands** \\ **(MHz)** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Spacing** \\ **between** \\ **Two-Antenna** \\ **Units (mm)** \\ \end{tabular} } & \multirow{2}{*}{**Isolation**} & \multirow{2}{*}{**Eff.**} & \multirow{2}{*}{**ECC**} & \multirow{2}{*}{**MIMO**} \\  & & & & & & & & **Order** \\ \hline
[8] & \(155\times 76\times 7.5\) & 6.78 \(\times\) 6.7 & Yes & 4400-5000 & \(\geq\)31 & \(\geq\)22 & \(\geq\)50\% & \(\leq\)0.049 & 8 \\
[9] & \(145\times 75\times 6\) & \(\begin{array}{c}29\times 8.75\\ 10\times 5\end{array}\) & Yes & 3300-3600 & \(\geq\)18 & \(\geq\)20 & \(\geq\)49.4\% & \(\leq\)0.013 & 8 \\
[10] & \(150\times 75\times 6\) & \(\begin{array}{c}114\times 8.4\end{array}\) & Yes & 3300-6000 & \(\geq\)22 & \(\geq\)12.8 & \(\geq\)50\% & \(\leq\)0.06 & 8 \\
[11] & \(147\times 76\times 7\) & \(\begin{array}{c}14.5\times 1.5\end{array}\) & Yes & 3300-6000 & \(\geq\)12.5 & \(\geq\)11.4 & \(\geq\)46\% & \(\leq\)0.26 & 8 \\  & & 59.2 \(\times\) 2 & & 824-960 & & & & & 2 \\
[14] & \(158\times 72\times 7\) & \(\begin{array}{c}40\times 2\end{array}\) & Yes & 1710-3800 & \(\geq\)21 & \(\geq\)15 & \(\geq\)31\% & \(\leq\)0.3 & 2 \\  & & 18.5 \(\times\) 2 & & 4800-5825 & & & & & 4 \\  & & 56.7 \(\times\) 25.3 & & 698-960 & & & & & 2 \\
[15] & \(158\times 73\times 7\) & \(\begin{array}{c}15\times 25.3\end{array}\) & Yes & 1710-2690 & \(\geq\)50.4 & N/A & \(\geq\)17\% & \(\leq\)0.48 & 2 \\  & & 14.55 \(\times\) 2 & & 3300-4500 & & & & & 4 \\ \hline
[16] & \(140.6\times 70.6\times 6\) & \(\begin{array}{c}28\times 2\end{array}\) & Yes & 3300-3800 & Shared dipole & \(\geq\)16 & \(\geq\)68\% & \(\leq\)0.1 & 4 \\
[17] & \(140.6\times 70.6\times 6\) & \(\begin{array}{c}67\times 2\end{array}\) & Yes & 3400-3600 & Shared loop & \(\geq\)16 & \(\geq\)55\% & \(\leq\)0.1 & 4 \\
[18] & \(150\times 75\times 7.5\) & \(\begin{array}{c}29\times 3\end{array}\) & Yes & 3400-3600 & \(\geq\)30 & \(\geq\)24 & N/A & N/A & 4 \\
[19] & \(160\times 80\times 7\) & \(\begin{array}{c}14.5\times 1.5\end{array}\) & No & 3300-3800 & \(\geq\)11.5 & \(\geq\)10 & \(\geq\)58\% & \(\leq\)0.2 & 12 \\
[20] & \(150\times 75\times 7\) & \(\begin{array}{c}20\times 6.5\end{array}\) & No & 3400-3600 & \(\geq\)8 & \(\geq\)10 & \(\geq\)61\% & \(\leq\)0.15 & 12 \\
[21] & \(150\times 80\times 0.8\) & \(\begin{array}{c}18.2\times 7.5\end{array}\) & No & 3400-3800 & \(\geq\)9.1 & \(\geq\)14.8 & \(\geq\)74\% & \(\leq\)0.05 & 12 \\ Proposed & \(165\times 85\times 7\) & \(\begin{array}{c}15\times 3\end{array}\) & Yes & 3300-3600 & & \(\geq\)10 & \(\geq\)36\% & \(\leq\)0.38 & 12 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Performance comparison of MIMO antenna systems. **Author Contributions:** Conceptualization, S.-H.C. and S.-C.C. ; methodology, C.-C.L., S.-C.C. and C.-S.W. ; software, C.-C.L., S.-H.C. and C.-S.W. ; validation, S.-H.C.; visualization, C.-C.L. ; writing--original draft preparation, C.-C.L. and C.-S.W. ; writing--review and editing, S.-H.C.; supervision, S.-C.C. ; project administration, S.-C.C. and S.-H.C.; funding acquisition, S.-H.C. and S.-C.C. All authors have read and agreed to the published version of the manuscript. **Funding:** This work was sponsored by the National Science and Technology Council of Taiwan under grants MOST 111-2221-E606-003 and MOST 111-2221-E606-004. **Data Availability Statement:** Not applicable. **Conflicts of Interest:** The authors declare no conflict of interest.