# Design of MIMO Antenna with Double L-Shaped Structure for 5G NR
## 4 Effect of User's Hand  
The practical antenna performance is discussed in this section. As depicted in Figure 13, the most commonly used operation modes of the antenna embedded in a smartphone are single-handset mode (SHM) and double-handset mode (DHM). The effect on the user's head will not be discussed here because the operation is only for data transmission and not for call mode.  
Figure 13a shows the hand configuration with the proposed antenna design in one-handed mode (SHM). Similarly, Figure 13b shows the proposed antenna design in two-handed mode (DHM). Because of their direct contact with the finger, Ant5, Ant6, Ant7, Ant8, and Ant2 exhibit high reflection coefficients under SHM, as shown in Figure 14a. In contrast, because they are farther away from the fingers and still operate in the 3.4-4.7 GHz band, Ant1, Ant3, and Ant4's reflection coefficients are less affected. Ant1, Ant3, and Ant4's reflection coefficients, on the other hand, are less affected because they are farther away from the fingers and still cover the 3.4-4.7 GHz band. Their reflection coefficient, however, is slightly higher than in the situation with no hand interference. Nonetheless, the isolation over the entire/desired operating band is greater than 10 dB for all antennas. Besides, as shown in Figure 14c, the radiation efficiency of Ant6 and Ant7 reduces to less than 65%, since the hand tissue can absorb electromagnetic waves. Similarly, Ant2 and Ant8 are also less efficient owing to their proximity to the palm. On the contrary, Ant1 and Ant4 are located far from the hand and hence show efficiency greater than 80%.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**References** & **Bandwidth (GHz)** & **Isolation (dB)** & **ECC** & **Total Efficiency (\%)** \\ \hline
[6] & 3.4–3.6(\(-\)10 dB) & \textgreater{}10 & \textless{}0.2 & 62–78 \\
[17] & 3.4–3.6(\(-\)6 dB) & \textgreater{}10 & \textless{}0.15 & 40–52 \\
[28] & 3.3–3.8(\(-\)10 dB) & \textgreater{}18 & \textless{}0.01 & 87–93 \\
[29] & 2.496–2.69, 3.4-3.8(\(-\)6 dB) & \textgreater{}10.5 & \textless{}0.2 & 44–46 \\
[30] & 3.3–4.2(\(-\)6 dB) & \textgreater{}9.5 & \textless{}0.06 & 40–58 \\
[31] & 3.4–3.6(\(-\)6 dB) & \textgreater{}11 & \textless{}0.23 & 40–53 \\
[32] & 3.3–4.2(\(-\)6 dB) & \textgreater{}12 & \textless{}0.1 & 50–77 \\
[8] & 3.4–3.6(\(-\)6 dB) & \textgreater{}12.7 & \textless{}0.13 & 29.2–54 \\ Proposed & 3.4–4.7(\(-\)6 dB) & \textgreater{}11 & \textless{}0.08 & 87–96 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Performance comparison of various state of the art 5G antennas.  
Figure 13: Two application scenarios for a hand-held smartphone. (**a**) SHM. (**b**) DHM. The practical antenna performance is discussed.  
As shown in Figure 15a, only Ant5 and Ant8 are in direct contact with the fingers for DHM, while all other antenna elements are not. Ant5 and Ant8 have significantly higher reflection coefficients because they are covered by the thumb. The radiation efficiency of the antenna elements that are not in contact with the fingers or palm remains greater than 85% over the entire operating band, as shown in Figure 15b. However, for Ant5 and Ant8 that were in contact with the finger, the efficiency was significantly reduced, with a maximum efficiency of only around 60%.  
Figure 14: Simulated parameters under SHM. (**a**) Reflection coefficient. (**b**) Transmission coefficient. (**c**) Total efficiency.