# Design of Multi-Mode Antenna Array for Use in Next-Generation Mobile Handsets
## 7 User Effects on the Characteristics of the Designed Antenna Array  
The health hazards of emitted electromagnetic (EM) radiation from mobile handsets has become a point of open deliberation as the use of mobile handsets is increasing exponentially [74]. For mobile handsets, the investigation of the user-effect on the characteristics of the antenna is indispensable [75]. Below, different usage postures in the data-mode of the user-hand for right and left hands are considered and studied in Figures 14 and 15, respectively. The employed user-hand phantom in the simulation has a relative permittivity of \(\varepsilon=24\) and conductivity of \(\sigma=2\) s/m [76]. According to the obtained results, the proposed design exhibits similar radiation behavior for different hand scenarios. This is mainly due to the symmetrical schematic of the designed MIMO antenna. It is shown that the handset antenna and its modified PIFA elements exhibit good efficiencies. Besides, when the antenna frequency increases, the efficiency of the antenna is improved. The reflection coefficients (S\({}_{\text{nn}}\)) of the proposed \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Reference** & **Antenna Type** & **Elements** &
\begin{tabular}{c} **Bandwidth** \\ **(GHz)** \\ \end{tabular} & **Efficiency (\%)** & **Overall Size (mm\({}^{2}\))** & **Isolation (dB)** & **ECC** \\ \hline \multicolumn{8}{c}{**Single-Band MIMO Handset Antennas**} \\ \hline
[16] & Coupled-Fed & 8 & 2.55-2.68 & 48-63 & \(136\times 68\) & 12 & \textless{}0.15 \\
[17] & Petal Slot & 8 & 2.55-2.66 & - & \(150\times 75\) & 10 & \textless{}0.1 \\
[18] & Loop & 8 & 2.55-2.6 & 48-63 & \(136\times 68\) & 11 & \textless{}0.15 \\
[19] & PIFA Slot & 8 & 3.4-3.6 & 62-78 & \(140\times 70\) & 10 & \textless{}0.20 \\
[20] & Slot-Ring & 8 & 3.4-3.8 & 55-70 & \(150\times 75\) & 15 & \textless{}0.05 \\
[21] & Patch-Slot & 8 & 3.55-3.65 & 52-76 & \(150\times 75\) & 11 & - \\
[22] & Loop Element & 8 & 3.33-3.6 & 40 & \(120\times 70\) & 15 & \textless{}0.02 \\
[23] & CPW-Fed Slot & 8 & 3.4-4.4 & 65 & \(150\times 75\) & 16 & \textless{}0.01 \\
[24] & Monopole & 8 & 4.55-4.75 & 50-70 & \(136\times 68\) & 10 & - \\ \hline \multicolumn{8}{c}{**Dual-Band MIMO Handset Antennas**} \\ \hline
[25] & Coupled-Fed & 10 & 3.4-3.8 & 41–84 & \(150\times 80\) & 12 & \textless{}0.15 \\  & Slot & 5.15-5.92 & 47–79 & & & \\
[26] & Dual Mode & 2 & 3.4-3.6 & 50-61, & \(150\times 76.6\) & 10.5 & \textless{}0.2 \\  & Monopole & 2 & 5.725-8.875 & 67–80 & & \\
[27] & Cuboid & 6 & 2.6-2.7 & 60–70 & & \\  & Monopole & 6 & 5.1–5.9 & 70–80 & \(140\times 05\) & 10 & \textless{}0.05 \\
[28] & Monopole & 8 & 3.2–3.9 & 60–80 & & \\
[28] & Monopole & 8 & 5–5.5 & 70–85 & \(150\times 75\) & 12 & - \\
[29] & Folded & 2.45-2.6 & 40–60 & & \(124\times 74\) & 15 & \textless{}0.2 \\  & Monopole & 8 & 3.45-3.65 & 50–80 & & \\ \hline \multicolumn{8}{c}{**Tri-Band MIMO Handset Antennas**} \\ \hline
[30] & Coupled-Fed & 8 & 3.3-3.8 & 55–72, & & \\ Arm & 8 & 4.8-5, & 50–65, & \(130\times 70\) & 10 & \textless{}0.1 \\  & & 5.1–5.9 & 43–73 & & \\  & & 2.40-2.48 & 44–48, & & \\
[31] & Yet-Decoupled & 2 & 5.15-5.35, & 74–80, & \(150\times 75\) & 15 & \textless{}0.14 \\  & Antennas & 5.72–5.92 & 75 & & \\  & & 3.3–4.2, & & & \\
[32] & F-Shaped & 4 & 4.4–5, & 60–80 & \(150\times 75\) & 12 & \textless{}0.1 \\  & Monopole & 5.15–5.85 & & & \\  & & **2.45-2.65,** & **40–65,** & & \\
**Proposed** & **Diversity PIFA** & **8** & **3.4-3.75,** & **50–70,** & **150\times 75** & **11** & **\textless{}0.01** \\  & & **5.6-6** & **60–80** & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of the design characteristics with the referenced handset antennas. MIMO: multiple-input–multiple-output. array are not affected drastically by the hand, except for some small frequency fluctuations. However, the antenna efficiencies of the proposed array are affected significantly owing to the absorption effect of the user's hand. This is because some EM energy has been absorbed by the hand [77].