# Metamaterial Integrated Folded Dipole Antenna with Low SAR for 4G, 5G and NB-IoT Applications
## 4 Metamaterial Integrated Antenna Design
An omnidirectional pattern is observed in the polar plane without the metamaterial. However, the metamaterial integrated antenna results in less emission in the lower half and greater emission in the upper half, especially at high frequency bands. Thus, the pattern was proven to be a good design for SAR reduction. \begin{table}
\begin{tabular}{c c c c} \hline
**Band No.** & \begin{tabular}{c} **Gain without Metamaterial** \\ **(dB)** \\ \end{tabular} & \
\begin{tabular}{c} **Gain with Metamaterial** \\ **(dB)** \\ \end{tabular} &
\begin{tabular}{c} **Band Name** \\ \end{tabular} \\ \hline B2U & 2.477 & 2.998 & \\ \hline B2D & 2.609 & 3.232 & \\ \hline B25U & 2.481 & 3.002 & IoT Bands \\ \hline B25D & 2.611 & 3.238 & \\ \hline B1U & 2.596 & 3.202 & \\ \hline B1D & 2.768 & 3.619 & \\ \hline
35 & 2.583 & 3.084 & \\ \hline
39 & 2.634 & 3.153 & \\ \hline
33 & 2.657 & 3.184 & Low frequency LTE bands \\ \hline
37 & 2.678 & 3.213 & \\ \hline
36 & 2.743 & 3.309 & \\ \hline
34 & 2.794 & 3.403 & \\ \hline
40 & 2.656 & 3.788 & \\ \hline
41 & 2.716 & 4.340 & Middle frequency LTE Bands \\ \hline
38 & 2.718 & 4.346 & \\ \hline
42 & 3.825 & 6.701 & \\ \hline
43 & 3.893 & 6.668 & High frequency LTE bands \\ \hline n78 & 4.044 & 6.824 & 5G NR \\ \hline \end{tabular}
\end{table} 
Table 4: Effect of metamaterial on antenna gain. Figure 18: Fabricated prototype of the metamaterial integrated antenna. Despite showing good antenna performance for mobile communication, the design needs to be incorporated with consideration of the radiation impacts on the human body [36]. The harmful effects of radiation can be investigated with the \(SAR\) evalua  
Figure 19: Measured and simulated S parameter for metamaterial integrated antenna. Figure 20: Metamaterial integrated antenna radiation pattern in the azimuth plane. (**a**) Low frequency bands. (**b**) Middle frequency bands. (**c**) High frequency bands. Figure 21: Metamaterial integrated antenna radiation pattern in the polar plane. (**a**) Low frequency bands. (**b**) Middle frequency bands. (**c**) High frequency bands. tion of antenna design on the human body. \(SAR\) is the means of measuring absorbed radiations by the human body [37] and is expressed as:  
\[SAR=\frac{\sigma\left|E\right|^{2}}{\rho} \tag{10}\]  
where \(E\) is the induced electric field, \(\sigma\) is the conductivity of tissue and \(\rho\) is the tissue density. There are various factors affecting the \(SAR\) value, such as the tissue properties, geometry and spacing from the antenna. The \(SAR\) simulation was examined using the CST SAM (Specific Anthropomorphic Mannequin) head phantom, because the antenna is designed for mobile applications and the head is the most exposed part in mobile radiation. The SAM consists of a plastic shell filled with tissue simulating liquid, and was defined for standardized certification purposes based on the 90 th percentile of the head size of the male population [38]. The designed antenna is placed near to the left ear at a distance of d; the simulation setup for SAR analysis is illustrated in Figure 22.  
According to the FCC guidelines, the maximum \(SAR\) is restricted to 2 W/kg averaged over 10 g of human tissue and 1.6 W/kg averaged over 1 g of human tissue. The averaging method used in this analysis is per the IEEE C95.3 standard. The \(SAR\) is analyzed at 100 mW of input power for 1 g of tissue at a distance of 1 mm from the human head. It was observed from the SAR analysis that the peak SAR value for the antenna without the metamaterial is less than 0.6751 W/kg for all the bands. On the other hand, the metamaterial integration results in dwindling the SAR values by a significant amount with the lowest SAR of 0.0732 W/kg. The maximum SAR value observed for the antenna without the metamaterial was for band B25U, which was reduced by 57.47% with the integration of the metamaterial. The use of the metamaterial in the antenna design results in less radiation in the upper half for the polar plane.