# Design and SAR Analysis of a Dual Band Wearable Antenna for WLAN Applications
## 3 Results
### Off-Body Analysis
#### 3.1.3 Conventional Antenna in Different Free Space Bending Conditions  
The primary utilization of wearable antennas is their usage in on-body health or sports equipment or in security gadgets. All these applications are wearable in nature, and hence, it is impossible to maintain a regular flat antenna condition all the time when these gadgets are worn on the wearer's body. Consequently, the antenna bending phenomenon occurs during its regular operation, which can adversely affect the performance of the corresponding system of gadget installed with the antenna. For this reason, a thorough analysis of a wearable antenna in various bending conditions can result in improved designs and better results in future wearable systems. Therefore, we used the conventional dual band wearable antenna as given in Figure 1 and bent it around different body parts as shown in Figure 8. In this work, we analyzed our proposed conventional antenna by evaluating its various bending conditions on the basis of its return loss and radiation characteristics. We describe our analysis of various results of the antenna system below.  
Figure 17 illustrates the effects on the return loss of the conventional dual band wearable antenna due to bending around a leg with a radius of 70 mm, a healthy arm with a radius of 60 mm, and the worst case, which is a child's arm with a radius of 40 mm. It is worth noticing that irrespective of the bending radii, the return loss result of the antenna is  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multicolumn{2}{c}{**Conventional**} & \multicolumn{2}{c}{**Mushroom-like**} & \multicolumn{2}{c}{**EBG with Plus-**} \\  & **Dual Band** & \multicolumn{2}{c}{**EBG-Based**} & \multicolumn{2}{c}{**Shaped Slots-**} \\  & **Antenna** & \multicolumn{2}{c}{**Antenna**} & \multicolumn{2}{c}{**Based Antenna**} \\ \hline Frequency (GHz) & 2.5 & 5.196 & 2.452 & 5.192 & 2.528 & 5.208 \\ \hline Bandwidth (MHz) & 23.8 & 60.4 & 29 & 94 & 31.7 & 77.1 \\ \hline Return loss (dB) & \(-24.975\) & \(-28.234\) & \(-19.82\) & \(-24.41\) & \(-24.06\) & \(-19.25\) \\ \hline Directivity (dB) & 8.39 & 9.01 & 8.55 & 11.6 & 9.66 & 9.33 \\ \hline Gain (dBi) & 8.08 & 8.74 & 8.43 & 11.4 & 9.43 & 9.14 \\ \hline Radiation Efficiency (\%age) & 93.06 & 93.94 & 97.43 & 96.17 & 94.89 & 95.71 \\ \hline Total efficiency (\%age) & 92.76 & 93.80 & 96.41 & 95.82 & 94.52 & 94.58 \\ \hline Angular width (Deg) & 83.4 & 76.9 & 80.2 & 99.4 & 62.8 & 70.2 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Performance comparison of proposed dual band antennas with and without EBG ground planes.  
Figure 16: Gain patterns without and with EBG ground planes at **(a)** 2.5 GHz and **(b)** 5.2 GHz.  
stable when bent on these body parts. The return loss is improved by about 15.16 dB at 2.5 GHz for bending around the radius of a child's arm (40 mm). Similarly it is improved by about 5.68 dB at 5.2 GHz for bending around a leg of radius 70 mm. It is clear from Figure 17 that the bending radii have no prominent effects on the return loss of the proposed dual band wearable antenna.  
Figures 18 and 19 portray the effects on the directivity and gain patterns, respectively, at the desired resonance frequencies when the proposed conventional dual band patch antenna is bent around body parts of different radii. It is worth mentioning that a very small amount of reduction in directivity and gain for the lower frequency band is observed as the bending radius decreases. However, there is no prominent effect of the bending on the radiation characteristics of the conventional patch antenna, and its overall performance remains stable in terms of return loss and radiation patterns.  
Figure 17: Off-body reflection coefficient of the conventional dual band antenna.  
Figure 18: Off-body directivity patterns of the conventional dual band antenna at **(a)** 2.5 GHz and **(b)** 5.2 GHz.