## 4 Conclusions  
In this work, a button sensor antenna was presented along with a wearable wireless sensor module for WBAN applications working at two frequency bands, of 2.45 GHz and \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{1}{c}{**Characteristics**} & \multicolumn{2}{c}{**Bending Scenario (Lower/Upper Band)**} \\ \hline
**Antenna Parameters** & **Free Space** & **On-Chest** & **On-Arm** \\ \hline Simulated S\({}_{11}\) (dB) at the Center Frequency & \(-21.55/-21.96\) & \(-17.73/-35.00\) & \(-18.92/-28.11\) \\ \hline Measured S\({}_{11}\) (dB) at the Center Frequency & \(-20.31/-21.05\) & \(-17.25/-33.94\) & \(-17.85/-28.01\) \\ \hline Simulated and Measured Center Frequency (GHz) & \(2.38-2.44/\) & \(2.31-2.48/\) & \(2.31-2.46/\) \\ \(5.01-5.80\) & \(5.01-6.00\) & \(4.76-5.26\) \\ \hline Simulated/Measured Bandwidth (MHz) & \(59.80/814.10\) & \(166.20/982.40\) & \(1261.70/524.20\) \\ \hline Voltage Standing Wave Ratio VSWR & \(1.26/1.18\) & \(1.50/1.02\) & \(1.15/1.05\) \\ \hline Simulated Gain (dBi) & \(1.35/6.09\) & \(1.31/6.35\) & \(0.91/6.45\) \\ \hline Simulated Directivity (dBi) & \(1.78/6.34\) & \(2.8/7.14\) & \(2.31/7.19\) \\ \hline Simulated Directivity (Total Efficiency) \% & \(75.00/95.00\) & \(71.00/82.98\) & \(73.00/85.00\) \\ \((72.00/95.00)\) & \((45.00/81.37)\) & \((48.00/84.00)\) \\ \hline Radiation Pattern Type & Omnidirectional & Omnidirectional & Omnidirectional \\ \hline (10 m/40 m) Path Loss (dB) Minimum/Maximum & \(34/82\) (LoS/NLoS) & \(35/83\) (LoS/NLoS) & \(34/81\) (LoS/NLoS) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Different SAR Values in Bending Positions. \begin{table}
\begin{tabular}{c c c c} \hline \hline Frequency (GHz) & \(1\) g/\(10\) g (On-Body) & \(1\) g/\(10\) g (On-Arm) & SAR Limits \\ \hline
2.73/5.466 & \(1.63/1.56\) & \(0.90/0.54\) & \(0.67/0.67\) & \(0.41/0.37\) \\ \hline \hline \end{tabular}
\begin{tabular}{c c c c} \hline \hline Frequency (GHz) & \(1\) g/\(10\) g (On-Body) & \(1\) g/\(10\) g (On-Arm) & SAR Limits \\ \hline
2.41/5.49 & \(0.89/1.55\) & \(0.57/0.64\) & \(0.95/1.46\) & \(0.54/0.73\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Different SAR Values in Flat Positions. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{1}{c}{**Characteristics**} & \multicolumn{2}{c}{**Button Sensor Antenna (Lower/Upper Band)**} \\ \hline
**Antenna Parameters** & **Free Space** & **On-Chest** & **On-Arm** \\ \hline Simulated S\({}_{11}\) (dB) at the Center Frequency & \(-29.30/-30.97\) & \(-23.07/-27.07\) & \(-30.76/-31.12\) \\ \hline Measured S\({}_{11}\) (dB) at the Center Frequency & \(-27.45/-39.31\) & \(-21.35/-22.05\) & \(-30.15/-27.10\) \\ \hline Simulated and Measured Center Frequency (GHz) & \(2.35/2.44/\) & \(2.33-2.41/\) & \(2.33-2.45/\) \\ \(5.01-5.82\) & \(5.11-6.00\) & \(5.12-5.96\) \\ \hline Voltage Standing Wave Ratio VSWA & \(1.08/1.01\) & \(1.31/1.16\) & \(1.17/1.11\) \\ \hline Simulated Gain (dBi) & \(1.75/5.69\) & \(2.09/6.7\) & \(2.16/5.67\) \\ \hline Directivity (dBi) & \(1.81/6.94\) & \(3.95/8.19\) & \(2.38/6.25\) \\ \hline Simulated Radiation Efficiency (Total Efficiency)\% & \(71.91/92.51\) & \(65.12/81.63\) & \(75.0/87.58\) \\ \((59.26/80.0)\) & \((50.0/75.64)\) \\ \hline Radiation Patterns & Omnidirectional & Omnidirectional & Omnidirectional \\ \hline (2 m/40 m) Path Loss (dB) Minimum/Maximum & \(34/82\) & \(35/84\) & \(34/83\) \\ \hline Severe Bending and Crumpling Conditions/Wet Conditions & High Stability & Good Stability & Good Stability \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Summary Performance of the Proposed Button Sensor Antenna in Flat Position. 5.6 GHz. The device is small, button-shaped, with an area of 45 \(\times\) 45 mm\({}^{2}\), and it can be fitted into a 45 mm diameter circular-shaped wireless sensor module that is enclosed into a 3D enclosure as large as a hand-watch cover for users' convenience.