## 3 Results
### Measurements  
Due to less stringent fabrication requirements for the meandered antenna (Antenna II), it was selected as a sample for fabrication and validation of the simulation results. The fabricated structure of antenna II with and without the superstrate is shown in Figure 7a.  
Figure 6: Impact of different bodies on antenna characteristics is shown. A fat body voxel is compared to a normal body type in Figure 4. (**a**) percentage of the resonant frequency variation in normal and overweight voxels are compared, (**b**) percentage of the bandwidth variation in the normal and overweight voxels are illustrated, and (**c**) overweight human voxel and the positions of the antenna’s placement are shown.  
Figure 7: (**a**) Fabricated structure of the antenna with and without superstrate. (**b–d**) Measurement of the relative permittivity of equivalent phantoms at the three bands.  
Mixtures of n-butanol, propanol, salt, and purified water with TDS = 5, at different concentrations, were prepared and measured by an open-ended coaxial line [39; 40] to make sure the effective EM characteristics of the equivalent three-layer phantom in each frequency band are in good agreement with that of the human tissues (skin, fat, and muscle). The percentage of each material is illustrated in Table 3 in each frequency [41; 42]. The results are shown versus the frequency at each band in Figure 7b-d.  
The S\({}_{11}\) measurement results are illustrated in Figure 8a-c. The results show a good agreement in the first two bands, between test results and the simulation results of the three-layer mode, but some discrepancies are observed in the third frequency band. The reasons are the nonideal behavior of the connectors, ports, and coaxial cables at 5.7 GHz. The coaxial cable connection to the antenna was done by hand, and this creates impedance mismatches since the input impedance becomes more sensitive to the location of the feeding point as the frequency increases. Furthermore, the need for a thin protective layer on the antenna (with a relative permittivity of approximately 3) to avoid penetration of the liquid to the substrate and replacing a one-layer liquid phantom instead of the three-layer phantom in the measurement are the other reasons for the small differences between simulations and measurement results.  
Figure 8: (**a–c**) Measurement of the S\({}_{11}\) of the fabricated meandered antenna in the equivalent phantom along with the simulation results of the three-layer model with no coating layer and the one-layer equivalent phantom with the coating layer at the three bands.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Volume** & \multirow{2}{*}{**N-Butanol 96\%**} & \multirow{2}{*}{**Propanol 99\%**} & \multirow{2}{*}{**Purified Water**} & \multirow{2}{*}{**Salt**} & \multirow{2}{*}{**Frequency Band**} \\
**Percentage** & & & & TDS = 5 & \\ \hline Phantom 1 & 49 & 49 & 1.9 & 0.1 & 400 MHz \\ Phantom 2 & 31 & 31 & 37.7 & 0.3 & 2.4 GHz \\ Phantom 3 & 12.5 & 12.5 & 74.35 & 0.15 & 5.6 GHz \\ \hline \hline \end{tabular}
\end{table}
Table 3: Materials of the liquid phantoms.  
In order to show the effect of the thin protective coating layer and the use of one-layer liquid phantom in the measurement compared to the real three-layer phantom in the simulation, simulation results of the one-layer equivalent phantom with a coating layer are also shown along with the measurement results and the original simulation of the three-layer model with no coating in Figure 8. As expected, the use of a one-layer equivalent phantom with the coating results in a resonance frequency shift to a lower value, and it explains the small discrepancy observed between the measurement results and simulation of the three-layer model with no coating observed in Figure 8b,c. It should also be noted that the effect of the use of a one-layer equivalent phantom with a coating layer is less as frequency decreases, and it is negligible at the 400 MHz band.