## 6 Results and Discussion  
Finite Integration Technique (FIT)-based electromagnetic simulator CST microwave studio was used to analyse the S-parameter and the various material characteristics parameters. Figure 13 illustrates the CST results of the reflection coefficient and transmission coefficient. The simulated result of S\({}_{21}\) exhibited triple band resonance at 2.38 GHz, 4.55 GHz and 9.42 GHz with the magnitudes of \(-29.40\) dB, \(-39.65\) dB and \(-43.35\) dB, respectively. Meanwhile, S\({}_{11}\) is observed at 2.64 GHz, 5.65 GHz and 11.2 GHz with magnitudes of \(-34.85\) dB, \(-27.38\) dB and \(-17.19\) dB, respectively. The bandwidths of three resonance peaks for the concerned bands are shown in Figure 13: These are 0.124 GHz at S-band, 0.597 GHz at C-band and 1.288 GHz at X-band. Figure 13 indicates that the first resonance of the reflection coefficient (S\({}_{11}\)) pursued by the minimum value of transmission coefficient (S\({}_{21}\)). Every minimum frequency of S\({}_{11}\) is lower than that of the corresponding S\({}_{21}\) maximum frequency, where each resonance of the unit cell was addressed as an electrical resonance. Meanwhile, Figures 14-16 represent the three important material characteristics, namely, the permittivity (\(\epsilon_{\mathrm{r}}\)), permeability (\(\mu_{\mathrm{r}}\)) and refractive index (n) derived using NRW method via MATLAB programming code. According to Figure 14, the is noticed that resonance of transmission coefficient (S\({}_{21}\)) just started while the values of \(\epsilon\) changes from highest to the lowest. The smallest value of permeability (\(\mu\)) was achieved when the value of the reflection coefficient (S\({}_{11}\)) was the lowest (Figure 15). At the positive permeability, the value of permittivity shifted from positive to negative. The refractive index (n) of a material is also regarded as a function of frequency. It denoted a negative value when permittivity (\(\epsilon\)) was negative, as demonstrated in Figure 16. The permittivity of the proposed metamaterial was negative for a certain frequency range. Therefore, it can be termed as an \(\epsilon\)-negative (ENG) metamaterial. The Drude equation can be used to explain the negative permittivity [33]:  
\[\epsilon(\omega)=\frac{\omega(\omega+\mathrm{i}\Gamma)-\omega_{\mathrm{p}}^{2} }{\omega(\omega+\mathrm{i}\Gamma)} \tag{14}\]  
where \(\Gamma\) and \(\omega_{\mathrm{p}}\) denote the energy disintegration attenuation function in the plasmons and plasmon frequency, respectively. If the losses \(\Gamma\approx 0\) and \(\omega<\omega_{\mathrm{p}}\), then the permittivity \(\epsilon\) becomes negative. This artificial characteristic of the projected MM is utilised in many types of wireless communication such as antenna bandwidth development [34]. Furthermore, the other NRI properties can numerously be used to enhance the antenna gain, cloaking and application.  
Figure 12: Transmission coefficients (S\({}_{21}\)) result for CST and ADS simulation.  
Figure 14: Permittivity (\(\epsilon\)) of real and imaginary magnitude for the unit cells.  
Figure 13: CST-simulated result of reflection coefficient (S\({}_{11}\)) and transmission coefficient (S\({}_{21}\)) of a unit cell.