## 2 Metamaterial Unit Cell Design Architecture  
Figure 1a shows the front view of the proposed unit cell structure. It consists of several pairs of symmetric C-shaped split-ring resonators that are assembled and cover each other to enable the unit cell operation over the wideband range. The unit cell was designed on an FR4 substrate with 4.6 substrate dielectric constant, and a thickness of 1.6 mm. Here, two simulation set-ups were applied to verify the unit cell working principle. Firstly, the structure was located between two-wave guide ports in the x-direction as shown in Figure 1b, then in the y-direction as illustrated in Figure 1c. This was simulated using a finite-difference time-domain solver based on computer simulation technology (CST).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Reference** & **Size (mm\({}^{2}\))** &
\begin{tabular}{c} **Operating Bands** \\ **(GHz)** \\ \end{tabular} & **Technique** & **Max. BW (\%)** & **Max. Gain(dBi)** \\ \hline
[33] & \(30.0\times 40.0\) &
\begin{tabular}{c} (2.400–2.700), \\ (3.320–4.000), \\ (4.760–5.800) \\ \end{tabular} & CPW-Fed \& Slots & 19.70 & – \\ \hline
[34] & \(18.0\times 30.0\) &
\begin{tabular}{c} (1.765–2.695), \\ (3.010–3.910), \\ (5.110–6.055) \\ \end{tabular} & CPW-Fed & 16.90 & 4.75 \\ \hline
[35] & \(50.0\times 35.0\) &
\begin{tabular}{c} (1.680–2.040), \\ (3.030–4.100), \\ (4.760–6.840), \\ (7.620–8.420) \\ \end{tabular} & I-shaped strips & 35.80 & -3.50 \\ \hline
[36] & \(50.0\times 69.0\) &
\begin{tabular}{c} (1.430–1.600), \\ (1.940–2.100), \\ (2.400–2.570), \\ (3.450–3.600) \\ \end{tabular} & L-shaped stub & 06.80 & 1.38 \\ \hline
[37] & \(85.0\times 125\) &
\begin{tabular}{c} (0.870–1.010), \\ (1.720–1.960), \\ (2.280–2.830), \\ (5.710–6.380) \\ \end{tabular} & L-shaped radiator & 11.10 & 5.82 \\ \hline
[38] & \(40.0\times 20.0\) &
\begin{tabular}{c} (1.540–1.610), \\ (2.310–2.720), \\ (3.100–3.750), \\ (5.030–5.950) \\ \end{tabular} & Asymmetric coplanar strip & 16.70 & 3.50 \\ \hline
[25] & \(24.8\times 30.0\) &
\begin{tabular}{c} (2.350–2.450), \\ (2.630–2.760), \\ (5.420–5.770), \\ (8.680–8.890) \\ \end{tabular} & Metamaterial & 10.25 & 3.01 \\ \hline
[26] & \(32.0\times 38.0\) &
\begin{tabular}{c} (2.400–2.600), \\ (2.900–3.100), \\ (3.300–3.500), \\ (4.000–8.300) \\ \end{tabular} & Metamaterial & 11.11 & 3.80 \\ \hline
[27] & \(48.0\times 48.0\) &
\begin{tabular}{c} (1.710–1.880), \\ (1.880–2.200), \\ (3.400–3.800) \\ \end{tabular} & Metamaterial & 13.00 & 4.72 \\ \hline
[28] & \(125\times 125\) & \begin{tabular}{c} (1.380–1.395), \\ (1.570–1.580) \\ \end{tabular} & Artificial magnetic conductor (AMC) & 02.00 & 7.00 \\ \hline This work & \(78.6\times 42.5\) & \
\begin{tabular}{c} (0.865–1.060), \\ (2.240–2.520), \\ (3.250–4.310), \\ (4.900–6.500) \\ \end{tabular} &
\begin{tabular}{c} NZRI \& DNG \\ Metamaterial \\ \end{tabular} & 28.00 & 6.72 \\ \hline \hline \end{tabular}
\end{table}
Table 1: _Cont._The simulation of metamaterial was executed for the frequency range of 2-20 GHz. The negative electric permittivity and permeability are usually used as the material parameters that describe how materials polarize in the presence of electric and magnetic fields, which leads to achieving a negative refractive index.