# Miniaturized Antenna Array-Based Novel Metamaterial Technology for Reconfigurable MIMO Systems
## 3 MTM Analysis and Discussion
### Design Methodology  
#### 3.1.1 Monopole Antenna Performance  
In this section, the proposed monopole element performance in terms S\({}_{11}\) spectra are investigated with respect to varying the separation distance between the monopole and the ground plane (Xg). Therefore, the considered distance Xg was changed from 1 to 5 mm with a step of 1 mm with respect to monitoring S\({}_{11}\) spectra as shown in Figure 3. It was observed from the obtained results that the antenna provides two frequency bands around 1.9 and 4.5 GHz. Nevertheless, it is seen that the proposed antenna matching impedance is insignificantly changed with changing Xg at the first band; however, at the second band, the matching impedance is improved pointedly at Xg = 3 mm; then, it returns back to being degraded due to increasing the distance. Additionally, it was observed that the frequency resonance location is not changed due to the fact of keeping the monopole length fixed to a certain length that has no effect on the current motion [12]. Moreover, it was observed that the generated frequency resonances are relative to the multiple constants of the halves of the wavelengths, which depends on the antenna's electrical lengths' harmonics [13]. Consequently, the length of the proposed monopole was found to be relative to the physical length after the proposed CPW feeding structure. Such an observation reveals that the capacitive effects between the antenna ground plane and the monopole structure could accumulate the electrical charges significantly to increase the antenna input impedance over the microwave source [15]. For this, the authors considered Xg = 2 + 1 mm to be the best choice for the next design step; this is because the matching was found to be around \(-\)35 dB at 4.35 GHz.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Element** & **Value** \\ Resistance of the left hand (RLH) & 12.2 \(\Omega\) \\ Resistance of the right hand (RRH) & 50 \(\Omega\) \\ Conductance of the left hand (GLH) & 0.11 S \\ Conductance of the right hand (GRH) & 4.55 S \\ Capacitance of the left hand (CLH) & 1.17 pF \\ Capacitance of the right hand (CRH) & 3.11 pF \\ Inductance of the left hand (LLH) & 3.24 nH \\ Inductance of the right hand (LRH) & 2.34 nH \\ \hline \hline \end{tabular}
\end{table}
Table 2: Equivalent circuit model lumped elements.  
Figure 3: The obtained S\({}_{11}\) spectra variation for the proposed antenna with changing Xg.  
Now, to investigate the effects of increasing the ground plane length on the antenna frequency resonance, the authors considered \(\mathrm{Xg}=3\) mm, but the ground plane length was changed from 8 to 5 mm with a step of 1 mm. It was observed that with decreasing the ground plane length, there was a significant decay in the antenna second mode frequency resonance. Therefore, it is concluded the ground plane length (Yg) is better to be 5 mm for our applications. Reducing the length to less than 5 mm is not very desired during the fabrication process due to soldering limitations [4]. The calculated results are shown in Figure 4 in terms of \(\mathrm{S}_{11}\) spectra with respect to varying the ground plane length (Yg).  
For further analysis, the authors studied the effects of varying the monopole width on the antenna \(\mathrm{S}_{11}\) spectra. Therefore, the monopole width (Xm) was changed from 1 to 5 mm. It was found that the observable variation in the term of \(\mathrm{S}_{11}\) spectra is specific to bandwidth, matching, and frequency resonance, as depicted in Figure 5. This is attributed to the fact that current motion is usually on the antenna length that follows the dimension with a larger conduction area [12]. For this, such phenomena are well known from different previous publications that discussed the effects of current motion on antennas' maximum dimension [12].  
Figure 4: The obtained \(\mathrm{S}_{11}\) spectra variation for the proposed antenna with changing Yg.  
Figure 5: The obtained \(\mathrm{S}_{11}\) spectra variation for the proposed antenna with changing Xm.