## 2 Proposed Antenna Design
### Evolution of Satellite Network Notch  
Satellite networks often face disruptions in communication rates due to the significant amount of data being transferred among users. By placing a C-shaped (curve-shaped) element in the patch's center, a notching band can be created for the satellite network. The notch at the satellite network was introduced by the C-shaped curve, which also reduced interference. For the satellite network, the notch frequency was introduced at an estimated arc length of 2.8 mm as shown in Figure 4.  
The notching characteristics at the C, WLAN, and satellite networks are shown in Figure 5.  
The simulated and measured results are in good agreement. The simulated gain can go from \(-8\) to 5 dB. Gain improves at in-band frequencies and degrades in notch-frequency ranges. As a result, we may say that the in-band frequency has high gain and low signal suppression, while the notched band has low gain and strong signal suppression. The gain of the antenna is represented in Figure 6. The efficiency of the specific C notch band, WLAN band, and satellite band is 48%, 52%, and 51% respectively. The efficiency is degraded in the notching band because of mismatching characteristics. Figure 4: The simulated result of WLAN band rejection. Figure 3: The simulated result of WLAN band rejection. Figure 7 displays the radiation pattern's co and cross configuration at the in-band frequency as well as the notch band. The radiation patterns at 4.5 GHz, 5.5 GHz, 8.3 GHz (notch band frequencies), and 6 GHz (in-band frequency) are shown, along with the corresponding modeled and measured radiation patterns. The results demonstrate that the proposed antenna can operate in both omnidirectional and dipole configurations. The resonant behavior of the system can be elucidated by examining the surface current distribution on the top and bottom metallic layers, as illustrated in Figure 8. According to [PERSON]'s law, a time-varying magnetic field confined between two metals induces surface currents on these layers in opposing directions. As depicted in Figure 8a,b, at the resonant frequencies of 5.5 GHz and 8.8 GHz, a remarkable observation emerges: the net currents on the top and bottom layers (referred to as the ground plane) flow in diametrically opposed directions. This distinctive characteristic of oppositely directed currents on the top and bottom layers results in the attainment of a pronounced magnetic resonance at 5.5 GHz and 8.8 GHz, as evidenced in the figures. The black arrow in the diagram signifies the distribution of current on the top patch, whereas the red arrow corresponds to the current distribution on the bottom metallic layer. Furthermore, the current distribution pattern discernible in the antenna's resonant mode bears resemblance to that of a dipole. Such behavior grants the antenna the ability to maintain stable radiation patterns across a wide frequency band, which proves to be an advantageous trait in practical applications. Figure 5: The simulated and measured result of the reflection coefficient at the C, WLAN, and satellite bands. Figure 6: The simulated and measured result of the gain. The provided monopole, crescent-shaped, 4 \(\times\) 4 MIMO antenna exhibits a circular configuration in Figure 1, which is advantageous for achieving pattern and polarization diversity. Antennas 1 and 2 contribute to polarization diversity, while antennas 1 and 3 enable pattern diversity. To assess the effectiveness of the monopole UWB-MIMO antenna, various critical parameters are examined. Figure 9 presents the transmission coefficient of the UWB-MIMO antenna, indicating a \(-25\) dB transmission coefficient among the ports, which does not degrade the characteristics of the MIMO system. The high isolation in the MIMO system is achieved through the mutual coupling of CSRR. The inter-antenna correlation is evaluated using the envelope correlation coefficient (ECC) of the UWB MIMO antenna's diversity parameter.