## 2 Proposed Antenna Design
### Evolution of Satellite Network Notch
In a MIMO system, low correlation between antennas is desirable, and therefore the ECC (envelope correlation coefficient) value should be close to or at its minimal value, which is zero. In the case of the MIMO antenna system under investigation, it is crucial for the ECC to remain below a certain threshold throughout the entire operating frequency range. Specifically, the ECC should  
Figure 8: Surface current distribution at (a) 5.5 GHz, (b) 8.8 GHz. Figure 7: The simulated and measured results of radiation patterns at different frequencies: (**a**) C-band notch frequency 4.45 GHz, (**b**) WLAN notch frequency 5.5 GHz, (**c**) in-band frequency 6.25 GHz, (**d**) satellite notch 8.5 GHz. be less than or equal to 0.5 to ensure satisfactory performance and can be calculated using Equation (2). Figure 5.0  
Figure 10 illustrates the ECC (envelope correlation coefficient) values, indicating the level of correlation between the antenna and the other antennas in the system. It is observed that the ECC remains consistently below 0.5 across the entire frequency spectrum, demonstrating low correlation between the antennas. In terms of diversity, the Diversity Gain (DG) should be equal to or greater than 10 (DG \(\geq\) 10). The Diversity Gain represents the strength of the transmitted signal by the MIMO antenna system, while also indicating the reliability of the communication channel. The computation of Diversity Gain can be performed using the provided Equation (3). Figure 5.1  
The equation establishes a relationship between the Diversity Gain (DG) and envelope correlation coefficient (ECC). When there is a higher degree of correlation among the antennas, the signal power generated by the MIMO system diminishes, leading to reduced reliability of the communication link. As depicted in Figure, the correlation between the antennas is relatively weak, and the design yields the strongest signal. The ECC value is low, while the DG value approaches 10 dB across the entire frequency range. Mean Effective Gain (MEG) represents the power received by an antenna. To ensure good diversity performance, the MEG threshold should be below MEG < 3 dB. Due to the MIMO antenna system's excellent isolation, a low MEG value can be achieved. The provided Equation (4) can be utilized to calculate the MEG. Figure 5.2  
Figure 10 demonstrates that the Mean Effective Gain (MEG) performance of the MIMO antenna remains below 3 dB throughout the entire frequency band, indicating that it does not significantly affect other antenna elements. Channel capacity loss (CCL) quantifies the amount of information lost in a MIMO antenna system. Mutual coupling between the antenna elements is the primary cause of communication loss in a MIMO setup. This mutual coupling degrades the performance of the communication system and results in losses, thereby reducing the system's reliability. The channel capacity loss, represented by  
Figure 5.3 Simulated and measured transmission coefficient of MIMO system. CCL, should be less than 0.4 bits per second per hertz. By analyzing the S-parameters of the MIMO antennas, the CCL can be derived using Equation (5). Figure 10 demonstrates that the MIMO antenna system exhibits minimal mutual coupling, resulting in low channel capacity loss (CCL) throughout the entire frequency range. The low mutual coupling indicates that the communication loss in the MIMO setup is minimized, leading to enhanced system reliability. The CCL values, as depicted in Figure 10, affirm the efficient performance of the MIMO antenna system with respect to channel capacity across various frequencies. Figure 5.4  
where  
\(A=1-|S_{ii}|^{2}+|S_{ij}|^{2}\)  
\(B=1-|S_{jj}|^{2}+|S_{ji}|^{2}\)