## 3 Result Analysis and Discussion
The E-Plane radiation pattern of all of the modes is observed for \(\phi\) = 0\({}^{\circ}\). Practically, antenna gain is measured in the anechoic chamber by keeping the horn antenna [27; 28]. The three-dimensional total gain plot of the proposed MIMO structures is presented in Figure 7. The total gains of DS-1, DS-2, DS-3, and DS-4 are 3.63 dB, 4.82 dB, 3.36 dB, and 5.23 dB, respectively. Maximum gain occurs in D.S.-4 design. The gain over the 1 to 14 GHz span is presented in Figure 8. The DS-1 configuration provides an average gain of 1.108 dB attained with a peak gain of 20.44 dB at 2.59 GHz. The DS-2 configuration provides an average gain of 1.42 dB attained with 12.79 dB at 2.415 GHz. The DS-3 configuration provides an average gain of 3.281 dB attained with the peak gain of 24.77 dB at 12.02 GHz. Finally, the DS-4 configuration provides an average gain of 1.16 dB attained with a peak gain of 26.127 dB at 12.575 GHz. The E-field distributions through the patch region for the proposed four designs are shown in Figure 9. The E-fields of DS-1, DS-2, DS-3, and DS-4s are 22.3 V/cm, 18.5 V/cm, 33.3 V/cm, and 14.2 V/cm, respectively. However, due to the opposite field distribution in the slits near the hexagonal-shaped patch area, the effective value of the electric field is reduced [29]. The directivity and \(-3\) dB down directivity plots of the proposed four structures are shown in Figure 10. The co-polar directivity plot is represented over the \(-180\) degrees to \(+180\) degrees range [30]. The peak value of directivity for DS-1 is 3.12 dB. The DS-2 provides a high gain of 5.16 dB. DS-3 provides less directivity than DS-2. DS-3 provides a directivity of 3.48 dB, and DS-4 provides directivity of 2.78 dB. Normalized directivity is calculated at \(-3\) dB down to the peak directivity. The two bands of normalized directivity for DS-1 are \(90^{\circ}\) and \(50^{\circ}\). The normalized directivity for DS-2 is \(60^{\circ}\). Three bands of normalized directivity attained for the DS-3 configuration are \(40^{\circ}\), \(38^{\circ}\), and \(30^{\circ}\). Similarly, three bands of \(20^{\circ}\), \(70^{\circ}\), and \(35^{\circ}\) are attained for the DS-4 configuration. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Design** & **No of S\({}_{11}\) Bands** & **Maximum** & **Maximum** & **Peak Gain** \\
**Structure** & **(\(<\)\(-10\) dB)** & **Isolation (dB)** & **Bandwidth (GHz)** & **(dB)** \\ \hline D.S.-1 & Two & \(-27.098\) & 2.485 & 20.44 \\ DS-2 & Five & \(-31.457\) & 1.045 & 12.79 \\ DS-3 & Nine & \(-39.44\) & 2.54 & 24.77 \\ DS-4 & Five & \(-20.308\) & 2.35 & 26.127 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Performance comparison among different design structures. The value of ECC should be zero. The isolation between the individual antenna nodes improves as the ECC increases. Using the scattering parameter, the ECC can be calculated as per Equation (5). The simulated result represents the ECC response of the proposed DS:1, DS:2, DS:3, and DS:4, as represented in Figure 11. DS:1 showed a peak ECC value of 0.2 dB at 2.5 GHz, DS:2 showed a peak ECC value of 0.15 dB at 2.3 GHz, and DS:3 and DS:4. Figure 5: The comparison among measured and simulated results. (**a**) DS-1. (**b**) DS-2. (**c**) DS-3. (**d**) DS-4. DS:4 almost showed values of zero for the ECC for the entire spectrum. The measured responses of the ECC for all of the proposed designs, DS:1, DS:2, DS:3, and DS:4, are within an acceptable range or are near to zero over the 1 GHz to 14 GHz range. \[\text{ECC}=\frac{\left|\text{S}_{11}^{*}\text{S}_{12}+\text{S}_{21}^{*}\text{S} _{22}\right|^{2}}{\left(1-\left(\left|\text{S}_{11}\right|^{2}+\left|\text{S}_ {21}\right|^{2}\right)\right)\left(1-\left(\left|\text{S}_{22}\right|^{2}+ \left|\text{S}_{12}\right|^{2}\right)\right)} \tag{5}\]  
The improvement in the SNR of a multiple element system over a one element system is referred to as diversity gain (DG). The DG is calculated using the following Equation (6).