## 3 Result Analysis and Discussion  
Each design was numerically analyzed using the full-wave higher-frequency structural simulator (HFSS). A variety of performance metrics such as return loss, radiation pattern, total gain plot, field distribution, gain for the different frequencies, directivity, TARC, and directivity gain were analyzed. The reflection and transmittance response must be analyzed for the high-frequency antenna structure [26]. The initial analysis was carried out for the one-element MIMO antenna to check the performance observation. The analysis in terms of reflection coefficients for the one-element MIMO structure is represented in Figure 3. There are two bands with less than \(-10\) dB of reflection coefficients observed. The first band is shown at 4.5 GHz with an S\({}_{11}\) of \(-18\) dB and the second band is shown at 8 GHz with an S\({}_{11}\) of \(-21\) dB. The MIMO structure's unusual form primarily aids in attaining higher isolation (\(<\)\(-28\) dB) during measurement as per DS-1. Two bands of reflection response are observed in Figure 4. The first band represents reflection coefficients of \(-27.098\) dB at 2.3 GHz, and the S\({}_{11}\) is less than \(-10\) dB in the range of 1 to 2.485 GHz. The second band provides the S\({}_{1  
this band is observed in the range of 13.655 GHz to 14 GHz. Therefore, in this mode, a maximum bandwidth of 2.54 GHz is achieved. Figure 4: Reflection and transmission coefficients of the proposed four structures. (**a**) DS-1 provides the two frequency band responses, The design provides peak isolation of \(-27.098\) dB and maximum bandwidth of 2.485 dB. (**b**) DS-2 provides the five band responses with peak isolation of \(-31.457\) dB and maximum bandwidth of 1.045 dB. (**c**) DS-3 provides the nine band responses with peak isolation of \(-39.44\) dB and maximum bandwidth of 2.54 dB. (**d**) DS-4 provides the five band responses with peak isolation of \(-20.308\) dB and maximum bandwidth of 2.35 dB. The maximum bandwidth of 2.485 GHz was attained for the DS-1 configuration. There were a maximum of nine bands of reflection response attained for the DS-3 configurations, and the maximum isolation was attained for the DS-3 design. The comparison of the measured and simulated reflection plots is presented in Figure 5. The measured results authenticate the performance results of both structures. The rationale of the proposed design was analyzed based on the modification of the patch and defective ground region. DS-4 shows the five bands of reflection coefficients with less than \(-10\) dB value. For example, the first band represents an S\({}_{11}\) of \(-14.420\) dB at 3.1 GHz; this band is observed in the range of 3.065 GHz to 3.215 GHz. The second band represents an S\({}_{11}\) of \(-20.308\) dB at 3.55 GHz; this is observed in the range of 3.485 GHz to 5.655 GHz. The third band represents an S\({}_{11}\) of \(-16.715\) dB at 7.6 GHz; this band is observed in the range of 7.2 GHz to 7.97 GHz. The fourth band represents reflection coefficients of \(-19.805\) dB at 11.8 GHz; this band is observed in the range of 9.45 GHz to 11.8 GHz. The fifth band represents reflection coefficients of \(-13.914\) dB at 12.57 GHz; this band is observed in the range of 12.55 GHz to 12.585 GHz. In this mode, a maximum bandwidth of 2.35 GHz is achieved. Table 3 gives an idea about how each modification affects the performance of structure in terms of reflection coefficient, bandwidth, and isolation. Table 3 shows that adding slots in the ground region enhances the reflection coefficients. Therefore, the engraved patch area with surrounded slots and ground region provides the maximum bandwidth of 2.485 GHz. The radiation pattern for the simulation and measurement of the proposed antenna structure is represented in Figure 6. The healthy similarity that is observed in both of the results confirms the effectiveness of the structure. The maximum broadside radiation pattern is observed in DS-3. The addition of slots in the patch and ground region affects the radiation pattern.