## 2 Dual-Port MIMO Antenna  
### Geometry and Design Evolution  
This section presents the comprehensive geometry and design progression of the presented dual-port MIMO variant. Figure 1 displays the top view and Figure 1 displays the ground view with dimensions 41 \(\times\) 30 \(\times\) 1.6 mm\({}^{3}\). Table 1 provides a detailed breakdown of the antenna's dimensions. This finalized antenna design was achieved through a four-stage development process with parametric analysis. The sequential evolution of the antenna across these four stages is illustrated in Figure 2a-d. The antenna elements are excited by 50 \(\Omega\) microstrip lines. Stage 1 involves the creation of a basic rectangular radiating element accompanied by a slightly modified ground which is illustrated in Figure 2a. Computed impedance profile is illustrated in Figure 3, revealing that the 10 dB bandwidth achieved fails to encompass the full UWB range spanning 3.1 GHz to 10.6 GHz. At this stage, the electric field is mainly confined near the feed point and the central area of the radiating patch with minimal spreading of surface currents resulting in narrow bandwidth. In Stage 2, a U-shaped slot oriented up-side down and a linear I-shaped slot are embedded into the ground, as illustrated in Figure 2b. This variation leads to a notable improvement in the impedance bandwidth, as evidenced in the simulation results displayed in Figure 3. The current flow on \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Parameters**} & **Measurement** & \multirow{2}{*}{**Parameters**} & **Measurement** & \multirow{2}{*}{**Parameters**} & **Measurement** \\  & **(mm)** & & & **(mm)** & **(mm)** \\ \hline L & 30 & L10 & 17 & W5 & 1 \\ L1 & 7.5 & L11 & 19 & W6 & 3 \\ L2 & 3.5 & L12 & 5 & W7 & 5 \\ L3 & 1 & L13 & 11 & W8 & 1.5 \\ L4 & 3 & L14 & 0.5 & W9 & 1 \\ L5 & 0.5 & W & 41 & W10 & 4 \\ L6 & 12 & W1 & 12 & W11 & 12 \\ L7 & 2 & W2 & 1 & W12 & 1 \\ L8 & 2 & W3 & 0.5 & W13 & 2 \\ L9 & 7 & W4 & 2.5 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Proposed 2-port antenna dimension details. Figure 1: Dual-port geometry (**a**) top layout (**b**) ground layout. the ground plane was disturbed by the introduction of slots, creating new resonance paths, enabling a broader distribution of the electric field, and helping to enhance the antenna's bandwidth. However, the desired full UWB range is still not achieved. In Stage 3, two small rectangular notches resembling staircase-like cuts are added to the bottom corners of the radiating patch along with a slot of C-shape which is carved into the antenna's ground. The updated impedance characteristics are shown in Figure 3 indicating further enhancement in bandwidth. These alterations improve impedance matching by altering current paths and enabling more efficient E-field radiation near the patch edges and the ground slot, though the complete UWB range remains uncovered. Finally in Stage 4, two additional rectangular slots are introduced at the center of the antenna elements, one oriented vertically and the other horizontally so that they intersect to form a cross-shaped slot. This structure significantly alters the electric-field distribution by enabling stronger coupling between modes and introducing multi-resonant behavior and helps to flatten the reflection coefficient curve and extend the bandwidth. Using the stage 4 structure, a parametric study was conducted by altering the length W1 varied between 10 mm and 14 mm with 1 mm intervals to examine its effect on impedance matching and resonant frequencies. The comparative results for the different values of W1 are illustrated in  
Figure 3: Simulated S11 vs. frequency for four-stage antenna evolution. Figure 2: (**a–d**) Stage-wise advancement in the proposed antenna configuration. Figure 4. The analysis reveals that adjusting the W1 length leads to a noticeable increase in bandwidth and a reduction in reflection. Notably, when W1 = 12 mm, the design achieves the widest bandwidth along with the lowest reflection coefficient.