## 4 Simulation Results and Analysis  
### Return Loss  
The simulated S11 results in Figure 4 illustrate a deep resonance at 28.3 GHz with a return loss of approximately \(-\)23 dB, indicating excellent impedance matching. The measured S11 results exhibits a resonance at around 28.1 GHz with a return loss of approximately \(-\)21.5 dB. The 3 dB bandwidth is slightly broader in the simulation, while the measured response shows a slightly shifted resonance and a narrower impedance bandwidth. The measured and simulated S11 results shown in Figure 5 exhibit good agreement, validating the design's accuracy despite minor fabrication and assembly tolerance. A return loss better than \(-\)10 dB across the desired band confirms that the antenna is well-matched at 28 GHz, making it suitable for mm-wave 5G and radar applications. Small discrepancies between the curves are expected due to connector and solder joint parasitic, dielectric constant deviation in the substrate, as well as SMA-to-2.4 mm transition errors. Similar performance trends are reported in [15], where fabricated results exhibit a \(\pm\)200 MHz shift due to PCB etching and material tolerances. Figure 6 presents the simulated and measured S11 results of the proposed 1 \(\times\) 6 linear antenna array integrated with a two-way microstrip power divider. The simulated resonance occurs at 28.1 GHz with a minimum return loss of \(-\)23.5 dB, while the measured resonance is observed at 28.3 GHz with a minimum return loss of \(-\)20.7 dB. The frequency shift of approximately 200 MHz (0.7% of the center frequency) reflects good agreement and confirms the accuracy of the design and fabrication process. Both results maintain a return loss below \begin{table}
\begin{tabular}{c c c} \hline
**Linear Array Elements** & **Parameters** & **Dimensions (mm)** \\ \hline \multirow{4}{*}{**Substrate**} & Length (L) & 27 \\  & Width (W) & 6.5 \\  & Thickness (T) & 1.574 \\  & Permititivity (\(\varepsilon\)) & 3 (F/m) \\  & Length (L\({}_{\text{f}}\)) & 3 \\
**Feedline** & Width (W\({}_{\text{f}}\)) & 0.3 \\  & Length (L\({}_{\text{g}}\)) & 27 \\
**Ground** & Width (W\({}_{\text{g}}\)) & 6.5 \\  & Length (L\({}_{\text{p}}\)) & 2 \\
**Patch** & Width (W\({}_{\text{p}}\)) & 4 \\ \hline \end{tabular}
\end{table} 
Table 2: Dimension of the 1 \(\times\) 6 linear antenna array. Figure 3: Layout design of the symmetric two-way microstrip power divider. \(-10\) dB across the \(\sim\)27.3 to \(\sim\)29.6 GHz range, indicating a wide impedance bandwidth of approximately 23 GHz (-8.2%), which is suitable for 5G mm-wave bands such as n257 and n258. Figure 4: The magnitude of the return loss S11 for various antenna evaluation design steps. Figure 5: Simulated return loss of proposed 1 \(\times\) 6 array. Figure 6: Simulated and measured return loss of proposed 1 \(\times\) 6 array integrated with power divider. Figure 5 shows the simulated and measured S\({}_{11}\) of the standalone 1 \(\times\) 6 linear array (without the power divider). The resonance in this case is centered around 28.0 GHz, with both simulation and measurement showing minimum return losses of approximately \(-\)13.2 dB and \(-\)12.6 dB, respectively [16]. These results confirm that the integration of the power divider enhances impedance matching and deepens the return loss, resulting in more efficient energy transfer to the radiating elements. The observed discrepancies between simulation and measurement, both in frequency shift and return loss magnitude, can be attributed to several common mm-wave fabrication factors, including connector parasitic and SMA-to-2.4 mm transitions, soldering irregularities at the feed point, etching variations affecting line dimensions, and dielectric constant deviations in the Rogers RO3003 substrate [17]. To improve agreement in future iterations, it is proposed to use precision launch connectors, employing laser-based or photolithographic etching and performing careful pre-measurement calibration using standard gain horns or known reference antennas [18].