## 4 Experimental Result  
The results obtained in this study evaluate the effectiveness of various methods for mitigating crosstalk effects in CPW lines. The measurements clearly demonstrate the presence of crosstalk between CPW lines, particularly at high frequencies. The addition of capacitors to the ground (GND) planes was found to significantly reduce crosstalk at specific frequencies. These capacitors provide an alternative path for return currents, thereby stabilizing the electromagnetic environment and reducing mutual coupling between transmission lines. As mentioned in the Section 3, the capacitors used in this study belong to the S603 DS series and have an SRF of approximately 20 GHz. This frequency range ensures their effectiveness in mitigating crosstalk in high-speed applications. By providing effective performance up to 20 GHz, these capacitors are well suited for practical high-frequency designs, as verified in this study. The selected capacitor values of 1 pF, 15 pF, and 82 pF were chosen for their availability and practicality in real-world applications. Additionally, the spacing between transmission lines was shown to have a substantial impact on crosstalk levels. The measurements indicate that crosstalk increases at shorter distances due to stronger electromagnetic coupling, whereas greater spacing reduces this effect. These findings underscore the importance of optimizing line spacing during the design phase to control crosstalk in electronic circuits. Tables 1 and 2 summarize the improvements in S31 achieved by adding capacitors to the GND planes for two different UCPW line designs fabricated using FR4 dielectric material. The selection of 3W and 5W as ground plane widths is based on design guidelines provided by semiconductor manufacturers and industry standards for high-speed PCB design. 'W' represents the transmission line width, meaning that 3W and 5W correspond to ground planes that are three and five times the width of the signal line, respectively. While 1W spacing was theoretically an option, it was excluded due to its limited effectiveness in practical applications. Manufacturer guidelines and industry best practices recommend 3W and 5W configurations, as they provide an optimal balance between manufacturability, crosstalk reduction, and signal integrity. Furthermore, validation tests and performance benchmarks are typically conducted based on these ratios, reinforcing their relevance in real-world designs. Analysis of the data in Tables 1 and 2 reveals that capacitors added to the reference planes between the transmission lines significantly reduce crosstalk as the length of the transmission lines increases. The observed improvements also depend on the width of \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Length (mm)** & **Value (pF)** & **Location** & **Frequency (GHz)** & **Improvement (\(-\)dB)** \\ \hline
100 & 82 & First & 2.7 & 25 \\
200 & 15 & First & 2.9 & 35 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Optimum near-end crosstalk improvements with capacitors added between 3W wide ground planes. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Length (mm)** & **Value (pF)** & **Location** & **Frequency (GHz)** & **Improvement (\(-\)dB)** \\ \hline
100 & 15 & End & 2.1 & 25 \\
200 & 82 & End & 1.5 & 40 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Optimum near-end crosstalk improvements with capacitors added between 5W wide ground planes. the ground plane, with reductions noted for both 3W and 5W configurations. These findings confirm the critical role of capacitor placement and reference plane dimensions in control-ling crosstalk. The frequency values presented in the tables correspond to the points where the highest crosstalk reduction was observed for each configuration. Rather than evaluating arbitrary frequency points, the selection was based on the frequency ranges where capacitive coupling effects provided the most effective mitigation.