## 4 Experimental Result
### The VNA Graphics of Tests Performed on 3W Ground Plane Transmission Line  
This section presents the measurement results obtained from a transmission line model with a ground plane width three times the width of the signal line (3W). The experiments primarily focused on analyzing near-end crosstalk (S\({}_{\rm 31}\)). The effects of capacitors placed at different positions along the 100 mm transmission line are depicted in Figure 6. Specifically, Figure 6a illustrates the results when the capacitor is located at the starting point, Figure 6b corresponds to the midpoint placement, and Figure 6c represents the endpoint configuration.  
As illustrated in Figure 2, the placement of capacitors at different positions along the transmission line directly influences the return current path, thereby affecting crosstalk mitigation. When the capacitor is placed at the beginning of the transmission segment in Figure 6a, it primarily influences the initial propagation of the return current and modifies the early-stage coupling behavior. The middle placement Figure 6b distributes the capacitive effect along the transmission length, promoting a more uniform reduction in crosstalk. In contrast, placing the capacitor at the end of Figure 6c mainly affects the termination region, where secondary coupling effects and reflections can be more significant. These placements allow for a comparative evaluation of how capacitor positioning influences crosstalk suppression along different sections of the transmission line.  
Figure 6: The NEXT obtained when capacitors with values of 1 pF, 15 pF, and 82 pF are placed in length of 100 mm and a ground width of 3W: (**a**) at the beginning of the transmission line; (**b**) in the middle of the transmission line, and (**c**) at the end of the transmission line.  
In Figure 6, the effects of capacitors placed at different positions along the 100 mm transmission line are illustrated. The observed impact varies based on the frequency and capacitance values. For instance, when an 82 pF capacitor was placed at the beginning of the transmission line, a crosstalk reduction of approximately 20-25 dB was achieved within the 1.6-2.7 GHz frequency range. When capacitors were added at the midpoint of the transmission line, all tested values showed improvements starting from 1.9 GHz. Notably, when an 82 pF capacitor was placed at the endpoint of the transmission line, an improvement of approximately 22 dB was observed. Furthermore, in the frequency range of 2.5-2.85 GHz, the 1 pF capacitor exhibited superior performance compared to the other tested capacitance values.  
The effects of capacitors on the 200 mm transmission line are shown in Figure 7, with Figure 7a representing the beginning, Figure 7b the midpoint, and Figure 7c the endpoint placements.  
As shown in Figure 7, the placement of capacitors on the 200 mm transmission line significantly impacts crosstalk reduction, depending on the frequency and capacitance values. When a 1 pF capacitor is placed at the beginning of the line, an improvement of 25 dB is observed around 1.1 GHz, while an 82 pF capacitor achieves the same level of improvement near 3 GHz. For capacitors placed at the midpoint of the line, all values exhibit positive effects between 2.9 GHz and 3.1 GHz, with 1  
Figure 7: The NEXT obtained when capacitors with values of 1 pF, 15 pF, and 82 pF are placed in length of 200 mm and a ground width of 3W: (**a**) at the beginning of the transmission line, (**b**) in the middle of the transmission line, and (**c**) at the end of the transmission line.  
showing particularly strong performance. At the endpoint, adding a 15 pF capacitor results in a 30 dB improvement around 3 GHz.