Application91 Crosstalk analysis between two sets of differential lines with vias

When the distance between the differential lines is varied,
The effect on crosstalk noise between two sets of differential signals was investigated.
It is a standard function of Femtet with the interval between the differential lines as variable name dx.
It is calculated by waving dx = 0.35, 1.0 by parametric analysis.

Two sets of differential line analysis models with differential vias are shown in Figure 1.
The differential line analysis model is based on electromagnetic wave analysis example 22.
Figure 2 shows an image of shaking the variable dx in parametric analysis.
The far-end crosstalk frequency characteristics (Sd4d1) of the differential signal are shown in Figure 3.
The near-end crosstalk frequency characteristics (Sd3d1) of the differential signal are shown in Figure 4.
From the results in Figures 3 and 4, we can see how the smaller the differential track spacing, the larger the crosstalk.

Figure 5 shows the TDR waveform.
Because the shape of the differential track itself (Via diameter, track width, etc.) was not changed in this case,
There is no difference between the two.