Far-End Crosstalk Modeling and Prediction for Stripline With Inhomogeneous Dielectric Layers (IDLs)

Far-end crosstalk (FEXT) is a critical factor that limits signal integrity performance in high-speed systems. The FEXT level is sensitive to the dielectric inhomogeneity of the stripline in fabricated printed circuit boards (PCBs). The dielectric of the stripline is manufactured with multiple inhomogeneous dielectric layers (IDLs) of various resin and glass fiber bundles. A marginal difference in the dielectric permittivity of the IDLs can lead to a significant change FEXT level. In this article, a practical FEXT modeling methodology for striplines is proposed by introducing the extraction method for ${{\boldsymbol{\varepsilon }}}_{\boldsymbol{r}}$ of IDLs. The new stripline model is constructed with three IDLs comprised of core, prepreg, and resin pocket, to improve the model accuracy. With the cross-sectional geometry and measured S-parameters of the coupled striplines, ${{\boldsymbol{\varepsilon }}}_{\boldsymbol{r}}$ of IDLs can be extracted. In addition, an analytical model to predict the FEXT polarity and magnitude of the stripline caused by the inhomogeneity is proposed targeted for prelayout application. The proposed models have been verified using measurement. The proposed models can provide useful analysis methodology and design guidelines to mitigate the FEXT level in high-speed systems, especially for high-volume PCB tests in the prelayout and postlayout stages.