Far-End Crosstalk Analysis for Stripline with Inhomogeneous Dielectric Layers (IDL)

Abstract

Far-end crosstalk (FEXT) noise is a critical factor that affects signal integrity performance in high-speed systems. The FEXT level is sensitive to the dielectric inhomogeneity of the stripline in fabricated printed circuit boards (PCB). Stripline is typically modeled as a 2-layer model with core and prepreg layers. However, in reality, the stripline is laminated by multiple inhomogeneous dielectric layers (IDL). The dielectric layers of the stripline are laminated with epoxy resin and glass bundles. The dielectric permittivity (ε <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</inf> ) of the epoxy resin and glass bundles are different, which causes the inhomogeneity of the dielectric layers while also increasing the FEXT magnitude. Therefore, a typical 2-layer structure is inaccurate to model the FEXT. In this paper, the stripline model is constructed with the core, prepreg, and resin pocket layers. To analyze the stripline with three IDL, a practical superposition method is proposed. A design guideline to mitigate the FEXT level in the stripline design is proposed based on the method.