Intra-Pair Skew Propagation Graph (ISPG): An Analytical Model for Cascaded Channels

TL;DR

This paper introduces the Intra-pair Skew Propagation Graph (ISPG), a novel analytical framework that accurately models cumulative skew in high-speed differential channels, validated through simulations and measurements.

Contribution

The paper presents the ISPG, a new graph-based analytical model explicitly incorporating skew into S-parameters for cascaded high-speed channels.

Findings

Excellent accuracy of ISPG validated against simulations and measurements.

Robustness of the model for complex, cascaded transmission lines.

Provides a computationally efficient alternative to electromagnetic simulations.

Abstract

As data rates scale, intra-pair skew has become a critical bottleneck for high-speed differential signaling. Current analytical models are often limited, while 3D electromagnetic simulations are computationally intensive. This paper presents a comprehensive analytical framework for intra-pair skew in generic asymmetric coupled transmission lines, explicitly integrating skew into S-parameter formulations. We introduce the Intra-pair Skew Propagation Graph (ISPG), a novel graph-based methodology for calculating cumulative skew in complex, cascaded channels. The proposed framework is validated against both S-parameter simulations and empirical measurements of a 2m bulk twinax cable assembly, demonstrating excellent accuracy and robustness for high-speed interconnect design.