Abstract
High-speed transmission lines are commonly routed as differential lines to control sensitivity to noise on the reference planes at higher speeds. The preferred method of characterization of differential lines is in terms of mixed-mode scattering parameters, as they provide insight into the behavior of differential and common signals, as well as the mode conversion among them. These mixed-mode scattering parameters can be mathematically obtained from single-ended parameters, which can for example be measured with a 4-port vector network analyzer. There has been recent concerns about the so-obtained mixed-mode scattering parameters, especially for tightly-coupled lines, resulting in extended or modified definitions of mixed-mode scattering parameters. This can be a point of confusion in interpreting the behavior of differential lines. In this paper we introduce the mixed-port hybrid parameters, which do not suffer from any such ambiguous definitions, as they are based on intuitive differential and common-port excitations of the network. As such, mixed-port hybrid parameters can be used to analyze the mixed-mode performance of any arbitrary 4-port network, certainly including coupled or asymmetrical lines, without any ambiguity.
Number of Sections Necessary for Transmission Line Model Used in Transient Network Analyzer