^4fA Four Port Formulation for Analyzing Cascaded Cabling Systems

摘要

^7fThe general increase in frequency requirements for twisted pair systems demands an increasingly detailed understanding of the performance of cabling systems. At the higher frequencies required for the forthcoming lOGHz Ethernet or for ATM transmission, the performance of a cascade is particularly important because of the effects of discontinuities along the transmission system: a simple example is the effect of connectors and cables having different characteristic impedances resulting in higher attenuation, return loss and forward echo. An adequate representation for cables and connectors that allows the determination of overall performance based on measurements of individual component performances, or the de-embedding of the performance of one unknown part is highly desirable. Clearly, a single twisted pair , or other, cable can be treated as a two port matrix, the cascading of these is well documented. However, if for example, cross-talk is to be considered in this way, a four port network is required to account for the two cables and the coupling between them. Cascaded four port scattering parameter matrices are not as widely discussed. This paper presents the equations for a cascaded four port network, with clear application to twisted pair cables. Numerical examples are presented to demonstrate the operation of the equations.