eldo_user

Working with S, Y, Z Parameters
Implementation Issues
In general, an n-port has a 2n x 2n mixed-mode S parameter matrix of the following form:
Implementation Issues
Eldo uses three methods to simulate an S-model given by S, Y, or Z parameters. These methods
are briefly described below:
• Complex Pole Fitting (CPF) technique is a method based on complex-pole fitting of the
original dependence. During an initial “fitting” stage, the model’s given dependence is
represented as a sum of simple first-order components, each one defined by its complex
pole and residue. The result of fitting is re-usable; once generated, the list of poles and
residues is stored in a *.pls file and can be used repeatedly for simulations without the
need to re-fit. This file has the same name and location as the original data (Touchstone)
file.
The representation of frequency dependence created by fitting enables fast and accurate
transient simulation of the S-model. Simulation progresses linearly in time, using an
effective, recursive, convolution-based algorithm. Although poles/residues can be used
to build an equivalent circuit, this is not needed or recommended, for performance
Eldo® User's Manual, 15.3 695