[SI-LIST] : limitations of spice for SI modelling

Christopher Albert (Christopher_Albert@notes.teradyne.com)
Tue, 9 Mar 1999 11:51:47 -0500

My question pertains specifically to modelling lossy transmission lines in
Pspice using the built in RLGC model, but I think that it may have implications
for other implementations of lossy transmission line models as well.

Pspice allows R and G to be functions of a laplace variable [frequency]. In
theory, skin and dielectric loss can be modelled if the correct function of R
and G are chosen (in my experience, G must be set much higher than actual to get
correlation, but this is another question !). Alternately, a frequency dependent
two port representation can be created using Pspice's analog behavioural
modelling suite. In this case, the two port might be described in terms of
scattering (this is outlined in Pspice Apps notes) or ABCD matrices and
implemented with analog behavioural modelling components.