10
CONDITION CONDITION MODEL TYPE
Tr > 5 TD
(lumped)
R >0.1* Rsource TLURCx Lumped RC,
lossy
" RC > 0.1* tr TLURCx Lumped RC,
lossy
" L/R > 0.1*tr TLUMPx Lumped, lossy
" Coupled
symmetric
This Article Lumped, coupled
" Coupled
asymmetric
This Article Lumped, coupled
Tr < 5 TD Loss negligible T Distributed
" Low loss Tlossy Distributed
" Coupled
symmetric
TxCOUPLED
KCOUPLEx
Distributed
Table 2. Model Selection For Different Rise Time And Primary Line Constants.
Distributed (T and TLOSSY)
OrCAD provides both ideal and lossy distributed models:
The parameters of the ideal transmission line are:
Z0 – Characteristic Impedance
TD – Transmission Delay
The parameters of the lossy transmission line are:
R - Resistance Per Unit Length
G - (Shunt) Conductance Per Unit Length
C - Self Capacitance Per Unit Length
L - Self Inductance Per Unit Length
LEN – Length Of Transmission Line
Lumped RC models (TLURCx)
An RC line is a special case where R/L is large (or the series inductance is small). The simplest model
for an RC line is a capacitor and a resistor.
