ngmultidec writes an ngspice input file to standard output which describes a sub-circuit for coupled lines
using uncoupled simple lossy lines.
Each generated subcircuit models a 4-conductor transmission line with
the following parameters: length
l, line capacitance
c, line resistance
r, line conductance
k, inter-line capacitance
l. Derived parameters are:
ctot. The values of
c, the model name, the number of conductors and the length of the line
must be specified.
It is important to note that the model is a simplified one - the
following assumptions are made: 1. The self-inductance l, the
self-capacitance ctot (note: not c), the series resistance r and the
parallel capacitance g are the same for all lines, and 2. Each line
is coupled only to the two lines adjacent to it, with the same
coupling parameters cm and lm.
The first assumption implies that edge effects have to be neglected.
The utility of these assumptions is
that they make the sL+R and sC+G matrices symmetric, tridiagonal and
Toeplitz, with useful consequences (see the paper referenced below).
It may be noted that a symmetric two-conductor line is
represented accurately by this model.
Standard C language scientific (exponent) notation may be used for options numeric values.
Efficient Transient Simulation of Lossy Interconnect,
J.S. Roychowdhury and D.O. Pederson,
Proceedings of the Design Automation Conference,