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##

Transmission Lines (General)

- General Form:

`t`*name* *n1 n2 n3 n4* [*model*]
[*param*=*value* ...]

o*name* *n1 n2 n3 n4* [*model*]
[*param*=*value* ...]

- Examples:

`t1 1 0 2 0 z0=50 td=10ns
`

tw 1 0 2 0 z0=50 f=1ghz nl=.1

tx 1 0 4 0 l=9.13e-9 c=3.65e-12 len=24

oy 2 0 4 0 level=2 l=100pH c=5pf r=1.5 len=12

oz 2 0 4 0 level=2 tranmod len=12

In *WRspice*, the transmission line element represents a general
lossless or lossy transmission line. There are actually three
historical models unified in the *WRspice* model: the SPICE3
lossless transmission line, the SPICE3 lossy (LTRA) transmission line
convolution approach of Roychowdhury and Pederson [13], and the
Pade approximation lossy line approach of Lin and Kuh [14].

The device line is keyed by the letters ``t`' and ``o`'
equivalently, as above. In SPICE3, ``o`' calls the lossy
convolution model, but this is not necessarily the case in
*WRspice*. One can enforce use of the convolution model by using
```level=2`'' in the device or model line, the default (```level=1`'') is the Pade approximation model. In the lossless case,
the `level` parameter has no effect.

Above, *n1* and *n2* are the nodes at port 1, *n3*
and *n4* are the nodes at port 2. Note that this element
models only one propagating mode. If all four nodes are distinct in
the actual circuit, then two modes may be excited. To simulate such
a situation, two transmission line elements are required.

There is a fairly lengthly list of parameters which can be applied
in the device line, or in a model. If a model is referenced in the
element line, the element defaults to the parameters specified in
the model, though any of these parameters can be overridden for the
element if given new values in the element line.

**Subsections**

** Next:** Model Level
** Up:** Passive Element Lines
** Previous:** Switch Model
** Contents**
** Index**
Stephen R. Whiteley
2024-10-26