# [SI-LIST] N-port problem in interconnects

• To: si-list@xxxxxxxxxxxxx
• Date: Thu, 30 Oct 2003 17:03:09 -0500 (EST)

```
Hi,

I am trying to model the interconnects using the "nport" feature of
spectre. Take for example I have 2 conductors (A1-B1 and A2-B2). A1, B1,
A2, B2 are connected to other circuit elements, like transistors for
example. I am trying to model only the interconnect portion.
_                           _
B1  | |                     B2  | |
| |                         | |
| |                         | |_____________
| |_____________            |_____________  |
|____________  |                          | |
| |                          | |
| |                          | |
| |                          | |
| |                          |_|
A1 |_|                        A2

I am able to obtain a (2 x 2) impedance matrix [Z] for this 2-conductor
system. Using the formula (Z-1)(Z+1)^-1, the impedance parameters can be
converted to s-parameters (as "nport" of spectre operates on
s-parameters).
The problem is how do I represent this 2-conductor system
in spectre "nport" format. If you do "spectre -help nport" you will see
that the instance statement looks like:

Name ( t1 b1 [t2] [b2] ... ) nport <parameter=value> ...,

where the terminals should be given in pairs. Can this 2-conductor system
be realized as 2-port network? What would the common terminals be (-ve
terminal) in this case? In this 2-port interconnect network can I
represent the first port as (A1, B1) where A1 is +ve terminal and B1 is
-ve terminal, while the second port being (A2, B2) where A2 is +ve
terminal and B2 is -ve terminal?

(note: this is only an instance of a 2-conductor system. The same problem
can be extended for any "n-conductor system", where n=1,2,3,4,5...etc)

Would appreciate any help on this.
Thanks,
Amit

Research Assistant
527 ERC
University of Cincinnati
OH - 45220
ph : 513-556-3025

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