[SI-LIST] Re: N-port problem in interconnects

  • From: "Patrick Zilaro" <pzilaro@xxxxxxxxxxxx>
  • To: bhadhua@xxxxxxxxxxxx, si-list@xxxxxxxxxxxxx
  • Date: Thu, 30 Oct 2003 14:26:27 -0800

I think you got it.  Cadence Spectre represents each port with a positive
and a negative terminal.  This is just like, if you were measuring these
s-parameters using a VNA and microprobes.  The microprobes each have a
positive and a negative terminal.  By the way, some circuit simulators that
can handle s-parameters choose to combine all the negative terminals into
one common "reference" terminal.  Spectre keeps them separate.

Regards,

Patrick Zilaro
SI Packaging Engineer
Broadcom Corporation

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Amitava Bhaduri
Sent: Thursday, October 30, 2003 2:03 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] N-port problem in interconnects




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


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

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