[SI-LIST] Re: S-parameter to SPICE
- From: "Hassan O. Ali" <hassan@xxxxxxxx>
- Date: Sat, 07 Dec 2002 00:49:29 -0500
Mick,
Your question has a lot of "catch phrases" that one has to be aware of
before giving you a "correct" answer.
"DC-20GHz":
Would you be able to obtain S-parameter values at DC? By extrapolation,
right? How do you then define a phase of a DC (non-oscillating) signal?
Besides, aren't S-parameters a linear wave phenomenon that implies
wave-like propagation?
I think, requiring the SPICE model to be valid at DC is quite a tall
order unless you have a priori knowledge of how the structure behaves at
DC. That wouldn't be the case with "complex structures" (another catch
phrase).
"Complex structures":
How complex? Is it by its many ports? Is it by its irregular S-parameter
characteristics? Is it by its radiative and coupling effects? Is it
non-linear?
Here this: if your structure is indeed "complex", getting a SPICE model
for it may also be a very complex matter and may even be impossible or
impractical. You see, when you represent a structure by its S-parameters
or a SPICE model, you assume it to be a "covered" black-box. That is it
won't interact with the rest of the circuit in any manner other than
through its defined ports and with the wave propagating in its dominant
(quasi-TEM) mode.
But that can simply be not true for "complex structures". In reality the
structure is "uncovered" hence subject to interacting with other circuit
structures through ways other than the ports, and may involve more than
one mode of wave propagation. That is even more true at higher
frequencies of your interest.
If your structure has irregular S-parameters, with resonances everywhere
(for example), you may also have difficulty creating a SPICE model for
such a broad frequency band other than using the method used by Ansoft's
Fullwave SPICE.
My 2 cent's worth.
Hassan.
"Zhou, Xingling (Mick)" wrote:
>
> Hello,
>
> Did anybody successfully generate broadband (DC-20GHz) SPICE model from S
> matrix for complex structures using the SPICE generator in ADS ? Or any
> other alternatives. I know Ansoft fullwave SPICE does the work.
> Unfortunately, some circuit simulators do not support the frequency
> dependent lookup table sources. We can definitely use [S] directly, but some
> users still prefer SPICE models. Any experience to share ?
>
> Thanks,
>
> Xingling(Mick) Zhou, PhD
> Signal Integrity Technologist
> Agere Systems
>
> Tel: 610-712-7462
> Fax: 610-712-4081
--
Hassan O. Ali Email: hassan@xxxxxxxx
12-2159 Elmira Drive Tel/Fax: (613) 721-9047
Ottawa, Ontario
CANADA K2C 1H3 WWW: http://www.glcom.com/hassan
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