From: Degerstrom, Michael J. (firstname.lastname@example.org)
Date: Thu Dec 21 2000 - 06:37:01 PST
I think what the original poster implied was that the
s-parameters are taken on a uniform transmission line
structure. Although I am not certain of this. If this
is the case then one can theoretically mathematically convert the
measured s-parameters to RLCG vs. frequency. But in practice,
I have been only able to do this for very good quality
structures with very good launch structures and very
good high frequency microwave probes. I have had much
better luck in converting s-parameters from simulation to
RLCG vs frequency.
Mike Degerstrom Email: email@example.com
200 1st Street SW
Gugg. Bldg. RM 1042A Phone: (507) 284-3292
Rochester, MN 55905 FAX: (507) 284-9171
> -----Original Message-----
> From: Bob Lewandowski [mailto:Bob.Lewandowski@Vixel.com]
> Sent: Thursday, December 14, 2000 5:44 PM
> To: Djohan Adrianus
> Cc: 'firstname.lastname@example.org'
> Subject: Re: [SI-LIST] : s parameters to rlgc matrix
> I don't think there is any direct way to go from S-parameters
> to a model. Some
> sort of circuit topology is needed.
> If the circuit is a lumped structure with parasitics, some
> topology is defined
> in schematic form, and model element values assigned. Then
> it is possible to
> take an rf circuit simulator, (Agilent ADS, Ansoft,
> Eagleware, Aplac, etc.) and
> match the calculated S-parameters of the model to the
> measured data. The
> circuit model element values are adjusted by the software to
> minimize the
> calculated-to-measured errors. This process assumes you have
> a good starting
> value for each circuit element. You just can't put down a
> bunch of Rs, Ls, and
> Cs and let the software go nuts. Garbage-in-garbage-out
> applies here big time.
> If the network is resonably simple, inspection of the S11,
> and S22 plots in
> Smith chart form will yield a circuit model and element
> values for input and
> ouput circuits to an experienced eye.
> If the circuit is a distributed structure then the problem is
> more difficult
> because the order of the model has to be estimated (number of
> RLGC sections).
> This will effect results big time. But the procedure is
> basically the same.
> Assign starting values, and let the software optimize to
> match the model to the
> ---Bob Lewandowski
> Vixel Corp.
> "Djohan, Adrianus" wrote:
> > Hi,
> > I'm wondering if anyone has success with finding an
> equivalent RLGC element
> > for a set of s parameters. For example: Given a set of S
> parameter as a
> > function of frequency (2 by 2 by f) as typically one would
> get from a
> > network analyzer. What would be the method to compute an
> equivalent RLGC
> > element for each frequency, assuming that the RLGC element
> is 1/nth of the s
> > parameters?
> > THanks,
> > Adrianus
> > Adrianus Djohan
> > Hardware Engineer
> > Tenor Networks, Inc.
> > 100 Nagog Park
> > Acton, MA 01720
> > Phone: (978) 206-5175
> > (978) 264-4900 Ext. 175
> > Fax: (978) 264-0671
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