[SI-LIST] Re: S-parameter Bisection
- From: "Zabinski, Patrick" <zabinski.patrick@xxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Tue, 10 Nov 2009 17:30:52 -0600
> Is it possible to split a passive S-parameter matrix into two equal
sections?
Yes - but with several caveats.
We tried several approaches over the years, and as Brett mentions, it
comes down to the assumptions you make.
The square-root approach is reasonable under a very-limited set of
situations where there are no launch effects and the structure is
exactly symmetrical. If you inject a TDR and see any anomalies at the
launch (i.e., connector, probe point, ...), then the square-root method
quickly falls apart. For the majority of board-level structures, the
connector launches are significant enough to warrant this approach
useless.
Another approach is bi-section whereby you assume the line is
symmetrical - but there can be some launch effects. There are more
unknowns than equations, so you need to make some assumptions that
invite inaccuracies and/or completely wrong answers. We developed an
approach several years ago (**), and it has worked fairly well for us in
many situations. Unfortunately, when return loss is high (-15 dB), then
the approach becomes a bit inaccurate. When insertion is excessive (-10
dB), then the approach falls apart.
(**) Daniel, E. S., N. E. Harff, V. Sokolov, S. M. Schreiber, and B. K.
Gilbert: Network Analyzer Measurement De-embedding Utilizing a
Distributed Transmission Matrix Bisection of a Single THRU Structure.
Proceedings of the 63rd ARFTG Conference Digest, pp. 61-68, June 11,
2004, Dallas, Texas.
Another approach is to develop custom structures such that you can use
them for in-situ VNA calibration. SOLT, LRM, ... can all be implemented
in structures, but that approach too has several challenges -
particularly in areas of repeatability, calibration coefficients, etc.
There does not appear to be a quick-n-easy approach - at least not that
we've found.
The most reliable - and often most time consuming - approach generally
follows Steve's advice of creating a model to match your measurement,
breaking the model into two, then using the sliced model to your
deembedding parameters. It requires several steps, good SI analysis
tools/skills, and a bit of luck.
If you find a quick-n-easy solution, let us all know.
Good luck,
Pat Zabinski
Mayo Clinic
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List technical documents are available at:
http://www.si-list.net
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
