Hello Igor,

        In MultiCal and StatistiCAL you put in an estimate for the length of the fixture. The programs use this estimate at the lowest frequency to resolve this phase ambiguity. This is usually not difficult if the frequency is low enough. Then the programs use the solution at this lowest frequency and the length estimate to estimate the phase at the next frequency point, and so on. In this way, the programs step from frequency to frequency, each time estimating the phase at the next frequency point. The approach is not perfect, but it usually works in practice.

I hope that his is helpful,

Dylan




At 09:37 AM 7/30/2008, you wrote:

Thank you Dylan

When S21=S12 there is a 180deg ambiguity in the answer because of the
square root function. Similarly, there is a square root to solve for
S22 of the input adapter that gives another 180deg ambiguity.

The first 180deg ambiguity is ok because usually we need S12*S21
products and as long as the same 180deg error is made in calculating
both S-parameters of the input and the output adapters, the DUT
deembedding will be correct. However I'm not sure the 180deg ambiguity
in S22 of the input adapter is as easy to deal with.

BTW, I'd like to write a matlab routine to determine the full
S-parameters of the input and the output adapters.

Regards
Igor

>
> Sorry Igor,
>
> When de-embedding adapters you can use reciprocity
(S21=S12) to
> solve this problem. Both MultiCal and StatistiCAL allow you to solve
for
> adapter scattering parameters with multiline TRL, and that would be
a good
> place to start.
>
> Next time I will have to be more careful about getting the
reply
> to you!
>
> Best,
>
> Dylan
>
>
> At 03:54 PM 7/22/2008, you wrote:
>
> >Hello Dylan
> >
> >Looks like you replied to my message but the text did not show?
> >
> >Regards
> >Igor
> >
> >--- In < mailto:mtt-11%40yahoogroups.com>mtt-11@yahoogroups.com, Dylan
> >Williams <dylan@> wrote:
> > >
> > > At 07:46 AM 7/22/2008, you wrote:
> > >
> > > >Hello
> > > >
> > > >I've been following Doug Rytting presentation called "TRL
> > > >Calibration". The equations all make sense and give good results
> > > >however the presentation does not seem complete as it does not
discuss
> > > >how to do the final step of separating e10e32 and e23e01 terms
(these
> > > >terms are the S12's and S21's of the two error adapters).
> > > >
> > > >Can anybody help me with this? I'd like to determine the
S-parameters
> > > >of the two error adapters.
> > > >
> > > >Thank you
> > > >Igor
> > > >
> > > >
> > >
> > >
> > >
> > > -----------------------------------------------------
> > > Dylan Williams <dylan@>
> > > NIST 818.01 <dylan@>
> > > 325 Broadway [+1] (303)497-3138 (TEL)
> > > Boulder CO 80305 USA [+1] (303)497-3970 (FAX)
> > >
< http://www.boulder.nist.gov/dylan/ > http://www.boulder.nist.gov/dylan/
> > > -----------------------------------------------------
> > >
> >
> >
>
>
>
> -----------------------------------------------------
> Dylan Williams <dylan@...>
> NIST 818.01 <dylan@...>
> 325 Broadway [+1] (303)497-3138 (TEL)
> Boulder CO 80305 USA [+1] (303)497-3970 (FAX)
> http://www.boulder.nist.gov/dylan/
> -----------------------------------------------------
>

-----------------------------------------------------
Dylan Williams               <dylan@...>
NIST 818.01                  <dylan@...>
325 Broadway                 [+1] (303)497-3138 (TEL)
Boulder CO 80305 USA         [+1] (303)497-3970 (FAX)
http://www.boulder.nist.gov/dylan/
-----------------------------------------------------