[SI-LIST] Re: why do I need mixed mode S parameters?
- From: Peter.Pupalaikis@xxxxxxxxxx
- To: axel stein <stein_axel@xxxxxxxxx>
- Date: Wed, 22 Dec 2010 16:01:56 -0500
Hi Axel:
I get S31-S41-S32+S42.
The reason that this is different from Jeff's result is the port numbering
(which is why doing this with formulas really stinks).
Jeff's result seems to be for ports numbered:
1 2
3 4
My formula is for ports numbered
1 3
2 4
(where the left two numbers are the +/- singled ended ports that form mixed
mode port 1 and the
right two numbers are the +/- single ended ports that form mixed mode port
2).
You will need to verify your port numbering in order to get the correct
results.
Pete
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|12/22/2010 03:50 PM
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|[SI-LIST] Re: why do I need mixed mode S parameters?
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I have tried to use the formula from below to convert 4-port S-parameters
to a
SDD21 value. Unfortunately, the results was not even close to what my VNA
would
give me when directly displaying SDD21.
What I did was:
-measured the 4-port S-parameters --> results are available in dB-angle
format.
-I have converted the values first to linear-angle and then to linear_real
-
linear-imaginary format.
-I have added / subracted the linear_real values according to the formula
below.
-I have added / subtracted the linear_imaginary values according to the
formula
below.
-I converted the linear_real & linear_imaginary portions of the calculated
SDD21
back to linear-angle and finally dB-angle format.
My expectating would have been, that the SDD21 values that I have
calculated
this way would be reasonably similar to the directly measured SDD21,
however
these two are showing significant differences.
What have I missed here?
Thanks for your kind help,
axel
___________________
Loyer, Jeff wrote:
>The formula that I know of is:
>SDD21 = 1/2 (S21 - S41 - S23 + S43)
>
>For the reciprocal, symmetric system, S21 = S43, and S41 = S23. My
>algebra says that, for this system, SDD21 = S21 - S41. I didn't check
>your Maxim reference; please double-check it and let me know if it still
>disagrees with the formula.
>
>Also, a quick Google search of "Pozar book" would've found the
>information about that book - my thanks to Jeff of Agilent for providing
>that info.
>
>Not to beat you up, but please invest a few ergs before responding
>(especially to the entire list) - I invest a bit of time in my responses
>(to keep from asking the obvious, mis-stating information, and/or
>embarrassing my employer), and I appreciate others doing the same.
>
>Aside from that, I welcome folks letting me know if I've goofed and/or
>asking for clarification.
>
>Jeff Loyer
>
>
>-----Original Message-----
>>
>>For example, for the following circuit:
>>p1 ------- p2
>>p3 ------- p4
>>
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