[SI-LIST] Re: why do I need mixed mode S parameters?
- From: axel stein <stein_axel@xxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Wed, 22 Dec 2010 12:50:18 -0800 (PST)
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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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