[SI-LIST] Re: why do I need mixed mode S parameters?
- From: Istvan Novak <istvan.novak@xxxxxxxxxx>
- To: axel stein <stein_axel@xxxxxxxxx>
- Date: Wed, 22 Dec 2010 16:00:37 -0500
Axel,
I would first check to make sure the port numbering is what the formula
assumes.
Regards,
Istvan
On 12/22/10 15:50, axel stein wrote:
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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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