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 |------------> | From: | |------------> >----------------------------------------------------------------------------------------------------------------------------------------| |axel stein <stein_axel@xxxxxxxxx> | >----------------------------------------------------------------------------------------------------------------------------------------| |------------> | To: | |------------> >----------------------------------------------------------------------------------------------------------------------------------------| |si-list@xxxxxxxxxxxxx | >----------------------------------------------------------------------------------------------------------------------------------------| |------------> | Cc: | |------------> >----------------------------------------------------------------------------------------------------------------------------------------| |stein_axel@xxxxxxxxx | >----------------------------------------------------------------------------------------------------------------------------------------| |------------> | Date: | |------------> >----------------------------------------------------------------------------------------------------------------------------------------| |12/22/2010 03:50 PM | >----------------------------------------------------------------------------------------------------------------------------------------| |------------> | Subject: | |------------> >----------------------------------------------------------------------------------------------------------------------------------------| |[SI-LIST] Re: why do I need mixed mode S parameters? | >----------------------------------------------------------------------------------------------------------------------------------------| |------------> | Sent by: | |------------> >----------------------------------------------------------------------------------------------------------------------------------------| |si-list-bounce@xxxxxxxxxxxxx | >----------------------------------------------------------------------------------------------------------------------------------------| Hi SI-Gurus,Legal Disclaimer: The information contained in this message may be privileged and confidential. It is intended to be read only by the individual or entity to whom it is addressed or by their designee. If the reader of this message is not the intended recipient, you are on notice that any distribution of this message, in any form, is strictly prohibited. If you have received this message in error, please immediately notify the sender and delete or destroy any copy of this message 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 >> ------------------------------------------------------------------ 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 ------------------------------------------------------------------ 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