*From*: Chris Cheng <Chris.Cheng@xxxxxxxxxxxx>*To*: si-list@xxxxxxxxxxxxx*Date*: Tue, 17 May 2005 15:43:14 -0700

I think the original question was asking for Sdd21, not S21. -----Original Message----- From: lgreen [mailto:lgreen22@xxxxxxxxxxxxxx] Sent: Tuesday, May 17, 2005 2:15 PM To: Chris.Cheng@xxxxxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: RE: [SI-LIST] Re: Estimate ISI with S parameters -- Using TDR to do SDD21 correlation? Hi, Chris, If you transform into differential, you lose the (important) common mode information. If you are planning on using the extracted S-parameters in a commercial SI tool, you might want to leave them in standard Touchstone format. A number of companies already support Touchstone, even if they do not yet support the full IBIS ICM spec. Some tools can correct for passivity/causality (various approaches). But you might want to at least check this yourself, since it can help catch data problems. Best regards, Lynne "IBIS training when you need it, where you need it." Dr. Lynne Green Green Streak Programs http://www.greenstreakprograms.com 425-788-0412 lgreen22@xxxxxxxxxxxxxx -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Chris Cheng Sent: Tuesday, May 17, 2005 1:22 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Estimate ISI with S parameters -- Using TDR to do SDD21 correlation? I have to admit I've never try this before but I am about to give it a = shot myself so tell me I am crazy or worst trying. 1) If you have a TDR head, you should be able to do single ended TDR and TDT. 2) If you treat your differential lines as 4 ports, you can measure TDRxy and TDTxy on sequential pairs of ports while terminating the = other 2 ports with 50 ohm terminators.=20 3) If you invoke symmetry on the lines you just need to measure the upper or lower diagonal of the matrix. 4) Do your FFT to transform the TDT/TDR to single ended Sxy parameters 5) Clean them up with your favorite SOLT error corrections methods 6) Transform the Sxy matrix into mix mode Sddcc matrix. My questions are : a) Can this be done ? b) How "clean" do I need on the SOLT error corrections ? Can it be skipped ? c) Do I have to worry about passivity on these extracted parameters ? ------------------------------------------------------------------ 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: http://www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: http://www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu

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