Length of the cable appears irrelevant. I just click the little "risetime" icon on the scope screen to get the 20-80% tr. Chris -----Original Message----- From: Joseph Wang [mailto:JYWANG@xxxxxxxxxx]=20 Sent: Wednesday, June 29, 2005 2:11 PM To: Chris Padilla (cpad); si-list@xxxxxxxxxxxxx Subject: RE: [SI-LIST] Agilent TDR Normalization Questions Have you tried to use different length of cables? Could you share results to us all? And how do you measure the rise time? With TDT or another sampling scope, or 40GS/s real time scope? Regards, Joseph Wang -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Chris Padilla (cpad) Sent: Wednesday, June 29, 2005 2:03 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Agilent TDR Normalization Questions I've read the Help files included with my 86100B w/ 54754A TDR module and I follow what happens when one Normalizes to the end of cable and/or test fixture so I understand that. There is an IFT and FIR filters being used and then FFT'ing back. I did a little check, however, and have some seemingly strange results that I hope someone here can explain. I find that as long as I am using decent high-quality cables, the Normalization routine will degrade (increase) the ristime of the step from ~30 ps (unnormalized step) to ~65 ps: a factor of ~2+. I tried this for several different cable I had laying around and they are all about the same as far as Normalization goes. Expectedly, the normalized step is cleaned up of some higher-frequency content wiggles at the top of the step. Next, I decided to Normalize to the end of the TDR module or put another way, I didn't add any cable or test fixtures to the TDR module...I just screwed my Cal Standards right to the 3.5 mm SMA on the TDR module. Guess what? I got the same ~2x increase of risetime as if I had some cable and/or test fixtures attached! Anyone have an explanation for this? Seems to me that as long as I use those "decent high-quality cables", all the Normalization adjustments happen INSIDE the TDR module!? What am I missing here...this doesn't seem right. My next questions regards even using Normalization in the first place. I often see a lot of TDR plots (with TDA Systems logo on them! ;o) ) that don't appear to have been normalized. It is probably for good reason since Normalization appears to chop the bandwidth of the scope right in half. I have been learning to use I-Connect and I'm confused whether or not I should be using the Normalization routine on my scope. Thanks, Chris Padilla Cisco Systems San Jose, CA ------------------------------------------------------------------ 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 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: =20 //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 =20 ------------------------------------------------------------------ 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 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: //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