Fabrizio, The dominant generation mechanism of the common-mode of a differential transmission line seems to be delay skew, from our investigations. Hence, to minimize common-mode generation, minimize the path length skew and live with the short section with a change in the line-to-line coupling. I can point you to a paper or two in the archives of the IEEE EMC Symposia. Jim Knighten NCR San Diego, CA On board designs with nets running Gigabit signals, I constantly see that one side of the differential pair is serpentined/lengthened to perfectly match it to the delay of other side of the differential pair. This causes the positive and negative lines to not be coupled for a few hundred mils, which can result in common mode noise. My question is, which of the two evils is worse, having a little bit of skew within the pair or having the pairs uncoupled for a portion of the run? Thanks very much, Fabrizio Zanella Signal Integrity EMC Corporation 508-435-2075, x14645 fzanella@xxxxxxx ------------------------------------------------------------------ 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 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 ------------------------------------------------------------------ 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 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