Doug, Good question! I also suspect that you are not the only one trying to figure it out. The term "common-mode" is often used in different contexts, so its use can be confusing. What this thread on "Even mode, common mode, and mode conversion" is all about is signal behavior on differential transmission lines. The discussion has nothing to do with single (or single ended) transmission lines. On differential traces, these two modes can exist. Even mode is when both lines are excited with the same voltage (common excitation). Odd mode is when the lines are excited with equal, but opposite voltages (differential excitation). Now, you would think that odd-mode impedance would be the same as differential-mode impedance. Not so. To make things more confusing, the industry conventions are such that even and odd mode impedance is related to common and differential mode impedances by the following: Odd mode impedance = 0.5 * Differential Mode impedance Even Mode impedance = 2 * Common-mode impedance These are not different phenomena, just two different conventions in the way that you can look at the same transmission line. Jim Jim Knighten, Ph.D. Teradata, a Division of NCR http://www.ncr.com 17095 Via Del Campo San Diego, CA 92127 USA Tel: 858-485-2537 Fax: 858-485-3788 jim.knighten@xxxxxxx -----Original Message----- From: Doug Brooks [mailto:doug@xxxxxxxxxx] Sent: Monday, February 25, 2002 9:31 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Even mode, common mode, and mode conversion Gurus, I've been following the thread on mode conversion and suspect I am not the only one with this question. Can someone explain, in layman's terms: The distinction between even mode and common mode? between odd mode and differential MODE (not to be confused with differential traces) And does the existence of differential traces add any complications to these distinctions? Thanks for bringing the dummies along with you! Doug Brooks ------------------------------------------------------------------ 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 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 ------------------------------------------------------------------ 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 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