Here is the problem. We are confusing the classical definition of TEM odd/even mode (which only happen in a two line transmission line system) and the generic SI term of odd/even mode in crosstalk analysis. A three conductors TEM mode transmission line system has three not two modes. What you are describing is the generic SI engineering term of analyzing the worst case impact of aggressor to the victim lines where the aggressors are switching in the same direction as the victim (even) or opposite (odd). There is no TEM odd or even modes involved. You can even extend this definition to an N line system. The propose of such analysis is to understand the worst case impact of a victim line (signal degradation and propagation variation) under the worst case impact of crosstalk. May be we should drop the TEM mode definition so as not to confuse people more ? -----Original Message----- From: Mary [mailto:mary@xxxxxxxxxxxx] Sent: Tuesday, February 26, 2002 4:04 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Even mode, common mode, and mode conversion Don't confuse the issue by referring to what happens in an inhomogeneous medium. I believe Mr. Haedge's point is valid. After all, aren't there an infinite number of ways to divide a signal on three conductors into two complete-orthogonal modes? The even/odd mode description is convenient for many reasons. However, I don't think there's anything magical about these modes. They do not propagate down a transmission line independent of one another. It's true that if you launch an odd (or even) mode signal down a symmetric pair of traces you will theoretically get an odd (or even) mode signal at the termination. However, if you launch an odd and an even mode signal at the same time, you no longer have the symmetry that was responsible for the "single-mode" propagation. I don't believe it's proper to assume that the odd-mode propagation and even-mode propagation can be analyzed independently. Yet there is a tendency on this list to ignore what happens to the even mode component when the "intentional" signal is all odd mode. Mary ------------------------------------------------------------------ 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