Sainath -- I will give you the short answer, and refer you to the texts for the long answer. The even and odd modes are TEM modes, or at least quasi-TEM. TEM vs. higher order modes describes the field distribution across a single transmission line or waveguide structure. Quasi-TEM is a basic assumption of the transmission line theory on which we rely, including characteristic impedance and RLGC matrices. It requires that to first order, no field has a component in the direction of propagation. I usually rely on "Analysis of Multiconductor Transmission Lines" by Clayton R. Paul when I have questions of this sort. The higher order modes are significant to transmission line theory for the most part in that we try to make sure they don't exist, since they each propagate with their own velocities and make a mess of our nice clean square waves. Any E/M text with a waveguide section will describe the physics behind this. On the other hand, all TEM modes propagate. Analysis of the different TEM modes supported on a multiconductor transmission line structure is from my perspective more of a mathematical tool for breaking down a system into its most basic components. In the case of even/odd, this has a very practical application in differential signaling, but once we step outside of the symmetric coupled two-line regime, the math gets pretty complicated to try and define signaling schemes which coincide with any particular modes. So-called "full-wave" analysis, which essentially means "non-TEM analysis" for our purposes, is necessary for situations where we can't count on quasi-TEM assumptions. These situations occur when we step outside of the strict geometries of uniform transmission lines, or into certain loss regimes. Again, I would refer you to the book by Clayton R. Paul. -- Steve ------------------------------------------- Steven D. Corey, Ph.D. Time Domain Analysis Systems, Inc. "The Interconnect Modeling Company." http://www.tdasystems.com email: steve@xxxxxxxxxxxxxx phone: (503) 246-2272 fax: (503) 246-2282 ------------------------------------------- Muranyi, Arpad wrote: > To all, > > Sainath addressed his question to me, but I am going on vacation > and don't have the time to answer it. Could someone please > give him a good explanation to his questions? Thanks, > > Arpad > ================================================================= > > -----Original Message----- > From: sainath@xxxxxxxxxxxxx [mailto:sainath@xxxxxxxxxxxxx] > Sent: Monday, February 25, 2002 11:18 AM > To: si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] Re: Even mode, common mode, and mode conversion > > > > Arpad, > > This two T-lines vs one T-line mode distinction is confusing to me. > What makes the two T-lines support even or odd kind of modes? and the one > T-line support the TEM kind of modes? > Is it not possible to have TEM kind of mode propagation in a two T-line > system? > How would you define a MODE when it is meant even or odd mode ? and when it > is meant TEM mode? > > Thanks, > Sainath > > ----- Original Message ----- > From: "Muranyi, Arpad" <arpad.muranyi@xxxxxxxxx> > To: <si-list@xxxxxxxxxxxxx> > Sent: Monday, February 25, 2002 10:26 AM > Subject: [SI-LIST] Re: Even mode, common mode, and mode conversion > > > >>What may be confusing to some is that the word "mode" is used >>in different ways in different contexts, both involving >>transmission lines. >> >>So far most responses mentioned the even or odd mode, where >>the signals of ***two*** T-lines go either in the same or the >>opposite direction. >> >>The other usage of this word involves only one T-line (or >>wave guide or optical fiber) and describes how the electro >>magnetic waves propagate inside that line, one of the most >>familiar mode being the TEM (Transverse Electro Magnetic) >>mode. Don't confuse the two meanings of the word MODE! >> >>Arpad Muranyi >>Intel Corporation >>================================================================= >> > ------------------------------------------------------------------ > 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