Sainath -- I'll see what I can do without getting too embroiled in the details: 1. What makes the two T-lines support even or odd kind of modes? and the one T-line support the TEM kind of modes? For the first part of #1, I would refer to the book by Paul. A system doesn't really support modes, it has modes. Sometimes in analysis we break down voltages and currents into the system modes to simplify analysis. If you come up with a good answer to the first part of #1, you will understand that the even and odd are also TEM modes in the same way that a single line has a TEM mode. 2. Is it not possible to have TEM kind of mode propagation in a two T-line system? Yes, as you will see in my previous post. 3. How would you define a MODE when it is meant even or odd mode ? and when it is meant TEM mode? For the first part of #3, you can refer to Paul's book for a rigorous mathematical definition. You can also refer to Eric Bogatin's post to this thread for what may be a more intuitive definition. For the second part of the question, refer to my earlier post for a short definition, or to Paul's book or any E/M book that covers waveguides for a longhand definition. > > > > Sainath Nimmagadda wrote: > Steve, > > I suppose your message was to address my questions to Arpad. > There are 3 questions and I'm not clear which one is addressed. > Is it possible to say few simple words about each question separately? > > Thanks, > Sainath > > ----- Original Message ----- > From: "Steve Corey" <steve@xxxxxxxxxxxxxx> > To: <si-list@xxxxxxxxxxxxx> > Sent: Tuesday, February 26, 2002 7:20 AM > Subject: [SI-LIST] Re: Even mode, common mode, and mode conversion > > > >>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 >> >> >> > > ------------------------------------------------------------------ > 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 > > > > -- ------------------------------------------- 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 ------------------------------------------- ------------------------------------------------------------------ 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