Aubrey, Cool. Microwave guys worry about their modes and SI guys worry about their modes. Having background in both microwave and SI, I was trying to get at what is fundamentally common to these two seemingly different types of modes. Once I get that, these different mode types, descriptions and semantics are mere spices to give personality to those subjects ...and, of course, job securities - as some one already pointed out. Thanks, Sainath ----- Original Message ----- From: <Aubrey_Sparkman@xxxxxxxx> To: <sainath@xxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx> Sent: Tuesday, February 26, 2002 1:04 PM Subject: RE: [SI-LIST] Re: Even mode, common mode, and mode conversion > Sainath, > Perhaps I can help. Seems like there are two different types of modes being > confused here. > > Type 1) > Any single transmission line will propagate the TEM mode up to it's cut-off > frequency, then you get other modes like TE11, TM11, etc which means one of > the cross-sectional dimensions is greater than 1/2 wavelength (if memory > serves, microwave experts feel free to correct me) but you should > investigate waveguides if you want to understand all these different types > of modes. I haven't seen this type of modes be relevant to SI engineers in > the past. Perhaps the hi speed serial links will change that. Most of our > chip-to-chip signals (on the same PCB) signal each other using TEM mode. > > Type 2) > SI engineers talk about odd and even modes when a pair of signals are either > in phase or 180 degrees out of phase. The pair of odd mode signals see a > differential impedance and SI engineers call that differential signaling. > The noise that disturbs the pair is usually "in phase" and we hope for good > common mode rejection; the differential receiver sees no difference. If you > consider the odd mode pair having an "a" signal and a "b" signal, the "a" > signal will see the odd mode impedance when the pair of signals are 180 > degrees out of phase. The "a" signal will see the even mode impedance when > the pair of signals are in phase. > > Hope this helps. > > Aubrey Sparkman > Signal Integrity > Aubrey_Sparkman@xxxxxxxx > (512) 723-3592 > > > > -----Original Message----- > From: sainath@xxxxxxxxxxxxx [mailto:sainath@xxxxxxxxxxxxx] > Sent: Tuesday, February 26, 2002 1:31 PM > To: si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] Re: Even mode, common mode, and mode conversion > > > > Steve, > > I better leave my three questions at that with all those 'refer to's. > My attention is turned to the statement: "A system doesn't really support > modes, it has modes." > Again, is it Paul's book that I should refer to? > > Thanks, > Sainath > > ----- Original Message ----- > From: "Steve Corey" <steve@xxxxxxxxxxxxxx> > To: <si-list@xxxxxxxxxxxxx> > Sent: Tuesday, February 26, 2002 10:48 AM > Subject: [SI-LIST] Re: Even mode, common mode, and mode conversion > > > > > > 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 > > > > > > ------------------------------------------------------------------ > 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