[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
> >>>>=================================================================
> >>>>
> >>>>
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>
> --
> -------------------------------------------
> 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
> -------------------------------------------
>
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