[SI-LIST] Re: Impedance calculation of asymmetric coupled lin es?
- From: "john lipsius" <johnlipsius@xxxxxxxxx>
- To: <hfchen73@xxxxxxxxx>, <JK100005@xxxxxxxxxxxxxxxx>,<dgun@xxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Fri, 18 Oct 2002 16:50:14 -0700
See my other reply.
hfchen is really agreeing with Jim but missed the fact, as Jim says,
that the lack of symmetry (ie: Z11 != Z22 and/or Z12 != Z21) results in
BOTH even and odd modes are present EVEN IF driven differentially or
commonly. The asymmetric topology converts one to the other partially.
Pure mode requires symmetry!
----- Original Message -----
From: "houfei chen" <hfchen73@xxxxxxxxx>
To: <JK100005@xxxxxxxxxxxxxxxx>; <dgun@xxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
Sent: Thursday, October 17, 2002 1:52 PM
Subject: [SI-LIST] Re: Impedance calculation of asymmetric coupled lin es?
>
> I am not sure about that, but I think Even and odd are
> defined by signal input, as long as you have a
> differential input, it will be transmitted as odd
> mode, it's just the field pattern of this odd mode
> will depend on different line geometry.
> For symmetric coupled line, the even mode is really
> "even" and odd mode is really "odd" due to the
> symmetry of the structure, thus differential input has
> the best cancellation effect. With asymmetric lines,
> the even and odd mode is no long "even" and "odd" in
> field pattern, thus created additional EMI problem.
> For extreme cases, two symmetric lines far apart still
> support even and odd mode, but these two modes now
> don't have much difference.
>
> --- "Knighten, Jim L" <JK100005@xxxxxxxxxxxxxxxx>
> wrote:
> >
> > If you have coupled lines, then both even and odd
> > modes are supported. An
> > asymmetric set of coupled lines sounds as if they
> > are unbalanced. In that
> > case, you will find that you have both differential
> > and common modes present
> > on the transmission lines, even with a purely
> > differential input.
> >
> > Your simulation program probably only considers the
> > differential signal.
> > The common mode is usually an undesirable EMI noise
> > signal.
> >
> > Jim
> >
> >
> > Jim Knighten, Ph.D.
> > Teradata, a Division of NCR http://www.ncr.com
> > 17095 Via Del Campo
> > San Diego, CA 92127
> > USA
> > Tel: 858-485-2537
> > Fax: 858-485-3788
> > jim.knighten@xxxxxxx
> >
> > -----Original Message-----
> > From: D G [mailto:dgun@xxxxxxxxxx]
> > Sent: Monday, October 14, 2002 10:12 AM
> > To: si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: Impedance calculation of
> > asymmetric coupled
> > lines?
> >
> >
> > Fair enough. What do I get out of an asymmetric
> > coupled line when I put a
> > differential signal into it? How do I simulate this
> > with transmission line
> > models?
> >
> >
> > From: Fred Balistreri <fred@xxxxxxxxxxxxx>
> > > If they are not electrically symmetrical then they
> > cannot be called
> > > differential so the definition does not apply.
> > >
> > > Best Regards,
> > >
> > > D G wrote:
> > > >
> > > > The calculation of differential and common-mode
> > impedances is well known
> > for symmetric coupled lines. How about asymmetric
> > coupled lines, where
> > Zeven for line1 is not equal to Zeven for line2?
> > > >
> > > > --
> > > > Daniel
> > > > ZZZ-dgun-ZZZ-@xxxxxxxxxxxxxxx
> > > > (remove the Z-'s to reply--they're what I do
> > when I read spam)
> > > >
> > > > --
> > > >
> >
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