[SI-LIST] Re: Impedance calculation of asymmetric coupled lin es?
- From: houfei chen <hfchen73@xxxxxxxxx>
- To: JK100005@xxxxxxxxxxxxxxxx, dgun@xxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Thu, 17 Oct 2002 13:52:26 -0700 (PDT)
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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> > --
> > Fred Balistreri
> > fred@xxxxxxxxxxxxx
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> > http://www.apsimtech.com
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>
>
> --
> Daniel
> ZZZ-dgun-ZZZ-@xxxxxxxxxxxxxxx
> (remove the Z-'s to reply--they're what I do when I
> read spam)
>
> --
>
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