FreeLists / si-list / [SI-LIST] Re: Even/Odd mode impedance

[Ray Anderson <Raymond.Anderson@xxxxxxx>]

Check at http://www.tdasystems.com/Appnotes/diff1199.pdf

-Ray
Sun Microsystems Inc.

>
>
>Hi Allen,
>Do u have a url where I can directly go to the paper.
>Thanks,
>Rahul.
>--- Michael Allen <mallen@xxxxxxxxxxxxxxx> wrote:
>> 
>> Alexis,
>>      The odd mode impedance should be approximately
>> equal to half of
>> the differential impedance and the even mode should
>> be as high as
>> possible.  TDA systems has a very good paper on the
>> subject.
>> 
>> Mike Allen
>> Principal Engineer, Signal Integrity
>> TeraConnect, Inc
>> Nashua, NH
>> 
>> 
>> > -----Original Message-----
>> > From:      Alexis LESTRA [SMTP:alestra@xxxxxxxxxx]
>> > Sent:      Tuesday, June 12, 2001 11:58 AM
>> > To:        si-list@xxxxxxxxxxxxx
>> > Subject:   [SI-LIST] Even/Odd mode impedance
>> >=20
>> >=20
>> > Dear all,
>> >=20
>> > I am new in the field of signal integrity and
>> would like to submit a=20
>> > basic problem. I am currently designing a 
>> backplane for differential=20
>> > signals at 2.5  Gbit/s. The receiver is
>> differential, with 100 Ohm=20
>> > termination. For coupled transmission lines, which
>> characteristic=20
>> > impedance should match 50 Ohm, the even-mode
>> impedance or the
>> > even-mode=20
>> > impedance ? After reading some documentation on
>> the topic, I am=20
>> > confused. On one  hand, I read that differential
>> signals propagate in=20
>> > odd-mode since  coupled transmission lines are
>> driven with equel=20
>> > magnitude and 180=B0 out  of phase ("High-speed
>> Digital System =
>> Design",=20
>> > S.H. Hall, G.W. Hall, J.A.  McCall, p.53) . On the
>> other hand, I read=20
>> > that since differential  signals are launched from
>> silicon devices,
>> > the=20
>> > gates that driver these  signals are both
>> referenced to ground,=20
>> > resulting in even-mode coupling =20
>> > (http://www.amp.com/simulation/files/papers/98060A
>> 5.pdf   p.19).
>> > Can anyone help me to clarify this point.
>> >=20
>> > Thanks in advance.
>> >=20
>> > Alexis
>> >=20
>> > Alexis Lestra
>> > Tachys Technologies
>> > Les Algorithmes, Batiment Aristote A
>> > 2000, route des Lucioles
>> > F-06901 Sophia-Antipolis Cedex
>> >=20
>> >
>>
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>> >=20
>>
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