[SI-LIST] Re: ??: NEXT and FEXT: Question on relative levels

  • From: <Aubrey_Sparkman@xxxxxxxx>
  • To: <chengyuming_ah@xxxxxxxxxxxx>, <Charles.Grasso@xxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
  • Date: Wed, 30 Nov 2005 10:05:26 -0600

Let's be a little more clear about the situation we are discussing.  For =
stripline I would expect (due to cancellation) NEXT to be greater than =
FEXT.

BUT!

Charles asked about two MICROSTRIP traces.  Anyone want to claim the =
inductive and capacitive coupling for microstrip traces is sufficiently =
balanced for cancellation to apply?

Aubrey Sparkman=20
Enterprise Engineering Signal Integrity Team
Dell, Inc.=20
Aubrey_Sparkman@xxxxxxxx=20
(512) 723-3592

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
On Behalf Of Yuming Cheng
Sent: Tuesday, November 29, 2005 11:29 PM
To: Charles.Grasso@xxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] ??: NEXT and FEXT: Question on relative levels

Hello Charles,

From figure 3.2 of "High-Speed Digital System Design=A1=AAA Handbook of =
Interconnect Theory and Design Practices", you can find that the =
inductive and capacitive crosstalk cancel at far end and reinforce at =
near end.

You can also get this from section 5.7.1-5.7.3 in "High-speed digital =
design, Dr. Johnson".
 =20
So it's possible to have NEXT greater than FEXT.

B.R.
Astrom

--- "Grasso, Charles"
<Charles.Grasso@xxxxxxxxxxxx>=D0=B4=B5=C0:

> Is it possible to have NEXT greater than FEXT.??
> =20
>=20
> For example: For a two trace microstrip system my simulator reports=20
> 10% NEXT (so for a 2.5V signal that translates to 250mV).
>=20
> Based on the reported mutuals and self numbers and using the formula=20
> in Eric's book I estimate 60mV for FEXT.
>=20
> =20
>=20
> Is this reasonable?
>=20
> =20
>=20
> Best Regards
> Charles Grasso
> Senior Compliance Engineer
> Echostar Communications Corp.
> Tel: 303-706-5467
> Fax: 303-799-6222
> Cell: 303-204-2974
> Pager/Short Message: 3032042974@xxxxxxxx
> Email: charles.grasso@xxxxxxxxxxxx;
> Email Alternate: chasgrasso@xxxxxxxx
>=20
> =20
>=20
>=20
>
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