[SI-LIST] Re: Remove Ground underneath Differential signal is deserved or not?
From: yunnan <yunnan@xxxxxxxxxx>
To: scott@xxxxxxxxxxxxx <scott@xxxxxxxxxxxxx>
Date: Wed, 15 May 2002 16:44:56 +0800
Scott,
For what you say: ¡°In the same project I also was successfully able to extract
with a 2D field solver, simulate with Hspice and correlate to measurements, the
crosstalk isolation between two traces seperated by a 1/2 oz copper plane.
Through simulation we were able to determine that by using 1 oz copper we could
increase the crosstalk isolation by 10 dB.¡± you have mentioned the crosstalk
between two traces seperated by a plane, can you make a more detail
description? I am very interested in it.
Best regards,
Yun Nan
Senior Engineer
Wuhan Fiberhome Networks
yunnan@xxxxxxxxxx
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I've been able to successifully achieve better than -70 dB of crosstalk
isolation between multiple analog video signals using guard traces for
over 60 inches of total trace length. They do work quite nicely if vias
are used to ground the trace over regular intervals.
Not only did I have these results in Spice simulations. But also they
were subsequently confirmed by VNA measurements on the traces, within 1
dB of the simulated results. Without the guard traces, the crosstalk
was greater than 6 dB worse. In the same project I also was
successfully able to extract with a 2D field solver, simulate with
Hspice and correlate to measurements, the crosstalk isolation between
two traces seperated by a 1/2 oz copper plane. Through simulation we
were able to determine that by using 1 oz copper we could increase the
crosstalk isolation by 10 dB.
We utilized guard traces for several hundred single-ended and several
hundred differential traces on an analog video crosspoint switch.
Without the guard traces and stitch vias, we would not have been able
to meet our end-to-end crosstalk isolation requirement of -60 dB.
Best regards,
Scott
--
Scott McMorrow
Teraspeed Consulting Group LLC
2926 SE Yamhill St.
Portland, OR 97214
(503) 239-5536
http://www.teraspeed.com
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