[SI-LIST] Re: Remove Ground underneath Differential signal isdeserved or not?
- From: "Perry Qu" <Perry.Qu@xxxxxxxxxxx>
- To: scott@xxxxxxxxxxxxx
- Date: 31 Jul 2002 15:05:13 -0400
Scott:
I find your recommendation on "random interval" via stitching interesting.
This can be applied not only on guard trace but other cases when we need to do
via stitchings. I call it a "spread spectrum" technique, as we reduce the
peak amplitude of one sharp resonance and spread the energy a little bit.
Regards
Perry
Scott McMorrow wrote:
> Lee,
>
> > What I show in my class is that guard traces are always LC networks that
> > resonate at some frequency and can and do turn into bandpass filters
> > at some
> > frequencies. I demonstrate this will actual failed circuits.
> >
> >
> This is exactly why Mike Conn and myself recommend stitching guard
> traces to ground at random intervals across the length. The average
> spacing of the via sites should be 1/10 of the wavelength of the fast
> signal frequency or equivalent risetime that will be present on this
> trace. These stitch vias to ground will eliminate the problems which
> you have alluded to. They are backed by extremely good analytical and
> experimental science.
>
> Best regards,
>
> Scott
>
> --
> Scott McMorrow
> Teraspeed Consulting Group LLC
> 2926 SE Yamhill St.
> Portland, OR 97214
> (503) 239-5536
> http://www.teraspeed.com
>
> --
> Scott McMorrow
> Teraspeed Consulting Group LLC
> 2926 SE Yamhill St.
> Portland, OR 97214
> (503) 239-5536
> http://www.teraspeed.com
>
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--
Perry Qu
Product Integrity | 600 March Road
Alcatel Canada | Ottawa, ON K2K 2E6, Canada
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