FreeLists / si-list / [SI-LIST] Re: Shielding clock traces on PCB's

["Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>]

Guard traces ar great ways to make accidental band pass filters.  Why would
anyone advise using them to control cross talk?  See any microwave
engineers' handbook on how to make bandpass filters by traces running in
parallel in the same layer.


> [Original Message]
> From: Salman Jiva <sjiva@xxxxxxxxxx>
> To: <william.coombs@xxxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
> Date: 1/2/2007 2:17:37 PM
> Subject: [SI-LIST] Re: Shielding clock traces on PCB's
>
> William,
>
> Crosstalk noise varies greatly with distance between traces as well as
> the height of the trace above the reference plane.  If you have already
> used sufficient separation between adjacent traces, you may not see much
> improvement from placing a guard trace in between.
>
> Refer to this article by Dr. Eric Bogatin for details
> http://www.altera.com/technology/signal/columns/2006/2006-10-oct_1.html
>
> Hope this helps,
>
> Salman Jiva
> Altera Corporation
> Technical Marketing Engineer
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Coombs, William B. (US SSA)
> Sent: Tuesday, January 02, 2007 11:03 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Shielding clock traces on PCB's
>
> =3D20
> Hello all,
>
> In regards to noise reduction, how effective do guard traces
> seem to be?
>
> Iv'e experimented with Hyperlynx by simulating my clock lines=3D20
> on the spectrum analyzer. These clock lines were simulated with=3D20
> and without grounded guard traces wrapped around the clock traces.=3D20
> The results showed little to no noise reduction with the addition
> of the guard traces.
>
> The clock lines & guard traces were routed on an internal layer in=3D20
> a dual-stripline Stackup.
>
> Thanks.
>
> William B. Coombs
> BAE Systems
> (973)636-7463
> Email:William.Coombs@xxxxxxxxxxxxxx
>
>
>
>
>
>
>
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