So when I was a younger engineer someone (Johnson maybe) put me on to this simple experiment I did in the lab when I was trying to convince my bosses at the time that coupling in our system was really mostly inductive and not capacitive. With a little modification you can also use it to get a feel for how well or not well a guard trace works. All you need is a Pulse generator, or some kind of square wave in the Mhz range, some wire, a piece of copper clad PCB and some resistors. Oh and motivation to go into the lab. Anyway take your piece of copper clad and put these two wires over the top like this, and make sure to GND the top of the copper with the GND cable from the coax. Aggressor (tape this down) Pulse Generator----50 Ohm coax (BNC cable) --- 3” of Regular wire ---- R1 50 Ohm Resistor to GND Victim GND -------------------------------------3” of Regular wire ---- R2 50 Ohm To GND It’s kind of cool, if you move the victim 3” of wire closer or further from the aggressor you’ll see the cross talk voltage go up and down when measured at R2. Then if you want, get yourself another wire to use as a guard trace in between the Aggressor and Victim. Just ground it at both ends and you’ll see the difference it makes (which should be pretty tiny), or go crazy and ground it everywhere. Just remember to keep the spacing between the Aggressor and Victim the same in this part of the experiment or you’ll end up fooling yourself ;) This isn't going to tell you what to do in your system but it's a neat way to get your head around the problem. Good Luck, -Eric -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Lee Ritchey Sent: Wednesday, March 07, 2012 1:48 PM To: aaditya.kandibanda@xxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Guard Traces Short answer- Don't use guard traces! Use separation to isolate signals from each other. -----Original Message----- >From: Aaditya Kandibanda <aaditya.kandibanda@xxxxxxxxx> >Sent: Mar 7, 2012 10:31 AM >To: si-list@xxxxxxxxxxxxx >Subject: [SI-LIST] Guard Traces > >Hello Everyone, >I have few questions about the guard traces. > >1. How do I terminate the guard traces? >2. While using the guard traces for differential pair, how shall I >place them between the differential pair? >3. How should I place the vias for guard traces? >4. What are disadvantages of Guard traces? > >Thanks and regards >Aaditya > > >------------------------------------------------------------------ >To unsubscribe from si-list: >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > >or to administer your membership from a web page, go to: >//www.freelists.org/webpage/si-list > >For help: >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > >List forum is accessible at: > http://tech.groups.yahoo.com/group/si-list > >List archives are viewable at: > //www.freelists.org/archives/si-list > >Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > > I just used the energy it took to get mad and wrote some blues. Count Basie Lee W. Ritchey Speeding Edge P.O. Box 2194 Glen Ellen, CA 707-568-3983 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List forum is accessible at: http://tech.groups.yahoo.com/group/si-list List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List forum is accessible at: http://tech.groups.yahoo.com/group/si-list List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu