Personally I take it a step further and use guard traces for my guard traces. I find that gives me more guard traces. On really critical boards I might make a daughter card of guard traces and strap that to my main board. My next board is incredibly high performance so I'm thinking of making it out of only guard traces, removing all traces and components to make room for more of them. I expect it to perform admirably ;) -Eric -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Christopher.Jakubiec@xxxxxxxxxxxx Sent: Friday, May 25, 2012 12:50 PM To: doh@xxxxxxxxxx; bertsimonovich@xxxxxxxxxx; ken@xxxxxxxxxxxxxxxx; EMC-PSTC@xxxxxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Guard Traces - Use 'Em, or Not? So, physics aside let's ask the question how many people have chosen to implement guard traces into their designs as an optimal solution? Regards, Chris Infineon -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Oh, Dan Sent: Friday, May 25, 2012 9:35 AM To: bertsimonovich@xxxxxxxxxx; ken@xxxxxxxxxxxxxxxx; EMC-PSTC@xxxxxxxxxxxxxxxxx; 'SI-LIST' Subject: [SI-LIST] Re: Guard Traces - Use 'Em, or Not? Hi Bert, Thanks for great data and paper. We can finally discuss this issue over real data! As I have mentioned in the earlier posting, the guard trace effectiveness strongly depends on the trace height and spacing. The capacitive (electrical) coupling saving by placing the guard trace is pretty minimal as others pointed out. However, I believe the main advantage of the guard trace is reducing the inductive (magnetic) coupling which decays rather slowly than the capacitive coupling. The example you used only had 3mils height and 5mils spacing which makes the most of signal return through the ground plane rather than the guard trace. It is not surprising that you would not see much improvement in this case. If you increase the height, you will definitely see the improvement (say 15mils). Of course, this may not be a typical conventional microstrip configuration. The point I am trying to make is that let's not make a myth out of this guard trace. It is a simple physics. If the trace ground plane further away, use the guard trace (of course with proper stitching and impedance matching). Otherwise, don't. It would be nice if you can re-simulation your case with various heights. Best, -Dan Oh ___________________________________________ Dan (KyungSuk) Oh, Ph.D. Technical Director of Signal and Power Integrity Rambus Inc. (B) 408-462-8363 -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Lambert Simonovich Sent: Thursday, May 24, 2012 5:15 PM To: ken@xxxxxxxxxxxxxxxx; EMC-PSTC@xxxxxxxxxxxxxxxxx; 'SI-LIST' Subject: [SI-LIST] Re: Guard Traces - Use 'Em, or Not? Ken et al, Good blog post. I have been doing a little research myself; hopefully to put the subject to bed. I was putting the finishing touches on a white paper when you posted your link. Abstract: To guard or not to guard? That is the question often asked by digital hardware design engineers. As bit rates continue to climb, there is increased debate on whether to use guard traces to control crosstalk in high-speed digital signaling. By doing so, it is believed the guard trace will act as a shield between the aggressor and victim traces. On the other hand, the argument is that merely separating the victim trace to at least three times the line width from the aggressor is good enough. This paper studies the application of guard traces and quantifies the results against non guarded scenarios. Conclusions: This study has shown that adding a guard trace, at 3 times the line width, terminated at both ends with 50 Ohms, does little to improve crosstalk on the victim. In fact, in most cases, it was worse. The same was true when the guard trace was grounded only at each end. But adding a ground-stitched guard trace, with the same spacing, showed it was the best solution for microstrip, and had little to no benefit for stripline. However, by increasing the spacing to 5 times the line width in microstrip, the crosstalk, for all intensive purposes, was the same. In stripline, there was no benefit in adding a guard trace for digital signaling. You can download a copy from my website. Hope everyone finds it useful. Here is the link: http://bit.ly/KSM5BZ Best regards, Bert Simonovich, Consultant & Founder LAMSIM Enterprises Inc. "Innovative Signal Integrity and Backplane Solutions" Email: lsimonovich_at_lamsimenterprises.com Blog: http://blog.lamsimenterprises.com/ LinkedIN: http://www.linkedin.com/in/bertsimonovich Web Site: http://lamsimenterprises.com/ ======================================================= -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Ken Wyatt Sent: May-24-12 2:43 PM To: EMC-PSTC@xxxxxxxxxxxxxxxxx; SI-LIST Subject: [SI-LIST] Guard Traces - Use 'Em, or Not? Hi Group, After noticing the continued banter and discussions regarding guard traces in both the EMC and SI groups over the past months, I decided to consult a couple experts on the subject - Howard Johnson and Eric Bogatin. I summarized their thoughts in my latest blog posting on the Test & Measurement World web site: http://www.tmworld.com/blog/The_EMC_Blog/41806-Guard_Traces_Use_Em_or_Not_.p hp. I invited both to add any additional comment, if they wished. Feel free to add to the discussion. Cheers, Ken _______________________ Kenneth Wyatt Wyatt Technical Services LLC Woodland Park, CO Email Me! | Web Site | Blog Subscribe to Newsletter Connect with me on LinkedIn ------------------------------------------------------------------ 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 ------------------------------------------------------------------ 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 ------------------------------------------------------------------ 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