I'm pretty sure that's the opposite of true ;) -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Oh, Dan Sent: Friday, March 09, 2012 11:41 AM To: weirsi@xxxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Guard Traces Hi Steve and Doug, I also agree with you. You guys have one more vote. The guard trace is very effective to reduce the inductive coupling which cannot be easily reduced by spacing. Best, -Dan Oh -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of steve weir Sent: Thursday, March 08, 2012 9:23 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Guard Traces Doug, I agree that guard traces can help in certain situations. In most, and particularly when inserted without doing the requisite engineering work, they can make a good mess of things. Best Regards, Steve. On 3/8/2012 8:22 PM, Doug Smith wrote: > Hi Lee, > > Your statement is true for most cases, but for two layer boards (every > household has several of these with processors on them) guard traces > can stabilize impedance, improve grounding, and lower noise coupling. > I agree with you for advanced electronics. > > We should always state the assumptions made when citing design or > other rules. I see this a lot in EMC books where an equation is given > (such as slot radiation) but the (sometimes many) assumptions are not > given and people use the equations when they don't apply. Shielding > effectiveness is another case where the common equations do not apply > in many cases (far field conditions are assumed when in fact they are > not met). Under every equation in EMC and other books there should be > a list of assumptions given. > > Doug > > On 3/8/12 10:52 AM, Lee Ritchey wrote: >> With all the feedback on this forum that guard traces are a bad idea, why is >> this discussion still going on? Are there still people who cling to the >> notion that guard traces are useful, even in the face of mounting evidence >> that they don't help? >> >> >> -----Original Message----- >>> From: Dennis<dennis.han@xxxxxxxxx> >>> Sent: Mar 7, 2012 12:59 PM >>> To: si-list@xxxxxxxxxxxxx >>> Subject: [SI-LIST] Re: Guard Traces >>> >>> In addition to what Wolfgang has stated, if the guard traces are too close >>> to the signal traces, and most people who believe in ground traces put them >>> too close (ground fill also falls in this category), the impedance of the >>> signal traces is lowered and there are less crosstalk and radiation because >>> of it if the now mismatched terminations don't cause other problems. >>> >>> >>> >>> >>> >>> --- In si-list@xxxxxxxxxxxxxxx, Gwen and Wolfgang<gwmaichen@...> wrote: >>>> Hello, >>>> >>>> first, the short answer: simply don't use guard traces here, they >>>> won't help much with isolation of high speed signals, and they use >>>> up way too much routing space (on all layers, because of the >>>> stitching vias necessary). Much easier to just increase the >>>> distance between diff pairs etc. and you get the same benefit. (in >>>> fact, I suspect the reason many people believe in the magic power >>>> of guard traces in this setting - high speed signaling - is because >>>> those traces _force_ you to have enough space between signal >>>> lines...). Guard traces have their place in low-current / >>>> low-leakage / high-voltage applications, but NOT in high speed digital. At >>>> least that's my opinion. >>>> >>>> If you do need grounded traces, stitch them to the ground planes >>>> with vias spaced no further than a quarter wavelength from the >>>> signal trace and at an interval of no less than a quarter wave >>>> length from each other. The wavelength given of course by bandwidth >>>> connected with the signal rise time, BW = 0.33 / Tr, or a bit more >>>> conservatively, the knee frequency f_knee = 0.5 / Tr. No special >>>> termination needed at the ends of those traces because they are >>>> already solidly grounded along their full length. >>>> >>>> Wolfgang >>>> >>>> >>>> >>>> >>>> On 3/7/2012 7:31 PM, Aaditya Kandibanda wrote: >>>>> 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@... 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@... 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@... 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@... 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 >>> >>> >> 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 >> >> >> -- Steve Weir IPBLOX, LLC 150 N. Center St. #211 Reno, NV 89501 www.ipblox.com (775) 299-4236 Business (866) 675-4630 Toll-free (707) 780-1951 Fax All contents Copyright (c)2012 IPBLOX, LLC. All Rights Reserved. This e-mail may contain confidential material. 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