Hi Ritchy, Are you indicating that my explanation is valid if we stay with the circuit concept? Maybe I am missing radiation impact here which I do not have much experience so I will take your words. I will try to continue this thread offline since it may not be interested to others. Best, -Dan Oh -----Original Message----- From: Lee Ritchey [mailto:leeritchey@xxxxxxxxxxxxx] Sent: Friday, March 09, 2012 8:58 AM To: Oh, Dan; weirsi@xxxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: Re: [SI-LIST] Re: Guard Traces Dan, it's basic physics. You need to cease looking at the problem in terms of current loops and start looking at it as fields and waves. -----Original Message----- >From: "Oh, Dan" <doh@xxxxxxxxxx> >Sent: Mar 9, 2012 8:52 AM >To: Lee Ritchey <leeritchey@xxxxxxxxxxxxx>, "weirsi@xxxxxxxxxx" ><weirsi@xxxxxxxxxx>, "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx> >Subject: [SI-LIST] Re: Guard Traces > >Hi Ritchey, >Perhaps, you can elaborate why??? >The reason why we placed ground guards closer to the signal is to reduce the >current loop (assuming they are sufficiently stitched). This will reduce >coupling from other current loops (which is also small). Of course, this >depends on the height of trace which I assumed is fairly large compare to >spacing. Otherwise, it would not help as you indicated. >So, the answer would be depends. But I want to make sure when the trace is >located high; then, the ground guard is a very effective way to mitigate this. >May I am missing something here and need your lecture here. >Best, >-Dan Oh >-----Original Message----- >From: Lee Ritchey [mailto:leeritchey@xxxxxxxxxxxxx] >Sent: Friday, March 09, 2012 8:46 AM >To: Oh, Dan; weirsi@xxxxxxxxxx; si-list@xxxxxxxxxxxxx >Subject: Re: [SI-LIST] Re: Guard Traces > >Inductive coupling is precisely what guard traces cannot block. If they could >we would not have motors and transformers or bandpass filters in microwave >applications. > > >-----Original Message----- >>From: "Oh, Dan" <doh@xxxxxxxxxx> >>Sent: Mar 9, 2012 8:40 AM >>To: "weirsi@xxxxxxxxxx" <weirsi@xxxxxxxxxx>, "si-list@xxxxxxxxxxxxx" >><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. >>If you are not the intended recipient, please destroy all records and notify >>the sender. >> >>------------------------------------------------------------------ >>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 >> >> > > >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 > > 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