Jeff, No, but if you transition through a plane that has no stitching or bypass with a via, you will surely see the resonance on the plane, some of which may be detected on the signal. A plane can have a resonant mode that is uninteresting until excited. When excited, it may radiate like the dickens. scott Loyer, Jeff wrote: >So, you would predict that:=20 >If I ran a trace on a 12" board and performed VNA on that trace, I >should expect to see a "resonance" at 250MHz. If I took that same trace >and ran it on a 24" board, I would see a resonance at 125MHz, and so on. >(note that this time I have F indirectly propotional with board size - >an oversight in my last posting). > >If this is the prediction, I am respectfully skeptical. > >And by the way, I didn't mean to imply that my experience in any other >field besides power delivery was UN-limited! That's only true for the >field of inducing errors in measurements and simulations. > >Jeff Loyer > >-----Original Message----- >From: steve weir [mailto:weirsp@xxxxxxxxxx]=20 >Sent: Wednesday, May 05, 2004 12:45 PM >To: Loyer, Jeff >Cc: si-list@xxxxxxxxxxxxx >Subject: RE: [SI-LIST] Re: Is a copper plane not tied to any net a >reference plane? > >Jeff, no, and I don't know where you get that idea. Lambda will be at=20 >about 1/500MHz, lambda/2 at 250MHz, and lambda/4 at about 125MHz. A Tr >of=20 >2ns has a knee at about 250MHz, which coincides with lambda/2. > >Regards, > > >Steve. >At 12:39 PM 5/5/2004 -0700, Loyer, Jeff wrote: > > >>If I understand you correctly, you predict that if I ran a trace on a >>12" board and performed VNA on that trace, I should expect to see a >>"resonance" at 100MHz. If I took that same trace and ran it on a 24" >>board, I would see a resonance at 200MHz, and so on. >> >>If this is the prediction, I am respectfully skeptical. >> >>If this isn't the prediction, could you articulate how the phenomenon >>would be reproduced, and how it would manifest itself? >> >>Perhaps you're talking about power distribution (where my experience is >>admittedly limited)? In that case, could you answer the same >> >> >questions? > > >>Thanks, >>Jeff Loyer >> >>-----Original Message----- >>From: steve weir [mailto:weirsp@xxxxxxxxxx] >>Sent: Wednesday, May 05, 2004 11:09 AM >>To: Loyer, Jeff >>Cc: si-list@xxxxxxxxxxxxx >>Subject: RE: [SI-LIST] Re: Is a copper plane not tied to any net a >>reference plane? >> >>Jeff, sure it is just the propagation velocity of the wavefront. A >> >> >12" > > >>board at Er of 4 is 2nS 1 way delay. The round trip directly aligns on >>a >>2nS Tr/Tf. >> >>Regards, >> >> >>Steve. >>At 07:25 AM 5/5/2004 -0700, Loyer, Jeff wrote: >> >> >>>Steve, >>>Could you clarify what you meant about "the half-wave resonance of a >>> >>> >>12" >> >> >>>board"? Do you mean to say that you think a 12" board (I assume >>> >>> >you're > > >>>talking about a height or width dimension) will be susceptible to >>>resonances at ~100MHz? If so, I'd like to understand that better. >>> >>> >>>Jeff Loyer >>> >>> >>>-----Original Message----- >>>From: si-list-bounce@xxxxxxxxxxxxx >>> >>> >>[mailto:si-list-bounce@xxxxxxxxxxxxx] >> >> >>>On Behalf Of steve weir >>>Sent: Tuesday, May 04, 2004 3:59 PM >>>To: ericsilist@xxxxxxxxx; si-list@xxxxxxxxxxxxx >>>Subject: [SI-LIST] Re: Is a copper plane not tied to any net a >>> >>> >>reference >> >> >>>plane? >>> >>>Eric, I believe Dr. Green provided a nice explanation for what >>> >>> >happens > > >>>to >>>the current in your trace. However, that is hardly the end of the >>>story. When you reference a signal, intentionally, or >>> >>> >unintentionally > > >>>against anything other than ground, you would be wise to consider >>> >>> >what > > >>>happens to that other reference. For your example case, it is pretty >>>close >>>to the half-wave resonance of a 12" board, resulting in efficient >>>broadcasts to Zontar and other points East. Resonant cavities >>> >>> >excited > > >>>with >>>substantial energy are generally not a good thing. >>> >>>Steve. >>>At 02:16 PM 5/4/2004 -0700, eric steimle wrote: >>> >>> >>>>I'm trying to settle an argument without saying which >>>>side I'm on, and I was hoping someone could give a >>>>quick and easy example to prove this. >>>> >>>>You have a four layer board that looked like this >>>> >>>>SIG1 >>>>GND >>>>VCC >>>>SIG2 >>>> >>>>And the maximum rise time on the board was about 2ns >>>>(say a 100MHz clock), then if I ran a trace from one >>>>IC to another on SIG1 the return current would flow >>>>along the GND plane (assuming no splits in the plane >>>>etc.) >>>> >>>>What if I covered SIG1 with a plane of copper say >>>>hovering 5 mil above SIG1, and then made the distance >>>>between SIG1 and GND 100mil so.. >>>> >>>>Plane sheet of Copper >>>>5 mil of air >>>>SIG1 >>>>100 mil FR4 >>>>GND >>>>VCC >>>>SIG2 >>>> >>>>Now that plane sheet is not GND and it has no >>>>association to any net it is just a continuous sheet >>>>of copper about the size of the board. One of us >>>>argues that the return current will continue to flow >>>>along the GND plane as it did before. The other >>>>argues that the return current will instead flow >>>>mostly along that sheet of copper unitl it jumps back >>>>to the GND plane as it gets closer to the IC. Any >>>>help in this would be much appreciated. >>>> >>>>Thanks >>>> >>>> >>>> >>>> >>>> >>>>__________________________________ >>>>Do you Yahoo!? >>>>Win a $20,000 Career Makeover at Yahoo! HotJobs >>>>http://hotjobs.sweepstakes.yahoo.com/careermakeover >>>>------------------------------------------------------------------ >>>>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 FAQ wiki page is located at: >>>> http://si-list.org/wiki/wiki.pl?Si-List_FAQ >>>> >>>>List technical documents are available at: >>>> http://www.si-list.org >>>> >>>>List archives are viewable at: >>>> //www.freelists.org/archives/si-list >>>>or at our remote archives: >>>> http://groups.yahoo.com/group/si-list/messages >>>>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 FAQ wiki page is located at: >>> http://si-list.org/wiki/wiki.pl?Si-List_FAQ >>> >>>List technical documents are available at: >>> http://www.si-list.org >>> >>>List archives are viewable at: >>> //www.freelists.org/archives/si-list >>>or at our remote archives: >>> http://groups.yahoo.com/group/si-list/messages >>>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 FAQ wiki page is located at: > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > >List technical documents are available at: > http://www.si-list.org > >List archives are viewable at: > //www.freelists.org/archives/si-list >or at our remote archives: > http://groups.yahoo.com/group/si-list/messages >Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > > > > -- Scott McMorrow Teraspeed Consulting Group LLC 2926 SE Yamhill St. Portland, OR 97214 (503) 239-5536 http://www.teraspeed.com Teraspeed is the registered service mark of Teraspeed Consulting Group LLC ------------------------------------------------------------------ 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 FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu