Doug A very good point, indeed. Scott Scott McMorrow Teraspeed® Consulting - A Division of Samtec 16 Stormy Brook Rd Falmouth, ME 04105 (401) 284-1827 Business http://www.teraspeed.com On Wed, Oct 22, 2014 at 11:07 AM, emceed <doug@xxxxxxxxxx> wrote: > One problem to remember, the amount of energy extracted from a signal to > cause an EMC emissions problem is often so low that the effect on SI is > insignificant. So EMC simulations and measurements are in order. I present > live experiments in my seminars to illustrate this effect, very easy to set > up an experiment to show this right on a table top, no chamber needed! > > Doug Smith > Sent from my iPhone > iPhone: 408-858-4528 > Office: 702-570-6108 > Email: doug@xxxxxxxxxx > Website: http://dsmith.org > > > > On Oct 22, 2014, at 05:44, Loyer, Jeff <jeff.loyer@xxxxxxxxx> wrote: > > > > At the risk of finding myself embroiled in a furball, I thought I'd see > if I could clear up (in my own mind anyway) some of the effects of ground > vias. I ran 3-D simulations on a pair of single-ended signal vias with > various configurations of ground vias around them and compared impedance, > NEXT, and FEXT. The results strongly suggest that nearby ground vias are a > good investment to reduce via crosstalk. Of course, if you can absorb the > extra crosstalk, it's a moot point. And ground vias are often hard to put > where we want them, since they impede routing on every layer, so we seldom > have the luxury of all the vias we might like (the "no xtalk" configuration > in the study). > > Here's a link to the study. > > https://www.filesanywhere.com/fs/v.aspx?vâ¹6e658761616dab72a2 > > > > Note: I'm leaving the presentation a bit vague (leaving out any > conclusions, many exact dimensions, and not stipulating simulation > assumptions) on purpose - this should not be regarded as any formal > "report-out". It's only a "quick-and-dirty" peek at the issue. Others may > duplicate the simulation with different results, though that seems > improbable - I don't see anything leading me to believe they are > fundamentally flawed. They are not overly complex topologies, so I invite > others to replicate the simulations if the results seem questionable. > > > > And, of course, exact results will depend on design specifics (stackups, > via dimensions, etc.). Your mileage may vary... > > > > Cheers, > > Jeff Loyer > > > > > > ------------------------------------------------------------------ > > 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