Gert Just one "slight" correction. Crosstalk between traces is matter of distance. Crosstalk between vias may not be, and quite likely is not in a real design. Poor localization of structures (i.e. - bad use of ground vias) can cause very interesting crosstalk results. Scott Scott McMorrow Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 (401) 284-1827 Business (401) 284-1840 Fax http://www.teraspeed.com Teraspeed® is the registered service mark of Teraspeed Consulting Group LLC On 1/6/2012 4:19 AM, Havermann, Gert wrote: > Yes, x-talk is a matter of distance, and yes, talking about distance without > relation to the tracewidth isn't accurate. That's why I also stated a > distance in factors of tracewidth (the tracewidth is always related to the > reference plane distance). There are quite good rules of thumb:>5x tracewidth > distance between differentialtraces "removes crosstak" This works fine for > most applications. > > I don't like using Microstrip for Datarates exceeding 6GBps, but in some > cases it is absolutely ok (and even better than stripline). If you have very > short traces, Microstrip is better because you don't need to worry about via > stub effects and reflections. The longer the trace, the more preferable it is > to route it as stripline. Crosstalk and EMI are other factors to prefer > stripline. > > BR > Gert > > > ---------------------------------------- > Absender ist HARTING Electronics GmbH& Co. KG; Sitz der Gesellschaft: > Espelkamp; Registergericht: Bad Oeynhausen; Register-Nr.: HRA 5596; > persönlich haftende Gesellschafterin: HARTING Electronics Management GmbH; > Sitz der Komplementär-GmbH: Espelkamp; Registergericht der Komplementär-GmbH: > Bad Oeynhausen; Register-Nr. der Komplementär-GmbH: HRB 8808; > Geschäftsführer: Edgar-Peter Duening, Torsten Ratzmann, Dr. Alexander Rost > > -----Ursprüngliche Nachricht----- > Von: Pehr Andersson [mailto:andersson.pehr@xxxxxxxxx] > Gesendet: Donnerstag, 5. Januar 2012 19:48 > An: Havermann, Gert > Cc: si-list@xxxxxxxxxxxxx; Rick Brooks (ricbrook) > Betreff: Re: [SI-LIST] Re: Reduction of crosstalk by using stitching vias > between traces > > If we have in between differential traces, a single trace and stitch that one > with thru hole vias connecting reference planes, then it's a guard trace, how > much reduction in crosstalk could we then expect? > > Also how wide should this single "guard trace" be, if the drill hole diameter > of my stitching vias are 10 mils, is it OK if the trace is> > 12 mils wide? (The gap is 30 mils wide) > > So basically if I understood correctly only means we have for reduction of > crosstalk is to increase the spacing between the pairs and also how close are > the traces to the reference planes also affects crosstalk, but closeness to > reference plane isn't something that I could change, since then the > differential impedance changes, and I have to use smaller traces, which could > be problematic from manufacturing point of view? Thinner traces will be more > susceptible to impedance variations. > > Is it recommendable to use microstrip traces for high-speed signaling where > data rate is> 10Gb/s? > > Since stripline is what is usually seen for high-speed Ethernet (10GBase-KR) > > Thanks and best regards! //Pelle > > > >> 2012/1/5, Havermann, Gert<Gert.Havermann@xxxxxxxxxxx>: >> Pelle, >> >> the effect is minimal. I'd guess, that you will reduce the x-talk of >> the microstrip by 2%, and the stripline by 1% (attention: I'm talking >> about total reduction. I'm not saying stitching brings you down to 1% >> x-talk!!!). >> >> Just for reference, 4 mil of additional separation between the >> differential pairs gives you approx, 5-10dB lower crosstalk (5dB >> microstrip, 10dB stripline depending on the topology). Having a >> separation of>3x the tracewidth in stripline already gives you approx 30dB >> isolation (2% x-talk). >> >> Distance is much more effective for isolation than stitching vias. >> >> BR >> Gert > ------------------------------------------------------------------ > 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 technical documents are available at: > http://www.si-list.net > > 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 technical documents are available at: http://www.si-list.net 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