Pehr, You can find a description or the modal aspects of crosstalk in chapter 11 of Eric Bogatin's book. I always think of FEXT in terms of modes. In a lossless microstrip, when you put a pulse on one line next a quiet line, at the far end of the quiet line you get a short negative going pulse. This pulse is defined by the velocity differences of the odd and even modes. The first negative excursion represents the arrival of the odd mode component. This will continue to go negative until the arrival of the even mode component when it will begin to go positive till it returns to the 0 level. The odd mode arrives earlier because there is more air in the cross-section that the fields are exposed to; the even mode see less air and consequently sees a higher effective dielectric constant. Since all of the modes in a lossless stripline see the same effective dielectric constant, they all travel at the same velocity and arrive at the same time. John Ellis Principal Engineer Mixed Signals & I/O Libraries Group Synopsys, Inc. email: jellis@xxxxxxxxxxxx Phone: 508.263.8194 -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Pehr Andersson Sent: Monday, April 23, 2012 10:32 AM To: Wolfgang.Maichen@xxxxxxxxxxxx Cc: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Design rules for estimating crosstalk Thanks Wolfgang! How accurate are the equations that are used for crosstalk analysis and that are based on circuit analysis? For example with those equations we cannot explain why FEXT = 0 in striplines (theoretically) What are other alternatives, I have read that modal analysis could be used to accurately model crosstalk, but I couldn't find any explanation what it is. Best regards, Pehr 2012/4/23 <Wolfgang.Maichen@xxxxxxxxxxxx> > Hello Pehr, > > actually crosstalk for striplines decreases exponentially, i.e. > exp(-d/const.). This means beyond a certain distance it drops off much > faster than the 1/d^4 you assumed. > > NEXT increases linearly with coupling length for coupled sections with > a round trip delay shorter than the signal rise time (this is why in > the past people assumed ANY crosstalk - NEXT and FEXT - would increase > linearly with coupled length, because rise times were cery long). Only > for lines longer than that there is the plateau in the NEXT. > > Regards, > > Wolfgang > > ------------------------------------------------------------------ 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