Hello, I donot know if this answers your question...but just a piece of information...the fourier coefficients of a trapezoidal wave comprises of product of three terms. 1. (tau+tr)/T 2. sinc(n*pi*tr/T) 3. sinc{n*pi*(tr+tau)/T} where tau is the high time, tr is the rise time ( or fall time) and T is the period. For tau>>t1, till Frequency 1/tr, the 2nd sinc pulse decays slowly, hence 20dB / decade attenuation due to 3rd sinc pulse.....beyound this knee frequency both the sinc terms act and hence 40dB/decade attenuation..... Hope this helps. Sincerely Himanshu Arora PhD student, Duke University, Durham, NC. --- Tom Dagostino <tom@xxxxxxxxxxxxx> wrote: > > If I remember correctly, and its been over 20 years > since I've seen this, > but a 2 pole Gaussian low pass filter that is > critically damped is the basis > for this number. That is the response that scope > designers were trying to > design to. > > Tom Dagostino > Teraspeed Consulting Group LLC Teraspeed > Consulting Group LLC > 2926 SE Yamhill St. Device Modeling > Division > Portland, OR 97214 13610 SW Harness > Lane > Beaverton, OR > 97008 > http://www.teraspeed.com 503-430-1065 > tom@xxxxxxxxxxxxx > > > -----Original Message----- > From: si-list-bounce@xxxxxxxxxxxxx > [mailto:si-list-bounce@xxxxxxxxxxxxx]On > Behalf Of Keskinen, Kai > Sent: Tuesday, May 20, 2003 9:24 AM > To: si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] Re: Interconnect Simulations-V2 > > > > If you work out the amplitude of the harmonics of an > infinitely repeating > trapesoidal waveform with equal rising and falling > edges, you find that the > harmonics on a log-log plot fall at 20dB per decade > until you reach > 1/(pi*Tr) ~ 0.318/Tr . After that knee frequency, > they fall at 40dB per > decade. Most of the significant harmonics are > present to the knee frequency. > Clayton Paul's book on EMC has both measurements and > the derivation for > those who last did a fourier analysis in undergrad. > Does anyone know where > the 0.35 number can be derived from? > > Cheers, > > Kai Keskinen > Signal Integrity Advisor > Solectron Technical Center > 21 Richardson Side Road, > Kanata, ON K2K 2C1 > <mailto:kaikeskinen@xxxxxxxxxxxxx> > <http://www.solectron.com/> > "This message may contain information proprietary to > Solectron so any > unauthorized disclosure, copying or distribution of > its contents is strictly > prohibited." > ------------------------------------------------------------------ > 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 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 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 > > __________________________________ Do you Yahoo!? The New Yahoo! Search - Faster. Easier. Bingo. http://search.yahoo.com ------------------------------------------------------------------ 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 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