> And also on the other hand, I would assume that the Fourier > sum is actually limit process, the true square wave being the > limit of the asymptote. As such, the Fourier can't be looked > upon as a "real" thing. Doug: Agreed, but neither is the "true" square wave to which you refer a "real" thing. It is defined in the time domain as a limit as well -- both its infinitesimal risetime, and its periodicity defined over an infinite time interval. And if it did exist, we couldn't measure even one period precisely... All this to say, Fourier analysis is based on precise mathematical definitions, which precision is not available to us in the measurement world. In both the time and frequency domains, we are left to guess as to what lies in between the measurement samples, or outside the measurement window. However, measurable signals contain measurable Fourier components, to within the precision with which we are able to measure either one. I think this is basically what you stated in your post. To the mathematician, measurement of Fourier components is irrelevant in proving their existence. To the scientist, it implies existence until a better hypothesis comes along. To the engineer, it means food on the table next month. -- Steve ------------------------------------------- Steven D. Corey, Ph.D. Time Domain Analysis Systems, Inc. "The Interconnect Modeling Company." http://www.tdasystems.com email: steve@xxxxxxxxxxxxxx phone: (503) 246-2272 fax: (503) 246-2282 ------------------------------------------- Doug McKean wrote: > Lucien wrote: > >>Can anyone give me the low-down on square waves! Basically, my >>question is: In our physical reality, do square waves contain >>harmonics? Or does the idea of square wave harmonics only exist on >>paper as a mathematical model, used to PREDICT the natural behavior >>of the square wave? >> > > And also on the other hand, I would assume that the Fourier > sum is actually limit process, the true square wave being the > limit of the asymptote. As such, the Fourier can't be looked > upon as a "real" thing. -- ------------------------------------------------------------------ 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