hello SI-list, concerning the question on rational function approximation you could check the following article: Rational approximation of frequency domain responses by vector fitting Bjorn gustavsen, Adam Semlyen, IEEE trans on Power Delivery, vol 14, nr 3, July 1999 There are several other articles from these authors on this subject. Another one is: A general procedure for the extraction of Lumped-Equivalent circuits from Full-wave electromagnetic simulations of interconnect discontinuities R. Araneo, S. Celozzi 2003(?) Symphosium on EMC, Zurich I think this article has also made it to the IEEE MTT. I also have used a demo version from http://www.emwonder.com/ to model ferrite beads with very good results and ceramic decoupling capacitors with not so good results. Kind regards, Jan vercammen ------------------------------------------------------------------ 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 FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org 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