There are several models for frequency dependance of Er, it depends on what type of material you are looking at. One model appropiate for FR4 is found in :- "Wideband Frequency-Domain Characterization of FR-4 and Time-Domain Causality" A Djordjevic, R Biljic, V Likar-Smiljanic, T Sarkar IEE Transactions on Electromagnetic Compatibility, November 2001 Regards John ryan.satrom@xxxxxxxxxxx wrote: > Thanks for your feedback. Sometimes, living in the simulation world, > you forget the real-world effects of boards. > > Lee: Is there any way to predict this frequency dependency of er? > > Fred: Is the frequency dependence of R and G caused by the same issues > Lee is discussing (dielectric constant over frequency)? Are there any > other causes of this? > > (As a side note, the equation suggests R and G to be fixed in > frequency, while L and C are the frequency dependent values. I guess > that's why the lumped element model breaks down and models are more > accurately viewed as distributed full-wave EM models) > > Thanks again for the comments. > > Ryan > > ------------------------------------------------------------------ > 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: > http://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: > http://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: http://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: http://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