The problem with conductivity is that it scales with frequency. Your 2.5Gbit signal has frequency components from zero to 1/(PI *rise time). In Ansoft SI2D (I am assuming this is the field solver you are using) the problem is, that you can not define functions with frequency dependent variables. I ended up to define conductivity and permittivity of FR4 as constant variables and swept the value of them in 31 individual setups vs. frequency. This will provide you with 31 simulation runs, each at a specific frequency, using the correct conductivity and permittivity. The results of this can than be extracted and converted into a tabular W Element for Hspice. It would be much easier if Ansoft would allow the definition of loss tangent rather than conductivity for dielectrics. Also the definition of frequency dependent variables (like conductivity) would simplify the effort a lot. cheers Joachim -- - -- Joachim Mueller EMC/SI-Engineer, W.L.Gore & Associates Nordring 1 91785 Pleinfeld Germany Phone: +49 9144 6016368 Email: joachim_mueller@xxxxxxxxxx Alfredo.Moncayo@in fineon.com To: si-list@xxxxxxxxxxxxx Sent by: cc: si-list-bounce@fre Subject: [SI-LIST] Re: Conductivity for FR4 elists.org 06.11.01 23:43 Please respond to Alfredo.Moncayo That has worked well for me. I haven't methodically gone through and determined the effect of the frequency term in the end result, but so far have achieved very good correlation when using 3x the base rate of the signal that would be used on the interconnect. Alfredo > -----Original Message----- > From: Khalid Ansari [mailto:khalida@xxxxxxxxxxx] > Sent: Tuesday, November 06, 2001 10:44 AM > To: si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] Conductivity for FR4 > > > > Hi all, > > I am using a 2D field solver to extract the RLGC parameters for a > stripline differential pair. When defining FR4 it asks me for the > conductivity of the material. I looked up the loss tangent for FR4, > which is .02 (around 2.5 Gbps). Can I use the formula: > Loss tangent = conductivity/(2*pi*f*EoEr) and get the appropriate > conductivity value for the field solver, or do I need to worry about > something else. > > Thanks, > Khalid > > ------------------------------------------------------------------ ------------------------------------------------------------------ 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