Hi, To simplify the model, we often extract single RLGC parameters from the s-parameter model at a certain frequency. I wonder what on earth the meaning of the single frequency parameters is. First, if the parameters only represent the magnitude and phase of the S-parameter model at the frequency point, it may have different combinations of RLGC to reach the same goal, what's the method or principle? Second, if the parameters are meaningful at a certain frequency, why can single RLGC parameters often be used to estimate characteristic of package model such as IBIS? In my opinion, for example, the single RLGC model should be the first-order approximation to the real model for transmission line, as Eric's book 'Signal Integrity: Simplified' said. It is equivalent to the real model within low frequency range and we can use it if the signal frequency component is within the range. However, if the RLGC model extracted at a certain frequency is only meaningful for the extracting frequency, it isn't the first-order approximation for the transmission line. So we can't use it as the first-order approximation and estimate its low frequency characteristic. Appreciate any idea and discussion for the problem. Best Regards, Zhengrong ------------------------------------------------------------------ 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 technical documents are available at: http://www.si-list.net 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