Jenifer, In addition to all the good advice you have received so far from experts in the field, I would like to suggest that if none of the tools mentioned are able to solve you causality issue you may ultimately "manually" build an RLC Spice model from the s-parameters frequency sweep simulations. This model will not be so accurate like the broadband spice models, but at least it will give you something to work with. I have attached an example of RLC model built from s-param simulation (file: s_param_rlc_model.tif), where you can see also the error between the RLC model and the s-param simulation. The "C" values are calculated from the "DOWN" slopes, "L" values from "UP" slopes or resonant peaks, and "R" form minimums of the resonant peaks, as shown in the figure. Contact me if you need more details. Cosmin Iorga, Ph.D. NoiseCoupling.com http://www.noisecoupling.com ________________________________ From: Jennifer Maharani <jennifer.maharani@xxxxxxxxx> To: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx> Sent: Thursday, May 14, 2009 12:48:44 PM Subject: [SI-LIST] Causality Dear all, I have non-passive non-causal S-parameter. I can use some commercial tools that can generate broadband spice with passivity enforcement. Not with causality enforcement, though. In transient simulation it clearly shows non-causal response. Does anybody know how to resolve this issue? Quick and dirty solution will also be appreciated. Many thanks. ------------------------------------------------------------------ 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 ------------------------------------------------------------------ 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