is your s-parameter band limited? most likely this is due to different s-parameter extrapolation. Try to force the time step to be the same using .option delmax=<my_desired_max_timestep> if this works you atleast you should have consistent results. "correctness", that is whole another issue!! --- On Thu, 2/26/09, Lucian Zhang <zhanglub@xxxxxxxxxx> wrote: From: Lucian Zhang <zhanglub@xxxxxxxxxx> Subject: [SI-LIST] Ask help for s-parameter simulation To: si-list@xxxxxxxxxxxxx Date: Thursday, February 26, 2009, 5:14 AM Content-Type: text/plain; charset="US-ASCII" Dear all, In one of my simulation work, the Board parameter is extracted as S-parameter, include cupper, capacitors, inductors. The simulator is Hspice. The problem is, when the simulation time is set as 100ns or 1000ns, the waveform of the first 100ns is different a lot. Who can tell me that is why and how to adjust it? Thank you. ------------------------------------------------------------------ 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