Define a port across the two points where you want to determine the potential difference. Extract S11. Steve. On 6/2/2011 6:18 PM, Rajesh K wrote: > you are very much correct, one VDD or ten VDD doesn't matter. it all matters > potential difference. This is universal truth, we are not debating here this > point. The question is, how should I get or generate separate s-parameter > for VDD, VSS domain in a typical die, package, pcb connected system. This is > purely from simulation point of view. I wish to probe(in simulation) VSS > noise at different point in package, pcb, die input. if I use typical > s-parameter, VSS of package, pcb& die will be lumped together. Therefore, I > will not be able to estimate VSS noise at different point. > please do not expect to write new EM tool which will need to search for > equipotential point. suggest some solution within existing set of EM tools > available in market > On Fri, Jun 3, 2011 at 6:28 AM, steve weir<weirsi@xxxxxxxxxx> wrote: > >> ** >> One Vdd, or ten Vdd's, does not matter. AC and DC current will result in >> voltage potentials through interconnects. Vss at any two points on a die, >> PCB plane, or different planes in a stack-up will have different absolute >> potentials. The issue is: you need to understand what that potential >> difference is in reference to, or perhaps more importantly, what it is >> common to, and therefore whether it matters. If you were to probe a given >> signal or power rail, think about where would you ideally put the ground >> side of your scope probe, and why you would put it there. >> >> Steve. >> >> >> On 6/2/2011 5:11 PM, Rajesh K wrote: >> >> in a system with multi-voltage power rail, where VSS is common to all the >> power rails. any noise on VSS will impact system performance differently. >> you will get different results if you assume VSS quiet/noisy. separate >> s-parameters of power& VSS are highly desirable in such scenario. >> >> >> -- >> Thanks >> Rajesh >> >> >> >> -- >> Steve Weir >> IPBLOX, LLC >> 150 N. Center St. #211 >> Reno, NV 89501 www.ipblox.com >> >> (775) 299-4236 Business >> (866) 675-4630 Toll-free >> (707) 780-1951 Fax >> >> >> > -- Steve Weir IPBLOX, LLC 150 N. Center St. #211 Reno, NV 89501 www.ipblox.com (775) 299-4236 Business (866) 675-4630 Toll-free (707) 780-1951 Fax ------------------------------------------------------------------ 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 Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu