Bratfest, The explanation you have was pretty much the direction I was thinking in. I assumed that since a processor on an integrated circuit die can switch in a very large number of permutations, the common practise was to either take a worst case estimate, or some kind of approximation. But I guess it makes sense to conduct a transient analysis to get more accurate values. Thanks for the info :) Ihsan, Thanks for clearing out what Spectre meant by using convolution with regards to their S-parameter data. I was under the impression they were doing an IFFT, which didn't make sense. I kept thinking that they were somehow including the frequency response/IFFT by adding extra equations into the newton-rhapson/integration formula of the transient solver. Sincerely, ------------------- Taha Amiralli thamiral [A] uwo [D] ca thamiral [A] gmail [D] com MESc Candidate 2007, Computer Engineering The University Of Western Ontario BESc, BSc. 2005, Computer Engineering & Computer Science The University Of Western Ontario --------------------------------------------------------------- On 12/4/06, Ihsan Erdin <erdinih@xxxxxxxxx> wrote: > > Taha, > > Spectre (or any circuit simulator that uses a time evolution > technique) fails because its iterative algorithm builds the error in > the S-parameter data at every time step. If the data is unstable the > result shoots to the sky, if non-passive, it oscillates. The > convolution they mention is an intermediate step to get the > s-parameter data into the admittance matrix. Keep in mind that the > original frequency domain data can't be directly included in the > simulator's time domain algorithm. The data is first approximated in a > rational form and then expanded in decaying exponentials, which saves > storage and computational time by recursive convolution. But the end > result is still obtained by marching in the time, hence the passivity > requirements. > For the analysis of power delivery systems, I don't really see a big > incentive to use a transient simulator as long as the linear load > assumption holds. This applies to most practical cases. Usually the > frequency domain solution will give enough information for the > decoupling efficiency etc. A time domain response may be desired just > to see the peak-to-peak noise level but then one can easily get it > through IFFT as you put it. > > Regards > > Ihsan > > > On 12/4/06, Taha Amiralli <thamiral@xxxxxxxxx> wrote: > > Ihsan, > > Your comments are definitely correct. No matter how bad the S-parameter > > matrices are, with respect to passivity/causality, you will still get a > > frequency response and thus, an IFFT should do the trick. > > > > The thing is that I have read that spectre does use convolution when > > computing the time domain response from S-parameter matrices. So I guess > the > > question then becomes, why would spectre fail to compute the transient > > response of a non passive S-parameter dataset, as is the case with > Madhu? > > > > Bratfest, > > > > I definitely did not consider all those options... but I am still not > sure > > why a transient response would be required... If the design is lets say > an > > Integrated circuit, with lots of different loads, wouldn't it suffice to > > just find out what the max power levels required are and provide a power > > supply that is suited to the task? I guess I am still unsure of how a > > transient analysis would apply since the loading conditions are > different > > depending on what the integrated circuit is doing at a certain moment in > > time. > > > > Thanks, > > > > Sincerely, > > > > Taha > > > > > > > > On 12/3/06, Dmitriev-Zdorov, Vladimir < > vladimir_dmitriev-zdorov@xxxxxxxxxx> > > wrote: > > > > > > > > > Hi Madhu, > > > > > > We do have a tool that can solve the problem you describe, unless your > > > original touchstone files are of an extremely bad quality (in terms of > > > resolution, causality, passivity etc.) For example, if instead of > having > > > L2 norm of the matrix below one, it reaches 1.1...1.5, it is possible > to > > > make the model passive without changing the dependences too much. > > > However, if the norm goes up to hundreds, this is less likely. > > > > > > Anyway, we may produce either passive/causal/smooth data in a form of > > > the touchstone file, re-sampled with sufficient resolution, or, in a > > > form of an equivalent SPICE-compatible circuit, whichever you prefer. > > > > > > Please contact off-line for more technical details. > > > > > > Vladimir > > > > > > > > > > > > ------------------------------ > > > > > > Msg: #5 in digest > > > Date: Sat, 02 Dec 2006 00:16:01 -0500 > > > From: Madhusudanan K Sampath <mkeezhve@xxxxxx> > > > Subject: [SI-LIST] Spectre S-parameter based modeling- Stability > issues > > > > > > Hi All,=20 > > > I am using n-port component in spectre to perform time domain > simulation > > > using touchstone s-parameter files for power planes which are obtained > > > from > > > measurement/full wave tools. In many cases, the simulation explodes > due > > > to > > > stability reasons. What are the possible causes of this and how can > one > > > solve this issue. I think Spectre n-port component uses convolution > > > methods > > > to perform time domain simulation from frequency domain s-parameter > data > > > and > > > hence are prone to convergence issues. If so how does it enforce > > > passivity > > > in the model. I verified the s-parameter matrix for eigenvalues and it > > > proves the data is not passive. I would like to compensate for > passivity > > > and > > > then re-try the time domain simulation. There are quite a few > > > interesting > > > passivity enforcements techniques in literature by Dr. B. Gustavsen > and > > > Dr > > > S.G. Talocia . However they are applied on the rational functions > which > > > are > > > obtained by vector fitting the data. My question is if I vector fit > the > > > data, enforce the passivity using these techniques and then calculate > > > the > > > S-parameter matrix for each frequency point from the passive rational > > > function model. Will spectre give stable results with this new data > ?=20 > > > > > > Please share your ideas and views on this. Thanks in advance.=20 > > > > > > Madhu=20 > > > > > > =20 > > > > > > > > > > > > > > > ------------------------------ > > > > > > End of si-list Digest V6 #422 > > > ***************************** > > > > > > ------------------------------------------------------------------ > > > 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 FAQ wiki page is located at: > > > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > > > > > > List technical documents are available at: > > > http://www.si-list.org > > > > > > 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 > > > > > > > > > > > > > > > -- > > ------------------- > > Taha Amiralli > > thamiral [A] uwo [D] ca > > thamiral [A] gmail [D] com > > > > MESc Candidate 2007, Computer Engineering > > The University Of Western Ontario > > > > BESc, BSc. 2005, > > Computer Engineering & Computer Science > > The University Of Western Ontario > > --------------------------------------------------------------- > > > > > > ------------------------------------------------------------------ > > 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 FAQ wiki page is located at: > > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > > > > List technical documents are available at: > > http://www.si-list.org > > > > 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 FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org 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