Abe et al- There is another dimension to the model vs. measurement exercise - one which i have been grapeling with for awhile. This is the time AND frequency domain correlation. Just because the time domain response matches measurement, does NOT necessarily produce frequency domain correlation - and visa versa. (i.e. transfer response, or TDT in time domain). And it IS important to match things up - mutually. In my work, i initiate my modeling exercise from TDR measurements because of its greater 'bandwidth' compared to my order of magnitude lower BW VNA, and because i need to see the spacial response. However, when i look at transfer response in the freq domain - i do not see as much modeled loss as i measure. This is partly to do with my model construct, for sure. Would appreciate any commentary regarding this disparity from ALL the community: - mutual-domain correlation validation practice -mutual-domain non-correlation reasons Regards, Greg Kimball PS Yes, i also use Excel to marry my PSPICE and measured waveforms Abe Riazi wrote: > Dear all, > > Comparing simulation generated waveforms with the corresponding lab measured > data can yield valuable information towards identifying/eliminating signal > integrity problems, enhancing buffer and > interconnect models, and optimizing simulation/measurement techniques, etc. > > One effective correlation approach involves superimposing the measured and > simulated > waveforms utilizing Microsoft Excel. This is feasible because many simulator > and measurement > tools can output data in a format compatible with Excel. For instance, the > Multi-column (.dat) files exported by XNS and .csv (Comma Space Delimited) > files stored by digital oscilloscopes can be readily imported into an Excel > spreadsheet. It is important for the simulated and measured data > to have similar bit patterns and to be captured at the same location > (topology node). Let us > consider a sample case. > > Example. > A signal waveform, belonging to memory subsystem of a high-speed > motherboard, was captured (in Read cycle) using a HP infinium 1.5GHz 8GSa/S > oscilloscope, in conjunction with Tektronix P6248 (1.7 GHz) differential > probes. The result was recorded in .bmp ( for quick viewing) and .csv ( for > importing to Excel) formats. Waveform examination revealed that the measured > signal initiates > in High Z state, makes a transition to Low (remains Low for 5 nS), then > switches to High (stays > High for 10 nS), followed by another transitions to Low (for 5 nS) and > finally to High Z. > The corresponding simulations were performed utilizing XTK. A .mdc ( > Multi-Driver > Contention) file was constructed in a manner that the driver output exhibited > same bit pattern as measured signal. Furthermore, the simulation waveform > was probed at the topology node > consistent with measured data. The simulation result was then exported and > saved in Multi-column (.dat) format. The measured " .csv " and the > simulated " .dat " files were entered into Excel for correlation analyses. It > was noted that the time axis of simulated result required a conversion (from > nano seconds to seconds) and the measured data needed a time shift of ~ > 800pS, in order to optimally overlay the two signals.. > > Above example has described a way for superimposing measured and simulated > waveforms. > > With the simulated/measured results properly overlaid, it is possible to > evaluate their sameness > and/or differences. The signal features frequently examined include the low > and high DC quiescent voltage levels, the rise/fall times, > overshoot/undershoot, ringing, ringback, glitches, etc. > > It is also important that the selected simulation corner (i.e. Min, Typ, Max) > and > the voltage/temperature conditions of measured data to be consistent with > each other. > Although, the nominal corner correlations are very common; correlating under > Fast (best case) > and Slow (worst case) requirements can be also beneficial. Furthermore, it > may be necessary to evaluate the signal waveforms at both the driver output > and the receiver input pins (or pads). > > Comparison of simulated and measured data usually reveals certain differences > some > of which can be due to model deficiencies, simulator limitations, or certain > measurement > inaccuracies. Correctly interpreting the measured/simulated signal features, > their similarities > and differences constitute a crucial element of accurate correlation. > > In summary, comparing key features of simulated and measured waveforms can be > helpful > towards identification/ removal of SI degradation, model optimization, and > improvements of simulation/measurement methods. Correlation can be carried > out by overlaying the measured > and simulated waveforms using the Excel program. This approach often > necessitates applying > certain adjustments/shifts to time axis data of one or both waveforms to > achieve optimum > superposition of the results. It is usually desirable that the points > (topology nodes) of capture, > driver output bit patterns, voltage/temperature conditions of simulated and > measured waveforms be nearly matched. > > Your comments are highly appreciated. > > Respectfully, > > Abe Riazi > ServerWorks > > ------------------------------------------------------------------ > 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 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 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