Hi Scott, many thanks for the detailed clarification. This was exactly the answer I was looking for, even though I was hoping there is an easier way. I tested impulse response and frequency sweep simulation for the models, but didn get a response at all. I also tested step response which somehow worked, but the output didn't make much sense. I think the models aren't throughly linear, even though the input and output stages seem to be. Based on that I will go ahead with "trial and error" settings sweep to find the optimum. I'd like to thank everyone who responded online and offline for their effort and support. BR Gert http://www.mesago.de/de/SPS/home.htm Besuchen sie uns auf der SPS/IPC/Drives in Nürnberg, vom 23. - 25. November 2010, in Halle 10, Stand 130. -------------------------------------------------------------------------- Absender ist HARTING Electronics GmbH & Co. KG; Sitz der Gesellschaft: Espelkamp; Registergericht: Bad Oeynhausen; Register-Nr.: HRA 5596; persönlich haftende Gesellschafterin: HARTING Electronics Management GmbH; Sitz der Komplementär-GmbH: Espelkamp; Registergericht der Komplementär-GmbH: Bad Oeynhausen; Register-Nr. der Komplementär-GmbH: HRB 8808; Geschäftsführer: Edgar-Peter Duening, Torsten Ratzmann -----Ursprüngliche Nachricht----- Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] Im Auftrag von Scott McMorrow Gesendet: Mittwoch, 24. November 2010 23:14 An: si-list@xxxxxxxxxxxxx Betreff: [SI-LIST] Re: AW: Re: optimize Equalization and De-emphasis settings Guys, With all due respect, the problem Gert has is one of non-Linear, non-LTI optimization. The optimal equalization for one stage in these multiple link systems is not optimal for multiple stages cascaded, especially when distorted waveforms are passed through non-linear switch matrices. Given the channel that you have Gert (driver-PCB-switch-PCB-switch-PCB-reclocker-PCB-Receiver) You can treat this as two problems that can be optimized separately. 1- (driver-PCB-switch-PCB-switch-PCB-reclockerInput) 2 - (reclockerOutput-PCB-Receiver) #2 is amenable to the approaches that multiple people have suggested. #1 is a PITA. If the switches operate in the linear amplification region, then this is just a cascaded amplifier/equalizer problem, not unlike a video cable system. You have to keep the signal in the linear region at all inputs, above the noise floor of the input amplifier, and below the clipping region. In that case, each switch and interconnect can be handled as a transfer function, modeled as s-parameters, and optimized accordingly. But ... you need to know what they are. If any of the amplifiers clip then you have the impact of clipping on the spectrum, which then causes the transfer function to be dependent on the received signal waveform. If the clipping is reasonably predictable, then you still might be able to use linear assumptions. If limiting amplifiers are used in the silicon, then you have a really nasty non-linear problem, since a limiting amplifier looks like a digital sampler with amplitude as the trigger, but with finite gain. The transfer response changes with time. If I were attempting to optimize this (and thankfully I'm not!) I would try to characterize the switch that you're using, and determine just how linear it is from input to output with whatever the nominal equalization is. If the switch is fully composed of linear amplifiers, and no switch elements, then you can perform frequency domain sweeps from input to output, with the input biased to the correct common mode voltage, and a variable differential p-p voltage across multiple sweeps. This will give you a series of curves that describe the transfer function as a function of input amplitude. With some luck, you'll find a linear sweet spot that is large enough to allow for latitude in optimization. If the model is not amenable to FD sweeps, then just perform impulse response simulations at various amplitudes and derive the transfer response. If there is limiting or clipping going on, then you might be able to characterize the silicon at an amplitude low enough to stay out of the clipping/limiting region that is linear, and then model the limiting amplifier behaviorally. Once you find a characterization method that "works" then use the p-p voltage in the center of the linear range to characterize each equalizer setting in the switch. From these, you can derive a simplified model for each equalizer boost setting. Good luck Scott Scott McMorrow Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 (401) 284-1827 Business (401) 284-1840 Fax http://www.teraspeed.com Teraspeed® is the registered service mark of Teraspeed Consulting Group LLC On 11/24/2010 3:39 AM, Havermann, Gert wrote: > Hello Vladimir, > > thanks for the clarification (especially about StatEye). As you say, there is > no digital processing involved, thus StatEye will not be much help. > > The logical step to simulate each passive link separately doesn't apply > either. I started that way, but the silicon passes a lot of effects thru to > the output (they behave more like an amplifier than a switch). > > You are right, that if a bit doesn't pass one of the switches it is lost for > good, but a bit with decreased amplitude or timing will influence the next > channel section. In my case, I can for instance use one silicons equalizer to > get a better signal output at the next silicon. The timing portion of the > "over"- equalization passes thru the silicon and acts like a pre-equalization > (is just a small effect, but given the fact that the passive links are 45" > long and contain multiple vias ith long stubs (>200 mil via stub!!) I need > all the performance I can get. > > BR > Gert > > > http://www.mesago.de/de/SPS/home.htm > > Besuchen sie uns auf der SPS/IPC/Drives in Nürnberg, vom 23. - 25. November > 2010, in Halle 10, Stand 130. > > ---------------------------------------------------------------------- > ---- Absender ist HARTING Electronics GmbH& Co. KG; Sitz der > Gesellschaft: Espelkamp; Registergericht: Bad Oeynhausen; > Register-Nr.: HRA 5596; persönlich haftende Gesellschafterin: HARTING > Electronics Management GmbH; Sitz der Komplementär-GmbH: Espelkamp; > Registergericht der Komplementär-GmbH: Bad Oeynhausen; Register-Nr. > der Komplementär-GmbH: HRB 8808; Geschäftsführer: Edgar-Peter Duening, > Torsten Ratzmann -----Ursprüngliche Nachricht----- > > > Von: si-list-bounce@xxxxxxxxxxxxx > [mailto:si-list-bounce@xxxxxxxxxxxxx] Im Auftrag von Dmitriev-Zdorov, > Vladimir > Gesendet: Dienstag, 23. November 2010 23:46 > An: si-list@xxxxxxxxxxxxx > Betreff: [SI-LIST] Re: optimize Equalization and De-emphasis settings > > Hi Steve, > > As was stated in the original question: "I'm looking for some technique or > algorithm to determine the desired amount of equalization just by examining > each silicon's input signal". Therefore I think that the purpose was to find > equalization in every analog portion separately. Digital processing in the > silicon itself is not involved. > > We cannot generate the combined 4-port model that includes switches and > channels, or equally we shouldn't produce combined model for the channels > separated by switches. Switch is not something that can contribute to the > transfer function or S-parameters, because it is a heavily non-linear > transformation - similar to A/D converter. > > Logically, it also does not make sense to combine links because if the first > switch fails (produces incorrect bit) all others should fail too, and no > equalization in the subsequent links will help. Therefore equalization should > be constructed separately for each analog link. > > In Hyperlynx FastEye, there is a possibility to find optimal set of FFE and > DFE taps, given the channel schematic, S-parameters or its equivalent step or > pulse response. > > Vladimir > > > > -----Original Message----- > From: si-list-bounce@xxxxxxxxxxxxx > [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Stephen Zinck > Sent: Tuesday, November 23, 2010 6:28 AM > To: 'Havermann, Gert'; si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] Re: optimize Equalization and De-emphasis settings > > Hi Gert, > > If you are using Altera or Broadcom, they have applications that automate > this process (other vendors may also have this capability). All you do is > provide a 4-port S-parameter model of your system and the tool will tell you > the required settings for the most open eye. Pretty cool. > > I use SIWave from Ansoft to extract all the features for a particular link > (BGA pads, traces, accurate via models, passive pads, etc.). The output of > this tool is 4-port S-parameters. If multiple system S-parameter files are > required for each element (switch-backplane-switch), these models are then > concatenated in Ansoft's Designer SI. This tool can accurately concatenate > S-parameter files into a single file for the entire system. > > Best regards, > Steve > > Stephen P. Zinck > High-Speed Signal Integrity Consulting Interconnect Engineering Inc. > P.O. Box 577 > South Berwick, ME 03908 > Phone - (207) 384-8280 > Email - szinck@xxxxxxxxxxxxxxxxxxxxxxxxxxx > Web - www.interconnectengineering.com > > -----Original Message----- > From: si-list-bounce@xxxxxxxxxxxxx > [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Havermann, Gert > Sent: Tuesday, November 23, 2010 07:05 AM > To: si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] optimize Equalization and De-emphasis settings > > Dear Experts, > > is there any way to determin the optimum settings for Equalization and > De-emphasis in a channel simulation? > > Situation: I'm running simulations of cascaded channels > (driver-PCB-switch-PCB-switch-PCB-reclocker-PCB-Receiver). Each silicon has > analog equalization and de-emphasis, only some have ECR, thus i can't just > simulate section by section. > > Simulation takes very long, thus I would like to start with optimum settings. > I'm looking for some technique or algorithm to determin the desired amount > of equalization just by examining each silicon's input signal (Eye, spectrum, > timing...). > > Any thoughts or paper reference is appreciated. > > BR > Gert > > http://www.mesago.de/de/SPS/home.htm > > Besuchen sie uns auf der SPS/IPC/Drives in Nürnberg, vom 23. - 25. November > 2010, in Halle 10, Stand 130. > > > ---------------------------------------------------------------------- > ---- Absender ist HARTING Electronics GmbH& Co. KG; Sitz der > Gesellschaft: Espelkamp; Registergericht: Bad Oeynhausen; > Register-Nr.: HRA 5596; persönlich haftende Gesellschafterin: HARTING > Electronics Management GmbH; Sitz der Komplementär-GmbH: Espelkamp; > Registergericht der Komplementär-GmbH: Bad Oeynhausen; Register-Nr. > der Komplementär-GmbH: HRB 8808; Geschäftsführer: Edgar-Peter Duening, > Torsten Ratzmann > > ------------------------------------------------------------------ > 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 > > > > ------------------------------------------------------------------ > 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 > > ------------------------------------------------------------------ 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 ------------------------------------------------------------------ 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