Stephen, what are you observing that you think is different at one end versus the other? What have you done to determine that the difference you see in your simulations: * Correlate to real results * Is due to position at one end of the line versus the other rather than some other inadvertent difference introduced in different test cases I suspect the latter. Regards, Steve Stephen Zinck wrote: > Hi Scott, > My simulations show that the capacitor is best placed at the receiver end of > the transmission-line. Do you disagree? If so, why? > > Steve > > Stephen P. Zinck > 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: Scott McMorrow > To: signalintegrity@xxxxxxxxxxx > Cc: jory_mckinley@xxxxxxxxx ; leeritchey@xxxxxxxxxxxxx ; npatel@xxxxxxxxxx > ; si-list@xxxxxxxxxxxxx > Sent: Tuesday, September 25, 2007 8:30 AM > Subject: Re: [SI-LIST] Re: AC Coupled Signals > > > Stephen, > > I'm sorry, this is a linear system. Except for possible resonances that > are created by discontinuities and modal conversion (which have absolutely > zero to do with signal rise time), there is no difference in the attenuation > of a capacitor placed at the Tx as opposed at the Rx. W.R.T. the receiver, > if it is "lost in the rise-time degradation of the system", it will be lost > wherever it is placed. > > > > 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 > > > Stephen Zinck wrote: > Hi Jory, > > I have simulated this at length and concur with your experience that the > capacitor is best placed at the receiver... > > In effect, the attenuation associated with the capacitor placement at the > receiver (parasitics/pads/vias) is lost in the rise-time degradation of the > system. > The classic "don't break it until you have to" rule is applicable... OK this > is my rule... :-) > > All the best, > Steve > > Stephen P. Zinck > 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: "Jory McKinley" <jory_mckinley@xxxxxxxxx> > To: <leeritchey@xxxxxxxxxxxxx>; <npatel@xxxxxxxxxx>; <si-list@xxxxxxxxxxxxx> > Sent: Monday, September 24, 2007 5:31 PM > Subject: [SI-LIST] Re: AC Coupled Signals > > > I will elaborate a bit on what I have seen. I have measured (time domain) > in the lab some effects that appears to be location specific in the > placement of the AC coupling caps at the rcvr. Now this may be due in part > to the fact that I am using 50-ohm resistor termination in each lead as > well and the combination (cap plus rcvr reflection) is giving some > imbalance depending on distance. The best rcvr eye that I am seeing is > when I can move the AC/term as close to the rcvr as I can. By the way > these are 5Gb/s signals. > If I have time I will try and isolate what I am seeing and even simulate > it, has anyone else seen or simulated this? > -Jory > > ----- Original Message ---- > From: Lee Ritchey <leeritchey@xxxxxxxxxxxxx> > To: "npatel@xxxxxxxxxx" <npatel@xxxxxxxxxx>; si-list@xxxxxxxxxxxxx > Sent: Monday, September 24, 2007 1:06:06 PM > Subject: [SI-LIST] Re: AC Coupled Signals > > Nikil, > > I have made measurements on test PCBs and the location is not all that > important. In identical pairs, one with AC coupling capacitors and the > other without, the loss vs. frequency is virtually identical at leas out > to > 6 GHz. That would be 12 Mb/S. > > Lee Ritchey > > > [Original Message] > From: <npatel@xxxxxxxxxx> > To: <si-list@xxxxxxxxxxxxx> > Date: 9/24/2007 10:21:37 AM > Subject: [SI-LIST] AC Coupled Signals > > Hi all, > In case of AC coupled signals does anyone know of an optimum placement > for the caps? I mean should they be placed near the source, receiver, > middle of the transmission line? > How much difference does it make in the opening of the eye? > The signals are differential CML running at 3.0Gbps > > Thanks, > Nikhil > > > ------------------------------------------------------------------ > 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 > > > > > > > > > > > ____________________________________________________________________________________ > Moody friends. Drama queens. Your life? Nope! - their life, your story. > Play Sims Stories at Yahoo! Games. > http://sims.yahoo.com/ > ------------------------------------------------------------------ > 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 > > > > > ------------------------------------------------------------------ > 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 > > > > > -- Steve Weir Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 California office (408) 884-3985 Business (707) 780-1951 Fax Main office (401) 284-1827 Business (401) 284-1840 Fax Oregon office (503) 430-1065 Business (503) 430-1285 Fax http://www.teraspeed.com This e-mail contains proprietary and confidential intellectual property of Teraspeed Consulting Group LLC ------------------------------------------------------------------------------------------------------ Teraspeed(R) is the registered service mark of Teraspeed Consulting Group LLC ------------------------------------------------------------------ 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