Anyone have a decent Spice model for a twisted pair... lossy, not the
ideal model in circulation?
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Twisted Pair
Started by ●December 8, 2013
Reply by ●December 8, 20132013-12-08
On Sun, 08 Dec 2013 10:41:37 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> Gave us:>Anyone have a decent Spice model for a twisted pair... lossy, not the >ideal model in circulation? > > ...Jim Thompsonusing cat 5e specs and hardware and calling it cat 6 would yield lossy operation at the upper end.
Reply by ●December 8, 20132013-12-08
On Sun, 08 Dec 2013 10:41:37 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>Anyone have a decent Spice model for a twisted pair... lossy, not the >ideal model in circulation? > > ...Jim ThompsonThere's enormous variation in twisted pairs, even among "standard" things like compliant CAT5 and CAT6 cables. The Spice lossy delay line implements The Telegrapher's Equation, but ignores skin loss variation with frequency. The best thing to usually do is get a chunk of the actual cable of the expected length and note its step response on a scope, then fiddle the Spice lossy line parameters to match. An extra RC or two sometimes helps fine-tune the model to reality. Multi-pair cables, like CAT5/6, can be expected to have various amounts of crosstalk and pair delay skews, too. https://dl.dropboxusercontent.com/u/53724080/Wire_Cable/Cat6_Risetimes.pdf https://dl.dropboxusercontent.com/u/53724080/Wire_Cable/Stonewall_2.JPG https://dl.dropboxusercontent.com/u/53724080/Wire_Cable/44.2m_CMH_SSTP_CAT6A_Tr.pdf Simple RC equalization helps, if the cables are repeatable. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Reply by ●December 8, 20132013-12-08
On Sun, 08 Dec 2013 10:33:44 -0800, John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:>On Sun, 08 Dec 2013 10:41:37 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>Anyone have a decent Spice model for a twisted pair... lossy, not the >>ideal model in circulation? >> >> ...Jim Thompson > >There's enormous variation in twisted pairs, even among "standard" things like >compliant CAT5 and CAT6 cables. > >The Spice lossy delay line implements The Telegrapher's Equation, but ignores >skin loss variation with frequency. The best thing to usually do is get a chunk >of the actual cable of the expected length and note its step response on a >scope, then fiddle the Spice lossy line parameters to match. An extra RC or two >sometimes helps fine-tune the model to reality. > >Multi-pair cables, like CAT5/6, can be expected to have various amounts of >crosstalk and pair delay skews, too. > >https://dl.dropboxusercontent.com/u/53724080/Wire_Cable/Cat6_Risetimes.pdf > >https://dl.dropboxusercontent.com/u/53724080/Wire_Cable/Stonewall_2.JPG > >https://dl.dropboxusercontent.com/u/53724080/Wire_Cable/44.2m_CMH_SSTP_CAT6A_Tr.pdf > >Simple RC equalization helps, if the cables are repeatable.Thanks! Good collection of data there in your examples! I do remember doing compensation BC (before CAD) using a pre-emphasis leading-edge pulse... on a thousand foot chunk ;-) I'll look at how PSpice does their lossy T-line, and maybe I can adapt. I did some lecturing on skin-effect modeling for Intel eons ago... I'll review my notes. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●December 8, 20132013-12-08
On Sun, 08 Dec 2013 11:55:30 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> Gave us:>On Sun, 08 Dec 2013 10:33:44 -0800, John Larkin ><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: > >>On Sun, 08 Dec 2013 10:41:37 -0700, Jim Thompson >><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >> >>>Anyone have a decent Spice model for a twisted pair... lossy, not the >>>ideal model in circulation? >>> >>> ...Jim Thompson >> >>There's enormous variation in twisted pairs, even among "standard" things like >>compliant CAT5 and CAT6 cables. >> >>The Spice lossy delay line implements The Telegrapher's Equation, but ignores >>skin loss variation with frequency. The best thing to usually do is get a chunk >>of the actual cable of the expected length and note its step response on a >>scope, then fiddle the Spice lossy line parameters to match. An extra RC or two >>sometimes helps fine-tune the model to reality. >> >>Multi-pair cables, like CAT5/6, can be expected to have various amounts of >>crosstalk and pair delay skews, too. >> >>https://dl.dropboxusercontent.com/u/53724080/Wire_Cable/Cat6_Risetimes.pdf >> >>https://dl.dropboxusercontent.com/u/53724080/Wire_Cable/Stonewall_2.JPG >> >>https://dl.dropboxusercontent.com/u/53724080/Wire_Cable/44.2m_CMH_SSTP_CAT6A_Tr.pdf >> >>Simple RC equalization helps, if the cables are repeatable. > >Thanks! Good collection of data there in your examples! > >I do remember doing compensation BC (before CAD) using a pre-emphasis >leading-edge pulse... on a thousand foot chunk ;-) > >I'll look at how PSpice does their lossy T-line, and maybe I can >adapt. I did some lecturing on skin-effect modeling for Intel eons >ago... I'll review my notes. > > ...Jim ThompsonThis has to be a first. Or at least the first in a long time. Could this mean that the group might actually get back on a/the scientific/proper track again? Looks to me like you pointed him onto the right path, and also that he may actually know more about what effects are in play than you do, just has to dig up some recollection between glasses of wine or some such.
Reply by ●December 8, 20132013-12-08
On Monday, 9 December 2013 07:20:30 UTC+11, DecadentLinuxUserNumeroUno wro= te:> On Sun, 08 Dec 2013 11:55:30 -0700, Jim Thompson > <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> Gave us:=20 > >On Sun, 08 Dec 2013 10:33:44 -0800, John Larki=20 > ><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: > >>On Sun, 08 Dec 2013 10:41:37 -0700, Jim Thompso=20 > >><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:=20 > >> > >>>Anyone have a decent Spice model for a twisted pair... lossy, not the==20> >>>ideal model in circulation? =20 > >>=20 > >>There's enormous variation in twisted pairs, even among "standard" thin=gs like compliant CAT5 and CAT6 cables.=20> >> > >>The Spice lossy delay line implements The Telegrapher's Equation, but i=gnores skin loss variation with frequency. The best thing to usually do is = get a chunk of the actual cable of the expected length and note its step re= sponse on a scope, then fiddle the Spice lossy line parameters to match. An= extra RC or two sometimes helps fine-tune the model to reality.=20> >>=20 > >>Multi-pair cables, like CAT5/6, can be expected to have various amounts=of crosstalk and pair delay skews, too.=20> >>=20 > >>https://dl.dropboxusercontent.com/u/53724080/Wire_Cable/Cat6_Risetimes.=pdf> >> > >>https://dl.dropboxusercontent.com/u/53724080/Wire_Cable/Stonewall_2.JPG==20> >>=20 > >>https://dl.dropboxusercontent.com/u/53724080/Wire_Cable/44.2m_CMH_SSTP_=CAT6A_Tr.pdf> >> > >>Simple RC equalization helps, if the cables are repeatable. > >=20 > >Thanks! Good collection of data there in your examples! > > > >I do remember doing compensation BC (before CAD) using a pre-emphasisleading-edge pulse... on a thousand foot chunk ;-)=20> >=20 > >I'll look at how PSpice does their lossy T-line, and maybe I canadapt. I did some lecturing on skin-effect modeling for Intel eons ago... I'll review my notes.>=20 > This has to be a first.Scarcely. Larkin and Thompson have been posting here for a long time, and l= iked each other a lot better early on. =20> Or at least the first in a long time.Perhaps. =20> Could this mean that the group might actually get back on a/the scienti=fic/proper track again? It's never got off it. The political stuff is just background noise which s= hows up when there's nothing technical to talk about. <snipped the stuff about personalities and performance> --=20 Bill Sloman, Sydney
Reply by ●December 8, 20132013-12-08
On Sun, 8 Dec 2013 16:35:31 -0800 (PST), Bill Sloman <bill.sloman@gmail.com> Gave us:> >Scarcely. Larkin and Thompson have been posting here for a long time, and liked each other a lot better early on.Idiot. I was here long before you, and remember. I don't need a refresher, jackass. Particularly not from a dork like you.
Reply by ●December 8, 20132013-12-08
On Monday, 9 December 2013 11:44:39 UTC+11, DecadentLinuxUserNumeroUno wro= te:> On Sun, 8 Dec 2013 16:35:31 -0800 (PST), Bill Sloman > <bill.sloman@gmail.com> Gave us: > >=20 > >Scarcely. Larkin and Thompson have been posting here for a long time, an=d liked each other a lot better early on.> =20 > Idiot. I was here long before you, and remember. I don't need a refre=sher, jackass. Particularly not from a dork like you. My first post here dates from 1996. When did you first post here? I know that it's dorkish to intrude facts into a pissing contest, but someo= ne who posts under a constantly changing alias is at a substantial disadvan= tage when he wants to claim to have been here for a long time. We did have = our resident idiots early on, but my feeling is that you weren't one of the= m. --=20 Bill Sloman, Sydney
Reply by ●December 8, 20132013-12-08
In article <3bac84d9-733c-4a33-a093-b7661ef14fda@googlegroups.com>, bill.sloman@gmail.com says...> > On Monday, 9 December 2013 11:44:39 UTC+11, DecadentLinuxUserNumeroUno wrote: > > On Sun, 8 Dec 2013 16:35:31 -0800 (PST), Bill Sloman > > <bill.sloman@gmail.com> Gave us: > > > > > >Scarcely. Larkin and Thompson have been posting here for a long time, and liked each other a lot better early on. > > > > Idiot. I was here long before you, and remember. I don't need a refresher, jackass. Particularly not from a dork like you. > > My first post here dates from 1996. When did you first post here? > > I know that it's dorkish to intrude facts into a pissing contest, but someone who posts under a constantly changing alias is at a substantial disadvantage when he wants to claim to have been here for a long time. We did have our resident idiots early on, but my feeling is that you weren't one of them.You know how to make friends.. Jamie
Reply by ●December 8, 20132013-12-08
On Monday, 9 December 2013 12:04:23 UTC+11, Maynard A. Philbrook Jr. wrote= :> In article <3bac84d9-733c-4a33-a093-b7661ef14fda@googlegroups.com>,=20 > bill.sloman@gmail.com says...=20 > > On Monday, 9 December 2013 11:44:39 UTC+11, DecadentLinuxUserNumeroUno =wrote:=20> > > On Sun, 8 Dec 2013 16:35:31 -0800 (PST), Bill Sloman=20 > > > <bill.sloman@gmail.com> Gave us:=20 > > > >=20 > > > >Scarcely. Larkin and Thompson have been posting here for a long time=, and liked each other a lot better early on.> > > =20 > > > Idiot. I was here long before you, and remember. I don't need a r=efresher, jackass. Particularly not from a dork like you.> >=20 > > My first post here dates from 1996. When did you first post here?=20 > > =20 > > I know that it's dorkish to intrude facts into a pissing contest, but s=omeone who posts under a constantly changing alias is at a substantial disa= dvantage when he wants to claim to have been here for a long time. We did h= ave our resident idiots early on, but my feeling is that you weren't one of= them.> =20 > You know how to make friends..You want AlwaysWrong or one of his clones as a friend? --=20 Bill Sloman, Sydney
