Charles, The simulation was made with both differential signal traces on the top layer of the PCB. There was 0.5 oz solder mask (Er of 3.3) on top of a 0.5 oz copper trace that was 5 mills wide. 3 mills of dielectric Er 4.3 loss tangent 0.02 1 oz solid plane. The two pictures showed a trace to trace separation of 1 mills ... ie 1X trace to plane distance and 30 mills ... ie 10X trace to plane distance. In both cases the traces were 5 mills wide and 3 mills above the ground plane. TFox At 03:43 PM 7/2/2007, Grasso, Charles wrote: >Terry - A quick check shows that your results were derived using a >microstrip cross section with no mask coating. Is that correct? > >Best Regards >Charles Grasso >Compliance Engineer >Echostar Communications Corp. >Tel: 303-706-5467 >Fax: 303-799-6222 >Cell: 303-204-2974 >Pager/Short Message: 3032042974@xxxxxxxxx >Email: charles.grasso@xxxxxxxxxxxx > >-----Original Message----- >From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] >On Behalf Of Terry Fox >Sent: Monday, July 02, 2007 4:17 PM >To: si-list@xxxxxxxxxxxxx >Subject: [SI-LIST] Re: DC-blocking transmission-line > >Aubrey, Ron, > >I always appreciate learning something through the experience of others >rather than having to get it the hard way. > >I suspect there is a certain amount of conflict in our terminology. > >I placed a short explanation about what I was talking about on >http://www.siemc.com/SI_List.htm > >The link has a schematic and two simulation examples. One example is >very >close trace to trace spacing, the other has very wide trace to trace >spacing. In both cases the traces are 20 inches long using a PCI >Express >driver. > >The difference between the two is about 10% in eye opening. > >I am happy to do more simulations to illustrate your points, I just want >a >common picture from which we can all work. > >TFox > > At 12:22 PM 6/28/2007, Aubrey_Sparkman@xxxxxxxx wrote: > > >I don't believe in public stoning.... > > > >What you have said is pretty much true for the special case where the > >two 50 Ohm traces are far enough appart to have negligible coupling. > >Take a look at cases where there is significant coupling. For >instance, > >make a 100 Ohm diff pair from two 60 Ohm traces. Let me know... > > > > > >Aubrey Sparkman > >Enterprise Engineering Signal Integrity Team > >Dell, Inc. > >Aubrey_Sparkman@xxxxxxxx > >(512) 723-3592 > > > >The Greatest Pleasure in Life is Doing what People say can't be done... > > > >-----Original Message----- > >From: si-list-bounce@xxxxxxxxxxxxx >[mailto:si-list-bounce@xxxxxxxxxxxxx] > >On Behalf Of Terry Fox > >Sent: Thursday, June 28, 2007 12:29 PM > >To: gkorony@xxxxxxxxx; Si-List > >Subject: [SI-LIST] Re: DC-blocking transmission-line > > > >At risk of being stoned...the "differential impedance" has very little > >to do with anything. > > > >The key issues is the impedance of the individual lines to their > >reference. > > > >The number "differential impedance" comes from 2 X Z0 which is the > >characteristic impedance of each of the individual lines. > > > >If these lines are balanced mirror images, the current through each of > >the two Z0 50 ohm resistors cancels and there is no net current out the > >reference...hence you can use a single 100ohm resistor rather than two > >50 ohm resistors. > > > >The out fall of this is that everyone thinks differential imp[edance is > >some magical thing. > > > >In my experience it is not. > > > >He has touched the holy thing...let us now begin the stoning. > > > >TFox > > > >At 07:59 AM 6/28/2007, George Korony wrote: > > > > >Content-Type: multipart/alternative; > > > boundary="----=_NextPart_002_0008_01C7B973.5B78CED0" > > > > > >------=_NextPart_002_0008_01C7B973.5B78CED0 > > >Content-Type: text/plain; > > > charset="iso-8859-1" > > >Content-Transfer-Encoding: 7bit > > > > > >BlankHi All, > > >I am not a board designer, but I do design parts that other people >put > > >on boards. We are working on a new (patent protected) concept: the " > > >DC-blocking transmission-line". > > >Basically the idea is to build a pair of capacitors that can be > > >intercalated on the differential signal traces, having a controlled > > >characteristic impedance between the two capacitors, the obvious >scope > > >is to reduce the reflections that may show up due the DC-blocking > >capacitors. > > >One request, we have, is that the characteristic impedance between >the > > >two capacitors (treated as a simple transmission line) should be 100 > >Ohm. > > >Of course things are not so simple; and my question is: does anyone > > >have a different approach to this problem? > > >Thanks for any suggestion, George. > > > > > > > > > > > > > > > > > >------=_NextPart_002_0008_01C7B973.5B78CED0 > > >Content-Type: text/html; > > > charset="iso-8859-1" > > >Content-Transfer-Encoding: quoted-printable > > > > > ><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> Hi >All, > > >I am not a board designer, but I = do design=20 parts that other >people > > > > >put on boards. We are working on = a new =20 (patent protected) > >concept: > > >the " DC-blocking = transmission-line". > > >Basically the idea is to build a = pair of=20 capacitors that can be > > >intercalated on the differential signal = traces,=20 having a > > >controlled characteristic impedance between the two capacitors, = > > >the=20 obvious scope is to reduce the reflections that may show up >due > > >the = DC-blocking capacitors. > > >One request, we have, is that the=20 characteristic impedance between > > >the two capacitors (treated as a simple = transmission line) should >be > >100 Ohm. > > >Of course things are not so = simple; and my=20 question is: does > > >anyone have a different approach to this = problem? > > >Thanks for any suggestion,=20 George. > > > > > > > > > > > > > > >------=_NextPart_002_0008_01C7B973.5B78CED0-- > > > > > > > > >-- Binary/unsupported file stripped by Ecartis -- > > >-- Type: image/gif > > >-- File: Blank Bkgrd.gif > > > > > > > > > > > >-- Binary/unsupported file stripped by Ecartis -- > > >-- Type: text/x-vcard > > >-- File: George Korony.vcf > > > > > > > > >------------------------------------------------------------------ > > >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 > ------------------------------------------------------------------ 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