All- Thanks for your insight. I resolved the issue. To those who are interested, the differential trace model included one trace that was approximately 170mils longer than the other trace. The connector launch, due to its geometry, had that same trace 170mils shorter than the other trace. So when I measured differential insertion loss, there was a resonance due to the length mismatch on both of the subcircuits. However, they pieced together and the resonance was removed, causing improved insertion loss. John - I like your filter analogy, but I believe that the analogy breaks down when we become concerned about transmission lines (and EM waves) and not lumped elements. It does little to feed our intuition as to how an electromagnetic wave travels down a trace. It is an analog world, but it's also an electromagnetic world:) --- In si-list@xxxxxxxxxxxxxxx, "Hill, John" <John.Hill@...> wrote: > > Ryan, > > Consider a filter, in the pass band the filter can have a lot of > inductors and capacitors between the source and the load, but the > insertion loss is low. This is because all of the inductances and > capacitances resonate together without changing the real value of the > impedance. > > Now consider the same filter in the stop band. The inductors and > capacitances do not resonate together and either changes the real value > of the filter or makes it very non-real.=3D20 > > The point is that in the pass band the filter correctly matches the > source impedance to the load impedance and in the stop band the filter > deliberately miss-matches the impedances.=3D20 > > Look at your circuit as a filter. Is it matching or miss-matching the > source to the load? Remember digital signal are wide band signals. We > typically need to design our signal paths as low pass filters with high > cutoff frequencies. > > As we all know, it is an analog world. > > Best regards, > > John > > John Hill > Design Engineer > TK HOLDINGS INC =3D20 > Electronics=3D20 > 27200 Haggerty Road Suite B-12 =3D20 > Farmington Hills, MI 48331 > Office Phone: 248 699 2915 > Mobile Phone 248 765 3599 > > > =3D20 > > --------------------------------------- > The information in this email and attachments hereto may contain legally =3D > privileged, proprietary or confidential information that is intended for =3D > a particular recipient. If you are not the intended recipient(s), or the =3D > employee or agent responsible for delivery of this message to the =3D > intended recipient(s), you are hereby notified that any disclosure, =3D > copying, distribution, retention or use of the contents of this e- mail =3D > information is prohibited and may be unlawful. When addressed to Takata =3D > customers or vendors, any information contained in this e-mail is =3D > subject to the terms and conditions in the governing contract, if =3D > applicable. If you have received this communication in error, please =3D > immediately notify us by return e-mail, permanently delete any =3D > electronic copies of this communication and destroy any paper copies. > --------------------------------------- > -----Original Message----- > > From: si-list-bounce@... [mailto:si-list-bounce@...] > On Behalf Of ryansatrom > Sent: Tuesday, December 12, 2006 3:49 PM > To: si-list@... > Subject: [SI-LIST] Insertion Loss of Passive Components > > SI-Listers: > > I have set up a simulation and am very confused by the results. I=3D20 > have a differential trace in series with a connector launch. > > I am getting very strange insertion loss results so I'm hoping=3D20 > somebody could help advise me as to whether my model is wrong, or I=3D20 > am wrong. > > When I view the differential insertion loss of the system (both=3D20 > subcircuits in series), the loss is better (there is less loss) than=3D20 > the differential insertion of the trace only. Is this possible? I=3D20 > always thought that it was impossible to improve the insertion loss=3D20 > by adding a passive component. And I think I still believe that, but=3D20 > now I'm getting a little confused. > > It's also important to note that the single-ended insertion loss=3D20 > results seem to be as expected. That is, the insertion loss of the=3D20 > system is worse than the insertion loss of either individual=3D20 > component. > > Is something occurring with the differential signal to allow it to=3D20 > perform better? > > Please advise. Thanks in advance for your response. > > Ryan Satrom > Everett Charles Technologies > ryan.satrom@... > > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@... 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@... with 'help' in the Subject field > > List FAQ wiki page is located at: > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > > List technical documents are available at: > http://www.si-list.org > > List archives are viewable at: =3D20 > //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@... 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@... with 'help' in the Subject field > > List FAQ wiki page is located at: > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > > List technical documents are available at: > http://www.si-list.org > > 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 FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org 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