If anyone could point me to an electronic source of the mentions paper=20 "Theory and Measurement of Unbalanced Differential-Mode Transmission Lines" From DesignCon 2006 I would very much appreciate it. Thanks so much Mark Burford Research Engineer -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of istvan novak Sent: 17 December 2006 15:38 To: hreidmarkailen@xxxxxxxxx Cc: ryan.satrom@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Insertion Loss of Passive Components Agathon, It is true that for electrically short structures there is no need for=20 distributed model. However, the 170-mil length difference is long enough that when measured up to 20 or 40GHz, the time-of-flight difference in the two legs shows up as a cancellation (or resonance). With regular FR4, the 'resonance' could be around 15GHz. There was a paper on this effect at DesignCon 2006: Stephen B. Smith, "Theory and Measurement of Unbalanced Differential-Mode Transmission Lines", and more papers will show up at=20 DesignCon 2007. Regards, Istvan Novak SUN Microsystems agathon wrote: >Ryan, >I would submit that it really ought to help. And, sorry, but please don't >claim that for SI Engineers in general. :-) >All the laws of physics rule, not just some. >The net IS a filter. And, if the section (170mil) is electrically short, >then lumped "filter" modeling could be a perfectly appropriate way to >understand and accurately model its interaction with the rest of the net. >It is a well known technique in any college microwave advanced text. In >that case, the "propagation" is irrelevant and, if resonance is at work, the >variable t, for time, itself is irrelevant. So, time to understand >filters. > >On the other hand, I didn't read any convincing explanation of a "resonance" >on a bare diff pair with mismatched conductor lengths. Most likely, the >higher loss of the pair was due to mode conversion due to the mismatch, >fixed mostly by the adjustment presented by the connector lead lengths, >which WOULD be simply a correction of unequal flight times -- most easily >viewed as a propagation issue; ie: time domain. > > >On 12/13/06, ryansatrom <ryan.satrom@xxxxxxxxxxx> wrote: > =20 > >>John- >> >>You are correct. As an SI Engineer, it doesn't help my understanding >>to view a net as a filter. But that doesn't make it invalid. >> >>Thanks for the insight. >> >>Ryan Satrom >> >> >>--- In si-list@xxxxxxxxxxxxxxx, "Hill, John" <John.Hill@...> wrote: >> =20 >> >>>Ryan, >>> >>>I would summit to you that not all filters use lumped elements. >>> =20 >>> >>Strip >> =20 >> >>>line filters are just lengths of coupled transmission lines and they >>>make very good microware filters.=3D3D20 >>> >>>You can also consider a length of coupled transmission lines as two >>>transmission lines with crosstalk. The vantage point depends a lot >>> =20 >>> >>on if >> =20 >> >>>you are an SI engineer or an RF engineer.=3D3D20 >>> >>>Best regards, >>> >>>John =3D3D20 >>> >>>John Hill >>>Design Engineer >>>TK HOLDINGS INC =3D3D20 >>>Electronics=3D3D20 >>>27200 Haggerty Road Suite B-12 =3D3D20 >>>Farmington Hills, MI 48331 >>>Office Phone: 248 699 2915 >>>Mobile Phone 248 765 3599 >>> >>> >>> >>>=3D3D20 >>> >>>--------------------------------------- >>>The information in this email and attachments hereto may contain >>> =20 >>> >>legally =3D3D >> =20 >> >>>privileged, proprietary or confidential information that is >>> =20 >>> >>intended for =3D3D >> =20 >> >>>a particular recipient. If you are not the intended recipient(s), >>> =20 >>> >>or the =3D3D >> =20 >> >>>employee or agent responsible for delivery of this message to the = =3D3D >>>intended recipient(s), you are hereby notified that any disclosure, >>> =20 >>> >>=3D3D >> =20 >> >>>copying, distribution, retention or use of the contents of this e- >>> =20 >>> >>mail =3D3D >> =20 >> >>>information is prohibited and may be unlawful. When addressed to >>> =20 >>> >>Takata =3D3D >> =20 >> >>>customers or vendors, any information contained in this e-mail is = =3D3D >>>subject to the terms and conditions in the governing contract, if = =3D3D >>>applicable. If you have received this communication in error, >>> =20 >>> >>please =3D3D >> =20 >> >>>immediately notify us by return e-mail, permanently delete any =3D3D >>>electronic copies of this communication and destroy any paper >>> =20 >>> >>copies. >> =20 >> >>>--------------------------------------- >>>-----Original Message----- >>> >>>From: si-list-bounce@... [mailto:si-list-bounce@...] >>>On Behalf Of ryansatrom >>>Sent: Wednesday, December 13, 2006 10:50 AM >>>To: si-list@... >>>Subject: [SI-LIST] Re: Insertion Loss of Passive Components >>> >>>All- >>> >>>Thanks for your insight. I resolved the issue. To those who are=3D3D20 >>>interested, the differential trace model included one trace that >>> =20 >>> >>was=3D3D20 >> =20 >> >>>approximately 170mils longer than the other trace. The connector=3D3D20 >>>launch, due to its geometry, had that same trace 170mils shorter >>> =20 >>> >>than=3D3D20 >> =20 >> >>>the other trace. So when I measured differential insertion loss,=3D3D20 >>>there was a resonance due to the length mismatch on both of = the=3D3D20 >>>subcircuits. However, they pieced together and the resonance was=3D3D20 >>>removed, causing improved insertion loss. >>> >>>John - I like your filter analogy, but I believe that the analogy=3D3D20 >>>breaks down when we become concerned about transmission lines (and >>> =20 >>> >>EM=3D3D20 >> =20 >> >>>waves) and not lumped elements. It does little to feed our >>> =20 >>> >>intuition=3D3D20 >> =20 >> >>>as to how an electromagnetic wave travels down a trace. It is an=3D3D20 >>>analog world, but it's also an electromagnetic world:) >>> >>>--- In si-list@xxxxxxxxxxxxxxx, "Hill, John" <John.Hill@> wrote: >>> =20 >>> >>>>Ryan, >>>>=3D3D20 >>>>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 >>>> =20 >>>> >>of=3D3D20 >> =20 >> >>>the >>> =20 >>> >>>>impedance. >>>>=3D3D20 >>>>Now consider the same filter in the stop band. The inductors and >>>>capacitances do not resonate together and either changes the >>>> =20 >>>> >>real=3D3D20 >> =20 >> >>>value >>> =20 >>> >>>>of the filter or makes it very non-real.=3D3D3D3D20 >>>>=3D3D20 >>>>The point is that in the pass band the filter correctly matches >>>> =20 >>>> >>the >> =20 >> >>>>source impedance to the load impedance and in the stop band = the=3D3D20 >>>> =20 >>>> >>>filter >>> =20 >>> >>>>deliberately miss-matches the impedances.=3D3D3D3D20 >>>>=3D3D20 >>>>Look at your circuit as a filter. Is it matching or miss- >>>> =20 >>>> >>matching=3D3D20 >> =20 >> >>>the >>> =20 >>> >>>>source to the load? Remember digital signal are wide band >>>> =20 >>>> >>signals.=3D3D20 >> =20 >> >>>We >>> =20 >>> >>>>typically need to design our signal paths as low pass filters >>>> =20 >>>> >>with=3D3D20 >> =20 >> >>>high >>> =20 >>> >>>>cutoff frequencies. >>>>=3D3D20 >>>>As we all know, it is an analog world. >>>>=3D3D20 >>>>Best regards, >>>>=3D3D20 >>>>John >>>>=3D3D20 >>>>John Hill >>>>Design Engineer >>>>TK HOLDINGS INC =3D3D3D3D20 >>>>Electronics=3D3D3D3D20 >>>>27200 Haggerty Road Suite B-12 =3D3D3D3D20 >>>>Farmington Hills, MI 48331 >>>>Office Phone: 248 699 2915 >>>>Mobile Phone 248 765 3599 >>>>=3D3D20 >>>>=3D3D20 >>>>=3D3D3D3D20 >>>>=3D3D20 >>>>--------------------------------------- >>>>The information in this email and attachments hereto may >>>> =20 >>>> >>contain=3D3D20 >> =20 >> >>>legally =3D3D3D3D >>> =20 >>> >>>>privileged, proprietary or confidential information that is=3D3D20 >>>> =20 >>>> >>>intended for =3D3D3D3D >>> =20 >>> >>>>a particular recipient. If you are not the intended recipient >>>> =20 >>>> >>(s),=3D3D20 >> =20 >> >>>or the =3D3D3D3D >>> =20 >>> >>>>employee or agent responsible for delivery of this message to the >>>> =20 >>>> >>=3D3D >> =20 >> >>>=3D3D3D3D >>> =20 >>> >>>>intended recipient(s), you are hereby notified that any >>>> =20 >>>> >>disclosure,=3D3D20 >> =20 >> >>>=3D3D3D3D >>> =20 >>> >>>>copying, distribution, retention or use of the contents of this e- >>>> =20 >>>> >>>mail =3D3D3D3D >>> =20 >>> >>>>information is prohibited and may be unlawful. When addressed >>>> =20 >>>> >>to=3D3D20 >> =20 >> >>>Takata =3D3D3D3D >>> =20 >>> >>>>customers or vendors, any information contained in this e-mail is >>>> =20 >>>> >>=3D3D >> =20 >> >>>=3D3D3D3D >>> =20 >>> >>>>subject to the terms and conditions in the governing contract, if >>>> =20 >>>> >>=3D3D >> =20 >> >>>=3D3D3D3D >>> =20 >>> >>>>applicable. If you have received this communication in error,=3D3D20 >>>> =20 >>>> >>>please =3D3D3D3D >>> =20 >>> >>>>immediately notify us by return e-mail, permanently delete any >>>> =20 >>>> >>=3D3D3D3D >> =20 >> >>>>electronic copies of this communication and destroy any paper=3D3D20 >>>> =20 >>>> >>>copies. >>> =20 >>> >>>>--------------------------------------- >>>>-----Original Message----- >>>>=3D3D20 >>>>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 >>>>=3D3D20 >>>>SI-Listers: >>>>=3D3D20 >>>>I have set up a simulation and am very confused by the results. >>>> =20 >>>> >>=3D3D20 >> =20 >> >>>I=3D3D3D3D20 >>> =20 >>> >>>>have a differential trace in series with a connector launch. >>>>=3D3D20 >>>>I am getting very strange insertion loss results so I'm >>>> =20 >>>> >>hoping=3D3D3D3D20 >> =20 >> >>>>somebody could help advise me as to whether my model is wrong, >>>> =20 >>>> >>or=3D3D20 >> =20 >> >>>I=3D3D3D3D20 >>> =20 >>> >>>>am wrong. >>>>=3D3D20 >>>>When I view the differential insertion loss of the system >>>> =20 >>>> >>(both=3D3D3D3D20 >> =20 >> >>>>subcircuits in series), the loss is better (there is less = loss)=3D3D20 >>>> =20 >>>> >>>than=3D3D3D3D20 >>> =20 >>> >>>>the differential insertion of the trace only. Is this possible? >>>> =20 >>>> >>=3D3D20 >> =20 >> >>>I=3D3D3D3D20 >>> =20 >>> >>>>always thought that it was impossible to improve the = insertion=3D3D20 >>>> =20 >>>> >>>loss=3D3D3D3D20 >>> =20 >>> >>>>by adding a passive component. And I think I still believe >>>> =20 >>>> >>that,=3D3D20 >> =20 >> >>>but=3D3D3D3D20 >>> =20 >>> >>>>now I'm getting a little confused. >>>>=3D3D20 >>>>It's also important to note that the single-ended insertion =3D3D >>>> =20 >>>> >>>loss=3D3D3D3D20 >>> =20 >>> >>>>results seem to be as expected. That is, the insertion loss = of=3D3D20 >>>> =20 >>>> >>>the=3D3D3D3D20 >>> =20 >>> >>>>system is worse than the insertion loss of either >>>> =20 >>>> >>individual=3D3D3D3D20 >> =20 >> >>>>component. >>>>=3D3D20 >>>>Is something occurring with the differential signal to allow = it=3D3D20 >>>> =20 >>>> >>>to=3D3D3D3D20 >>> =20 >>> >>>>perform better? >>>>=3D3D20 >>>>Please advise. Thanks in advance for your response. >>>>=3D3D20 >>>>Ryan Satrom >>>>Everett Charles Technologies >>>>ryan.satrom@ >>>>=3D3D20 >>>> =20 >>>> ------------------------------------------------------------------ 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: =20 //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 =20 ------------------------------------------------------------------ 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