I've been trying to better understand dispersion and its effects on = signal integrity. Allow me to state what I believe, and feel free to = correct any falacies I've developed (or clarify what I've stated). 1) The key factor "creating" dispersion is the fact that, for a given = medium, different frequencies will travel at different velocities. = I.E., the Er for a material varies, depending on frequency. This same = effect is responsible for prisms' breaking light into its constituent = components and, interestingly enough, causes distortion of earthquake = waves as they travel through the earth. 2) I've heard the term associated with microstrip, but don't know why it = couldn't be present in stripline. 3) The net effect on our (digital S.I. types) signals of interest would = be that a pulse would appear rounded after passing through a dispersive = medium. 3) I don't think Hspice can simulate this phenomena, and I don't know if = ADS can, either. 4) The way I would expect to measure the effect would be with a VNA - I = would expect my S21 phase rate-of-change to vary with frequency. I.E., = for a non-dispersive medium, S21 phase appears as a regular sawtooth. = For a dispersive medium, I would expect the period of that sawtooth to = vary with frequency (probably very linearly). I haven't measured the = effect this way (that I know of, it might have been too subtle for me to = notice), nor have I seen data demonstrating the effect. I would love clarification on the terms "medium dispersion" vs. "wave = dispersion" vs "phase dispersion". I thought there was only a single = dispersion effect of phase velocities being different for different = frequencies. Thanks for your insights... Jeff Loyer -----Original Message----- From: Xin Wu [mailto:lifehappiest@xxxxxxxxxxx] Sent: Tuesday, December 10, 2002 6:54 AM To: steven.corey@xxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: (no subject) Steve, it is not a good idea to mix things together. Wave dispersion=20 definitely has nothing to do with loss, conceptually. Dispersion is = related=20 to phase velocity, but the loss is related to energy. Of cause, because=20 signal pulse consists of a bunch of frequency components, different=20 components propagate at different speed, this makes the pulse shape = change=20 at the reception. However, the total energy of the pulse won't be=20 dissipated. Dispersion of medium is another concept. If we talking about = a=20 dispersive medium, this means that the dielectric constant of the medium = is=20 frequency dependent, the medium is dispersive. Kramer Kronig = relationship is=20 to explain the medium dispersion rather than wave dispersion. Of cause, when the medium is frequency dependent, both wave dispersion = and=20 signal loss will be happening. Xin Wu Ph.D student, University of Maryland, College Park Http://www.wam.umd.edu/~xwu >From: Steve Corey <steven.corey@xxxxxxxxxxxxxx> >Reply-To: steven.corey@xxxxxxxxxxxxxx >To: si-list@xxxxxxxxxxxxx >Subject: [SI-LIST] Re: (no subject) >Date: Mon, 09 Dec 2002 16:44:28 -0800 > > >This illustrates an interesting point, which is that if you have >dispersion, then you have to have frequency-dependent losses as well. >The Kramers-Kronig relationship (a.k.a. causality) states that the real >part and the imaginary parts of the dielectric constant are tightly >related to each other. As a result, frequency-dependent phase velocity >is always accompanied by frequency-dependent attenuation, and vice >versa. So you can easily make the argument that describing something = as >"dispersive" is the same as describing it as "lossy". > >Yu Liu wrote: > > > Jeff, > > > > By definition, I think dispersive effect is the frequency-related = effect > > (phase velocities at different spectrums). However, since the = losses > > are also frequency-dependent, sometimes people just use the term > > interchangbly, which causes confusions. Distinguish the two terms > > (dispersive and loss) would make things clearer. > > > > Yu > > =3D=3D=3D > > > > Loyer, Jeff wrote: > > > > > >>Yu, > >>When you use the term "dispersive", are you talking about losses=20 >(resistive, skin effect, dielectric), or about differences in phase=20 >velocities (page 170 of Pozar's book)? I've heard others refer to loss = >effects as dispersive and have had confusion as a result. Are both = uses of=20 >the term "dispersive" correct? > >> > >>Jeff Loyer > >> > >> > >>-----Original Message----- > >>From: Yu Liu [mailto:yu_liu@xxxxxxxxxxxxx] > >>Sent: Friday, December 06, 2002 9:32 PM > >>To: xlzhou@xxxxxxxxx > >>Cc: 'Xin Wu'; si-list@xxxxxxxxxxxxx > >>Subject: [SI-LIST] Re: (no subject) > >> > >> > >> > >>Mick, > >> > >>To answer your question: In theory, Yes. In practice, No. > >> > >>The fundamental principle for SPICE model approach is using lumped > >>elements (RLC) to model distributed effect (S-parameter). For lower > >>frequency and small size, it is possible. But for broad-band = frequency > >>and large size (say, 20' FR-4), it is very hard to model the = dispersive > >>effects accurately. That's why people start to use = frequency-dependent > >>elements, or better yet, import S-parameter directly into Spice = engine. > >> > >> > >>Regards, > >> > >>Yu > >>=3D=3D=3D > >> > >>Apache Design Solutions > >>web: www.apache-da.com > >> > >> > >> > >>Zhou, Xingling (Mick) wrote: > >> > >> > >> > >>>Xin Wu > >>> > >>>Thanks for your information. It will be valuable. > >>>However, it still contains something like (from the example on the = web=20 >you > >>>referred) > >>> > >>>E11 11 12 FREQ {V(10,5)}=3D > >>> > >>>which will not be accepted by some circuit simulators such as ADS. = It=20 >is > >>>similar to Ansoft fullwave SPICE. I know HSPICE and PSPICE can = handle=20 >it. > >>> > >>>Although it is still a research topic in terms of efficiency, = stability=20 >and > >>>accuracy etc., I know the problem [S] ---> SPICE model (reduced = models)=20 >is > >>>solvable without the following limitations in several ways. But, = can we > >>>generate broadband SPICE models without frequency dependent lookup=20 >tables > >>>such as " FREQ " ? Or is it still solvable without components = "FREQ"=20 >etc. ? > >>> > >>>Regards, > >>> > >>>Mick > >>> > >>>-----Original Message----- > >>>From: Xin Wu [mailto:lifehappiest@xxxxxxxxxxx] > >>>Sent: Friday, December 06, 2002 8:38 PM > >>>To: scott@xxxxxxxxxxxxx; xlzhou@xxxxxxxxx > >>>Cc: si-list@xxxxxxxxxxxxx > >>>Subject: Re: [SI-LIST] Re: (no subject) > >>> > >>> > >>>Hi, XL, > >>> If you want to convert S-matrix into a spice simulator, a lot of > >>>commercial software can do that--that's the simplest way. However, = it=20 >is > >>>possible for yourself to make a equivalent subcircuit which can = include=20 >the > >>>timing and frequency info and then import to a spice like = simulator.=20 >Here > >>>are some application notes: > >>>http://wwwinfo.cern.ch/ce/ae/Maxwell/apps/2stripem/2stripem.html > >>>If you want to get involved in more details, I remembered that = somebody=20 >did > >>>his Ph.D work on this in UIUC around early 1990s'. > >>> > >>> > >>> > >>>Xin Wu > >>>Ph.D student, > >>>University of Maryland, College Park > >>>Http://www.wam.umd.edu/~xwu > >>> > >>> > >>> > >>> > >>> > >>> > >>> > >>> > >>>>From: "Scott McMorrow" <scott@xxxxxxxxxxxxx> > >>>>Reply-To: scott@xxxxxxxxxxxxx > >>>>To: xlzhou@xxxxxxxxx > >>>>CC: "'si-list@xxxxxxxxxxxxx'" <si-list@xxxxxxxxxxxxx> > >>>>Subject: [SI-LIST] Re: (no subject) > >>>>Date: Fri, 06 Dec 2002 13:45:41 -0800 > >>>> > >>>> > >>>>Mick, > >>>> > >>>>There are two solutions which I use: > >>>> > >>>>1) Apache Nspice is an Hspice compatabible simulator that can > >>>>co-simulate with Touchstone S-parameter files. > >>>>http://www.apache-da.com/ > >>>> > >>>>2) Sigrity BroadBand Spice can convert Touchstone s-parameter = files=20 >into > >>>>spice black boxes. > >>>>http://www.sigrity.com/ > >>>> > >>>>Both are scary accurate in both the frequency and time domain. > >>>> > >>>>regards, > >>>> > >>>>scott > >>>> > >>>>-- > >>>>Scott McMorrow > >>>>Teraspeed Consulting Group LLC > >>>>2926 SE Yamhill St. > >>>>Portland, OR 97214 > >>>>(503) 239-5536 > >>>>http://www.teraspeed.com > >>>> > >>>> > >>>>Zhou, Xingling (Mick) wrote: > >>>> > >>>> > >>>> > >>>> > >>>>>Hello, > >>>>> > >>>>>Did anybody successfully generate broadband (DC-20GHz) SPICE = model=20 >from S > >>>>>matrix for complex structures using the SPICE generator in ADS ? = Or=20 >any > >>>>>other alternatives. I know Ansoft fullwave SPICE does the work. > >>>>>Unfortunately, some circuit simulators do not support the = frequency > >>>>>dependent lookup table sources. We can definitely use [S] = directly,=20 >but > >>>>> > >>>>> > >>>>> > >>>>some > >>>> > >>>> > >>>> > >>>>>users still prefer SPICE models. Any experience to share ? > >>>>> > >>>>>Thanks, > >>>>> > >>>>>Xingling(Mick) Zhou, PhD > >>>>>Signal Integrity Technologist > >>>>>Agere Systems > >>>>> > >>>>>Tel: 610-712-7462 > >>>>>Fax: 610-712-4081 > >>>>> > = >>>>>------------------------------------------------------------------ > >>>>>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 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 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 > >>>> > >>>> > >>>> > >>>> > >>>_________________________________________________________________ > >>>Add photos to your messages with MSN 8. Get 2 months FREE*. > >>>http://join.msn.com/?page=3Dfeatures/featuredemail > >>>------------------------------------------------------------------ > >>>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 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 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 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 > > > > > > > > > > >-- >------------------------------------------- >Steven D. Corey, Ph.D. >Time Domain Analysis Systems, Inc. >"The Interconnect Modeling Company." >http://www.tdasystems.com > >email: steven.corey@xxxxxxxxxxxxxx >phone: (503) 246-2272 >fax: (503) 246-2282 >------------------------------------------- > >------------------------------------------------------------------ >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 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 > _________________________________________________________________ The new MSN 8: advanced junk mail protection and 2 months FREE*=20 http://join.msn.com/?page=3Dfeatures/junkmail ------------------------------------------------------------------ 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 archives are viewable at: =20 //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages=20 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 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