[SI-LIST] Re: (no subject)
- From: "Jian X. Zheng" <jian@xxxxxxxxxx>
- To: <JK100005@xxxxxxxxxxxxxxxx>, <jeff.loyer@xxxxxxxxx>,<si-list@xxxxxxxxxxxxx>
- Date: Wed, 11 Dec 2002 10:34:04 -0800
Hi, Jim:
I don't think that the pulses will be sharpend if you have dispersion. No
matter low frequency is faster or high frequency is faster, it will cause
the relative offset of the harmonics in your clock signal. At the start
point of the transmission, the sum of the harmonics may create a sharp edge.
After transmission, the harmonics will be shifted due to the difference in
the speed of different frequencies. Then, the summation of the harmonics
will create much ripple or rounded effect there. Thanks!
Best regards,
-----------------------------------------------------------------------
Jian-X. Zheng, Ph.D
Zeland Software, Inc., 48890 Milmont Drive, 105D, Fremont, CA 94538, U.S.A.
Tel: 510-623-7162, Fax: 510-623-7135, Web: http://www.zeland.com
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> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Knighten, Jim L
> Sent: Wednesday, December 11, 2002 9:48 AM
> To: jeff.loyer@xxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: (no subject)
>
>
>
> Jeff,
>
> Here's one for the dead horse:
>
> Rounding of edges: If a dispersive medium propagates high frequencies
> faster than low frequencies, it is quite possible to see edges in a time
> domain pulse sharpened, rather than rounded (degraded).
>
> Jim
>
>
> Jim Knighten, Ph.D.
> Teradata, a Division of NCR http://www.ncr.com
> 17095 Via Del Campo
> San Diego, CA 92127
> USA
> Tel: 858-485-2537
> Fax: 858-485-3788
> jim.knighten@xxxxxxx
>
> -----Original Message-----
> From: Loyer, Jeff [mailto:jeff.loyer@xxxxxxxxx]
> Sent: Tuesday, December 10, 2002 2:41 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: (no subject)
>
>
> Thanks for all the information. Not to beat a dead horse, but can =
> someone give me the definitive answers on:
>
> 1) Whether Hspice or ADS can simulate dispersion?
>
> 2) How would dispersion show itself? I would expect to measure the =
> effect 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). Of =
> course, it would also be seen on a pulse as a rounding of the edges, but =
> it couldn't be separated from loss effects in that case.
>
> Jeff Loyer
>
> -----Original Message-----
> From: Loyer, Jeff=20
> Sent: Tuesday, December 10, 2002 9:55 AM
> To: 'lifehappiest@xxxxxxxxxxx'; steven.corey@xxxxxxxxxxxxxx;
> si-list@xxxxxxxxxxxxx
> Subject: RE: [SI-LIST] Re: (no subject)
>
>
> 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
> > >>>>>
> > =
> >>>>>------------------------------------------------------------------
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> >
> >--
> >-------------------------------------------
> >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
> >-------------------------------------------
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