# [SI-LIST] Re: (no subject)

• From: "Xin Wu" <lifehappiest@xxxxxxxxxxx>
• To: steven.corey@xxxxxxxxxxxxxx, si-list@xxxxxxxxxxxxx
• Date: Tue, 10 Dec 2002 09:54:00 -0500

Steve, it is not a good idea to mix things together. Wave dispersion
definitely has nothing to do with loss, conceptually. Dispersion is related
to phase velocity, but the loss is related to energy. Of cause, because
signal pulse consists of a bunch of frequency components, different
components propagate at different speed, this makes the pulse shape change
at the reception. However, the total energy of the pulse won't be
dissipated. Dispersion of medium is another concept. If we talking about a
dispersive medium, this means that the dielectric constant of the medium is
frequency dependent, the medium is dispersive. Kramer Kronig relationship is
to explain the medium dispersion rather than wave dispersion.
Of cause, when the medium is frequency dependent, both wave dispersion and
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>
>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
> > ===
> >
> > Loyer, Jeff wrote:
> >
> >
> >>Yu,
> >>When you use the term "dispersive", are you talking about losses
>(resistive, skin effect, dielectric), or about differences in phase
>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
>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,
> >>
> >>
> >>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
> >>===
> >>
> >>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
>you
> >>>referred)
> >>>
> >>>E11 11 12 FREQ {V(10,5)}=
> >>>
> >>>which will not be accepted by some circuit simulators such as ADS. It
>is
> >>>similar to Ansoft fullwave SPICE. I know HSPICE and PSPICE can handle
>it.
> >>>
> >>>Although it is still a research topic in terms of efficiency, stability
>and
> >>>accuracy etc., I know the problem [S] ---> SPICE model (reduced models)
>is
> >>>solvable without the following limitations in several ways. But, can we
> >>>generate broadband SPICE models without frequency dependent lookup
>tables
> >>>such as " FREQ " ?  Or is it still solvable without components "FREQ"
>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
>is
> >>>possible for yourself to make a equivalent subcircuit which can include
>the
> >>>timing and frequency info and then import to a spice like simulator.
>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
>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>
> >>>>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
>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
>from S
> >>>>>matrix for complex structures using the SPICE generator in ADS ? Or
>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,
>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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> >>
> >>
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> >>.
> >>
> >>
> >>
> >
> >
> >
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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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