[SI-LIST] Re: Signal crossing Split plane
- From: "Ray Anderson" <ray.anderson@xxxxxxxxxx>
- To: <ch_harrington@xxxxxxxxx>
- Date: Thu, 6 Dec 2007 15:42:52 -0800
Charles-
I'm not quite sure what is going on here, and truthfully I really don't
want or need to know, however your past couple of messages really aren't
the kind of traffic si-list is intended to support.
Si-list is intended for technical interchange, not for personal attacks
or denials or rebuttals of same.
So as the administrator of si-list I'd like to request that you pursue
this message thread somewhere off of si-list. If you would care to stick
to the technicalities of the matter then by all means feel free to carry
on those discussions here on the list.
Thank you for you consideration in this matter.
Regards,
Ray Anderson
(si-list admin)
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Charles Harrington
> Sent: Thursday, December 06, 2007 1:14 PM
> To: Scott McMorrow
> Cc: Chris.Cheng@xxxxxxxx; Jean-Pierre Maurice; shlepnev@xxxxxxxxxxxxx;
si-
> list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Signal crossing Split plane
>=20
> Scott,
>=20
> I need no credibility from your eyes, because you've got none on
mine.
> You believe in friendship, biographies, self-praise, credentials,
> experience etc.
>=20
> I don't need to prove to you that I have any experience and I'm
hiding
> from no one. If you wish, go ahead and consder that I have no
experience.
> I'm fine with that.
>=20
> You always take sides unnecessarily in this list, especially when
the
> posting comes from your friend or some one you know his biography.
That's
> wrong.
>=20
> I believe in nothing but the facts. Go ahead and disprove the facts,
if
> you can, and forget about my biography.
>=20
> Why didn't you name the tool, if you know any? You can't believe me
> because you don't know my biography. Why didn't you propose the
> methodology Chris needed?
>=20
> Well, I hope Chris is satisfied with your answer. To me you wrote
much
> and said nothing, because you are blind with other matters that have
> nothing to do with the facts.
>=20
> I have accussed no one. I'm throwing darts at no one and will never
do
> that.
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> Scott McMorrow <scott@xxxxxxxxxxxxx> wrote:
> Charles,
>=20
> You said: "I disagree with Yuriy that a tool can define the boundaries
> of discontinuties and decompose the channel. If he still believe this
is
> true, then he should name the tool."
>=20
> IMO, there is no reason why a PCB SI tool cannot do exactly what Yuriy
> says. That one does not now, does not preclude the possibility. Since
> a tool based on a physical layout, netlist, and driver locations has
> knowledge of all signal paths, and direction of signal travel, it
would
> be possible to automate the process of defining appropriate TEM and
> Quasi-TEM boundaries, placing ports, performing full-wave extractions,
> caching the results for other identical structures, and then
integrating
> the sub-circuits into a complete end-to-end model. I also do not see a
> reason why it would not be possible to identify "problematic"
structures
> where well-defined return paths do not exist over the bandwidth of
> interest, warn the user of the inherent errors in modeling, and
possibly
> even suggest alternatives to modify the structure. (Do not pick nits
> with me over the details, or assume that because I have not included
> every detail that I am somehow unaware of them. You would be wrong.)
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> The problem is in the size of "real" problems. You can argue all day
> about higher order modes, and appropriate boundary definitions. These
> have little relevance for a designer like Chris Cheng who is trying to
> implement real system boards that have hundreds of 3, 6, 10 Gbps
links,
> and the necessary thousands of single-ended DDR-XYZ memory signals to
> support those aggregated data rates, running at 533, 666, 1066, 1333,
> and 1666 Mbps in his future systems. Although Chris is quite capable
> of defining structures to model and simulate, and quite capable of
> performing the modeling himself, his problem is one of sheer time,
> volume and space.
>=20
> Chris' problem boils down to two very basic questions:
>=20
> 1) Is there a tool and methodology that can help to engineer a
reliable
> system, free of SI, PI and EMI problems, within his product
engineering
> time window?
>=20
> 2) If not, when do I know, how do I know, that I must spend the time
to
> run full-wave tools to characterize and define the localized boundary
> regions of the design?
>=20
>=20
> Charles, you have been sitting in the background, hiding in anonymity,
> throwing darts at Yuriy, when IMO they are unjustified. You would be
> well advised to be a professional, ask questions and clarifications,
> rather than make accusations. Please feel free to provide us with your
> experience and credentials, rather than questioning Yuriy's. It would
> help your credibility in my eyes.
>=20
>=20
> regards,
>=20
> Scott
>=20
>=20
>=20
> Scott McMorrow
> Teraspeed Consulting Group LLC
> 121 North River Drive
> Narragansett, RI 02882
> (401) 284-1827 Business
> (401) 284-1840 Fax
>=20
> http://www.teraspeed.com
>=20
> Teraspeed(r) is the registered service mark of
> Teraspeed Consulting Group LLC
>=20
>=20
>=20
> Charles Harrington wrote:
> > Chris,
> >
> > I completely agree with you. We need methods rather than just
validated
> tools.
> >
> > I disagree with Yuriy that a tool can define the boundaries of
> discontinuties and decompose the channel. If he still believe this is
> true, then he should name the tool.
> >
> > Channel decomposition is a very old and simple procedure to
impement.
> This I agree with Yuriy. But what Yuriy does not understand is that
you
> can do decomposition only when you have one dominant wave mode at
points
> or interfaces along the channel where you wish to do the
decomposition.
> Let me explain what I mean. If you have a stripline, competely
surrounded
> by a homogeous dielectric and losses can be neglected, then the TEM
> approximation can be used. Even if this stripline is as long as 1 km,
you
> can decompose it and use quasi-static or even static approximations to
> analyse the different segments. These segments can later be integrated
> together. But when ever you have higher order modes, then
straight-forward
> decomposition, which is implemented in most tools, fails. As Prof. R.
> Collins (field theory of guided waves) explains, once there are
> discontinuities, then the waves at the output of the segment
containing
> the discontinuity will have a combination of the dominant
> > modes (which you can competely characterize) and higher order modes
> (which you may not even know). These waves will then serve as incident
> waves to the second segment and so on. That's why in most tools, it is
> recommended to do decomposition only at points where the higher order
> modes have decayed. The user must define interfaces or points along
the
> channel where the higher order modes have decayed and only the main
mode
> (which propagates power) is present. This is one of the motivations
why
> boundaries of discontinuties are defined. So, don't rely on tools to
do
> channel decomposition whenever you have discontinuties at higher
> frequencies. Remember, at lower frequencies most of the effects of the
> highe order modes can be neglected.
> > I am sure no body in this list (including myself) will be able to
> propose you a solution much better than the one you proposed yourself
in
> your previous mail. Below, I will try to outline your methodology.
Please
> correct me, if I don't understand something.
> >
> > 1. Characterise the 3D geometies for your PCB technology considering
the
> return paths, plane stitches etc. at your frequencies of intertest.
You
> may consider the highest frequency. Whenever discontinuties are placed
too
> close to each other, then you consider them as one discontinutity and
use
> a 3D field solver to compute the fied solution.
> > 2. Use a statistical method to make sure you cover possible
dimensions
> of the 3D geometries (such as via pads, via holes, stitcing vias and
so
> on) and what-if scenarios.
> > 3. Place your design rules in a data base for your post route
> verification analysis.
> >
> > I think if you proceed as you proposed yourself, then you will not
> encounter any uncalculated discontinuity, because you define your
layout
> yourself. You can always localize any discontinuity you encounter. You
> just have to make sure that the return current is kept close to signal
> current. There is nothing new or difficult in this. Dr. Howard Johnson
in
> his book on advanced black magic explains this very well.
> >
> > I hope it helps. If not, I'm sorry, I can not help you further.
> >
> > Best regards
> > Charles
> >
> >
> >
> >
> >
> >
> > Chris Cheng wrote:
> > JP,
> > I have no beef in who has a better 3D algorithm. My question is
> specifically on methodology to both Charles and Yuriy in integrating
3D
> models in a system environment and I didn't find Yuriy pimping his own
> tool in his response to me. In fact I think his description is
somewhat
> closer to what Charles has been saying, there are non-localize models
one
> has to take into consideration.
> > I am just looking out from my short bus asking all the experts you
> mention to chime in. Namely, what is the correct methodology to
integrate
> 3D models in a complete system interconnect simulation environment.
> > As far as I know there are not that many brave souls that model the
> entire system interconnect in one big giant 3D full wave model from
end to
> end. That means at certain point of time the model is partitioned,
most
> likely between pure interconnect (lossy line) and discontinuity (3D
> models).
> > I think Yuriy correctly point out some of the cases are not
localizable
> and in those cases, what are you going to do ? What tool can tell me I
can
> safely break my trace read from the PC CAD database at what distance
> before I have to extract my 3D model (as in case a) on my original
> question)? What tool can precompute the discontinuity in 3D and then
> calibrate out the ideal interconnect part out of the extended port
> (probably by some kind of pseudo TRL algorithm) so that a user can
simply
> extract the trace length information from the PC CAD database and then
> just reuse the pre-compute 3D models everytime he encounter the
> discontinuity ?
> > To me, the second option is very attractive because it gives the
dumb
> user like me a very straight forward modeling methodology. All those
via
> drills and return models, plane switches can be pre-compute and
constrain
> in PCB design rules and the post route verification will be a snap by
> simply reading out the trace length and location of the discontinuity
and
> substituting the pre-compute model.
> > On the other hand, what if we hit one of those giant non-localize
> discontinuity ? What tool can fall back and extract the necessary area
and
> model ?
> > I am not an academic, I ship products. With that in mind, I need a
> methodology and not just a tool that can be validated to a terahertz.
> > ________________________________
> >
> > From: Jean-Pierre Maurice [mailto:mauricejeanpierre@xxxxxxxxxxxxxx]
> > Sent: Sat 12/1/2007 4:28 PM
> > To: shlepnev@xxxxxxxxxxxxx; Chris Cheng; ch_harrington@xxxxxxxxx
> > Cc: si-list@xxxxxxxxxxxxx
> > Subject: RE: [SI-LIST] Re: Signal crossing Split plane
> >
> >
> >
> > Yuriy,
> >
> > stop confusing yourself and others with lengthy emails and
explanations
> that have no proof.
> >
> > Which of the references you quote in the 40s or any other EM
principle
> warrants you to model discontinuities the way you do in your
application
> notes? I went through all the examples in your website using the link
you
> provided ( http://www.simberian.com/AppNotes.php) and realized that
you
> don't have even one example where you correlated your simulations with
> measurements. Why? Are you hiding something?
> >
> > At the beginning, Lee advised you to do some measurements. Charles
also
> said the very thing, but in a rather harder way.
> >
> > I may disagree with the way Charles pointed this out to you, but
there
> is a lot of truth in everything he said, especially regarding your
models.
> Indeed, the models in your application notes are not correct and also
> misleading, I would say. You make terrible claims about your solver's
> ability to compute complex multilayer geometries and yet provide no
> example to make your case solid.
> >
> > In the case of via-hole modeling; If you have now learned and agree
that
> via-holes are not just barrels and pads as you represent them in your
> notes, and if you now also agree that you need to be far away with
your
> ports, then why do you still have these unrealistic models in your
> application notes? You even go as far as posting them in this list. By
> doing so, you mislead the young and unexperienced. You even mislead
the
> users of your solver. If you claim that any of the models (multilayer
> geometries, slots, via, planes, transmission lines, etc) in your
> application notes is correct, then show us how they match with
measurement
> results.
> >
> > There are also a lot of weakness in the way you explain some
fundamental
> issues which do not reflect the 25 years of experience you claim to
have.
> Unlike Charles, I will not talk about that openly in this forum. May
be
> privately, if you permit me. You even forge explanations to justify
your
> solver and models. This is inappropriate.
> >
> > I am now on holidays. When I get back to work, I would like to
evaluate
> your solver using some of our multilayer geometries (if you provide me
the
> 3 day evaluation license you promise on your website). As long as I
don't
> see any good correlation with measurements and your simulation models
are
> also weak, then there is no way I can believe you.
> >
> > Chris: I don't think Yuriy is the person to ask questions concerning
> real PCB designs when he can not provide realistic examples in the
> application notes of his own solver. If you don't believe me, use the
link
> given above. Charles too is a bit impolite, I would say. There are a
lot
> of other well respected experts in this forum (Steve, Istvan, Lee,
Eric
> Bogatin etc) from whom I learn a lot. I think they will give you real
> answers, not some theory that does not help.
> >
> > Best regards
> > Jean Pierre
> >
> >
> >
> >
> > This email and any attachments thereto may contain private,
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