[SI-LIST] Re: Connector model using 2D/3D field solver
- From: steve weir <weirsi@xxxxxxxxxx>
- To: bratfest@xxxxxxxxxxxxxx, <esayre3@xxxxxxxx>, <darshanmehta2k@xxxxxxxxx>
- Date: Wed, 24 Aug 2005 19:12:16 -0700
Gus, I think the key is to first determine how accurate a model or
measurement needs to be to be meaningful, and then set-out to meet that
target.
I would rephrase your "general agreement" statement into:
1. Measurement and models are always limited. ( Machine aided
hallucinations. )
2. We need to define the required accuracy before we model or measure.
3. We need to use a modeling and/or measurement method that can meet the
required accuracy.
4. Correlation is meaningful only within the accuracy limits of each the
model and the measurement.
5. Peer review can be an important arbiter of hallucination versus reality.
The corollary to 3. is that if we define an unreasonable accuracy target,
we aren't going to get useful results. OTOH, problems with gross margins
can be modeled on the back of a napkin. A skilled practitioner will not
waste time developing overly complex measurements and/or models. Neither
will they accept gross results that lack sufficient accuracy as conclusive.
I think a great point that you make is that correlation doesn't guarantee
correct results. A faulty understanding of the science can lead to: a
defective model, a defective test, and incorrect interpretation of the
two. Pons and Fleischman are our generation's poster children for that
lesson. Early peer review might have saved them and their management a lot
of embarrassment.
Regards,
Steve.
At 08:21 PM 8/24/2005 -0500, bratfest wrote:
>The "done properly" part is key... Sometimes (always??) it is not
>possible to remove 100% of the fixture effects from a measurement. On
>top of that.. how does the measurement system effect current flows and
>the like as relative to the overall system??? Think about this for a
>bit... think where are the fields of propagations different between the
>device under test and the application...
>
>Then try to wrap your head around the options that may be available in
>simulation.
>
>Think about this .. Is it possible to make a model that will "agree"
>better with a measurement... but not agree well in estimation of system
>performance??? Is it possible to make a model that will "agree" well in
>a system analysis... but not do well when comparing to a measurement?
>The answer is "yes" to both.
>
>On the other side, it can be tricky to model... start think about how
>the modeler works with wave fronts, port definitions, numerical
>resolution, etc... aauuggghhh
>
>Throw in the other assumptions about the test... homogenous PCB
>losses... exact symmetry in all traces, etc. Oh boy... it is
>difficult... many variables...
>
>Of course this all depends on ones definition of "correlated"... But
>basically... correlation between components models and component
>mesurements can become very acedemic very quickly... i.e. It is very
>easy to turn the "modeling to measurement" stuff into a science
>project...
>
>But all is not lost... A couple points to remember..
>* It is JUST a model ...yes, there will be approximations
>* It is JUST a measurement... there will be measurement error
>* The best that can be hoped for is "general agreement between methods"
>as a definition for "correlation"
>* ESTIMATION (not absolute knowledge)of system performance is the goal.
>* Measurements make your model better... but modeling also makes your
>measurements better.
>* Science is fun, but making product pays the bills.
>
>In the end, it does require a lot of time and effort... typically 2
>years of very directed work with an expert in the lab and a year behind
>a simulator with an expert can get you "fluent" in the aspects of
>passive component modeling and measurement per each domain. To become
>"conversational" it takes a lot less time.... but you will miss a lot of
>the details.
>
>Best Regards,
>Gus
>
>
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
>On Behalf Of Ed Sayre III
>Sent: Monday, August 22, 2005 11:39 AM
>To: darshanmehta2k@xxxxxxxxx
>Cc: esayre3@xxxxxxxx; si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: Connector model using 2D/3D field solver
>
>
>Darshan,
> You can simulate just about anything.... The trick is to know if the
>
>results are correct or not. A measurement, done properly, is always the
>
>Gold standard to which everything else is compared, not the other way
>around. An accurate model and modeling strategy is the key to
>extrapolation into areas of technology advancement If you are really
>interested in this understanding how a model gets built check out
>Scott's
>webinar stuff as suggested by Steve. Or get a demo version of the
>software
>and take the tutorial.
>
>-Ed
>
>
>
>
>
>At 06:11 AM 8/22/2005 -0700, Darshan Mehta wrote:
> >Hi Ed,
> >
> >
> >
> >Thanks for the suggestion. Even I was also thinking to contact the
> >vendor
> >to get the model, but I want to learn how they make model. But looks
>like
> >it may require lot of effort and time. How can we check whether the
> >S-Parameter extracted from the tool is accurate? Do you compare the
>Tool
> >results with the result at actual Hardware using Oscilloscope?
> >
> >
> >
> >Is there any other method to model a connector?
> >
> >
> >
> >Thanks,
> >
> >Darshan Mehta
> >
> >
> >Ed Sayre III <esayre3@xxxxxxxx> wrote:
> >
> >Darshan,
> >This is not a trivial thing and neither is the cost and training time
> >for the software you will need. Some of the players are CST, HFSS, and
> >ADS. It will take a few months, minimum, to go from install to
> >meaningful and accurate models. I would suggest that a better course of
>
> >action is to contact the connector vendor and ask for the models. If
> >unavailable it may be faster and likely cheaper to design and build a
> >test fixture for making measurements. Another alternative is to hire a
> >firm/consultant to build the connector models and extract the
> >s-parameters.
> >
> >Good luck
> >
> >-Ed
> >
> >
> >
> >At 05:16 AM 8/22/2005 -0700, Darshan Mehta wrote:
> > >Hello Everybody,
> > >
> > >
> > >
> > >I want to model a connector and I have got the information that we
> > >can extract the S-Parameter using 2D or 3D field solver to model the
> > >Connector (I am not sure about any other method to model a connector,
>
> > >probably you can suggest me). I have found some free 2D/3D field
> > >solver on net but I am not sure how accurate it will be. Could you
> > >please suggest me some 2D or 3D field solver?
> > >
> > >
> > >
> > >I have downloaded MEFiST 3D field solver which gives S-Parameter
> > >values but I am not sure whether I will get the accurate results.
> > >
> > >
> > >
> > >Thanks,
> > >
> > >Darshan Mehta
> > >
> > >
> > >
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