[SI-LIST] Re: S parameters

  • From: "Alfred P. Neves" <al@xxxxxxxxxxxxxxxxx>
  • To: Hany Fahmy <hanymhfahmy@xxxxxxxxx>
  • Date: Sun, 27 Mar 2011 09:48:25 -0700

Confirming measurement with 3D EM is more complicated than you suggest, if I 
understand your post correctly.  I always question the integrity of 3D EM 
results by asking how where the materials property obtained, is the appropriate 
loss model utilized, and what level of benchmarking for simple known structures 
was established beforehand.  We find 3D EM correspondence to be very non 
trivial, and it gets exponentially harder as the frequencies increase.  

As a SI consultant, I would ask " how do you know your models work, and to what 
frequency"?   Many folks don't really know.  

On the measurement side before we address a difficult measurement, we always 
ask what is required, and how can we confirm the measurement with external 
tools, platforms, or verification vehicles.  For example, if you are testing a 
symmetric reciprocal structure, it makes sense to first measure  (either tdr or 
vna) a Beatty standard first, then analyze reciprocity and symmetry in the 
resulting s-parameter matrix.  S21 should equal s12, and s11 should equal s22 
if the test structure is indeed reciprocal and symmetric.   After doing this 
satisfactorily, then make you intended measurement. 


Btw, make sure you watch Mike Stienberger's video on PCB007 on not destroying 
you s-parameters, he reiterates my point.   Jim Bell also posted our last 
Designcon paper corresponding crosstalk, and jitter to 3D EM to our website.   
Authors included Teraspeed, LeCroy, and Simbeor.  The paper shows how well the 
prevalent jitter decomposition tools work.







Regards,
Alfred P. Neves
Director of Business Development
Wild River Technology LLC
www.wildrivertech.com

work 503 718 7172
mobile 503 679 2429

Sent from my iPad2

On Mar 27, 2011, at 6:03 AM, "Hany Fahmy" <hanymhfahmy@xxxxxxxxx> wrote:

> Agree Alfred that all times we should go hand-in-hand between 3DEM
> simulations n VNA measurements to find-out the delta if exists. 3DEM
> simulations also in ADS (Momentum for PCBs n Packages along with FEM n FDTD)
> can be used to check the measured VNA data. Not all times we correlate
> sims-2-lab to check the validity of the sims but also in such case below we
> use 3DEM tools to check the validity of measured data. 
> 
> -----Original Message-----
> From: Alfred P. Neves [mailto:al@xxxxxxxxxxxxxxxxx] 
> Sent: Saturday, March 26, 2011 7:31 PM
> To: Hany Fahmy
> Cc: Tayyab Rahimkhan Pathan; Nijagunamurthy, Hithesh (GE Intelligent
> Platforms); si-list@xxxxxxxxxxxxx
> Subject: Re: [SI-LIST] Re: S parameters
> 
> What is nice about the ADS approach is that a template can be
> established,which we used to confirm the integrity of TRL calibration
> results and published it in our 2008 designcon paper (it is on our website).
> 
> Recently however, we routinely use Simbeor for all internal S-parameter
> checking, in addition to our 3D modeling.  This tool quickly identifies
> passivity and causality problems, and also easily creates a rational compact
> model in the same process.   
> 
> Regards,
> Alfred P. Neves
> Director of Business Development
> Wild River Technology LLC
> 
> work 503 718 7172
> mobile 503 679 2429
> 
> Sent from my iPad2
> 
> On Mar 26, 2011, at 10:42 AM, Hany Fahmy <hanymhfahmy@xxxxxxxxx> wrote:
> 
>> Another simple n reliable method to deal with S-parameters is to use 
>> ADS engine. It deals reliably with S-parameters while enforcing 
>> passivity.
>> 
>> It leads all the time to reliable data if the measurements r done correct.
>> 
>> Hany
>> 
>> On 3/25/11, Tayyab Rahimkhan Pathan <Tayyab_Pathan@xxxxxxxxxxx> wrote:
>>> If you google "S parameters" you will get many useful articles Or 
>>> specify what information you are seeking about s parameters?
>>> - Tayyab
>>> 
>>> -----Original Message-----
>>> From: si-list-bounce@xxxxxxxxxxxxx 
>>> [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Nijagunamurthy, 
>>> Hithesh (GE Intelligent Platforms)
>>> Sent: Friday, March 25, 2011 10:30 AM
>>> To: si-list@xxxxxxxxxxxxx
>>> Subject: [SI-LIST] S parameters
>>> 
>>> I was looking for S parameter articles, but could not find much. Are 
>>> there any articles or notes on S-parameters for Digital circuits.
>>> 
>>> -Hithesh
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>> 
>> --
>> Sent from my mobile device
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