[SI-LIST] Re: surface roughness
- From: Brian Rautio <brian@xxxxxxxxxxxxxxxxxx>
- To: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>, "<colin_warwick@xxxxxxxxxxx>" <colin_warwick@xxxxxxxxxxx>, "scott@xxxxxxxxxxxxx" <scott@xxxxxxxxxxxxx>, "twesterh@xxxxxxxxxx" <twesterh@xxxxxxxxxx>
- Date: Wed, 23 Nov 2011 02:32:39 +0000
Gentlemen,
First, I want to disclose that I have a PhD fellowship funded by Sonnet
Software. I will try to be unbiased in my views presented but I certainly
encourage fair skepticism.
There are two seemingly different ideas being discussed in this thread that I
would like to discuss my views on. First, there is mention that a macroscopic
model of the entire dielectric/metal combination is better and/or sufficient
for use over a microscopic model of individual components (e.g. "spheres" of
metal along the surface). Second, there is mention that microscopic models
generally don't present phase data and thus are not guaranteed accuracy.
I believe that both of these things are real issues, but also that they are
very much intertwined. First, if one finds a macroscopic model entirely
sufficient for their work, then I agree that there is little need to move to a
microscopic model. Second, if a microscopic model does not include sufficient
data to improve the result of a simulation [e.g. lacking phase as mentioned],
then this also leaves room for a macroscopic model to be better. I am
personally no stranger to macroscopic modeling--my M.Sc. Thesis was work to
'absorb' the effects of different fiberglass weaves as a macroscopic uniaxial
anisotropy. However, I was unable to absorb surface roughness into the
macroscopic dielectric model. This is often incorrectly attempted by changing
velocity of propagation through the dielectric to counter the effects of
increased surface inductance.
That said, there has been some recent ground breaking work by a collaboration
of Al Horn from Rogers Corporation and Jim Rautio from Sonnet. The main
discovery that they made is that surface roughness is modeled effectively in
situations where other models fail, by adding more inductance than would
generally be expected. They have several publications on this, notably winning
the best paper award for DesignCon 2010. I invite you all to read their IMS
paper, and specifically refer you to Fig. 7. for a wonderfully simple visual
explanation.
http://www.sonnetsoftware.com/support/downloads/publications/IMS2010_Roughness.pdf
Thank You,
Brian
On Nov 22, 2011, at 6:45 PM,
<colin_warwick@xxxxxxxxxxx<mailto:colin_warwick@xxxxxxxxxxx>>
wrote:
Hi Scott,
No worries. I guess we'll just have to agree to differ. We couldn't get a good
correlation with Hammerstadt using measured microscopic parameters, which
suggest to me at least that any macroscopic fit is fortuitous.
"The best model for a cat is a cat. Preferably the same cat."
Rosenblueth and Wiener, The Role of Models in Science. Philos Sci.
1945;12:316-321.
;-)
Cheers,
-- Colin
-----Original Message-----
From: Scott McMorrow [mailto:scott@xxxxxxxxxxxxx]
Sent: Tuesday, November 22, 2011 4:46 PM
To: WARWICK,COLIN (A-Americas,ex1)
Cc: si-list@xxxxxxxxxxxxx<mailto:si-list@xxxxxxxxxxxxx>;
twesterh@xxxxxxxxxx<mailto:twesterh@xxxxxxxxxx>
Subject: Re: [SI-LIST] Re: surface roughness
Colin
Not ganging up on you at all. Just ganging up on the fact that the
"Intel/Huray" approach of performing this level of microscopic detailed
modeling is gross overkill. I'd certainly love to see good complex
correlation of both magnitude and phase for the Huray model in a
simulator. But, it's just not necessary, having done hundreds of models
correlated with measurements using the Djordjevic-Sarkar model combined
with the Hammerstadt-Jensen model (or other macroscopic model).
Scott
Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax
http://www.teraspeed.com
Teraspeed(r) is the registered service mark of
Teraspeed Consulting Group LLC
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