[SI-LIST] Re: 2.5D
- From: "Shawn Carpenter" <scarp@xxxxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Fri, 7 Dec 2001 15:11:31 -0500
FW: [SI-LIST] Re: 2.5DHi:
I'm posting this on behalf of Dr. Jim Rautio at Sonnet Software, Inc.
--Shawn Carpenter
Sonnet Software, Inc.
------------------
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Dan Swanson
Sent: Tuesday, December 04, 2001 1:25 PM
To: 'xlzhou@xxxxxxxxx'; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: 2.5D
Dan -- Noticed your comments. Just want to correct one misunderstanding,
Sonnet includes all coupling, via-to-via, via-to-X/Y, etc., to full
numerical (usually double) precision, leaving cell size as the only
significant approximation.
I worked quite hard on that one, wouldn't want people to get the wrong idea
that we are approximate when accuracy is our primary strength. Also, for the
open environment codes, I suspect that they might get pretty slow when there
are a large number of layers (say, 5-10), although I have no specific
knowledge there (I don't go around trying to do competitive benchmarks). I
have done circuits with over 1000 layers, and it is still primarily limited
by the matrix solve time.
As for 2.5-D, will tell you a story about that. As far as I know I
introduced the term back in 1984 when I was working on my dissertation. At
that time we did not have vias, just X-Y current. My friends back at GE (who
were funding my Ph. D.) looked at the current and called it a 2-D analysis.
Harrington looked at the fields and called it 3-D. To Harrington, 2-D meant
infinite lengths of waveguide, etc. Since my success depended on the good
will of both parties, and since I had just read a book on chaos theory (and
related fractal theory where fractional dimensionality is explicitly
defined), I compromised and called it a 2.5 - D analysis.
Shortly after that, I added vias and had full 3-D current and full 3-D
fields, just restricted to a planar dielectric. So I started, and continue,
to call it a 3-D planar analysis. However, I guess "2.5-D" sounds so cool,
it is often used equivalent to 3-D planar, even though it is hard to justify
quantitatively.
I wrote a short paper on this, discussing dimensionality and appropriate
quantitative justifications of all common types of EM analyses a while back,
(I think we had a short discussion about it, but that was a while ago, gosh
time flies!) will send you (and anyone else who wants it) a copy if desired:
J. C. Rautio, "Some Comments on Electromagnetic Dimensionality", IEEE MTT-S
Newsletter, Winter 1992, pg. 23.
As far as I know, no one else in microwaves was using the term 2.5-D before
I pulled it out of fractal theory.
As for vias not doing well when making a wall, that is because their design
in Sonnet (and most other planar codes) is not intended for that purpose.
Specifically, Sonnet uses vias which are rectangular cylinders with uniform
current along their length flowing through the entire volume. They work very
well when transferring current from one layer to another (their intended
purpose), but not nearly as well for making conducting walls. It is entirely
possible to design vias that would work well for making walls. (Actually, it
would require two kinds of vias, the first transfers current vertically, the
second horizontally, and you have two possible horizontal directions further
complicating matters, and it would have to be sheet current, not volume
current, and a linear change in magnitude and phase along the subsection
length would be required.) Entirely possible, with no new theory required at
all, but I realized early on that if you are going to get into that kind of
complication, you would get into big-time slow-downs for large circuits. So,
I left that problem to the 3-D volume meshing codes, which they handle very
well.
Dr. James C. Rautio
Sonnet Software, Inc.
rautio@xxxxxxxxxxxxx
(Dr. Rautio is out of the country for the next week. Responses or replies
will get to him in a week or so. ---Shawn)
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Dan Swanson
Sent: Tuesday, December 04, 2001 1:25 PM
To: 'xlzhou@xxxxxxxxx'; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: 2.5D
Mick,
2.5D usually refers to method of moments (MoM) codes for planar circuits.
You can have multiple, homogeneous dielectric layers and metal patterns
at each dielectric interface. You can also have via metal between planar
metal layers.
To save time and complexity, most codes solve for the XY currents on the
planar conductors and use a different, simpler approximation for the Z
directed
currents on the via metal. So vias can couple to each other, but they
don't
couple
to planar metal. One fallout from this is an analysis of shielding due to
a
"fence" of vias may not be accurate. Or using via metal to build an
isolation
wall in a package may not give the expected results.
Sonnet em, Emsite, Momentum, Ensemble fall into this camp.
The one commercial exception is IE3D from Zeland. They retain the full 3D
Green's
function (or potential function) for the current distribution. So you can
place metal
at arbitrary angles and there is no separate approximation for Z directed
currents.
The down side may be a hit on solution time because the math is tougher.
Can't
say for sure though because I have not benchmarked similar cases on
different
codes lately. Have not tried the via fence problem on IE3D, should
probably
do that.
Dan
Dan Swanson EMAIL: d.swanson@xxxxxxxx
Bartley RF Systems PHONE: 978-834-4085
37 South Hunt Road FAX: 978-388-7077
Amesbury, MA 01913
-----Original Message-----
From: Zhou, Xingling (Mick) [mailto:xlzhou@xxxxxxxxx]
Sent: Tuesday, December 04, 2001 10:36 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] 2.5D
Hello,
A simple but unclear (to me) question. What is the exact
definition
of "2.5D problems" ? If we search "2.5 D simulation", we can find some
products. Because the problem has been there for a while. Please advice
academic references or support instead of "I think".
Regards.
Mick
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