[SI-LIST] Re: 2.5D

  • From: "Shawn Carpenter" <scarp@xxxxxxxxxxxxx>
  • To: "Zhou, Xingling (Mick)" <xlzhou@xxxxxxxxx>,<si-list@xxxxxxxxxxxxx>
  • Date: Fri, 14 Dec 2001 11:55:10 -0500

RE: [SI-LIST] Re: 2.5DMick:

I'll refer your questions regarding the history of the 2.5D term to Jim
Rautio, and let him reply to you offline.

I have the article:  J. C. Rautio, "Some Comments on Electromagnetic
Dimensionality", IEEE MTT-S Newsletter, Winter 1992, pg. 23. ?
I will email it to you, or to anyone else who is interested.



  -----Original Message-----
  From: Zhou, Xingling (Mick) [mailto:xlzhou@xxxxxxxxx]
  Sent: Thursday, December 13, 2001 9:09 PM
  To: 'scarp@xxxxxxxxxxxxx'; si-list@xxxxxxxxxxxxx
  Subject: RE: [SI-LIST] Re: 2.5D


  Thanks for the interesting historical infromation.
  Since I asked this question, I would like to discuss more.

  Looks like 2.5D always reminds us Momentum, or plannar structures in this
society. However, I have seen other non-plannar

  structures that are called 2.5D. For example, [1] IEE Proceeding-Micow.
Antenna Propag., vol.144, No.2, April, 1997,pp.81-89.

  and [2]IEEE MTT-43, No.11, Nov. 2600-2607., both papers discuss full wave
solutions of waveguides. The authors (even some others before them ) named
the problems 2-1/2D. I am not sure if it was borrowed. Obviously, the
geometry is traditionally 2D, unlike plannar structure. My understanding is
the z-component was "decoupled" from  x and y components, only the X-Y
problem (2D) is solved explicitly in the algorithm. However, the full wave
solution is different from static one. In static case, z-component is
independent of others, but not in the full wave solutions. So, the problem
is between a typical 2D (waveguide, or transmission line) problem and a real
3D problem in terms of fields. It was called 2.5D. Here D does not
necessarily mean geometrical dimensions, could be other physical dimensions
(such as fields, must be the same).

  I heard of psduo-2D problem from other disciplines. Is this similar to
what we discussed ? Any comments ?

  Regarding fractional dimensions, if we need to count the same dimension ?
I mean the quantities with the same physical dimension or physical meaning.
Or we can have mixed dimension such as the one mentioned in the story

  ((geometry (3D)+current(2D))/2=2.5) etc. ?

  BTW, who can provide me a copy (email or fax) of the paper J. C. Rautio,
"Some Comments on Electromagnetic Dimensionality", IEEE MTT-S Newsletter,
Winter 1992, pg. 23. ?  It must be an interesting articale.

  Best regards.


  -----Original Message-----
  From: Shawn Carpenter [mailto:scarp@xxxxxxxxxxxxx]
  Sent: Friday, December 07, 2001 3:12 PM
  To: si-list@xxxxxxxxxxxxx
  Subject: [SI-LIST] Re: 2.5D

  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
  that we are approximate when accuracy is our primary strength. Also, for
  open environment codes, I suspect that they might get pretty slow when
  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
  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
  were funding my Ph. D.) looked at the current and called it a 2-D
  Harrington looked at the fields and called it 3-D. To Harrington, 2-D
  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
  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
  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

  I wrote a short paper on this, discussing dimensionality and appropriate
  quantitative justifications of all common types of EM analyses a while
  (I think we had a short discussion about it, but that was a while ago,
  time flies!) will send you (and anyone else who wants it) a copy if

  J. C. Rautio, "Some Comments on Electromagnetic Dimensionality", IEEE
  Newsletter, Winter 1992, pg. 23.

  As far as I know, no one else in microwaves was using the term 2.5-D
  I pulled it out of fractal theory.

  As for vias not doing well when making a wall, that is because their
  in Sonnet (and most other planar codes) is not intended for that purpose.
  Specifically, Sonnet uses vias which are rectangular cylinders with
  current along their length flowing through the entire volume. They work
  well when transferring current from one layer to another (their intended
  purpose), but not nearly as well for making conducting walls. It is
  possible to design vias that would work well for making walls. (Actually,
  would require two kinds of vias, the first transfers current vertically,
  second horizontally, and you have two possible horizontal directions
  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
  all, but I realized early on that if you are going to get into that kind
  complication, you would get into big-time slow-downs for large circuits.
  I left that problem to the 3-D volume meshing codes, which they handle

  Dr. James C. Rautio
  Sonnet Software, Inc.

  (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


    2.5D usually refers to method of moments (MoM) codes for planar
    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
    currents on the via metal. So vias can couple to each other, but they
    to planar metal. One fallout from this is an analysis of shielding due
    "fence" of vias may not be accurate. Or using via metal to build an
    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
    function (or potential function) for the current distribution. So you
    place metal
    at arbitrary angles and there is no separate approximation for Z
    The down side may be a hit on solution time because the math is tougher.
    say for sure though because I have not benchmarked similar cases on
    codes lately. Have not tried the via fence problem on IE3D, should
    do that.


    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


            A simple but unclear (to me) question. What is the exact
    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
    academic references or support instead of "I think".



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