# [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. Thanks, --Shawn -----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 Hello, 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. Mick -----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 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 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: http://www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: http://www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu

**Follow-Ups**:**[SI-LIST] Re: 2.5D***From:*Mustansir Fanaswalla

**References**:**[SI-LIST] Re: 2.5D***From:*Zhou, Xingling (Mick)

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