Han and Steve: Ground is another very interesting issue. Zero potential is at infinity. This leads to the problems we have when we mix of 2D and 3D models. 2D models need a close reference ground and 3D PEEC and other 3D models have their reference at infinity. For some mixed 2D and 3D problems we have to improvise the ground situation which is sometimes very difficult. As Han mentioned in the note below, a closed box is an example where we can use the box (at least one point on the box) as our ground since we are practically shielded from the outside. For open problems it becomes a more difficult issue depending on the details. Regards, Albert Albert Ruehli ruehli@xxxxxxxxxx 914-945-1592 TL 862-1592, Fax 914-945-4244 Bi Han <mike_bihan@xxxxxxxxxxxx> Sent by: si-list-bounce@xxxxxxxxxxxxx 09/24/2005 04:22 AM Please respond to mike_bihan To steve weir <weirsi@xxxxxxxxxx>, List` Si <si-list@xxxxxxxxxxxxx> cc Subject [SI-LIST] Re: What can we get from solid ground plane? Steve: It is a lot of fun and use to read your reply, because it always extend my questions and make me think more, and of course find that there is someting new to think about. Why I came up this question is that I used to hear a comment from a Optimal AE that in package design, the ground plane on the package substrate could be treated as reference ground. Another Agilent AE used to comment that in RF circuit, the metal box could be treated as ground reference. I want to dig out the theory behind, however, they did not give me satisfying answer. In my understanding, if the ground plane is very solid, all return current will not interfere severely between each other. Thus ground reduction could be meaningful. Otherwise, ground reduction will loose all information about Cross-talk through return path and becomes incorrect. I agree with you that solid ground plane is the basis of 2D solver. It is also the basis that we could do ground reduction, which makes transmission line equations/simulations meaningful. thanks, Han steve weir <weirsi@xxxxxxxxxx> £º Han, I think your life will be easiest if you look at a plane as a good reflector. Mapping the RLCG into the "other conductor" is a convenience that works reasonably well to reduce computations in things like 2D planar models. Sometimes it is fine, other times it leads to serious errors, as can occur in connector models. If you are talking about the effect the presence of a plane has on multiple signal lines, then "minimal" is perhaps inappropriate. A semi-rigid coax fits that description a lot better than a plane. For a plane, we are concerned with how far away each signal is from each other, and each from the plane. We can readily build constructions where the signal to plane coupling is weak, and the signal to signal coupling is anything but "minimal". Fortunately, such constructions are contrived and not very economical. Doug Smith has examples on his web site, such as parallel signals crossing a split. Steve. At 11:19 PM 9/23/2005 -0700, Bi Han wrote: >In papers, I often read "solid ground plane" concept. Some papers will >treat it as reference node. > >As I know, ground plane could not be treated as "ideal ground" no matter >how good/wide/thick it is. The assumption behind it could be different as >I will present my understanding below. > > From the view of EM modeling, this solid ground plane make "ground > reduction method" effictive and accurate. "ground reduction" means fold > ground plane RLCG into signal trace, thus ground plane could be treated > as ideal ground. > > From design view, the benefit I could see for now, is that solid ground > plane make each loop's mutual inductance minimal, thus minimize cross talk. > >Any different ideas? > >thanks, >Han > >--------------------------------- > ÑÅ»¢Ãâ·ÑGÓÊÏä£ÖйúµÚÒ»¾øÎÞÀ¬»øÓʼþɧÈų¬´óÓÊÏä > ÑÅ»¢ÖúÊÖ£ËÑË÷¡¢É±¶¾¡¢·ÀɧÈÅ > >------------------------------------------------------------------ >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: >//www.freelists.org/webpage/si-list > >For help: >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > >List FAQ wiki page is located at: > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > >List technical documents are available at: > http://www.si-list.org > >List archives are viewable at: > //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 > --------------------------------- ÑÅ»¢Ãâ·ÑGÓÊÏä£ÖйúµÚÒ»¾øÎÞÀ¬»øÓʼþɧÈų¬´óÓÊÏä ÑÅ»¢ÖúÊÖ£ËÑË÷¡¢É±¶¾¡¢·ÀɧÈÅ ------------------------------------------------------------------ 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: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //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 ------------------------------------------------------------------ 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: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //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