## [SI-LIST] Re: What can we get from solid ground plane?

• From: steve weir <weirsi@xxxxxxxxxx>
• To: mike_bihan@xxxxxxxxxxxx, List` Si <si-list@xxxxxxxxxxxxx>
• Date: Sat, 24 Sep 2005 00:18:38 -0700

```Han, I think your life will be easiest if you look at a plane as a good=20
reflector.

Mapping the RLCG into the "other conductor" is a convenience that works=20
reasonably well to reduce computations in things like 2D planar=20
models.  Sometimes it is fine, other times it leads to serious errors, as=20
can occur in connector models.

If you are talking about the effect the presence of a plane has on multiple=
=20
signal lines, then "minimal" is perhaps inappropriate.  A semi-rigid coax=20
fits that description a lot better than a plane.  For a plane, we are=20
concerned with how far away each signal is from each other, and each from=20
the plane.  We can readily build constructions where the signal to plane=20
coupling is weak, and the signal to signal coupling is anything but=20
"minimal".  Fortunately, such constructions are contrived and not very=20
economical.  Doug Smith has examples on his web site, such as parallel=20
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=20
>treat it as reference node.
>
>As I know, ground plane could not be treated as "ideal ground" no matter=20
>how good/wide/thick it is. The assumption behind it could be different as=
=20
>I will present my understanding below.
>
> From the view of EM modeling, this solid ground plane make "ground=20
> reduction method" effictive and accurate. "ground reduction" means fold=20
> ground plane RLCG into signal trace, thus ground plane could be treated=20
> as ideal ground.
>
> From design view, the benefit I could see for now, is that solid ground=20
> plane make each loop's mutual inductance minimal, thus minimize cross=
talk.
>
>Any different ideas?
>
>thanks,
>Han
>
>---------------------------------
=CE=DE=C0=AC=BB=F8=D3=CA=BC=FE=C9=A7=C8=C5=B3=AC=B4=F3=D3=CA=CF=E4
=C9=A7=C8=C5
>
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