Sonnet User's Guide - Sonnet Software

Chapter 3 Subsectioning
Chapter 3
Subsectioning
The Sonnet subsectioning is based on a uniform mesh indicated by the small dots
in the project editor screen. The small dots are placed at the corners of a “cell”.
One or more cells are automatically combined together to create subsections. Cells
may be square or rectangular (any aspect ratio), but must be the same over your
entire circuit. The cell size is specified in the project editor in the Box Settings dialog
box which is opened by selecting Circuit ⇒ Box. The analysis solves for the
current on each subsection. Since multiple cells are combined together into a single
subsection, the number of subsections is usually considerably smaller than the
number of cells. This is important because the analysis solves an N x N matrix
where N is the number of subsections. A small reduction in the value of N results
in a large reduction in analysis time and memory.
Care must be taken in combining the cells into subsections so that accuracy is not
sacrificed. Em automatically places small subsections in critical areas where current
density is changing rapidly, but allows larger subsections in less critical areas,
where current density is smooth or changing slowly.
However, in some cases you may wish to modify the automatic algorithm because
you want a faster, less accurate solution, or a slower, more accurate solution, than
is provided by the automatic algorithm. Also, in some cases, you may have knowledge
about your circuit that the software does not. For example, you may know
that there is very little current on a certain area of your metal. Or you may have
chosen a small cell size because you have a small dimension in your circuit, but
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