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Claude Fable 5 implemented capacitance checking at shape corners,

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after much discussion about the implementation.  Since it is not
exactly clear what the field lines do at corners, the implementation
depends largely on an unknown and presumably global constant
multiplier;  this has provisionally been set to 1 but needs to be
determined empirically with a field equation solver.  At least one
rational approximation suggests a value of pi/2 instead of 1.  The
corner capacitance can be considered a refinement of existing
parasitic capacitance extraction, and since it takes a non-trivial
additional amount of computation, it is left as an option to
"extract" that can be turned on when a more accurate result is
preferred at the expense of a longer extraction time.
This commit is contained in:
R. Timothy Edwards
2026-07-08 09:13:07 -04:00
parent 443045b331
commit 718e02ec3f
7 changed files with 891 additions and 11 deletions
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doc/html/extract.html
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@@ -45,6 +45,26 @@ Circuit netlist extractor
<DT> <B>coupling</B>
<DD> Extract the parasitic coupling capacitance between
nodes.
<DT> <B>corners</B> [<I>value</I>]
<DD> (Added in magic version 8.3.672) Extract the fringe
capacitance at the corners of shapes. The fringe
capacitance model measures capacitance outward from
shape edges, which does not account for the part of
the fringe field at a convex corner that couples to
shapes diagonal to the corner, or for the
double-counting of the fringe field from the two
edges meeting at a concave corner. With this option
enabled, the corner fringe capacitance is modeled as
a superposition of the fields of the two edges
meeting at each corner, and is added to (convex) or
subtracted from (concave) both the substrate
capacitance and the coupling capacitance.
The optional <I>value</I> (default 1.0) is a
dimensionless scale factor on the corner capacitance
model. This is a second-order correction which
increases extraction time, so it is disabled by
default, and is not included in the options enabled
by "<B>all</B>".
<DT> <B>lumped</B>
<DD> Extract lumped resistance values.
The values extracted are "lumped" resistance and