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At a parallel junction, we set the selfloop admittance to zero, and the admittances of the branches leading away from a parallel junction at grid point to be identical, thus
and set
The positivity requirements on
and
force us to choose

(4.75) 
Thus we have a simple CFLtype bound on the space step/time step ratio, which must be chosen greater than times the maximum value of the local group velocity
over parallel junction locations
. The bound (4.63) converges to
, as defined by (3.68), in the limit as the grid spacing becomes small.
Next: Type II: Currentcentered Mesh
Up: The Waveguide Mesh
Previous: Losses, Sources, and Spatiallyvarying
Stefan Bilbao
20020122