Re: NEC-LIST: 4nec2 LATEST. Patches

Ken,

Apologies if I have sent this twice, but I don't think it went first time!

A surface patch is indeed a patch, but NEC uses the Magnetic Field Integral
Equation for them and they can only be used to model completely closed
structures with non-vanishing volume. NEC patches model only the side of the
surface from which their normals are directed outwards and are not valid for
a conducting plate. MFIE does not allow anything that results in a field
inside the structure (e.g. gaps or non-perfect conductors). Incidentally,
NEC takes no account of the shape of the patch even though the SP command
does allow you to specify a shape and the co-ordinates of its corners. NEC
uses these just to determine the co-ordinates of the patch's centre and its
normal.

For wires NEC use the Electric Field Integral Equation and these can, with
care, be used to model thin plates and open structures.

Paul Carlier
FanField Ltd

Miron,
In nec, a surface patch is a patch, not a box. You can make it a box with 6
patches. Not sure though, how patches are treated in nec. They don't show
currents as in wires, but it does seem to reflect EM waves. Have not tried
to place a 1/4 wave wire inside a Patch Box to see if fields outside the box
couple to it. Would be a neat example to try.
How are dielectrics, other then ground plane, specified in nec? Or maybe
they can not be?
Thanks!
Ken Carrigan

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