Re: NEC-LIST: Modelling Slots with MOM codes

Roland Mueller wrote:
>
> Hello,
>
> I am trying to model a rectangular slot antenna using a MOM type of
> program. How would I feed the slot to work with a magnetic current

Are you thinking about using Babinets principle? It would mean:
1) Instead of the slotted plane you take a flat strip in empty space.
2) The TOTAL electric field of the strip is the SCATTERED magnetic
     field of the slotted plane, times Z_0 (wave impedance).
3) The TOTAL magnetic field of the strip is the SCATTERED electric
     field of the slotted plane, divided by minus Z_0.

For more details look it up (in Jackson, for instance.) The advantage
is of course that modelling a strip requires less elements than
modeling an infinite plane with a slot :-) If it is a narrow strip,
you can even approximate it by a thin wire (diameter one half of the
strip width.)

If you just want to stick with the slot, then you could still use
Babinets principle as a guideline to find a good excitation. For
instance, a strip, just like a straight wire, might be excited by
a small current loop beside it, so the slot would require a
magnetic current loop (center line of slot running in the plane
of the loop).

Also: applying a voltage over the gap (at several points if you
want) is equivalent to forcing a current in the strip (or wire) at
these points, in the Babinet-transformed case, with the rule:
  V_gap = 1/2 Z_0 I_wire

Greetings,
Jos

--
Dr. Jozef R. Bergervoet                      Electromagnetism and EMC
Philips Research Laboratories,             Eindhoven, The Netherlands
Building WS01                                     FAX: +31-40-2742224
E-mail: bergervo_at_natlab.research.philips.com    Phone: +31-40-2742403