NEC-LIST: Wire Grids and the Wheeler Cap

>From the desk of Keith Lysiak
>
> In "PC's for AP and Other EM Reflections" in IEEE Antennas
> and Propagation Magazine, Vol. 39, No. 1, Feb 1997, Ed Miller
> performs a similar analysis (Wheeler Cap ?) in an innovative
> approach to determining "Wire-grid approximations to solid
> surfaces".

Although I had long known about the Wheeler approach for measuring
antenna efficiency and had been working with wire-grid models of solid
surfaces for many years, I didn't really make any connection between
them until seeing Keith's note. But the principle is the same, except
for my problem I wanted to confirm in still another way that the
"equal-area" rule for modeling a solid surface by a wire grid is
correct.

My Wheeler cap in this simple case was modeled using 8 or 10
2-wavlength-long parallel, equi-spaced wires on a circular surface
with a half-wave dipole located on the cylinder axis. The input
resistance of the dipole was obtained as the radii of the cage wires
was varied, and found to be minimized when the equal-area rule was
satisfied. Actually, the minimum resistance was slightly negative,
but I didn't regard this as invalidating the approach but instead an
indication of accurately modeling radiators with near-zero radiation
resistance.

Ed Miller

                    PLEASE NOTE MY NEW e-mail ADDRESS.

----------------------------------------------------------------------
Edmund K. Miller, PhD
3225 Calle Celestial
Santa Fe, NM 87501-9613
505-820-7371 (voice and FAX)
Received on Thu Apr 22 1999 - 17:41:44 EDT