RE: NEC-LIST: Antenna pattern distortion modelling

Deb Chatterjee wrote:
> I have run the NEC-BSC3 (containing UTD formulations). The code is
> ...
> The code seems, in my view, the only solution to modeling of "antenna
> pattern distorions by neighboring structures" for structures about a
> wavelength or greater.

I have recently been trying to do just that, with the method of
moments. It requires millions of elements and, therefore, a
matrix-free iterative solver (with NEC, I can use at most about 7000
elements).

--- A TEST CASE ---

I would like to compare the methods. I have calculated a test-case
consisting of a square plate (1 x 1m), with a 1 GHz wave hitting it in
the normal direction. I looked at the field at 10 cm behind the center
of the plate. I did the same for a disk of 1m diameter. Results:

  Ex [V/m] = -.0667 + 0.1951*i +- 0.0002 <-- for the disk

  Ex [V/m] = 0.???? + 0.????*i +- 0.00015 <-- the square (secret!)

where the incident wave is polarized in the x-direction and has phase
exp(I*k*z), with the origin of the coordinate-system in the center of
the square (or disk). The error is based on Richardson extrapolation,
using up to 2097152 degrees of freedom in the solver.

Since this situation corresponds to a (receiving) antenna with its
view almost completely blocked by the square in front of it, NEC-BSC3
might be able to compute this.

I would like to compare my result to that of other methods, especially
if these other methods also give error bounds! To make the test more
interesting, I only listed my results for the disk, not for the
square, but they are known, I have mailed them to <davem_at_ece.ubc.ca>.

I hope more people will be interested in accuracy tests like this one,
since estimating accuracy is often a problem with EM codes.

Cheers,
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