4nec2x

I'd like to say hi to everybody.

I am using NEC2 to estimate scattering from a large metallic structure. My problem is that there is seemingly a difference of square root of 2 between the apparent near-field assymptotic behaviour and the far-field value.

I am assuming the following:
NEC far-field output, "Rp" is RCS/(lambda^2) (from nec manual)
NEC near-field output, "Ne" is linear field strength amplitude [V/m]

As I am not specifying the amplitude of the incident plane-wave, I am assuming that the near-field value is against some reference, for instance 1 V/m.

then for r -> infinite
|Ne| = sqrt(RCS/(4*pi*r^2))
=[1/(2*r)]*sqrt[(Rp*lambda^2)/pi]

But, as I said, when I run NEC and plot the results, I get a factor of sqrt(2) that doesnt fit in the equation...

with regards
knut

I've used the 4NEC2 to analisze filar antennas. Are You sure that the 4NEC2 uses RMS voltages instead Peak voltages!?

However, if You see that mistake, try to correct the value of voltage, to compensate the square-root (a trick who can simply resolve your problem)!

Good Luck!


P.S. Look at these Documents (in Italian) about examples on 4NEC2, wrote by my friend Dr. Andrea Serra

http://www.ing.unipi.it/~o1443499/Fi...imentale_1.pdf