## Antenna Scatterers Analysis Program

# Source Code Description:
Subroutine GFF

**GFF**

**PURPOSE: ** to calculate the far-zone field of a sinusoidal electric monopole.

**METHOD: ** If an electric line source has length d and endpoints at (x_{1}, y_{1}, z_{1}) and (x_{2}, y_{2}, z_{2}), then the coordinates of any point on the source are

x = x_{1} + l cos(x)

y = y_{1} + l cos(y)

z = z_{1} + l cos(z)
where cos(x), cos(y), cos(z) are the direction cosines of the l axis, and l is the distance along the source measured from the endpoint (x_{1}, y_{1}, z_{1}). Let the current distribution on the monopole be:

Where I_{1} and I_{2} are the endpoint currents. The far-zone field of this source is:

where

and are the spherical coordinates of the observation point.

In this subroutine the range dependence has been suppressed. The far field vanishes in the endfire direction where GK=0. If a ground plane is present (IGRD > 0) the E_{1} equation above is decomposed into the x, y, and z components and the reflection coefficients are applied before E_{q} and E_{f} field components are returned to the calling program.

CALLED BY:

CALLS TO: NONE

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Last modified on:
3 Nov 2007
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