Source Code Description: Subroutine GNF

GNF

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

METHOD: An electric line source is located on the z axis with endpoints at z₁ and z₂ as shown in the above figure. Let the electric monopole have the following current distribution:

where I₁ and I₂ are the endpoint currents, g is the complex propagation constant of the medium, d = z₂ - z₁ is the source length. The cylindrical components of the field are E(q) = 0 and

where h is the intrinsic impedance of the medium and where (r,f,z) denotes the cylindrical coordinates in a coordinate system centered at the endpoint of z₁.

These expressions exclude the field contributions from the point charges at the endpoints of the line source, since these charges disappear when two monopoles are connected to form a dipole.

Let the coordinate s measure distance along the test monopole with the origin at (XA, YA, ZA). From any point X,Y,Z a line is constructed perpendicular to the monopole. SZ denotes the s coordinate of the intersection of this line with the monopole. The length of the line is the radial coordinate r and RS denotes r². R1 and R2 are the distances from (XA, YA, ZA) and (XB, YB, ZB) to the point (X, Y, Z). In the statements above statement 1, the above equations are solved; and after statement 1, the cartesian components (E_x, E_y, E_z) of the field are determined. If a ground plane is present (IGRD>0) the reflection coefficients are applied to the cartesian components before returning to the calling program.

CALLED BY:

• GNFLD

CALLS TO: NONE