Dipole at a parabolic reflector focus

This example shows how to design a very simple parabola reflector. This reflector is illuminated with a dipole antenna. Even this structure may have no practical use, it presents how to use the parametric line utility in GiD.

To create the geometry it is more convenient to use the geometry=>create=>parametric line. The following settings will create a parabola line. The focal length will be 0.5 m and the focal point will be at the coordinates (0 0 0.5).

When this is done use copy under utilities with following options:

entities type : line
transformation : rotation
angle : 90°
1st point : 0. 0. 0.
2nd point : 0. 0. 1. (these two points define the normal, in our case the z axis was the direction of the pointing direction)
extrude : surfaces
multiple copies : 4 (90 x 4 = 360°; in GiD the mesh is built taking the lines as a support. Consequently a higher quality mesh is obtained when using a sufficient number of lines. That's why we are using 4 copies of the line instead of only 1)

To create the dipole, draw a line with the following points :

(-0.25, 0, 0.5)=>(0, 0, 0.5)=>(0.25, 0, 0.5)

The final geometry is displayed in the next picture :

Assign the interface properties over the surfaces and the antenna property over the wire.

Create a Voltage source at the middle point of the wire.

Choose a far field pattern.

Set the frequency (300 MHz, so that the dipole is a half wave dipole).

Collapse the model and repair it (optional, but recommended in most cases).

The computed surface currents. To switch to the wire currents, use the "Show Wire Currents" button in the 3D results window.

The computed far field pattern :