Rectangular Horn : Voltage source

First create the horn's geometry :

Create a plate :

First Corner : (0.09779, 0.048895, 0)

Second Corner : (-0.09779, -0.048895, 0)

Extrude it toward the Z axis, with a translation of 0.5. This will create the waveguide used to feed the horn. Don't forget to remove the original surface and its copy. Just keep the walls of the waveguide.

Create a second plate which corresponds to the horn's aperture :

First Corner : (-0.465, 0.375, 1.8)

Second Corner : (0.465, -0.375, 1.8)

When this surface is create, delete it and just keep its contour.

In preference, choose "Create a new point" and select "Never". This will help you to create lines between existing points. It is recommended to set this field back to ask after you created all the required lines.

Use the line creation to join the corners of the output of the waveguide with the corners of the aperture. These lines are the contour of the horn's walls. Fill this contour with thebutton in the GiD toolbar (also available at Geometry=>Create=>NURBS surface=>By contour). and by selecting the wall's contour.

In this first case, the source is a monopole. In order to compare the results with the next cases, a small part of waveguide is added. It contains the monopole and should create the correct guided mode at the input of the antenna. In fact, this part can be considered as a transition "voltage source" to "wave guide source". For simplification purposes, it is just a copy of the small waveguide create at the beginning of this case. Don't forget to close the end of this waveguide. The obtained geometry is presented in the previous figure.

Create the feeding monopole with a line from (0, 0.026105, -0.383) to (0, -0.048895, -0.383). It is a quarter wavelength monopole. Its distance form the end of the waveguide is also a quater wavelength, the considered wavelength is defined by the propagation characteristics inside a waveguide (this is a classical approach and will not be detailed here).

Check the normals orientation :

The normals to the different surface elements should be defined coherently

Assign interface's properties on the surface, an antenna property on the line, a voltage source and a short circuit at the junction between the wire and the guide.

Set the frequency (1 GHz in this example).

Select a near field grid to view the field at the aperture of the horn. The origin of the grid is the lower left point of the aperture. The U and V axis are in the plane of the aperture (OXY). Umax and Vmax are defined by the size of the aperture. The step between each point is set to a fraction of the wavelength (λ/10 here).

Select a far field pattern.

It may be of interest to use the collapse and repair functions in some cases

Collapse : Geometry => Edit => Collapse => Model

Repair : Utilities => Repair Model

Generate the mesh, save and run

Computed surface currents, with a display of the CPU time :

A view of the electric near field in the aperture of the horn :

Radiation patterns in the two main planes (phi=0° and phi=90°) :