Cassegrain Reflector

To create a Cassegrain Reflector antenna, select Source > Reflectors > Cassegrain Reflector from the menu bar, or issue the command cassegrainReflector on the command line.

Figure 1. Cassegrain reflector menu item.

This will display the Cassegrain Reflector panel, used to create these reflectors.

Figure 2. Cassegrain Reflector panel.

The following options can be given:

  • Position the coordinates for the Cassegrain center. This is the geometrical point that will be used as a reference when the Cassegrain reflector is created. The center is located at the vertex from the main paraboloid reflector.
  • Diameter this sets the diameter for the main paraboloid. This value sets the diameter of the circular projection of the main paraboloid reflector.
  • Focal length this sets the focal length for the main paraboloid.
  • Feed height this sets the height of the feed point. It is described as a height above the position center; so, as an example, if the position is (x, y, z) and the feed height is p, the actual feed point will be (x, y, z+p).
  • Height this is the height the secondary hyperboloid reflector will be placed.

Additionally, the user is able to select if they want to create a front-fed Cassegrain reflector or an offset-fed one. By default, a front-fed Cassegrain reflector system will be created, and by checking the "Offset-fed" option the user can create an offset-fed Cassegrain reflector.

Figure 3. An offseted Cassegrain reflector and a simple Cassegrain reflector.

There are two ways of creating an offset-fed Cassegrain reflector:

  • Circular shape Selecting this option will cause the sub reflector to have a circular projection on the XZ plane. This mode of creating the reflector requires an additional parameter the separation (also called D'), along the X axis, between the left border of the main reflector and the vertex of the paraboloid it is extracted from.
  • Custom shape This option allows the user to customize the shape of the main reflector (and consequently, the shape of the secondary reflector) by selecting a closed set of curves that define the projection of the main reflector on the XZ plane. To do this, the user needs to select the "Custom shape" option, select the set of curves and press the "Select curves" button (the preview will be updated if the selected curves are adequate).

In order to create the geometry of the Cassegrain reflector system, the user needs to press the "Save" button.