Cassegrain antenna

In telecommunication, a Cassegrain antenna is an antenna in which the feed radiator is mounted at or near the surface of a concave main reflector and is aimed at a convex secondary reflector slightly inside the focus of the main reflector.

Note 1: Energy from the feed unit illuminates the secondary reflector, which reflects it back to the main reflector, which then forms the desired forward beam.

Note 2: The Cassegrain antenna design is adapted from optical telescope technology and allows the feed radiator to be more easily supported.

Source: from Federal Standard 1037C