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.
The Parabolic antenna is a high-gain, reflector antenna used for radio, television and data communications, and also for radiolocation (RADAR), on the UHF and SHF frequencies.
This antenna is typically a low-gain type such as a half-wave dipole or a small waveguide horn.
In more complex designs, such as the Cassegrainantenna, a sub-reflector is used to direct the energy into the parabolic reflector from a feed antenna located away from the primary focal point.