A bowl-shaped aerial with a parabolic cross-section that reflects incoming radio waves to a focal point above the bowl; also known as a dish antenna. At the focal point is a collector known as a feed. High-performance parabolic antennas are often of the Cassegrain design, in which a secondary reflector directs radio waves to a focal point low down inside the bowl. The principle of a parabolic antenna is identical to that of the primary mirror in an optical telescope.