To increase the sensitivity ofparabolic antennas, parabolic antennas with two reflectors were developed, the double reflector antennas. They consist of a main reflector and a subreflector.
In the double reflector antennas, the main reflector is a section of a paraboloid, as in other parabolic antennas. The main reflector reflects the microwaves onto the subreflector, which is located at the focal point of the main reflector. The subreflector can also be a paraboloid, but it can also be elliptical, or look like an angled reflecting wall. The subreflector focuses the received microwaves at the focal point where the LNB(s) are located.Cassegrain antenna or the Gregory antenna, which have the shape of a hyperboloid or a paraboloid. In addition, there are double reflector antennas that use a curved, obliquely oriented reflecting surface as a subreflector and have multiple focal points. In this design, the reflecting surface forms multiple reflection planes that have offset focal points. The focal points contain different LNBs for the different transmission frequencies of the geo-satellites.
Such double reflector antennas are designed for multiple subscriber systems and can receive German and various foreign programs from different satellites.