Offset antenna
In the case of an offset antenna , also called an offset mirror , the parabolic reflector is a section of a paraboloid . The exciter (a horn antenna) and its holder are located outside of the main direction of radiation and therefore cannot negatively influence the antenna diagram through "shadowing".
The exciter radiates upwards into a parabolic reflector cutout and the lower half of the symmetrical paraboloid is not used. The remaining reflector surface is not circular, but elliptical, so that it is illuminated more evenly due to the offset of the exciter. Grooved horn radiators are mostly used as pathogens .
Offset antennas are mainly used in satellite broadcast reception systems with an offset angle of 25 °. The advantage of an offset antenna is that the reflector can be mounted almost vertically, despite a receiving direction that is typically around 30 ° upwards for Central Europe, so that no snow can accumulate on the reflector in winter, which would significantly impair reception .
literature
- Bernhard Krieg: Satellite TV Little theory, a lot of practice. 1st edition, Elektor Verlag GmbH, Aachen 1987, ISBN 3-921608-47-3