ANTENNA DEVICE

摘要

A disk-shaped reflecting plate 3 for reflecting an electric wave emitted out of an aperture 1a of a circular waveguide 1 is placed at a location which is just opposite to the aperture 1a of the circular waveguide 1, and a ring-shaped waveguide 4 for shaping the radiation characteristic of the electric wave reflected by the disk-shaped reflecting plate 3 to a rotational symmetrical radiation characteristic is disposed around the perimeter of the disk-shaped reflecting plate 3. Thereby, even when many grooves 4a need to be formed in order to make the electric wave have a rotational symmetrical radiation characteristic, it is not necessary to increase the size of the disk-shaped reflecting plate 3 in the direction of its radius. For this reason, the existence of the subreflector does not increase the side lobe level, and does not cause any reduction in the gain, and hence high gain can be achieved, reduction in the cross polarization can be made, and reduction in the side lobe level can be made.