Sub-reflector for directional horn aerial - has auxiliary conical element adjustably mounted by threaded stem on suitably curved outer face of sub-reflector

摘要

The subreflector for a horn aerial has a conical element (4) mounted at the centre of the curved face (3) which faces the interior of the parabolic curve of the aerial and the horn radiator at the centre. This conical element is mounted on an externally threaded stem (5) so that it may be adjusted towards or away from the outside surface of the curved face. The threaded stem fits into an internally threaded bush (6) projecting away from the interior of the subreflector. The ratio of the diameter of the cone, to that of the subreflector is between 0.07 and 0.2. The distance (a) between the edge of the cone and the subreflector when divided by the wavelength of the operating frequency is 0.25. The subreflector can be a hyperbolic, parabolic or elliptical shape, and is calculated to give optimum electrical properties.