GB1126670A - Feed arrangement for ring-shaped antennae - Google Patents

Abstract

1,126,670. Aerials. ROHDE & SCHWARZ. 28 April, 1967 [29 April, 1966; 2 Aug., 1966], No. 19704/67. Heading H4A. An aerial comprises a ring-shaped main reflector 1, 2, Fig. 1, the surface of which is formed by the rotation of a parabola or other conic section about a central axis 3 which is parallel to the tangent at its vertex, a centrally disposed feed 6, a Cassegrain-type sub-reflector ring 8 (shown partly broken away), the surface of which is formed by the rotation of a curve, such as a hyperbola, about the axis 3. A plastics or other radiation transparent mast 4 supports the halves 1, 2 of the main reflector, said halves being interrupted over a central section 5 to permit radiation from the feed 6 to pass through to the sub-reflector 8. The said sub-reflector, which is con-focal with the main reflector, is supported therefrom by stays 9. The feed 6 may be a bi-conical aerial, or it may be constituted by crossed log-periodic aerials, or other omnidirectional aerial arrangements. In a second embodiment, the feed is a directional horn (16), Fig. 2 (not shown), which radiates upon a portion only of a sub-reflector ring (8), and scanning is effected by rotating said horn. Phase correction by means, for example, of a lens may be provided in the horn. In a third embodiment, a main reflector 1, Fig. 3, is formed as a half paraboloidal ring by division in a horizontal plane and is provided with an additional inner paraboloidal ring 11 which receives radiation directly from a feed 16, and projects it upon a sub-reflector ring 8.