GB1384677A - Reflecting antenna primaryl for the ghz bands - Google Patents

Abstract

1384677 Aerials GRUNZWEIG & HARTMANN UND GLASFASER AG and ROHDE & SCHWARZ 17 Aug 1973 [19 Aug 1972] 39067/73 Heading H4A An aerial comprises a main reflector made from synthetic resin with an electrically conducting surface, with a drive system which is mounted in the region of the pole of the main reflector and which is mechanically and electrically connected through a rod-like waveguiding member to an auxiliary reflector mounted in the region of the focus of the main reflector. The auxiliary reflector, wave-guiding member and drive system form a separate unit capable of being mounted on, and detached from the main reflector through an opening provided for this purpose in the main reflector in the region of its pole. When the unit is in place the opening in the main reflector is closed by a plate having a reflecting surface which is flush with that of the main reflector. A first embodiment comprises a paraboloidal main reflector 1, Fig. 1, made of synthetic resin with a rearwardly-extending cylindrical housing 2, stiffening rim flange 7, and (optionally) stiffening ribs 8. The rear end of the housing 2 is closed by a wall 4 having a central hole 16. The front end of said housing is open and receives a drive circuit 10 and a plate 5 of a feed unit 13, said plate being received in a recess in the main reflector, and being registered by dowels 14. The plate 5 is made of the same material as the main reflector 1. Its surface is a continuation of that of the main reflector, and both surfaces are coated electrolytically with a metallic layer 6. An extension 15 at the rear of the drive circuit 10 projects through the hole 16 and is engaged by a securing nut 17. The feed unit 13 also comprises a cylindrical waveguide 20 extending towards an auxiliary reflector 22, which is in the form of a metal disc, and which is located near the focus 12 of the main reflector 1. The waveguide 20 supports the auxiliary reflector 22 by means of an insulating spacer 21 and is soldered to the coating 6 where it passes through. A radome 29 may be provided, and a protective layer of synthetic resin may be formed on the reflective coating 6. The aerial may be attached to a mast by means of a clamping bracket 30. In a second embodiment, the rear end of the housing 2, Fig. 2, is open to receiving a large diameter securing ring 18, and the plate 5 is of smaller diameter than in the first embodiment. A round rod 23 of synthetic resin extends towards the focus 12, and terminates in a mushroom shaped head 26, of no greater diameter than the plate 5. The face 24 of the head 26 is of substantially paraboloidal shape, with focus 12, and is conductively coated, as is the surface of the rod 23. The other face of the head 26 is substantially spherical shape, with centre 12, and is provided with grooves or blind holes 27 to improve matching. A mixer diode 28 may be provided at the other end of the rod 23.