GB1419283A - Wide band width vertically polazized omnidirectional aerial - Google Patents

Abstract

1419283 Aerials MESSERSCHMITTBOLKOW-BLOHM GmbH 30 Nov 1973 [2 Dec 1972] 55711/73 Heading H4A A wide bandwidth vertically polarized omnidirectional aerial comprises a first conductive tubular element 12, Fig. 1a, in which is an annular group of slots 4 disposed around its periphery in a plane perpendicular to its axis. As shown, the slots are of uniform size and rectangular shape, but may alternatively be widened out from their centres, either uniformly or stepwise, or be of dumb-bell shape. Furthermore, the slots may have different lengths, in order to obtain a desired asymmetry in the radiation diagram. The element 12 is substantially #/2 wide (#=wavelength at the nominal operating frequency) and the annular group of slots divides it into two portions each #/4 wide. As shown, a co-liner array is formed by a number of elements 12, with narrow gaps 3 therebetween, but in another embodiment said gaps are bridged over, adjacent annular groups of slots then being #/2 apart (Fig. lb, not shown). Coaxially inside the tubular element (or elements) 12 are second and third conductive tubes 10 and 14, which together form a feed system for the aerial. Each slot is connected to said feed system by a symmetrical three-conductor arrangement 5, 8, 9, the outer conductors 8, 9 of which serve also to maintain the spacing between the tube 10 and the element 12. One end of the inner conductor 5 of each arrangement is connected to a lug 7 extending into the slot and its other end passes through an aperture in the tube 10 and is connected to the tube 14. Coaxial cables such as 15, 16 are contained in the tube 14 and are connected to it and to the tube 10 as shown in Fig. 2. Each cable is extended by means of a tube 20 and a rod 21, a transversely disposed hollow boss 20 of said tube passing through a bore in the tube 14 and being secured by a nut 24, whereby the two tubes are electrically connected. An internally threaded extension 26 from the rod 21 projecting into the hollow boss 20 is engaged by a bolt 31. A bush 28 has a flange 29 by means of which it is secured to the tube 10, through an aperture in which it passes. A portion 27 is of reduced diameter, and enters the hollow boss 20. The screw 31 is inserted through a central hole in the bush 28 and when tightened provides electrical connection between the tube 10 and the rod 21. An adjustable short-circuit plane is provided in the coaxial feed 20, 21 at a distance of about #/4 to facilitate matching. It is stated that the aerial is suitable for application to space vehicles.