GB749303A - Antennas - Google Patents

Abstract

749,303. Aerials. STANDARD TELEPHONES & CABLES, Ltd. (Federal Telecommunication Laboratories). Oct. 24, 1951, No. 24815/51. Class 40 (7). An antenna for producing substantially circularly polarized waves comprises a plurality of antenna elements forming a substantially closed figure in a given plane capable of producing waves polarized in that plane, other antenna elements co-operating with the first antenna elements capable of producing waves polarized in a plane perpendicular to the first plane, and a pair of metal plates between which the elements are all located for producing a quadrature phase relation between the electric fields of the waves from said elements. A complete aerial may comprise three stacked units 1, 2, 3, supported by a tubular metal mast 29 which may be used as the outer of a coaxial feeder for the aerial. The first antenna elements of each unit may comprise horizontal dipole elements 5a, 5b, 6a, 6b, 7a and 7b, each of which forms part of a circle gapped at 11, 12, 13, 14, 15 and 16 and supported from central metallic hub 4 by means of arms 8a, 8b, 9a, 9b, 10a and 10b. The elements 5a, 6a and 7a have threaded therethrough bolts 17, 18 and 19 which extend inwards through holes in the hub 4 and mast 29 to make contact with, or capacitatively couple to, the central conductor 23 of the feeder. Each of the horizontal dipole elements has attached to it (through the holes shown in Fig. 2) a pair of vertical dipole elements symmetrically arranged with respect to the axis of the unit and preferably a quarter wavelength long. Rigidly fastened to the mast on each side of the antenna elements are annular members 31, 32, 33, 34 supporting circular metal plates 35, 36, 37, 38. The vertical spacing and diameter of these plates is chosen so that the vertical and horizontal electric field components are at 90 degree phase difference in the case of each unit 1, 2 and 3; the space between the plates acting as a wave-guide. More or less than three circular dipples may be used to form the first elements and a cylindrical protective housing 39 of a material capable of passing the electric and magnetic fields may be provided for each unit. Specification 611,736 is referred to.