GB979645A - Improvements in or relating to directional aerials - Google Patents

Abstract

979,645. Aerials. COMPAGNIE GENERALE DE TELEGRAPHIE SANS FIL. June 29, 1961 [July 4, 1960], No. 23546/61. Heading H4A. A directional aerial comprises a plurality of slotted waveguide sections extending in the same direction and all branched off at different points along a feeder waveguide, there being a linear relation between the phases of the energies fed to the slotted sections and the distances of the branch points from the input end of the feeder, the energies being propogated with the same predetermined phase velocity in the feeder and slotted sections. The phase velocities are governed by the presence of a dielectric coating T on one wall of the feeder waveguide G and on the wall opposite to the radiating slots F of each of the slotted sections. These sections are collinear and each is coupled to the feeder by a directional coupler D and a phase shifter #. Each phase shifter may comprise a dielectric plate which can be displaced in the waveguide or a ferrite insert whose phase shift can be controlled by a magnetic field. The phase of the energy propogated along the feeder guide varies linearly with distance from the input end and the phase shifters introduce an additional phase shift into each slotted section, a phase shift of # being introduced into the section nearest the input end of the feeder, 2# into the next section, 3# into the next, and so on. This is stated to result in a sharply-directional beam and its direction may be varied by simultaneous control of the phase shifters. The slots in each slotted section may be proportioned so that the amplitude per slot varies along the guide to a maximum mid-way along the array of slots, Fig. 3 (not shown), the widths of the slots being chosen to provide maximum elimination of side lobes in the radiation pattern.