A switched-beam directive aerial on 600 Mc/s

An account is given of research work into the effect of a cylindrical parabolic reflector on 600-Mc/s electromagnetic waves. It is shown that such a reflector, fed by a line of dipoles parallel to the axis, forms an efficient aerial at this frequency, radiation being very similar to that from a uniformly-excited aperture. Problems encountered in the development of such an aerial, horizontally polarized, suitable for production and ship-fitting, are dealt with; in particular it is shown, both theoretically and practically, how the side radiation from a line of dipoles can be reduced by feeding more power to the centre dipoles of the array than to the extreme ones. The development of a phasing system and mechanism for rapid switching of the beam from one side of the normal direction to the other are described, together with an electrical method of correcting errors due to both mechanical and electrical variations in production of the aerial.