GB647136A - Directional antenna systems - Google Patents

Abstract

647,136. Aerials. PHILCO CORPORATION. March 20, 1947, No. 7696. Convention date, March 28, 1946. [Class 40 (vii)] A directive aerial system comprises an aerial structure having an aperture through which radio waves are transmitted or received, and a metallic diffracting-plate situated wholly outside the aerial structure substantially in front of the aperture thereof and at a distance of approximately a quarter-wavelength therefrom. The diffracting-plate distorts the wave-front of waves radiated from the aerial, producing a substantially planar front from a curved front, whereby the overall directivity of the system is increased. In Fig. 1A, metallic disc 9, having a diameter of slightly less than a half-wavelength at the operating frequency, is spaced approximately a quarter-wavelength from the mouth of the horn radiator 4. The disc is supported upon a dielectric rod 10 which is mounted upon a plate of dielectric material which is fixed over the aperture of the horn. The horn is excited from a probe 6 coupled to a coaxial feeder; the end-plate 8 is made movable so that the feeder may be correctly matched to the aerial system. In Fig. 2 a biconical aerial co-operates with a coaxial, annular, metallic ring 35, the diameter of which is approximately a half-wavelength greater than the maximum diameter of the cones. The invention is applicable to an aerial system comprising a dipole and spherical reflector. The Specification as open to inspection under Sect. 91 also describes a system comprising a plurality of metallic discs mounted upon a dielectric supporting-disc and arranged in front of a horn aperture together with a further disc supported upon a rod as in Fig. 1. This subjectmatter does not appear in the Specification as accepted.