GB857140A - Improvements in or relating to directional aerial systems - Google Patents

Abstract

857,140. Aerials. COMPAGNIE GENERALE DE TELEGRAPHIE SANS FIL. April 9, 1959 [April 9, 1958], No. 12003/59. Class 40(7). A directional aerial comprises a primary unit consisting of a radiator or receiver of relatively small longitudinal extension and whose directivity is a function of the transverse dimension of its aperture together with a hollow arrangement of dielectric material having tapered or stepped transverse dimensions, the larger end of the arrangement being substantially in the plane of the aperture of the primary unit. The primary unit may be a suitably fed lens, paraboloid reflector or horn but in the embodiment of Fig. 1 is a horn 1 having a lens 2 arranged in the mouth of the horn, which is also the aperture of the unit. Beyond the lens are three coaxial tubes of dielectric material 3, 4, 5 getting smaller in diameter the further they are from the aperture of the unit. It is stated that energy is canalized by the dielectric arrangement so that it travels more, nearly parallel to the axis thereof and that it is distributed in a zone substantially as shown in the Figure. The overall length of the dielectric arrangement may be of the order of ten times the working wavelength and the complete system is then equivalent to a horn with an aperture two or three times larger than that of horn 1 placed at the outer end of the dielectric arrangement. Instead of the coaxial dielectric tubes a hollow dielectric cone placed with its apex outwards and its base in the plane of the primary unit aperture may be used (Fig. 2, not shown). Aerials according to the invention are very convenient for mounting side by side in the focal plane of a reflecting parabloid for producing overlapping beam patterns.