GB1471859A - Radio antennae incorporating low loss high relative permitivity dielectric material - Google Patents

Abstract

1471859 Aerials PLESSEY CO Ltd 2 July 1974 [6 June 1973 30 Aug 1973] 27097/73 and 40810/73 Heading H4A A receiving or transmitting radio antenna comprises at least one electrically conductive active rod and a low loss, high relative permittivity (defined as not more than 4% and at least 25, respectively), non-magnetic dielectric material at least partially surrounding and in contact with the said at least one rod, at least part of the electromagnetic energy transmitted or received being constrained to pass through the dielectric material which presents a uniform cylindrical shape surrounding the length of the said at least one rod, the length of the latter being less than the length required for a rod operating at the same frequency in free space. As described, a monopole aerial 3, Fig. 1, extends from the inner conductor 1 of a coaxial feed cable, and is surrounded by a cylinder 4 of compacted dielectric material. A ground plate 5 extends transversely from the outer conductor 2 of the cable. The dielectric material may be a mixture of barium and strontium titanites, or of lanthanum and magnesium titanites, or of calcium and bismuth titanites, and a method of preparation is given. Such mixtures have a relative permittivity of 4 or more, and a considerable reduction in the length of the monopole results. In a second embodiment a conductive ring is positioned between the end of the outer conductor of thecable and the dielectric material cylinder, the ground plate being omitted (Fig. 2, not shown). In a third embodiment, a conductive ring is positioned about the dielectric material cylinder and is connected to the outer conductor of the cable, the ground plate again being omitted (Fig. 3, not shown). Another embodiment features a dipole, which is fed by a two-wire balanced line, and is surrounded by dielectric material (Fig. 7, not shown).