GB1350549A - Ground antenna for instrument landing systems - Google Patents

Abstract

1350549 Aerials INTERNATIONAL STANDARD ELECTRIC CORP 10 Aug 1972 [12 Aug 1971] 37287/72 Heading H4A A scanning aerial arrangement comprises a laminar structured dielectric lens with varying dielectric constant which is formed as a solid of revolution and which is either of truncated spherical shape, or at least in part of right cylindrical shape, and at least one exciter, means being provided either for moving the exciter on the surface of the lens, or for simulating such movement. The lens is normally disposed with its axis vertical, and it may be shaped wholly as a cylinder, or as a truncated sphere, or as a cylinder with an extension below whose diameter reduces to its lower end. The lens may be so made that its dielectric constant increases in steps from the inside to the outside, and from its bottom to its top. The shaping of the lens, and the gradation of its dielectric constant enable the radiation pattern in the elevation plane to be specially shaped, for example, to reduce or eliminate radiation below the horizontal. An exciter in the form of a horn may be mounted on a ring, coaxial with the lens, and rotatable thereabout in a horizontal plane. Furthermore, two diametrically opposed exciters may be provided each of which is switched on in turn to cover a desired angular range. Alternatively, electronic beam scanning may be provided. The arrangement is particularly suitable for an ILS system operating in the SHF range, and in such a case two additional oppositely located exciters of lower power may be provided on the aforesaid rotatable ring and be used to give " back course " information to an overflying aircraft.