GB715957A - Improvements in or relating to aerial systems - Google Patents

Abstract

715,957. Aerials. GENERAL ELECTRIC CO., Ltd., and KING, D. LA W. W. Nov. 10, 1952 [Aug. 10, 1951], No. 18921/51. [Class 40 (7) An aerial system comprising an open-ended waveguide 5 is provided with a plurality of spaced parts 6 and 7 which project into the guide from the walls and serve to modify the radiation patterns. The arrangement is of particular application with circularly polarized radiation which may be considered as two component plane-polarized waves having their electric vectors in the X- and Y-planes respectively. In the case of the component with the vector. in the X-plane, the guide is effectively bounded by,.walls 8 and lines 12, and by correctly choosing the distance parts 7 project into the guide, the resulting X- and Y-plane polar diagrams may be made substantially the same. Similarly, for the component having the electric vector in the Y-plane, the guide is effectively bounded by walls 9 and lines 11, and if the parts 6 have the same dimensions as parts 7, the two polar diagrams are the same as those due, to the other component. By this means the resulting radiation remains substantially circularly polarized at all points in space contained in a wide solid angle Reference is made generally to elliptically polarized, waves, and also to the use of two in-phase waves having their electric vectors parallel to walls 8 and 9 respectively. In this latter case the resulting radiation is plane polarized at an angle which is set by the relative amplitude of the two waves. A circular waveguide may be used with the parts projecting radially into the guide. The parts are made about one wave-length long, although parts 6 and 7 need not be of the same length, and taper as shown at 13 to prevent any impedance discontinuity. The front ends terminate flush with or just short of the open end 10. The parts may be inclined to the guide walls. The corners of the tube forming the guide may be rounded off since the corner parts are not used in propagation. A thin window may close the open end or, alternatively, the guide may be filled wholly or in part with a solid or foamed dielectric. The waveguide walls and parts may be made of a dielectric material.