GB780086A - Improvements in and relating to electromagnetic wave radiators - Google Patents

Abstract

780,086. Waveguides. FOSTER, K., and THIELE, A. P. C. Nov. 28, 1955 [Dec. 8, 1954], No. 35530/54. Class 40 (8). [Also in Group XL (c)] The invention relates to a horn for radiating circularly polarized wave energy and feed means therefor. The horn 10 is constructed with a rectangular cross-section which differs in shape along its length and is so dimensioned that for wayes of a given wavelength A a wave polarized parallel to one edge of the throat is delayed an odd number of quarter wavelengths relative to a wave polarized perpendicular to that edge. It is preferred to make the throat end of the horn square. To feed the horn with the required orthogonal plane polarized waves feedguide 11 may be coupled by transition guide 12 to circular guide 13 itself coupled to the horn by transition guide 14. The guide 11 may carry an H 11 wave and be orientated so that energy reaches the throat of the horn with its E vector at 45 degrees to the edges and is there resolved into the two waves required. In a different arrangement section 13 may contain a phaseshifter by means of which two H 11 waves polarized at right angles are produced which combine to give a wave polarized with its E vector at 45 degrees to the throat edges as before. Suitable phase shifters consist of a correctly orientated strip of dielectric (Fig. 3a, not shown), a pair of diametrically opposite metal fins (Fig. 4, not shown) or a metal plug 18 against the guide wall (Fig. 5). The central part of the section 13 can also be made elliptical to produce the same effect. The phase shifters are preferably stepped or otherwise shaped to match them to the approaching and outgoing waveguide sections.