GB1145273A - Improvements in or relating to slotted wave guide aerials - Google Patents

Abstract

1,145,273. Aerials. MARCONI CO. Ltd. 14 April, 1966 [11 June, 1965; 31 March, 1966], Nos. 24877/65 and 14248/66. Heading H4A. [Also in Division H1] An aerial comprises a waveguide which is so dimensioned as to propagate only the fundamental mode and which is provided with a continuous slot in one wall. The distance of the slot from an adjacent longitudinally extending boundary of the wall varies at least approximately sinusoidally along its length. As described, a rectangular waveguide G, Fig. 1, has a parallel-sided continuous slot S in one broad wall B which follows a sinusoidal path whose axis is parallel to the edge of that wall. The width of the slot may be from #g/50 to #g/10, a preferred value being #g/20, where #g = length of the wave in the guide. When the pitch L of the slot equals #g the main direction of radiation is broadside, and this direction may be changed by using another frequency. It is stated that the bandwidth obtained is about 30%. In a second embodiment the sinusoidal shape of the slot is approximated by straight segments (Fig. 2, not shown) and in a third embodiment a ridged waveguide is used (Fig. 3, not shown). The cross-section of the waveguide may be other than rectangular, for example, flattened elliptical, provided there is a flat wall for the slot. In other embodiments, the waveguide is bent into a generally sinusoidal shape, and the slot is straight (Figs. 5, 6, not shown). An array may comprise a number of such waveguides placed side by side with their broad walls, containing the slots, coplanar. Or a number of such waveguides may be arranged on edge side by side, with their slots feeding an array of horns or flares H1, H2, H3, Fig. 4, through sideways extending waveguides F1, F2, F3. Coupling cavities C1, C2, C3 are provided between the sinusoidal radiating slots of waveguides of the kind shown, for example, in Fig. 1 and the waveguides Fl, F2, F3, but they are not required if the radiating slots of the waveguides are straight.