GB1269950A - Improvements in or relating to antenna feed systems - Google Patents

Abstract

1,269,950. Aerials. PLESSEY CO. Ltd. 10 Nov., 1969 [15 Nov., 1968], No. 54427/68. Heading H4A. [Also in Division H1] An aerial feeder arrangement comprises a waveguide having a plurality of transverse grooves upon its inner surface, the depths of successive grooves decreasing from #g/2 at the entrance of the waveguide to #g/4 at the exit end of the waveguide (#g = wavelength of the dominant mode set up in a groove). In a broadband monopulse tracking feeder arrangement using circularly polarized waves a plain square cross-section wavoguide 7, Fig. 2a, is subdivided into four subsidiary waveguides 8, and is joined to a transversely corrugated end section 9. Grooves 10 in the section 9 are of gradually decreasing depths, from #g/2 adjacent the waveguide 7 to #g/4 adjacent the aperture of the section. The inner surface of the end section 9 is provided with a slight flare of angle #. It is stated that the feed arrangement affords equal E-plane and H-plane beamwidths, with good matching and beamwidth. The corners of the grooves may be filled with shaped pieces, such as squares with chamfered inside comers, to reduce the effects of spurious modes, (Fig. 3, not shown). In another embodiment, a plain square crosssection waveguide (1), Fig. 1 (not shown), is joined to a flared, square cross-section, corrugated extension (2) by means of a square crosssection, corrugated matching section (3). The extension (2) is flared at an angle # to the longitudinal axis of the arrangement, and the grooves therein afforded by the corrugations have a depth of #g/4. The grooves in the matching section (3) are tapered in depth from #g/2 adjacent the waveguide (1) to #g/4 adjacent the extension (2).