AERIAL FEEDERS

摘要

1530446 Aerials PLESSEY CO Ltd 8 Jan 1976 [21 Jan 1975] 2530/75 Heading H4A A linear aerial array comprises a row of radiating slots 4 arranged along one wall 5 of a rectangular waveguide 1, and a plurality of transversely disposed grooves 6 formed on the inside of the wall 7 opposite the wall 5. The waveguide 1 is constructed in two parts, a first part 2, which contains the grooves 6, and which is formed from a solid block of metal, and a second part 3, which contains the radiating slots 4, and which is secured to the part 2. The part 3 may also be formed from a solid block of metal. The metal used may be copper, and the parts may be formed by machining. The edges of the grooves 6 may be rounded. The mating surfaces of the two parts of the waveguide are stepped for alignment purposes, and may be silver plated. Preferably, they are welded together by means of an electron beam which is focused at a point inside the inner surface of the waveguide. The grooves 6 provide reactive loading, which results in enhanced group delay between slots. A greater beam swing for a given frequency change is thereby obtained. The array may be disposed along the focal line of a cylindrical parabolic reflector, and a series of external upstanding longitudinal fins 9 provide side-lobe suppression. The slots 4 as shown are of crossed form, for circularly polarized operation, but they can be of straight form if linearly polarized operation is required. Sideways extending fins are provided for cooling purposes, and these may be supplemented by ducts in the wall 7 of the waveguide, through which fluid is circulated.