Communications: radio wave antennas – Antennas – Slot type
Patent
1996-08-01
1998-11-03
Hajec, Donald T.
Communications: radio wave antennas
Antennas
Slot type
343770, 343772, H01Q 1310
Patent
active
058315837
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a waveguide antenna comprising a number of longitudinal waveguides with lateral and longitudinal slots, arranged to emit electromagnetic fields with different directions of polarization. Such antennae are used particularly in the satellite technique, but can also be of interest for flight-borne radar. There are for instance demands for a compact construction. Such a waveguide antenna is described in the Swedish published application with application No. 9103555-0 and publication No. 469,540, and shows upper and lower longitudinal waveguides, with a mutual broad side, with longitudinal as well as lateral slots in the upper broad side of the upper waveguide. A waveguide antenna is built of a number of such combined upper and lower waveguides, arranged beside each other, i.e. with mutual short sides. Such a waveguide antenna is compact, per se, but shows a limited possible deflection of the antenna lobe across the waveguide relative to the normal of the antenna.
The object of the present invention is to achieve a waveguide antenna of the kind mentioned in the introduction, which is compact in its construction and makes possible a great deflection of the antenna lobe relative to the normal of the antenna without secondary lobes (grid lobes) being formed.
SUMMARY OF THE INVENTION
According to the invention such a waveguide antenna is primarily characterized in that it comprises a first kind of waveguide having a rectangular cross-section with lateral slots, preferably at right angle to the longitudinal axis of the waveguide, arranged in its first short side, and also comprises a second kind of waveguide having a rectangular cross-section with longitudinal slots arranged in its first short side and with a separating wall arranged symmetrically, going out from its second short side, partly extending towards its first short side, the waveguides of the first and second kind, alternately, being joined at their broad sides with said first short sides facing the same direction forming the waveguide antenna. With this embodiment of a waveguide of the second kind in the form of a so-called ridge waveguide with single ridge the total cross-dimension of the two waveguides is reduced to about half a free space wavelength.
Within the scope of the present invention, different directions of polarization are conceivable, but orthogonal directions of polarization are of special interest, which can be obtained if the slots in the waveguide of the first kind are arranged at right angles to those in the waveguide of the second kind.
Different embodiments are conceivable. The first short sides of the waveguides can for instance lie in a mutual first plane. It is also conceivable that the first short sides of the waveguides lie in separate planes, preferably so that their second short sides lie substantially in a mutual second plane.
The slots can be formed in different ways. The lateral slots can for instance be oriented at right angles to the longitudinal axis of the waveguide, or form any other than right angle to it. The lateral slots can extend lying entirely within the plane of the short side, or cut down a little in the ajoining broad sides. This embodiment means that at a certain given .lambda.g/2 the waveguide can be formed with a short side having a smaller extension, i.e. a more compact antenna is obtained. The lateral slots are suitably located at a distance of about .lambda.g/2 from each other. The use of field-displacing protrusions such as metallic threads etc. constitutes a technique known per se, which is applicable within the scope of this invention too.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described in the following, reference being made to the accompanying figures, which schematically shows examples of embodiments of a waveguide of the first and second kind. A waveguide antenna according to the invention is thus built up by a number of such waveguides arranged beside each other with mutual broad sides. So, it is shown by
FIG. 1 in p
REFERENCES:
patent: 3013267 (1961-03-01), Rotman
patent: 3189908 (1965-06-01), Provencher
patent: 3193830 (1965-07-01), Provencher
patent: 3523297 (1970-08-01), Fee
patent: 3653054 (1972-03-01), Wen
patent: 4243990 (1981-01-01), Nemit et al.
patent: 4839663 (1989-06-01), Kurtz
patent: 5541612 (1996-07-01), Josefsson
patent: 5638079 (1997-06-01), Kastner et al.
Lagerlof Rolf
Lagerstedt Anders
Hajec Donald T.
Ho Tan
SAAB Ericson Space Aktiebolag
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