Patent Application
20090109111
1. Field of the Invention
This invention relates to feed horns for reflector antennas. More particularly, the invention relates to a cost effective and electrically optimized cross-polarization interference compensating feed horn for an offset reflector antenna arrangement.
2. Description of Related Art
Reflector antennas may be configured in an offset arrangement where a sub reflector and or feed is located spaced away from a center point of a reflector target beam path. Although offset reflector antenna geometry minimizes beam interference that would otherwise be generated by the presence of the subreflector and or feed, it also generates an inherent cross-polarization within the non-symetric plane.
U.S. Pat. No. 6,771,225 discloses an elliptical main reflector and one piece feed horn in an offset configuration. The one piece feed horn is formed with compensation slots in a waveguide section that are open to the horn end of the feed, the slot depths limited and the innermost step face angled in an electrical performance compromise to enable manufacture via a single die casting.
In addition to the electrical performance compromises made to enable manufacture via a single die casting, U.S. Pat. No. 6,771,225 requires the manufacture of a separate embodiment for every desired combination of feed position/orientation, main reflector geometry and or operating frequency(s). The required complex die molds, unique to each embodiment, significantly increases tooling, manufacturing and inventory costs.
Competition within the reflector antenna industry has focused attention on antenna designs that reduce antenna production costs but which still satisfy and or improve upon stringent electrical specifications,
Therefore, it is an object of the invention to provide an apparatus that overcomes deficiencies in the prior art.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention.
The inventor has recognized that a two component feed horn arrangement enables both cost effective manufacture of multiple embodiments and significant improvements to feed horn electrical performance.
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Because the slot(s) 16 are open to the front end 10, they may be formed with any desired length, depth and width to match the corresponding bore 14 diameter and operating frequency parameters without introducing overhanging edges along the longitudinal axis.
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Further, because the slot(s) 16 are fully contained within the waveguide body 6, the step 22 widths of the horn body 6 are not limited or constrained by desired slot 16 depths. Thus the first step of the horn bore 26 may be provided with a step 22 width that is less than a depth of the slot(s) 16 and the horn bore 26 formed with a diameter at the back end 12 equal to or less than the waveguide bore 14 at the front end 10.
The various dimension selections are also made in view of the other antenna optics, such as the main reflector and or sub reflector if present, to provide a complete optic solution with respect to cross-polarization interference cancellation and signal phasing.
Both the horn body 4 and the waveguide body 6 may be dimensioned for manufacture via die casting, injection molding, thixotropic molding, metal injection molding or the like without overhanging edges for mold separation along the longitudinal and transverse dimensions. The separate horn and waveguide body(s) 4, 6 may then coupled together via fasteners. A gasket such as an o-ring (not shown for clarity) may be placed in an annular groove 24 formed in the front face 30 of the waveguide body 4 and or the back face 32 of the horn body 6 to environmentally seal the joint between the horn body 6 and the waveguide body 4. Alternatively, a monolithic embodiment may be achieved by overmolding, for example forming the horn body 4 upon a pre-formed waveguide body 6 or vice versa.
From the foregoing, it will be apparent that the present invention brings to the art a feed horn 2 with improved electrical performance and significant manufacturing cost efficiencies. A range of different feed horn embodiments may be quickly assembled from different waveguide and horn body(s) 4, 6 to meet varying main reflector and or operating frequency requirements, significantly reducing inventory costs. Alternative embodiments may be cost effectively prepared by fabrication only of the needed molds or mold portions. For example, the slot(s) 16 configuration of a selected waveguide body 4 may be modified by preparing only an alternate longitudinal axis portion of the waveguide body 4 mold(s).
Where in the foregoing description reference has been made to ratios, integers, components or modules having known equivalents then such equivalents are herein incorporated as if individually set forth.
Each of the patents identified in this specification are herein incorporated by reference in their entirety to the same extent as if each individual patent was fully set forth herein for all each discloses or if specifically and individually indicated to be incorporated by reference.
While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus, methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of applicant's general inventive concept. Further, it is to be appreciated that improvements and/or modifications may be made thereto without departing from the scope or spirit of the present invention as defined by the following claims.
