Patent Application
20130082896
1. Field of the Invention
This invention relates to microwave reflector antennas. More particularly, the invention relates to a radome for a reflector antenna utilizing a cost effective twin-wall extruded polymer material retained via folding the material around a rim of the reflector dish.
2. Description of Related Art
The open end of a reflector antenna is typically enclosed by a radome coupled to the distal end (the open end) of the reflector dish. The radome provides environmental protection and improves wind load characteristics of the antenna. Because reflector antennas are often mounted in remote locations, such as high atop radio towers, a radome failure may incur significant repair/replacement expense.
Prior radomes have utilized, for example, woven fabric stretched across the distal end of the reflector dish and held in place by a plurality of springs and/or hooks. Woven fabrics may be subject to degradation and/or stretching over time. Alternatively, specialized woven fabrics with sufficient strength to endure long term environmental exposure may be expensive. Also, the numerous connections required to evenly tension the fabric across the distal end of the reflector dish may complicate radome installation and/or removal.
Another common radome configuration is a rigid and/or semi-rigid injection molded and/or machined solid polymer portion dimensioned to seat upon the open end of the reflector dish. Such radomes may be retained, for example, by a band clamp or the like that couples the radome to the rim of the reflector dish. Injection molding and/or machining may require significant capital investment in specialized equipment and operations/maintenance personnel.
Competition in the reflector antenna market has focused attention on improving electrical performance and minimization of overall manufacturing, inventory, distribution, installation and maintenance costs. Therefore, it is an object of the invention to provide a radome and resulting reflector antenna assembly 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, where like reference numbers in the drawing figures refer to the same feature or element and may not be described in detail for every drawing figure in which they appear 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 inventors have recognized that a radome utilizing commonly available twin-wall extruded polymer sheet material may enable significant materials, manufacturing and/or installation efficiencies.
As best shown in
The twin-wall extruded polymer material is provided in a generally planar portion 13 dimensioned to cover the open end of the desired reflector dish 11. A periphery of the planar portion 13 is provided with a plurality of slits 15, the slits 15 defining a plurality of tabs 17. As best shown in
As best shown in
One skilled in the art will appreciate that folding tabs 17 around the outer diameter of the rim 9 and then radially inward will introduce edge-to-edge interference as second portions 23 with a larger circumference are translated inward to an area with a smaller circumference. Such interference may be avoided, for example, by applying slits 15 with a V shape (see
When each of the tabs 17 is folded around the rim 9 of the reflector dish 11, the hollow channels 7 of the twin-wall material collapse at an edge 27, such as the fold guide 19, if present, securely coupling the planar portion 13 to the rim 9 until such folds are straightened. One skilled in the art will appreciate that the hollow channel 7 collapses along the circumference of the rim 9, thereby providing a longitudinal interlock across the rim diameter that secures the planar portion 13 in position without requiring further clamping, perforation and/or compression as long as the folds are maintained seated against the rim 9. Because the hollow channel 7 is collapsed along the edge 27, tension applied upon the radome surface is unable to pull the planar portion 13 from its position at the rim 9, as such would require destruction of the hollow channel structure at either side of the edge 27 before further displacement can occur.
Although the hollow channels 7 are sealed between the front wall 1, back wall 3 and flutes 5, the ends of the channels 7 may present an entry path for moisture to accumulate within the channels 7. The collapse of the channels 7 at the edge 27 as the tabs 17 are folded provides a significant seal against moisture entry. To allow any moisture which does enter and/or condense within the channels 7 to drain rather than accumulate along the channels 7, the planar portion 13 may be aligned on the rim 9 such that the channels 7 are normal to a ground plane of the reflector antenna. Thereby, any moisture accumulation that occurs within the channels 7 will drain by gravity toward the bottom of the rim 9, out of the reflector antenna signal path. Alternatively, the channels 7 may be aligned, for example, at 45 degrees so that any RF influence generated by the channel sidewalls impacts neither of the critical horizontal or vertical planes.
As best shown in
The folded tabs 17 may be retained in contact with the rim outer diameter and back side 25 by applying a band clamp 33, for example as shown in
The turnback region 39 may be applied, for example, as an outward bend prior to the inward end of the proximal lip 37. As the band clamp 33 is tightened during interconnection of the radome and the reflector dish 11, the diameter of the band clamp 33 is progressively reduced, driving the turnback region 39 against the convex outer surface 41 of the signal area of the reflector dish 9, into a uniform circumferential interference fit. As the band clamp 33 is further tightened, the turnback region 39 slides progressively inward along the outer surface 41 of the signal area of the reflector dish 11 toward the reflector dish proximal end. Thereby, the distal lip of the band clamp also moves towards a proximal end of the reflector dish 11, securely clamping the planar portion 13 against the rim 9. Because the interference fit between the turnback region 39 and the outer surface 41 of the reflector dish 11 is circumferentially uniform, any RF leakage between these surfaces may be reduced.
The bandclamp 33 may be further provided with a depth flange 43 extending toward the reflector dish proximal end a distance selected for example with respect to a desired operating frequency of the resulting reflector antenna, for example between 0.8 and 1.5 wavelengths of the operating frequency, further reducing backlobe components of the resulting reflector antenna signal pattern that may be otherwise generated by the presence of the bandclamp 33, for example by generating mutual interference of surface currents traveling along the outer periphery of the band clamp 33.
Alternatively, as demonstrated in
As best shown in
Because the twin-wall extruded radome material enables simplified radome and reflector dish periphery geometries, the resulting reflector antenna may have improved materials and manufacturing costs. Because the radome is simply and securely attached, installation and maintenance may be simplified compared to prior reflector antenna configurations with cost intensive molded/machined radome elements, complex peripheral geometries, delicate back lobe suppression ring coatings, platings and/or RF absorbing materials. Where the band clamp 33 is omitted entirely, one skilled in the art will appreciate that in addition to improving the electrical performance of the reflector antenna by eliminating the signal conducting structure of a radome retaining band clamp 33, the reduction in components in addition to simplification of the radome material may further reduce the overall cost of the resulting reflector antenna,
Where in the foregoing description reference has been made to materials, ratios, integers or components having known equivalents then such equivalents are herein incorporated as if individually set forth.
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.
