The present invention relates to devices for covering the radiator of an antenna. The present invention may be embodied as a radome.
Single antenna elements, antenna arrays, and antenna systems utilize radomes to protect the antenna components (which may include an antenna and related circuitry). The radome shields the antenna components by preventing objects on one side of the radome from reaching the antenna components that are located on another side of the radome. For example, the antenna components may be protected by a radome from the vagaries of people and/or weather conditions.
Radomes designed for outdoor-use must be capable of shedding water from the surface of the radome, particularly when a major surface of the radome is oriented horizontal to the force of gravity. When water exists in the path of the signals emanating from or to the antenna, the signals may be attenuated. For example, when more than about 20% of the radiating area is covered by water, the attenuation can be significant. Signal attenuation makes incoming and outgoing signals difficult to detect and amplify. Furthermore, when water exists in the path of the signal, the center frequency of the antenna system may shift due to the different electromagnetic characteristics of air and water.
In the prior art, a radome having a curved surface is placed over the antenna in order prevent water from contacting the antenna and in order to prevent water from accumulating in the path of the signals traveling to and from the antenna. The curved surface of the prior art is usually spherical in shape—that is to say that many prior art radomes have an external surface that is a portion of a sphere.
The spherical surfaces of existing radomes allow water to run off the radome, but these radomes increase the size of the antenna assembly, thereby causing the antenna assembly to occupy space that could be used by other components, and/or causing the radome to extend further from a surface to which the antenna is mounted. In situations where the antenna components are mounted below the plane of an exterior surface (e.g. for aerodynamic or aesthetic reasons), a spherical radome designed to prevent water accumulation may extend beyond the exterior surface, thereby reducing the benefits of mounting the antenna components below the exterior surface.
Thus, there is a need for a radome that can prevent water from accumulating, while also minimizing the size of the antenna assembly.
The invention may be embodied as a radome having an exterior-facing surface. The exterior-facing surface has a step. The step may be positioned in the path of signals to be transmitted to a receiver by a radiator which is to be covered by the radome. For example, the step may intersect an imaginary line extending perpendicularly from the radiator. The step may form an edge in the shape of a square, triangle, circle, oval or other shape.
In one embodiment of the invention, the exterior-facing surface of the radome has a first substantially planar surface extending from a first side of the step, and a second substantially planar surface extending from a second side of the step.
To facilitate movement of water, a radome according to the invention may have additional features. For example, a water-repelling coating may be applied to the exterior-facing surface, and/or the exterior-facing surface may be polished.
The invention may be an antenna having such a radome. In such an antenna, a radiator is covered by the radome. The radiator may be substantially planar. In such an antenna, the radome provides a surface facing away from the radiator, and the step is part of the surface facing away from the radiator.
For a fuller understanding of the nature and objects of the invention, reference should be made to the accompanying drawings and the subsequent description. Briefly, the drawings are:
The step 25 of the exterior-facing surface 19 may be positioned such that signals emanating from the radiator 13 must pass through and/or near the step 25. In this manner, the step 25 is positioned so that water does not accumulate in an area that is needed for transmitting signals to a receiver 37. In one embodiment of the invention, the radiator 13 is substantially planar, and the step 25 is arranged above the radiator 13 so that the step 25 intersects an imaginary line (see
The first portion 28 of the exterior-facing surface 19 may be substantially planar. The second portion 31 of the exterior-facing surface 19 may be substantially planar, albeit at a different elevation from the first portion 28 due to the step 25 that exists between the first portion 28 and the second portion 31. In this manner, the first portion 28 of the exterior-facing surface 19 extends from a first side 40 of the step 25, and the second portion 31 of the exterior-facing surface 19 extends from a second side 43 of the step 25. The first portion 28 of the exterior-facing surface 19 may be angled or shaped so that water is encouraged to flow toward the step 25, and the second portion 31 of the exterior-facing surface 19 may be angled or shaped so that water is encouraged to flow away from the step 25.
One or both sides 40, 43 of the step 25 may form a geometric shape, such as a rectangle, triangle, circle, oval. However, the geometric shape need not be one that is common.
The radome 10 may have a water-repelling coating applied to the exterior-facing surface 19. For example, wax or a polymer may be applied to the exterior-facing surface 19 so that water flows across the exterior-facing surface 19 easily. In lieu of coating the radome 10 with a water-repelling material, the radome 10 may be formed from a water-repelling material, and/or polished to provide a smooth surface.
A radome 10 according to the invention may be made part of an antenna 16 which has a radiator 13.
The number and size of the steps 25 may be varied to accommodate different sizes of radomes 10. The number and size of the steps 25 may be selected to minimize the amount of water that is allowed to accumulate on any particular portion of the exterior-facing surface 19, while also taking into account the “footprint” (i.e. the size and shape of the perimeter 34) of the radome 10 and the maximum permitted distance between radiator 13 and the radome 10.
Although the present invention has been described with respect to one or more particular embodiments, it will be understood that other embodiments of the present invention may be made without departing from the spirit and scope of the present invention. Hence, the present invention is deemed limited only by the appended claims and the reasonable interpretation thereof.
This application claims the benefit of priority to U.S. provisional patent application Ser. No. 61/033,677, filed on Mar. 4, 2008.
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Number | Date | Country | |
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61033677 | Mar 2008 | US |