Patent Application
20100013729
This application is based on French Patent Application #07 58 847 filed on Nov. 7, 2007, the disclosure of which is hereby incorporated by reference thereto in its entirety, and the priority of which is hereby claimed under 35 U.S.C. §119.
1. Field of the Invention
This invention pertains to a telecommunication antenna, particularly one used for base stations of cellular communication networks (including GSM and UMTs networks). Such an antenna is made up of radiating element network spaced slightly apart. The invention particularly pertains to the reflecting means with which this antenna is equipped.
2. Description of the Prior Art
A telecommunications antenna sends and receives radio waves over frequencies specific to a telecommunications system used by that antenna. Thus, an antenna intended for the UMTS system uses waves whose frequencies are within the range of 1710 to 2170 MHz. A base station comprises a network of antennas, and supplies each antenna with waves whose frequencies are within the range that the antenna uses. However, the distance between the antennas is short, and as a result, every antenna has an influence on the adjacent antenna.
The document U.S. Pat. No. 5,710,569 mentions the problem of minimizing the lateral radiation of an antenna, a source of interference with neighboring antennas, by modifying the width of the horizontal beam and improving the front-to-back ratio. This document describes an antenna comprising arrayed dipoles attached to the flat base of a reflector whose edges fold upward. Choke reflectors are disposed within the area between the dipole and the lateral upward fold of the reflector, which they are distinct from, in such a way as to serve as a screen on other side of the row of dipoles. These choke reflectors are made up of metal sheets folded into L shapes and attached to the flat base of the reflector supporting the dipoles. They may move in a horizontal direction, so that they move closer to or further from the dipole array, in order to modify the characteristics of the antenna.
The document EP-0 973 231 states its purposes as minimizing the lateral lobes of an antenna, which are a source of interference with adjacent lobes, and to obtain the characteristics of a bipolarization with just one antenna. This document also mentions the possibility of controlling the isolation by adjusting the positions of the choke reflectors. This document describes an antenna comprising radiating elements attached to the flat part of a reflector comprising downward-folding edges. Two choke reflectors which may move longitudinally are disposed along the radiating elements on the flat part of the reflector. Transversal choke reflectors, furthermore, are placed between the radiating elements, perpendicular to the lateral choke reflectors.
In these documents, the term “choke reflector” refers to simple angle pieces which form two parallel flat surfaces which surround the arrayed radiating elements as closely as possible. The purpose of these choke reflectors is to modify the beam width value of the antenna. The authors of these documents have sought after a way to control the rated beam width value of the antenna by disposing the choke reflectors within the central area of the antenna, as close as possible to the dipoles.
The purpose of the invention is to improve the stability of a radio antenna's beam width along the horizontal plane.
A further purpose is to improve the performance of this antenna in cross-polarization along the main axis and along an axis of ±60° from the antenna.
The object of the invention is an antenna comprising a network of arrayed radiating elements, a first reflecting means comprising a flat central part upon which are disposed the radiating elements and longitudinally folded edges on either side of the arrangement of elements, and at least one second reflective means.
According to the invention, the second reflective means is a choke reflector disposed on the outside of the space separating the radiating elements from the folded edge of the first reflective means, and it is separate from the first reflective means by a layer of dielectric material so that it can be connected to the first reflective means by capacitive coupling.
According to the invention, the second reflective means is disposed outside the folded edges of the first reflective means of the antenna, outside the immediate radiating area of the elements, which, as a result, produces the stabilization of the beam width value of the antenna, and at the same time, simultaneously improves the cross-polarization parameters.
The second reflective means, according to the invention, is connected to the first reflective means by indirect electrical coupling or capacitive coupling. This represents an improvement upon the prior art: it is simply to assemble and poses no intermodulation problems resulting from improper assembly between parts. To achieve this, the second reflective means is separate from the first reflective means by a layer of dielectric material. Thus, the grounded parts are not in direct contact.
Unlike known devices, the inventive choke reflector does not affect the rated beam width value of the antenna, but it does improve the stability of this value. Furthermore, the invention enables an improvement in the antenna's cross-polarization parameters, whereas the prior art only describes vertical-polarization antennas.
Furthermore, it must be noted that the insulating value is not in any way influences by the presence of choke reflectors, as they are placed too far away from the radiating elements.
In one embodiment of the invention, the second reflective means is a metal sheet folded into a U shape, with the outer surface of one of the arms of the U cooperating with the outer surface of a folded edge of the first reflective means.
In one variant, the arms of the U are unequal in length.
In another variant, the metal sheet is made of aluminum.
According to one aspect of the invention, the second reflective means is disposed upon at least one part of the antenna's entire length. The choke reflector is applied against the outer surface of the folded edges of the first reflective means, on certain portions of the length of the first reflective means. The choke reflector may also cover the entire length of the first reflective means.
Other characteristics and advantages of the invention will become apparent while reading the following description of embodiments, which are non-limiting and given for purely illustrative purposes, and in the attached drawing, in which.
The antenna 1 comprises choke reflectors 10 made up of aluminum sheets folded into a U shape and placed longitudinally outside the reflector 3, out of the area near the radiating elements 2.
The outer surface 11 of one of the arms of the U is affixed to the outer surface 12 of the lateral edge 5 of the reflector 3, as shown in
The arm of the U of the choke reflector 10 is separated from the lateral edge 5 of the reflector 3 to which it is affixed by a layer 13 of dielectric material. The capacitive coupling, equivalent to a short-circuit for the radio frequencies, which is created between the lower part 14 of the choke reflector 10 and the lower angle 15 of the reflector 3 leads to an open circuit in the upper edge 16 of the reflector 3. As a result, the currents 17 become trapped within the choke reflector 10, and no longer propagate in an uncontrolled manner (arrow 18) outside and inside the lower flat part 4 in the rear of the reflector 3, as illustrated in
The radiating elements 2 are further protected by a casing 21.
In the event that two arrays of radiating elements 30 are disposed side-by-side, as depicted in
In a perspective view,
A dual polarization antenna has two ports denoted +45° and −45°, which correspond to the two connectors of the antenna.
Comparing the curves of
Comparing the curves of
| Number | Date | Country | Kind |
|---|---|---|---|
| 0758847 | Nov 2007 | FR | national |
