Communications: radio wave antennas – Antennas – Balanced doublet - centerfed
Reexamination Certificate
1999-08-31
2001-03-27
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
Balanced doublet - centerfed
C343S807000
Reexamination Certificate
active
06208311
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention pertains generally to the field of antennas and antenna systems including, more particularly, antennas and antenna systems for use in cellular and other wireless communications systems.
While substantial recent attention has been directed to the design and implementation of cellular and other wireless communications systems and to the communications protocols utilized by those systems, surprisingly little attention has been directed to the development of improved antennas and antenna systems for use within those communications systems.
Perhaps, the reason for this is that until recently space for the deployment of antenna networks was readily available on the tops of buildings in a dense urban environment. Thus, until recently little attention was paid to the development of relatively small, aesthetically appealing antenna networks which could be deployed, for example, on light poles or telephone poles substantially at street level.
Nor was there any substantial reason, until recently, to address the issue of channeling in the “urban canyon.” The term, “urban canyon,” as used herein, refers to the linear open space which exists between buildings along streets, for example, in a dense urban environment. As for the issue of channeling within an urban canyon, it has been found that the exterior surfaces (walls and the like) of the buildings lining an urban canyon exhibit characteristics quite similar to the walls of a typical wave guide. Thus, when a radio frequency (RF) signal is transmitted within an urban canyon, the signal tends to propagate for the entire length of the urban canyon with very little attenuation. While this characteristic of an urban canyon may be viewed by some as advantageous, this characteristic raises a serious issue when it is desired to implement a cellular communications network within a dense urban environment. In short, this characteristic makes it difficult for mobile units and base stations alike to identify differences in the strengths of received signals, thus, making it difficult to effect necessary and proper hand-offs between and among the mobile units and base stations. To better understand this principle, one should consider a scenario where a mobile unit enters a four-way intersection within a dense urban environment (i.e., when a mobile unit reaches the intersection point of two urban canyons). Upon entering the intersection, the mobile unit is likely to receive four separate signals of substantially the same amplitude from four separate base stations, and the base stations are likely to receive signals of similar amplitude from the mobile unit. This presents a substantial risk that the mobile unit will be handed-off to an improper base station and, as a result, communications between the mobile unit and the base stations will be terminated prematurely (i.e., the call may be lost).
Another issue which must be addressed in the design of antenna networks for use in “low tier,” or street level, deployment schemes is the issue of “multipath” interference. The term “multipath” refers to the tendency of an antenna in a dense urban environment (or any other environment) to receive a single (or the same) signal multiple times as the signal is reflected from objects (poles, buildings and the like) in the area proximate the antenna. To combat multipath interference, it may be desirable to employ one or more pattern or separation diversity methodologies within a given antenna network.
Given the substantial issues of channeling, multipath, size and aesthetics which must be addressed when designing antennas and antenna networks for low tier deployment within a dense urban (or other) environment, it is believed that those skilled in the art would find improved antennas and antenna networks which may be deployed in relatively small, aesthetically appealing packages, and which may provide substantial multipath and channeling mitigation, to be very useful.
SUMMARY OF THE INVENTION
The present invention is directed to the implementation, manufacture and use of improved antenna elements and antenna arrays for use in cellular and other wireless communications systems. The antennas and antenna arrays of the present invention may be deployed in relatively small, aesthetically appealing packages and, perhaps more importantly, may be utilized to provide substantial mitigation of multipath and channeling in a dense urban (or other) environment.
In one innovative aspect, the present invention is directed to the implementation, manufacture and use of a folded mono-bow antenna element. A folded mono-bow antenna element in accordance with the present invention may comprise, for example, a main radiating bowtie element and a parasitic element, wherein the main radiating bowtie element and the parasitic element are separated by a dielectric material and, if desired, may be formed on separate sides of a dielectric substrate, such as a printed circuit board. A shorting element may also provide an electrical connection between a selected portion of the main radiating bowtie element and a selected portion of the parasitic element. The main radiating bowtie element may be coupled to a feed pin mounted through an insulated hole formed in an associated ground plane, and the parasitic element may be mounted to the ground plane. A folded mono-bow antenna in accordance with the present invention may have a substantially omnidirectional radiation pattern in the horizontal plane, a radiation pattern which varies in the elevation plane depending upon the size of an associated ground plane, and may be dimensioned to provide transmission and reception over a fairly broad bandwidth centered, for example, at a frequency of 1920 MHZ. This makes the folded mono-bow antenna of the present invention quite suitable for use in cellular and other wireless communications systems.
In one innovative arrangement, a pair of folded mono-bow antennas (or other monopole antennas) may be configured to provide a dual pattern diversity folded mono-bow array. In such an embodiment, two folded mono-bow antenna elements (or other monopole antenna elements) may be mounted on a common ground plane and fed by a 180° ring hybrid combiner/splitter circuit. By combining a pair of folded mono-bow antenna elements in this fashion, it is possible to achieve a radiation pattern which exhibits reduced azimuth beam width orthogonal beam pairs. Thus, a dual pattern diversity folded mono-bow antenna array in accordance with the present invention is particularly well suited for use with communications systems which utilize pattern diversity to mitigate multipath.
In another innovative arrangement, four of the aforementioned dual pattern diversity folded mono-bow arrays may be configured to provide a dual polarized 4-way diversity antenna array. In such an embodiment, the ground planes of the respective dual pattern diversity folded mono-bow arrays may be arranged such that selected pairs of the ground planes form parallel and opposing surfaces, and such that adjacent pairs of the ground planes have an orthogonal relationship to one another.
In still another innovative arrangement, four folded mono-bow antenna elements (or other monopole antenna elements) may be configured to provide a 4-beam monopole diversity antenna array. In such an embodiment, four folded mono-bow antenna elements may be mounted on a common ground plane along a common axis and fed by a butler matrix combiner.
In still another innovative arrangement, two folded mono-bow antenna elements may be configured to provide an omnidirectional dual pattern diversity antenna array. In such an embodiment, a pair of folded mono-bow antenna element may be coupled to a 180° hybrid combiner network and oriented along a common axis in contra-direction to one another.
In still another innovative arrangement, two folded mono-bow antenna elements and two contradirectionally oriented “T” shaped antenna elements may be configured to provide a dual polarized bi-directional diversity antenna array. In such an embodiment, the p
Aden John L.
Reece John Kenneth
Lyon & Lyon LLP
Wimer Michael C.
Xircom, Inc.
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