Patent Application
20210135371
The present application claims priority to and the benefit of Chinese Patent Application No. 201911073578.9, filed Nov. 6, 2019, the content of which is hereby incorporated herein in its entirety.
The present invention generally relates to radio communications and, more particularly, to antenna assemblies for a beamforming antenna and base station antennas for cellular communications systems.
Cellular communications systems are well known in the art. In a cellular communications system, a geographic area is divided into a series of regions that are referred to as “cells” which are served by respective base stations. The base station may include one or more base station antennas that are configured to provide two-way radio frequency (“RF”) communications with mobile subscribers that are within the cell served by the base station.
In many cases, each base station is divided into “sectors.” In perhaps the most common configuration, a hexagonally shaped cell is divided into three 120° sectors, and each sector is served by one or more base station antennas that have an azimuth Half Power Beam width (HPBW) of approximately 65°. Typically, the base station antennas are mounted on a tower structure, with the radiation patterns (also referred to herein as “antenna beams”) that are generated by the base station antennas directed outwardly. Base station antennas are often implemented as linear or planar phased arrays of radiating elements.
Base station antennas often include a linear array or a two-dimensional array of radiating elements, such as crossed dipole or patch radiating elements. In order to increase system capacity, beamforming base station antennas are now being deployed that include multiple closely-spaced linear arrays of radiating elements that are configured for beamforming. A typical objective with such beamforming antennas is to generate an antenna beam that has a narrowed beamwidth in the azimuth plane. This increases the power of the signal transmitted in the direction of a desired user and reduces interference.
If the linear arrays of radiating elements in a beamforming antenna are closely spaced together, it may be possible to scan the antenna beam to very wide angles in the azimuth plane (e.g., azimuth scanning angles of 60°) without generating significant grating lobes. However, as the linear arrays are spaced more closely together, mutual coupling increases between the radiating elements in adjacent linear arrays, which degrades other performance parameters of the base station antenna such as the co-polarization performance. Therefore, the radiation pattern of the antenna may be distorted and the beamforming performance may be degraded. This is undesirable.
Embodiments of the present invention provide an antenna assembly for a beamforming antenna and a related base station antenna capable of overcoming at least one drawback in the prior art.
According to a first aspect of the present invention, there is provided an antenna assembly for a beamforming antenna that includes a reflector and an antenna array that has a plurality of vertically extending arrays. The plurality of vertically extending arrays include a plurality of first radiating elements that are arranged as a first of the vertically extending arrays, the first radiating elements extending forwardly from the reflector; and a plurality of second radiating elements that are arranged as a second of the vertically extending arrays, the second radiating elements extending forwardly from the reflector. The first and second of the vertically extending arrays are adjacent each other in a horizontal direction, two adjacent first radiating elements are spaced apart from one another by a first distance, and a first radiating element and an adjacent second radiating element are spaced apart from one another by a second distance. The first distance is substantially equal to the second distance. The antenna assembly further includes a plurality of parasitic elements for the antenna array. The parasitic elements are placed along sides of the first and second of the vertically extending arrays, between adjacent ones of the first radiating elements and between adjacent ones of the second radiating elements. A first of the parasitic elements extends farther forwardly from the reflector than a second of the parasitic elements, and the first of the parasitic elements is closer to a middle of the antenna array than the second of the parasitic elements.
With the antenna assembly in accordance with some embodiments of the present invention, the shape of the radiation pattern and/or the CPR performance of the antenna may also be improved.
In some embodiments, the parasitic elements can be mounted at three or more different distances forwardly of the reflector. At least some of the parasitic elements that are in between the first and second of the vertically extending arrays are mounted farther from the reflector than are at least some of the parasitic elements that are not between the first and second of the vertically extending arrays.
In some embodiments, the parasitic elements can be stepped down one or more times from a middle region of the antenna array towards an outer region of the antenna arrays in a vertical direction and/or a horizontal direction.
In some embodiments, the second radiating elements can be staggered in a vertical direction with respect to the first radiating elements.
In some embodiments, ones of the parasitic elements can be provided around each first radiating element and around each second radiating element.
In some embodiments, the parasitic elements can include a plurality of first parasitic elements that extend vertically, the first parasitic elements can be disposed on both sides of each first radiating element in the horizontal direction and on both sides of each second radiating element in the horizontal direction.
In some embodiments, distances that the first parasitic elements are located forwardly of the reflector can be defined according to the intensities of coupling interference in respective locations where the first parasitic elements are located.
In some embodiments, distances that the first parasitic elements are located forwardly of the reflector can be stepped down one or more times from the middle of the antenna array towards the outer regions of the antenna array.
In some embodiments, the parasitic elements can include a plurality of second parasitic elements that extend horizontally. The second parasitic elements can be disposed on both sides of each first radiating element in a vertical direction and on both sides of each second radiating element in the vertical direction.
In some embodiments, distances that the second parasitic element are located in front of the reflector can be defined according to the intensities of coupling interference in respective locations where the second parasitic elements are located.
In some embodiments, distances that the second parasitic elements are located in front of the reflector can be stepped down one or more times from the middle of the antenna array towards the outer regions of the antenna array.
In some embodiments, the plurality of vertically extending arrays can further include: a plurality of third radiating elements that are arranged as a third of the vertically extending arrays. The first of the vertically extending arrays, the second of the vertically extending arrays, and the third of the vertically extending arrays can be sequentially arranged in the horizontal direction. Arranged about a first of the second radiating elements, a substantially regular hexagonal shape can be collectively defined by two of the first radiating elements that are adjacent the first of the second radiating elements, two of the second radiating elements that are adjacent the first of the second radiating elements, and two of the third radiating elements that are adjacent the first of the second radiating elements.
According to another aspect of the present invention, there is provided an antenna assembly for a beamforming antenna that includes a reflector and an antenna array that includes a plurality of vertically extending arrays. The plurality of vertically extending arrays can have: a plurality of first radiating elements that are arranged as a first of the vertically extending arrays, the first radiating elements extending forwardly from the reflector; and a plurality of second radiating elements that are arranged as a second of the vertically extending arrays, the second radiating elements extending forwardly from the reflector. The first and second of the vertically extending arrays are adjacent each other in a horizontal direction. An average value of spacing between adjacent first radiating elements is a first average spacing, and an average value of spacing between a first radiating element and an adjacent second radiating element is a second average spacing. The absolute value of the difference between the first average spacing minus the second average spacing is less than 10% of the first or second average spacing. The antenna assembly further includes a plurality of parasitic elements for the antenna arrays. The parasitic elements are placed along sides of the first and second of the vertically extending arrays, between adjacent ones of the first radiating elements, and between adjacent ones of the second radiating elements. Distances that the parasitic elements extend forwardly from the reflector are stepped down one or more times from the middle region towards the outer region of the antenna array in a vertical direction and/or a horizontal direction.
In some embodiments, the absolute value of the difference between the first average spacing minus the second average spacing can be less than 5% of the first or second average spacing.
In some embodiments, the first average spacing can be substantially equal to the second average spacing.
In some embodiments, the second radiating elements can be staggered in a vertical direction with respect to the first radiating elements.
In some embodiments, parasitic elements can be provided about each first radiating element and around each second radiating element.
In some embodiments, the parasitic elements can further include a plurality of first vertically extending parasitic elements, the first parasitic elements being disposed on both sides of each of the first radiating elements and on both sides of each of the second radiating elements in the horizontal direction.
In some embodiments, the parasitic elements can further include a plurality of second horizontally extending parasitic elements, the second parasitic elements being disposed on both sides of each of the first radiating elements and on both sides of each of the second radiating elements in a vertical direction.
According to yet other aspects of the present invention, a base station antenna includes an antenna assembly according to any embodiments of present invention.
According to another aspect of the present invention, a base station antenna is provided that includes a beamforming array with a reflector, an antenna array that has a plurality of columns of radiating elements that extend forwardly from the reflector, and a plurality of first parasitic elements and a plurality of second parasitic elements. The first parasitic elements are arranged as a plurality of columns of first parasitic elements that are positioned between respective pairs of adjacent columns of radiating elements and outside end ones of the columns of radiating elements. At least some of the first parasitic elements that are positioned between a first pair of adjacent columns of radiating elements are located farther forwardly from the reflector than are the first parasitic elements that are outside the end columns of radiating elements.
In some embodiments, the first parasitic elements that extend the farthest forwardly from the reflector can be included in a middle one of the plurality of columns of first parasitic elements.
In some embodiments, the second parasitic elements can be arranged as a plurality of rows of second parasitic, wherein at least some of the second parasitic elements that are positioned in a middle region of the antenna are located farther forwardly from the reflector than are other of the second parasitic elements that are positioned at a periphery of the antenna array.
The present invention will be described below with reference to the drawings, in which several embodiments of the present invention are shown. It should be understood, however, that the present disclosure may be implemented in many different ways, and is not limited to the example embodiments described below. In fact, the embodiments described hereinafter are intended to make a more complete disclosure of the present disclosure and to adequately explain the scope of the present disclosure to a person skilled in the art. It should also be understood that the embodiments disclosed herein can be combined in various ways to provide many additional embodiments.
In the drawings, the same reference signs present the same elements. In the drawings, for the sake of clarity, the sizes of certain features may be modified.
It should be understood that, the wording in the specification is only used for describing particular embodiments and is not intended to limit the present invention. All the terms used in the specification (including technical and scientific terms) have the meanings as normally understood by a person skilled in the art, unless otherwise defined. For the sake of conciseness and/or clarity, well-known functions or constructions may not be described in detail.
The singular forms “a/an” and “the” as used in the specification, unless clearly indicated, all contain the plural forms. The words “comprising”, “containing” and “including” used in the specification indicate the presence of the claimed features, but do not preclude the presence of one or more additional features. The wording “and/or” as used in the specification includes any and all combinations of one or more of the items listed. The phases “between X and Y” and “between about X and Y” as used in the specification should be construed as including X and Y. As used herein, phrases such as “between about X and Y” mean “between about X and about Y”. As used herein, phrases such as “from about X to Y” mean “from about X to about Y.”
In the specification, when an element is referred to as being “on”, “attached” to, “connected” to, “coupled” with, “contacting”, etc., another element, it can be directly on, attached to, connected to, coupled with or contacting the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on”, “directly attached” to, “directly connected” to, “directly coupled” with or “directly contacting” another element, there are no intervening elements present. In the specification, references to a feature that is disposed “adjacent” another feature may have portions that overlap, overlie or underlie the adjacent feature.
In the specification, words describing spatial relationships such as “up”, “down”, “left”, “right”, “forth”, “back”, “high”, “low” and the like may describe a relation of one feature to another feature in the drawings. It should be understood that these terms also encompass different orientations of the apparatus in use or operation, in addition to encompassing the orientations shown in the drawings. For example, when the apparatus shown in the drawings is turned over, the features previously described as being “below” other features may be described to be “above” other features at this time. The apparatus may also be otherwise oriented (rotated 90 degrees or at other orientations) and the relative spatial relationships will be correspondingly altered.
The antenna assemblies according to embodiments of the present invention are applicable to various types of base station antennas, and may be particularly suitable for beamforming antennas.
As the number of arrays of radiating elements mounted on a reflector of a base station antenna increases, the spacing between radiating elements of different arrays is typically decreased, which results in increased coupling interference between the arrays. This increased coupling interference may distort the radiation pattern of the antenna, which may degrade the antennas the beamforming performance. The coupling interference between the arrays may affect the radiation pattern in both the azimuth and elevation planes. Excessive coupling may affect not only the gain (due to coupling loss), but also distort the shape of the radiation pattern and/or degrade the cross-polarization discrimination (CPR) performance of the antenna.
Pursuant to embodiments of the present invention, techniques are provided for creating a symmetrical, balanced electromagnetic environment in the vicinity of the linear arrays of a base station antenna in which there is with low coupling between closely spaced radiating elements. This symmetrical, balanced electromagnetic environment may exhibit balanced, symmetrical coupling in the far field and low coupling levels in the near field. Since the coupling interference between radiating elements is symmetrical and/or balanced, distortion of the radiation pattern may be reduced, which may improve the CPR performance of the antenna. Further, according to some embodiments of the present invention, the RF energy couples from a first radiating element to a parasitic element before potentially coupling to a second radiating element and that therefore there is a longer transmission path between the first and second radiating elements, and that therefore there is a longer transmission path between the first and second radiating, thereby reducing near field coupling between adjacent radiating elements. With the antenna assembly in accordance with some embodiments of the present invention, the coupling interference between adjacent linear arrays may be reduced, thus improving the isolation performance. Further, with the antenna assembly in accordance with some embodiments of the present invention, the shape of the radiation pattern and/or the CPR performance of the antenna may also be improved.
Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings.
Referring to
As shown in
As shown in
Further, parasitic elements 230 for the arrays 220 of radiating elements 222 may also be mounted on the reflector 210. The parasitic elements 230 may be, for example, conductive elements that are mounted forwardly of the reflector 210 adjacent one or more of the radiating elements 222. The parasitic elements 230 may be configured to shape the radiation pattern of the one or more adjacent radiating elements 222. For example, parasitic elements 230 may be designed to narrow the beamwidth of the radiation pattern(s) of the one or more adjacent radiating elements 222 in the azimuth plane. In some cases, the parasitic elements 230 may comprise dipoles and may have lengths that are approximately the same length as dipoles that are included in the adjacent radiating elements 222. The parasitic elements 230 are not coupled to a feed network of the antenna that couples RF signals to and from the arrays 220 of radiating elements 222.
The parasitic elements 230 may be placed around the arrays 220 of radiating elements 222 or between adjacent radiating elements 222. Some of the parasitic elements 230 may be positioned to act as isolators between adjacent radiating elements 222 to increase the isolation and thereby reduce the coupling interference between the adjacent radiating elements 222. Other parasitic elements 230 may be placed around the arrays 220 of radiating elements 222 and may interact with the respective radiating elements 222. For example, in operation, the parasitic elements 230 may absorb radio waves emitted by the respective radiating elements 222 and then radiate the radio waves outward in different phases so as to favorably shape the resultant antenna beam by, for example, adjusting a beam width of the antenna beam.
The arrays 220 may be, for example, linear arrays of radiating elements 222 or two-dimensional arrays of radiating elements 222. In some embodiments, the arrays 220 of radiating elements 222 may extend substantially along the entire length of the base station antenna 100. In other embodiments, the arrays 220 of radiating elements 222 may extend only partially along the length of the base station antenna 100. The arrays 220 of radiating elements 222 may extend from a lower end portion to an upper end portion of the base station antenna 100 in a vertical direction V, which may be the direction of a longitudinal axis L of the base station antenna 100 or may be parallel to the longitudinal axis L. The vertical direction V is perpendicular to a horizontal direction H and a forward direction F (see
In the present embodiment, only four linear arrays 220 of radiating elements 222 are exemplarily shown: a plurality of (exemplarily shown as three here) first radiating elements that are arranged as a first vertically extending array 2201; a plurality of (exemplarily shown as three here) second radiating elements that are arranged as a second vertically extending array 2202; a plurality of (exemplarily shown as three here) third radiating elements that are arranged as a third vertically extending array 2203; and a plurality of (exemplarily shown as three here) fourth radiating elements that are arranged as a fourth vertically extending array 2204. The four arrays are adjacent each other in the horizontal direction H.
In other embodiments, additional arrays 220 of radiating elements 222 (e.g., one or more arrays of high band radiating elements, one or more arrays of mid-band radiating elements and/or one or more arrays of low band radiating elements) may be mounted on the reflector 210. The low-band radiating elements 222 may, for example, operate in the 617 MHz to 960 MHz frequency band, or one or more portions thereof, the mid band radiating elements 222 may, for example, operate in the 1427 MHz to 2690 MHz frequency band, or one or more portions thereof, and the high band radiating elements 222 may, for example, operate in the 3 GHz or 5 GHz frequency bands, or one or more portions thereof.
Further, as the arrays 220 of radiating elements 222 are spaced more closely together to improve the electronic scanning capabilities of the antenna in the azimuth plane, the spacing between the radiating elements 222 is reduced. This reduced spacing degrades the isolation between radiating elements 222 in adjacent arrays 220, especially between radiating elements (e.g., dipoles) that have the same polarization (also referred to as Co-pol isolation). Thus, it may be necessary to improve the isolation between radiating elements 222 in adjacent arrays 220 in order to improve the beamforming performance of the base station antenna 100. For this purpose, adjacent arrays 220 of radiating elements 222 may be staggered with respect to each other, that is, the feed points of the radiating elements 222 in two adjacent arrays 220 are staggered in a vertical direction (i.e., not horizontally aligned with each other). This increases the spatial distance between radiators (e.g., dipole radiators) of adjacent radiating elements 222 that have the same polarization, thereby improving the isolation. In other embodiments, two adjacent arrays 220 of radiating elements 222 may also be vertically aligned with one another.
Pursuant to embodiments of the present invention, in order to improve the radiation pattern generated by the arrays 220 to, for example, improve the CPR performance, the radiating elements 222 are arranged on the reflector in a symmetrical, balanced layout in terms of an electromagnetic coupling environment such that the coupling interferences between adjacent radiating elements 222 may exhibit improved balance, thereby improving the shape of the radiation pattern. Next, a partial schematic view of the arrays 220 of radiating elements 222 and a schematic view of the arrays of parasitic elements 230 of the antenna assembly 200 in accordance with some embodiments of the present invention will be described in detail with reference to
two adjacent radiating elements 222 in each sub-array are spaced apart by a first spacing (d), while radiating elements 222 from adjacent arrays that are adjacent each other are spaced apart by a second spacing (d′). In the present embodiment, the first spacing d is substantially equal to a second spacing d′.
Thus, the radiating elements 222 in accordance with some embodiments of the present invention may be mounted on the reflector 210 to have a substantially symmetrical layout. The “symmetrical layout” may be appreciated as: the spacings between a radiating element and all the adjacent radiating elements are substantially equal, such that the coupling interferences of adjacent radiating elements on said radiating element are also presented in a symmetrical manner. In this regard, the radiating elements shown in
In some embodiments, the first spacings between two adjacent radiating elements 222 in a given sub-array may be slightly deviated from each other due to the manufacturing process, in this case the average value of the first spacings may be calculated to serve as a first average spacing. Likewise, the second spacings between two adjacent radiating elements 222 in two adjacent arrays 220 may also be slightly deviated from each other, and the average value of the second spacings may be calculated to serve as a second average spacing. In order to obtain a relatively symmetrical layout, the absolute value of the difference between the first average spacing minus the second average spacing may be less than 10%, 5%, 2% or 1% of the first or second average spacing in specific embodiments of the present invention.
In order to further reduce the coupling interference and improve isolation between the arrays 220, in some embodiments of the invention, parasitic elements 230 may be provided around each radiating element 222. As shown in
The above-described arrangement of the first parasitic elements 2301 and the second parasitic elements 2302 is advantageous for several reasons. First, the first parasitic elements 2301 may reduce the coupling interference between adjacent arrays 220 and the second parasitic elements 2302 may reduce the coupling interference between adjacent radiating elements 222 in the same array 220, thereby further reducing the coupling interference effect on each radiating element 222 Second, parasitic elements are disposed not only on the left and right sides of each radiating element 222 but also on the upper and lower sides of each radiating element 222, thereby creating a relatively symmetrical isolation environment for each radiating element 222, which helps to improve the shape of the radiation pattern. Third, based on the enhanced isolation measures, the arrays 220 of radiating elements 222 may be spaced more closely together to maintain the compactness of the base station antenna 100.
The radiating elements 222, however, may be subjected to different intensities of coupling interference depending on their locations in front of the reflector 210. Typically, the radiating elements 222 in the middle region of the array formed by the four linear arrays 220 are subject to increased coupling interference from the surrounding radiating elements 222 as compared to the radiating elements 222 in the outer regions of the array. Pursuant to further embodiments of the present invention, different ones of the first parasitic elements 2301 and/or the second parasitic elements 2302 may be positioned at different distances forwardly of the reflector 210 (also referred to herein as “heights”) based on an intensity of the respective coupling interference experienced by the radiating elements 222 based on their respective locations within the array. For example, the height of the first parasitic element 2301 and/or the second parasitic element 2302 may be stepped down one or more times from the middle region towards the outer region of the arrays 220 of radiating elements 222.
Although exemplary embodiments of this disclosure have been described, those skilled in the art should appreciate that many variations and modifications are possible in the exemplary embodiments without materially departing from the spirit and scope of the present disclosure. Accordingly, all such variations and modifications are intended to be included within the scope of this disclosure as defined in the claims. The present disclosure is defined by the appended claims, and equivalents of these claims are also contained.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201911073578.9 | Nov 2019 | CN | national |
