Patent Application
20230395971
The present application claims priority under 35 U.S.C. § 119 to Chinese Patent Application Serial No. 202210960474.5, filed Aug. 11, 2022, and to Chinese Patent Application Serial No. 202210616612.8, filed Jun. 1, 2022, the entire content of each of which are incorporated herein by reference.
The present invention generally relates to radio communications and, more particularly, to base station antenna systems that include both passive and active antenna arrays.
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. Typically, the base station antennas are mounted on a tower or other raised structure, with the radiation patterns (also referred to herein as “antenna beams”) that are generated by the base station antennas directed outwardly.
A common base station configuration is the three sector configuration in which a cell is divided into three 120° “sectors” in the azimuth (horizontal) plane. A separate base station antenna provides coverage (service) to each sector. Typically, each base station antenna will include multiple vertically-extending columns of radiating elements that operate, for example, using second generation (“2G”), third generation (“3G”) or fourth generation (“4G”) cellular network protocols. These vertically-extending columns of radiating elements are typically referred to as “linear arrays,” and may be straight columns or columns in which some of the radiating elements are staggered horizontally. Most modern base station antennas include both “low-band” linear arrays of radiating elements that support service in some or all of the 617-960 MHz frequency band and “mid-band” linear arrays of radiating elements that support service in some or all of the 1427-2690 MHz frequency band. These linear arrays are typically formed using dual-polarized radiating elements, which allows each array to transmit and receive RE signals at two orthogonal polarizations.
Each of the above-described linear arrays is coupled to two ports of a radio (one port for each polarization). An RF signal that is to be transmitted by a linear array is passed from the radio to the antenna where it is divided into a plurality of sub-components, with each sub-component fed to a respective subset of the radiating elements in the linear array (typically each sub-component is fed to between one and three radiating elements). The sub-components of the RF signal are transmitted through the radiating elements to generate an antenna beam that covers a generally fixed coverage area, such as a sector of a cell. Typically these linear arrays will have remote electronic tilt (“RET”) capabilities which allow a cellular operator to change the pointing angle of the generated antenna beams in the elevation (vertical) plane in order to change the size of the sector served by the linear array. Since the antenna beams generated by the above-described 2G/3G/4G linear arrays generate static antenna beams, they are often referred to as “passive” linear arrays.
Most cellular operators are currently upgrading their networks to support fifth generation (“5G”) cellular service. One important component of 5G cellular service is the use of so-called multi-column “active” beamforming arrays that operate in conjunction with active beamforming radios to dynamically adjust the size, shape and pointing direction of the antenna beams that are generated by the active beamforming array. These active beamforming arrays are typically formed using “high-band” radiating elements that operate in higher frequency bands, such as some or all of the 3.3-4.2 GHz and/or the 5.1-5.8 GHz frequency bands. Each column of such an active beamforming array is typically coupled to a respective port of a beamforming radio. The beamforming radio may be a separate device, or may be integrated with the active antenna array. The beamforming radio may adjust the amplitudes and phases of the sub-components of an RF signal that are fed to each port of the radio in order to generate antenna beams that have narrowed beamwidths in the azimuth plane (and hence higher antenna gain). These narrowed antenna beams can be electronically steered in the azimuth plane by proper selection of the amplitudes and phases of the sub-components of an RF signal.
In order to avoid having to increase the number of antennas at cell sites, the above-described 5G antennas also often include passive linear arrays that support legacy 2G, 3G and/or 4G cellular services. In some cases, both the active beamforming arrays and the passive linear arrays may be included in a single base station antenna. Another solution for providing an antenna that supports both 2G/3G/4G and 5G cellular service is to mount a 5G active antenna module (i.e., a module that includes an active beamforming array and associated beamforming radio) on the rear surface of a passive base station antenna that includes a plurality of 2G, 3G, and/or 4G passive linear arrays. An opening is provided in the reflector of the passive base station antenna so that the antenna beams generated by the active beamforming array can be transmitted through the passive base station antenna. This design is advantageous as the active antenna module may be removable, and hence as enhanced 5G capabilities are developed, a cellular operator may replace the original active antenna module with an upgraded active antenna module without having to replace the passive base station antenna. Herein, the combination of a passive base station antenna that has an active antenna module mounted thereon is referred to as a “passive/active antenna system.”
Pursuant to embodiments of the present invention, base station antennas are provided that comprise a reflector assembly and a first radiating element having a first feed stalk and a first radiator. A base of the first feed stalk is adjacent the reflector assembly and the first radiator is adjacent a distal end of the first feed stalk. A center of the first radiator is offset from the base of the first feed stalk in a longitudinal direction that is parallel to a longitudinal axis of the base station antenna.
In some embodiments, the reflector assembly includes a main reflector, longitudinally-extending first and second reflector strips that extend from the main reflector and are spaced apart from each other in a transverse direction that is perpendicular to the longitudinal direction, and a transversely-extending third reflector strip that extends between the first and second reflector strips.
In some embodiments, the first radiating element may be mounted to extend forwardly from the third reflector strip. In such embodiments, the reflector assembly may include an opening that is bounded by an upper edge of the main reflector and the first through third reflector strips. In some embodiments, at least half of the first radiator may overlap this opening in a direction perpendicular to the main reflector.
In some embodiments, the base station antenna may further comprise a first RF port, the first radiating element is part of a first array of radiating elements that are all coupled to the first RF port, and a second radiating element that is part of the first array of radiating elements is mounted to extend forwardly from the first reflector strip.
In some embodiments, a third radiating element that is part of the first array of radiating elements is mounted to extend forwardly from the main reflector.
In some embodiments, the second radiating element has a second feed stalk and a second radiator, where a base of the second feed stalk is adjacent the reflector assembly and the second radiator is adjacent a distal end of the second feed stalk, and wherein a center of the second radiator is offset from the base of the second feed stalk in the transverse direction.
In some embodiments, the first feed stalk is a tilted feed stalk that extends forwardly from the third reflector strip in a first plane and the second feed stalk is a tilted feed stalk that extends forwardly from the first reflector strip in a second plane, where the first plane is substantially perpendicular to the second plane.
In some embodiments, the second radiating element extends forwardly from a portion of the first reflector strip that is widened in the transverse direction.
In some embodiments, front surfaces of the respective first and second reflector strips extend in a first plane that is positioned rearwardly of a plane defined by a front surface of the main reflector.
In some embodiments, the first reflector strip comprises a first integrated strip that is monolithic with the main reflector and a first auxiliary strip that is mounted on the first integrated strip, and the second reflector strip comprises a second integrated strip that is monolithic with the main reflector and a second auxiliary strip that is mounted on the second integrated strip.
In some embodiments, the first integrated strip and the first auxiliary strip together form a first tubular structure, and the second radiating element extends forwardly from a feedboard printed circuit board that is mounted on a forward surface of the first tubular structure.
In some embodiments, the first auxiliary strip includes a front wall that is parallel to a front surface of the main reflector and a sidewall that extends rearwardly from the front wall, and the first integrated strip includes a rear wall that is parallel to the front surface of the main reflector and a sidewall that extends forwardly from the rear wall.
In some embodiments, the second radiating element is mounted to extend forwardly from a feed board, and the feed board is mounted on the first auxiliary strip.
In some embodiments, the third reflector strip comprises a first transverse strip that extends in the transverse direction from the first auxiliary strip, a second transverse strip that extends in the transverse direction from the second auxiliary strip, and a transversely-extending crossbar that is connected to the first and second transverse strips.
Pursuant to additional embodiments of the present invention, base station antennas are provided that comprise a reflector assembly that extends in a longitudinal direction. The reflector assembly includes a main reflector that has a main reflecting surface and spaced-apart first and second integrated strips that are integral with and extend longitudinally from respective first and second opposed sides of the main reflector, a first auxiliary strip mounted on the first integrated strip, and a second auxiliary strip mounted on the second integrated strip. The first and second auxiliary strips are non-planar metal strips.
In some embodiments, the first and second auxiliary strips are bent sheet metal strips.
In some embodiments, the first auxiliary strip is mounted forwardly of the first integrated strip, and the second auxiliary strip is mounted forwardly of the second integrated strip.
In some embodiments, the first auxiliary strip has a front wall that is parallel to the main reflecting surface and a sidewall that extends rearwardly from the front wall.
In some embodiments, the first integrated strip has a rear wall that is parallel to the main reflecting surface and a sidewall that extends forwardly from the rear wall.
In some embodiments, the base station antenna further comprises at least one first insulating gasket interposed between the first integrated strip and the first auxiliary strip, and at least one second insulating gasket interposed between the second integrated strip and the second auxiliary strip.
In some embodiments, the first integrated strip and the first auxiliary strip together form a first reflector strip that has a tubular structure, the base station antenna further comprising a radiating element that extends forwardly from a first feedboard printed circuit board that is mounted on a front surface of the first reflector strip, and wherein the second integrated strip and the second auxiliary strip together form a second reflector strip that has a tubular structure.
In some embodiments, the base station antenna further comprises a third reflector strip that extends in a transverse direction between the first and second reflector strips.
In some embodiments, the radiating element is a first radiating element, the base station antenna further comprising a second radiating element that extends forwardly from a second feedboard printed circuit board that is mounted on a front surface of the third reflector strip, wherein the first and second radiating elements are both part of a first array of radiating elements and both the first and second radiating elements are coupled to a first radio frequency (“RF”) port of the base station antenna.
In some embodiments, a feed stalk of the first radiating element extends forwardly from the first reflector strip at an oblique angle and is tilted in a first direction and a feed stalk of the second radiating element extends forwardly from the third reflector strip at an oblique angle and is tilted in a second direction that is different from the first direction.
In some embodiments, the first array further comprises a third radiating element that extends forwardly from the main reflector, the third radiating element including a feed stalk that extends perpendicular to the main reflector.
In some embodiments, the first reflector strip includes a widened section that has an increased width in a transverse direction that is perpendicular to the longitudinal direction, and the first feedboard printed circuit board is mounted on the widened section.
In some embodiments, portions of the first reflector strip have a width in the transverse direction that is less than a width of the first feedboard printed circuit board.
Pursuant to further embodiments of the present invention, base station antennas are provided that comprise a reflector assembly having a main reflector that includes a forwardly-facing planar main reflecting surface and spaced-apart first and second tubular reflector strips that each have a front wall, a rear wall and first and second sidewalls, the first and second tubular reflector strips extending longitudinally from respective first and second opposed sides of the main reflector.
In some embodiments, the reflector assembly further includes first and second radio frequency choke sections that are positioned rearwardly of the main reflector.
In some embodiments, the first tubular reflector strip comprises a first integrated strip that is monolithic with the main reflector and a first auxiliary strip that is mounted on the first integrated strip, and wherein the second tubular reflector strip comprises a second integrated strip that is monolithic with the main reflector and a second auxiliary strip that is mounted on the second integrated strip.
In some embodiments, the first integrated strip forms the rear wall and at least one of the first and second sidewalls of the first tubular reflector strip, and the second integrated strip forms the front wall and at least one of the first and second sidewalls of the second tubular reflector strip.
In some embodiments, the base station antenna further comprises a first RF port and a first linear array of radiating elements that are all coupled to a first RF port, wherein a first of the radiating elements in the first linear array is mounted on the first tubular reflector strip.
In some embodiments, the reflector assembly further comprises a third reflector strip that extends transversely between distal end portions of the first and second tubular reflector strips.
In some embodiments, a second of the radiating elements in the first linear array is mounted on the third reflector strip.
In some embodiments, the first of the radiating elements in the first linear array includes a first tilted feed stalk that extends forwardly from the first tubular reflector strip at an oblique angle in a first plane, and the second of the radiating elements in the first linear array includes a second tilted feed stalk that extends forwardly from the third reflector strip at an oblique angle in a second plane.
In some embodiments, the first plane is substantially perpendicular to the second plane.
In some embodiments, a third of the radiating elements in the first linear array is mounted to extend forwardly from the main reflector, where the third of the radiating elements in the first linear array has a feed stalk that extends perpendicularly to the main reflector.
Pursuant to still further embodiments of the present invention, base station antennas are provided that comprise a reflector assembly having a main reflector that includes a forwardly-facing planar main reflector surface and spaced-apart first and second reflector strips that extend from respective first and second opposed sides of the main reflector. The first reflector strip includes a front wall that has a widened region that is wider in a transverse direction than are first and second narrowed regions of the front wall that are on either side of the widened section in a longitudinal direction of the first reflector strip, where the longitudinal direction is perpendicular to the transverse direction.
In some embodiments, the first reflector strip further includes an outer sidewall and an inner sidewall, wherein the inner sidewall comprises a plurality of discontinuous segments.
In some embodiments, the base station antenna further comprises a feedboard mounted on the widened region.
In some embodiments, the first reflector strip is a tubular reflector strip that has the front wall, a rear wall and first and second sidewalls.
In some embodiments, the reflector assembly further comprising a first RF choke that is positioned behind the main reflector, wherein a width of the first RF choke in the transverse direction is greater than widths of the first and second narrowed regions of the front wall.
In some embodiments, the first reflector strip comprises a first integrated strip that is monolithic with the main reflector and a first auxiliary strip that is mounted on the first integrated strip.
In some embodiments, the reflector assembly further comprising a third reflector strip that extends in the transverse direction from a distal end of the first reflector strip.
In some embodiments, a first portion of the third reflector strip is integral with the first auxiliary strip.
Pursuant to further embodiments of the present invention, base station antennas are provided that include a longitudinally-extending passive reflector assembly that includes a main reflector that has a main reflecting surface and spaced-apart first and second integrated strips that are integral with and extend longitudinally from respective first and second opposed sides of the main reflector. A first plurality of non-metal (dielectric) auxiliary strips are mounted on the first integrated strip, and a second plurality of auxiliary strips are mounted on the second integrated strip. Each dielectric auxiliary strip includes a respective forwardly-facing radiating element mounting surface.
In some embodiments, each of the dielectric auxiliary strips includes an outer wall that connects to a first side of the forwardly-facing radiating element mounting surface and an inner wall. One or more supports connect the inner wall to a second side of the forwardly-facing radiating element mounting surface. The outer wall and the inner wall may each be connected to the integrated strip by fasteners such as rivets (not shown). The forwardly-facing radiating element mounting surface may include a plurality of cable openings in some embodiments. In some embodiments, first through third feedboards are mounted on the auxiliary strip, and first through third radiating elements are mounted on the respective first through third feedboards. The first radiating element may be a low-band radiating element that is configured to operate in a first frequency band and the second and third radiating elements may be mid-band radiating elements that are configured to operate in a second frequency band that encompasses higher frequencies than the first frequency band. Metal ground planes of the second and third feedboards each have a smaller footprint than a dipole radiator printed circuit board of the respective second and third radiating elements.
Pursuant to embodiments of the present invention, passive base station antennas are provided that are suitable for use in passive/active antenna systems. The passive base station antennas according to embodiments of the present invention may have an improved reflector assembly that provides increased mechanical support and include features that improve the electronic scanning performance of an active beamforming array included in an active antenna module that is mounted on the passive base station antenna.
As discussed above, the reflector assembly of a passive base station antenna of a passive/active antenna systems (herein also referred to as the “passive reflector assembly”) may include a large opening that allows RF energy from the active beamforming array included in the active antenna module to transmit and receive RF signals through the passive base station antenna. Unfortunately, the large opening in the passive reflector assembly reduces the structural support provided by the passive reflector assembly. This can reduce the rigidity of the passive base station antenna, which may result in components of the passive base station antenna experiencing increased movement under high wind environments. Such increased movement can negatively impact the RF performance of the passive base station antenna, and may also increase the likelihood that components of the antenna are damaged. In order to provide increased structural support, the passive reflector assembly may include first and second longitudinally-extending “reflector strips” that extend on either side of the opening, and may also include a third transversely-extending reflector strip that connects upper edges of the first and second longitudinally-extending reflector strips. The first and second reflector strips may increase the rigidity of the passive reflector, and may also serve as mounting locations for radiating elements of selected linear arrays of the passive base station antenna. Unfortunately, however, the first and second reflector strips may also interfere with the RF performance of the beamforming array of the active antenna module. This is particularly true when the beamforming array is electronically scanned to large scanning angles in the azimuth plane, as at these scanning angles the first and second reflector strips may block the RF energy emitted by the radiating elements that are closest to the first and second reflector strips.
The passive base station antennas according to some embodiments of the present invention may include first and second longitudinally-extending tubular reflector strips that exhibit increased strength and rigidity. In some embodiments, each tubular reflector strip may be formed from multiple pieces of sheet metal. For example, each tubular reflector strip may comprise two pieces of sheet metal, where at least one of the pieces of sheet metal includes a generally U-shaped or L-shaped transverse cross-section. The two pieces may be attached together to form the tubular reflector strip. Insulating gaskets may be provided that space the two pieces of metal apart from each other to avoid inconsistent metal-to-metal contact between the two pieces that might give rise to passive intermodulation (“PIM”) distortion.
The reflector strips included in the passive base station antennas according to embodiments of the present invention may also include widened (e.g., in the transverse direction) sections that serve as mounting locations for feedboard printed circuit boards. For example, a first linear array of the passive base station antenna may include one or more radiating elements that extend from one or more feedboard printed circuit boards that are mounted on the first longitudinally-extending reflector strip, and a second linear array of the passive base station antenna may include one or more radiating elements that extend from one or more feedboard printed circuit boards that are mounted on the second longitudinally-extending reflector strip. The widened sections on the first and second reflector strips provide support for the feedboard printed circuit boards and ensure that the feedboard printed circuit boards do not bend. Regions of the first and second reflector strips that do not have feedboard printed circuit boards mounted thereon may be narrowed (e.g., in the transverse direction) as compared to the widened sections. The provision of these narrowed sections increases the size of the opening in the passive reflector (i.e., the width of the opening is increased everywhere except the locations where feedboard printed circuit boards are mounted on the first and second reflector strips). This increased width may improve the electronic scanning performance of the beamforming array of the active antenna module that is mounted behind the opening in the passive reflector assembly. The increased rigidity of the tubular reflector strips allows for the reduction in the width of much of each reflector strip without compromising the structural integrity of the passive base station antenna.
The radiating elements that extend from the feedboard printed circuit boards that are mounted on the reflector strips may, in some embodiment, have tilted feed stalks, so that the radiators of these radiating elements are positioned forwardly of the opening in the passive reflector assembly as explained, for example, in U.S. Patent Publication No. 2021/0305718, published Sep. 30, 2021 (herein “the '718 publication”), the entire content of which is incorporated herein by reference. In particular, the one or more radiating elements that extend from the one or more feedboard printed circuit boards that are mounted on the reflector strip that extends along the right side of the passive base station antenna (when the passive base station antenna is viewed from the front) may have feed stalks that extend forwardly and to the left, and the radiating elements that extend from the feedboard printed circuit boards that are mounted on the reflector strip that extends along the left side of the passive base station antenna may have feed stalks that extend forwardly and to the right. In some embodiments, a transversely-extending third reflector strip may be provided that connects the upper ends of the longitudinally-extending first and second reflector strips. One or more feedboard printed circuit boards may be mounted on the transversely-extending third reflector strip. The radiating elements that are mounted on the third reflector strip may also have tilted feed stalks that extend forwardly and downwardly so that radiators of these radiating elements are also positioned forwardly of the opening in the passive reflector assembly. The radiators of all of the radiating elements in the first linear array may be aligned along a first longitudinal axis in some embodiments, and the radiators of all of the radiating elements in the second linear array may be aligned along a second longitudinal axis in such embodiments.
In some embodiments, base station antennas are provided that include a reflector assembly and a first radiating element having a first feed stalk and a first radiator. A base of the first feed stalk is adjacent the reflector assembly and the first radiator is adjacent a distal end of the first feed stalk. A center of the first radiator is offset from the base of the first feed stalk in a longitudinal direction that is parallel to a longitudinal axis of the base station antenna.
In other embodiments, base station antennas are provided that include a reflector assembly that extends in a longitudinal direction. The reflector assembly includes a main reflector that has a main reflecting surface and spaced-apart first and second integrated strips that are integral with and extend longitudinally from respective first and second opposed sides of the main reflector. The reflector assembly further includes a first auxiliary strip that is mounted on the first integrated strip and a second auxiliary strip that is mounted on the second integrated strip, where the first and second auxiliary strips are non-planar metal strips.
In further embodiments, base station antennas are provided that include a reflector assembly having a main reflector that includes a forwardly-facing planar main reflecting surface and spaced-apart first and second tubular reflector strips that each have a front wall, a rear wall and first and second sidewalls, the first and second tubular reflector strips extending longitudinally from respective first and second opposed sides of the main reflector.
Finally, in other embodiments, base station antennas are provided that include a reflector assembly having a main reflector that includes a forwardly-facing planar main reflector surface and spaced-apart first and second reflector strips that extend from respective first and second opposed sides of the main reflector. The first reflector strip includes a front wall that has a widened region that is wider in a transverse direction than are first and second narrowed regions of the front wall that are on either side of the widened section in a longitudinal direction of the first reflector strip, where the longitudinal direction is perpendicular to the transverse direction.
Example embodiments of the present invention will now be discussed in further detail with reference to the drawings.
Referring to
Referring to
As will be discussed in greater detail below, each of the low-band and mid-band radiating elements 132, 142 may be implemented as dual-polarized radiating elements that include first and second radiators that transmit and receive RF energy at orthogonal polarizations. When such dual-polarized radiating elements are used, each of the low-band and mid-band linear arrays 130, 140 may be connected to a pair of the RF ports 118. The first RF port 118 is connected between a first port of a radio (e.g., a remote radio head mounted on the antenna tower 102 near the passive base station antenna 110) and the first polarization radiators of the radiating elements in the array, and the second RF port 118 is connected between a second port of a radio and the second polarization radiators of the radiating elements in the array. RF signals that are to be transmitted by a selected one of the linear arrays 130, 140 are passed from the radio to one of the RF ports 118, and passed from the RF port 118 to a power divider (or, alternatively, a phase shifter assembly that includes a power divider) that divides the RF signal into a plurality of sub-components that are fed to the respective first or second radiators of the radiating elements in the linear array, where the sub-components are radiated into free space.
The passive reflector assembly 120 includes a main reflector 122 and spaced-apart first and second reflector strips 124-1, 124-2 that extend longitudinally from respective first and second opposed sides of the main reflector 122. The passive reflector assembly 120 may further include a third reflector strip 124-3 that extends in a transverse direction between the first and second reflector strips 124-1, 124-2. An opening 126 is defined between the first and second reflector strips 124-1, 124-2. For example, the opening 126 may be bounded by a top portion of the main reflector 122, the first and second reflector strips 124-1, 124-2, and the third reflector strip 124-3. Most of the low-band and mid-band radiating elements 132, 142 are mounted to extend forwardly from the main reflector 122. However, low-band linear arrays 130-1, 130-2 extend substantially the full length of the passive/active antenna system 100 and hence extend beyond the main reflector 122. The first and second reflector strips 124-1, 124-2 provide mounting locations for low-band radiating elements 132 that are positioned above the main reflector 122. The first and second reflector strips 124-1, 124-2 may be integral with the main reflector 122 so that the first and second reflector strips 124-1, 124-2 and the main reflector 122 will be maintained at a common ground voltage, which may be important for the performance of the low-band linear arrays 130-1, 130-2.
Each low-band radiating element 132 may comprise a slant −45°/+45° cross-dipole radiating element that includes a −45° dipole radiator 134-1 and a +45° dipole radiator 134-2 that are arranged to form a cross when the radiating element 132 is viewed from the front. The dipole radiators 134 may (but need not) extend in a plane that is parallel to a plane defined by the main reflector 122. The dipole radiators 134-1, 134-2 may be mounted on a feed stalk 136 of the radiating element 132. Conventionally, cross-dipole radiating elements extend forwardly from a main reflector surface of a reflector assembly with the feed stalks the radiating elements extending perpendicularly to the main reflector surface. The feed stalk may be configured to pass RF signals between the dipole radiators and an associated feed network, and may also be used to support the dipole radiators forwardly of the reflector assembly. The radiating elements 132 that extend forwardly from the main reflector 122 may have a conventional design where the feed stalks extend perpendicularly to the main reflector 122. However, the centers of the low-band radiating elements 132 that are mounted on the first and second reflector strips 124-1, 124-2 are above the opening 126, and hence conventional radiating elements cannot be readily used. Thus, the three uppermost low-band radiating elements 132 have so-called “tilted” feed stalks 136 that extend forwardly from the reflector strips 124-1, 124-2 at oblique angles. In particular, the base of each feed stalk 136 is mounted on one of the reflector strips 124-1, 124-2, and the feed stalk 136 extends at an angle so that the center of the cross defined by the dipole radiators 134-1, 134-2 is above the opening 126. In example embodiments, the feed stalks 136 may extend at an angle of about 30°-60° with respect to the front surface of the reflector strips 124-1, 124-2.
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There are two potential problems with the passive reflector assembly 120 shown in
Pursuant to embodiments of the present invention, passive base station antennas having improved passive reflector assemblies are provided. The passive reflector assemblies according to embodiments of the present invention may provide enhanced structural support, and may have reduced impact on the antenna beams generated by the active beamforming array of an active antenna module mounted behind the passive base station antenna. An example embodiment of a passive base station antenna 210 (with the radome removed) that includes a passive reflector assembly according to embodiments of the present invention is illustrated in
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The first and second reflector strips 224-1, 224-2 are integral or “monolithic” with the main reflector 222 (i.e., they are all formed from a single piece of sheet metal). As a result, the first and second reflector strips 224-1, 224-2 and the main reflector 222 will be maintained at a common voltage. This may be important for the performance of the low-band linear arrays (discussed below) since these arrays include radiating elements that are mounted to extend forwardly of both the main reflector 222 and the reflector strips 224. As shown best in
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Each of the low-band and mid-band linear arrays 230, 240 may generate relatively static antenna beams that provide coverage to a predefined coverage area (e.g., antenna beams that are each configured to cover a sector of a base station), with the only change to the coverage area occurring when the electronic downtilt angles of the generated antenna beams are adjusted (e.g., to change the size of the cell).
Each low-band radiating element 232 may comprise a slant −45°/+45° cross-dipole radiating element that includes a −45° dipole radiator 234-1 and a +45° dipole radiator 234-2 that are arranged to form a cross when the radiating element 232 is viewed from the front. The dipole radiators 234 may (but need not) extend in a plane that is parallel to a plane defined by the main reflector 222. The dipole radiators 234-1, 234-2 of each radiating element 232 are mounted on a feed stalk 236 of the respective radiating elements 232. The feed stalks 236 for low-band radiating elements 232-1 through 232-5 and 232-9 through 232-13 extend perpendicularly with respect to the plane defined by the main reflector 222. In contrast, the feed stalks 236 for low-band radiating elements 232-6 through 232-8 and 232-14 through 232-16 extend at oblique angles with respect to the plane defined by the main reflector 222. This allows the base of each feed stalk 236 to be mounted on one of the reflector strips 224 (which are adjacent the side or top of the antenna 210) while the distal ends of the feed stalks 236 are positioned inwardly from the base above the opening 226. Such feed stalks 236, which have distal ends that are not aligned with their bases along the forward direction, are referred to herein as “tilted” feed stalks 236. In example embodiments, the tilted feed stalks 236 may extend at an angle of about 30°-60° with respect to the plane defined by the main reflector 222, although other angles may be used. The aforementioned '718 publication discloses a wide variety of designs for radiating elements having tilted feed stalks. Any of the radiating elements disclosed in the '718 publication may be used to form the low-band radiating elements 232 that have radiators that are mounted in front of the opening 226 in the passive reflector assemblies according to embodiments of the present invention.
The bases (i.e., the rearward ends) of the feed stalks 236 of the low-band radiating elements 232 are adjacent the passive reflector assembly 220, as each radiating element 232 is mounted on a feedboard printed circuit board 238 that in turn is mounted on the passive reflector assembly 220. The dipole radiators 234 of low-band radiating elements 232 are adjacent the distal end of the respective feed stalks 236 (and typically mounted thereon). Since the feed stalks 236 of low-band radiating elements 232-6 through 232-8 and 232-14 through 232-16 are tilted, a center of each dipole radiator 234 of low-band radiating elements 232-6 through 232-8 and 232-14 through 232-16 is offset from the base of its associated feed stalk 236. For low-band radiating elements 232-8 and 232-16, the center of each dipole radiator 234 is offset from the base of its associated feed stalk 236 in the longitudinal direction. In contrast, for low-band radiating elements 232-6, 232-7 and 232-14, 232-15, the center of each dipole radiator 234 is offset from the base of its associated feed stalk 236 in the transverse direction. Thus, the feed stalks 236 of low-band radiating elements 232-8 and 232-16 each extend forwardly from the third reflector strip 224-3 in respective first planes and the feed stalks of low-band radiating elements 232-6, 232-7 and 232-14, 232-15 extend forwardly from the first or second reflector strips 224-1, 224-2 in respective second planes, where each first plane is substantially perpendicular to the second planes.
As can also be seen from
Each of the low-band linear arrays 230 is connected to a pair of the RF ports 218 via respective first and second feed networks (not shown). For example, for low-band linear array 230-1, a first of the RF ports 218 is connected to the first polarization radiators of the radiating elements 232 in the array 230-1 by a first feed network, and a second of the RF ports 218 is connected to the second polarization radiators of the radiating elements 232 in the array 230-1 by a second feed network. Each feed network may include a phase shifter assembly that sub-divides RF signals received from the RF port 218 into a plurality of sub-components, and that further imparts a phase progression to the sub-components so that the generated antenna beam will have a desired amount of electrical downtilt in the elevation plane, as is well understood by those of ordinary skill in the art. Each sub-component is then fed to one (or split between two) of the low-band radiating elements 232 in array 230-1, which radiate the sub-components into free space.
Each mid-band linear array 240 includes twelve mid-band radiating elements 242 that are arranged in respective vertically-extending columns. The mid-band linear arrays 240 do not extend the full length of the passive base station antenna 210, and instead only extend for the length of the main reflector 222. Thus, all of mid-band radiating elements 242 extend forwardly from the main reflector 222.
The passive reflector assembly 220 includes a revised design that may improve both the mechanical and electrical performance as compared to the passive reflector assembly 120 of passive base station antenna 110 that is described above. In particular, as is shown in
The first and second auxiliary strips 310-1, 310-2 may each be formed from stamped sheet metal that is formed (bent) into the shapes shown in
The outer sidewall 314-2 of the first auxiliary strip 310-2 may abut the outer sidewall 304-2 of the second integrated strip 300-2, and a dielectric gasket 330 may be disposed therebetween. Dielectric rivets 332 may be used to attach the outer sidewall 314-2 of the second auxiliary strip 310-2 to the outer sidewall 304-1 of the second integrated strip 300-2. The inner sidewall 316-2 of the second auxiliary strip 310-2 may similarly abut the inner sidewall 306-2 of the second integrated strip 300-2, and another dielectric gasket 330 may be disposed therebetween. The rear wall 318-2 of the second auxiliary strip 310-2 may abut the rear wall 302-2 of the second integrated strip 300-2, and one or more dielectric gaskets 330 may be disposed therebetween. Additional dielectric rivets 332 may be used to attach the rear wall 318-2 of the second auxiliary strip 310-2 to the rear wall 302-2 of the second integrated strip 300-2.
As shown best in
The front surface 312-2 of the second auxiliary strip 310-2 includes a pair of widened sections 320 that are interposed between narrowed sections 322 of the front surface 312-2. Each widened section 320 is widened in the transverse direction as compared to the remainder of the second auxiliary strip 310-2 (except for the distal end portion). As shown in
Referring to
As discussed above with reference to
As is best shown in
In some embodiments, a frequency selective surface (“FSS”) may be positioned in the opening 226. The FSS may be coplanar with the opening 226, in front of the opening 226 or behind the opening 226. The FSS can have a grid pattern such as a grid pattern of metal patches and/or other metal structures. The metal patches/structures may be arranged in one or more layers. In some embodiments, the FSS may be formed on a substrate such as, for example, a printed circuit board. In other embodiments, the FSS may be formed in sheet metal. In some embodiments, the opening 226 may comprise an FSS that is formed in the metal sheet 221. While in such embodiments the opening 226 is a non-conventional opening in that it comprises a large plurality of small openings formed in the metal sheet 221, it is still considered an opening for purposes of the present disclosure as the FSS structure will be substantially invisible to RF energy emitted by the beamforming array 160 (as will be discussed below), and hence with respect to such RF energy the FSS structure is the equivalent of a single large physical opening in the metal sheet 221.
As noted above, the FSS may be configured to allow RF energy emitted by the high band radiating elements 162 in the beamforming array 160 to pass therethrough, while the FSS reflects RF energy in lower frequency bands (and specifically, low-band RF signals that are emitted by the low-band radiating elements 232. The grid pattern can be arranged in any suitable manner and may be symmetric or asymmetric across a width and/or length of the FSS. The grid pattern may comprise sub-wavelength periodic microstructures.
Turning to the drawings,
Referring to
Referring to
Referring again to
Referring to
The rails 500 of passive reflector assembly 420 and the tubular structures 340 of passive reflector assembly 220 may exhibit comparable strength and rigidity. However, the width of each rail 500 in the transverse direction, which may match the width of the narrowed sections 542 of the reflector strips 424, may be less than the widths of the tubular structures 340 of passive reflector assembly 220 so that opening 426 is larger than opening 226. The enlarged opening 426 may further improve the RF performance of the beamforming array 160 mounted behind the opening 426.
While the above-discussed passive reflector assemblies according to embodiments of the present invention can dramatically improve the performance of the beamforming array 160 included in the active antenna module 150, in many applications the beamforming array 160 may need to scan the generated antenna beams to very wide angles in the azimuth plane, such as angles of 50° or more. When the peak of the antenna beam generated by the beamforming array 160 is scanned to a large electronic scanning angle, the antenna beam is pointed more toward one of the two sides of the passive reflector assembly, which tends to increase the amount of the RF radiation that is directed toward the longitudinally-extending reflector strip on that side of the antenna. Since the reflector strip is formed of metal, the RF radiation that impinges on the reflector strip is typically reflected backwardly, which acts to decrease the gain of the antenna beam, and which may also result in further reflections that can cause destructive cancellation, further degrading performance. The reflector strip will primarily reflect the RF radiation emitted by the outer columns of the beamforming array that are closest to the reflector strip on the side of the passive reflector assembly to which the antenna beam is being electronically scanned. As discussed above, the passive reflector assemblies according to embodiments of the present invention have widened openings between the longitudinally-extending reflector strips, which helps reduce the extent to which the reflector strips degrade the performance of the beamforming array 160. However, in some applications (and particularly applications that require very wide electronic scanning in the azimuth plane), the reflector strips may still unacceptably impact the performance of the beamforming array 160.
Another potential complication is that in some applications, the outer mid-band linear arrays (e.g., linear arrays 240-1 and 240-4 in
Pursuant to further embodiments of the present invention, base station antennas are provided that include passive reflector assemblies that have longitudinally-extending reflector strips that each include one or more auxiliary strips that are formed of dielectric materials. These dielectric auxiliary strips may be mounted on the longitudinally-extending reflector strips, and the radiating elements that extend on either side of the opening in the passive reflector assembly for the beamforming array may be mounted on the dielectric auxiliary strips. The use of these dielectric auxiliary strips may improve the performance of the high-band array in at least two ways. First, when these dielectric auxiliary strips are used, the need for the longitudinally-extending metal reflector strips to have inner sidewalls may be reduced or eliminated, as the dielectric auxiliary strips may perform the support function of the inner sidewalls of the reflector strips. This is advantageous because, in practice, the inner sidewalls of the longitudinally-extending reflector strips may be the primary element of the reflector strips that reflects radiation emitted by the beamforming array 160. Second, while the ground planes on the feedboards for the radiating elements 232, 242 that are mounted on the longitudinally-extending reflector strips 224-1, 224-2 of the passive reflector assembly 220 may still reflect radiation emitted by the beamforming array 160, the ground planes on the feedboards may be designed to cover less than half the area of the support surface of the dielectric auxiliary strips, and hence the amount of RF radiation from the beamforming array 160 that is reflected may be further reduced.
Referring to
As can further be seen in
As described above, the radiating elements 232, 242 that are mounted on the reflector strips of the passive reflector assemblies according to embodiments of the present invention are typically mounted on feed board printed circuit boards. As is well known in the art, feed board printed circuit boards typically include a metal ground plane on one side thereof and metal traces on the other side thereof that carry RF signals between the feed board printed circuit board and the radiating element(s) mounted thereon. The ground plane on the feed board printed circuit boards, however, will reflect RF radiation incident thereon such as RF radiation emitted by the beamforming array 160. Accordingly, pursuant to a further aspect of the present invention, feed board printed circuit boards are provided that have smaller metal ground planes.
As shown in
Each of the dielectric auxiliary strips 650 includes an outer wall 652 that connects to a first side of the forwardly-facing radiating element mounting surface 654 and an inner wall 656. One or more supports 658 connect the inner wall 656 to a second side of the forwardly-facing radiating element mounting surface 654. The outer wall 652 and the inner wall 656 may each be connected to the integrated strip 624 by fasteners such as rivets (not shown). The forwardly-facing radiating element mounting surface 654 may include a plurality of cable openings 655 in some embodiments. In some embodiments, first through third feedboards 660, 670 are mounted on the auxiliary strip 624, and first through third radiating elements 232, 242 are mounted on the respective first through third feedboards 660, 670. The first radiating element may be a low-band radiating element 232 that is configured to operate in a first frequency band and the second and third radiating elements may be mid-band radiating elements 242 that are configured to operate in a second frequency band that encompasses higher frequencies than the first frequency band. Metal ground planes 672 of the second and third feedboards each have a smaller footprint than a dipole radiator printed circuit board of the respective second and third radiating elements 242.
While the present invention has been described above primarily with reference to the accompanying drawings, it will be appreciated that the invention is not limited to the illustrated embodiments; rather, these embodiments are intended to fully and completely disclose the invention to those skilled in this art. In the drawings, like numbers refer to like elements throughout. Thicknesses and dimensions of some components may be exaggerated for clarity.
Spatially relative terms, such as “under”, “below”, “lower”, “over”, “upper”, “top”, “bottom” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “under” or “beneath” other elements or features would then be oriented “over” the other elements or features. Thus, the exemplary term “under” can encompass both an orientation of over and under. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
Well-known functions or constructions may not be described in detail for brevity and/or clarity. As used herein the expression “and/or” includes any and all combinations of one or more of the associated listed items.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes” and/or “including” when used in this specification, specify the presence of stated features, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, operations, elements, components, and/or groups thereof.
Herein, the terms “attached”, “connected”, “interconnected”, “contacting”, “mounted” and the like can mean either direct or indirect attachment or contact between elements, unless stated otherwise.
It will also be appreciated that the various embodiments described above may be combined in any and all ways to provide additional embodiments.
The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202210616612.8 | Jun 2022 | CN | national |
| 202210960474.5 | Aug 2022 | CN | national |
