In order to reduce large sidelobes that may result from using a base station antenna with increased electronic downtilt, base station antennas according to the present disclosure may have a plurality of modules in which the columns of radiating elements of at least one of the modules are staggered or offset with respect to each other. For example, a multi-beam cellular antenna may include an antenna array having a plurality of modules, each module comprising at least three columns of radiating elements each having first polarization radiators, wherein the columns of radiating elements of at least one of the modules are staggered with respect to each other; and an antenna feed network configured to couple at least a first input signal and a second input signal to each first polarization radiator of each of the radiating elements included in a first of the plurality of modules.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of priority to Chinese Patent Application 202010385103.X, filed on May 9, 2020, the disclosure of which is herein incorporated by reference in its entirety for all purposes.

TECHNICAL FIELD

The present invention generally relates to radio communications and, more particularly, to base station antennas for cellular communications systems.

BACKGROUND

Cellular communications systems are well known in the art. In a typical cellular communications system, a geographic area is divided into a series of regions that are referred to as “cells,” and each cell is served by a base station. The base station may include baseband equipment, radios and base station antennas that are configured to provide two-way radio frequency (“RF”) communications with subscribers that are positioned throughout the cell. In many cases, the cell may be divided into a plurality of “sectors,” and separate base station antennas provide coverage to each of the sectors. The antennas are often mounted on a tower, with the radiation beam (“antenna beam”) that is generated by each antenna directed outwardly to serve a respective sector. Typically, a base station antenna includes one or more phase-controlled arrays of radiating elements, with the radiating elements arranged in one or more vertical columns when the antenna is mounted for use. Herein, “vertical” refers to a direction that is perpendicular to the horizontal plane that is defined by the horizon. Reference will also be made to the azimuth plane, which is a horizontal plane that bisects the base station antenna, and to the elevation plane, which is a plane extending along the boresight pointing direction of the antenna that is perpendicular to the azimuth plane.

A common base station configuration is the “three sector” configuration in which a cell is divided into three 120° sectors in the azimuth plane. A base station antenna is provided for each sector. In a three sector configuration, the antenna beams generated by each base station antenna typically have a Half Power Beamwidth (“HPBW”) in the azimuth plane of about 65° so that each antenna beam provides good coverage throughout a 120° sector. Three such base station antennas provide full 360° coverage in the azimuth plane. Typically, each base station antenna will include one or more so-called “linear arrays” of radiating elements that includes a plurality of radiating elements that are arranged in a generally vertically-extending column. Each radiating element may have an azimuth HPBW of approximately 65° so that the antenna beam generated by the linear array will have a HPBW of about 65° in the azimuth plane. By providing a phase-controlled column of radiating elements extending along the elevation plane, the HPBW of the antenna beam in the elevation plane may be narrowed to be significantly less than 65°, with the amount of narrowing increasing with the length of the column in the vertical direction.

As the volume of cellular traffic has grown, cellular operators have added new cellular services in a variety of new frequency bands. When these new services are introduced, the existing “legacy” services typically must be maintained to support legacy mobile devices. In some cases, it may be possible to use linear arrays of so-called “wide-band” or “ultra-wide-band” radiating elements to support service in the new frequency bands. In other cases, however, it may be necessary to deploy additional linear arrays (or multi-column arrays) of radiating elements to support service in the new frequency bands. Due to local zoning ordinances and/or weight and wind loading constraints, there is often a limit as to the number of base station antennas that can be deployed at a given base station. Thus, to reduce the number of antennas, many operators deploy so-called “multiband” base station antennas that include multiple linear arrays of radiating elements that communicate in different frequency bands to support multiple different cellular services.

Additionally, or alternatively, dual-beam antennas (or multi-beam antennas) may be used to reduce the number of antennas on the tower. A key aspect of such multi-beam antennas is the use of a beamforming network (BFN). For example, the antenna11ofFIGS.1A and1Bemploys a 2×2 BFN10having a 3 dB 90° hybrid coupler shown at12and forms both beams A and B in azimuth plane at signal ports14. (2×2 BFN means a BFN creating 2 beams by using 2 columns). The two radiator coupling ports16are connected to antenna elements also referred to as radiators, and the two ports14are coupled to the phase shifting network, which is providing elevation beam tilt (seeFIG.1B). An antenna may be both multi-beam and multi-band; that is, an antenna may be configured with both multiple linear arrays of radiating elements that communicate in different frequency bands, with at least some of those radiating elements coupled to one or more BFN to provide directionalized beams in the azimuth plane.

However, as discussed in U.S. Pat. No. 9,831,548, which is incorporated by reference, the main drawback of the prior art antenna ofFIGS.1A and1Bis that more than 50% of the radiated power is wasted and directed outside of the desired 60° sector for a 6-sector application, and the azimuth beams are too wide (150°@−10 dB level), creating interference with other sectors. Moreover, the low gain and large backlobe (about −11 dB) are not acceptable for modern systems due to high interference generated by one antenna into other cells.

SUMMARY

In order to reduce large sidelobes that may result from using a base station antenna with increased electronic downtilt, the present disclosure provides base station antennas in which the columns of at least one of the modules are staggered or offset with respect to each other. In some embodiments, a majority of the modules that are present within the base station antenna may include such staggered column arrangements.

According to some aspects of the present disclosure, a multi-beam cellular antenna is provided. The multi-beam cellular antenna may include an antenna array having a plurality of modules, each module comprising at least three columns of radiating elements each having first polarization radiators, wherein the columns of radiating elements of at least one of the modules are staggered with respect to each other; and an antenna feed network configured to couple at least a first input signal and a second input signal to each first polarization radiator of each of the radiating elements included in a first of the plurality of modules.

In some embodiments, the radiating elements of the columns of radiating elements of a majority of the modules are staggered with respect to each other. In some embodiments, the radiating elements of the columns of radiating elements of at least one of the modules are aligned with respect to each other.

A first module of the plurality of modules may include three columns of radiating elements, and wherein a second module of the plurality of modules may include four columns of radiating elements. In some embodiments, the three columns of radiating elements of the first module may each include an equal number of radiating elements. In some embodiments, a first column of radiating elements of the first module may include a number of radiating elements that is less than a number of radiating elements included in a second column of the first module. The antenna feed network may include a 2×3 beamforming network that couples the first and second input signals to the radiating elements of the first module and a 2×4 beamforming network that couples the first and second input signals to the second module. The 2×4 beamforming network may include at least one variable power divider.

The antenna array may be configured to generate a first beam that points in a first direction responsive to the first input signal and to generate a second beam that points in a second direction responsive to the second input signal.

The radiating elements may be cross-polarized radiating elements.

According to some aspects of the present disclosure, a multi-beam cellular antenna is provided. The multi-beam cellular antenna may include a plurality of first modules each having a first number of columns of radiating elements. The radiating elements of the columns of at least one of the first modules may be staggered with respect to each other. The multi-beam cellular antenna may also include a plurality of second modules each having a second number of columns of radiating elements. The radiating elements of the columns of at least one of the second modules may be staggered with respect to each other. The multi-beam cellular antenna may also include an antenna feed network that includes at least one 2×4 beamforming network that couples first and second input signals to the radiating elements of one of the plurality of first modules, and at least one 2×3 beamforming network that couples the first and second input signals to the radiating elements of one of the plurality of second modules.

The radiating elements of the columns of radiating elements of a majority of the first modules may be staggered with respect to each other. The radiating elements of the columns of radiating elements of at least one of the second modules may be aligned with respect to each other. Each first module may include four columns of radiating elements, and each second module of the plurality of modules may include three columns of radiating elements. The 2×4 beamforming network may include at least one variable power divider.

The plurality of first modules and plurality of second modules may be configured to generate a first beam that points in a first direction responsive to the first input signal and may be configured to generate a second beam that points in a second direction responsive to the second input signal.

According to some aspects of the present disclosure, a multi-beam cellular antenna is provided. The multi-beam cellular antenna may include a plurality of first modules each having a first number of columns of radiating elements. The radiating elements of the columns of at least one of the first modules may be staggered with respect to each other. The multi-beam cellular antenna may also include a second module having a second number of columns of radiating elements. The radiating elements of the columns of the second module may be staggered with respect to each other. The multi-beam cellular antenna may also include an antenna feed network that includes at least one 2×4 beamforming network that couples first and second input signals to the radiating elements of one of the plurality of first modules, and at least one 2×3 beamforming network that couples the first and second input signals to the radiating elements of the second module.

A first column of radiating elements of the second module may include a number of radiating elements that is less than a number of radiating elements included in a second column of the second module.

The multi-beam cellular antenna may further include a third module having the second number of columns of radiating elements. The columns of the third module may be staggered with respect to each other. Each column of the third module may include an equal number of radiating elements as the first column of radiating elements of the second module.

DETAILED DESCRIPTION

As discussed in the above-referenced U.S. Pat. No. 9,831,548, a base station antenna that is currently of interest includes a plurality of modules of radiating elements.

FIGS.2and3illustrate a perspective view of a base station antenna300.FIG.2is a perspective view of the base station antenna300, whileFIG.3is a front view of the base station antenna300with the radome removed that schematically illustrates the modules of radiating elements included in the antenna300.

As shown inFIG.2, the base station antenna300is an elongated structure that extends along a longitudinal axis L. The base station antenna300may have a tubular shape with a generally rectangular cross-section. The antenna300includes a radome310and a bottom end cap312. A plurality of RF connectors314may be mounted in the bottom end cap312. The antenna300is typically mounted in a vertical configuration (i.e., the longitudinal axis L may be generally perpendicular to a plane defined by the horizon when the antenna300is mounted for normal operation).

As seen inFIG.3, the base station antenna300may include one or more modules80,90that each include one or more columns74of radiating elements76. The radiating elements76may be radiating elements configured to provide service in one or more than one frequency bands, such as the 1.7-2.7 GHz frequency band, the 3.4-3.8 GHz frequency band, and/or the 5.1-5.8 GHz frequency band. Each of the radiating elements76may be a cross-polarized radiating element. The base station antenna300ofFIGS.2-3includes two three-column modules80and three four-column modules90, though the number of modules and the number of columns per module may vary in different embodiments. Moreover, althoughFIG.3shows that each column74of radiators76of both the three-column modules80and the four-column modules90has two radiators76, in some applications a different number of radiators76may be present in each of the columns74of a module80,90.

Each three-column antenna module80of the base station antenna300ofFIGS.2and3is fed by first and second 2×3 BFNs. The first 2×3 BFN may form antenna beams for a first polarization, e.g., a slant −45° polarization, and the second 2×3 BFN may be configured to form antenna beams for a second polarization, e.g., a +45° polarization. Similarly, each four-column module90may be fed by first and second 2×4 BFNs, with the first 2×4 BFN configured to form antenna beams for a first polarization, e.g., a slant −45° polarization, and the second 2×4 BFN configured to form antenna beams for a second polarization, e.g., a +45° polarization. The 2×3 and 2×4 BFNs are not shown inFIG.3, but examples of each are shown in incorporated U.S. Pat. No. 9,831,548.

Although the incorporated U.S. Pat. No. 9,831,548 discusses that the base station antenna300results in radiation patterns having low sidelobes in both the azimuth and elevation planes, the present disclosure results from the recognition that a large sidelobe may be present when there is a large degree of electronic downtilt applied to the antenna beams, e.g., from phase shifting. Increasing electronic downtilt is frequently desirable as it may be used to reduce the size of a cell when a new adjacent cell is added by a network operator. One way of increasing capacity is to use a larger number of smaller cells.FIG.10Ashows an elevation pattern1000for the base station antenna300ofFIGS.2-3for one polarization at the large degree of downtilt, along with the discovered sidelobe1020. It may also be seen that there is an unequal balance in the sidelobes between the large sidelobe1020and a smaller sidelobe1030on the other side of the main lobe.

In order to reduce large sidelobes that may result from using a base station antenna with increased electronic downtilt, the present disclosure provides base station antennas in which the columns of at least one of the modules80,90are staggered or offset with respect to each other. In some embodiments, a majority of the modules80,90that are present within the base station antenna may include such staggered column arrangements.

The presence of staggered column arrangements may help to equalize RF energy on both sides of the main lobe. Although this may result in an increase in a lower sidelobe (e.g., the low sidelobe1030), there is an overall positive result and improvement in performance of antennas with such arrangements resulting from the reduction in a higher sidelobe (e.g., the high sidelobe1020).

FIG.4is a front view of a base station antenna400with the radome removed that schematically illustrates the modules of radiating elements included in the antenna400. As with the base station antenna300ofFIG.2, the base station antenna400is an elongated structure that extends along a longitudinal axis with a radome, bottom end cap, and RF connectors that are similar to those discussed with respect toFIG.2. For brevity, discussion of these components is not duplicated herein.

As seen inFIG.4, one or more modules180,190comprising staggered columns74of radiating elements76may be provided in the base station antenna400. The radiating elements76may be radiating elements configured to provide service in one or more than one frequency bands, such as the 1.7-2.7 GHz frequency band, the 3.4-3.8 GHz frequency band, and/or the 5.1-5.8 GHz frequency band. Each of the radiating elements76may be a cross-polarized radiating element.

The base station antenna400ofFIG.4includes one staggered three-column module180, and three staggered four-column modules190and one non-staggered three-column module80. However, the number of staggered modules and the number of columns per staggered module may vary in different embodiments. Moreover, althoughFIG.4shows that each column74of radiators76of both the three-column staggered module180and the four-column staggered modules190has two radiators76, in some applications a different number of radiators76may be present in each of columns74of a staggered module180,190.

In some embodiments, the base station antenna400may include one or more than one non-staggered three-column module80. In some embodiments, the base station antenna400may include one or more than one non-staggered four-column module90. As can be seen from comparing a length L1 parallel to the longitudinal axis L of the staggered three-column module180with a length L2 parallel to the same axis of the non-staggered or aligned three-column module80, the length of a staggered module may be greater than a non-staggered module. In order to size the base station antenna400to satisfy, for example, local zoning ordinances and/or weight and wind loading constraints, a non-staggered module may be used on either or both ends of the base station antenna400to reduce the overall length thereof.

Each staggered three-column antenna module180of the base station antenna400ofFIG.4is fed by first and second 2×3 BFNs. The first 2×3 BFN may form antenna beams for a first polarization, e.g., a slant −45° polarization, and the second 2×3 BFN may be configured to form antenna beams for a second polarization, e.g., a +45° polarization. Similarly, each staggered four-column module190may be fed by first and second 2×4 BFNs, with the first 2×4 BFN configured to form antenna beams for a first polarization, e.g., a slant −45° polarization, and the second 2×4 BFN configured to form antenna beams for a second polarization, e.g., a +45° polarization. The 2×3 and 2×4 BFNs are not shown inFIG.4, but are illustrated respectively inFIGS.7and8and described in greater detail below.

FIG.5is a front view of a base station antenna500with the radome removed that schematically illustrates the modules of radiating elements included in the antenna500. The base station antenna500ofFIG.5is similar to the base station antenna400ofFIG.4, except that the base station antenna500ofFIG.5omits the staggered three-column module180ofFIG.4in favor of an additional staggered four-column module190. Each module80,190of the base station antenna500ofFIG.5is fed by a respective pair of either 2×3 or 2×4 BFNs which are illustrated respectively inFIGS.7and8and described in greater detail below.

FIG.6is a front view of a base station antenna600with the radome removed that schematically illustrates the modules of radiating elements included in the antenna600. The base station antenna600ofFIG.6is similar to the base station antennas400ofFIG.4and500ofFIG.5, except that the base station antenna600ofFIG.6includes a staggered three-column module280at one end of the base station antenna600, with one radiating element76per column74. Additionally, a staggered three-column module380is provided at the opposite end of the base station antenna600that includes at least one column74-2with a different number of radiating elements76than a different column (e.g. column74-1) of the same module380. The result is that there are five radiating elements76in the staggered three-column module380ofFIG.6, as opposed to six radiating elements76in the staggered three-column module180ofFIG.4. Each module280,380, and190of the base station antenna600ofFIG.6is fed by a respective pair of either 2×3 or 2×4 BFNs which are illustrated respectively inFIGS.7and8and described in greater detail below.

FIG.7is a block diagram of a 2×3 beam forming network700configured for use with modules of base station antennas having staggered column arrangements such as those illustrated inFIGS.4-6. The 2×3 beam forming network700ofFIG.7is configured to form2antenna beams with 3 staggered columns of radiators for signals received at signal ports710-1and710-2. A 90° hybrid coupler720is provided, which may be a 3 dB coupler. In some embodiments, the splitting coefficient of the 90° hybrid coupler720may be varied, and different amplitude distributions of the beams can be obtained for column coupling ports750-1,750-2, and750-3: from uniform (1-1-1) to heavy tapered (0.4-1-0.4). With equal splitting (3 dB coupler) 0.7-1-0.7 amplitudes are provided. Additionally, an equal splitter730is provided between one of the ports of the 90° hybrid coupler720and two of the column coupling ports (in this case, column coupling ports750-1and750-3). In some embodiments, the splitter730may be a Wilkinson divider with a 180° Shiffman phase shifter. However, equal phase dividers can be used. Further, 180° phase shifting of signals transmitted to one of the column coupling ports (in this case, column coupling port750-3) is performed by a dipole element with 180° rotation740. In some embodiments, the beam forming network700may include or implement a Butler matrix.

FIG.8is a block diagram of a 2×4 beam forming network800configured for use with modules of base station antennas having staggered column arrangements such as those illustrated inFIGS.4-6. The 2×4 beam forming network800ofFIG.8, is configured to form 2 antenna beams with 4 staggered columns of radiators for signals received at signal ports810-1and810-2. A 90° hybrid coupler820is provided, which may be a 3 dB coupler. Two variable power dividers830-1and830-2are provided between two of the ports of the 90° hybrid coupler820and the column coupling ports850-1to850-4). Further, 180° phase shifting of signals transmitted to two of the column coupling ports (in this case, column coupling ports850-1and850-4) is performed by respective dipole elements with 180° rotation840-1,840-2arranged between the column coupling ports and the variable power dividers830-1,830-2. In some embodiments, the beam forming network800may include or implement a Butler matrix.

FIG.9is a front view of a multi-band base station antenna900with a radome removed that schematically illustrates the modules of radiating elements included in the antenna900. The base station antenna900ofFIG.9is similar to the base station antenna600ofFIG.6, except that first and second columns970-1,970-2of radiating elements974are also shown. The radiating elements974may be used to provide service in a different frequency band than the radiating elements74of the modules180,190,280,380shown herein. For example, the radiating elements974may be used to provide service in some or all of the 617-960 MHz frequency band. The arrangement of the multi-band base station antenna900is provided as an example, and the radiating elements974may be used in the base station antenna500ofFIG.5without limitation.

Additionally, or alternatively, in some embodiments at least some of the radiating elements76described herein and the modules or base station antennas including such radiating elements76may be configured to provide a multi-input-multi-output (MIMO) array of “high-band” radiating elements that operate in, for example, some or all of the 1.7-2.7 GHz frequency band, the 3.4-3.8 GHz frequency band, or the 5.1-5.8 GHz frequency band. Massive MIMO arrays typically have at least four columns of radiating elements, and as many as thirty-two columns of radiating elements. In some embodiments, two or more base station antennas400ofFIG.4, base station antennas500ofFIG.5, and/or base station antennas600ofFIG.6may be vertically stacked to provide a MIMO array of a desired size.

FIG.10Bshows an elevation pattern1050for the base station antenna400ofFIG.4for one polarization at the same degree of electronic downtilt as the elevation pattern1000ofFIG.10A. It may also be seen that there is a more equal balance of RF energy between a right sidelobe1060and a left sidelobe1070and that the highest sidelobe level is lower than the highest sidelobe levels inFIG.10A.

While the discussion above focuses on radiating elements, it will be appreciated that the techniques discussed above can be used with radiating elements that operate in any appropriate frequency band.

It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (i.e., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.).

Aspects and elements of all of the embodiments disclosed above can be combined in any way and/or combination with aspects or elements of other embodiments to provide a plurality of additional embodiments.