Patent Application
20230170957
The present invention relates to cellular communications systems and, more particularly, to small cell base station antennas and related small cell base stations
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 “macrocell” base station. Each cell may, for example, have an area on the order of 1-50 km2, with the cell size depending upon, among other things, the terrain and population density. The base station may include baseband equipment, radios and base station antennas that are configured to provide two-way radio frequency (“RF”) communications with fixed and mobile subscribers (“users”) that are positioned throughout the cell. The base station antennas are often mounted on a tower or other raised structure, with the radiation beam (“antenna beam”) that is generated by each antenna directed outwardly to serve the entire cell or a portion (“sector”) thereof. 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 generally perpendicular relative to the plane defined by the horizon.
In order to increase capacity, cellular operators have been deploying so-called “small cell” base stations. A small cell base station refers to a lower power base station that may operate in the licensed and/or unlicensed spectrum that serves a much smaller area than a typical macrocell base station. Herein, the term “small cell” is used broadly to refer to base stations that serve smaller areas than conventional macrocell base stations, and thus the term “small cell” encompasses small cell, microcell, picocell and other base stations that serve small geographic regions. Small cell base stations may be used, for example, to provide cellular coverage to high traffic areas within a macrocell, which allows the macrocell base station to offload much or all of the traffic in the vicinity of the small cell to the small cell base station.
The small cell base station 10 further includes base station equipment such as one or more baseband units 40 and radios 42. The baseband unit 40 may receive data from another source such as, for example, a backhaul network (not shown) and may process this data and provide a data stream to the radio 42. The radio 42 may generate RF signals that include the data encoded therein and may amplify and deliver these RF signals to the antenna 20 for transmission via, for example, a cabling connection 44. While the radio 42 is shown as being co-located with the baseband equipment 40 at the bottom of the antenna tower 30, it will be appreciated that in other cases the radio 42 may be a remote radio head that is mounted on the antenna tower 30 adjacent the antenna 20. In some cases, the antenna may be a so-called “active antenna” that has the radio mounted directly on the antenna or implemented within the antenna. It will also be appreciated that the small cell base station 10 of
Beamforming antennas are antennas that have multiple columns of radiating elements that are fed by corresponding ports of a beamforming radio. The beamforming radio may form a plurality of RF signals that are based on a baseband data stream and pass each of these RF signals to a respective output port of the radio (“radio port”). Each radio port is coupled to a different column of radiating elements of the multi-column array of radiating elements. The amplitude and phase of each RF signal may be set by the beamforming radio so that the columns of radiating elements work together to form a more focused, higher gain antenna beam that has a narrowed beamwidth in the azimuth plane. If the radiating elements in each column of the antenna are dual-polarized radiating elements, then the number of RF ports on the beamforming radio may be doubled, and the antenna may be configured to form a separate antenna beam for each polarization. The antenna beams may be changed on a time slot-by-time slot basis in a time division duplex (“TDD”) transmission scheme in order to electronically “steer” the antenna beams in the azimuth plane to point at or near the users served during each time slot (the pointing direction of an antenna beam refers to the direction where the antenna beam has peak gain). In other cases the antenna may be arranged so that there are multiple input ports for sub-arrays in the elevation direction as well as azimuth direction so that the antenna beam may be electronically steered and narrowed in both the azimuth and elevation planes. Since beamforming antennas have the ability to narrow the azimuth (and perhaps elevation) beamwidth and to scan the antenna beams in the directions of specific users, they may exhibit higher antenna gains and support increased capacity.
As shown in
The base station antenna 100 may operate in an LTE-TM8 beamforming mode in conjunction with an off-the-shelf 4th Generation (4G) LTE-TDD eight-port beamforming radio 42. The radio 42 uses digital beamforming techniques to optimize the amplitude and phase weights that are applied to the signals received at each RF port 144 of the antenna 100. In particular, during a given time slot, an RF signal that is transmitted by the user assigned to the time slot is received at the antenna 100. This RF signal may be received at the radiating elements 122 of all four linear arrays 120-1 through 120-4. The magnitude and phase of the sub-components of the RF signal that are received at the radiating elements 122 of each linear array 120 will differ due to differences in transmission path lengths, fading, the azimuth pointing direction of each array and various other factors. Multiple versions of the transmitted RF signal may be received at one or more of the linear arrays 120 due to signal reflections off buildings, terrain features or the like that result in multipath transmission. The signals received at each of the eight linear arrays 120 are fed to the beamforming radio 42. The beamforming radio 42 uses an optimization algorithm to determine amplitude and phase weights to apply to the signals received at each linear array 120 that optimize a performance parameter (e.g., signal-to-noise ratio). The beamforming radio 42 applies the amplitude and phase weights determined by the optimization algorithm in demodulating the received RF signal. The beamforming radio 42 then determines the complex conjugates of the amplitude and phase weights that maximize the performance parameter for the received (uplink) signal and uses the complex conjugates as the amplitude and phase weights for transmitting RF signals through the linear arrays 120 on the downlink.
Pursuant to embodiments of the present invention, base station antennas are provided that include a tubular reflector that has at least first through fourth faces that face in different directions, first through fourth arrays of radiating elements that are mounted on the respective first through fourth faces of the tubular reflector, and a passive beamforming network that has first through fourth outputs that are coupled to the respective first through fourth arrays of radiating elements.
In some embodiments, the first face may be angled about 90° with respect to the second face.
In some embodiments, the tubular reflector may have a generally rectangular cross-section in a plane that is parallel to a plane defined by the horizon.
In some embodiments, the passive beamforming network may include a Butler Matrix.
In some embodiments, the base station antenna may be configured to provide omnidirectional coverage in the azimuth plane.
In some embodiments, the base station antenna may be provided in combination with a beamforming radio. The beamforming radio may include first through fourth first polarization ports that are coupled to respective first through fourth inputs of the passive beamforming network.
In some embodiments, the beamforming radio may be configured to operate using a time division duplex (“TDD”) communications scheme and may be configured to direct substantially all of the RF energy output by the first through fourth first polarization ports of the beamforming radio to a selected one of the arrays of radiating elements during selected time slots in a frame structure of the TDD communications scheme. In some embodiments, the beamforming radio may direct the RF energy output by the first through fourth first polarization ports to different ones of the first through fourth arrays of radiating elements during different time slots of the TDD communications scheme. In some embodiments, the beamforming radio may comprise an 8T/8R eight port beamforming radio.
In some embodiments, the first through fourth arrays of radiating elements may be respective first through fourth multi-column arrays of radiating elements, and the base station antenna may further include first through fourth power divider circuits that are each configured to split the RF energy output at a respective output of the passive beamforming network between the columns of the respective one of the first through fourth multi-column arrays of radiating elements that is coupled to the respective output of the beamforming network.
In some embodiments, an azimuth boresight pointing direction of the first array of radiating elements may be offset from the azimuth boresight pointing direction of the second through fourth arrays of radiating elements by about 90°, about 180° and about 270°, respectively.
In some embodiments, the first array of radiating elements may point in a first direction and the third array of radiating elements may point in a third direction that is substantially opposite the first direction. In some embodiments, the second array of radiating elements may point in a second direction and the fourth array of radiating elements may point in a fourth direction that is substantially opposite the second direction.
In some embodiments, the amplitude and phase weights of the beamforming radio may be set in a manner that will configure the first through fourth arrays of radiating elements to generate antenna beams having any of a sector antenna pattern, a heart-shaped antenna pattern, a bi-directional antenna pattern and an omni directional antenna pattern in the azimuth plane.
Pursuant to further embodiments of the present invention, base stations are provided that include a beamforming radio having a plurality of first polarization radio ports, a base station antenna that includes a plurality of arrays of radiating elements, and a passive beamforming network coupled between the first polarization radio ports and the arrays of radiating elements. The beamforming radio is configured to adjust the amplitude and/or phase of the RF signals output at each first polarization radio port in order to direct substantially all of the RF energy output through the first polarization radio ports to a selected one of the arrays of radiating elements.
In some embodiments, the base station antenna may further include a reflector assembly that includes a first face and a second face that is angled by about 90° with respect to the first face, and a first of the arrays of radiating elements may be mounted on the first face and a second of the arrays of radiating elements may be mounted on the second face.
In some embodiments, the passive beamforming network may include a plurality of four-port couplers.
In some embodiments, the beamforming radio may be an 8T/8R eight port beamforming radio.
In some embodiments, the beamforming radio may be configured to operate using a time division duplex (“TDD”) communications scheme and may be configured to direct substantially all of the RF energy output through the first polarization radio ports to different ones of the arrays of radiating elements during different time slots.
In some embodiments, the base station antenna may be configured to provide omnidirectional coverage in the azimuth plane.
Pursuant to still further embodiments of the present invention, methods of operating a cellular base station are provided. The base station includes a reflector assembly having arrays of radiating elements mounted to extend outwardly from respective faces of the reflector assembly that face in different directions. First RF signals are transmitted through a plurality of ports of a beamforming radio to a passive beamforming network during a first time slot, where the beamforming radio sets amplitudes and phases of the first RF signals so that substantially all of the RF energy is passed to a first of the arrays of radiating elements.
In some embodiments, the method further comprises transmitting second RF signals through the plurality of ports of the beamforming radio to the passive beamforming network during a second time slot, where the beamforming radio sets amplitudes and phases of the second RF signals so that substantially all of the RF energy is passed to a second of the arrays of radiating elements.
In some embodiments, the beamforming radio may be an 8T/8R eight port beamforming radio.
In some embodiments, the beamforming radio may be configured to set the amplitudes and phases of RF signals generated by the beamforming radio to one of four different settings.
In some embodiments, the reflector assembly may have a generally rectangular cross-section in a plane that is parallel to the plane defined by the horizon.
In some embodiments, the passive beamforming network may include a Butler Matrix.
In some embodiments, the reflector assembly may include first through fourth faces and the arrays of radiating elements may include first through fourth arrays of radiating elements that are mounted on the respective first through fourth faces.
In some embodiments, the first face may be angled from the second through fourth faces by about 90 degrees, about 180 degrees and about 270 degrees, respectively.
In some embodiments, the first through fourth arrays of radiating elements may be respective first through fourth multi-column arrays of radiating elements, the base station antenna further comprising first through fourth power divider circuits that are each configured to split the RF energy output at a respective output of the passive beamforming network between the columns of the respective one of the first through fourth multi-column arrays of radiating elements that is coupled to the respective output of the beamforming network.
Pursuant to further embodiments of the present invention, base stations are provided that include a beamforming radio having first through fourth first polarization radio ports, a base station antenna that includes first through fourth arrays of radiating elements, and a passive beamforming network that couples each of the first through fourth first polarization radio ports to all four of the first through fourth arrays of radiating elements.
In some embodiments of these base stations, the base station antenna may include a tubular reflector assembly that has first through fourth faces that are each angled by about 90° with respect to adjacent ones of the first through fourth faces. The first through fourth arrays of radiating elements may be mounted on the respective first through fourth faces.
In some embodiments, the passive beamforming network may include at least one four-port coupler. For example, in some embodiments, the passive beamforming network may include four four-port couplers per polarization.
In some embodiments, the amplitude and phase weights of the beamforming radio may be set in a manner that will configure the first through fourth arrays of radiating elements to generate antenna beams having any of a sector antenna pattern, a heart-shaped antenna pattern, a bi-directional antenna pattern and an omni directional antenna pattern in the azimuth plane.
In some embodiments, the beamforming radio may be an 8T/8R eight port beamforming radio.
When multiple instances of an element are present, the individual elements may be referred to in the drawings using two-part reference numerals (e.g., 220-2). Herein, the full reference numeral is used to refer to a specific element (e.g., linear array 220-2), while the first part of the reference numeral may be used to refer to all of the elements collectively (e.g., the linear arrays 220).
With the introduction of 5th generation (“5G”) cellular systems, beamforming antennas are now widely being deployed. Most of these antennas are so-called “panel” antennas that are designed to provide coverage throughout a 120° sector of a base station. These antennas typically include multiple linear arrays of radiating elements and one or more multi-column arrays of radiating elements, all of which are mounted on a planar reflector. The linear arrays of radiating elements may be designed to generate static antenna beams that cover the full 120° sector. In contrast, the multi-column arrays are designed to work with beamforming radios in order to generate more focused antenna beams that have higher antenna gain and that can be electronically steered to cover different portions of the 120° sector. For example, so-called 8T/8R beamforming radios have been developed that are routinely used with four column multi-column arrays. These 8T/8R radios have a total of eight radio ports, with four of the radio ports coupled to the −45° radiators of the radiating elements in the four columns (one radio port per column) of the multi-column array and the other four of the radio ports coupled to the +45° radiators of the radiating elements in the remaining four columns (one radio port per column) of the multi-column array. The radio and the four column array can simultaneously generate a pair of antenna beams, namely one at each polarization. The 8T/8R beamforming radio sets the amplitude and phase of the RF signals output through each radio port so that the generated antenna beams (1) have reduced beamwidths in the azimuth plane, and hence higher antenna gain and (2) are electronically steered in the azimuth plane to point in a desired direction. The 8T/8R beamforming radio may, for example, change the pointing direction of the generated antenna beams on a time slot-by-time slot basis of a TDD communication scheme.
While these 8T/8R 5G radios are well-suited for use with panel antennas that only cover, for example, a 120° sector of a cell, these radios are not well suited for use with antennas that provide omnidirectional (i.e., 360°) or quasi-omnidirectional coverage in the azimuth plane. Most small cell antennas, however, are designed to provide omnidirectional or quasi-omnidirectional coverage in the azimuth plane. Thus, 8T/8R 5G radios are not designed to be used in conjunction with most small cell antennas.
One option for providing beamforming small cell base stations is to use the beamforming antenna 100 discussed above with respect to
Pursuant to embodiments of the present invention, small cell beamforming base station antennas are provided that are suitable for use with 5G TDD radios that may use substantially all of the transmit power of the radio. These antennas may have passive beamforming networks that route the RF signals received from each radio port to a desired subset of the linear arrays included in the antenna. The small cell beamforming antennas according to embodiments of the present invention may have a very small form factor and may be mounted on light posts, electric power poles, telephones poles and the like. These small cell beamforming antennas may generate directional radiation patterns during any given time slot while providing full 360° coverage in the azimuth plane. The small cell antennas according to embodiments of the present invention may support higher EIRP levels than conventional small cell beamforming systems.
In some embodiments, the beamforming antennas according to embodiments of the present invention may include four linear arrays of radiating elements that are mounted on the four main faces of a tubular reflector assembly having a generally rectangular horizontal cross-section. The azimuth boresight pointing direction of each linear array (i.e., the direction where the antenna beams formed by the linear array achieve peak gain when no electronic steering is applied) may be offset from the azimuth boresight pointing direction of the remaining three linear arrays by about 90°, about 180° and about 270°, respectively. The radiating elements in each linear array may comprise dual-polarized radiating elements such as, for example, slant −45°/+45° cross-dipole radiating elements. The radiating elements may have directional patterns in the azimuth plane having, for example, azimuth half power beamwidths of between 50°-100°. Each of the four linear arrays may connect to two RF ports (one for each polarization) on the antenna, and the eight RF ports may connect to corresponding radio ports on an eight-port 5G 8T/8R beamforming radio. Each linear array may form a pair of directional antenna beams, one for each orthogonal polarization. Each antenna beam may, for example, provide coverage for about 90° in the azimuth plane.
In some embodiments, the small cell base station antenna may use passive beamforming networks such as a 4×4 Butler Matrix to combine the RF signals output through the four radio ports associated with one of the polarizations and to then output the combined signal through one of four output ports of the beamforming network to form a “sector” antenna beam that, for example, provides coverage to a 90° sector in the azimuth plane. The radio may set the amplitude and phase weights on the RF signals output from each radio port in one of four ways. Each of the four different weight settings act to direct all of the RF energy output at the four radio ports of the beamforming radio to a selected one of the four linear arrays. In other words, the 5G beamforming radio and the passive beamforming network may be configured to work together to feed the signals output by four radio ports to a selected one of the four linear arrays. This may be done for each of the two polarizations so that all of the RF energy output by the 5G radio during any given time slot may be radiated through a selected one of the four linear arrays. The radio may optionally be programmed to use two of the linear arrays during time slots serving users that are at the overlapping edges of the coverage areas of two adjacent arrays.
Moreover, by adjusting the weight settings, antenna beams having other shapes and/or pointing directions may be formed. For example, all of the RF energy output at the four radio ports of the beamforming radio may be directed to two adjacent ones of the linear arrays instead of to a single linear array. This technique may be used to change the boresight pointing direction of the sector antenna beam so that the peak gain of the sector antenna beam may be pointed at any angle in the azimuth plane. The beamforming antennas according to embodiments of the present invention may also be configured to form antenna beams having other shapes simply be changing the weight settings. For example, the above-described antennas may be configured to form antenna beams having omnidirectional, heart-shaped and/or bi-directional patterns in the azimuth plane simply by applying the appropriate weight settings in the beamforming radio. Thus, a single beamforming antenna, in conjunction with an off-the-shelf 5G beamforming radio, may form any of the standard antenna patterns that are typically desired by cellular operators.
Butler Matrix based beamforming networks are conventionally used to couple multiple radio ports to a multi-column planar array of radiating elements. For example, the Butler Matrix may be used to allow two radio ports to share a multi-column array of radiating elements so that each radio port is coupled to all of the radiating elements in the array. The Butler Matrix is typically configured to couple the two radio ports to the multi-column array in such a way that the RF signal from the first radio port generates a first antenna beam that points in a first direction in the azimuth plane and the RF signal from the second radio port generates a second antenna beam that points in a second, different, direction in the azimuth plane. Such antennas are typically used in sector splitting applications where the first antenna beam covers a first portion of a sector of a base station (e.g., the left side of a 120° sector) and the second antenna beam covers a second portion of the sector (e.g., the right side of the 120° sector). Embodiments of the present invention use Butler Matrix style beamforming networks in a completely different way; the Butler Matrix acts as a power combiner and as a switch that allows all of the output power of the radio to be delivered to a selected one of the linear arrays of the antenna.
According to further embodiments of the present invention, the base station antenna may include switching networks that accomplish the same result. For example, base station antennas are provided that include four linear arrays of radiating elements that are mounted on the four main faces of a tubular reflector assembly having a generally square horizontal cross-section. These antennas further include, for each polarization, a 4×1 combiner and a 1×4 switch. Each 4×1 combiner is coupled to the four radio ports of the 5G beamforming radio that are associated with one of the two supported polarizations. The output of each 4×1 combiner is coupled to a respective one of the 1×4 switches, and the outputs of each 1×4 switch are coupled to the respective linear arrays. Each 1×4 switch may be set to route RF signals received at the input thereof to a selected one of the four linear arrays on a time slot-by-time slot basis in order to combine the RF signals output through four of the radio ports and output the combined signal through the selected one of the linear arrays.
In some applications the antennas according to embodiments of the present invention that include Butler Matrix-style feed networks may be preferred over antennas that use RF switches in the feed network, as the Butler Matrix-style approach may have superior power handling capabilities and better passive intermodulation distortion performance.
Embodiments of the present invention will now be discussed in further detail with reference to
A plurality of RF ports 244 are mounted in a bottom end cap 240 of base station antenna 200. A total of eight RF ports 244-1 through 244-8 may be provided, with two RF ports 244 coupled to each linear array 220. The first RF port 244 coupled to each linear array 220 may support communications at the first polarization and the second RF port 244 coupled to each linear array 220 may support communications at the second polarization.
Each linear array 220 may be oriented generally vertically with respect to the horizon when the base station antenna 200 is mounted for use so that each linear array 220 comprises a column of radiating elements 222. In the depicted embodiment, each linear array 220 includes a total of five radiating elements 222. It will be appreciated, however, that other numbers of radiating elements 222 may be included in the linear arrays 220. In the depicted embodiment, each linear array 220 is implemented as three sub-arrays of radiating elements 222, where the top and bottom sub-arrays include two radiating elements 222 that are mounted on a common feedboard 228, while the middle sub-array includes a single radiating element 222 that is mounted on its own feedboard 228. It will be appreciated that any appropriate number of radiating elements 222 may be included in each sub-array, and that feedboards 228 may or may not be used. It will also be appreciated that different types of radiating elements 222 may be used than those depicted in
Each radiating element 222 may be implemented, for example, using the radiating element design shown in
As discussed above, the small cell base station antennas according to embodiments of the present invention may use beamforming networks such as, for example, Butler Matrices, to combine the RF signals output by the beamforming radio and to route the combined RF signal to a selected one of the linear arrays of the antenna. In this manner, the full transmit power of the radio may be utilized and the RF signal may be directed to a selected linear array.
As shown in
As shown in
The RF signals output from the first output port 264-1 of the third hybrid coupler 260-3 are coupled to the −45° dipole radiators 226 of the radiating elements 222 of the first linear array 220-1. The RF signals output from the second output port 264-2 of the third hybrid coupler 260-3 are coupled to the −45° dipole radiators 226 of the radiating elements 222 of the third linear array 220-3. The RF signals output from the first output port 264-1 of the fourth hybrid coupler 260-4 are coupled to the −45° dipole radiators 226 of the radiating elements 222 of the second linear array 220-2. The RF signals output from the second output port 264-2 of the fourth hybrid coupler 260-4 are coupled to the −45° dipole radiators 226 of the radiating elements 222 of the fourth linear array 220-4.
As a result of the above connections, assuming that a signal “A” is output from radio port 44-1, a signal “B” is output from radio port 44-2, a signal “C” is output from radio port 44-3, and a signal “D” is output from radio port 44-4, the phases of the sub-components of signals A-D that are received at linear arrays 220-1 through 220-4 are as follows:
TABLE 1 below shows the amplitude and phases of the RF signals input to feed network 250 (i.e., the amplitude and phase settings applied in the beamforming radio 42) that will result in all of the RF energy being directed to a single linear array 220. Herein, the antenna beams corresponding to the four rows of TABLE 1 in which all of the RF energy is output through a single linear array 220 are referred to as “compass beams.”
Focusing on, for example, the first row of TABLE 1, it can be seen that when radio ports 44-1 through 44-4 are fed signals having magnitude/phases of 0.5/−45°, 0.5/−135°, 0.5/−90°, 0.5/−180°, respectively, then the RF power at each linear array 220 is as follows:
In other words, by programming the 8T/8R beamforming radio 42 to apply appropriate amplitudes and phases to the RF signals output on the four ports for the first polarization, the small cell base station antenna 200 may be configured to output all of the RF energy to linear array 220-1. The same technique may be applied to direct all of the RF energy to the second linear array 220-2, the third linear array 220-3 or the fourth linear array 220-4 by simply using opposite signs on the phases for the signals output at each radio port 44.
TABLE 1 thus shows that by using the beamforming radio 42 to appropriately amplitude and phase weight the RF signals provided to radio ports 44-1 through 44-4, all of the RF energy transmitted through those radio ports 44 may be directed to a selected one of the four linear arrays 220. Thus, by using the passive beamforming network 250, the full capabilities of the 8T/8R beamforming radio 42 may be utilized (and, in particular, the full RF power of each transmit/receive chain) and the RF energy may be transmitted through a selected one of the linear arrays 220 to provide a directional, high gain antenna beam.
The 3GPP standard specifies a standard set of weights that are included in all fifth generation (5G) radios. These weight sets are referred to as “codebooks.” The use of standardized weight sets facilitates interoperability between equipment manufactured by different vendors. TABLE 2 below shows the weights or “codebooks” specified by the 3GPP standard for 8T8R 5G radios.
In TABLE 2 above, P1, P2, P3 and P4 refer to the first through fourth ports of the 8T8R radio. The values in the columns labelled P1-P4 of TABLE 2 indicate the relative phases of the RF signals output through the respective first through fourth ports of the 8T8R radio for each “codebook.” The first through fourth ports are the four first polarization ports of the 8T8R radio (i.e., the ports that are coupled to the first polarization radiators of respective first through fourth arrays of radiating elements of the base station antenna). It will be appreciated that fifth through eighth ports of the 8T8R radio, which are coupled to the second polarization radiators of the respective first through fourth arrays of radiating elements of the base station antenna, use the exact same codebooks (i.e., ports P1-P4 in TABLE 2 are simply replaced with ports P5-P8, respectively). It should also be noted that different manufacturers label the ports on the radio differently. Assume that the four columns of radiating elements on a four-column beamforming antenna are identified as the left (L) column, the left center (LC) column, the right center (RC) column and the right (R) column. In one common radio port configuration, which is referred to as the co-pol configuration, then the ports P1-P8 on the radio would be connected to the four columns as follows (where the “+” and “−” below indicate the polarization):
In another common radio port configuration, which is referred to as the cross-pol configuration, then the ports P1-P8 on the radio would be connected to the four columns as follows:
Referring to
Similarly, it can also be seen by comparing TABLES 1 and 2 that if the 5G radio 42 is set to Codebook 24, then the beamforming network 250 will direct all of the RF energy to linear array 220-3. This result occurs because the phases of radio ports 44-1, 44-3, 44-2, 44-4 (corresponding to ports P1, P2, P3, P4, respectively) shown in the third row of TABLE 1 increase by 135° port-to-port (i.e., the phase at each port 44-1, 44-3, 44-2, 44-4 is offset by 135° from the prior port), and the phases of the RF signals output at ports P1, P2, P3, P4 of Codebook 24 show the same 135° phase progression. If the 5G radio 42 is set to Codebook 40, then the beamforming network 250 will direct all of the RF energy to linear array 220-4. This result occurs because the phases of radio ports 44-1, 44-3, 44-2, 44-4 (corresponding to ports P1, P2, P3, P4, respectively) shown in the second row of TABLE 1 increase by 225° port-to-port (i.e., the phase at each port 44-1, 44-3, 44-2, 44-4 is offset by 225° from the prior port), and the phases of the RF signals output at ports P1, P2, P3, P4 of Codebook 40 show the same 225° phase progression. Finally, if the 5G radio 42 is set to Codebook 56, then the beamforming network 250 will direct all of the RF energy to linear array 220-1. This result occurs because the phases of radio ports 44-1, 44-3, 44-2, 44-4 (corresponding to ports P1, P2, P3, P4, respectively) shown in the first row of TABLE 1 increase by 315° port-to-port (i.e., the phase at each port 44-1, 44-3, 44-2, 44-4 is offset by 315° from the prior port), and the phases of the RF signals output at ports P1, P2, P3, P4 of Codebook 24 show the same 315° phase progression.
Thus, as shown above, by coupling ports P1, P2, P3, P4 of an 8T8R 5G radio to the ports of beamforming network 250 labelled A, C, B, D in
As the above discussion makes clear, pursuant to embodiments of the present invention, base stations are provided that include a base station antenna 200 that includes first through fourth arrays 220-1 through 220-4 of dual-polarized radiating elements 222. The base station antenna 200 may include a tubular reflector 210 that has at least first through fourth faces 212-1 through 212-4 that face in different directions, and the first through fourth arrays 220-1 through 220-4 are mounted on the respective first through fourth faces 212-1 through 212-4 of the tubular reflector 210, where the first face 212-1 is angled about 90° with respect to the second face 212-2. In some embodiments, an azimuth boresight pointing direction of the first array 220-1 is offset from the azimuth boresight pointing direction of the second through fourth arrays 220-2 through 220-4 by about 90°, about 180° and about 270°, respectively.
The base station further includes a beamforming radio 42 having first through fourth radio ports 44-1 through 44-4 that are coupled to first polarization radiators of the radiating elements 222 of the respective first through fourth arrays 220-1 through 220-4 and fifth through eighth radio ports that are coupled to second polarization radiators of the radiating elements 222 of the respective first through fourth arrays 220-1 through 220-4. Moreover, the base station antenna 200 is configured so that when the beamforming radio 42 outputs RF signals that have equal magnitudes and a phase progression of 45° through the respective first through fourth radio ports 44-1 through 44-4, substantially all of the RF energy output through the first through fourth radio ports 44-1 through 44-4 is directed to the first polarization radiators of the radiating elements 222 of the second array 220-2. The base station antenna 200 may also be configured so that when the beamforming radio 42 outputs RF signals that have equal magnitudes and a phase progression of 135° through the respective first through fourth radio ports 44-1 through 44-4, substantially all of the RF energy output through the first through fourth radio ports 44-1 through 44-4 is directed to the first polarization radiators of the radiating elements 222 of the third array 220-3, so that when the beamforming radio 42 outputs RF signals that have equal magnitudes and a phase progression of 225° through the respective first through fourth radio ports 44-1 through 44-4, substantially all of the RF energy output through the first through fourth radio ports 44-1 through 44-4 is directed to the first polarization radiators of the radiating elements 222 of the fourth array 220-4, and so that when the beamforming radio 42 outputs RF signals that have equal magnitudes and a phase progression of 315° through the respective first through fourth radio ports 44-1 through 44-4, substantially all of the RF energy output through the first through fourth radio ports 44-1 through 44-4 is directed to the first polarization radiators of the radiating elements 222 of the first array 220-1.
While not shown in
As shown above, the base station antenna 200 may have a four-beam beam set, and the radio 42 may be programmed to select one of the four antenna beams for each time slot based on one or more channel quality indicators for the user(s) served during the time slot. Since the base station antenna 200 has dual-polarized radiating elements 222, the selected linear array 220 generates two antenna beams during each time slot, allowing the small cell base station antenna 200 to operate as a 2T/2R (2xMIMO) beamforming antenna.
It will be appreciated that
In many cases, it may be desirable to have the ability to electronically downtilt the antenna beams generated by a base station antenna.
As shown in
The feed network 250A further includes four power splitter/phase shifter assemblies 280-1 through 280-4. Each phase shifter 280 may be configured to split the RF signals input thereto three ways (and the power split may be equal or unequal) and to apply a phase progression across the three sub-components of the split RF signal to apply an electronic downtilt to the antenna beam that is formed when the sub-components of the RF signal are transmitted (or received) through the linear array 220 that is connected to the outputs of the power splitter/phase shifter assembly 280. As described above with reference to
It will be appreciated that
The base station antenna 200 thus comprises a tubular reflector 210 that has at least first through fourth faces 212-1 through 212-4 that each face in different directions. The antenna 200 further includes first through fourth arrays 220-1 through 220-4 of radiating elements 222 that are mounted on the respective first through fourth faces 212-1 through 212-4 of the tubular reflector 210. The antenna 200 also includes a passive beamforming network 260-1 through 260-4, 270-1, 270-2 that has first through fourth outputs that are coupled to the respective first through fourth arrays of radiating elements 220-1 through 220-4.
The base station antenna 200 may be relatively small, having a diameter on the order of 8 inches and a height of about two feet for an antenna operating in the 2 GHz frequency range. Such an antenna may be readily mounted on most utility poles and streetlights, and given its small diameter, the antenna 200 may blend together with the pole so that it is not a visual blight. Moreover, in urban environments, there are typically a small number of entities that own the utility poles such as an electric power company, a government entity (e.g., for streetlights), and a landline telephone company. As such, deploying small cell base station antenna that are utility pole mountable—such as the base station antenna 200—may be advantageous since a cellular operator can reach a leasing agreement with one or two entities to obtain locations for mounting small cell base station antennas throughout the urban area.
The base station antenna 300 may be suitable for providing coverage over a 180° area in the azimuth plane. The base station antenna 300 may, for example, be mounted on an exterior wall of a building. In other embodiments, the tubular reflector assembly 310 having a semi-octagonal horizontal cross-section of
While base station antenna 200 (
The base station 600 may operate as follows. The beamforming radio 42 may output the same RF signal at each first polarization radio port 44. These RF signals are then combined by the 4×1 combiner 660 into a composite RF signal. The composite RF signal output by the combiner 660 is fed to the 1×4 switch 670 that passes the composite RF signal to the first polarization radiators of a selected one of the four linear arrays 220. The 1×4 switch 670 may select one of the four arrays 220 for each time slot in a TDD communications scheme based on a determination as to which array 220 will support communications having the highest channel quality indicator (which may be determined based on feedback from the user device(s) that are served during each time slot). Thus, the base station antenna 600 may operate in the same manner as the base station antenna 200 described above, but uses a combiner 660 and a switch 670 to select the linear array 220 that is fed during a particular time slot rather than a passive beamforming network as is the case with base station antenna 200. It should be noted that while not shown in
In some embodiments, the TDD beamforming radio may split the energy between different layers of a multi-input-multi-output (“MIMO”) transmission scheme, serving multiple user devices at the same time with different antenna beams. For example, the radio may support 4xMIMO communications by forming two different antenna beams (at each polarization) using different amplitude/phase weights at the RF level.
It will also be appreciated that the small cell base stations according to embodiments of the present invention, such as the small cell base station of
Moreover, by adjusting the weight settings that are applied in the 8T/8R radio 42, the pointing direction of the sector antenna beam may be adjusted. For example, all of the RF energy output at the four radio ports 44-1 through 44-4 of the beamforming radio 42 may be directed to two adjacent ones of the linear arrays 220 of base station antenna 200 instead of to a single linear array 220. This technique may be used to change the boresight pointing direction of the sector antenna beam so that the peak gain of the sector antenna beam may be pointed at any angle in the azimuth plane.
Additionally, in some situations, a cellular operator may want to generate antenna beams having shapes other than a “sector” shape. For example, in order to transmit control signals to all users within a coverage area of the base station antenna, the cellular operator may want to generate an antenna beam that has omnidirectional coverage in the azimuth plane. By amplitude and phase weighting the RF signals output at radio ports 44-1 through 44-4 in the manner shown in TABLE 3 below, an antenna beam having generally omnidirectional coverage in the azimuth plane may be generated.
None of the Codebook weights listed in TABLE 2 above have the phase progression shown in TABLE 3. However, most 5G radios allow definition of a broadcast beam, and thus the 5G radio can typically be programmed to have the phase progression shown in TABLE 3 as an option, allowing formation of an omnidirectional antenna beam. Additionally, 5G radios may be programmed to generate an “envelope” antenna beam, which is comprised of a set of traffic beams. Thus, an envelope beam may be generated based on a combination of Codebooks 8, 24, 40 and 56 to generate an omnidirectional beam.
Cellular operators are also sometimes interested in deploying base station antennas that generate so-called “heart-shaped” antenna beams that provide coverage over approximately 180° in the azimuth plane. The base station antennas according to embodiments of the present invention can also readily form such heart-shaped antenna beams by, for example, amplitude and phase weighting the RF signals output at radio ports 44-1 through 44-4 in the manner shown in TABLE 4 below.
The amplitude and phase weights shown in TABLE 4 will send all of the RF energy to first and second adjacent ones of the linear arrays 220 in order to form an antenna beam having a heart-shape in the azimuth plane. It will also be appreciated that the amplitude and phase weights may be adjusted from what is shown in TABLE 4 to select which pair of adjacent linear arrays 220 are excited to form the heart-shaped antenna beam, so that the pointing direction of the peak of the heart shaped antenna beam may be rotated to point in different directions. Moreover, the pointing direction of the heart-shaped antenna beam may also be adjusted to point in any direction in the azimuth plane by directing the RF energy to three of the linear arrays 220 with appropriate amplitude and phase weights applied by the beamforming radio 42. Setting the 5G radio to codebook 0 with the radio port to beamforming port connections described above will generate the heart-shaped antenna beam.
Cellular operators are also sometimes interested in deploying base station antennas that generate so-called “bi-directional” antenna beams that provide coverage in two opposed directions in the azimuth plane. Antenna beams having a bi-directional shape in the azimuth plane may be useful, for example, in providing coverage to long fairly straight sections of highways and/or along bridges, tunnels and the like. The base station antennas according to embodiments of the present invention can also readily form such “bi-directional” antenna beams by, for example, amplitude and phase weighting the RF signals output at radio ports 44-1 through 44-4 in the manner shown in TABLE 5 below.
The amplitude and phase weights shown in TABLE 5 will send all of the RF energy to first and second opposed ones of the linear arrays 220 in order to form an antenna beam having a bi-directional shape in the azimuth plane. It will also be appreciated that the amplitude and phase weights may be adjusted from what is shown in TABLE 5 to select which pair of opposed linear arrays 220 are excited to form the bi-directional antenna beam, so that the pointing direction of the peak of the bi-directional antenna beam may be rotated to point in one of two different directions. Most 5G radios also allow an operator to declare a traffic beam with a unique weight set which could be used to generate the bi-directional antenna beam.
Moreover, the amplitude and phase weights may be further adjusted so that the pointing direction of the peak of the various antenna beams that are discussed above that provide less than omnidirectional coverage in the azimuth plane (i.e., the 90° sector beams, the heart-shaped 180° sector beams and the bi-directional antenna beams) may point in any direction in the azimuth plane.
As illustrated above, the small cell beamforming base station antennas according to embodiments of the present invention can generate all of the standard antenna beams (omnidirectional, sector, heart-shaped, bi-directional) that cellular operators request for small cell antennas in a single antenna, and may do so while using the full transmit power of the cellular radio. Using conventional techniques, such a capability may only be obtained by providing four different small cell antenna designs—where each design is configured to form a specific one of the antenna beams. In short, by using a standard, off-the-shelf 8T/8R beamforming radio a cellular operator may now use the same antenna to generate any of the standard antenna beams.
It will be appreciated that many modifications may be made to the antennas described above without departing from the scope of the present invention. For example, the base station antenna 200 includes four linear arrays 220 that are mounted on the four sides of a support structure that has a square horizontal cross-section. In other embodiments, a base station antenna may be provided that is identical to the base station antenna 200 except that it includes five linear arrays that are mounted on a support structure having a pentagon-shaped horizontal cross-section. Such a base station antenna may be used with a 10T/10R 5G beamforming radio. In still other embodiments, a base station antenna may be provided that is identical to the base station antenna 200 except that it includes six linear arrays that are mounted on a support structure having a hexagonal horizontal cross-section. Such a base station antenna may be used with a 12T/12R 5G beamforming radio. As another example, small cell base station antennas may be provide that have a tubular reflector assembly that has a substantially octagonal horizontal cross-section, with a linear array mounted on each of the eight faces of the tubular reflector assembly. Such a base station antenna may be used in conjunction with two 8T/8R beamforming radios to effectively implement an antenna that is equivalent to two of base station antenna 200 in a single housing. Assuming the eight faces of the tubular reflector assembly are numbered as faces 1-8 in order, then the linear arrays on faces 1, 3, 5 and 7 may be used with the first beamforming radio and the linear arrays on faces 2, 4, 6 and 8 may be used with the second beamforming radio. Such an approach may be used to implement higher order MIMO communications or to provide service in two different frequency bands.
The present invention provides small cell base station antennas that can be used with 8T/8R (or other) 5G radios while harnessing all of the output power of the radio. This may be important as 8T/8R radios may be the only 5G radios that are available for use in certain of the 5G frequency bands such as the C-band (3.7-3.98 GHz). Such 8T/8R radios are not well-suited for use with conventional small cell antennas. The present invention provides base station antennas that take advantage of the beamforming capabilities of the 8T/8R radios to generate higher gain antenna beams while simultaneously using the full transmit power of all eight channels of the radio for each user.
The present invention has been described above with reference to the accompanying drawings. 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 elements may not be to scale.
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.
It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention.
The present application claims priority as a continuation-in-part of U.S. patent application Ser. No. 17/761,731, filed Mar. 18, 2022, which is a 35 U.S.C. § 371 national stage application of PCT Application No. PCT/CN2021/119258, filed on Sep. 18, 2021, which in turn claims priority to U.S. Provisional patent application Ser. No. 63/171,267, filed Apr. 6, 2021, the entire content of each of which is incorporated herein by reference as if set forth fully herein.
| Number | Date | Country | |
|---|---|---|---|
| 63171267 | Apr 2021 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 17761731 | Jan 0001 | US |
| Child | 17901991 | US |
