CN110416706B - Calibration circuit for beam forming antennas and associated base station antennas - Google Patents

Abstract

The present disclosure relates to calibration circuits for beamforming antennas and related base station antennas. The base station antenna includes a back plate and a plurality of radiating elements extending forward from the back plate. The antenna further includes a plurality of feed plates, and each of the feed plates has a respective set of one or more radiating elements mounted thereon. The antenna also includes a calibration port and a calibration circuit having a calibration combiner with an output coupled to the calibration port and a plurality of directional couplers coupled to the calibration combiner. At least a first portion of the first directional couplers is implemented on a first one of the feed plates.

Description

Calibration circuit for beam forming antennas and associated base station antennas

Technical Field

The present invention relates to cellular communication systems, and more particularly to cellular communication systems employing beamforming antennas.

Background

Cellular communication systems are used to provide wireless communication to both fixed and mobile subscribers (herein "users"). In a typical cellular communication system, a geographic area is divided into a series of regions called "cells" and each cell is served by a base station. Each base station may include a baseband device, a radio, and a base station antenna configured to provide two-way radio frequency ("RF") communication with users within the cell. The base station antennas are typically mounted on towers or other protruding structures.

A base station antenna is a directional device that can concentrate RF energy transmitted or received in a particular direction. The "gain" of a base station antenna in a given direction is a measure of the ability of the antenna to concentrate RF energy in that direction. The radiation pattern (also referred to as an "antenna beam") generated by a base station antenna is a collection of the gains of the antenna in all different directions. The radiation pattern of a base station antenna is typically designed to serve a predefined coverage area, such as a cell or a portion of a cell (commonly referred to as a "sector"). Base station antennas are typically designed to have a minimum gain level in their predefined coverage area and a much lower gain level outside the coverage area to reduce interference to neighboring cells or sectors. Typically, a base station antenna comprises one or more phased arrays of radiating elements, which are arranged in one or more vertical columns when the antenna is installed for use, wherein "vertical" refers to a direction generally perpendicular with respect to a plane defined by a horizontal plane.

Fig. 1 is a schematic diagram of a conventional cellular base station 10. The base station 10 comprises several base station antennas 20 mounted on a protruding structure 30, such as an antenna tower. The baseband apparatus 40 may be mounted at the base of the tower 30 and the cable connection 42 may connect the baseband apparatus 40 to a remote radio head (not visible in fig. 1) mounted behind each base station antenna 20. Each base station antenna 20 may generate an antenna beam 50 (shown schematically in fig. 1), the antenna beam 50 serving 120 ° sectors in a horizontal or "azimuth" plane. For example, each base station antenna 20 may be designed to have a half power beamwidth of approximately 65 ° which provides good coverage throughout a 120 ° sector.

Early base station antennas typically had a fixed radiation pattern, meaning that once the base station antenna was installed, the radiation pattern of the base station antenna could not be changed unless the technician physically reconfigured the antenna. Today, the radiation pattern on many base station antennas can be electronically changed from a remote location by sending control signals to the antennas, wherein the control signals alter the amplitude and/or phase of RF energy sent/received by each radiating element of the array that changes the shape of the radiation pattern. The most common changes in radiation pattern are changes in elevation (elevation) or "downtilt" angle (i.e., angle relative to the horizontal plane to which the portion of the antenna beam with the highest gain is directed) and/or azimuth angle (angle in the horizontal plane to which the portion of the antenna beam with the highest gain is directed). Base station antennas that can have their downtilt and/or azimuth electronically changed from a remote location are commonly referred to as remote electronic tilt ("RET") antennas.

To increase capacity, some cellular base stations now employ beamforming radios and multi-column beamforming antennas. In some beamforming antennas, each column of radiating elements is coupled to a respective RF port of the radio. The radio may adjust the amplitude and phase of the subcomponents of the RF signal delivered to each RF port such that the columns of radiating elements work together to form a more focused, higher gain antenna beam having a narrower beamwidth in the azimuth and/or elevation planes. In some cases, these beamforming antennas may be used to form two or more static antenna beams, where each antenna beam has a smaller beamwidth in the azimuth plane. This approach may be used to perform so-called "sector splitting", where a 120 ° sector may be split into two, three or even more smaller sub-sectors, and the beamforming antenna may be configured to generate a separate antenna beam for each sub-sector. Beamforming antennas capable of forming narrow antenna beams, sometimes referred to as "pencil (pencil) beams", which may be directed to a particular user or a densely aggregated group of users, may also be used. These antennas may generate different pencil beams on a slot-by-slot basis such that very high gain antenna beams may be electronically steered over the entire sector during the different slots to provide coverage for users of the entire sector.

Unfortunately, the relative amplitude and phase imposed by the radio on the subcomponents of the RF signal delivered to each column-beamformed antenna cannot be maintained because the subcomponents of the RF signal are delivered from the radio to the high power amplifier and then on to the base station antenna. If the relative amplitude and phase changes, the resulting antenna beam will typically exhibit lower antenna gain in the desired direction and higher antenna gain in the undesired direction, resulting in performance degradation. For example, changes in relative amplitude and phase may occur due to non-linearities in the amplifiers used to amplify the respective transmit and receive signals, differences in length of cable connections between the different radio ports and the respective RF ports on the antenna, temperature changes, and the like. While some of the reasons for amplitude and phase variations may tend to be static (i.e., they do not change over time), others may be dynamic and thus more difficult to compensate.

To reduce the effects of the amplitude and phase variations described above, the beamforming antenna may include calibration circuitry that samples each sub-component of the RF signal and passes the samples back to the radio. The calibration circuit may include a plurality of directional couplers, each configured to tap (tap) RF energy from a respective one of the RF transmission paths extending between the RF port and the radiating elements of the respective column, and a calibration combiner for combining the RF energy tapped from each of the RF transmission paths. The output of the calibration combiner is coupled to a calibration port on the antenna and in turn coupled back to the radio. The radio may use the samples of each sub-component of the RF signal to determine relative amplitude and/or phase changes along each transmission path, and may then adjust the applied amplitude and phase weights to account for these changes.

Disclosure of Invention

According to some embodiments of the present invention, there is provided a base station antenna comprising a back plate and a plurality of radiating elements extending forward from the back plate. The antenna further includes a plurality of feed plates, and each of the feed plates has a respective set of one or more radiating elements mounted thereon. The antenna also includes a calibration port and a calibration circuit having a calibration combiner with an output coupled to the calibration port and a plurality of directional couplers coupled to the calibration combiner. At least a first portion of the first directional couplers is implemented on a first one of the feed plates.

According to other embodiments of the present invention, a base station antenna is provided that includes a back plate, a first plurality of radiating elements arranged to define a first column of radiating elements, and a second plurality of radiating elements arranged to define a second column of radiating elements. The antennas also include a first electromechanical phase shifter electrically coupled between the first RF port of the antenna and the first column of radiating elements, and a second electromechanical phase shifter electrically coupled between the second RF port of the antenna and the second column of radiating elements. The antennas also include a calibration circuit including a first directional coupler coupled along a first RF transmission path extending between an input of the first electromechanical phase shifter and a first one of the radiating elements in the first column of radiating elements, and a second directional coupler coupled along a second RF transmission path extending between an input of the second electromechanical phase shifter and the first one of the radiating elements in the second column of radiating elements.

According to a further embodiment of the present invention, there is provided a base station antenna including a back plate having a front surface and a back surface, and a plurality of radiating elements extending forward from the back plate. The antennas also include a plurality of feed plates mounted in front of the back plate, wherein each feed plate has a respective set of one or more of the plurality of radiating elements mounted on the feed plate. The antenna also includes a calibration circuit including a plurality of components mounted in front of the back plate and at least one additional component mounted behind the back plate.

According to a further embodiment of the present invention, there is provided a base station antenna comprising a back plane, a plurality of RF ports including at least a first RF port and a second RF port, a plurality of radiating elements including at least a first radiating element and a second radiating element, a plurality of power splitters including at least a first power splitter and a second power splitter, a calibration port, and a calibration circuit, each radiating element extending forward from the back plane, the first power splitter coupled between the first RF port and the first radiating element, and the second power splitter coupled between the second RF port and the second radiating element. The calibration circuit includes a calibration combiner having an output coupled to the calibration port and a plurality of directional couplers including at least a first directional coupler and a second directional coupler coupled to the calibration combiner. The first directional coupler is implemented on a printed circuit board of the first power splitter.

Drawings

Fig. 1 is a schematic diagram illustrating a conventional cellular base station having three base station antennas for providing coverage to three sectors in an azimuth plane.

Fig. 2 is a schematic perspective view of a beamforming antenna with a radome (radome) removed, in accordance with an embodiment of the present invention.

Fig. 3 is a schematic block diagram illustrating a base station antenna with conventional calibration circuitry.

Fig. 4 is a schematic block diagram illustrating a base station antenna implementing calibration circuitry on a feed board of the antenna according to an embodiment of the invention.

Fig. 5 is a schematic block diagram illustrating a base station antenna according to other embodiments of the present invention.

Fig. 6 is a schematic block diagram illustrating a base station antenna according to other embodiments of the present invention.

Fig. 7 is a schematic plan view illustrating how a directional coupler included in the base station antenna of fig. 6 may be formed by electromagnetically coupling an RF transmission line on a feed board to a conductive structure on an underlying calibration circuit board through an opening in the back plate of the antenna.

Fig. 8 is a schematic front view of a calibration circuit board included in the base station antenna of fig. 6, illustrating a calibration combiner circuit implemented on the calibration circuit board.

Fig. 9 is a schematic cross-sectional view illustrating another implementation of a directional coupler included in the base station antenna of fig. 6.

Fig. 10 is a schematic block diagram illustrating a base station antenna according to a further embodiment of the present invention.

Fig. 11 is a front perspective view of a phase shifter assembly that may be included in the base station antenna of fig. 10.

Fig. 12 is a schematic block diagram of a modified version of the phase shifter assembly of fig. 11 that may be used in the base station antenna of fig. 10.

Fig. 13 is a schematic block diagram illustrating a modified version of the base station antenna including the calibration circuitry included in the base station antennas of fig. 6-8.

Fig. 14 is a schematic exploded perspective view of a portion of the base station antenna of fig. 13.

Fig. 15 is a schematic plan view of a calibration combiner circuit illustrating how a calibration coupler is implemented on and electromagnetically coupled to a phase shifter printed circuit board.

Detailed Description

According to an embodiment of the present invention, a beamforming base station antenna with improved calibration circuitry is provided. The calibration circuit may include a plurality of directional couplers and a calibration combiner that combines the outputs of the directional couplers. The calibration circuit can be implemented in a new manner and at a new location within the antenna, which can provide improved performance and/or reduce the cost of the antenna.

Conventionally, a calibration circuit for a beamforming antenna is located directly above a substrate (base plate) of the antenna, and an input cable is provided that directly connects each RF port on the antenna to the calibration circuit board on which the calibration circuit is implemented. A base station antenna with such a design may exhibit a high tolerance (tolerance) level for the calibration circuit because the only change in amplitude or phase within the antenna that will be generated along the calibration path is a change that may be introduced in the input cable and/or the calibration circuit. A beam forming base station antenna according to embodiments of the present invention may have calibration circuitry located at least partially on the phase shifter printed circuit board, on the feed board supporting the individual radiating elements, on the power splitter printed circuit board, and/or on the diplexer printed circuit board. This new approach allows the calibration circuit to identify relative amplitude and/or phase variations that may be introduced within many antenna feed networks, which allows the radio to correct for such variations and provide improved antenna patterns. Further, moving the calibration circuit onto the phase shifter printed circuit board, the feed board, the power splitter printed circuit board, and/or the diplexer printed circuit board may move the calibration circuit farther away from the RET actuator (typically at the base of the antenna adjacent to the antenna port), which may reduce the likelihood of the dc motor included in the RET actuator introducing noise in the calibration circuit. Furthermore, repositioning the calibration circuitry may also reduce the number of elements/circuits located near the base of the antenna, which may allow for a reduction in the overall length of many antenna designs. Repositioning the calibration circuitry may also reduce the number of cables (and associated pads) required in the antenna, which may both reduce cost and improve antenna performance. In addition, even with very short microstrip transmission lines on the calibration plate, the insertion loss added by the microstrip transmission line and the two cable-to-microstrip printed circuit board conversion can be significant, e.g., on the order of 0.4dB at 3.5 GHz. By locating some or all of the calibration circuitry on a microstrip or other printed circuit board already present in the antenna, this insertion loss can be reduced or eliminated, resulting in improved gain performance. With the movement of cellular base stations to higher frequency bands such as 3.5GHz and 5GHz bands, it is particularly important to improve the efficiency of the base station antennas in terms of physical layout and insertion loss performance of next generation calibration circuits.

In some embodiments of the invention, a monolithic feed board may be provided that includes at least one radiating element from each column of radiating elements included in the antenna. The calibration circuit may be implemented entirely on this single feed board. With this design, calibration circuitry can be added to the antenna without increasing the number of connections (e.g., pads or connectors) along the RF signal path through the antenna as compared to an antenna that does not include calibration circuitry. In fact, the only additional connections required to contain the calibration circuit are a pair of additional connections that connect the output of the calibration circuit to the calibration port on the antenna. In contrast, adding a calibration circuit board to a conventional antenna typically adds two connections per column of radiating elements, along with two additional connections for connecting the calibration circuit to the calibration port. These additional connections may increase the cost of manufacturing the antenna and are potential sources of passive intermodulation distortion that may degrade antenna performance.

In other embodiments, the calibration circuitry may be more distributed. For example, in one such embodiment, the radiating elements in each column of radiating elements may be mounted on one or more feed boards. One of the feed plates in each column may include a pair of directional couplers for extracting a small amount of energy from the corresponding radiator of the cross-polarized radiating element mounted on the feed plate and a 2x1 combiner for combining the two extracted RF signals. The output of the 2x1 combiner may then be coupled to another printed circuit board that includes an Nx1 combiner circuit that combines the outputs of the 2x1 combiners to provide a calibration signal. A connector, such as a cable connector, may be used to pass the calibration signal output by the Nx1 combiner to the calibration port of the antenna.

In still other embodiments, a first portion of each directional coupler of the calibration circuit may be implemented on one or more of the feed boards and a second portion of each directional coupler may be implemented on the calibration circuit board. Electromagnetic coupling may be used to couple RF energy from the first portion to the second portion of each directional coupler. In these embodiments, the feed board may be positioned on the front side of the back plate of the antenna, and the calibration circuit board may be positioned on the back side of the back plate. This approach may allow for the use of a small feed board and may reduce the number of pads required to implement the calibration circuit.

In still other embodiments, the directional coupler of the calibration circuit may be implemented on the main printed circuit board of the phase shifter included in the antenna to achieve remote electronic downtilt. For example, the microstrip directional coupler may be implemented along an "input trace" on the main printed circuit board of each phase shifter (i.e., a trace connecting the input cable to the power splitter of the phase shifter). Each directional coupler extracts a small amount of RF energy (which may be referred to as an "extracted calibration signal") which is then passed from the printed circuit board of the phase shifter to a calibration combiner circuit that combines the extracted calibration signals received from each phase shifter. The output of the calibration combiner circuit may be coupled to a calibration port of the antenna. In an alternative embodiment, the directional coupler may still be implemented on the main printed circuit board of each phase shifter, but may be implemented after the input RF signal has been subdivided by the power divider circuitry on the phase shifter printed circuit board. For example, conventional phase shifters for base station antennas typically divide an input signal into X sub-components and then apply a variable phase shift to X-1 of these sub-components. When such a phase shifter is used, the directional coupler may be implemented along a transmission path for sub-components of the input signal that are not phase shifted. As with the embodiments described above, each extracted calibration signal may be passed from the printed circuit board of the phase shifter to a calibration combiner circuit that combines the extracted calibration signals, and the combined calibration signal may then be passed to a calibration port of the antenna.

In still further embodiments, the calibration circuit may be implemented at least in part on other printed circuit boards within the base station antenna, such as a diplexer printed circuit board or a power splitter printed circuit board that holds the declined base station antenna.

Aspects of the present invention will now be discussed in more detail with reference to fig. 2-14, fig. 2-14 illustrating an example embodiment of a base station antenna including calibration circuitry in accordance with the present invention.

Fig. 2 is a schematic perspective view of a beamforming antenna 100 that may be designed to include any calibration circuit according to an embodiment of the present invention. As shown in fig. 2, the beam forming antenna 100 has four columns 110 of dual polarized radiating elements 120 mounted on a planar back plate 102. Each column 110 of radiating elements 120 has the same azimuthal pointing angle. The antenna 100 includes a total of eight RF ports 130, i.e., two RF ports 130 for each column (one port for each polarization) and a ninth port 132 for calibration. A radome (not shown) is mounted on the radiating element 120 to provide environmental protection.

Fig. 3 is a schematic diagram illustrating a base station antenna 200 with conventional calibration circuitry. As shown in fig. 3, the base station antenna 200 includes four columns 210 of dual polarized radiating elements 220 extending forward from the back plane 202. The base station antenna 200 also includes eight RF ports 230 and a calibration port 232.

The RF signal may be coupled between the RF port 230 and the column 210 of radiating elements 220. Because dual polarized radiating elements 220 are provided, two RF ports 230 are associated with each column 210, namely a first RF port 230 feeding a first polarized radiator 222 (e.g., -45 ° dipole) of the radiating elements 220 in the column 210 and a second RF port 230 feeding a second polarized radiator 224 (e.g., +45° dipole) of the radiating elements 220 in the column 210.

Eight input cables 240, which may be implemented as, for example, coaxial cables, may be provided to connect each of the RF ports 230 to the calibration circuit board 250. Typically, each input cable 240 is soldered to a corresponding fixture (fixture) 252 on the calibration circuit board 250 to provide an electrical path between each input cable 240 and a corresponding RF transmission line 254 on the calibration circuit board 250.

Each RF transmission line 254 may extend between a respective one of the fixtures 252 and a respective one of the plurality of fixtures 256. Each mount 256 may receive a respective one of a plurality of jumper (jumper) cables 272 extending between calibration circuit board 250 and a plurality of electromechanical phase shifters 270, as will be discussed in further detail below.

Calibration circuitry 260 is provided on calibration printed circuit board 250. The calibration circuit 260 may include, for example, a plurality of directional couplers 262 and a calibration combiner 264, wherein the number of directional couplers 262 may correspond to the number of RF ports 230 (e.g., eight directional couplers in the example of fig. 3). Each directional coupler 262 may be used to extract a small amount of any RF signal passing along a corresponding one of the RF transmission lines 254. In the depicted embodiment, each directional coupler 262 is implemented as a trace 263 extending substantially parallel alongside a respective one of the RF transmission lines 254. As the RF signal travels along one of the RF transmission lines 254, a small portion of the RF energy will electromagnetically couple to the trace 263 such that the trace 263 and adjacent segments of the RF transmission line 254 together form a directional coupler 262. Trace 263 may be referred to herein as a "tap port" of directional coupler 262 because a small portion of the RF signal traveling along RF transmission line 254 is tapped onto trace 263.

As can also be seen in fig. 3, the calibration combiner 264 is implemented using seven 2x1 combiners 266, the calibration combiner 264 combining any RF signals present at the outputs of the eight directional couplers 262 together into a single RF signal. As shown, the traces 263 of each set of two adjacent directional couplers 262 are connected to the input of a respective one of the four 2x1 combiners 266. The fifth 2x1 combiner 266 is used to combine the outputs of the first 2x1 combiner 266 and the second 2x1 combiner 266, and the sixth 2x1 combiner 266 is used to combine the outputs of the third 2x1 combiner 266 and the fourth 2x1 combiner 266. The seventh 2x1 combiner 266 combines the outputs of the fifth 2x1 combiner 266 and the sixth 2x1 combiner 266. Each 2x1 combiner 266 may be implemented using any conventional power coupler. For example, combiner 266 may be implemented using Wilkinson (Wilkinson) power couplers. The output of the seventh 2x1 combiner 266 is connected to the calibration fixture 253 and a calibration cable 280 connects the calibration fixture 253 to the calibration port 232 on the antenna 200.

Each mount 256 on the calibration circuit board 250 houses a respective jumper cable 272 that connects the mount 256 to a respective one of the plurality of phase shifters 270. The phase shifter 270 is configured to split the RF signal provided at its input port 274 into a plurality of subcomponents and then apply an adjustable phase taper (phase taper) to the RF subcomponents. The output of each phase shifter 270 is connected to the feed plate 212 of a respective column 210 of radiating elements so as to allow RF signals to pass between the phase shifters 270 and the feed plate 212. Each column 210 has an associated first polarization phase shifter 270 and an associated second polarization phase shifter 270. The first polarization phase shifter 270 for each column has three outputs connected (via three respective phase cables 276) to respective RF transmission lines 214 provided on each of the three feed plates 212 in the column 210. Each RF transmission line 214 passes through a respective splitter 216 such that the RF transmission line 214 may be connected to a first polarized radiator 222 of each of two radiating elements 220 mounted on the feed plate 212. In this manner, each output of the first polarization phase shifter 270 may be connected to the first polarized radiator 222 of two radiating elements 220 on a respective one of the feed plates 212. Similarly, the second polarization phase shifter 270 for each column 210 has three outputs connected (via respective phase cables 276) to respective RF transmission lines 215 provided on each of the three feed plates 212 in the column 210. Each RF transmission line 215 passes through a respective splitter 217 such that the RF transmission line 215 may be connected to a second polarized radiator 224 of each of the two radiating elements 220 mounted on the feed plate 212. In this manner, each output of the second polarization phase shifter 270 may be connected to the second polarized radiator 224 of two radiating elements 220 on a respective one of the feed plates 212.

As discussed above, the calibration circuit 260 is used to identify any undesired variations in the amplitude and/or phase of the RF signals input to the different RF ports 230 of the beamforming antenna 200. In particular, the calibration circuit 260 extracts a small amount of each of the RF signals input to the antenna 200, and then combines these extracted "calibration" signals and passes them back to the radio generating the RF signals. The radio may use this information to ensure that the amplitude and phase weights applied to the RF signals sent to the various columns 210 of radiating elements 220 provide an optimized antenna beam.

Calibration circuitry 260 in base station antenna 200 may allow for the use of short input cable 240 because calibration circuit board 250 may be located in close proximity to RF port 230. Furthermore, the calibration circuit 260 can easily pass tolerance testing because the short input cable 240 should exhibit little variation. However, the conventional calibration circuit design shown in fig. 3 has several drawbacks. First, this design positions the calibration circuit board 250 adjacent to the RF port 230 at the base of the antenna 200, which is also the traditional location of RET actuators. The current trend for base station antennas is to include a large number of independently controlled phase shifters, and thus many antennas include six, twelve or even more independently controlled phase shifters, requiring a corresponding number of RET actuators. Thus, antenna designers often need to position a large number of RET actuators near the base of the antenna, which often requires lengthening the length of the antenna. However, increasing the length of the antenna generally has negative consequences in terms of cost, weight, and customer satisfaction.

In addition, RET actuators typically include a DC motor. When the motors are operated, they may generate noise that negatively affects the RF signals on the calibration circuit board, especially since the calibration circuit board is often implemented as an unshielded microstrip (microsstrip) printed circuit board. Moreover, while conventional calibration circuits can well identify amplitude and phase variations that may occur for RF signals passing along each RF transmission path between a radio and an antenna, conventional calibration circuits do little to identify amplitude and phase variations that occur for RF signals passing through the feed network of a base station antenna. Thus, if there is such a change (e.g., because a portion of the antenna is in sunlight and the rest is in shadow, resulting in a temperature change affecting the relative phase), then the amplitude and phase weights used to perform beamforming may not be ideal, resulting in antenna pattern degradation.

Finally, as shown in fig. 3, two cable connectors per column and two other cable connectors for calibration cable 280 are typically made to calibration circuit board 250, creating eighteen additional connection points in antenna 200. Each connection point is typically achieved by soldering one end of the cable to the printed circuit board. However, these welded connections are time consuming to implement and are a potential source of passive intermodulation distortion ("PIM"). Calibration circuit designs according to embodiments of the present invention may reduce the number of pads required and/or may overcome other drawbacks associated with conventional calibration circuit designs.

Fig. 4 is a schematic diagram illustrating a base station antenna 300 according to an embodiment of the present invention. As shown in fig. 4, the base station antenna 300 includes four columns 310 of dual polarized radiating elements 320. Each radiating element 320 may be mounted to extend forward from the back plate 302. Any suitable radiating element may be used. In an example embodiment, each radiating element 320 may include a pair of circuits (walk) such as two printed circuit boards (only dipole radiators 322, 324 are shown in fig. 4) extending forward from the back plane 302 with a pair of dipole radiators 322, 324 formed or mounted thereon. The circuit may be arranged in an "X" configuration and the radiators 322, 324 may be arranged in a "cross dipole" arrangement, with the first radiator 322 being placed at an angle of-45 ° to the vertical axis and the second radiator 324 being placed at an angle of +45° to the vertical axis, such that both radiators 322, 324 will radiate in orthogonal polarizations.

The back plate 302 may comprise a single structure or may comprise multiple structures attached together. The back plate 302 may comprise a reflector, for example, that serves as a ground plane for the dual polarized radiating element 320. Each column 310 of radiating elements 320 may be oriented substantially vertically with respect to a horizontal plane when the base station antenna 300 is installed for use. In the depicted embodiment, each column 310 includes a total of six radiating elements 320. However, it will be appreciated that other numbers of radiating elements 320 may be included in each column 310, and that different numbers of columns 310 may be included in the antenna 300. The same is true for the embodiments of the invention discussed herein.

The base station antenna 300 includes eight RF ports 330 and a calibration port 332. Each RF port 330 may be coupled to a corresponding port of a multi-port radio (not shown) by a jumper cable (not shown). The RF port 330 may be mounted, for example, in a substrate of the housing of the antenna 300. The RF signal is coupled between the RF port 330 and the column 310 of radiating elements 320. Because of the provision of dual polarized radiating elements 320, two RF ports 330 are associated with each column 310, namely a first RF port 330 feeding a first polarized radiator 322 (e.g., -45 ° dipole) of the radiating elements 320 in the column 310 and a second RF port 330 feeding a second polarized radiator 324 (e.g., +45° dipole) of the radiating elements 320 in the column 310.

Eight input cables 340, which may include, for example, coaxial cables, are provided that connect each of the RF ports 330 to a respective one of the plurality of electromechanical phase shifters 370. Each electromechanical phase shifter 370 is configured to split the RF signal provided at its input port 374 (using one or more power splitters such as directional couplers) into a plurality of subcomponents and to apply an adjustable phase taper to the subcomponents. The amount of phase taper may be adjusted by mechanically changing the setting of the electromechanical phase shifter 370. Since the calibration circuit board for the antenna 300 is not located on the electrical path between the RF port 330 and the corresponding phase shifter 370, the antenna 300 may be shortened compared to the antenna 200, as schematically shown in fig. 4.

The phase shifters 370 may be implemented, for example, using "wiper" phase shifters, each comprising a main printed circuit board and a "wiper" printed circuit board rotatable over the main printed circuit board. The wiper phase shifter may divide an input RF signal received at the main printed circuit board into a plurality of sub-components and then capacitively couple at least some of these sub-components to the wiper printed circuit board. Further subdivision of the RF signal can be performed on the wiper printed circuit board. The subcomponents of the RF signal may be capacitively coupled back from the wiper printed circuit board to the main printed circuit board along a plurality of arcuate traces, where each arc has a different diameter. Each end of each arcuate track may be connected to a radiating element or a subset of radiating elements. By physically (mechanically) rotating the wiper printed circuit board over the main printed circuit board, the position at which sub-components of the RF signal are capacitively coupled back to the main printed circuit board can be changed, which thus changes the length of the respective transmission path from the phase shifter to the associated radiating element for each sub-component of the RF signal. These path length variations result in phase variations of the corresponding sub-components of the RF signal and, since the arcs have different radii, the phase variations along the different paths will be different. Typically, phase taper is applied by applying positive phase shifts of various magnitudes (e.g., + x°) to one or more sub-components of the RF signal and by applying negative phase shifts of the same magnitude (e.g., -x°) to one or more additional sub-components of the RF signal. In addition, the phase shifter 370 typically includes a transmission path that is not coupled to the wiper printed circuit board and therefore does not undergo an adjustable phase change. An electromechanical actuator, such as a DC motor connected to the wiper printed circuit board via a mechanical linkage (linkage), may be used to move the wiper printed circuit board.

Still referring to fig. 4, the radiating element 320 is mounted on a plurality of feed plates 312, 313. In the exemplary embodiment shown in fig. 4, each feed plate 312 has two radiating elements 320 mounted thereon. Two radiating elements 320 at the top of each column 310 are mounted on the feed plate 312, and two radiating elements 320 at the bottom of each column 310 are mounted on the other feed plate 312. The feed plate 313 is a larger feed plate on which eight radiating elements 320 are mounted (i.e., the middle two radiating elements 320 for each of the four columns 310). The feed board 313 serves as both a feed board including an RF transmission line connected to the radiating element 320 mounted on the feed board 313 and a calibration circuit board including the calibration circuit 360. Eight phase cables 376 are provided which connect the first output of each phase shifter 370 to one of the feed plates 312 located at the top of the four columns 310 (each feed plate 312 is fed by two phase cables 376, one phase cable 376 for each of the two polarizations). An additional eight phase cables 376 connect the second output of each phase shifter 370 to the feed plate 313, and another set of eight phase cables 376 connect the third output of each phase shifter 370 to one of the feed plates 312 at the bottom of the four columns 310. Three outputs of each first polarization phase shifter 370 are coupled to first polarized radiators 322 of six radiating elements in a respective one of columns 310, and three outputs of each second polarization phase shifter 370 are coupled to second polarized radiators 324 of six radiating elements in a respective one of columns 310. In some embodiments, the output of the phase shifter 370 connected to the feed plate 313 may be the output of the phase shifter 370 that is not subject to an adjustable phase shift.

The feed plate 312 may be the same as the feed plate 212 described above with respect to fig. 3. In particular, each feed plate 312 may include a first RF transmission line 314 coupled to one of the outputs of a respective one of the first polarization phase shifters 370, and a second RF transmission line 315 coupled to one of the outputs of a respective one of the second polarization phase shifters 370. On each feed plate 312, a first RF transmission line 314 is coupled to a first splitter 316, and the output of the first splitter 316 is connected to a first polarized radiator 322 of each of two radiating elements 320 mounted on the feed plate 312. Likewise, a second RF transmission line 315 is coupled to a second splitter 317, and an output of the second splitter 317 is connected to a second polarized radiator 324 of each of the two radiating elements 320 mounted on the feed plate 312.

For each pair of radiating elements 320 mounted on the feed plate 313, the feed plate 313 likewise comprises a first RF transmission line 314 and a second RF transmission line 315 and a first splitter 316 and a second splitter 317, which are connected in the same way as the feed plate 312, the only difference being that a single large feed plate 313 is provided for eight radiating elements 320 instead of four smaller feed plates 312.

Calibration circuitry 360 is also provided on the feed board 313. The calibration circuit 360 may include, for example, a plurality of directional couplers 362 and a calibration combiner 364, wherein the number of directional couplers 362 may correspond to the number of RF ports 330 (e.g., eight directional couplers 362). Each directional coupler 362 may be used to extract a small amount of any RF signal passing along a corresponding one of the RF transmission lines 314, 315. In the depicted embodiment, each directional coupler 362 is implemented as a trace 363 that extends substantially parallel alongside a respective one of the RF transmission lines 314, 315. As the RF signal travels along one of the RF transmission lines 314, 315, a small portion of the RF energy will electromagnetically couple to the trace 363 of the directional coupler 362 formed along the RF transmission line 314, 315. Trace 363 may be referred to herein as a "tap port" of directional coupler 362 because a small portion of the RF signal traveling along RF transmission lines 314, 315 is tapped to trace 363.

The calibration combiner 364 is implemented using seven 2x1 combiners 366, the seven 2x1 combiners 366 combining any RF signals present at the outputs of the eight directional couplers 362 together into a single RF signal. As shown, the traces 363 of each set of two adjacent directional couplers 362 are connected to the inputs of four 2x1 combiners 366. The fifth 2x1 combiner 366 is configured to combine the outputs of the first 2x1 combiner 366 and the second 2x1 combiner 366, and the sixth 2x1 combiner 366 is configured to combine the outputs of the third 2x1 combiner 366 and the fourth 2x1 combiner 366. The seventh 2x1 combiner 366 combines the outputs of the fifth 2x1 combiner 366 and the sixth 2x1 combiner 366. Each combiner 366 may be implemented using any conventional power coupler. For example, combiner 366 may be implemented using a wilkinson power coupler. The output of the seventh 2x1 combiner 366 is connected to a calibration fixture 353 and a calibration cable 380 connects the calibration fixture to a calibration port 332 on the antenna 300.

Thus, the base station antenna 300 includes a back plane 302 and a plurality of radiating elements 320 extending forward from the back plane 302. The antenna 300 further includes a plurality of feed plates 312, 313, and each of the feed plates 312, 313 has a respective set of one or more radiating elements 320 mounted thereon. The antenna 300 further includes a calibration port 332 and a calibration circuit 360, the calibration circuit 360 having a calibration combiner 364 and a plurality of directional couplers 362, the calibration combiner 364 having an output coupled to the calibration port 332, the plurality of directional couplers 362 being coupled to the calibration combiner 364. At least a first portion of the first directional couplers in the first directional coupler 362 is implemented on the feed plate 313.

The radiating elements 320 are arranged to define a first column 310 of radiating elements 320 and a second column 310 of radiating elements 320. The antenna 300 further includes a first electromechanical phase shifter 370 electrically coupled between the first RF port 330 of the antenna 300 and the first column 310 of radiating elements 320, and a second electromechanical phase shifter 370 electrically coupled between the second RF port 330 of the antenna 300 and the second column 310 of radiating elements 320. The calibration circuit 360 includes a first directional coupler 362 coupled along a first RF transmission path extending between the input of the first electromechanical phase shifter 370 and a first one of the radiating elements 320 in the first column 310, and a second directional coupler 362 coupled along a second RF transmission path extending between the input of the second electromechanical phase shifter 370 and the first one of the radiating elements 320 in the second column 310.

The calibration circuit 360 is used to identify any undesired variations in the amplitude and/or phase of the RF signals input to the different RF ports 330 of the beamforming antenna 300. In particular, calibration circuit 360 couples a small number of RF signals input to antenna 300 through each RF port 330, and then combines these extracted "calibration" signals and passes them back to the radio generating the RF signals. When performing a calibration operation, the radio may transmit RF signals at different frequencies or RF signals each including a unique code to each RF port 330, such that a receiver at the radio can distinguish between the received calibration signals to determine the relative amplitude and phase of each calibration signal. The radio may use this information to ensure that the amplitude and phase weights applied to the RF signals sent to the various columns 310 of radiating elements 320 provide an optimized antenna beam.

Calibration circuit 360 may have a number of advantages over prior art calibration circuits. First, the calibration circuit board 313 is removed from the RF port 330. This reduces the impact that the RET actuator may have on the calibration circuitry and also reduces the number of elements located at the base of the antenna 300. This may allow for a shorter antenna. Furthermore, since the calibration circuit board is located on the feed board, the calibration circuit 360 can also identify amplitude and phase variations that occur in the feed network of the antenna 300, and thus the radio can adjust the amplitude and phase weights to correct for any such variations, allowing improved beamforming. Also, as can be seen by comparing fig. 2 and 3, antenna 300 includes eight fewer cables (i.e., jumper cable 272 of antenna 200 is not included in antenna 300), and thus sixteen pads may be less needed in antenna 300. Solder joints are time consuming to complete in manufacture and are a potential source of passive intermodulation distortion. Thus, the base station antenna 300 is cheaper to manufacture and may provide improved performance compared to prior art base station antennas.

Fig. 5 is a schematic diagram illustrating a base station antenna 400 according to other embodiments of the present invention. As will be apparent from the following description, the base station antenna 400 includes the attributes of the conventional base station antenna 200 and the base station antenna 300.

The base station antenna 400 comprises four columns 410 of dual polarized radiating elements 420 having a first radiator 422 and a second radiator 424. The radiating element 420 is mounted on a plurality of feed plates 412, 413. Each radiating element 420 extends forward from the back plate 402. The base station antenna 400 also includes eight RF ports 430 and a calibration port 432. An input cable 440 connects each RF port 430 to a respective one of the plurality of electromechanical phase shifters 470, and a phase cable 476 connects the output of the phase shifter 470 to the feed plates 412, 413. Back plane 402, radiating element 420, RF port 430, calibration port 432, input cable 440, phase shifter 470 and phase cable 476 may be the same as back plane 302, radiating element 320, RF port 330, calibration port 332, input cable 340, phase shifter 370 and phase cable 376 discussed above, and thus further description thereof will be omitted herein. The base station antenna 400 also includes a calibration circuit 460, the calibration circuit 460 being described in more detail below.

Each feed plate 412, 413 may have two radiating elements 420 mounted thereon. The feeding plate 412 may be the same as the feeding plate 312, and thus a further description thereof will be omitted herein. The feed plate 413 in combination with the calibration circuit board 450 provides different ways of implementing the calibration circuit along the electrical path between the phase shifter and the radiating element of the base station antenna.

In particular, four small feed plates 413 are provided in the base station antenna 400, as compared to the larger feed plate 313 included in the base station antenna 300. Each feed plate 413 includes a first RF transmission line 414 coupled to one of the outputs of a respective one of the first polarization phase shifters 470 and a second RF transmission line 415 coupled to one of the outputs of a respective one of the second polarization phase shifters 470. The first RF transmission line 414 is coupled to a first splitter 416 and the output of the first splitter is connected to a first polarized radiator 422 of each of two radiating elements 420 mounted on a feed plate 413. Likewise, the second RF transmission line 415 is coupled to a second splitter 417, and the output of the second splitter 417 is connected to a second polarized radiator 424 of each of the two radiating elements 420 mounted on the feed plate 413.

In addition, each feed board 413 includes a portion of calibration circuit 460. As in other embodiments discussed herein, the calibration circuit 460 may include eight directional couplers 462 for tapping off a small portion of the RF energy input from each RF port 430 of the antenna 400, and a combiner circuit 464 for combining the tapped off RF energy into a single composite RF signal. The directional coupler 462 may be implemented in the same manner as the directional coupler 362 described above, i.e., as a trace 463 extending generally parallel alongside a respective one of the RF transmission lines 414, 415. As shown in fig. 5, each feed plate 413 includes two of the directional couplers 462 for tapping a fraction of the RF energy fed to the respective first and second radiators 422, 424 of the radiating element 420 mounted on each feed plate 413. In some embodiments, the output of the phase shifter 470 connected to the feed plate 413 may be an output of the phase shifter 470 that is not subject to an adjustable phase shift. The directional coupler 462 may be identical to the directional coupler 362 described above, and thus a further description thereof will be omitted. The tap ports of the two directional couplers 462 on each feed plate 413 are input to a 2x1 combiner 466 formed on the feed plate 413, and the 2x1 combiner 466 combines the two tapped RF signals into a composite signal. The output of each "feeder board" 2x1 combiner 466 may be coupled to the calibration circuit board 450 by a cable connection (or some other suitable transmission line structure).

The calibration circuit board 450 may include three additional 2x1 combiners 466 (or a single 4x1 combiner) that combine the outputs of the four 2x1 combiners 466 provided on the respective feeder boards 413. Seven 2x1 combiners 466 may be arranged in the same manner as combiner 366, except that 2x1 combiners 466 are distributed across multiple circuit boards 413, 450, and combiner 366 is all implemented on the same calibration circuit board 313. The 2x1 combiner 466 may be implemented in the same manner as the combiner 366 (e.g., as a wilkinson power combiner) and the output of the last 2x1 combiner 466 in the tree structure may be electrically connected to the calibration port 432 via a calibration cable 480.

It is clear that the calibration circuit 460 is similar to the calibration circuit 360 described above, with the main difference being that one large circuit board 313 included in the base station antenna 300 is replaced with four smaller feed boards 413 and a small calibration circuit board 450 in the base station antenna 400. This approach eliminates the need for a large circuit board (which tends to be expensive) and allows the feed plate 413 to be very similar to the feed plate 412, which may simplify the design process. Further, it should be noted that the feed plates (e.g., feed plates 312, 313, 412, 413) are typically mounted on the front side of the back plate of the antenna. Thus, radiation emitted by the radiating element of the antenna may be incident on the feed plate, potentially injecting noise into the calibration signal. In base station antenna 400, calibration circuit board 450 may be mounted on the back side of back plate 402, where back plate 402 shields the circuitry on the back plate from the RF energy emitted by radiating element 420. Accordingly, since a portion of the calibration circuitry 460 is mounted behind the back plate 402, the calibration circuitry 460 in the base station antenna 400 may have reduced sensitivity to such RF noise. However, the base station antenna 400 may include four more cable connections (and thus eight more pads) than the base station antenna 300 because cable connections may be used to connect the output of each 2x1 combiner 466 on the four feed boards 413 to the calibration circuit board 450.

Fig. 6 is a schematic diagram illustrating a base station antenna 500 according to other embodiments of the present invention. Base station antenna 500 may combine some of the advantages provided in base station antenna 300 and base station antenna 400 described above. Accordingly, the following description will focus on the differences between the base station antenna 500 and the above base station antennas 300, 400.

As shown in fig. 6, the base station antenna 500 includes four feed boards 513 and a calibration circuit board 550. The feed plate 513 may be similar to the conventional feed plate 212 except that the feed plate 513 may be designed to facilitate coupling of RF energy from RF transmission lines 514, 515 formed on the feed plate to traces (or other structures) on the calibration circuit board 550 through openings in the back plate 502.

Fig. 7 is an enlarged schematic front view of one of the feed plates 513 and a portion of the back plate 502 and a calibration circuit board 550 positioned behind the feed plate 513, which better illustrates the design and operation of the calibration circuit 560 included in the base station antenna 500. Fig. 8 is a schematic front view illustrating a calibration circuit board 550 on which a calibration combiner circuit 564 is implemented. It should be noted that fig. 6 does not illustrate various circuit elements included on the calibration circuit board 550 for simplicity of the drawing, but these circuit elements are shown in fig. 8.

Referring to fig. 6-8, the back plate 502 may have a pair of openings 504 behind each feed plate 513. The calibration circuit board 550 is positioned behind the back plate 502. A pair of RF transmission lines 514, 515 provided on each feed plate 513 that carry RF energy output from the phase shifter 570 to respective first 522 and second 524 radiators of the radiating element 520 may, for example, comprise a section 518 extending on the backside of the feed plate 513 near the opening 504 in the back plate 502. The calibration circuit board 550 may include conductive structures 552 such as, for example, widened mesas of conductive pads immediately behind each opening 504 in the backplate 502. Thus, RF energy present on one of the segments 518 may be electromagnetically coupled from the segment 518 to the corresponding conductive structure 552 through the opening 504 in the backplate 502. Thus, it should be appreciated that each combination of the segments 518 and the conductive structures 552 forms a directional coupler 562, the directional coupler 562 tapping a small portion of the RF energy flowing on a respective one of the RF transmission lines 514. Thus, in the embodiment of fig. 6, the directional coupler 562 of the calibration circuit 560 is implemented as an electromagnetic coupling between different circuit board structures.

As shown in fig. 8, a calibration combiner 564 is formed on the calibration circuit board 550. The calibration combiner 564 is configured to combine the outputs of the directional couplers 562 to provide a composite calibration signal that is routed to the calibration port 532 of the antenna 500. As shown in fig. 8, the calibration circuit board 550 includes eight conductive structures (shown as conductive pads) 552 (see fig. 7) that may be located directly behind each opening 504 in the backplate 502. As described above, each conductive structure 552 forms a portion of a respective one of the directional couplers 562 of the calibration circuit 560. The conductive traces 554 connect each conductive structure 552 associated with a particular feed plate 513 (the location of the feed plate 513 is shown in fig. 8 using a dashed box) to a respective 2x1 combiner 566. The outputs of the four 2x1 combiners 566 connected to the conductive structure are connected to the inputs of two additional 2x1 combiners 566, and the outputs of the two additional 2x1 combiners 566 are coupled to the inputs of the final 2x1 combiner 566 to form a three-level tree structure of 2x1 combiners 566 that acts as an 8x1 calibration combiner 564. The output of the final 2x1 combiner 566 is coupled to a mount 568 that can house a calibration cable 580.

Thus, the base station antenna 500 includes a back plate 502 having a front surface and a back surface, and a plurality of radiating elements 520 extending forward from the back plate 502. A plurality of feed plates 512, 513 are mounted on the front of the back plate 502, wherein each feed plate 512, 513 has a respective set of one or more radiating elements 520 mounted thereon. The antenna 500 also includes a calibration circuit 560, the calibration circuit 560 including a plurality of components 516 mounted in front of the back plate 502 and at least one additional component 552, 566 mounted behind the back plate 502.

The calibration circuit design of the base station antenna 500 may have a number of advantages. First, this arrangement allows the calibration circuit board 550 to be implemented on the back side of the back plate 502, thus the back plate 502 shields the calibration circuit 560 from the RF energy emitted by the radiating element 520. In addition, all calibration combiners 566 may be implemented on the same circuit board 550, and thus base station antenna 500 may have fewer cable connections than, for example, base station antenna 400.

Fig. 9 is a schematic cross-sectional view illustrating another technique for implementing a directional coupler 562 included in the base station antenna 500 of fig. 6. In particular, fig. 9 is a thin cross-section taken through the feed plate 513, the backplate 502, and the calibration circuit board 550 of fig. 6, fig. 9 illustrating an alternative implementation of one of the directional couplers 562 included in the base station antenna 500 that electromagnetically couples RF energy through the opening 504 in the backplate 502.

In practice, the feed board and calibration circuit board included in a base station antenna are typically formed using microstrip printed circuit boards, in some cases implemented using striplines (striplines) or other circuit boards. As known to those skilled in the art, microstrip printed circuit boards are typically implemented as dielectric substrates having a conductive ground plane formed on a first major surface (e.g., a bottom surface) thereof, and a conductive pattern formed on an opposite major surface (e.g., a top surface). The conductive pattern may include one or more traces defining an RF transmission line, and may also include conductive pads or other conductive structures forming circuit elements, input/output ports, and the like. The ground plane is typically formed as a continuous or near continuous sheet of metal that substantially or completely covers the bottom surface of the dielectric substrate. Fig. 9 illustrates one practical implementation of the directional coupler 562 of the base antenna 500 when the feed board 513 and the calibration circuit board 550 are formed as microstrip printed circuit boards.

Referring to the schematic cross-sectional view of fig. 9, it can be seen that the calibration circuit board 550 can be positioned immediately adjacent to the back plate 502 and behind the back plate 502, while the feed board 513 can be positioned immediately adjacent to the back plate 502 and in front of the back plate 502. The feed plate 513 is a microstrip feed plate comprising a dielectric substrate 590 having a ground plane 592 formed on a back surface thereof, with traces of the rf transmission line 514 being formed on a front surface of the dielectric substrate 517. As shown in fig. 9, an opening 594 is provided in the ground plane 592 behind the trace of the RF transmission line 514. The calibration circuit board 550 is also implemented as a microstrip feed board, the calibration circuit board 550 includes a dielectric substrate 557 having a ground plane 558 formed on a front surface thereof, and the conductive structure 552 is formed on a rear surface of the dielectric substrate 557. As further shown in fig. 9, an opening 559 is provided in the ground plane 558 in front of the conductive structure 552. The openings 594, 559 in the respective ground planes 592, 558 of the feed board 513 and the calibration circuit board 550 are aligned with each other and further with the above-described opening 504 in the back plate 502. Thus, when an RF signal is transmitted on the feed plate RF transmission line 514, a small portion of the RF energy will be coupled through the opening 594 in the ground plane 592 of the feed plate 513, through the opening 504 in the back plate 502, through the opening 559 in the ground plane 558 of the calibration circuit board 550, to the RF transmission line 554 on the calibration circuit board 550, which includes and/or is connected to the conductive structure 552. Thus, fig. 9 illustrates a practical implementation of one of the directional couplers 562 included in the calibration circuit 560 of the base station antenna 500. It will be appreciated that the cross-section of fig. 9 is "thin" in the sense that it is taken through a small portion of the antenna and corresponds to one of the openings 504 in the backplate 502, and thus the portions of the backplate 502, the feed plate 513, and the calibration circuit board 550 outside the area of the openings 504 are not shown to more clearly illustrate the openings 504 and the openings 594, 559 in the respective feed plate ground plane 592 and calibration circuit board ground plane 558.

In the example of fig. 9, the directional coupler 562 is formed by a single opening 504 in the backplate 502 (and corresponding openings 594, 559 in the ground planes 592, 558). However, it will be appreciated that in other embodiments, two or more sets of openings may be provided to improve the directivity of directional coupler 562.

Fig. 10 is a schematic diagram illustrating a base station antenna 600 according to a further embodiment of the present invention. The base station antenna 600 is similar to the base station antenna 400 described above, but with at least two basic differences. First, in the base station antenna 600, the directional coupler of the calibration circuit 660 is implemented in the phase shifter 670, not on the feed plate 413 as in the base station antenna 400. Second, in base station antenna 600, the combiner portion of the calibration circuitry is implemented entirely on a single calibration circuit board 650. The following discussion will focus on these two aspects of base station antenna 600 that differ from base station antenna 400.

As shown in fig. 10, the base station antenna 600 may include four columns 610 of dual polarized radiating elements 620, the dual polarized radiating elements 620 having a first radiator 622 and a second radiator 624 mounted on a backplate 602. The radiating element 620 may be mounted on the feed plate 612. In this embodiment, all of the feed plates 612 may be identical. The base station antenna 600 also includes eight RF ports 630 and a calibration port 632. An input cable 640 connects each RF port 630 to a respective one of the plurality of electromechanical phase shifters 670, and a phase cable 676 connects the output of the phase shifter 670 to the feed plate 612. The back plane 602, the feed plate 612, the radiating element 620, the RF port 630, the calibration port 632, the input cable 640, and the phase cable 676 may be the same as the back plane 402, the feed plate 412, the radiating element 420, the RF port 430, the calibration port 432, the input cable 440, and the phase cable 476 discussed above, and thus further description thereof will be omitted herein. The base station antenna 600 also includes a calibration circuit 660, the calibration circuit 660 being described in more detail below. The calibration circuit 660 includes the calibration circuit board 650 described above and eight directional couplers 662, with the eight directional couplers 662 formed as part of the corresponding eight phase shifters 670.

Fig. 11 is a perspective view of a dual rotary wiper phase shifter assembly 700 that may be used to implement two electromechanical phase shifters 670 (one for each of the two polarizations) included in a base station antenna 600. A total of four such phase shifter assemblies 700 are included in the base station antenna 600, one assembly 700 per column of radiating elements 620. As shown in fig. 11, the dual rotary wiper phase shifter assembly 700 includes a first phase shifter 670 and a second phase shifter 670 arranged back-to-back in a back-to-back relationship. The two phase shifters 670 may be identical, and thus only the front phase shifter 670 will be described herein.

As shown in fig. 11, the front phase shifter 670 includes a main (stationary) printed circuit board 710 and a rotatable wiper printed circuit board 720 rotatably mounted on the main printed circuit board 710 by a pivot pin 722. The position of the wiper printed circuit board 720 above the main printed circuit board 710 is controlled by the position of the mechanical linkage 704 (partially shown in fig. 11) extending between the output member of the RET actuator and the phase shifter 700. As the position of mechanical linkage 704 changes, wiper printed circuit board 720 rotates over main printed circuit board 710 to change the relative phase of the subcomponents of the RF signal output by phase shifter 670.

The main printed circuit board 710 includes transmission line traces 712, 714, 716, 718. The transmission line traces 712, 714 are generally arcuate. A first arcuate transmission line trace 712 is disposed along the outer circumference of the main printed circuit board 710 and a second arcuate transmission line trace 714 is disposed concentrically on a shorter radius within the outer transmission line trace 712. The transmission line trace 716 connects an input pad 730 on the main printed circuit board 710 to an input of a directional coupler 750 implemented on the main printed circuit board 710. The first output 752 of the directional coupler 750 is connected to a pad (not shown) on the main printed circuit board 710. A second output 754 of the directional coupler 750 is connected to the transmission line trace 718. The transmission line trace 718 extends between the directional coupler 750 and one of a plurality of output pads 740 disposed along an edge of the main printed circuit board 710.

The center conductor of the input cable 640 (see fig. 10) of the base station antenna 600 may be soldered to the input pad 730 (and the ground conductor of the input cable may be soldered to the ground plane of the main printed circuit board 710). RF signals may pass from one RF port 630 (see fig. 10) of the base station antenna 600 to the input pad 730 through the input cable 640. The RF signal will travel along the transmission line trace 716 to the directional coupler 750. The directional coupler 750 may be configured to unevenly divide the RF energy input thereto such that a majority (e.g., about 80%) of the RF energy is transferred to the first output 752 and the remaining input RF energy is transferred to the second output 754. The RF energy delivered to the first output 752 is then capacitively coupled to a transmission line trace (not visible in fig. 11) on the wiper printed circuit board 720. Another directional coupler (not shown) may be provided along the transmission line trace on the wiper printed circuit board 720 that splits the RF energy delivered to the wiper printed circuit board 720 into two subcomponents. These two subcomponents of the RF signal are capacitively coupled from the output of the directional coupler on the wiper printed circuit board 720 to the corresponding transmission line trace 712, 714 on the main printed circuit board. The subcomponent of the RF signal coupled to the transmission line trace 714 may be split into two subcomponents, with a first subcomponent traveling along the transmission line trace 714 (from the vantage point of fig. 11) to the left and a second subcomponent traveling along the transmission line trace 714 to the right. Similarly, a subcomponent of the RF signal coupled to the transmission line trace 712 may likewise be split into two subcomponents, with a first subcomponent traveling to the left along the transmission line trace 712 and a second subcomponent traveling to the right along the transmission line trace 712. Each end of each transmission line trace 712, 714 may be coupled to a respective output pad 740. Thus, the phase shifter 670 splits the RF signal input at pad 730 into five components, which pass to five corresponding output pads 740.

As wiper printed circuit board 720 moves, the electrical path length from input pad 730 of phase shifter 670 to four of the five output pads 740 (i.e., output pads 740 connected to arcuate transmission line traces 712, 714) may change. For example, when wiper printed circuit board 720 moves to the left, it shortens the electrical path length from input pad 730 to output pad 740 (which is connected to first radiating element 620) connected to the left side of transmission line trace 712, while the electrical length from input pad 730 to output pad 740 (which is connected to second radiating element 620) connected to the right side of transmission line trace 712 increases by a corresponding amount. These changes in path length result in a phase shift of the signal received at the output pad 740 connected to the transmission line trace 712 relative to, for example, the output pad 740 connected to the transmission line trace 718.

As shown in fig. 11, the rotating wiper printed circuit board 720 of the rear phase shifter 670 may be controlled by the same mechanical linkage 704 as the rotating wiper printed circuit board 720 of the top phase shifter 670. This arrangement is typically used when the column 610 of radiating elements 620 is a column 610 of dual polarized radiating elements 620, as the same phase shift is typically applied to the RF signals transmitted on each of the two orthogonal polarizations. Thus, a single mechanical linkage 704 may be used to control the position of wiper printed circuit board 720 on both phase shifters 670.

The main printed circuit 710 further includes a directional coupler 662 for tapping off a small portion of the RF signal input at the input pad 730. The directional coupler 662 may be implemented, for example, as a microstrip trace extending along the transmission line trace 716 or as any other suitable directional coupler design. A portion of the RF signal passing along the transmission line trace 716 may be electromagnetically coupled to the trace of the directional coupler 662 and passed to the calibration pad 780. In an example embodiment, approximately 3-6% of the RF energy may be coupled to the traces of directional coupler 662. An end (not shown) of an RF transmission line, such as, for example, an end of a coaxial cable, may be connected to calibration pad 780. The other end of the coaxial cable may be connected to a calibration printed circuit board 650 (see fig. 10).

Referring again to fig. 10, calibration printed circuit board 650 includes combiner circuit 664 that combines the RF energy tapped from each phase shifter 670 into a single composite RF signal. The combiner circuit 664 is schematically illustrated in fig. 10 as a block. The combiner circuit 664 may include, for example, seven 2x1 power combiners that combine eight tapped signals into a single composite calibration signal. For example, seven 2x1 combiners may be arranged in the same manner as the combiner 366 discussed above with reference to fig. 4, and may be implemented in the same manner (e.g., as a wilkinson power combiner). The output of the last 2x1 combiner in the tree may be electrically connected to a calibration port 632 through a calibration cable 680, as shown in fig. 10.

The calibration circuit 660 is similar to the calibration circuit 460 described above, with the primary difference being that the calibration signal is tapped from the phase shifter 670 rather than from the feed plate. This approach may be advantageous because the phase shifter 670 is located on the back side of the reflector 602 and the feed plate 612 is typically located on the front side of the reflector 602, so that if the directional coupler 662 is implemented as part of the phase shifter 670, it may be easier to connect the directional coupler to the calibration printed circuit board 650. In addition, by moving the directional coupler 662 from the feed plate 612 to the main printed circuit board 710 of the phase shifter 670, the likelihood that radiation emitted by the radiating element 620 of the base station antenna 600 will introduce noise into the calibration signal may be reduced.

Fig. 12 is a perspective view of a phase shifter assembly 700' that is a modified version of the phase shifter assembly 700 of fig. 11. According to other embodiments of the present invention, a phase shifter assembly 700' may be used in place of the phase shifter assembly 700 in a base station antenna. It can be seen that the phase shifter assembly 700' can be identical to the phase shifter 700 except that the directional coupler 662' included in the base station antenna 700' is formed on the transmission line trace 718 instead of on the transmission line trace 716. This arrangement may be advantageous because the addition of the directional coupler of the calibration circuit 660 increases the insertion loss along the RF path. By positioning the directional coupler 662' after the directional coupler 750, the effects of insertion loss can be reduced. As described above, in the exemplary embodiment, only about 20% of the RF energy input to the phase shifter 670 is transferred to the transmission line trace 718. The directional coupler 662' may then extract approximately 5% of the RF energy delivered to the transmission line trace 718, for example. Thus, since directional coupler 662 'is positioned after directional coupler 750, the insertion loss of directional coupler 662' only degrades each RF signal by approximately 20%, effectively reducing the insertion loss by approximately 80%. The directional coupler 662' may be formed along the output trace of each phase shifter 670 that is not subject to the effects of variable phase shifts (i.e., transmission line trace 718).

While fig. 11 and 12 illustrate implementation of the calibration coupler on the main printed circuit board of a rotary wiper arc phase shifter, it should be appreciated that portions of the calibration circuit may be implemented on the printed circuit board of any conventional phase shifter, including, for example, trombone slide dielectric phase shifters, phase shifters comprising multiple rotary wiper printed circuit boards, and the like. It should therefore be appreciated that the rotary wiper arc phase shifters depicted in fig. 11 and 12 are provided merely as examples of possible implementations on a phase shifter circuit board in accordance with the concepts of the present invention.

Fig. 13 is a schematic diagram of a modified version of a base station antenna 800 including calibration circuitry included in the base station antenna 500 of fig. 6-8. Base station antenna 800 combines the features of base station antenna 400 of fig. 5 and base station antenna 500 of fig. 6-8. In particular, the base station antenna 800 implements four combiners 866 of the calibration combiners on the feed plate 813 as in the base station antenna 400 of fig. 5, and electromagnetically couples the calibration signal from the feed plate to the calibration circuit board 850 as in the base station antenna 500 of fig. 6-8. This arrangement reduces the number of slots required in the reflector 802 and allows for the use of a smaller calibration circuit board 850.

As shown in fig. 13, the base station antenna 800 includes four columns 810 of dual polarized radiating elements 820 having a first radiator 822 and a second radiator 824 mounted on a backplate 802. The radiating element 820 may be mounted on the feed plates 812 and 813. The base station antenna 800 also includes eight RF ports 830 and a calibration port 832. An input cable 840 connects each RF port 830 to a respective one of the plurality of phase shifters 870, and a phase cable 876 connects the output of the phase shifter 870 to the feed plates 812, 813. The back plane 802, the feed plane 812, the radiating element 820, the RF port 830, the calibration port 832, the input cable 840, and the phase cable 876 may be the same as the back plane 402, the feed plane 412, the radiating element 420, the RF port 430, the calibration port 432, the input cable 440, and the phase cable 476 discussed above, and thus further description thereof will be omitted herein.

As further shown in fig. 13, the base station antenna 800 includes a calibration circuit board 850, the calibration circuit board 850 being mounted under four feed boards 813 with the backplate 802 therebetween. The feed plates 813 may be similar to the feed plate 513 of the base station antenna 500 except that each feed plate 813 may also include a combiner 866 thereon, the combiner 866 combining the RF energy from the two RF transmission lines 814, 815 tapped by the directional coupler 862. The output of each combiner 866 is electromagnetically coupled to a trace (or other structure) on the calibration circuit board 850 through a corresponding opening 806 in the backplate 802. Fig. 14 is a schematic exploded perspective view of a portion of the base station antenna of fig. 13, further illustrating the design and operation of calibration circuitry 860 included in base station antenna 800. In particular, fig. 14 illustrates a portion of one of the feed plates 813 and portions of the reflector 802 and calibration circuit board 850 located behind the feed plate 813.

Referring to fig. 14, the feed plate 813 includes a pair of feed points 882, each feed point 882 receiving a center conductor of a respective one of the phase cables 876 (the outer conductor of each phase cable 876 may be soldered to a ground plane formed on the back side of the feed plate 813). Each feed point 882 is connected to a respective RF transmission line 884 that connects the feed point 882 to a respective pad 886. The radiating element 820 is mounted on the pad 886 such that the first feed point 886 is electrically connected to the first radiator 822 via a first RF transmission line 884 and the first pad 886, and the second feed point 886 is electrically connected to the second radiator 824 via a second RF transmission line 884 and the second pad 886. The first and second directional couplers 862 are provided in the form of respective transmission line traces 863, the transmission line traces 863 extending parallel to the first and second RF transmission lines 884, the transmission line traces 863 tapping RF energy from the respective first and second transmission lines 884. A first end of each RF transmission line trace 863 is terminated to a resistor 888, and a second end of each RF transmission line 863 is coupled to an input of a power combiner 866 (e.g., a wilkinson power combiner). The output 868 of the power combiner 866 is routed over an opening 890 in the ground plane on the back side of the feed plate 813. The backplate 802 has an opening 806 therein which is located behind an opening 890 in the ground plane of the feed plate 813. The calibration circuit board 850 is positioned behind the backplate 802. The calibration circuit board 850 may include conductive structures 852 such as, for example, conductive pads directly behind the openings 806 in the backplate 802. RF energy present at the output 868 of the power combiner 866 may thus be electromagnetically coupled to the conductive structure 852 through the opening 806 in the backplate 802. The arrangement shown in fig. 14 exists with respect to each of the four feed plates 813 such that RF energy is coupled to four separate conductive structures 852 on the calibration circuit board 850. First through third 2x1 directional couplers (not shown) may be provided on the calibration circuit board 850. Four conductive structures 852 on calibration circuit board 850 may be coupled to respective inputs of the first and second 2x1 directional couplers, and outputs of the first and second 2x1 directional couplers may be coupled to an input of the third 2x1 directional coupler to combine four calibration signals electromagnetically coupled from four respective feed boards 813 to conductive structures 852 on calibration circuit board 850. The output of the third 2x1 directional coupler may be coupled to a mount that receives the calibration cable 880.

It should be appreciated that the directional coupler of the calibration circuit may also be located on other printed circuit boards included in the base station antenna. For example, some base station antennas include a diplexer for combining RF signals traveling along a transmit path such that the combined signals can be transmitted through a so-called "wideband" radiating element, and the diplexer is used to separate received RF signals within different frequency bands so that the received signals can be passed to an appropriate receiver. In some cases, these diplexers are implemented on a printed circuit board. In other embodiments of the invention, the directional coupler of the calibration circuit may be implemented on a diplexer printed circuit board, rather than on a feed board printed circuit board or a phase shifter printed circuit board. The diplexer may be located at any conventional location along the RF path, including between the RF port and the phase shifter or between the phase shifter and the radiating element. The combiner circuit may be implemented on a separate calibration circuit board, partially on a diplexer printed circuit board and a calibration circuit board, or on a common printed circuit board that includes the diplexer, the directional coupler of the calibration circuit, and the combiner of the calibration circuit.

As another example, some base station antennas are designed with a fixed downtilt angle (or no downtilt angle) rather than a variable downtilt angle that can be adjusted using an electromechanical phase shifter. These fixed tilted antennas typically have a power splitter printed circuit board for splitting the RF signal to be transmitted into multiple sub-RF components. These power splitter printed circuit boards perform the power splitting functions (as described above) performed by the electromechanical phase shifters included in the base station antennas according to various embodiments of the present invention, without performing variable phase delays. It should be appreciated that the directional coupler may also be implemented on a power splitter printed circuit board included in such an antenna in the same manner as the directional coupler implemented on the main printed circuit board of the phase shifter in the base station antenna discussed above with reference to fig. 10-12.

Fig. 15 is a schematic plan view of a portion of a base station antenna 900 including four phase shifters 910 mounted on a metal support plate 912. Fig. 15 shows how calibration couplers 940 may be formed, for example, on the main printed circuit board 920 of each phase shifter 910, the calibration couplers 940 electromagnetically extract calibration signals and pass these extracted calibration signals to a calibration circuit board 950 that includes a calibration combiner circuit.

As shown in fig. 15, each phase shifter 910 may include a main printed circuit board 920 and a wiper printed circuit board 930. Each phase shifter 910 may be identical to one of the phase shifters 670 shown in fig. 12, except how the calibration coupler is implemented. As shown in fig. 15, the main printed circuit board 920 of each phase shifter 910 includes an input RF transmission line 922 (which may be the same as the input RF transmission line 716 of the phase shifter 670 of fig. 12) and an output RF transmission line 924 (which may be the same as the output RF transmission line 718 of the phase shifter 670 of fig. 12). Calibration coupler 940 is implemented along output RF transmission lines 924 of each phase shifter 910 using electromagnetic coupling through openings in the metal plate in a manner similar to that shown in fig. 14. In particular, as shown in fig. 15, calibration couplers 940 may be formed on each phase shifter 910 by forming openings 942 in the ground plane of each main printed circuit board 920, for example, below the corresponding output RF transmission line 924. The calibration circuit board 950 may be mounted under the phase shifter 910 and under the metal plate 912. A corresponding opening (not separately shown in fig. 15, but identical in position and shape to the corresponding opening 942) is formed in the metal plate 912 below the corresponding opening 942 in the ground plane of the main printed circuit board 920 of the corresponding phase shifter 910. Conductive pads 944 may be formed on the calibration circuit board 950 directly below the corresponding openings 914 in the metal plate 912. RF energy transferred along each output transmission line 924 may be electromagnetically coupled to the conductive pad 944 through a respective opening 942 in the ground plane, through a respective opening in the metal plate 912. In other words, the combination of the opening 942 in the ground plane, the opening in the metal plate 912, and the conductive pad 944 can be used to implement a calibration coupler 940, which calibration coupler 940 couples RF energy from the corresponding output transmission line 924 to the conductive pad 944.

As further shown in fig. 15, calibration circuit board 950 may include calibration combiners 952-1 through 952-3. Calibration combiner 952-1 may be coupled to a first pair of conductive pads 944 by RF transmission line 954 to combine calibration signals coupled to those pads 944, while calibration combiner 952-2 may be similarly coupled to a second pair of conductive pads 944 by RF transmission line 954 to combine calibration signals coupled to those pads 944. An additional RF transmission line 954 may be provided on the calibration circuit board 950 for coupling the outputs of the calibration combiners 952-1 and 952-2 to a third calibration combiner 952-3 that outputs a combined calibration signal. Thus, fig. 15 illustrates how the electromagnetic coupling techniques discussed above with reference to, for example, fig. 7-9 and 13-14 may also be used to couple base station antennas from calibration circuits of a phase shifter printed circuit board.

In the above described exemplary embodiment, each antenna comprises four columns of dual polarized radiating elements, wherein each feed plate (except for the feed plate 313 comprising eight radiating elements) provides two radiating elements, for a total of six radiating elements per column. However, it will be appreciated that other numbers of columns and/or radiating elements may be included in the antenna, and that the number of radiating elements per feed plate may vary (e.g., one radiating element or three radiating elements are typically included on a feed plate), and that different feed plates may have different numbers of radiating elements, according to embodiments of the present invention. It will thus be appreciated that the above-described embodiments are exemplary in nature and are not intended to limit the scope of the invention, but simply illustrate several different exemplary ways in which the calibration circuit may be implemented along an electrical path connecting the phase shifter to the radiating element to provide a lower cost and/or improved performance antenna.

The invention is 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 the art. In the drawings, like numbers refer to like elements throughout. The thickness and size of some of the elements may not be proportional.

Spatially relative terms, such as "under", "below", "lower", "above", "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 or feature as illustrated. 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 "below" or "beneath" other elements or features would then be oriented "over" the other elements or features. Thus, the exemplary term "under" may encompass both an orientation of above and below. 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 should be appreciated that features illustrated with the above one example embodiment may be incorporated into any other example embodiment. Thus, it will be appreciated that the disclosed embodiments can be combined in any manner to provide many additional embodiments.

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 element. 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.

Claims (23)

1. A base station antenna, comprising:

a back plate;

a plurality of radiating elements including at least a first radiating element and a second radiating element, each radiating element extending forward from the back plate;

a plurality of feed plates including at least a first feed plate and a second feed plate, wherein each feed plate has a respective set of one or more radiating elements mounted thereon;

Calibrating the port; and

a calibration circuit, the calibration circuit comprising:

a calibration combiner having an output coupled to the calibration port; and

a plurality of directional couplers including at least a first directional coupler and a second directional coupler, the first directional coupler and the second directional coupler coupled to the calibration combiner,

wherein at least a first portion of the first directional coupler is implemented on the first feed plate,

wherein the first radiating element is mounted on the first feed plate and comprises a dual polarized radiating element comprising a first radiator radiating with a first polarization and a second radiator radiating with a second polarization different from the first polarization, and wherein the first directional coupler is coupled to the first radiator and the second directional coupler is coupled to the second radiator,

wherein the first directional coupler and the second directional coupler are implemented entirely on the first feed plate, and the first feed plate further comprises a combiner coupled to a tap port of the first directional coupler and a tap port of the second directional coupler, wherein the combiner comprises a portion of the calibration combiner, and

Wherein another portion of the calibration combiner is located on a calibration circuit board separate from the first feed board.

2. The base station antenna of claim 1, wherein the first radiating element is in a first column of the plurality of columns and the second radiating element is in a second column of the plurality of columns horizontally spaced apart from the first column, and wherein the first directional coupler is configured to couple radio frequency energy from a transmission line connected to the first radiating element and the second directional coupler is configured to couple radio frequency energy from a transmission line connected to the second radiating element.

3. A base station antenna, comprising:

a back plate;

a plurality of radiating elements including at least a first radiating element and a second radiating element, each radiating element extending forward from the back plate;

a plurality of feed plates including at least a first feed plate and a second feed plate, wherein each feed plate has a respective set of one or more radiating elements mounted thereon;

calibrating the port; and

a calibration circuit, the calibration circuit comprising:

a calibration combiner having an output coupled to the calibration port; and

A plurality of directional couplers including at least a first directional coupler and a second directional coupler, the first directional coupler and the second directional coupler coupled to the calibration combiner,

wherein at least a first portion of the first directional coupler is implemented on the first feed plate,

a first radio frequency port; and

a first electro-mechanical phase shifter coupled between the first radio frequency port and the first radiating element,

wherein the first directional coupler is configured to couple radio frequency energy from a first transmission path extending from the first output of the first electro-mechanical phase shifter to the first radiating element,

wherein the radiating elements are arranged in a plurality of columns.

4. A base station antenna according to claim 3, wherein the first output of the first electromechanical phase shifter comprises an output that is not subject to an adjustable phase shift.

5. A base station antenna, comprising:

a back plate;

a first plurality of radiating elements arranged to define a first column of radiating elements;

a second plurality of radiating elements arranged to define a second column of radiating elements;

A first radio frequency port;

a second radio frequency port;

a first electromechanical phase shifter electrically coupled between the first radio frequency port and the first column of radiating elements;

a second electromechanical phase shifter electrically coupled between the second radio frequency port and the second column of radiating elements; and

a calibration circuit, the calibration circuit comprising:

a first directional coupler coupled along a first radio frequency transmission path extending between an input of the first electro-mechanical phase shifter and a first one of the radiating elements in the first column of radiating elements; and

a second directional coupler coupled along a second radio frequency transmission path extending between an input of the second electro-mechanical phase shifter and a first one of the radiating elements in the second column of radiating elements,

wherein the calibration circuit further comprises a combiner configured to combine radio frequency energy present on a tap port of the first directional coupler with radio frequency energy present on a tap port of the second directional coupler, wherein an output of the combiner is coupled to a calibration port of the base station antenna,

Wherein the first one of the radiating elements in the first column of radiating elements is mounted to extend forward from a first feed plate and the first one of the radiating elements in the second column of radiating elements is mounted to extend forward from a second feed plate, and wherein a first directional coupler is at least partially implemented on the first feed plate and the second directional coupler is at least partially implemented on the second feed plate.

6. The base station antenna of claim 5, wherein the first one of the radiating elements in the first column of radiating elements is a dual-polarized radiating element comprising a first radiator coupled to the first radio frequency transmission path and radiating at a first polarization and a second radiator coupled to a third radio frequency transmission path and radiating at a second polarization different from the first polarization.

7. The base station antenna of claim 5, wherein the combiner is implemented on a calibration circuit board.

8. The base station antenna of claim 5, wherein the first and second feed plates are mounted in front of the back plate and the calibration circuit board is mounted behind the back plate.

9. The base station antenna of claim 5, wherein the first radiating element of the first column of radiating elements is mounted to extend forward from a first feed plate, and wherein the first directional coupler includes a first portion that is part of the first feed plate and a second portion that is part of a calibration circuit board.

10. The base station antenna of claim 9, wherein the first feed board is on a first side of the back plane and the calibration circuit board is on a second side of the back plane opposite the first side.

11. A base station antenna, comprising:

a back plate;

a first plurality of radiating elements arranged to define a first column of radiating elements;

a second plurality of radiating elements arranged to define a second column of radiating elements;

a plurality of feed plates, wherein each feed plate has a respective set of one or more radiating elements mounted thereon;

a first radio frequency port;

a second radio frequency port;

a first electromechanical phase shifter electrically coupled between the first radio frequency port and the first column of radiating elements;

A second electromechanical phase shifter electrically coupled between the second radio frequency port and the second column of radiating elements; and

a calibration circuit, the calibration circuit comprising:

a first directional coupler coupled along a first radio frequency transmission path extending between an input of the first electro-mechanical phase shifter and a first one of the radiating elements in the first column of radiating elements; and

a second directional coupler coupled along a second radio frequency transmission path extending between an input of the second electro-mechanical phase shifter and a first one of the radiating elements in the second column of radiating elements,

the first directional coupler is implemented on a printed circuit board of the first electromechanical phase shifter.

12. The base station antenna of claim 11, wherein the first directional coupler is implemented along an input radio frequency transmission line on the printed circuit board of the first electromechanical phase shifter that connects an input port of the first electromechanical phase shifter to a power splitter included on the printed circuit board of the first electromechanical phase shifter.

13. The base station antenna of claim 11, wherein the first directional coupler is implemented along a radio frequency transmission line extending between a power splitter on a printed circuit board of the first electromechanical phase shifter and an output port of the first electromechanical phase shifter.

14. The base station antenna of claim 13, wherein the radio frequency transmission line extending between the power splitters on the printed circuit board of the first electromechanical phase shifter has a fixed length that is unaffected by variable phase shifts.

15. A base station antenna, comprising:

a back plate;

a first plurality of radiating elements arranged to define a first column of radiating elements;

a second plurality of radiating elements arranged to define a second column of radiating elements;

a plurality of feed plates, wherein each feed plate has a respective set of one or more radiating elements mounted thereon;

a first radio frequency port;

a second radio frequency port;

a first electromechanical phase shifter electrically coupled between the first radio frequency port and the first column of radiating elements;

a second electromechanical phase shifter electrically coupled between the second radio frequency port and the second column of radiating elements; and

A calibration circuit, the calibration circuit comprising:

a first directional coupler coupled along a first radio frequency transmission path extending between an input of the first electro-mechanical phase shifter and a first one of the radiating elements in the first column of radiating elements; and

a second directional coupler coupled along a second radio frequency transmission path extending between an input of the second electro-mechanical phase shifter and a first one of the radiating elements in the second column of radiating elements; and

a diplexer printed circuit board comprising at least one diplexer, wherein the first directional coupler is implemented on the diplexer printed circuit board.

16. A base station antenna, comprising:

a back plate having a front surface and a back surface;

a plurality of radiating elements extending forward from the back plate;

a plurality of feed plates mounted on the front of the back plate, each feed plate having a respective group of one or more of the plurality of radiating elements mounted thereon;

a calibration circuit comprising a plurality of components mounted in front of the back plate and at least one additional component mounted behind the back plate,

Wherein the plurality of components includes a first portion of a corresponding plurality of directional couplers.

17. The base station antenna of claim 16, wherein the at least one additional component comprises at least a portion of a calibration combiner.

18. The base station antenna of claim 16, wherein the plurality of components comprises a plurality of directional couplers.

19. The base station antenna of claim 18, wherein the plurality of components further comprises a plurality of 2x1 combiners.

20. The base station antenna of claim 16, wherein the calibration circuit is mounted on a calibration circuit board, and wherein the second portion of each of the directional couplers is implemented on the calibration circuit board.

21. The base station antenna of claim 16, wherein the back plate comprises an opening, and wherein the calibration circuit comprises a directional coupler configured to electromagnetically couple radio frequency energy through the opening.

22. A base station antenna, comprising:

a back plate;

a plurality of radio frequency ports including at least a first radio frequency port and a second radio frequency port;

a plurality of radiating elements including at least a first radiating element and a second radiating element, each of the radiating elements extending forward from the back plate;

A plurality of power splitters including at least a first power splitter and a second power splitter, the first power splitter coupled between the first radio frequency port and the first radiating element, and the second power splitter coupled between the second radio frequency port and the second radiating element;

calibrating the port; and

a calibration circuit, the calibration circuit comprising:

a calibration combiner having an output coupled to the calibration port; and

a plurality of directional couplers including at least a first directional coupler and a second directional coupler, the first directional coupler and the second directional coupler coupled to the calibration combiner,

wherein the first directional coupler is implemented on a printed circuit board of the first power splitter,

wherein the second directional coupler is implemented on a printed circuit board of the second power splitter,

wherein the first power divider is part of a first phase shifter and the second power divider is part of a second phase shifter,

wherein the first phase shifter comprises an input radio frequency transmission line, the first power divider, and a plurality of output radio frequency transmission lines, and wherein the first directional coupler is implemented along the input radio frequency transmission line.

23. A base station antenna, comprising:

a back plate;

a plurality of radio frequency ports including at least a first radio frequency port and a second radio frequency port;

a plurality of radiating elements including at least a first radiating element and a second radiating element, each of the radiating elements extending forward from the back plate;

a plurality of power splitters including at least a first power splitter and a second power splitter, the first power splitter coupled between the first radio frequency port and the first radiating element, and the second power splitter coupled between the second radio frequency port and the second radiating element;

calibrating the port; and

a calibration circuit, the calibration circuit comprising:

a calibration combiner having an output coupled to the calibration port; and

a plurality of directional couplers including at least a first directional coupler and a second directional coupler, the first directional coupler and the second directional coupler coupled to the calibration combiner,

wherein the first directional coupler is implemented on a printed circuit board of the first power splitter,

Wherein the second directional coupler is implemented on a printed circuit board of the second power splitter,

wherein the first power divider is part of a first phase shifter and the second power divider is part of a second phase shifter, and

wherein the first phase shifter comprises an input radio frequency transmission line, the first power divider and a plurality of output radio frequency transmission lines, and wherein the first directional coupler is implemented along one of the output radio frequency transmission lines, the one output radio frequency transmission line having a fixed length that is unaffected by the variable phase shift.

Images