Radiating elements for multiband base station antennas having cavity phase shifters and related linear array assemblies and base station antennas

Abstract

A radiating element comprises a feed stalk that comprises a metal ground stalk and a radiator assembly. The metal ground stalk has a base and a distal end that are spaced apart from each other in a first direction and a first signal trace that extends in the first direction adjacent the metal ground stalk. The radiator assembly is mounted adjacent the distal end of the metal ground stalk. The first signal trace comprises an output trace of a first phase shifter assembly and directly electrically connects to the radiator assembly.

Description

Attorney Docket No.9833.7492.WO RADIATING ELEMENTS FOR MULTIBAND BASE STATION ANTENNAS HAVING CAVITY PHASE SHIFTERS AND RELATED LINEAR ARRAY ASSEMBLIES AND BASE STATION ANTENNAS FIELD

[0001] The present application claims priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application Serial No.63 / 680,302, filed August 7, 2024, the entire content of which is incorporated herein by reference as if set forth in its entirety. FIELD

[0002] The present disclosure relates to communications systems and, in particular, to base station antennas for cellular communications systems. BACKGROUND

[0003] Cellular communications systems are well known in the art. In a cellular communications system, a geographic area is divided into a series of regions that are referred to as "cells" which are served by respective base stations. Each base station may include one or more base station antennas that are configured to provide two-way radio frequency ("RF") communications with mobile subscribers that are within the cell served by the base station. Typically, the base station antennas are mounted on a tower or other raised structure, with the radiation patterns (also referred to herein as "antenna beams") that are generated by the base station antennas directed outwardly.

[0004] A common base station configuration is the three sector configuration in which a cell is divided into three 120º "sectors" in the azimuth (horizontal) plane. A separate base station antenna provides coverage (service) to each sector. Typically, each base station antenna will include multiple vertically-extending columns of radiating elements that operate, for example, using second generation ("2G"), third generation ("3G") or fourth generation ("4G") cellular network protocols. These vertically-extending columns of radiating elements areAttorney Docket No.9833.7492.WO typically referred to as "linear arrays," and may be straight columns of radiating elements or columns in which some of the radiating elements are staggered horizontally to narrow the beamwidths of the generated antenna beams in the azimuth (horizontal) plane. Most modern base station antennas include both "low-band" linear arrays of radiating elements that support service in some or all of the 617-960 MHz frequency band and "mid-band" linear arrays of radiating elements that support service in some or all of the 1427-2690 MHz frequency band. These linear arrays are typically formed using dual-polarized radiating elements, which allows each linear array to be connected to a pair of radio ports so that the linear array can simultaneously transmit and receive first and second RF signals at first and second orthogonal polarizations (i.e., an antenna beam is generated at each orthogonal polarization).

[0005] Each of the above-described linear arrays of dual-polarized radiating elements is coupled to two radio ports (one port for each polarization). An RF signal that is to be transmitted by one of the linear arrays is passed from the radio port to the antenna where it is divided into a plurality of sub-components, with each sub-component fed to a respective subset of the radiating elements in the linear array (typically each sub-component is fed to between one and three radiating elements). The sub-components of the RF signal are transmitted through the radiating elements to generate an antenna beam that covers a generally fixed coverage area, such as a 120⁰ sector of a cell. Typically these linear arrays will have remote electronic tilt ("RET") capabilities which allow a cellular operator to change, from a control center, the pointing angle of the generated antenna beams in the elevation (vertical) plane in order to change the size of the sector served by the linear array (since the more that the antenna beam is downtilted in the elevation plane, the smaller the area that is illuminated by the antenna beam, and hence the smaller the size of the area covered by the antenna beam). Since the antenna beams generated by the above-described 2G / 3G / 4G linear arrays are static antenna beams that only change in shape due to adjustments in the downtilt angle of the antenna beam, they are often referred to as "passive" linear arrays.

[0006] Cellular operators are currently upgrading their networks to support fifth generation ("5G") cellular service. One important component of 5G cellular service is the use of multi-column "active" beamforming arrays that operate in conjunction with beamforming radios. The beamforming radios can generate a plurality of sub-components of an RF signal where the amplitudes and / or phases of each sub-component is set in a desired fashion so that the size, shapeAttorney Docket No.9833.7492.WO and pointing direction of the antenna beam generated by the sub-components of the RF signal are controlled in desirable ways. The sub-components of the signal are passed to respective subsets of the radiating elements of the active beamforming array in order to generate an antenna beam having a desired size, shape and pointing direction. These active beamforming arrays are typically formed using "high-band" radiating elements that operate in higher frequency bands, such as some or all of the 3.3-4.2 GHz frequency bands, although active beamforming radios may also be provided that operate in other frequency bands such as the upper portion (e.g., 2.5- 2.7 GHz) of the mid-band frequency range. The radiating elements in each vertically-extending column of such an active beamforming array are typically coupled to a respective port of a beamforming radio so that each column of radiating elements is fed a different sub-component of an RF signal to be transmitted. The beamforming radio may be a separate device, or may be integrated with the active antenna array. As discussed above, the beamforming radio may adjust the amplitudes and phases of the sub-components of an RF signal that are fed to each port of the radio (and hence to each respective column of radiating elements in the multi-column beamforming array) in order to generate antenna beams that have narrowed beamwidths in the azimuth plane (and hence higher antenna gain). These narrowed antenna beams can be electronically steered throughout the sector by proper selection of the amplitudes and phases of the sub-components of the RF signal. In order to avoid having to increase the number of antennas at cell sites, 5G antennas that include such beamforming arrays also often include passive linear arrays that support legacy 2G, 3G and / or 4G cellular services. SUMMARY

[0007] Pursuant to some embodiments of the present invention, radiating elements for a base station antenna are provided that comprise a feed stalk that comprises a metal ground stalk that has a base and a distal end that are spaced apart from each other in a first direction and a first signal trace extending in the first direction adjacent the metal ground stalk and a radiator assembly that is mounted adjacent the distal end of the metal ground stalk. The first signal trace comprises an output trace of a first phase shifter assembly and directly electrically connects to the radiator assembly.

[0008] In some embodiments, the metal ground stalk comprises a first plate that has a longitudinal axis that extends in the first direction and a second plate that is at the base of the metal ground stalk, the second plate having a major surface that extends in a second directionAttorney Docket No.9833.7492.WO and a third direction that are perpendicular to each other and to the first direction. In some embodiments, the metal ground stalk further comprises a third plate that extends in the second direction and the third direction. In some embodiments, the third plate is at the distal end of the metal ground stalk.

[0009] In some embodiments, the metal ground stalk comprises a first metal piece and a second metal piece, and wherein the first, second and third metal plates are each part of the first metal piece, the first metal piece further comprising a fourth plate that extends in the first direction and a fifth plate that extends in the second direction and the third direction, where the fifth plate is coplanar with the third plate. In some embodiments, the second metal piece comprises a sixth plate and a ninth plate that each have a longitudinal axis that extends in the first direction, a seventh plate that extends in the second direction and the third direction at the base of the metal ground stalk, and an eighth plate and a tenth plate that each extend in the second direction and the third direction. In some embodiments, the eighth plate and the tenth plate are coplanar with the third plate and the fifth plate. In some embodiments, the radiating element further comprises a second signal trace extending in the first direction adjacent the metal ground stalk to directly electrically connect to the radiator assembly, where the second signal trace comprises an output trace of a second phase shifter assembly. In some embodiments, the first signal trace extends through at least a first opening in the first metal piece and the second signal trace extends through at least a first opening in the second metal piece. In some embodiments, the first plate extends in a first plane and the fourth plate extends in a second plane that is perpendicular to the first plane.

[0010] In some embodiments, the third plate, the fifth plate, the eighth plate and the tenth plate each extend in a third plane. In some embodiments, the second plate and the seventh plate each extend in a fourth plane that is parallel to the third plane. In some embodiments, the sixth plate extends in a fifth plane that is perpendicular to the first plane.

[0011] In some embodiments, the radiator assembly comprises a first printed circuit board that is galvanically coupled to the first signal trace. In some embodiments, the radiator assembly further comprises a second printed circuit board that includes a plurality of metal pads that are capacitively coupled to the metal ground stalk. In some embodiments, the radiator assembly further comprises a plurality of sheet metal dipole arm pieces that are capacitivelyAttorney Docket No.9833.7492.WO coupled to the respective metal pads on the second printed circuit board. In some embodiments, the first printed circuit board is mounted forwardly of the second printed circuit board.

[0012] In some embodiments, the first phase shifter assembly is at least partially mounted within a metal housing that has a front wall, and wherein the first signal trace extends through an opening in the front wall. In some embodiments, a rear of the metal housing is at least partially open to allow a printed circuit board of the phase shifter assembly to be inserted into the metal housing from the rear.

[0013] In some embodiments, the radiating element is part of a base station antenna that comprises a reflector that includes an opening that is larger than a footprint of the metal ground stalk.

[0014] Pursuant to further embodiments of the present invention, radiating elements are provided that comprise a feed stalk that includes a metal ground stalk that has a base and a distal end that are spaced apart from each other in a first direction and a first signal trace extending in the first direction adjacent the metal ground stalk. These radiating elements further comprise a radiator assembly that includes a first printed circuit board that is mounted forwardly of the metal ground stalk, a second printed circuit board, and a first sheet metal dipole arm piece.

[0015] In some embodiments, the first printed circuit board is mounted on the first signal trace.

[0016] In some embodiments, the first signal trace is soldered to a first metal structure on the first printed circuit board.

[0017] In some embodiments, the metal ground stalk is capacitively coupled to a first metal pad on the second printed circuit board.

[0018] In some embodiments, the radiator assembly further comprises a second sheet metal dipole arm piece, a third sheet metal dipole arm piece and a fourth sheet metal dipole arm piece, and the second printed circuit board further comprises a second metal pad, a third metal pad and a fourth metal pad, and wherein the first through fourth sheet metal dipole arm pieces are capacitively couped to the respective first through fourth metal pads.

[0019] In some embodiments, the metal ground stalk comprises a first plate that has a longitudinal axis that extends in the first direction and a second plate that is at the base of the metal ground stalk, the second plate extending in a second direction and a third direction that are perpendicular to each other and to the first direction. In some embodiments, the metal groundAttorney Docket No.9833.7492.WO stalk further comprises a third plate that extends in the second direction and the third direction. In some embodiments, the metal ground stalk comprises a first metal piece and a second metal piece, and wherein the first, second and third metal plates are each part of the first metal piece, the first metal piece further comprising a fourth plate that extends in the first direction and a fifth plate that is coplanar with the third metal plate.

[0020] In some embodiments, the second metal piece comprises a sixth plate and a ninth plate that each have a longitudinal axis that extends in the first direction, a seventh plate that extends in the second direction and the third direction at the base of the metal ground stalk, and an eighth plate and a tenth plate that are coplanar with the third metal plate and the fifth metal plate. In some embodiments, the radiating element further comprises a second signal trace extending in the first direction adjacent the metal ground stalk to directly electrically connect to the radiator assembly, where the second signal trace comprises an output trace of a second phase shifter assembly. In some embodiments, the first signal trace extends through at least a first opening in the first metal piece and the second signal trace extends through at least a first opening in the second metal piece.

[0021] In some embodiments, the first plate extends in a first plane and the fourth plate extends in a second plane that is perpendicular to the first plane. In some embodiments, the third plate, the fifth plate, the eighth plate and the tenth plate each extend in a third plane. In some embodiments, the first signal trace comprises an output trace of a first phase shifter assembly and directly electrically connects to the radiator assembly.

[0022] Pursuant to further embodiments of the present invention, radiating elements for a base station antenna are provided that comprise a first monolithic sheet metal piece that includes first and second ground plates and first and second dipole arms extending from distal ends of the first and second ground plates and a second monolithic sheet metal piece that includes third and fourth ground plates and third and fourth dipole arms extending from distal ends of the third and fourth ground plates. The first and second dipole arms form a first dipole radiator and the third and fourth dipole arms form a second dipole radiator.

[0023] In some embodiments, the radiating element further comprises a first signal trace mounted adjacent the first ground plate and a second signal trace mounted adjacent the third ground plate. The radiating element may further comprise a first printed circuit board that is mounted on the first and second signal traces. In some embodiments, the first printed circuitAttorney Docket No.9833.7492.WO board is mounted forwardly of the first and second dipole radiators. In some embodiments, the radiating element may further comprise a parasitic metal element mounted forwardly of the first printed circuit board. The parasitic metal element may comprise a parasitic metal ring. In some embodiments, the parasitic metal ring may be capacitively coupled to the first through fourth dipole arms.

[0024] The radiating may also comprise a director mounted forwardly of the parasitic metal element and / or a meta director, which may be mounted forwardly of the director. In some embodiments, the meta director comprises a printed circuit board that comprises a plurality of unit cell metal structures.

[0025] In some embodiments, the radiating element may further comprise a first printed circuit board, wherein the first signal trace is electrically connected to a first metal structure on the first printed circuit board and the second signal trace is electrically connected to a second metal structure on the first printed circuit board.

[0026] In some embodiments, the first signal trace comprises an output trace of a first phase shifter assembly and directly electrically connects to the first printed circuit board.

[0027] In some embodiments, the radiating element may further comprise a parasitic metal element that is configured to capacitively couple with the first through fourth dipole arms. In some embodiments, the parasitic metal element may comprise a metal ring having first through fourth metal plates extending radially inwardly from the metal ring. In other embodiments, the parasitic metal element may comprise a metal ring having fifth through eighth metal plates extending outwardly from the metal ring. In some embodiments, the fifth through eighth metal plates extend rearwardly from the metal ring. In some embodiments, the first through fourth dipole arms extend radially outwardly from a central point and have respective longitudinal axes that extend at angles of 45⁰, 135⁰, 225⁰ and 315⁰, and the fifth through eighth metal pads extend radially outwardly from the respective first through fourth metal plates.

[0028] In some embodiments, the first ground plate extends in a first plane and the second ground plate extends in a second plane that is perpendicular to the first plane.

[0029] In some embodiments, the first signal trace comprises an output trace of a first phase shifter assembly and the second signal trace comprises an output trace of a second phase shifter. In some embodiments, the radiating element may further comprise a first printed circuit board, wherein the first signal trace is galvanically connected to a first metal structure on the firstAttorney Docket No.9833.7492.WO printed circuit board and the second signal trace is galvanically connected to a second metal structure on the first printed circuit board. In some embodiments, the radiating element may further comprise a parasitic metal element that is configured to capacitively couple with the first through fourth dipole arms.

[0030] In some embodiments, the first printed circuit board is positioned forwardly of the first and second dipole radiators and rearwardly of the parasitic metal element. In some embodiments, the parasitic metal element comprises a metal ring having first through fourth metal plates extending radially inwardly from the metal ring.

[0031] In some embodiments, the radiating element is provided in combination with a base station antenna that includes a reflector having an opening that is aligned with the radiating element, wherein the opening is larger than a footprint of the first and second dipole radiators, the radiating element further comprising a parasitic metal element that is configured to capacitively couple with the first and second dipole radiators, wherein a footprint of the parasitic metal element is larger than the opening.

[0032] Pursuant to additional embodiments of the present invention, cavity phase shifters are provided that comprise a monolithic metal housing that comprises a front wall and first and second sidewalls that extend rearwardly from the front wall, the front wall and the first and second side walls defining a first cavity and a phase shifter assembly at least partly mounted in the first cavity. A rear side of the first cavity is at least partially open.

[0033] In some embodiments, the phase shifter assembly is configured to be inserted into the first cavity from the rear side of the first cavity.

[0034] In some embodiments, the front wall includes a plurality of openings, and forwardly extending output traces of the phase shifter assembly are configured to be inserted through the respective openings when the phase shifter assembly is mounted in the first cavity.

[0035] In some embodiments, a rear side of the first cavity is fully open.

[0036] In some embodiments, the first sidewall includes an inwardly extending lip that partially encloses the rear side of the first cavity. In some embodiments, the second sidewall includes an inwardly extending lip, and a slot is defined in between the first and second inwardly extending lips.

[0037] In some embodiments, the first cavity has first and second open ends.Attorney Docket No.9833.7492.WO

[0038] In some embodiments, the phase shifter assembly comprises a main phase shifter printed circuit board, and portions of each output trace that extend through the respective openings each have a length in the forward direction that is at least one-quarter of a length of the first sidewall in the forward direction. In some embodiments, portions of each output trace that extend through the respective openings each have a length in the forward direction that is at least one-third of the length of the first sidewall in the forward direction.

[0039] In some embodiments, the cavity phase shifter is provided in combination with a plurality of radiating elements, where each output trace comprises a signal trace of a respective one of the radiating elements. In some embodiments, each radiating element includes a radiator assembly, and each output trace is directly electrically connected to the radiator assembly. In some embodiments, each radiator assembly includes a printed circuit board, and each output trace is soldered to a respective metal structure on the respective printed circuit boards.

[0040] Pursuant to still further embodiments of the present invention, cavity phase shifter assemblies are provided that comprise a longitudinally-extending monolithic metal housing that defines a first cavity that has longitudinally-extending first and second sidewalls and a phase shifter that comprises a main printed circuit board. A rear of the first cavity includes a longitudinally-extending opening that is configured to receive the main printed circuit board.

[0041] In some embodiments, the main printed circuit board includes a plurality of forwardly-extending output traces.

[0042] In some embodiments, the monolithic metal housing includes a front wall and the first and second sidewalls extend rearwardly from the front wall, and wherein the front wall includes a plurality of openings and the forwardly-extending output traces extend through the respective openings.

[0043] In some embodiments, portions of each output trace that extend through the respective openings each have a length in the forward direction that is at least one-quarter of a length of the first sidewall in the forward direction.

[0044] In some embodiments, the cavity phase shifter is provided in combination with a plurality of radiating elements, wherein each output trace comprises a signal trace of a respective one of the radiating elements. In some embodiments, each radiating element includes a radiator assembly, and each output trace is directly electrically connected to the radiator assembly. InAttorney Docket No.9833.7492.WO some embodiments, each radiator assembly includes a printed circuit board, and each output trace is soldered to a respective metal structure on the respective printed circuit boards. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG.1A is a front perspective view of a conventional base station antenna that includes both passive 2G / 3G / 4G linear arrays and an active beamforming array.

[0046] FIG.1B is a schematic front view of the conventional base station antenna of FIG.1A with the radome removed.

[0047] FIG.2A is a schematic front view of a base station antenna according to embodiments of the present invention with the radome removed.

[0048] FIG.2B is a schematic exploded front perspective view of four mid-band linear array assemblies of the base station antenna of FIG.2A, with a main reflector of the base station antenna shown for context.

[0049] FIG.3A is a schematic side perspective view of one of the mid-band radiating elements included in the mid-band linear array assemblies of FIG.2B.

[0050] FIG.3B is an exploded perspective version of FIG.3A.

[0051] FIG.3C is a schematic perspective view of a metal ground stalk of the mid-band radiating element of FIGS.3A-3B.

[0052] FIG.3D is a front view of a radiator assembly of the mid-band radiating element of FIGS.3A-3C.

[0053] FIG.3E is an enlarged plan view of the mid-band radiating element of FIGS.3A- 3B that illustrates one example implementation of a parallel LC circuit that is used to move a common mode resonance of the mid-band radiating element out of the low-band operating frequency range.

[0054] FIG.4A is a schematic perspective view of the portion of FIG.2B contained in the box labelled 4A.

[0055] FIG.4B is a cross-sectional view taken along line 4B—4B of FIG.4A.

[0056] FIG.4C is a plan view of a main printed circuit board of one of the phase shifter assemblies included in the mid-band linear array assemblies of FIG.2B.

[0057] FIG.5 is a schematic perspective view of an alternative metal ground stalk that can be used on place of the metal ground stalk of FIG.3C.Attorney Docket No.9833.7492.WO

[0058] FIG.6 is a schematic side perspective view of the portion of FIG.2B contained in the box labelled 4A with an alternative mid-band radiating element mounted on the cavity phase shifter assembly.

[0059] FIG.7 is a schematic end view of an alternative metal housing for the cavity phase shifters according to further embodiments of the present invention.

[0060] FIG.8 is a schematic end view of a second alternative metal housing for the cavity phase shifters according to still further embodiments of the present invention

[0061] It should be noted that herein reference numerals that include two numbers separated by a dash may be used, and that like elements may be referred to individually by their full reference numeral and may be referred to collectively by the first part of their reference numeral. DETAILED DESCRIPTION

[0062] FIGS.1A and 1B illustrate a conventional base station antenna 1 that includes both passive low-band and mid-band linear arrays and a high-band active beamforming array. In particular, FIG.1A is a front perspective view of the base station antenna 1, and FIG.1B is a schematic front view of the base station antenna 1 with the radome thereof removed. In FIGS. 1A and 1B, the axes illustrate the vertical (V), horizontal (H) and forward (F) directions of the base station antenna system 1. In the description that follows, each antenna will be described using terms that assume that the antenna is mounted for use on a tower with the longitudinal axis L of the antenna extending along the vertical axis V and the front surface of the antenna mounted opposite the tower pointing toward the coverage area for the antenna.

[0063] Referring to FIG.1A, the base station antenna 1 has a tubular shape with a generally rectangular cross-section. The base station antenna 1 includes a radome 2 a top end cap 4 and a bottom end cap 6. A plurality of RF ports 8 in the form of RF connectors are mounted in the bottom end cap 6. The RF ports 8 extend through the bottom end cap 6 and are used to electrically connect the base station antenna 1 to external radios (not shown). The radome 2, top end cap 4 and bottom cap 6 may form an external housing for the antenna 1. An antenna assembly (FIG.1B) is contained within the housing.

[0064] FIG.1B is a schematic front view of the antenna assembly that is contained within the housing of base station antenna 1. As shown in FIG.1B, the antenna assembly includes a reflector 10. The reflector 10 may serve as both a structural component for theAttorney Docket No.9833.7492.WO antenna assembly and as a ground plane and reflector for at least some of the radiating elements (discussed below) of antenna 1. The reflector 10 includes a generally flat metallic surface that extends in the longitudinal direction L of the antenna 1. Various mechanical and electronic components of base station antenna 1 (not shown) are mounted behind the reflector 10.

[0065] The antenna assembly further includes first and second low-band arrays 20-1, 20-2 of low-band radiating elements 22, first and second mid-band arrays 30-1, 30-2 of first mid- band radiating elements 32A, third through sixth mid-band arrays 30-3 through 30-6 of second mid-band radiating elements 32B, and a multi-column high-band array 40 of high-band radiating elements 42. The low-band arrays 20 and mid-band arrays 30 are each implemented as vertically-extending linear arrays of radiating elements. The low-band and mid-band linear arrays 20, 30 may support, for example, 2G, 3G and / or 4G cellular service. Each of the low- band and mid-band linear arrays 20, 30 are passive arrays that generate static antenna beams that provide coverage to a predefined coverage area (e.g., antenna beams that are each configured to cover a 120⁰ sector of a base station), with the only change to the coverage area occurring when the electronic downtilt angles of the generated antenna beams are adjusted (e.g., to change the size of the cell).

[0066] The high-band radiating elements 42 are mounted in four columns in the lower center portion of the reflector 10 to form the multi-column array 40. Each column of the multi- column array 40 may be coupled to a pair of ports (one for each polarization) of a beamforming radio so that the multi-column array 40 operates as an active beamforming array that generates narrowed antenna beams that can be steered in the azimuth plane throughout the coverage area.

[0067] The low-band radiating elements 22 are configured to transmit and receive signals in the 617-960 MHz frequency range or a portion thereof (e.g., the 696-960 MHz frequency band). The first mid-band radiating elements 32A are configured to transmit and receive signals in the 1427-2690 MHz frequency range or a portion thereof (e.g., the 1427-1710 MHz frequency band, the 1427-2200 MHz frequency band, etc.). The second mid-band radiating elements 32B are configured to transmit and receive signals in the 1695-2690 MHz frequency range or a portion thereof (e.g., the 1710-2200 MHz frequency band, the 2300-2690 MHz frequency band, etc.). The second mid-band radiating elements 32B may have a different design than the first mid-band radiating elements 32A. The high-band radiating elements 42 are configured to transmit and receive signals in the 3300-4200 MHz frequency range or a portionAttorney Docket No.9833.7492.WO thereof. The radiating elements 22, 32A, 32B, 42 are mounted to extend forwardly from the reflector 10.

[0068] The low-band and mid-band radiating elements 22, 32A, 32B may each be implemented as dual-polarized radiating elements that each include first and second radiators that are configured to transmit and receive RF energy at orthogonal polarizations. For example, the low-band and mid-band radiating elements 22, 32A, 32B may be implemented as slant - 45⁰ / +45⁰ cross-dipole radiating element that include a -45⁰ dipole radiator and a +45⁰ dipole radiator that are arranged to form a cross when the radiating elements 22, 32A, 32B are viewed from the front. The dipole radiators of each low-band and mid-band radiating element 22, 32A, 32B are mounted on a feed stalk (not visible in the figures) that passes RF signals between the dipole radiators and an associated feed network.

[0069] Since dual-polarized radiating elements are used, each of the low-band and mid- band linear arrays 20, 30 is connected to a pair of the RF ports 8. The first RF port 8 of each pair is connected to a first port of a passive (non-beamforming) radio (e.g., a remote radio head mounted on the antenna tower near the base station antenna 1), typically by a coaxial cable. A feed cable and a feed network connect the first RF port 8 to the first polarization radiators of the radiating elements 22, 32A, 32B in the respective linear arrays 20, 30. Similarly, the second RF port 8 of each pair is connected to a second port of the radio by a coaxial cable, and another feed cable and feed network connect the second RF port 8 to the second polarization radiators of the radiating elements 22, 32A, 32B in a respective one of the linear arrays 20, 30. RF signals that are to be transmitted by a selected one of the low-band and mid-band linear arrays 20, 30 are passed from the associated radio to one of the RF ports 8, and passed from the RF port 8 to the associated feed network. Each feed network may include a phase shifter assembly that includes a power divider that divides the RF signal into a plurality of sub-components that are fed to the respective first or second radiators of the radiating elements 22, 32A, 32B in the linear array 20, 30 so that the sub-components are radiated into free space. Accordingly, each linear array 20, 30 may be used to form a pair of antenna beams, namely an antenna beam for each of the two polarizations at which the dual-polarized radiating elements included in the respective array are designed to transmit and receive RF signals. Each linear array 20, 30 may be configured to provide service to a sector of a base station. For example, each linear array 20, 30 may beAttorney Docket No.9833.7492.WO configured to provide coverage to approximately 120º in the azimuth plane so that the base station antenna 1 may act as a sector antenna for a three-sector base station.

[0070] The high-band radiating elements 42 are also implemented as dual polarized slant -45⁰ / +45⁰ cross-dipole radiating elements. Each column of high-band radiating elements 42 is coupled to a pair of ports (one port for each polarization) of a beamforming radio (not shown) that may be, for example, mounted on the antenna tower adjacent the antenna 1. The beamforming radio is capable of electronically adjusting the amplitudes and / or phases of the subcomponents of an RF signal that are output to each column of high-band radiating elements 42 of the multi-column beamforming array 40.

[0071] As shown best in FIG.1B, the low-band radiating elements 22 may be mounted on low-band feed board printed circuit boards 24, the mid-band radiating elements 32A, 32B may be mounted on mid-band feed board printed circuit boards 34, and the high-band radiating elements 42 may be mounted on high-band feed board printed circuit boards 44. The feed board printed circuit boards 24, 34, 44 couple RF signals between groups of one to three radiating elements 22, 32A, 32B, 42 and phase shifter assemblies that are interposed between the RF ports 8 and the arrays 20, 30, 40. Cables (not shown) may be used to connect each feed board printed circuit board 24, 34, 44 to the phase shifter assemblies.

[0072] While the conventional base station antenna 1 of FIGS.1A-1B can support a wide range of communications services, in practice it can be difficult to manufacture. Cellular operators tend to have strict limitations on the acceptable physical sizes for various types of base station antennas, since the base station antennas are often mounted on tall antenna towers where they can be subject to very high wind loads. As the size of a base station antenna increases, wind-loading considerations can greatly increase the structural requirements for the antenna mounting hardware and the antenna tower, which can significantly increase the cost of implementing a base station. Thus cellular operators often place strict limits on the lengths, widths and / or depths of each type of base station antenna.

[0073] Multiband base station antennas that support cellular service in all three of the low-band, mid-band and high-band frequency ranges typically include at least eight columns of radiating elements, and often as many as twelve, sixteen or more columns of radiating elements. Because of the size constraints for the antenna, radiating elements that operate in different frequency bands are often in very close proximity within the antenna, which may cause theAttorney Docket No.9833.7492.WO radiating elements from adjacent arrays to interact with each other, typically in undesirable ways. In addition, the number of feed networks included in the base station antennas increases linearly with the number of arrays of radiating elements. These feed networks are typically mounted behind the linear arrays, and the cables, phase shifters and other elements of the various feed networks are often intertwined. Each base station antenna is typically tested after the antenna is assembled to identify problems such as passive intermodulation ("PIM") distortion sources (e.g., poorly formed solder joints or loose metal-to-metal connections that can generate unwanted RF noise), faulty connections, inoperable components (e.g., phase shifters, RET units, etc.) and the like. When an antenna fails one or more of these tests, it often is difficult to identify the source of the problem, let alone fix it, since it is difficult to access many of the components of the antenna (and in particular components that are behind the reflector) due to the crowded design. As a result, when problems are identified, the base station antenna system often must be partly or completely disassembled to identify and fix the problems. This can greatly increase production costs.

[0074] Another problem with current multiband base station antennas is that the RF paths to radiating elements of at least some of the low-band, mid-band and high-band arrays pass between the back side of the reflector and the front side of the reflector. For example, the feed network for a linear array is typically mounted behind the reflector, while the radiating elements for the linear array are mounted in front of the reflector. Cables (or other RF connections) that pass through the reflector connect the feed network to the radiating elements. Since the feed network and the radiating elements are on opposed sides of the reflector, the full linear array typically cannot be assembled in advance; instead the feed network is installed behind the reflector and the radiating elements are mounted in front of the reflector, and the cables connecting the two are soldered into place. As such, the RF performance of these arrays cannot be tested until the base station antenna is assembled. If problems are identified, the antenna then typically has to be disassembled to fix the problems.

[0075] Pursuant to embodiments of the present invention, multi-band base station antennas are provided that have low-cost, high performance radiating elements that have low interaction on arrays operating in other frequency bands. In the embodiments discussed below, these radiating elements are mid-band radiating elements, but it will be appreciated that the techniques disclosed herein may be used to form radiating elements that operate in otherAttorney Docket No.9833.7492.WO frequency bands. The radiating elements according to embodiments of the present invention may have a feed stalk that comprises, for example, a metal ground stalk that can be formed using stamped and bent sheet metal and first and second signal traces that each may comprise, for example, an output trace of a respective phase shifter assembly. The sheet metal ground stalks may be manufactured at very low cost and may have lower insertion loss than printed circuit board based feed stalks. Additionally, in some embodiments, these radiating elements may only require a total of two solder joints (which connect the first and second signal traces to a radiator assembly) to assemble the radiating element and to electrically connect each radiating element to a pair of phase shifter assemblies, whereas most conventional radiating elements have four solder joints that connect the feed stalk to the radiator assembly and an additional four solder joints that connect the feed stalk to the pair of phase shifter assemblies. This reduction in solder joints reduces manufacturing time and costs, reduces the amount of "rework" required after factory testing (since poor solder joints are a frequent manufacturing issue), and reduces a potential source of PIM distortion in the antenna.

[0076] The radiating elements according to embodiments of the present invention may include a first printed circuit board that is mounted on the first and second signal traces of the feed stalk. Each of the first and second signal traces may be galvanically connected to a respective metal structure on the first printed circuit board. In some embodiments, each radiating element may also include a second printed circuit board that is mounted on the feed stalk and capacitively coupled thereto. In these embodiments, a plurality of sheet metal dipole arms may be mounted on the second printed circuit board and capacitively coupled thereto.

[0077] In other embodiments, the radiating elements may include dipole arms that are integral with the ground stalk of the feed stalk. For example, the ground stalk may comprise a two piece sheet metal ground stalk, where each sheet metal piece includes half of the ground stalk and a pair of dipole arms. The feed stalk may further include first and second signal traces that form air microstrip transmission lines with respective plates of the metal ground stalk. Each radiating element may also include a first printed circuit board. The first printed circuit board may be mounted on the first and second signal traces and may be soldered in place to physically and electrically connect the first and second signal traces to the first printed circuit board. The radiating elements may further include a parasitic metal element such as a parasitic metal ring that may be mounted forwardly of the first printed circuit board. The parasitic metal ring mayAttorney Docket No.9833.7492.WO capacitively load the dipole arms in order to extend the bandwidth of the radiating element so that it may encompass the full 1427-2690 MHz frequency range. These radiating elements may optionally include a director and / or a meta director that narrow the beamwidth of the generated antenna beams.

[0078] As discussed above, the feed network for each linear array typically includes a pair of phase shifter assemblies. One type of phase shifter assembly that is receiving increased interest is the so-called wireless cavity phase shifter assembly. A "wireless" phase shifter assembly refers to a phase shifter assembly that has outputs that connect directly to the radiating elements of an associated linear array (or to feed board printed circuit boards for the radiating elements), thereby eliminating the need for coaxial "phase cables" that extend from the outputs of a conventional phase shifter assembly to the radiating elements (or feed board printed circuit boards) of the array. A "cavity" phase shifter assembly refers to a phase shifter assembly that is mounted within a grounded metal housing so that the RF transmission lines of the phase shifter operate as low-loss stripline transmission lines. Since wireless cavity phase shifters have low- loss transmission lines and eliminate the need for phase cables (and the associated solder joints that connect the cables to the radiating elements and the phase shifter), they can enhance the performance of a base station antenna while at the same time reducing the manufacturing cost thereof. The use of cavity phase shifter assemblies also increases the modularity of a base station antenna, making it easier to disassemble the antenna, if necessary, to correct defects identified during factory testing.

[0079] One difficulty with conventional wireless cavity phase shifter assemblies is that the cavity phase shifter assembly is mounted behind a main reflector of the base station antenna while the radiating elements are mounted forwardly of the reflector. Because of this design, the base station antenna typically needs to be mostly assembled before the linear array assemblies can be installed and tested. In contrast, the mid-band radiating elements according to embodiments of the present invention may be pre-assembled onto the cavity phase shifters and tested before the linear array assembly is installed in the base station antenna. Then, a small portion of each radiating element, which may be held in place by snap clips or the like, may be removed and the remainder of the linear array assembly may be installed into the base station antenna. Thereafter, the small portion of each radiating element that was removed may be reinstalled to complete the installation of the linear array assembly into the base station antenna.Attorney Docket No.9833.7492.WO This simplifies the manufacturing response, since the mid-band linear arrays with their associated feed networks may be pre-tested before being installed in the antenna (which makes any rework much easier) and because the mid-band linear array assemblies may be installed into the base station antenna in a mostly-assembled form.

[0080] As discussed above, the output traces of the phase shifter assemblies may act as the signal traces for each radiating element. As a result, it is possible to have the outputs of the phase shifter assemblies directly feed the radiator assemblies of the radiating elements. This arrangement eliminates the need for any soldered connections between the phase shifter assembly and the signal traces of the radiating elements, which simplifies the manufacturing process and reduces the number of solder joints required. This design, however, also results in each phase shifter having a plurality of relatively long, forwardly-extending output traces. Since customer requirements and cost considerations may strictly limit the depth of the cavity phase shifter assemblies, it may not be possible to install the phase shifter assemblies in the cavities of the metal housing due to the long forwardly-extending output traces if the cavities have a full front wall, a full rear wall and full side walls (along with open ends), as is conventional. To solve this problem, the rear wall of each cavity may be partially or fully omitted, allowing the phase shifter assembly (or at least the portion thereof that includes the output traces) to be inserted into the metal housing from the rear. The front wall of each cavity may include a plurality of openings, and the output traces may extend through these openings to form the signal traces for the radiating elements.

[0081] The base station antennas according to embodiments of the present invention may include a reflector that is mounted forwardly of the cavity phase shifter assemblies. The reflector may include a plurality of openings that are located at the respective positions where the mid- band radiating elements are to be mounted. Each opening may, for example, be slightly larger than the footprint of the feed stalks of the radiating elements so that the mid-band radiating elements may be mostly pre-assembled on the cavity phase shifter assemble, and the cavity phase shifter assembly may then be installed in the antenna so that the partially assembled radiating elements pass through the respective openings in the reflector. This process simplifies the manufacture of the base station antenna. Moreover, in some embodiments, the radiating elements may be fully assembled onto the cavity phase shifter assemblies before the cavity phase shifters are installed in the base station antenna so that the linear array assemblies may be testedAttorney Docket No.9833.7492.WO before the antenna is assembled. The radiating elements may then be partially disassembled so that the cavity phase shifters can be installed in the antenna, and then reassembled.

[0082] Another difficulty with multiband antennas is that RF radiation transmitted and received by a lower frequency band radiating element may generate common mode currents on a nearby higher frequency band radiating element, particularly in cases where the feed stalk and dipole arm of the higher frequency band radiating element have a combined length that is close to a quarter wavelength of the frequency of the lower frequency band RF radiation. Unfortunately, the mid-band operating frequency range encompasses frequencies that are about twice frequencies in the upper portion of the low-band operating frequency range. As such, the electrical length of the combination of the feed stalk and a dipole arm of most mid-band radiating elements is about 0.25-0.35 wavelengths corresponding to frequencies in the upper portion of the low-band operating frequency range. Consequently, non-trivial common mode currents may be induced on the mid-band radiating elements when excited by RF energy in the low-band operating frequency range. The inducement of these common mode currents on the higher frequency band radiating element is referred to as a common mode resonance. These common mode resonances may distort the radiation patterns of the lower frequency band linear arrays.

[0083] The radiating elements according to embodiments of the present invention may include parallel inductor-capacitor ("LC") circuits in the electrical connections between the feed stalk and the dipole radiators. These LC circuit may be tuned to move the common mode resonance to be outside the low-band operating frequency range.

[0084] Embodiments of the present invention will now be described in greater detail with reference to FIGS.2A-8.

[0085] FIG.2A is a schematic front view of a multiband base station antenna 100 according to embodiments of the present invention with the radome removed. The multiband base station antenna 100 is similar to base station antenna 1 in many respects. Accordingly, the discussion below will focus on the differences between base station antenna 1 and base station antenna 100. Elements that are the same in the two base station antennas 1, 100 are labeled using the same reference numerals.

[0086] As can be seen by comparing FIGS.1B and 2A, the primary difference between the two base station antennas 1, 100 is that the four mid-band linear arrays 30-3 through 30-6 of base station antenna 100 and their associated feed networks (which are not visible in FIGS.1A-Attorney Docket No.9833.7492.WO 1B) are replaced in base station antenna 100 with four mid-band linear array assemblies 200-1 through 200-4. The reflector 10 of base station antenna 1 is also replaced in base station antenna 100 with a modified reflector 110. As shown in FIG.2A, the reflector 110 may extend substantially the entire length of the base station antenna 100, which provides increased structural strength. It should also be noted that the mid-band feed board printed circuit boards 34 for mid-band linear arrays 30-3 through 30-6 of base station antenna 1, each of which includes two mid-band radiating elements 32 thereon, are omitted in base station antenna 100.

[0087] FIG.2B is a schematic front perspective view of a portion of the four mid-band linear array assemblies 200-1 through 200-4 that are included in base station antenna 100. FIG. 2B also shows a portion of the reflector 110 of the base station antenna 100 for context. As shown in FIG.2B, each mid-band linear array assembly 200 includes a mid-band linear array 210 of mid-band radiating elements 300 and a cavity phase shifter assembly 220. The cavity phase shifter assemblies 220 form the feed networks for the respective mid-band linear arrays 210. The reflector 110 includes a plurality of openings 112. Each mid-band radiating element 300 extends through a respective one of the openings 112 in the reflector 110 so that most (or even all) of each mid-band radiating element 300 is positioned forwardly of the reflector 110. The cavity phase shifter assemblies 220 are mounted rearwardly of the reflector 110. Each mid- band radiating element 300 may be configured to operate in the 1427-2690 MHz frequency band, or a portion thereof. To simplify the drawing, only six of the radiating elements 300 of each of the first through fourth mid-band linear arrays 210-1 through 210-4 are shown in FIG.2B.

[0088] Each mid-band cavity phase shifter assembly 220 is connected to a pair of the RF ports (not shown, but see RF ports 8 of FIG.1A) since the mid-band radiating elements 300 are dual-polarized radiating elements that transmit and receive RF signals at two orthogonal polarizations. Each mid-band cavity phase shifter assembly 220 includes a plurality of output traces that may extend outside the metal housing of the cavity phase shifter assembly 220 to be directly connected to radiator assemblies of the respective mid-band radiating elements 300, as will be described in more detail below.

[0089] FIG.3A is a schematic side perspective view of one of the mid-band radiating elements 300 included in the mid-band linear array assemblies 200 of FIG.2B. FIG.3B is an exploded perspective view of the mid-band radiating element 300 of FIG.3A. Referring to FIGS.3A-3B, the mid-band radiating element 300 includes a feed stalk 310 and a radiatorAttorney Docket No.9833.7492.WO assembly 350. The feed stalk 310 has a base 312 and a distal end 314 that are spaced apart from each other in a first direction (the forward direction F). The base 312 of the feed stalk 310 is adjacent the reflector 110 (see FIG.2B). The radiator assembly 350 is mounted adjacent the distal end 314 of the feed stalk 310.

[0090] The feed stalk 310 comprises a metal ground stalk 320 and first and second signal traces 340-1, 340-2. The metal ground stalk 320 comprises first and second metal ground pieces 322-1, 322-2 in example embodiments. The first and second metal ground pieces 322-1, 322-2 are mirror-image pieces in the depicted embodiment. Each metal piece 322-1, 322-2 may be formed by stamping (cutting via a stamping process) and bending sheet metal, and hence the metal ground pieces 322-1, 322-2 may be fabricated at very low cost. However, embodiments of the present invention are not limited to sheet metal ground pieces; for example, in other embodiments, the first and second metal ground pieces 322-1, 322-2 may be die cast metal ground pieces, or can be implemented as a single monolithic die cast metal ground piece.

[0091] FIG.3C is a schematic perspective view of the metal ground stalk 320. The metal ground stalk 320 has a base 328B and a distal end 328D that are spaced apart from each other in the forward direction F. As shown in FIG.3C, the first metal ground piece 322-1 comprises a total of five plates that extend in different perpendicular planes. In particular, the first metal ground piece 322-1 comprises a first plate 324-1 and a fourth plate 324-4 that have respective longitudinal axes that extend in the forward direction F, a second plate 324-2 that is at the base 328B of the metal ground stalk 320 that extends in the vertical and horizontal directions V, H, and a third plate 324-3 and a fifth plate 324-5 that are at the distal end 328D of the metal ground stalk 320 that each also extend in the vertical and horizontal directions V, H. Similarly, the second metal ground piece 322-2 comprises a total of five plates that extend in different perpendicular planes. In particular, the second metal ground piece 322-2 comprises a sixth plate 324-6 and a ninth plate 324-9 that have respective longitudinal axes that extend in the forward direction F, a seventh plate 324-7 that is at the base 328B of the metal ground stalk 320 that extends in the vertical and horizontal directions V, H, and an eighth plate 324-8 and a tenth plate 324-10 that are at the distal end 328D of the metal ground stalk 320 that each also extend in the vertical and horizontal directions V, H. The first plate 324-1 and the fourth plate 324-4 extend in perpendicular planes, and the sixth plate 324-6 and the ninth plate 324-9 also extend in perpendicular planes. The sixth plate 324-6 extends in parallel to the first plate 324-1 and theAttorney Docket No.9833.7492.WO ninth plate 324-9 extends in parallel to the fourth plate 324-4 and may be coplanar with the fourth plate 324-4. The third, fifth, eighth and tenth plates 324-3, 324-5, 324-8, 324-10 may each be rectangular (e.g., square) plates that arranged adjacent each other so that they form a larger square when viewed from the front. The third, fifth, eighth and tenth plates 324-3, 324-5, 324-8, 324-10 may be coplanar with each other and may extend in the vertical and horizontal directions V, H.

[0092] A first rectangular slot 326-1 is provided in the second plate 324-2 and a second rectangular slot 326-1 is provided in the third plate 324-3. Similarly, a third rectangular slot 326- 3 is provided in the seventh plate 324-7 and a fourth rectangular slot 326-4 is provided in the eighth plate 324-8. The first and second slots 326-1, 326-2 may be aligned in the forward direction F, and the third and fourth slots 326-3, 326-4 may be aligned in the forward direction F,

[0093] Referring to FIGS.3A-3C, the first signal trace 340-1 extends in the forward direction F adjacent the first metal plate 324-1 of the first metal piece 322-1. The first signal trace 340-1 extends from the base 312 of the feed stalk 310 and past the distal end 314 thereof. The first signal trace 340-1 may be implemented, for example, as a metal trace on a printed circuit board, although embodiments of the present invention are not limited thereto. The first signal trace 340-1 extends through both the first rectangular slot 326-1 and the second rectangular slot 326-2. Similarly, the second signal trace 340-2 extends in the forward direction F adjacent the sixth metal plate 324-6 of the second metal piece 322-2. The second signal trace 340-2 extends from the base 312 of the feed stalk 310 and past the distal end 314 thereof. The second signal trace 340-2 may be implemented, for example, as a metal trace on a printed circuit board, although embodiments of the present invention are not limited thereto. The second signal trace 340-2 extends through both the third rectangular slot 326-3 and the fourth rectangular slot 326-4. As will be discussed in greater detail below with reference to FIGS.4A-4C, the first signal trace 340-1 comprises an output trace 268 of a first phase shifter assembly 260-1 and the second signal trace 340-2 comprises 268 an output trace of a second phase shifter assembly 260- 2.

[0094] FIG.3D is a front view of a radiator assembly 350 of the mid-band radiating element 300 of FIGS.3A-3C. Referring to FIGS.3A-3B and 3D, the radiator assembly 350 comprises a first printed circuit board 360, a second printed circuit board 370, four sheet metalAttorney Docket No.9833.7492.WO dipole arm pieces 380-1 through 380-4, and a director 390 (FIGS.3A-3B). The first printed circuit board 360 includes first and second rectangular slots 362-1, 362-2. The first and second signal traces 340-1, 340-2 are inserted through the first and second rectangular slots 362-1, 362-2 to mount the first printed circuit board 360 on the feed stalk 310. The first printed circuit board 360 further includes a first metal structure 364-1 in the form of a first metal trace 366-1 and a first metal pad 368-1 and a second metal structure 364-2 in the form of a second metal trace 366- 2 and a second metal pad 368-2. At least part of one of the first and second metal traces 366-1, 366-2 may be implemented on a first side of the first printed circuit board 360 and the other of the first and second metal traces 366-1, 366-2 may be implemented on a second side of the first printed circuit board 360 so that the first and second metal traces 366-1, 366-2 may cross while remaining electrically isolated from each other. Plated through holes (not shown) that extend through a dielectric substrate of the first printed circuit board 360 may be used to implement at least part of one of the first and second metal traces 366-1, 366-2 on the second side of the printed circuit board 360. The first and second metal pads 368-1, 368-2 may be implemented on the same side of the first printed circuit board 360. First and second solder joints may be applied that physically and electrically connect the first and second signal traces 340-1, 340-2 to the first and second metal traces 366-1, 366-2. As noted above, the first and second signal traces 340-1, 340-2 may comprise output traces 268 of first and second phase shifter assemblies 260-1, 260-2. Consequently, the output traces 268 of first and second phase shifter assemblies 260-1, 260-2 are directly electrically connected to the radiator assembly 350.

[0095] The second printed circuit board 370 may be mounted either behind or in front of the first printed circuit board 360. In the depicted embodiment, the second printed circuit board 370 is mounted behind the first printed circuit board 360. The second printed circuit board 370 includes first and second rectangular slots that are not visible in the figures but which are directly behind the first and second slots 362-1, 362-2 in the first printed circuit board 360 when the radiating element 300 is viewed from the front. The first and second signal traces 340-1, 340-2 are inserted through the first and second rectangular slots in the second printed circuit board 370 to mount the second printed circuit board 370 on the feed stalk 310. No galvanic electrical connection is provided between the first and second signal traces 340-1, 340-2 and the second printed circuit board 370, but the metal pads 368-1, 368-2 on the first printed circuit board 360Attorney Docket No.9833.7492.WO may be capacitively coupled to the metal pads 374-1, 374-2 (discussed below) on the second printed circuit board 370.

[0096] As shown in FIG.3D, the second printed circuit board 370 includes first through fourth metal pads 374-1 through 374-4 on one side thereof. As shown in FIGS.3A-3B, the first through fourth metal pads 374-1 through 374-4 may overlap the respective third, eighth, tenth and fifth plates 324-3, 324-8, 324-10, 324-5 of the metal ground stalk 320 in the forward direction so that each metal pads 374-1 through 374-4 capacitively couples with a corresponding one of the third, fifth, eighth and tenth plates 324-3, 324-5, 324-8, 324-10. The capacitive coupling may, for example, be through a dielectric substrate of the second printed circuit board 370 or may be through a different dielectric layer such as a solder mask.

[0097] The first through fourth sheet metal dipole arm pieces 380-1 through 380-4 may be mounted on the second printed circuit board 370 and may be configured to capacitively couple with the respective first through fourth metal pads 374-1 through 374-4. Each metal pad 374 and a corresponding one of the dipole arm pieces 380 together form a dipole arm 382 of radiating element 300. In particular, the first metal pad 374-1 and the first dipole arm piece 380- 1 form a first dipole arm 382-1, the second metal pad 374-2 and the second dipole arm piece 380-2 form a second dipole arm 382-2, the third metal pad 374-3 and the third dipole arm piece 380-3 form a third dipole arm 382-1, and the fourth metal pad 374-4 and the fourth dipole arm piece 380-4 form a fourth dipole arm 382-4. The first dipole arm 382-1 and the third dipole arm 382-3 together form a first dipole radiator 384-1. The second dipole arm 382-2 and the fourth dipole arm 382-4 together form a second dipole radiator 384-2. Each of the first through fourth sheet metal dipole arm pieces 380-1 through 380-4 may include bent sections 381 that allow the electrical length of each dipole arm 382 to be increased without further expanding the footprint of radiating element 300 (i.e., the area of radiating element 300 when viewed from the front).

[0098] The director 390 is mounted forwardly of the first and second printed circuit boards 360, 370. The director 390 may, for example, be configured to narrow the azimuth beamwidth of the radiation pattern generated by radiating element 300 in at least a portion of the operating frequency band of radiating element 300. The director 390 may be of conventional design.

[0099] As discussed above, various problems may arise when radiating elements that operate in different frequency bands are positioned in close proximity to each other in a baseAttorney Docket No.9833.7492.WO station antenna. One known problem is that a higher frequency radiating element may have a so- called "common mode resonance" that can distort the antenna beam of a nearby lower-band radiating element. Dipole-based radiating elements are differentially fed devices, and resonate when each center-fed dipole arm is about a quarter of a wavelength of incident RF energy. However, the combination of the feed stalk and the dipole arm may also resonate as a quarter wavelength monopole radiator. In other words, if RF radiation impinges on the mid-band radiating element 300 at a frequency that has a corresponding wavelength that is about four times the electrical length of the combination of the feed stalk and a dipole arm, then common mode currents may form on the feed stalk and the dipole radiator. These common mode currents will also cause radiation of RF energy. Typically, both the feed stalk and the dipole arms of a dipole- based radiating element have a length that is about one-quarter a wavelength (called the "center wavelength" herein) corresponding the center frequency of the operating frequency band of the radiating element. Thus, the combined length of the feed stalk and the dipole arm is about one- half the center wavelength. Since much of the mid-band operating frequency range includes frequencies that are twice the frequency of frequencies within the low-band operating frequency range, the combined length of the feed stalk and the dipole arm of a typical mid-band radiating element will be a little less than one quarter of the center wavelength of the low-band operating frequency range. As a result, common mode currents may flow on the mid-band radiating elements in response to RF energy that is transmitted by nearby low-band radiating elements. As these common mode currents emit RF radiation, the net effect is that the mid-band radiating elements may distort the antenna beams of nearby low-band radiating elements, degrading the performance of the low-band arrays. For example, the low-band radiation patterns may have reduced directivity and higher beamwidths than desired.

[0100] The mid-band radiating elements 300 may include one or more parallel inductor-capacitor ("LC") circuits in the electrical connections between the feed stalk 310 and the dipole radiators 384. These LC circuit may be tuned to move the common mode resonance outside of the low-band operating frequency range. Thus, the mid-band radiating elements 300 may readily be designed to have little to no impact on the radiation patterns of nearby low-band radiating elements 22 in base station antenna 100.

[0101] For example, FIG.3E is an enlarged plan view of mid-band radiating element 300 that illustrates one example implementation of these parallel LC circuits. As discussedAttorney Docket No.9833.7492.WO above, the printed circuit board 370 may comprise four metal pads 374-1 through 374-4 on one side thereof. In addition, as shown in FIG.3E, the second printed circuit board 370 may further comprise four additional, smaller metal pads 376-1 through 376-4 that are on the opposed side of the second printed circuit board 370. Each metal pad 374 may capacitively couple with a respective one of the smaller metal pads 376 to generate the capacitances of the parallel LC circuits. In addition, thin metal traces 378-1 through 378-4 are provided that include portions on each metallized layer of the second printed circuit board 370, where these portions are connected by respective plated via holes 379. The thin metal traces 378 are coupled in parallel to the respective capacitances to form the parallel LC circuits.

[0102] As discussed above, the mid-band radiating element 300 of FIGS.3A-3D may be used to implement the radiating elements in the mid-band linear array assemblies 200 of FIG. 2B. Each mid-band linear array assembly 200 includes a cavity phase shifter assemblies 220. FIG.4A is a schematic perspective view of the portion of FIG.2B contained in the box labelled 4A that illustrates how the mid-band radiating elements 300 are mounted on one of the cavity phase shifter assemblies 220. FIG.4B is a cross-sectional view taken along line 4B—4B of FIG.4A. While FIGS.4A and 4B illustrate one example cavity phase shifter design, it will be appreciated that cavity phase shifter assemblies are known in the art and can have a variety of different configurations. For example, U.S. Patent No.11,677,141 discloses a variety of other cavity phase shifter assemblies and the operation thereof. The entire content of U.S. Patent No. 11,677,141 is incorporated herein by reference. Cavity phase shifter assemblies are typically used as they include low-loss stripline RF transmission lines and because they can be designed to provide cableless connections to the radiating elements, which reduces the number of solder joints. Thus, while FIGS.4A-4B illustrate one cavity phase shifter design, it will be appreciated that any suitable cavity phase shifter assembly design may be used to implement the cavity phase shifter assemblies 220, including any of the cavity phase shifter assemblies disclosed in U.S. Patent No.11,677,141.

[0103] As shown in FIGS.4A-4B, the cavity phase shifter assembly 220 includes a longitudinally-extending metal housing 230. The metal housing 230 may be formed, for example, by extrusion. First and second longitudinally-extending cavities 240-1, 240-2 are defined within the metal housing 230. The metal housing 230 includes a front wall 232 and a pair of main sidewalls 234-1, 234-2 that together define the first and second cavities 240-1, 240-Attorney Docket No.9833.7492.WO 2. In the depicted embodiment, the cavities 240-1, 240-2 do not include any rear wall. As shown, the first and second cavities 240-1, 240-2 may share a common sidewall 236 in some cases. The metal housing 230 further includes a first generally c-shaped structure 250-1 that extends laterally from the first main sidewall 234-1 and a second generally c-shaped structure 250-2 that extends laterally from the second main sidewall 234-2. Each generally c-shaped structure 250 may have a front wall 252 that extends parallel to the front wall 232, a rear wall 258 that also extends parallel to the front wall 232, and a sidewall 254 that extends parallel to the main sidewalls 234. The first generally c-shaped structure 250-1 and the first main sidewall 234- 1 define a third cavity 240-3 and the second generally c-shaped structure 250-2 and the second main sidewall 234-2 define a fourth cavity 240-4. A longitudinal axis of each cavity 240 may extend parallel to a longitudinal axis of the base station antenna 100.

[0104] A first phase shifter assembly 260-1 is mounted in the first cavity 240-1, and a second phase shifter assembly 260-2 is mounted in the second cavity 240-2. Each phase shifter assembly 260 may comprise, for example, a phase shifter printed circuit board 262 with RF transmission lines formed thereon along with sliding dielectric pieces 263. Sliding dielectric phase shifters are well known in the art and thus further description thereof will be omitted.

[0105] FIG.4C is a plan view of one of the phase shifter printed circuit boards 262 included in the cavity phase shifter assembly 220. As shown in FIG.4C, each phase shifter printed circuit board 262 may include an input trace 264 that is electrically connected to a feed network of the base station antenna 100, a power divider (implemented as a plurality of T- junctions 266 in the RF transmission lines) that splits RF signals input at the input trace 264 into a plurality of sub-components, and a plurality of output traces 268 where the phase adjusted sub- components of the RF signal are output from the phase shifter assembly 260. Each phase shifter assembly 260 may also include sliding dielectric pieces 263 that are configured to impart an adjustable phase taper to the sub-components of the RF signal before they reach the respective output RF transmission lines. First and second RF feed lines 242-1, 242-2 (e.g., stripline RF feed lines) may be disposed in the third and fourth cavities 240-3, 240-4. The first and second RF feed lines 242-1, 242-2 may be electrically connected to the respective input RF traces 264 on the first and second phase shifter printed circuit boards 262-1, 262-2.

[0106] As shown in FIG.4C, the output traces 268 on phase shifter printed circuit board 262 are elongated traces that extend in the forward direction. The front wall 232 of theAttorney Docket No.9833.7492.WO metal housing 230 includes a plurality of openings (not shown) and each output trace 268 extends through a respective one of these openings. As discussed above, the elongated output traces 268 form the first and second signal traces 240-1, 240-2 of each radiating element 300 and are soldered to the first printed circuit board 360 of the radiator assembly 350 thereof. Thus, through a single solder joint per polarization, it is possible to galvanically connect the phase shifter assemblies 260-1, 260-2 to the radiating elements 300 according to embodiments of the present invention.

[0107] Referring again to FIGS.4A-4B, it can be seen that the mid-band radiating element 300 may be mounted on the front wall 232 of the metal housing 230 of cavity phase shifter assembly 220. A solder mask (not shown) or other dielectric layer may be interposed between the feed stalk 310 and the metal housing 230 so that the second and seventh plates 324- 2, 324-7 of the ground stalk 320 are capacitively coupled to the metal housing 230 of the cavity phase shifter assembly 220. As shown in FIGS.4A-4B, the reflector 110 is also mounted on (or at least forwardly of) the cavity phase shifter assembly 220. The reflector 110 includes a plurality of openings 112 that are positioned at the locations where the mid-band radiating elements 300 are to be mounted. Each opening 112 is larger than the footprint of the combination of the feed stalk 310, the first printed circuit board 360 and the second printed circuit boards 370 of a mid-band radiating element 300. Herein the "footprint" of an element refers to area of the element when viewed from the front.

[0108] The metal ground stalk 320 of each mid-band radiating element 300 may be mounted on the forwardly-extending output traces 268 of the phase shifter printed circuit boards 262 with a solder mask interposed between the metal housing 230 and each metal ground stalk 320. The second printed circuit board 370 of each radiating element 300 may be mounted on the distal end of the output traces 268 and the metal pads 374 thereon may capacitively couple to the metal ground stalk 320. The first printed circuit board 360 may then be mounted on the distal end of the output traces 268 forwardly of the second printed circuit board 370 and the output traces 268 may be soldered to respective metal structures 364 on the first printed circuit board 360 to partially pre-assemble each mid-band radiating element 300 on the cavity phase shifter assembly 220. Since the openings 112 are larger than the footprint of a partially assembled mid- band radiating element 300, the cavity phase shifter assembly 300 with the partially assembled mid-band radiating elements 300 mounted thereon may be installed behind the reflector 110 soAttorney Docket No.9833.7492.WO that the partially assembled mid-band radiating elements 300 pass through the openings 112 to project forwardly on the front side of the reflector 110. The dipole arm pieces 380 may then be mounted on the second printed circuit board 370 (e.g., using snap clips, not shown) and the directors 390 may be mounted forwardly of the dipole arm pieces 380 to complete the assembly of each mid-band radiating element 300. While not shown in the figures, each mid-band radiating element 300 may include a plastic support that holds the director 390 thereof in place.

[0109] Since the dipole arm pieces 380 and the director 390 of each mid-band radiating element 300 may be readily mounted on their second printed circuit board 370 using snap clips or other readily releasable attachment mechanisms, the dipole arm pieces 380 and the director 390 of each mid-band radiating element 300 may be easily installed onto each partially assembled mid-band radiating element 300 after the partially assembled mid-band radiating elements 300 have been installed into the cavity phase shifter assemblies 220 so that each cavity phase shifter assembly 220 may be fully assembled before it is installed into the base station antenna 100. Consequently, each cavity phase shifter assembly 220 may be fully tested before it is installed in the base station antenna 100 to identify poor solder joints, misconnections, defective components and the like. This allows problems to be identified and corrected before the base station antenna 100 is assembled, and makes it much easier to fix any problems that are identified. After testing is completed, the dipole arm pieces 380 and the director 390 of each mid-band radiating element 300 may be removed so that the cavity phase shifter assembly 220 with the partially assembled mid-band radiating elements 300 thereon may be installed into the base station antenna 100. Then, the dipole arm pieces 380 and the director 390 of each mid-band radiating element 300 may again be attached.

[0110] Referring again to FIGS.3A-3B, pursuant to some embodiments of the present invention, radiating elements are provided that comprise a feed stalk 310 that comprises a metal ground stalk 320 that has a base 328B and a distal end 328D that are spaced apart from each other in a first direction (the forward direction F) and a first signal trace 340-1 that extends in the first direction adjacent the metal ground stalk 320, and a radiator assembly 350 that is mounted adjacent the distal end 328D of the metal ground stalk 320. The first signal trace 340-1 comprises an output trace 268 of a first phase shifter assembly 260 and directly electrically connects to the radiator assembly 350.Attorney Docket No.9833.7492.WO

[0111] In some embodiments, the metal ground stalk 320 may comprise a first plate 324-1 that has a longitudinal axis that extends in the first (forward) direction F and a second plate 324-2 that is at the base 328B of the metal ground stalk 320, the second plate 324-2 having a major surface that extends in a second direction (the horizontal direction H) and a third direction (the vertical direction V) that are perpendicular to each other and to the forward direction F. In some embodiments, the metal ground stalk further comprises a third plate 324-3 that extends in the second direction and the third direction. The third plate 324-3 may be at the distal end 328D of the metal ground stalk 320.

[0112] In some embodiments, the metal ground stalk 320 comprises a first metal piece 322-1 and a second metal piece 322-2, and the first, second and third metal plates 324-1, 324-2, 324-3 are each part of the first metal piece 322-1, the first metal piece 322-1 further comprising a fourth plate 324-4 that extends in the first direction and a fifth plate 336-5 that extends in the second direction and the third direction, where the fifth plate 336-5 is coplanar with the third plate 324-3. The second metal piece 322-2 may comprise a sixth plate 324-6 and a ninth plate 324-9 that each have a longitudinal axis that extends in the first direction, a seventh plate 324-7 that extends in the second direction and the third direction at the base 328B of the metal ground stalk 320, and an eighth plate 324-8 and a tenth plate 324-10 that each extend in the second direction and the third direction. The eighth plate 324-8 and the tenth plate 324-10 may be coplanar with the third plate 324-3 and the fifth plate 324-5.

[0113] The radiating element 300 may further comprise a second signal trace 340-2 that extends in the first direction adjacent the metal ground stalk 320 to directly electrically connect to the radiator assembly 350. The second signal trace 340-2 may comprise an output trace 268 of a second phase shifter assembly 260-2.

[0114] The first signal trace 340-1 may extend through at least a first opening 326-1 in the first metal piece 322-1 and the second signal trace 340-2 may extend through at least a third 326-3 opening in the second metal piece 322-2.

[0115] In some embodiments, the first plate 324-1 may extend in a first plane and the fourth plate 324-4 may extend in a second plane that is perpendicular to the first plane. In some embodiments, the third plate 324-3, the fifth plate 324-5, the eighth plate 324-8 and the tenth plate 324-10 may each extend in a third plane. In some embodiments, the second plate 324-2 and the seventh plate 324-7 may each extend in a fourth plane that is parallel to the third plane.Attorney Docket No.9833.7492.WO In some embodiments, the sixth plate 324-5 may extend in a fifth plane that is perpendicular to the first plane.

[0116] In some embodiments, the radiator assembly 350 comprises a first printed circuit board 360 that is galvanically coupled to the first signal trace 340-1. The radiator assembly 350 may further comprise a second printed circuit board 370 that includes a plurality of metal pads 374 that are capacitively coupled to the metal ground stalk 320. The radiator assembly 350 may further comprise a plurality of sheet metal dipole arm pieces 380 that are capacitively coupled to the respective metal pads 374 on the second printed circuit board 370. In some embodiments, the first printed circuit board 360 may be mounted forwardly of the second printed circuit board 370.

[0117] The first phase shifter assembly 260-1 may be at least partially mounted within a metal housing 230 that has a front wall 232, and the first signal trace 340-1 extends through an opening in the front wall 232.

[0118] In some embodiments, the radiating element 300 may be part of a base station antenna 100 that comprises a reflector 110 that includes an opening 112 that is larger than a footprint of the metal ground stalk 320.

[0119] Still referring to FIGS.3A-3B, pursuant to further embodiments of the present invention, radiating elements are provided that comprise a metal ground stalk 320 that has a base 328B and a distal end 228D that are spaced apart from each other in a first direction (the forward direction F), a first signal trace 340-1 that extends in the first direction adjacent the metal ground stalk 320, and a radiator assembly 350. The radiator assembly 350 may comprise a first printed circuit board 360 that is mounted forwardly of the metal ground stalk 320, a second printed circuit board 370, and a first sheet metal dipole arm piece 380-1.

[0120] In some embodiments, the first printed circuit board 360 is mounted on the first signal trace 340-1 and may, for example, be soldered to a first metal structure 364-1 on the first printed circuit board 360. The metal ground stalk 320 may be capacitively coupled to a first metal pad 374 on the second printed circuit board 370. The radiator assembly 350 may further comprise a second sheet metal dipole arm piece 380-2, a third sheet metal dipole arm piece 380- 3 and a fourth sheet metal dipole arm piece 380-4, and the second printed circuit board 370 may further comprise a second metal pad 374-2, a third metal pad 374-3 and a fourth metal pad 374-Attorney Docket No.9833.7492.WO 4. The first through fourth sheet metal dipole arm pieces 380-1 through 380-4 are capacitively couped to the respective first through fourth metal pads 374-1 through 374-4.

[0121] As shown in FIGS.4A-4C, pursuant to further embodiments of the present invention, a cavity phase shifter assembly 220 is provided that comprises a monolithic metal housing 230 that comprises a front wall 232 and first and second sidewalls 234-1, 234-2 that extend rearwardly from the front wall 232. The front wall 232 and the first and second side walls 234-1, 234-2 may define a first cavity 240-1. The cavity phase shifter assembly 220 further comprises a first phase shifter assembly 260-1 that is at least partly mounted in the first cavity 240-1. Moreover, a rear side of the first cavity 240-1 is at least partially open.

[0122] In some embodiments, the phase shifter assembly 260-1 is configured to be inserted into the first cavity 240-1 from the rear side of the first cavity 240-1. In some embodiments, the front wall 232 includes a plurality of openings, and forwardly extending output traces 268 of the phase shifter assembly 260-1 are configured to be inserted through the respective openings when the phase shifter assembly 260-1 is mounted in the first cavity 240-1. In some embodiments, a rear side of the first cavity 240-1 may be fully open.

[0123] In some embodiments, the phase shifter assembly 260-1 comprises a main phase shifter printed circuit board 262-1, and portions of each output trace 268 that extend through the respective openings in the front wall 232 each have a length in the forward direction that is at least one-quarter of a length of the first sidewall 234-1 in the forward direction. In some embodiments, portions of each output trace 268 that extend through the respective openings each have a length in the forward direction that is at least one-third of the length of the first sidewall 234-1 in the forward direction.

[0124] In some embodiments, the cavity phase shifter assembly 220 is provided in combination with a linear array of radiating elements 210 to provide a linear array assembly 200. In such embodiments, each output trace 268 may comprise a signal trace 340 of a respective one of the radiating elements. Each radiating element 300 in the linear array 210 may include a radiator assembly 350, and each output trace 268 may be directly electrically connected to the radiator assembly 350. For example, each radiator assembly 350 may include a first printed circuit board 360, and each output trace 268 may be soldered to a respective metal structure 364 on the respective first printed circuit boards 360.Attorney Docket No.9833.7492.WO

[0125] Still referring to FIGS.4A-4C, pursuant to further embodiments of the present invention, a cavity phase shifter assembly 220 is provided that comprises a longitudinally- extending monolithic metal housing 230 that defines a first cavity 240-1 that has longitudinally- extending first and second sidewalls 234-1, 234-2 and a phase shifter assembly 260-1 that comprises a main printed circuit board 262-1. A rear of the first cavity 240-1 includes a longitudinally-extending opening that is configured to receive the main printed circuit board 262- 1. The main printed circuit board 262-1 includes a plurality of forwardly-extending output traces 268. The monolithic metal housing 230 includes a front wall 232 and the first and second sidewalls 234-1, 234-2 extend rearwardly from the front wall232. The front wall 232 includes a plurality of openings and the forwardly-extending output traces 268 extend through these respective openings.

[0126] FIG.5 is a schematic perspective view of an alternative metal ground stalk 320' that can be used on place of the metal ground stalk 320 of FIG.3C.

[0127] As shown in FIG.5, the metal ground stalk 320' is very similar to the metal ground stalk 320, with the primary difference being that the first and fourth metal plates 324-1 and 324-4 extend in perpendicular planes as do the sixth and ninth metal plates 324-6 and 324-9 in metal ground stalk 320, whereas in metal ground stalk 320' the first and fourth metal plates 324-1 and 324-4' are coplanar with each other, and the sixth and ninth metal plates 324-6 and 324-9' are likewise coplanar with each other. The design of metal ground stalk 320' may use less sheet metal, but also may exhibit reduced cross-polarization isolation.

[0128] FIG.6 is a schematic side perspective view of the portion of FIG.2B contained in the box labelled 4A with an alternative mid-band radiating element 400 mounted on the cavity phase shifter assembly 220.

[0129] The mid-band radiating element 400 may have a number of similarities to mid- band radiating element 300. In particular, the mid-band radiating element 400 may include the exact same feed stalk 310 as mid-band radiating element 300, including first and second signal traces 340-1, 340-2 that comprise elongated, forwardly extending output traces 268 of first and second phase shifter printed circuit boards 262-1, 262-2. The mid-band radiating element 400 also includes the first printed circuit board 360, which may be mounted on the first and second signal traces 340-1, 340-2 in the same fashion as discussed above with reference to mid-bandAttorney Docket No.9833.7492.WO radiating element 300. In addition, mid-band radiating element 400 further includes a director 390 which may be identical to the director 390 of mid-band radiating element 300.

[0130] Mid-band radiating element 400, however, does not include the second printed circuit board 370 or the dipole arm pieces 380-1 through 380-4 of mid-band radiating element 300. As such, in mid-band radiating element 400, the third, fifth, eighth and tenth metal plates 324-3, 324-5, 324-8, 324-10 form the dipole arms of mid-band radiating element 400, with dipole arms 482-1 and 482-3 (metal plates 324-3, 324-10) forming a first center-fed dipole radiator 484-1 and dipole arms 482-2 and 482-4 (metal plates 324-8, 324-5) forming a second center-fed dipole radiator 484-2. As noted above, the dipole arms of a cross-dipole radiating element typically have an electrical length of about one-quarter of a wavelength of the center frequency of the operating frequency band. In order to reduce the physical length of the dipole arms while achieving a desired electrical length, the dipole arms are often formed as "fatter" plates or as conductive loops so that the current path (and hence the electrical length) can be increased without increasing the physical length of the dipole arms. The dipole arms 482, however, preferably are relatively short to keep the openings 112 in the reflector 110 small. Thus, the dipole arms 482 may not, by themselves, have an electrical length of one-quarter of a wavelength of the center frequency of the operating frequency band in some embodiments.

[0131] In order to increase the effective length of the dipole arms 482, each mid-band radiating element 400 further includes a parasitic metal element 485 that is not present in mid- band radiating element 300. In the depicted embodiment, the parasitic metal element 485 is in the form of a parasitic metal ring 485 that is mounted forwardly of both the dipole arms 482 and the first printed circuit board 360. The parasitic metal element 485 includes a circular annular ring 486 and first through fourth inwardly-extending metal plates 487-1 through 487-4 that extend radially inward from the circular annular ring 486.

[0132] Centers of the outer edge of metal plates 487-1 through 487-4 may be at angles of 0⁰, 90⁰, 180⁰ and 270⁰, respectively, around the circular annular ring 486 when the mid-band radiating element 400 is mounted for use in base station antenna 100. Each metal plate 487 may have a diamond or arrow shape in example embodiments (as shown), although it will be appreciated that the metal plates 487 may have a wide variety of different shapes. The longitudinal axes of dipole arms 482-1 through 482-4 may extend at angles of 135⁰, 225⁰, 315⁰ and 45⁰ respectively, with respect to the circular annular ring 486 when the mid-band radiatingAttorney Docket No.9833.7492.WO element 400 is mounted for use in base station antenna 100. Consequently, each metal plate 487 may overlap two of the dipole arms 482 in the forward direction. The parasitic metal element 485 further includes first through fourth additional four metal pads 488-1 through 488-4. Each additional metal pad 488 may include a first segment that extends outwardly from the outer edge of the circular annular ring 486 at locations where the first through fourth inwardly-extending metal plates 487-1 through 487-4 connect to the circular annular ring 486 and a second segment that extends rearwardly from the outer edge of the first segment. The first through fourth additional four metal plates 488-1 through 488-4 effectively lengthen the metal plates 487-1 through 487-4. Bending the second segment of each metal plate 488 rearwardly allows the length of each metal plate 488 to be increased without further increasing the footprint of the parasitic metal ring 485.

[0133] The metal plates 487, 488 and the circular annular ring 486 may capacitively couple with the dipole arms 482 that they overlap, thereby capacitively loading the dipole arms 482. This acts to effectively increase the electrical length of the dipole arms 482, thereby extending the operating bandwidth of the mid-band radiating element 400, allowing mid-band radiating element 400 to operate across the full 1427-2690 MHz frequency range with good return loss performance. The parasitic metal element 485 may be formed of stamped and bent sheet metal (e.g., aluminum) in some embodiments. Moreover, because the parasitic metal element 485 is capacitively coupled with the dipole arms 482, mid-band radiating element 400 does not have a common mode resonance within the low-band operating frequency band.

[0134] As shown in FIG.6, the mid-band radiating element 400 comprises a first monolithic sheet metal piece 322-1 that includes first and second metal ground plates 324-1, 324-4 and first and second dipole arms 482-1, 482-2 extending from distal ends of the first and second metal ground plates 324-1, 324-4 and a second monolithic sheet metal piece 322-2 that includes third and fourth metal ground plates 324-6, 324-9 and third and fourth dipole arms 482- 3, 482-4 extending from distal ends of the third and fourth ground metal ground plates 324-6, 324-9. The first and third dipole arms 482-1, 482-3 form a first dipole radiator 484-1 and the second and fourth dipole arms 482-2, 482-4 form a second dipole radiator 484-2.

[0135] In some embodiments, the radiating element 400 further comprises a first signal trace 340-1 mounted adjacent the first metal ground plate 324-1 and a second signal trace 340-2 mounted adjacent the third metal ground plate 324-6. The radiating element 400 may alsoAttorney Docket No.9833.7492.WO include a first printed circuit board 360 that is mounted on the first and second signal traces 340- 1, 340-2. The first printed circuit board 360 may be mounted forwardly of the first and second dipole radiators 482-1, 482-2. The radiating element 400 may further include a parasitic metal element 485 that is mounted forwardly of the first printed circuit board 360. The parasitic metal element 485 may comprise, for example, a parasitic metal ring 485 that is capacitively coupled to the first through fourth dipole arms 482-1 through 482-4. In addition, the radiating element 400 may also include one or both of a director 490 that is mounted forwardly of the parasitic metal element 485 and / or a meta director 492 that is mounted forwardly of the director 390. In some embodiments, the meta director 492 comprises a printed circuit board 494 that comprises a plurality of unit cell metal structures 496. The design and operation of meta directors such as meta director 496 (also referred to as meta lenses) are discussed in further detail in PCT Application No. PCT / US24 / 036630, the entire content of which is incorporated herein by reference.

[0136] In some embodiments, the radiating element 400 may further comprise a first printed circuit board 360, and the first signal trace 340-1 may be electrically connected to a first metal structure 364-1 on the first printed circuit board 360 and the second signal trace 340-2 may be electrically connected to a second metal structure 364-2 on the first printed circuit board 360. In some embodiments, first signal trace 340-1 may be an output trace 268 of a first phase shifter assembly 260 and may be directly electrically connected to the first printed circuit board 360.

[0137] In some embodiments, the radiating element 400 may further comprise a parasitic metal element 485 that is configured to capacitively couple with the first through fourth dipole arms 482-1 through 482-4. The parasitic metal element 485 may, for example, be a metal ring 486 having first through fourth metal plates 487-1 through 487-4 extending radially inwardly from the metal ring 486. The parasitic metal element 485 may include fifth through eighth metal plates 488-1 through 488-4 that extend outwardly from the metal ring 486. The fifth through eighth metal plates 488-1 through 488-4 may also include segments that extend rearwardly from the metal ring 486.

[0138] In some embodiments, the first through fourth dipole arms 482-1 through 482-4 extend radially outwardly from a central point and have respective longitudinal axes that extend at angles of 135⁰, 225⁰ and 315⁰ and 45⁰ and the fifth through eighth metal plates 488-1 throughAttorney Docket No.9833.7492.WO 488-4 extend radially outwardly from the respective first through fourth metal plates 487-1 through 487-4.

[0139] In some embodiments, the first metal ground plate 324-1 extends in a first plane and the second metal ground plate 324-4 extends in a second plane that is perpendicular to the first plane. In some embodiments, the first signal trace 340-1 comprises an output trace 268 of a first phase shifter assembly 260-1 and the second signal trace 340-2 comprises an output trace 268 of a second phase shifter assembly 260-2. In some embodiments, the radiating element 400 may further comprise a first printed circuit board 360, and the first signal trace 340-1 may be galvanically connected to a first metal structure 364-1 on the first printed circuit board 360 and the second signal trace 340-2 may be galvanically connected to a second metal structure 364-2 on the first printed circuit board 360. In some embodiments, the parasitic metal element 485 may be configured to capacitively couple with the first through fourth dipole arms 482-1 through 482-4. In some embodiments, the first printed circuit board 360 is positioned forwardly of the first and second dipole radiators 482-1, 482-2 and rearwardly of the parasitic metal element 485. In some embodiments, the parasitic metal element 485 may have a footprint that is larger than the openings 112 in the reflector 110.

[0140] FIG.7 is a schematic end view of an alternative metal housing 230A according to further embodiments of the present invention that may be used in place of metal housing 230 in for the cavity phase shifters 220 of FIG.2B. As shown in FIG.7, longitudinally-extending inward lips 239A1 may be provided at the rear edge of the first and second main sidewalls 234-1, 234-2 and / or longitudinally-extending outward lips 239A2 may be provided at the rear edge of the inner sidewall 236. These lips 239A1, 239A2 may decrease the size of the opening in the rear of each cavity 240-1, 240-2, which may reduce insertion loss and / or may help reduce or eliminate resonances that may arise due to the presence of an opening in the rear of the cavities 240. An opening is still provided into each cavity 240-1, 240-2 between the lips 239A1, 239A2 so that the phase shifter printed circuit boards 262 (with the elongated, forwardly-extending output traces 268) may still be slid into the cavities 240 from the rear. In some embodiments, a separate, longitudinally-extending piece of metal (not shown) may be provided that may be used to cover the openings into the rear of the cavities 240. This separate piece of metal may be configured to capacitively couple with the metal shell 230 and may help further mitigate resonance issues and / or reduce the insertion loss.Attorney Docket No.9833.7492.WO

[0141] FIG.8 is a schematic end view of a second alternative metal housing 230B according to further embodiments of the present invention that may alternatively be used in place of metal housing 230 in for the cavity phase shifters 220 of FIG.2B. As can be seen by comparing FIGS.7 and 8, the two metal housings 230A, 230B are very similar to each other, except that metal housing 230A has the openings into each cavity 240 in the rear whereas metal housing 230B has the openings into each cavity 240 in the front wall 232, and includes full rear walls for each cavity 240. Thus, with metal housing 230B, the phase shifter printed circuit boards 262 are inserted from the front into the respective cavities 240-1, 240-2. As other aspects of metal housing 230B may be the same as metal housings 230, 230A, further description thereof will be omitted here.

[0142] The mid-band linear array assemblies according to embodiments of the present invention may have advantages over conventional mid-band linear arrays. First, since the mid- band linear array assemblies 200 are modular components, they can be almost completely assembled before they are installed in the base station antenna 100. This simplifies the manufacturing process. Second, since the sheet metal dipole arms 380 and directors 390 of the mid-band radiating elements 300 may be removably attached to the remainder of the mid-band linear array assembly 200 before the mid-band linear array assembly 200 is installed in the base station antenna 100, the entire assembly 200 may be pre-tested before it is installed in the antenna 100. Third, since the mid-band linear array assembly 200 is modular in nature if problems are identified later during antenna level testing, the mid-band linear array assembly 200 can readily be removed from the base station antenna 100 without removing various other components, making it much easier to fix problems (e.g., poor solder joints) detected during antenna level testing. Fourth, since the output traces 268 of the phase shifter assemblies 260 act as the signal traces for the mid-band radiating elements 300, the mid-band radiating elements 300 may be assembled with a total of only two solder joints in some embodiments, namely a solder joint that connects each signal trace 340 to the metal structures 364 on the first printed circuit board 360. The reduction in solder joints simplifies manufacture of the radiating elements 300, and also removes potential sources of PIM distortion since less solder joints are used. Fifth, since the mid-band radiating elements 300 include common mode rejection circuits, they may have reduced impact on nearby low-band radiating elements 22.Attorney Docket No.9833.7492.WO

[0143] Simulation results show the mid-band radiating elements 300 exhibit a return loss of less than -30 dB across the entire 1427-2690 MHz mid-band operating frequency range, with an average return loss of -37 dB. Simulation results also show the mid-band radiating element has a good azimuth half power beamwidth ("HPBW"), with the average azimuth HPBW being about 64⁰ and the variation in azimuth HPBW being about 20⁰ across the full 1427-2690 MHz operating frequency range. The (simulated) generated antenna beams also exhibit good cross-polarization discrimination (less than -15 dB) and low side lobe levels (less than -19 dB).

[0144] The present invention has been described above with reference to the accompanying drawings. The present invention is not limited to the illustrated embodiments. Rather, these embodiments are intended to fully and completely disclose the present invention to those skilled in this art. In the drawings, like numbers refer to like elements throughout. Thicknesses and dimensions of some components may be exaggerated for clarity.

[0145] Spatially relative terms, such as "under," "below," "lower," "over," "upper," "top," "bottom," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "under" or "beneath" other elements or features would then be oriented "over" the other elements or features. Thus, the example term "under" can encompass both an orientation of over and under. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0146] Herein, the terms "attached," "connected," "interconnected," "contacting," "mounted," "coupled," and the like can mean either direct or indirect attachment or coupling between elements, unless stated otherwise.

[0147] 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.

[0148] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless theAttorney Docket No.9833.7492.WO context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes," and / or "including" when used in this specification, specify the presence of stated features, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, operations, elements, components, and / or groups thereof.

Claims

Attorney Docket No.9833.7492.WO CLAIMS:

1. A radiating element, comprising: a feed stalk that comprises a metal ground stalk that has a base and a distal end that are spaced apart from each other in a first direction and a first signal trace extending in the first direction adjacent the metal ground stalk; and a radiator assembly that is mounted adjacent the distal end of the metal ground stalk, wherein the first signal trace comprises an output trace of a first phase shifter assembly and directly electrically connects to the radiator assembly.

2. The radiating element of Claim 1, wherein the metal ground stalk comprises a first plate that has a longitudinal axis that extends in the first direction and a second plate that is at the base of the metal ground stalk, the second plate having a major surface that extends in a second direction and a third direction that are perpendicular to each other and to the first direction.

3. The radiating element of Claim 2, wherein the metal ground stalk further comprises a third plate that extends in the second direction and the third direction.

4. The radiating element of Claim 3, wherein the third plate is at the distal end of the metal ground stalk.

5. The radiating element of Claim 3, wherein the metal ground stalk comprises a first metal piece and a second metal piece, and wherein the first, second and third metal plates are each part of the first metal piece, the first metal piece further comprising a fourth plate that extends in the first direction and a fifth plate that extends in the second direction and the third direction, where the fifth plate is coplanar with the third plate.

6. The radiating element of Claim 5, wherein the second metal piece comprises a sixth plate and a ninth plate that each have a longitudinal axis that extends in the first direction, a seventh plate that extends in the second direction and the third direction at the base of the metal ground stalk, and an eighth plate and a tenth plate that each extend in the second direction and the third direction.Attorney Docket No.9833.7492.WO 7. The radiating element of Claim 6, wherein the eighth plate and the tenth plate are coplanar with the third plate and the fifth plate.

8. The radiating element of Claim 6, wherein the radiating element further comprises a second signal trace extending in the first direction adjacent the metal ground stalk to directly electrically connect to the radiator assembly, where the second signal trace comprises an output trace of a second phase shifter assembly.

9. The radiating element of Claim 8, wherein the first signal trace extends through at least a first opening in the first metal piece and the second signal trace extends through at least a first opening in the second metal piece.

10. The radiating element of Claim 6, wherein the first plate extends in a first plane and the fourth plate extends in a second plane that is perpendicular to the first plane.

11. The radiating element of Claim 6, wherein the third plate, the fifth plate, the eighth plate and the tenth plate each extend in a third plane.

12. The radiating element of Claim 11, wherein the second plate and the seventh plate each extend in a fourth plane that is parallel to the third plane.

13. The radiating element of Claim 6, wherein the sixth plate extends in a fifth plane that is perpendicular to the first plane.

14. The radiating element of any of Claims 1-13, wherein the radiator assembly comprises a first printed circuit board that is galvanically coupled to the first signal trace.

15. The radiating element of Claim 14, wherein the radiator assembly further comprises a second printed circuit board that includes a plurality of metal pads that are capacitively coupled to the metal ground stalk.

16. The radiating element of Claim 15, wherein the radiator assembly further comprises a plurality of sheet metal dipole arm pieces that are capacitively coupled to the respective metal pads on the second printed circuit board.Attorney Docket No.9833.7492.WO 17. The radiating element of Claim 15, wherein the first printed circuit board is mounted forwardly of the second printed circuit board.

18. The radiating element of any of Claims 1-13, wherein the first phase shifter assembly is at least partially mounted within a metal housing that has a front wall, and wherein the first signal trace extends through an opening in the front wall.

19. The radiating element of Claim 18, wherein a rear of the metal housing is at least partially open to allow a printed circuit board of the phase shifter assembly to be inserted into the metal housing from the rear.

20. The radiating element of any of Claims 1-13, wherein the radiating element is part of a base station antenna that comprises a reflector that includes an opening that is larger than a footprint of the metal ground stalk.

21. A radiating element, comprising: a feed stalk that comprises: a metal ground stalk that has a base and a distal end that are spaced apart from each other in a first direction; and a first signal trace extending in the first direction adjacent the metal ground stalk; and a radiator assembly, comprising: a first printed circuit board that is mounted forwardly of the metal ground stalk; a second printed circuit board; and a first sheet metal dipole arm piece.

22. The radiating element of Claim 21, wherein the first printed circuit board is mounted on the first signal trace.

23. The radiating element of Claim 21, wherein the first signal trace is soldered to a first metal structure on the first printed circuit board.

24. The radiating element of Claim 21, wherein the metal ground stalk is capacitively coupled to a first metal pad on the second printed circuit board.Attorney Docket No.9833.7492.WO 25. The radiating element of Claim 21, wherein the radiator assembly further comprises a second sheet metal dipole arm piece, a third sheet metal dipole arm piece and a fourth sheet metal dipole arm piece, and the second printed circuit board further comprises a second metal pad, a third metal pad and a fourth metal pad, and wherein the first through fourth sheet metal dipole arm pieces are capacitively couped to the respective first through fourth metal pads.

26. The radiating element of any of Claims 21-25, wherein the metal ground stalk comprises a first plate that has a longitudinal axis that extends in the first direction and a second plate that is at the base of the metal ground stalk, the second plate extending in a second direction and a third direction that are perpendicular to each other and to the first direction.

27. The radiating element of Claim 26, wherein the metal ground stalk further comprises a third plate that extends in the second direction and the third direction.

28. The radiating element of Claim 27, wherein the metal ground stalk comprises a first metal piece and a second metal piece, and wherein the first, second and third metal plates are each part of the first metal piece, the first metal piece further comprising a fourth plate that extends in the first direction and a fifth plate that is coplanar with the third metal plate.

29. The radiating element of Claim 28, wherein the second metal piece comprises a sixth plate and a ninth plate that each have a longitudinal axis that extends in the first direction, a seventh plate that extends in the second direction and the third direction at the base of the metal ground stalk, and an eighth plate and a tenth plate that are coplanar with the third metal plate and the fifth metal plate.

30. The radiating element of Claim 29, wherein the radiating element further comprises a second signal trace extending in the first direction adjacent the metal ground stalk to directly electrically connect to the radiator assembly, where the second signal trace comprises an output trace of a second phase shifter assembly.

31. The radiating element of Claim 30, wherein the first signal trace extends through at least a first opening in the first metal piece and the second signal trace extends through at least a first opening in the second metal piece.Attorney Docket No.9833.7492.WO 32. The radiating element of Claim 29, wherein the first plate extends in a first plane and the fourth plate extends in a second plane that is perpendicular to the first plane.

33. The radiating element of Claim 29, wherein the third plate, the fifth plate, the eighth plate and the tenth plate each extend in a third plane.

34. The radiating element of Claim 29, wherein the first signal trace comprises an output trace of a first phase shifter assembly and directly electrically connects to the radiator assembly.

35. A radiating element, comprising: a first monolithic sheet metal piece that includes first and second ground plates and first and second dipole arms extending from distal ends of the first and second ground plates; a second monolithic sheet metal piece that includes third and fourth ground plates and third and fourth dipole arms extending from distal ends of the third and fourth ground plates; wherein the first and second dipole arms form a first dipole radiator and the third and fourth dipole arms form a second dipole radiator.

36. The radiating element of Claim 35, further comprising a first signal trace mounted adjacent the first ground plate and a second signal trace mounted adjacent the third ground plate.

37. The radiating element of Claim 36, further comprising a first printed circuit board that is mounted on the first and second signal traces.

38. The radiating element of Claim 37, wherein the first printed circuit board is mounted forwardly of the first and second dipole radiators.

39. The radiating element of Claim 38, further comprising a parasitic metal element mounted forwardly of the first printed circuit board.

40. The radiating element of Claim 39, wherein the parasitic metal element comprises a parasitic metal ring.

41. The radiating element of Claim 40, wherein the parasitic metal ring is capacitively coupled to the first through fourth dipole arms.Attorney Docket No.9833.7492.WO 42. The radiating element of Claim 41, further comprising a director mounted forwardly of the parasitic metal element.

43. The radiating element of Claim 42, further comprising a meta director mounted forwardly of the director.

44. The radiating element of Claim 43, wherein the meta director comprises a printed circuit board that comprises a plurality of unit cell metal structures.

45. The radiating element of any of Claims 36-44, further comprising a first printed circuit board, wherein the first signal trace is electrically connected to a first metal structure on the first printed circuit board and the second signal trace is electrically connected to a second metal structure on the first printed circuit board.

46. The radiating element of Claim 37, wherein the first signal trace comprises an output trace of a first phase shifter assembly and directly electrically connects to the first printed circuit board.

47. The radiating element of any of Claims 35-44, further comprising a parasitic metal element that is configured to capacitively couple with the first through fourth dipole arms.

48. The radiating element of Claim 47, wherein the parasitic metal element comprises a metal ring having first through fourth metal plates extending radially inwardly from the metal ring.

49. The radiating element of Claim 47, wherein the parasitic metal element comprises a metal ring having fifth through eighth metal plates extending outwardly from the metal ring.

50. The radiating element of Claim 49, wherein the fifth through eighth metal plates extend rearwardly from the metal ring.

51. The radiating element of Claim 48, wherein the first through fourth dipole arms extend radially outwardly from a central point and have respective longitudinal axes that extend at angles of 45⁰, 135⁰, 225⁰ and 315⁰, and the fifth through eighth metal pads extend radially outwardly from the respective first through fourth metal plates.Attorney Docket No.9833.7492.WO 52. The radiating element of any of Claims 35-44, wherein the first ground plate extends in a first plane and the second ground plate extends in a second plane that is perpendicular to the first plane.

53. The radiating element of Claim 36, wherein the first signal trace comprises an output trace of a first phase shifter assembly and the second signal trace comprises an output trace of a second phase shifter.

54. The radiating element of Claim 53, further comprising a first printed circuit board, wherein the first signal trace is galvanically connected to a first metal structure on the first printed circuit board and the second signal trace is galvanically connected to a second metal structure on the first printed circuit board.

55. The radiating element of Claim 54, further comprising a parasitic metal element that is configured to capacitively couple with the first through fourth dipole arms.

56. The radiating element of Claim 55, wherein the first printed circuit board is positioned forwardly of the first and second dipole radiators and rearwardly of the parasitic metal element.

57. The radiating element of Claim 56, wherein the parasitic metal element comprises a metal ring having first through fourth metal plates extending radially inwardly from the metal ring.

58. The radiating element of Claim 35 in combination with a base station antenna that includes a reflector having an opening that is aligned with the radiating element, wherein the opening is larger than a footprint of the first and second dipole radiators, the radiating element further comprising a parasitic metal element that is configured to capacitively couple with the first and second dipole radiators, wherein a footprint of the parasitic metal element is larger than the opening.

59. A cavity phase shifter assembly, comprising:Attorney Docket No.9833.7492.WO a monolithic metal housing that comprises a front wall and first and second sidewalls that extend rearwardly from the front wall, the front wall and the first and second side walls defining a first cavity; and a phase shifter assembly at least partly mounted in the first cavity, wherein a rear side of the first cavity is at least partially open.

60. The cavity phase shifter of Claim 59, wherein the phase shifter assembly is configured to be inserted into the first cavity from the rear side of the first cavity.

61. The cavity phase shifter of Claim 59, wherein the front wall includes a plurality of openings, and forwardly extending output traces of the phase shifter assembly are configured to be inserted through the respective openings when the phase shifter assembly is mounted in the first cavity.

62. The cavity phase shifter of any of Claims 59-61, wherein a rear side of the first cavity is fully open.

63. The cavity phase shifter of any of Claims 59-61, wherein the first sidewall includes an inwardly extending lip that partially encloses the rear side of the first cavity.

64. The cavity phase shifter of Claim 63, wherein the second sidewall includes an inwardly extending lip, and a slot is defined in between the first and second inwardly extending lips.

65. The cavity phase shifter of any of Claims 59-61, wherein the first cavity has first and second open ends.

66. The cavity phase shifter of Claim 61, wherein the phase shifter assembly comprises a main phase shifter printed circuit board, and portions of each output trace that extend through the respective openings each have a length in the forward direction that is at least one-quarter of a length of the first sidewall in the forward direction.

67. The cavity phase shifter of Claim 66, wherein portions of each output trace that extend through the respective openings each have a length in the forward direction that is at least one-third of the length of the first sidewall in the forward direction.Attorney Docket No.9833.7492.WO 68. The cavity phase shifter of Claim 61 in combination with a plurality of radiating elements, wherein each output trace comprises a signal trace of a respective one of the radiating elements.

69. The cavity phase shifter of Claim 68, wherein each radiating element includes a radiator assembly, and each output trace is directly electrically connected to the radiator assembly.

70. The cavity phase shifter of Claim 69, wherein each radiator assembly includes a printed circuit board, and each output trace is soldered to a respective metal structure on the respective printed circuit boards.

71. A cavity phase shifter assembly, comprising: a longitudinally-extending monolithic metal housing that defines a first cavity that has longitudinally-extending first and second sidewalls; and a phase shifter that comprises a main printed circuit board, wherein a rear of the first cavity includes a longitudinally-extending opening that is configured to receive the main printed circuit board.

72. The cavity phase shifter of Claim 71, wherein the main printed circuit board includes a plurality of forwardly-extending output traces.

73. The cavity phase shifter of Claim 72, wherein the monolithic metal housing includes a front wall and the first and second sidewalls extend rearwardly from the front wall, and wherein the front wall includes a plurality of openings and the forwardly-extending output traces extend through the respective openings.

74. The cavity phase shifter of Claim 73, wherein portions of each output trace that extend through the respective openings each have a length in the forward direction that is at least one-quarter of a length of the first sidewall in the forward direction.

75. The cavity phase shifter of Claim 73, in combination with a plurality of radiating elements, wherein each output trace comprises a signal trace of a respective one of the radiating elements.Attorney Docket No.9833.7492.WO 76. The cavity phase shifter of Claim 75, wherein each radiating element includes a radiator assembly, and each output trace is directly electrically connected to the radiator assembly.

77. The cavity phase shifter of Claim 76, wherein each radiator assembly includes a printed circuit board, and each output trace is soldered to a respective metal structure on the respective printed circuit boards.

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