RADIATING ELEMENTS FOR BASE STATION ANTENNAS HAVING SOLDERLESS

CONNECTIONS

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to U.S. Provisional Patent Application Serial No. 63/166,596, filed March 26, 2021, the entire content of which is incorporated herein by reference.

BACKGROUND

[0002] The present invention generally relates to radio communications and, more particularly, to radiating elements for base station antennas used in cellular communications systems

[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. In many cases, each base station is divided into "sectors." In perhaps the most common configuration, a hexagonally shaped-cell is divided into three 120° sectors, and each sector is served by one or more base station antennas that have an azimuth Half Power Beamwidth (HPBW) of approximately 65°. 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. Base station antennas are often implemented as linear or planar phased arrays of radiating elements.

[0004] With the introduction of various fourth generation ("4G") and fifth generation ("5G") cellular technologies, base station antennas are now routinely being deployed that have multi-input-multi-output ("MIMO") and/or active beamforming capabilities. MIMO refers to a technique where a baseband data stream is sub-divided into multiple sub-streams that are used to generate multiple RF signals that are transmitted through multiple different antenna arrays. In some cases, as many as eight, sixteen, thirty-two or sixty-four different sub-streams may be used (when large number of MIMO transmission paths are used, the technique is often referred to as "massive MIMO"). The antenna arrays are, for example, spatially separated from one another and/or at orthogonal polarizations so that the transmitted RF signals will be sufficiently decorrelated. The multiple RF signals are recovered at the receiver and demodulated and decoded to recover the original data sub-streams, which are then recombined. Active beamforming refers to transmitting RF signals through a multi-column array of radiating elements in which the amplitude and/or phase of the sub-components of an RF signal that are transmitted through the different radiating elements of the array are adjusted in the radio to form a more directive antenna beam that has higher gain. The multi-column arrays that are used to implement both massive MIMO and active beamforming tend to have large numbers of radiating elements, however, which can increase the cost and complexity of the antenna.

SUMMARY

[0005] Pursuant to embodiments of the present invention, feed board assemblies for base station antennas are provided that include a feed board and a radiating element that is separate from the feed board, the radiating element including a feed line. The feed line of the radiating element is electrically connected to the feed board via a first solderless connection.

[0006] In some embodiments, the radiating element may be mounted to extend forwardly from the feed board, and the feed line may be galvanically connected to the feed board.

[0007] In some embodiments, the first solderless connection may be a spring-biased connection between the feed line and a conductive structure (e.g., a feed trace) on the feed board.

[0008] In some embodiments, the spring-biased connection may be a pogo pin connection or a resilient conductive pad. [0009] In some embodiments, the radiating element may be a cross-dipole radiating element that includes a plurality of dipole arms and a stalk that mounts the dipole arms forwardly of the feed board. In some embodiments, the feed line and the stalk may together form a radio frequency transmission line. In some embodiments, the stalk may be electrically connected to a ground plane of the base station antenna via a second solderless connection. The ground plane may be, for example, a ground plane of the feed board or a reflector of the base station antenna. The second solderless connection may be a spring-biased connection between the stalk and the ground plane. In some embodiments, the stalk includes first and second interior channels, and the feed line comprises a first hook balun that extends through the first interior channel, the radiating element further including a second feed line in the form of a second hook balun that extends through the second interior channel. A dielectric material may be interposed between the first interior channel and the first hook balun.

[0010] In some embodiments, the feed board further may include a calibration circuit that has a plurality of calibration couplers.

[0011] In some embodiments, the feed board may be mounted rearwardly of a reflector of the base station antenna, and a stalk of the radiating element may be electrically connected to the reflector via a second solderless connection.

[0012] In other embodiments, the radiating element may be a patch radiating element.

[0013] Pursuant to further embodiments of the present invention, radiating elements for a base station antenna are provided that include a first dipole that includes a first dipole arm and a second dipole arm and a hook balun that includes a first longitudinally-extending segment, a second longitudinally-extending segment, and a transversely-extending segment that electrically connects the first longitudinally-extending segment to the second longitudinally-extending segment. The first longitudinally-extending segment includes a spring.

[0014] In some embodiments, the spring may be part of a pogo pin connector.

[0015] In some embodiments, the radiating element is provided in combination with a feed board and a reflector of a base station antenna, where the radiating element includes a stalk that mounts the first and second dipole arms forwardly of the feed board. In some embodiments, the first longitudinally-extending segment may be connected to a feed trace on the feed board via a first solderless connection and/or the stalk is electrically connected to a ground plane of the base station antenna via a second solderless connection. The ground plane may be the reflector or a ground plane of the feed board. The stalk may be electrically connected to the ground plane via a resilient conductive pad in some embodiments. In some cases, the feed board may be mounted rearwardly of the reflector.

[0016] Pursuant to still further embodiments of the present invention, base station antennas are provided that include a reflector having a plurality of openings, a feed board mounted behind the reflector; and an array of radiating elements that extend forwardly from the reflector. At least some of the radiating elements extend through respective ones of the openings in the reflector to physically contact the feed board and to electrically connect to the feed board via a solderless galvanic connection.

[0017] In some embodiments, the solderless galvanic connection may be a spring-biased connection between a first of the radiating elements and a conductive structure on the feed board.

[0018] In some embodiments, the conductive structure may be a feed trace on the feed board.

[0019] In some embodiments, the spring-biased connection may be a pogo pin connection or a resilient conductive pad.

[0020] In some embodiments, the first of the radiating elements may be a cross-dipole radiating element that includes a feed line, a plurality of dipole arms, and a stalk that mounts the dipole arms forwardly of the feed board. In some embodiments, the feed line and the stalk together form a radio frequency transmission line. In some embodiments, the stalk may be electrically connected to a ground plane of the base station antenna (e.g., the reflector) via a solderless connection.

[0021] In some embodiments, the stalk may include first and second interior channels, and the feed line may be a first hook balun that extends through the first interior channel, the first of the radiating elements further including a second feed line in the form of a second hook balun that extends through the second interior channel.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. l is a front perspective view of a base station antenna according to embodiments of the present invention.

[0023] FIG. 2 is a schematic front view of the base station antenna of FIG. 2 with the radome removed. [0024] FIG. 3 A is a schematic side view of a feed board assembly for a base station antenna that includes a pair of radiating elements having solderless electrical connections to the feed board printed circuit board.

[0025] FIG. 3B is a schematic cross-sectional view of an example feed line according to embodiments of the present invention.

[0026] FIG. 4 is a perspective view of a dipole/stalk assembly of a radiating element according to embodiments of the present invention.

[0027] FIGS. 5A-5C are perspective views that illustrate a feed structure that may be mated with the dipole/stalk assembly of FIG. 4 A to form a radiating element according to embodiments of the present invention.

[0028] FIGS. 6 A and 6B are front and rear perspective views, respectively, of an assembled radiating element according to embodiments of the present invention that includes the dipole/stalk assembly of FIG. 4 and the feed structure of FIG. 5C.

[0029] FIG. 6C is a front shadow perspective view of the radiating element of FIGS. 6A- 6B.

[0030] FIGS. 7 A and 7B are front and rear perspective views, respectively, of the radiating element of FIGS. 6A-6C mounted on a feed board to form a feed board assembly according to embodiments of the present invention.

[0031] FIG. 7C is an enlarged front view of a small portion of the feed board that illustrates the ground pads and conductive vias in the feed board of FIGS. 7A-7B.

[0032] FIG. 8 is a partial perspective view of an antenna including a 4x4 array of the feed board assemblies of FIGS. 7A-7B.

[0033] FIG. 9A is a shadow perspective view of a modified version of the radiating element of FIGS. 6A-6C.

[0034] FIG. 9B is a perspective view of the two hook baluns included in the radiating element of FIG. 9 A.

[0035] FIG. 10 is a schematic perspective view of a sheet metal based radiating element that includes a solderless feed line connection to a feed board.

[0036] FIG. 11 is a perspective view illustrating how a conventional hook balun may be used in conjunction with a conductive spring pad to form a radiating element according to further embodiments of the present invention. [0037] FIG. 12A is a perspective front view of a radiating element according to further embodiments of the present invention that connects to a feed board positioned behind the reflector.

[0038] FIG. 12B is a perspective rear view of the radiating element of FIG. 12A and a portion of the reflector

[0039] FIG. 12C is an enlarged shadow front perspective view of the radiating element of FIG. 12A illustrating the hole in the reflector that exposes the feed board behind the reflector.

[0040] Note that herein when multiple like elements are provided, the elements may be identified by two-part reference numerals. The full reference numeral (e.g., linear array 30-2) may be used to refer to an individual element, while the first portion of the reference numeral (e.g., the linear arrays 30) may be used to refer to the elements collectively.

DETAILED DESCRIPTION

[0041] The use of massive MIMO communication techniques and/or active beamforming can greatly increase the throughput supported by a base station antenna. However, the multi-column arrays of radiating elements that are used to implement massive MIMO and active beamforming may significantly increase the size, cost and/or complexity of a base station antenna. For example, the multi-column arrays used for massive MIMO and active beamforming often include four or eight columns that each have six to twelve radiating elements. The radiating elements are physically mounted on feed boards that typically include 1-3 radiating elements each. The radiating elements are electrically connected to the feed boards via solder joints. For cross-dipole radiating elements, four solder joints are typically provided, namely a solder joint for each of the two feed lines and solder joints for two ground connections.

Mounting many dozens of radiating elements onto feed boards to form a multi-column array may thus be a very involved process.

[0042] Solder joints are typically used to electrically connect radiating elements to feed boards because they may increase the structural integrity of the mechanical connection while also providing a high-quality electrical connection that may not be a significant source of passive intermodulation ("PIM") distortion. PIM distortion is a form of electrical interference that may occur when two or more RF signals encounter non-linear electrical junctions or materials along an RF transmission path. PIM distortion may be caused by, for example, inconsistent metal-to- metal contacts along an RF transmission path, that may occur, for example, because of contaminated and/or oxidized signal carrying surfaces, loose connections between two connectors, and/or poorly prepared soldered connections. Such non-linearities may act like a mixer causing the RF signals to generate new RF signals (which are called intermodulation products) at mathematical combinations of the original RF signals. These intermodulation products may appear as noise to other RF signals transmitted through the antenna. PIM generated by a single low-quality interconnection may degrade the electrical performance of the entire RF communications system.

[0043] Cellular operators typically place strict requirements on the levels of PIM distortion that may be generated along the RF paths in a base station antenna. In base station antennas that operate using frequency division duplexing ("FDD"), the PIM distortion requirements may be very strict, as even small amounts of PIM distortion generated along a high-power transmit path that fall within the bandwidth of the much lower power received signals may severely degrade communications quality. With the introduction of 5G service, some base station antennas may include arrays that operate using time division duplexing ("TDD"). Generally speaking, higher levels of PIM distortion may be acceptable in such TDD systems as the transmit and receive operations may be performed in different time slots. For example, the PIM distortion requirements for a TDD system may be 5-13 dBc higher than for a corresponding FDD system.

[0044] Pursuant to embodiments of the present invention, radiating elements and associated base station antennas are provided that have solderless connections to their associated feed boards. These solderless connections may, in some cases, be more likely to generate PIM distortion, but since heightened levels of PIM distortion may be acceptable in some antennas (e.g., TDD antennas), the increased PIM distortion risk may be acceptable. Moreover, by eliminating the soldered connections, the fabrication of the antennas according to embodiments of the present invention may be greatly simplified.

[0045] In some embodiments, spring-biased connectors such as, for example, pogo-pin style connectors may be used to physically and electrically connect conductive elements of the radiating elements to corresponding conductive elements on a feed board or other surface. Resilient conductive gaskets may additionally or alternatively be used to make some or all of the electrical connections. In other embodiments, dielectric spacers may be interposed between conductive elements of the radiating elements and corresponding conductive elements on the feed boards or other structures so that the radiating elements are capacitively coupled to the feed boards. In either case, support structures may hold the radiating elements firmly to the feed boards to ensure that consistent electrical connections are maintained.

[0046] In some embodiments, the feed boards may be mounted behind a reflector of the base station antenna, and the radiating elements may be mounted to the feed boards through openings in the reflector. For example, a calibration circuit board for the base station antenna that is positioned behind the reflector may also be used as a feed board for the radiating elements. Feed traces on the calibration board may be coupled to feed lines on the radiating elements that extend through the openings in the reflector to contact the calibration board. In some embodiments, ground connections on each radiating element may be connected to the reflector.

[0047] In some embodiments, the radiating elements may comprise cross dipole radiating elements. In some such embodiments, each radiating element may include a die cast structure that forms the stalks and the dipole arms of the radiating element. In other embodiments, the radiating elements may be formed at least primarily of stamped sheet metal.

In still other embodiments, at least a portion of the radiating element may be formed using printed circuit boards (e.g., the stalk and/or the radiators). In yet further embodiments, the radiating elements may comprise patch radiating elements.

[0048] Embodiments of the present invention will now be discussed in greater detail with reference to the accompanying figures.

[0049] FIGS. 1 and 2 illustrate a base station antenna 10 according to certain embodiments of the present invention. In particular, FIG. l is a front perspective view of the base station antenna 10, and FIG. 2 is a front view of the base station antenna 10 with the radome thereof removed to illustrate the inner components of the base station antenna. The base station antenna 10 may, for example, be designed to provide coverage to a 120° sector of a base station.

[0050] As shown in FIG. 1, the base station antenna 10 is an elongated structure that extends along a longitudinal axis L. The base station antenna 10 may have a tubular shape with a generally rectangular cross-section. The base station antenna 10 includes a radome 12 and a top end cap 14, which may or may not be integral with the radome 12. The base station antenna 10 also includes a bottom end cap 16 which includes a plurality of RF connectors 18 mounted therein. The base station antenna 10 is typically mounted in a vertical configuration (i.e., the longitudinal axis L may be generally perpendicular to a plane defined by the horizon when the base station antenna 10 is mounted for normal operation).

[0051] As shown in FIG. 2, the base station antenna 10 includes an antenna assembly 20 that may, for example, be slidably inserted within the radome 12. The antenna assembly 20 includes a backplane 22. Various mechanical and electronic components of the antenna may be mounted behind the backplane 22 such as, for example, phase shifters, remote electronic tilt ("RET") units, mechanical linkages, a controller, diplexers, and the like. The backplane 22 may comprise or include a reflector 24 in the form of a metallic surface that serves as a ground plane for the radiating elements of the antenna 10 and that reflects RF radiation emitted backwardly by the radiating elements in the forward direction.

[0052] A pair of low-band linear arrays 30-1, 30-2 are positioned along the outer edges of the reflector 24 and extend substantially the entire length of the reflector 24. Each low-band linear array 30 includes a plurality of radiating elements 32 and a plurality of tri-pol radiating elements 34. The radiating elements 32 comprise slant -45°/+45° cross-dipole low-band radiating elements while the radiating elements 34 comprise tri-pol low-band radiating elements. The tri-pol low-band radiating elements 34 are used as the radiating elements in the upper portion of each low-band linear array 30 in order to open up more room in the upper middle portion of the reflector 24 for a multi-column array of high-band radiating elements 50 (discussed below). Each of the radiating elements 32, 34 is mounted on low-band feed boards 36 that are positioned forwardly of the reflector 24. Each of the radiating elements 32, 34 extends forwardly from its associated feed board 36. The low-band radiating elements 32, 34 may be configured to operate, for example, in all or part of the 617-960 MHz frequency band.

[0053] A pair of mid-band linear arrays 40-1, 40-2 are positioned along the lower center portion of the reflector 24. Each mid-band linear array 40 includes a plurality of radiating elements 42, which may be implemented as slant -45°/+45° cross-dipole mid-band radiating elements in example embodiments. Each of the mid-band radiating elements 42 are mounted on mid-band feed boards 46 that are positioned forwardly of the reflector 24 and extend forwardly from these feed boards 46. The mid-band radiating elements 42 may be configured to operate in, for example, all or part of the 1427-2690 MHz frequency band.

[0054] A multi-column high-band array 50 is positioned on the upper center portion of the reflector 24. The high-band array 50 comprises eight columns of high-band radiating elements 52, which may be implemented as slant -45°/+45° cross-dipole high-band radiating elements in example embodiments. Each of the high-band radiating elements 52 are mounted on high-band feed boards 56 that are positioned forwardly of the reflector 24 and extend forwardly from these feed boards 56. The high-band radiating elements 52 may be configured to operate in, for example, all or part of the 2300-2690 MHz frequency band, the 3.1-4.2 GHz frequency band, or the 5.1-5.9 GHz frequency band.

[0055] The feed boards 36, 46, 56 may comprise printed circuit boards. The printed circuit boards may comprise a dielectric substrate that has metallization patterns on each major surface thereof. For example, the metallization pattern on the rear surface of the printed circuit board may comprise a metal pattern that forms a ground plane and the metallization pattern on the front surface of the printed circuit board may comprise feed traces and power dividers. The radiating elements 32, 34, 42, 52 are mounted to extend forwardly from the printed circuit boards.

[0056] The feed boards of each linear array may be connected to a respective pair of the RF connectors 18 through a feed network of the base station antenna 10. For example, referring to linear array 30-1 of base station antenna 10, a first RF connector 18-1 (that receives an RF signal from a radio that is to be transmitted with a -45° polarization) may be connected to a first electromechanical phase shifter that subdivides the RF signal into a plurality of sub-components and applies an adjustable phase progression to the sub-components in order to apply a desired amount of electronic downtilt to the -45° polarization antenna beam formed by linear array 30-1 in response to the RF signal input at RF connector 18-1. Each output of the electromechanical phase shifter (which receive the respective phase shifted sub-components of the RF signal) is connected to a respective one of the feed boards 36 included in linear array 30-1. The sub component of the RF signal passed to each feed board 36 may then be further sub-divided (since each feed board 36 includes two or three radiating elements mounted thereon) by power dividers provided on the feed boards 36. RF transmission lines on the feed boards 36 that are connected to the outputs of the power divider(s) then feed the further sub-divided sub-components of the RF signal to the individual radiating elements 32, 34. A second RF connector 18-2 (that receives an RF signal from a radio that is to be transmitted with a +45° polarization) may similarly be connected to the feed boards 36 through a second electromechanical phase shifter in order to pass signals to the +45° radiators of the radiating elements 32, 34 mounted on the feed boards 36. [0057] Each low-band and mid-band linear arrays 30-1, 30-2, 40-1, 40-2 may be used to form a pair of antenna beams, namely a first antenna beam having a +45° polarization and a second antenna beam having a -45° polarization. It will be appreciated that the number of linear arrays of radiating elements may be varied from what is shown in FIG. 2, as may the number of radiating elements per linear array and/or the positions of the linear arrays.

[0058] As noted above, pursuant to some embodiments of the present invention, feed board assemblies for a base station antenna are provided that include a feed board and a radiating element that includes a feed line that is mounted to extend forwardly from the feed board. The feed line of the radiating element is electrically connected to the feed board via a first solderless connection. For example, any of the radiating elements 32, 34, 42, 52 of base station antenna 10 may have such solderless connections to their associated feed boards 36, 46, 56.

[0059] In some embodiments, the feed line may be galvanically connected to the feed board. For example, the first solderless connection may be a spring-biased galvanic connection between the feed line and a conductive structure such as a feed trace or a feed pad on the feed board. The spring-biased connection may be a pogo pin connection or a resilient conductive pad in some embodiments. Other spring-biased connections such as spring contacts may be used in alternative embodiments. In some embodiments, the radiating element may be a cross-dipole radiating element that includes a plurality of dipole arms and a stalk that mounts the dipole arms forwardly of the feed board. In such embodiments, the stalk may be electrically connected to a ground plane of the base station antenna (e.g., a ground plane of the feed board or a reflector of the antenna) via one or more second solderless connections. The second solderless connections may also be spring-biased connections. In an example embodiment, the second solderless connections may comprise resilient conductive gaskets that connect respective ground lines on the radiating elements to the ground plane.

[0060] FIG. 3 A is a schematic side view of a feed board assembly 100 for a base station antenna according to embodiments of the present invention that includes a pair of radiating elements 130-1, 130-2 having solderless electrical connections to a feed board printed circuit board 110. The feed board assembly 100 may, for example, be used to form the high-band radiating elements 52 and high-band feed boards 56 of base station antenna 10 of FIGS. 1-2.

[0061] The feed board 110 may comprise a printed circuit board that includes a dielectric substrate 112 with metallization formed on each major surface thereof. In particular, metal feed traces 114 may be provided on the front surface of the dielectric substrate 112 and a metal ground plane 120 may be formed on the rear surface of the dielectric substrate 112. The metal feed traces 114 and the ground plane form microstrip transmission lines that may be used to pass RF signals between the radiating elements 130 mounted on the feed board 110 and other components of the antenna (that may be electrically connected to the feed board 110 via, for example, coaxial cables). Metal feed pads 116 may optionally be formed on the front surface of the dielectric substrate 112 that are electrically connected to the respective metal feed traces 114. Each metal feed pad 116 may be wider than the metal feed traces 114 in order to provide a larger surface for electrically connecting to a corresponding feed line on a respective one of the radiating elements 130. Metal ground pads 118 may also be formed on the front surface of the dielectric substrate 112 that are electrically connected to the ground plane 120 on the rear surface of the dielectric substrate 112 via metal-plated or metal-filled through holes (not shown) that extend through the dielectric substrate 112. The metal ground pads 118 may be electrically connected to corresponding ground connections on the radiating elements 130.

[0062] As shown in FIG. 3 A, the feed board assembly 100 includes a printed circuit board ("feed board") 110 and a pair of radiating elements 130-1, 130-2. The radiating elements 130 are shown as being single polarized dipole radiating elements in order to simplify the drawing. It will be appreciated that the radiating elements 130 will typically be implemented as, for example, slant -45°/+45° cross-dipole radiating elements. Radiating elements 130-1 and 130- 2 may be identical to each other. In FIG. 3A, the first radiating element 130-1 and the second radiating element 130-2 are rotated 180° with respect to each other so that a first side of radiating element 130-1 is shown and a second, opposed side of radiating element 130-2 is shown.

[0063] Each radiating element 130 includes a pair of feed stalks 150, a dipole radiator 160 and a feed structure 170 in the form of a feed line that is implemented as a hook balun 180. Dipole radiator 160-1 includes a first pair of dipole arms 162-1, 162, and dipole radiator 160-2 includes a second pair of dipole arms 162-3, 162-4. Each feed stalk 150 is used to mount a respective one of the dipole arms 162 forwardly of the feed board 110 (note that in use the feed board assembly 100 would be rotated 90° from the orientation shown in FIG. 3 A so that the dipole arms 162 are mounted forwardly of feed board 110). Each hook balun 180 is electrically connected to the feed trace 114 of a corresponding RF transmission line on the feed board 110. [0064] As shown in the enlarged inset on the left side of FIG. 3 A, the hook balun 180 of radiating element 130-1 is coupled to a metal feed trace 114 (or feed pad 116) on the feed board 110 via a solderless connection 102. A wide variety of different solderless connections 102 may be used. In some embodiments, the solderless connection 102 may be a capacitive connection. For example, the hook balun 180 of radiating element 130-1 may be coupled to the feed trace 114 on the feed board 110 through a dielectric material (not shown). In other embodiments, the solderless connection 102 may be a galvanic (direct metal -to-metal) connection. For example, the hook balun 180 of radiating element 130-1 may be physically connected to the feed trace 114 on the feed board 110. In some embodiments, spring-loading may be applied to ensure that a consistent electrical connection is formed between the hook balun 180 of radiating element 130- 1 and the feed trace 114 on the feed board 110. This may help reduce the likelihood of PIM distortion generation at the connection. FIG. 3 A does not show the physical structure of the solderless connection 102, although example solderless connections will be shown in other of the figures.

[0065] Each feed stalk 150 is used to mount a respective one of the dipole arms 162 forwardly of the feed board 110. Each feed stalk 150 and its corresponding dipole arm 162 may comprise a monolithic structure. Each feed stalk 150 is electrically connected to a ground connection (e.g., a ground pad 118) on the feed board 110. As shown in the enlarged inset on the right side of FIG. 3 A, each feed stalk 150 may be coupled to a corresponding ground connection on the feed board 110 via a solderless ground connection 104. A wide variety of different solderless ground connections 104 may be used. In some embodiments, the solderless ground connection 104 may be a capacitive connection. For example, the feed stalk 150 may be coupled to the ground connection on the feed board 110 through a dielectric material. In other embodiments, the solderless ground connection 104 may be a galvanic connection. For example, the feed stalk 150 may be physically connected to the ground pad 118. In some embodiments, spring-loading may be applied to ensure that a consistent electrical connection is formed between the feed stalk 150 and the ground pad 118. This may help reduce the likelihood of PIM distortion generation at the connection. FIG. 3 A does not show the physical structure of the solderless ground connection 104, although example solderless ground connections will be shown in other of the figures. [0066] FIG. 3B is a schematic cross-sectional view of an example feed line 170 for a radiating element according to embodiments of the present invention. As shown in FIG. 3B, the feed line is in the form of a hook balun 180. The hook balun 180 includes a fixed portion 172 and a spring-loaded portion 174. The fixed portion 172 may comprise, for example, a metal member that forms the hook portion of the hook balun 180. The spring-loaded portion 174 may comprise a spring-loaded member in some embodiments. The fixed portion 172 and the spring- loaded portion 174 of hook balun 180 may be held together by mating features (not shown) or may be held together by a separate support structure (not shown). In either case, the hook balun 180 may operate as if it were a single conductive structure.

[0067] In FIG. 3B, the spring-loaded portion 174 of the hook balun 180 is implemented as a pogo pin connector 190. The pogo pin connector 190 may comprise a tubular structure that includes at least a barrel 191, a plunger 194 and a spring 197. The barrel 191 includes a widened portion 192 and a narrowed portion 193 (which may comprise an inner lip) and the plunger 194 likewise includes a widened portion 195 (which may also be a lip) and a narrowed portion 196. The widened portion 195 of the plunger 194 is received within the widened portion 192 of the barrel 191, and the narrowed portion 196 of the plunger 194 extends out of the barrel 191. The narrowed portion 193 of the barrel 191 is narrower than the widened portion 195 of the plunger 194 and hence traps the widened portion 195 of the plunger 194 within the interior of the barrel 191. The spring 197 is also mounted within the barrel 191. When an upward force is applied to the plunger 194, the spring 197 is compressed and the plunger 194 moves further into the barrel 191. The spring 197 applies a downward force on the plunger 194.

[0068] As shown in FIG. 3B, the distal end of the plunger 194 may rest on a metal structure on the feed board 110 such as a feed pad 116 or a feed trace 114. The mating features on the fixed and spring-loaded portions 172, 174 of the hook balun 180 or the separate support structure may maintain the pogo pin connector 190 in a compressed position once the hook balun 180 is installed within the radiating element 130. The spring 197 within the pogo pin connector 190 may exert a downward force on the plunger 194 that maintains the plunger 194 in firm contact with the metal structure 114/116 on the feed board 110. This may ensure that a relatively low-PIM distortion electrical contact is formed between the feed line 170 and the feed board 110.

[0069] It will be appreciated that the pogo pin connector 190 shown in FIG. 3B is merely an example of one possible spring-loaded member that may be used to electrically connect the radiating elements 130 to the feed board 110. It will also be appreciated that a wide variety of pogo pin designs may be used. For example, a double-plunger pogo pin connector could be used that has plungers inserted into either side of the barrel in other embodiments. It will also be appreciated that the pogo pin connector 190 could be rotated 180° from the orientation shown in FIG. 3B so that the barrel 191 contacts the metal structure 114/116 on the feed board 110.

[0070] FIGS. 4-6C illustrate a cross-dipole radiating element 230 according to embodiments of the present invention that may be used, for example, as one of the high-band cross-dipole radiating elements 52 included in the base station antenna 10 of FIGS. 1-2. The radiating element 230 includes a dipole/stalk assembly 240 and a feed structure 270. FIG. 4 is a perspective view of the dipole/stalk assembly 240. FIGS. 5A-5C are perspective views that illustrate the feed structure 270 and steps for assembling the same. FIGS. 6A and 6B are front and rear perspective views of the assembled radiating element 230, and FIG. 6C is a front shadow perspective view of the radiating element 230.

[0071] Referring to FIG. 4, the dipole/stalk assembly 240 forms the stalk 250 and the dipole radiators 260-1, 260-2 of radiating element 230. The dipole/stalk assembly 240 is formed of metal or another conductive material (e.g., metallized plastic). The stalk 250 forms the rear portion of the dipole/stalk assembly 240, and is used to mount the dipole radiators 260-1, 260-2 forwardly of a feed board 210 (or other feed mechanism) for radiating element 230. It will be appreciated that in use the dipole/stalk assembly 240 will be rotated approximately 90° from the orientation shown in FIG. 4 (and in FIGS. 6A-6C) when a base station antenna that includes radiating element 230 is mounted for normal use.

[0072] The stalk 250 comprises four tubular columns 252-1, 252-2, 254-1, 254-2 that may be formed as a monolithic structure. Each tubular column 252, 254 may have an open interior. Tubular columns 252-1, 252-2 are longer than tubular columns 254-1, 254-2. Respective flanges 242-1, 242-2 (FIG. 6B) extend rearwardly from tubular columns 252-1, 252- 2. The feed structure 270 (discussed below) may be mounted in the tubular columns 252, 254. Four radial longitudinally-extending slots 258 extend from the front of the dipole/stalk assembly 240 toward the rear of the dipole/stalk assembly 240.

[0073] Dipole radiator 260-1 comprises first and second dipole arms 262-1, 262-2, and dipole radiator 260-2 comprises third and fourth dipole arms 262-3, 262-4. Each dipole arm 262 extends radially from the front of the stalk 250. Each dipole arm 262 may comprise a generally square shaped structure with an open interior. The base 264 of each dipole arm 262 may deviate from the square shape as it merges into the forward portion of a respective one of the tubular columns 252, 254. A Y-shaped member 268 extends inwardly from the distal end 266 of each dipole arm 262 into the open interior thereof.

[0074] FIGS. 5A-5C illustrate the feed structure 270 of radiating element 230. The feed structure 270 includes a pair of feed lines that are implemented as hook baluns 280-1, 280-2.

Each feed line/hook balun 280 passes RF signals to and from a respective one of the dipole radiators 260-1, 260-2. Each hook balun 280 includes a first longitudinally-extending member 282, a second longitudinally-extending member 284 and a cross member 286 that connects the first longitudinally-extending member 282 to the second longitudinally-extending member 284. The cross members 286 each have a cross-over section 288 that has a shallow U-shape or C- shape, where the cross-over section 288 on the first cross member 286-1 extends rearwardly while the cross-over section 288 on the second cross member 286-1 extends forwardly, which allows the two cross members 286-1, 286-2 to cross each other without touching.

[0075] Each hook balun 280 may include a fixed portion 272 and a spring-loaded portion 274. In the depicted embodiment, the fixed portion 272 may comprise the front portion of the first longitudinally-extending member 282, the cross member 286, and the second longitudinally-extending member 284. The spring-loaded portion 274 comprises the rear portion of the first longitudinally-extending member 282. The fixed portion 272 and the spring-loaded portion 274 of each hook balun 280 may be held together by mating features (not shown) and/or may held together by a separate support structure (discussed below).

[0076] As shown in FIG. 5B, a pair of dielectric tubes 276 are provided and the spring- loaded portion 274 of each hook balun 280 is inserted into a respective one of the dielectric tubes 276. As shown in FIG. 5C, a dielectric feed support structure 290 is provided that includes a pair of longitudinally-extending legs 292 and a generally X-shaped member 294. Each leg 292 of the dielectric feed support structure 290 is inserted into a respective one of the dielectric tubes 276. Each leg 292 may conform to the shape of the first longitudinally-extending member 282 of the hook balun and/or to the inner surface of the dielectric tube 276 that receives the first longitudinally-extending member 282 of the hook balun 280 and the associated rearwardly extending leg 292 of the feed support structure 290. The forward portion of each leg 292 may include a slot that receives the cross-member 286 of the hook balun 280. Each leg 292 may be configured to engage the spring-loaded portion 274 of a respective one of the hook baluns 280 and to tightly hold the spring-loaded portion 274 within its associated dielectric tube 276.

[0077] The generally X-shaped member 294 has four arms that extend radially from a central region. The generally X-shaped member 294 includes several pairs of opposed fingers 296 that include snap clip features. The pairs of fingers 296 engage the cross-members 286 of the hook baluns 280. The generally X-shaped member 294 may also engage the dipole/stalk assembly 240 and may be used to lock the feed support structure 290 into place within the dipole/stalk assembly 240 (see FIGS. 6A-6C). Once the feed support structure 290 is locked in place within the dipole/stalk assembly 240, the dielectric tubes 276 and hook baluns 280 may be held firmly in place in their appropriate locations within the dipole/stalk assembly 240.

[0078] The thickness and material of the dielectric tubes 276 and/or the dielectric feed support structure 290 may be selected to improve the impedance match between the feed board 210 and the dipole arms 262. It will also be appreciated that the pogo pin (or other spring- biased) connector 290 need not be used to form the rear portion of the first longitudinally- extending member 282. For example, in other embodiments, the pogo pin connector 290 may be in the middle of the first longitudinally-extending member 282 or may form the forward portion of the first longitudinally-extending member 282.

[0079] FIGS. 6A-6C illustrate the radiating element 230 in its assembled state. As shown, the feed structure 270 is inserted within the dipole/stalk assembly 240. The four arms of the X-shaped member 294 extend through the four respective slots 258 in the dipole/stalk assembly 240. Snap features on the arms of the X-shaped member 294 lock the feed support structure 290 in place behind the dipole arms 262. The first longitudinally-extending member 282 of each hook balun 280 is received in a respective one of the longer tubular columns 252 of the dipole/stalk assembly 240. As shown best in FIG. 6B, the rear portion of each hook balun 280 (which here is the plunger 294 of the pogo pin connector 290) extends all the way through its associated tubular column 252 so that it may mate with another structure (e.g., the feed board 210).

[0080] As shown in FIG. 6B, the rear surface of the dipole/stalk assembly 240 includes two pairs of rearwardly extending arcuate flanges 242. Each pair of flanges 242 is aligned with a respective one of the longer tubular columns 252. The rear surface of each flange 242 includes a plurality of rearwardly extending pins 244. A conductive gasket 246 is mounted on each respective pair of flanges 242. Each conductive gasket 246 may include a plurality of openings 248 that are aligned with the locations of the pins 244 so that the conductive gasket 246 may be mounted on the dipole/stalk assembly 240 by inserting the pins 244 through the mating openings 248 in the conductive gaskets 246. The conductive gaskets 246 may be formed of a resilient material so that the conductive gaskets 246 act as springs. The conductive gaskets 246 allow a ground connection on the feed board 210 (e.g., a ground pad) to be galvanically connected to the dipole/stalk assembly 240. It will be appreciated that in other embodiments a capacitive connection may be formed between the dipole/stalk assembly 240 and the ground connection on the feed board 210.

[0081] As the above description makes clear, the radiating element 230 includes a first dipole 260-1 that includes a first dipole arm 262-1 and a second dipole arm 262-2, and a hook balun 280-1 that includes a first longitudinally-extending segment 282, a second longitudinally- extending segment 284, and a transversely-extending cross member 286 that electrically connects the first longitudinally-extending segment 282 to the second longitudinally-extending segment 284. The first longitudinally-extending segment 282 includes a spring 297 that is part of a pogo pin connector 290. The radiating element 230 is part of a feed board assembly 200 that also includes a feed board 210. The radiating element 230 includes a stalk 250 (which may comprise a single piece stalk or a multi-piece stalk) that mounts the first and second dipole arms 262-1, 262-2 forwardly of the feed board 210. The first longitudinally-extending segment 282 of the hook balun 280 is connected to a feed trace 214 on the feed board 210 via a first solderless connection. The stalk 250 is electrically connected to a ground plane via a second solderless connection, which may be implemented as a resilient conductive pad in some embodiments.

[0082] FIGS. 7A-7B are a schematic side perspective view and a schematic rear shadow perspective view, respectively, of the radiating element 230 of FIGS. 4-6C mounted on the feed board 210 to provide the feed board assembly 200. The feed board 210 may comprise, for example, an RF printed circuit board that includes a dielectric substrate 212 with metal patterns on either major surface thereof (the ground plane on the rear surface of the dielectric substrate is not shown in FIGS. 7A-7B). As shown in FIGS. 7A-7B, the metal pattern 214 on the front surface of the dielectric substrate 212 includes a pair of feed traces 214-1, 214-2. Each feed trace 214 may be aligned so that the rear surface of one of the hook baluns 280 will rest on the feed trace 214 when the radiating element 230 is mounted on the feed board 210. The metal pattern on the rear surface of the dielectric substrate 212 may comprise a ground plane (not shown) that may be implemented, for example, as a solid metal layer. The metal pattern on the front surface of the dielectric substrate 212 further includes a plurality of ground pads 218, and a plurality of conductive vias 220 (e.g., metal-plated or metal-filled vias) are formed through the dielectric substrate 212 that electrically connect the ground pads 218 to the ground plane on the rear surface of the dielectric substrate 212. The ground pads 218 are positioned so that the conductive gaskets 246 will rest on the respective ground pads 218 when the radiating element 230 is mounted on the feed board 210. The ground pads 218 and conductive vias 220 are not shown in FIG. 7B so that the conductive gaskets 246 will be visible. FIG. 7C is a front view of a small portion of the feed board 210 that illustrates the ground pads 218, and the dotted circles in FIG. 7C show the positions of the conductive vias 220 that are behind the ground pads 218.

[0083] As the above discussion makes clear, when the radiating element 230 is mounted on the feed board 210, each hook balun 280 is physically and electrically connected to a respective one of the feed traces 214. The pogo pin connector 290 (or other spring-loaded structure) of the hook balun 280 ensures that a consistent electrical contact is maintained between each hook balun 280 and its corresponding feed trace 214. The dipole/stalk assembly 240 is physically and electrically connected to the ground pads 218 on the feed board 210 through the conductive gaskets 246. The resilience or "springiness" of the conductive gaskets 246 when compressed ensures that a consistent electrical contact is maintained between the dipole/stalk assembly 240 and the ground pads 218. A mounting structure (not shown) may be used to mount the radiating element 230 to the feed board 210 (or to another structure). This mounting structure ensures that the radiating element 230 is biased against the feed board 210 so that the springs 297 in the pogo pins 290 and the conductive gaskets 246 are compressed.

[0084] FIG. 8 is a partial perspective view of an antenna 300 including a 4x4 array of the feed board assemblies 200 of FIGS. 7A-7B. As shown in FIG. 8, the antenna 300 includes a reflector 310. Sixteen of the feed board assemblies 200 of FIGS. 7A-7B are mounted forwardly of the reflector 310. The feed board assemblies 200 are mounted in columns so that a 4x4 array of radiating elements 230 is formed (i.e., the array has four columns and four rows, with four radiating elements in each column and row). Dielectric mounting structures (not shown) may be used to mount the feed board assemblies 200 to the reflector 310. Isolation walls 312 are provided that extend forwardly from the reflector 310. The isolation walls 312 may comprise sheet metal walls and may increase the isolation between radiating elements 230 in adjacent columns.

[0085] When soldered connections are used between a radiating element and its associated feed board, the feed board is typically mounted on the front surface of the reflector of the antenna and openings are cut into the reflector in order to allow the stalks of the radiating elements to extend through the feed board and be soldered to the feed board on both the front and back sides of the feed board. When the radiating elements according to embodiments of the present invention are used that have solderless connections, it may not be necessary to include these openings in the reflector, which further simplifies fabrication of the antenna and which may also improve the performance of the antenna (e.g., the front-to-back ratio performance).

[0086] FIG. 9A is a shadow perspective view of a radiating element 430 that is a modified version of the radiating element 230 of FIGS. 6A-6C. FIG. 9B is a perspective view of the two hook balun feed lines 480-1, 480-2 included in the radiating element 430 of FIG. 9 A.

[0087] As shown in FIG. 9 A, the radiating element 430 includes a dipole/stalk assembly 440. The dipole/stalk assembly 440 may be identical to the dipole/stalk assembly 240 of radiating element 230, and hence further description thereof will be omitted.

[0088] Referring to FIG. 9B, it can be seen that the feed structure 470 of radiating element 430 differs from the feed structure 270 that is discussed above. In particular, the feed structure 470 comprises a pair of hook baluns 480-1, 480-2 that are each implemented as a single tubular structure. Each hook balun 480 includes a first longitudinally-extending member 482, a second longitudinally-extending member 484 and a cross member 486 that connects the first longitudinally-extending member 482 to the second longitudinally-extending member 484. The cross members 486 each have a cross-over section 488 that has a shallow U-shape or C-shape, where the cross-over section 488 on the first cross member 486-1 extends rearwardly while the cross-over section 488 on the second cross member 486-1 extends forwardly, which allows the two cross members 486-1, 486-2 to cross each other without touching.

[0089] The rearward portion of the first longitudinally-extending member 482 is implemented as a pogo pin connector 490. The first longitudinally-extending member 482 may comprise a tubular member that may form the barrel of the pogo pin connector. The cross member 486 and the second longitudinally-extending member 484 may be formed integral with the barrel of the pogo pin connector 490 or may be separate pieces that are joined together by joint sections (as shown). The rearward portion of the first longitudinally-extending member 482 may act as a spring-loaded portion 474 of the hook balun. The design of the hook baluns 480 shown in FIG. 9B may be advantageous as a separate support structure may not be required to hold the parts of the hook balun 480 together. The pogo pin connector 490 also need only apply force at one point, namely between the pogo pin connector 490 and the feed trace/pad on the feed board. In contrast, the pogo pin connectors 290 used in radiating element 230 are designed to apply force both (1) between the pogo pin connector and the feed trace/pad on the feed board and (2) between the pogo pin connector and the fixed portion of the hook balun.

[0090] The radiating elements according to embodiments of the present invention that have been discussed above include die cast structures that act as the stalk and dipole arms of the radiating elements. It will be appreciated, however, that embodiments of the present invention are not limited thereto. For example, FIGS. 10 and 11 illustrate a sheet metal based radiating element 530 according to embodiments of the present invention that includes a solderless feed line connection to a feed board 510. In particular, FIG. 10 is a schematic perspective view of the sheet metal based radiating element 530, while FIG. 11 is a perspective view illustrating how a conventional hook balun may be used in conjunction with a pogo pin connector to form a radiating element according to further embodiments of the present invention.

[0091] As shown in FIG. 10, the radiating element 530 is primarily formed of sheet metal. The radiating element 530 includes four dipole arms 540-1 through 540-4 and four stalks 550-1 through 550-4. Each stalk 550 may be integral with a respective dipole arm 540, and the four dipole arm/stalk structures 540/550 may be formed by stamping and bending sheet metal into the shapes shown in FIG. 10. The radiating element 530 includes a feed structure in the form of a pair of hook baluns 580. One of the hook baluns 580 is shown in greater detail in FIG. 11. As shown in FIG. 11, the hook balun 580 includes a first longitudinally-extending member 582, a second longitudinally-extending member 584 and a cross member 586 that connects the first longitudinally-extending member 582 to the second longitudinally-extending member 584. The cross members 586 each have a cross-over section 588 that has a shallow U-shape or C- shape. The rearward portion of the first longitudinally-extending member 582 is implemented as a pogo pin connector 590. The pogo pin connector 590 differs from the pogo pin connectors 290 and 490 discussed above in that the pogo pin connector 590 has a hemicylindrical shape instead of a cylindrical shape so that the portion of pogo pin connector 590 that faces the stalk 250 is flat. As shown in FIG. 10, the first longitudinally-extending member 582 of each hook balun 580-1, 580-2 may be mounted on stalks 550-1, 550-2, respectively, and the second longitudinally-extending member 584 of each hook balun 580-1, 580-2 may be mounted on stalks 550-3, 550-4, respectively. The hook baluns 580 may be mounted on the stalks 550 using dielectric spacers (not shown).

[0092] The pogo pin connectors 590 may connect each hook balun feed line 580 to a corresponding feed line (or other conductive structure) on an underlying feed board. The stalks 550 are capacitively coupled to an underlying structure (e.g., the feed board or a reflector) by placing dielectric pads between the "foot" of each stalk 550 and the underlying structure.

[0093] The radiating elements according to embodiments of the present invention may be mounted on feed boards that are mounted in front of a reflector of a base station antenna, as discussed above. It will also be appreciated, however, that in other embodiments, the radiating elements may be mounted to feed boards (or other structures) that are mounted behind the reflector of the base station antenna. In particular, pursuant to further embodiments of the present invention, base station antennas are provided that include a reflector having a plurality of openings, a feed board mounted behind the reflector, and an array of radiating elements that extend forwardly from the reflector. At least some of the radiating elements extend through respective ones of the openings in the reflector to physically contact the feed board and to electrically connect to the feed board via respective first solderless galvanic connections. The first solderless galvanic connections may be spring-biased connections (e.g., pogo pin connections) between feed lines of the radiating elements and feed traces or feed pads on the feed board. Second solderless galvanic connections may also be provided that electrically connect a ground plane of the antenna to ground lines on the radiating elements. The second solderless galvanic connections may be spring-biased connections (e.g., resilient conductive pad connections). In some embodiments, the first solderless galvanic connections may be between the radiating elements and the feed board while the second solderless galvanic connections may be between the radiating element and a reflector of the antenna. The feed board may also include a calibration circuit in some embodiments.

[0094] FIGS. 12A-12C schematically illustrate a portion of a base station antenna 600 that has such a design. In particular, FIG. 12A is a perspective front view showing the radiating element 230 of FIGS. 4-6C mounted in front of a reflector 602 of base station antenna 600, while FIG. 12B is a perspective rear view that illustrates how the feed board 610 is positioned behind the reflector 602. FIG. 12C is a shadow front perspective view of the reflector 602, feed board 610 and radiating element 230 of FIGS. 12A-12B.

[0095] As shown in FIG. 12 A, the radiating element 230 extends forwardly from the reflector 602. While not visible in FIG. 12A, two small openings (or one larger opening) are formed in the reflector 602. The rearwardly extending flanges 242-1, 242-2 on the dipole/stalk assembly 240 extend through these openings.

[0096] As shown in FIGS. 12B-12C, the feed board 610 may be mounted behind the reflector 610. The feed board may have the design of any of the feed boards discussed above. Alternatively, the feed board 610 may be part of a larger printed circuit board structure such as a calibration circuit board for a beamforming antenna. This may reduce the total number of printed circuit boards required in antenna 600, and may also eliminate the need for electrical connections between separate calibration circuit boards and feed boards.

[0097] It will also be appreciated that the techniques according to embodiments of the present invention may be used on other than dipole-based radiating elements For example, the techniques disclosed herein may also be used with patch radiating elements in other embodiments.

[0098] Embodiments of the present invention have been described above with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

[0099] It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

[00100] It will be understood that when an element is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements present. It will also be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion ( i.e "between" versus "directly between", "adjacent" versus "directly adjacent", etc.).

[00101] Relative terms such as "below" or "above" or "upper" or "lower" or "horizontal" or "vertical" may be used herein to describe a relationship of one element, layer or region to another element, layer or region as illustrated in the figures. It will be understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.

[00102] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" "comprising," "includes" and/or "including" when used herein, 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.

[00103] Aspects and elements of all of the embodiments disclosed above can be combined in any way and/or combination with aspects or elements of other embodiments to provide a plurality of additional embodiments.