CROSS-REFERENCE TO RELATED APPLICATION [0001] The present application claims priority to Italian Patent Application Serial No. 102021000014843, filed June 8, 2021, the entire content of which is incorporated herein by reference as if set forth in its entirety.

FIELD

[0002] The present invention relates to cellular communications systems and, more particularly, to base station antennas having active antenna modules

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. 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. 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 fifth generation ("5G") cellular technologies, base station antennas are now routinely being deployed that have active beamforming capabilities. Active beamforming refers to transmitting RF signals through a multi-column array of radiating elements in which the relative amplitudes and phases of the sub-components of an RF signal that are transmitted (or received) through the different radiating elements of the array are adjusted so that the radiation patterns that are formed by the individual radiating elements constructively combine in one or more desired directions to form narrower antenna beams that have higher gain. With active beamforming, the shape and pointing direction of the antenna beams generated by the multi-column array may, for example, be changed on a time slot-by-time slot basis of a time division duplex ("TDD") multiple access scheme. Moreover, different antenna beams can be generated simultaneously on the same frequency resource in a multi-user MIMO scenario. More sophisticated active beamforming schemes can apply different beams to different physical resource blocks that are a combination of time and frequency resources by applying the beam vector in the digital domain. Base station antennas that have active beamforming capabilities are often referred to as active antennas. When the multi-column array includes a large number of columns of radiating elements (e.g., sixteen or more), the array is often referred to as a massive MIMO array. A module that includes a multi-column array of radiating elements and associated RF circuitry (and perhaps baseband circuitry) that implement an active antenna is referred to herein as an active antenna module. Active antenna modules may be deployed as standalone base station antennas, or may be deployed in larger antenna structures that include additional active antenna modules and/or conventional "passive" antenna arrays that are connected to radios that are external to the antenna structures.

SUMMARY

[0005] Pursuant to embodiments of the present invention, filter units are provided that include a resonant cavity filter that includes a metal housing having an opening therein and a spring-biased contact that extends through the opening in the metal housing to contact a port of the resonant cavity filter.

[0006] In some embodiments, the spring-biased contact may be a pogo pin connector assembly.

[0007] In some embodiments, the metal housing may include an internal chamber having a first open end that is defined by the opening, and the pogo pin connector assembly may extend through at least a portion of the internal chamber. In some embodiments, the port may be within the internal chamber.

[0008] In some embodiments, the filter unit may further include a conductive gasket mounted in the opening, and the pogo pin connector assembly may extend through a hole in the conductive gasket.

[0009] In some embodiments, the pogo pin connector assembly and walls that define the internal chamber comprise an RF transmission line structure. In such embodiments, the pogo pin connector assembly may comprise an inner conductor of the RF transmission line structure and the walls that define the internal chamber may comprise part of an outer conductor or ground of the RF transmission line structure.

[0010] In some embodiments, the filter unit may be provided in combination with a first printed circuit board that includes RF circuitry and an EMI shield having external sidewalls and a front wall, the EMI shield substantially covering a front surface of the first printed circuit board. In such embodiments, the pogo pin connector assembly may contact a conductive structure on the first printed circuit board. In some embodiments, the metal housing may be electrically connected to the EMI shield, and the pogo pin connector assembly may extend through an opening in the EMI shield. In some embodiments, the EMI shield may include a cylindrical internal sidewall that extends rearwardly from the opening in the EMI shield, and the pogo pin connector assembly may extend through a passageway defined by the cylindrical internal sidewall.

[0011] In some embodiments, the opening is in a bottom surface of the metal housing.

[0012] Pursuant to further embodiments of the present invention, filter units are provided that include a cavity filter that has a metal housing that includes a floor, at least one sidewall and a cover that together define an internal cavity, and a plurality of resonators mounted within the internal cavity. These filter units further include a spring-biased contact that extends through an opening in the cover.

[0013] In some embodiments, the spring-biased contact may be a pogo pin connector assembly. The pogo pin connector assembly may galvanically connect a port of the resonant cavity filter to a conductive structure on a printed circuit board that is external to the resonant cavity filter. The port may, for example, be within the internal cavity. [0014] In some embodiments, the filter unit may further comprise an annular sleeve that extends outwardly from the cover, and a conductor of the pogo pin connector assembly may extend through the annular sleeve. In some embodiments, a base of the annular sleeve that is adjacent the cover may have a first internal diameter and a distal end of the annular sleeve may have a second internal diameter that is larger than the first internal diameter. Additionally, the filter unit may further comprise an annular conductive gasket that may be mounted in the distal end of the annular sleeve. In some embodiments, the pogo pin connector assembly and the annular sleeve may comprise part of an RF transmission line structure that electrically connects the resonant cavity filter to the printed circuit board. The pogo pin connector assembly may be an inner conductor of the RF transmission line structure and the annular sleeve may be part of an outer conductor of the RF transmission line structure. In some embodiments, in the conductive gasket may galvanically connect the annular sleeve to a reflector of an antenna.

[0015] In some embodiments, the printed circuit board may be a feed board of the antenna. In some embodiments, a primary electrical connection to a ground plane of the feed board may be a capacitive coupling between the ground plane of the feed board and the reflector.

[0016] In some embodiments, the cover may be a removable cover. In some embodiments, plurality of tuning elements may be formed in the cover.

[0017] Pursuant to additional embodiments of the present invention, antennas are provided that include a first printed circuit board that includes radio frequency ("RF") circuitry, an EMI shield covering a front surface of the first printed circuit board, and a resonant cavity filter having a first port, the resonant cavity filter mounted forwardly of the EMI shield. A spring-biased contact directly electrically connects a conductive structure on the first printed circuit board to the first port of the resonant cavity filter.

[0018] In some embodiments, the spring-biased contact may be a pogo pin connector assembly. In some embodiments, may be the EMI shield may include external sidewalls and a front wall, and the pogo pin connector assembly may extend through an opening in the front wall of the EMI shield to contact the conductive structure on the first printed circuit board.

[0019] In some embodiments, the pogo pin connector assembly may be a conductive pogo pin connector and a dielectric spacer, the EMI shield may include a cylindrical wall that extends rearwardly from the opening in the front wall, and the dielectric spacer may contact the cylindrical wall. [0020] In some embodiments, the resonant cavity filter may include a metal housing that has an internal chamber, and the pogo pin connector assembly may extend through at least a portion of the internal chamber. In some embodiments, the first port of the resonant cavity filter may be within the internal chamber.

[0021] In some embodiments, the antenna may further comprise a conductive gasket that electrically connects the EMI shield to a metal housing of the resonant cavity filter. In some embodiments, the pogo pin connector assembly may extend through a hole in the conductive gasket.

[0022] In some embodiments, the pogo pin connector assembly and walls that define the internal chamber may comprise an RF transmission line structure. In some embodiments, the pogo pin connector assembly may comprise an inner conductor of the RF transmission line structure and the walls that define the interior chamber may comprise part of an outer conductor of the RF transmission line structure.

[0023] Pursuant to still further embodiments of the present invention, antennas are provided that include a reflector, a printed circuit board (e.g., a feed board) mounted forwardly of the reflector, a resonant cavity filter mounted behind the reflector, and an RF transmission line structure that includes a signal conductor in the form of a pogo pin connector assembly that galvanically connects a port of the resonant cavity filter to a conductive trace on the printed circuit board and a ground conductor that galvanically connects a housing of the resonant cavity filter to the reflector.

[0024] In some embodiments, the trace on the printed circuit board and a ground plane of the printed circuit board may form a microstrip transmission line, and the primary electrical connection to the ground plane of the printed circuit board may be a capacitive coupling between the ground plane of the printed circuit board and the reflector.

[0025] In some embodiments, the reflector may be galvanically connected to the housing of the resonant cavity filter through a conductive gasket. In some embodiments, the pogo pin connector assembly may extend through a hole in the conductive gasket.

[0026] In some embodiments, a rear side of the printed circuit board includes a ground plane and a conductive pad that is electrically isolated form the ground plane, and the printed circuit board further includes at least one conductive via that electrically connects the conductive pad to the conductive trace, where the conductive trace is on a front side of the printed circuit board.

[0027] In some embodiments, the resonant cavity filter may include a metal housing that has an internal chamber, and the pogo pin connector assembly may extend through at least a portion of the internal chamber.

[0028] In some embodiments, the port of the resonant cavity filter may be within the internal chamber.

[0029] In some embodiments, the resonant cavity filter may include a metal housing that has a floor, at least one sidewall and a cover that together define an internal cavity.

[0030] In some embodiments, the antenna may further include an annular sleeve that extends outwardly from the cover, and a portion of the pogo pin connector assembly may extend through the annular sleeve.

[0031] In some embodiments, a base of the annular sleeve that is adjacent the cover may have a first internal diameter and a distal end of the annular sleeve may have a second internal diameter that is larger than the first internal diameter, and the antenna may further include an annular conductive gasket mounted in the distal end of the annular sleeve. In some embodiments, the annular conductive gasket may be the ground conductor that galvanically connects the metal housing of the resonant cavity filter to the reflector.

[0032] In some embodiments, the cover may be a removable cover that includes a plurality of tuning elements formed therein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIGS. 1 A and IB are perspective front and back views, respectively, of an active antenna module that may include filter units having spring-biased contacts according to embodiments of the present invention.

[0034] FIGS. 2 A and 2B are perspective front and back views, respectively, of the active antenna module of FIGS. 1 A-1B partially slid into place within a larger passive base station antenna.

[0035] FIG. 3A is a perspective back view of the passive base station antenna of FIGS. 2A-2B with the active antenna module fully installed therein. [0036] FIG. 3B is a shadow perspective front view of the antenna of FIGS. 2A-2B that schematically illustrates the linear arrays of radiating elements included in the passive base station antenna.

[0037] FIG. 4 is an exploded perspective view of the active antenna module of FIGS.

1A-1B.

[0038] FIG. 5 is a schematic diagram of the active circuit layer, the filter layer and the antenna layer of the active antenna module of FIG. 4.

[0039] FIGS. 6 and 7 are schematic front and side views, respectively, of the active circuit layer included in the active antenna module of FIG. 4.

[0040] FIG. 8A is a perspective view of a pogo pin connector assembly that may be included in the filter units according to embodiments of the present invention.

[0041] FIG. 8B is a partial cross-sectional view of the pogo pin connector of the pogo pin connector assembly of FIG. 8 A.

[0042] FIG. 8C is a schematic side view of pogo pin connector assembly of FIGS. 8A and 8B where a conductive pin has been added to the assembly.

[0043] FIG. 9 is a partial cross-sectional view illustrating a filter unit according to embodiments of the present invention that includes a first pogo pin connector assembly that electrically connects the filter unit to a first external printed circuit board.

[0044] FIG. 10 is another partial cross-sectional view of the filter unit of FIG. 9 illustrating a second pogo pin connector assembly that electrically connects the filter unit to a second external printed circuit board.

[0045] FIG. 11 is a perspective view of a front portion of the second pogo pin connector assembly and the annular sleeve of FIG. 10 .

[0046] FIGS. 12A and 12B are schematic plan views of the front and rear surfaces, respectively, of a small portion of an embodiment of a feed board printed circuit board of FIG. 10

[0047] FIG. 13 is a schematic cross-sectional view of the filter unit of FIGS. 9-11 that illustrates both pogo pin connector assemblies included therein.

DETAILED DESCRIPTION

[0048] Pursuant to embodiments of the present invention, filter units having spring-biased contacts are provided that may be used, for example, in active antenna modules for cellular communications systems. The filter units according to embodiments of the present invention may be connected to external circuits using these spring-biased contacts, which may avoid the need for soldered connections. For example, the filter units may include pogo-pin connector assemblies that, for downlink signals, connect a filter of the filter unit to a first external circuit (e.g., a radio) that generates the RF signals that are input to the filter and/or to a second external circuit (e.g., one or more radiating elements) that receives the RF signals output by the filter. For uplink signals, the pogo-pin connector assemblies may receive RF signals from the second external circuit and pass them to the filter and/or may pass the uplink signals from the filter to the first external circuit. The use of such pogo-pin connector assemblies (or other spring-biased contacts) may significantly simplify the manufacturing process, as forming soldered connections is a labor-intensive operation. Moreover, since spring-biased contacts are used to replace soldered connections, rework of defective filter units becomes far simpler. If a conventional filter unit that includes soldered input and output connections is found to be defective during testing, it is necessary to melt each soldered connection and clean away the solder so that the defective filter unit may be removed and then repaired or replaced. Additionally, the soldered connections may themselves be defective, requiring that the solder be melted and removed. Such operations are both costly and time-consuming. Additionally, when soldered connections are used, space is required between the filter unit and the external circuits that the filter unit is connected to in order to allow the soldering equipment to form the solder joints. This increases the overall size of the electronic device that includes the filter unit. The filter units having spring-biased contacts according to embodiments of the present invention may avoid the disadvantages associated with soldered connections, thereby reducing manufacturing costs, speeding up the manufacturing process, and/or allowing the filter units to be positioned more closely to other circuits.

[0049] Solder joints are typically used for electrical connections in base station antennas 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, 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.

[0050] 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.

[0051] Pursuant to embodiments of the present invention, filter units are provided that have solderless connections to other elements of an active antenna module. 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.

[0052] In some embodiments, the filter units may include a resonant cavity filter and one or more pogo pin connector assemblies. For example, the filter unit may comprise a resonant cavity filter that includes a metal housing having an opening therein. The pogo pin connector assembly may extend through the opening in the metal housing to contact a port of the resonant cavity filter to an external circuit element. In some embodiments, the housing of the filter may include an internal chamber that has a first open end that comprises the opening into the housing, and the pogo pin connector assembly extends through at least a portion of this internal chamber. In such embodiments, the port of the filter (e.g., an RF input port or an RF output port) is positioned within the internal chamber. The pogo pin connector assembly may connect a conductive signal trace of an RF circuit to the port of the filter. The ground connection of the RF circuit may be electrically connected to the metal housing of the filter via a conductive gasket that is mounted in the opening. The conductive gasket may comprise an annualar gasket and the pogo pin connector assembly may extend through the conductive gasket in some embodiments.

[0053] In other embodiments, filter units are provided that include a resonant cavity filter that comprises (1) a metal housing that includes a floor, at least one sidewall and a cover that together define an internal cavity and a plurality of resonators mounted within the internal cavity and (2) a spring-biased contact that extends through an opening in the cover. The spring-biased contact may be a pogo pin connector assembly. The pogo pin connector assembly may galvanically connect an internal port of the resonant cavity filter to a conductive structure on a printed circuit board that is external to the resonant cavity filter. The filter unit may also include an annular sleeve that extends outwardly from the cover. A portion of the pogo pin connector assembly may extend through the annular sleeve. A base of the annular sleeve that is adjacent the cover has a first internal diameter and a distal end of the annular sleeve has a second internal diameter that is larger than the first internal diameter, and an annular conductive gasket may be mounted in the distal end of the annular sleeve. The conductive gasket may galvanically connect the annular sleeve and the cover of the filter to a reflector of an antenna.

[0054] Pursuant to still further embodiments of the present invention, antennas are provided that include a first printed circuit board, an EMI shield covering a front surface of the first printed circuit board, and a resonant cavity filter having a first port, the resonant cavity filter mounted forwardly of the EMI shield. A spring-biased contact such as a pogo pin connector assembly may directly electrically connect a conductive structure on the first printed circuit board to the first port of the resonant cavity filter.

[0055] Pursuant to still further embodiments of the present invention, antennas are provided that include a reflector, a feed board mounted forwardly of the reflector, a resonant cavity filter mounted behind the reflector, and an RF transmission line structure that includes a signal conductor in the form of a pogo pin connector assembly that galvanically connects a port of the resonant cavity filter to a conductive trace on the feed board and a ground conductor that galvanically connects a housing of the resonant cavity filter to the reflector.

[0056] The filter units having spring-biased interface contacts according to embodiments of the present invention may be part of an active antenna module that provides 5G communications capability. Before discussing the filter units according to embodiments of the present invention, an example active antenna module in which these filter units may be used will be discussed in greater detail.

[0057] FIGS. 1 A and IB are perspective front and back views, respectively, of an active antenna module 100 that may include filter units according to embodiments of the present invention. As shown in FIGS. 1 A and IB, the active antenna module 100 includes a housing 110 and an outer radome 192. The housing 110 may include heat fins 112 that are used to dissipate heat generated by active circuit components that are mounted within the housing 110. The housing 110 with heat fins 112 forms the rear side of the active antenna module 100. The radome 192 may be formed of a dielectric material that is substantially transparent to RF radiation in the operating frequency band of the active antenna module 100. The radome 192 may be mounted forwardly of the housing 110 and may cover and protect a multi-column array of radiating elements that is included in the active module 100.

[0058] The active antenna module 100 may be used as a standalone antenna. When used in this fashion, the active antenna module 100 may be mounted on a raised structure with the radiating elements thereof pointing outwardly so that they can form antenna beams in the direction of the intended coverage area for the active antenna module 100. A pair of fiber optic cables may extend between the active antenna module 100 and a baseband unit (not shown).

[0059] The active antenna module may alternatively be integrated into a larger "passive" base station antenna. A passive base station antenna refers to a base station antenna that includes one or more arrays of radiating elements that generate relatively static antenna beams. Passive base station antennas include RF connectors or "ports" that are connected to external radios.

[0060] FIGS. 2 A and 2B are perspective front and back views, respectively, of the active antenna module 100 of FIGS. 1 A-1B partially slid into place within a larger passive base station antenna 10. The passive base station antenna 10 may comprise an elongated structure that extends along a longitudinal axis L. The passive base station antenna 10 includes a radome 12 and a first top end cap 14. The passive base station antenna 10 also includes a bottom end cap 16 which includes a plurality of RF ports 18 (FIGS. 3A-3B) mounted therein. The RF ports 18 are connected to external radios (not shown) that are connected to the arrays of radiating elements of the passive base station antenna 10. The passive 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 passive base station antenna 10 is mounted for normal operation).

[0061] The depth of the upper portion 22 of the passive base station antenna 10 is less than the lower portion 20 of the passive base station antenna 10. The rear side of the upper portion 22 of the passive base station antenna 10 is recessed. This allows the active antenna module 100 to be pushed or slid into place and secured to the upper rear side of the passive base station antenna 10. The lower portion 20 of the passive base station antenna 10 includes a second top end cap 24.

[0062] FIG. 3 A is a rear perspective view of the passive base station antenna 10 with the active antenna module 100 fully integrated therein. FIG. 3B is a shadow perspective front view of the passive base station antenna 10 with the active antenna module 100 integrated therein that schematically illustrates the linear arrays of radiating elements included in the passive base station antenna 10. As shown in FIG. 3B, the passive base station antenna 10 includes one or more reflectors 26. Various components of the passive antenna 10 may be mounted behind the lower portion of the reflector 26, such as remote electronic tilt units, phase shifters, diplexers, controllers and the like (not shown). A pair of linear arrays 30-1, 30-2 of low-band radiating elements 32, 34 and four linear arrays 40-1 through 40-4 of mid-band radiating elements 42, 44 are mounted to extend forwardly from the reflector 26. The low-band radiating elements 32, 34 may comprise slant -45°/+45° cross dipole radiating elements that are configured to transmit and receive RF signals in all or part of the 617-960 MHz frequency range. The low-band radiating elements 34 differ from the low-band radiating elements 32 in that they have slanted feed stalks so that the active antenna module 100 can fit in between the two low-band linear arrays 30-1, 30- 2

[0063] The mid-band radiating elements 42, 44 may also comprise slant -45°/+45° cross dipole radiating elements that are configured to transmit and receive RF signals in all or part of the 1427-2690 MHz frequency range. In the depicted embodiment, the outer mid-band linear arrays 40-1 and 40-4 include mid-band radiating elements 42 that are configured to transmit and receive RF signals in the 1695-2690 MHz frequency range (or alternatively the 1427-2690 MHz frequency range), while the inner mid-band linear arrays 40-2 and 40-3 include mid-band radiating elements 44 that are configured to transmit and receive RF signals in the full 1427- 2690 MHz frequency range. The radiating elements of the active antenna module 100 are not shown in FIG. 3B to simplify the drawing.

[0064] Passive base station antennas that are designed for use with integrated active antenna modules are discussed in detail in U.S. Patent Application Serial No. 17/209,562 ("the '562 application"), the entire content of which is incorporated herein by reference. The passive base station antenna 10 and the active antenna module 100 may have the mechanical designs of any of the passive base station antennas and active antenna modules disclosed in the above- referenced '562 application.

[0065] FIG. 4 is an exploded schematic perspective view of the active antenna module 100. As shown in FIG. 4, the rearmost portion of the active antenna module 100 is the housing 110 having heat fins 112. The housing 110 may comprise a metal frame and the heat fins 112 may be formed integrally with the housing 110. The bottom surface of the housing 110 and the heat fins act as a heat sink. Heat spreading structures (not shown) such as vapor chambers, heat pipes or any other high thermal conductivity material, structure or assembly may also be mounted in the housing 110 adjacent regions where high heat density occurs during device operation. The heat spreading structures may facilitate spreading heat from a small area (e.g., the area behind active circuits in the active circuit layer 120) to a much larger area so that the heat may be vented from the active antenna module 100 through the heat fins 112.

[0066] An "active circuit layer" 120 is mounted forwardly of the heat spreading structures. The active circuit layer 120 may comprise a printed circuit board structure 122 (not visible in FIG. 4, but shown in FIGS. 5 and 6-7) and an EMI shield 124 that covers and protects the printed circuit board structure 122. The printed circuit board structure 122 may include multiple printed circuit boards that have processors as well as baseband and RF circuit components mounted thereon such as field programmable gate arrays, amplifiers, oscillators, switches, circulators, up -converters, down-converters and the like. The EMI shield 124 may comprise a metal (e.g., aluminum) structure that may be formed by, for example, die casting.

The EMI shield 124 shields the circuits and transmission lines in the active circuit layer 120 from RF radiation from external sources, and prevents RF energy radiated from the active circuit layer 120 from impacting other circuits/elements in the active antenna module 100 or the passive antenna 10. Electrical connections may extend through the EMI shield 124 to facilitate connecting circuit elements in the active circuit layer 120 to the filter layer 170. The active circuit layer 120 will be described in greater detail below with reference to FIGS. 5 and 6-7. Various of the processors and baseband/RF circuit components may generate significant amounts of heat. By providing vapor chambers or other heat spreading structures directly behind the highest heat generating circuits of the active circuit layer 120, the heat generated by such circuits may be more efficiently vented from the active antenna module 100.

[0067] A filter layer 170 is mounted forwardly of the active circuit layer 120. The filter layer 170 includes a plurality of RF filters 174. The RF filters 174 may be formed as filter banks 172 that each include a plurality of RF filters 174 that share a common housing. In the depicted embodiment, a total of four filter banks 172 are provided that each include eight RF filters 174 that are formed in a common housing. Each RF filter 174 may comprise a resonant cavity bandpass filter that is configured to pass RF signals in the operating frequency band of the active antenna module 100. The filters 174 may be mounted directly on the EMI shield 124.

[0068] An antenna layer 180 is provided forwardly of the filter layer 170. The antenna layer 180 may include a reflector 182 and a plurality of radiating elements 184. The reflector 182 may comprise, for example, a metallic sheet or a frequency selective surface that is designed to reflect RF energy in the operating frequency range of the radiating elements 184 of the active antenna module 100. The radiating elements 184 may comprise, for example, slant -45°/+45° cross dipole radiating elements that are configured to transmit and receive RF signals in the operating frequency range of the active antenna module 100. This operating frequency range may, for example, comprise all or a portion of the 3.1-4.2 GHz frequency range or all or a portion of the 5.1-5.8 GHz frequency range. In an example embodiment, the operating frequency range may be the 3.4-3.8 GHz frequency band. The radiating elements 184 may be arranged in a plurality of rows and columns. In the depicted embodiment, a total of eight columns having twelve radiating elements 184 each are provided. The radiating elements 184 may be mounted on feed board printed circuit boards 188 (FIG. 10). As will be explained below, the upper and lower half of each column are fed by different transceivers so that the active antenna module 100 operates as two separate eight column arrays 186-1, 186-2 of radiating elements 184 that are stacked along the longitudinal axis of the active antenna module 100. As a result, the active antenna module 100 effectively includes sixteen columns of radiating elements 184 (namely two arrays 186 with eight columns each, where each column includes six radiating elements 184). Since the radiating elements 184 are dual-polarized radiating elements, this means that the active antenna module 100 effectively has thirty -two columns of radiators that can simultaneously transmit or receive RF signals.

[0069] An inner radome 190 covers and protects the antenna layer 180. An outer radome 192 covers the inner radome 190. The function and operation of the inner radome 190 and the outer radome 192 are described in more detail in the above-referenced '562 application.

[0070] FIG. 5 is a schematic diagram of the printed circuit board structure 122 of the active circuit layer 120, the filter layer 170 and the antenna layer 180. As shown in FIG. 5, the printed circuit board structure 122 includes an optical interface printed circuit board ("PCB")

130, a digital front haul printed circuit board 132, a pair of RF front end printed circuit boards 134-1, 134-2, and a pair of power supply printed circuit boards 138-1, 138-2. Each RF front end printed circuit board 134 may have a plurality of RF power amplifier ("PA") printed circuit boards 136 mounted thereon. Each RF PA printed circuit board 136 supports four RF channels, and hence a total of eight RF printed circuit boards 136 are provided to support thirty -two channels that are coupled to the respective thirty-two columns of radiators discussed above. The active circuit layer 120 may further include a power bar or other power bus 126. The power bus may connect to each of the power supply printed circuit boards 138 and to the digital front haul printed circuit board 132.

[0071] The digital front haul printed circuit board 132 may be mounted in the middle of the heat sink, and may be placed directly on a first of the vapor chambers. The first and second RF front end printed circuit boards 134-1, 134-2 may be mounted on either side of the digital front haul printed circuit board 132, and may likewise be mounted directly on respective second and third vapor chambers. Four RF PA printed circuit boards 136 are mounted on each RF front end printed circuit board 134, and may be soldered onto or press fit on the front surfaces of the RF front end printed circuit boards 134. The digital front haul printed circuit board 132 and the first and second RF front end printed circuit boards 134 may be formed using conventional low cost printed circuit boards formed using FR4 or the like. The RF PA printed circuit boards 136 may be formed using dielectric materials that have low insertion losses for RF signals.

[0072] The filter layer 170 includes the above-described banks 172 of resonant cavity filters 174. A total of thirty -two resonant cavity filters 174 are provided, with each resonant cavity filter 174 coupled to a respective one of the transmit/receive chains on the RF PA printed circuit boards 136. As noted above, the filters 174 may be mounted directly on the EMI shield 124 that covers and protects the printed circuit boards of the active circuit layer 120.

[0073] First and second resonant cavity filters 174 are coupled to each of the sixteen columns of radiating elements 184, where the first resonant cavity filter 174 is coupled to the slant -45° radiators of the radiating elements 184 in the column, and the second resonant cavity filter 174 is coupled to the slant +45° radiators of the radiating elements 184 in the column.

[0074] FIGS. 6 and 7 are schematic front and side views, respectively, of the printed circuit board structure 122 of the active circuit layer 120. As shown in FIG. 6, a pair of optical connector modules 140-1, 140-2 are provided on the optical interface printed circuit board 130. Each optical connector module 140 may have the same design, with two optical connector modules 140 provided to double the throughput and/or to provide redundancy. Each optical connector module 140 is a bidirectional device that includes a fiber optic connector, an integrated optical-to-electrical converter that converts optical digital baseband data received at the connector module 140 into an electrical baseband data stream and an integrated electrical -to- optical converter that converts an electrical baseband data stream that is received from the digital front haul printed circuit board 132 into digital optical signals.

[0075] A high speed cable assembly 142 connects the first and second optical connectors 140 to a main field programmable gate array ("FPGA") 144 that is mounted on the digital front haul printed circuit board 132. The main FPGA 144 may perform various functions including ORAN processing and digital beamforming. The main FPGA 144 is connected to four secondary FPGAs 146 that are mounted on the RF front end printed circuit boards 134 (two secondary FPGAs 146 are provided per RF front end printed circuit board 134). High-speed board-to-board connectors 148 are used to connect the main FPGA 144 to each of the secondary FPGAs 146. Each secondary FPGA 146 may perform additional processing.

[0076] Each secondary FPGA 146 is connected to a pair of RF transceivers 150. Four RF transceivers 150 are located on each of the RF front end printed circuit boards 134, with each RF transceiver 150 being associated with a respective one of the RF PA printed circuit boards 136. Each secondary FPGA is 146 coupled to its associated two RF transceivers 150 by a pair of JESD transmission paths 152.

[0077] Each RF transceiver 150 includes a digital -to-analog converter, an I/Q modulator (including a local oscillator) that, for downlink signals, converts an input digital data stream into four RF signals. The RF transceivers 150 likewise include an analog-to-digital converter and an I/Q demodulator that demodulate four RF uplink signals and convert the demodulated data into a digital data stream. Thus, each RF transceiver 150 comprises the front end of four transmit/receive chains. Each RF PA printed circuit board 136 includes the back end of four transmit/receive chains, including filters, high power amplifiers, low noise amplifiers, amplifier predistortion circuitry and transmit/receive path switching. Thus, the eight RF transceivers 150 and the eight RF PA printed circuit boards 136 together form thirty -two transmit/receive chains. The output of each transmit/receive chain may be coupled to a respective one of the filters 174 in the filter layer 170.

[0078] FIG. 7 is a schematic side view of the printed circuit board structure 122 of the active circuit layer 120. As shown in FIG. 7, the digital front haul printed circuit board 132 may be offset rearwardly from the two RF front end printed circuit boards 134 so that high-speed board-to-board connectors 148 may be used to connect each RF front end printed circuit board 134 to the digital front haul printed circuit board 132. FIG. 7 also illustrates the high-speed cable assembly 142 that connects the optical connectors 140-1, 140-2 to the digital front haul printed circuit board 132.

[0079] Pursuant to embodiments of the present invention, filter units are provided that include resonant cavity filters that have solderless connections to external circuits. In some embodiments, the solderless connections may be implemented using spring-biased connectors such as pogo pin connector assemblies and/or resilient conductive gaskets.

[0080] FIGS. 8 A and 8B illustrate a pogo pin connector assembly 200 that may be included in the filter units according to embodiments of the present invention. In particular, FIG. 8A is a perspective view of the pogo pin connector assembly 200 and FIG. 8B is a partial cross- sectional view of the pogo pin connector of the pogo pin connector assembly 200.

[0081] As shown in FIGS. 8A-8B, the pogo pin connector assembly 200 may include a pogo pin connector 210 and a dielectric spacer 260. The pogo pin connector 210 is a tubular structure that includes a barrel 220, a plunger 230, and a spring 240. The barrel 220 has an open interior and a forward (or "distal") end 222 of the barrel 220 includes an opening 224. The spring 240 and a portion of the plunger 230 are received within the barrel 220. The plunger 230 includes a widened portion 232 that is within the barrel 220. The widened portion 232 may comprise a rear portion of the plunger 230. A forward (or "distal") end 234 of the plunger 230 extends through the opening 224 in the barrel 220. The barrel 220 includes an inner lip 226 (which defines the opening 224) that has a diameter that is smaller than a diameter of the widened portion 232 of the plunger 230, and hence the inner lip 226 traps the widened portion 232 of the plunger 230 within the interior of the barrel 220. The spring 240 biases the widened portion 232 of the plunger 230 against the inner lip 226 of the barrel 220. When a rearwardly directed force is applied to the plunger 230, the spring 240 is compressed and the plunger 230 moves further into the barrel 220. The spring 240 applies a forwardly directed force on the plunger 230. The barrel 220, plunger 230 and spring 240 may each be made of a conductive material, such as a metal. The pogo pin connector 210 may also include additional elements.

For example, as shown in FIG. 8B, the pogo pin connector 210 may include a metal ball 250 that is interposed between the spring 240 and the plunger 230 and/or an O-ring 228 that abuts the inner lip 226 of the barrel 220.

[0082] The pogo pin connector 210 may be mounted in the dielectric spacer 260. The dielectric spacer 260 may be used to electrically isolate the pogo pin connector 210 from surrounding structures, and/or to mount the pogo pin connector 210 in another structure such as, for example, a filter unit according to embodiments of the present invention. As shown in FIG. 8C, the pogo pin connector 210 may also include additional structures, such as a conductive pin 270. The conductive pin 270 may be positioned adjacent the distal end 234 of the plunger 230 and may act as an extension of the plunger 230 so that the plunger 230 may have any desired length. By including the conductive pin 270 in the pogo pin connector assembly 200, a single pogo pin connector 210 may be manufactured and pins 270 having different lengths may be provided that allow the pogo pin connector assembly 200 to make electrical connections over gaps having different distances.

[0083] FIG. 9 is a partial cross-sectional view illustrating a filter unit 300 according to embodiments of the present invention that includes a pogo pin connector assembly that electrically connects the filter unit 300 to a first external printed circuit board. As shown in FIG. 9, the filter unit 300 includes a first pogo pin connector assembly 200-1 and a resonant cavity RF filter 310. In the depicted embodiment, the pogo pin connector assembly 200-1 is identical to the pogo pin connector assembly 200 of FIGS. 8A-8C, and hence the elements thereof will be referred to using the reference numerals shown in FIGS. 8A-8C. The first external printed circuit board in FIG. 9 is one of the RF PA printed circuit boards 136 of the active circuit layer an opening in the EMI shield 124 of the active circuit layer 120 to form an electrical connection between the RF PA printed circuit board 136 and a port of the filter 310.

[0084] The filter 310 includes a metal housing 320 and an RF input port 340. The metal housing 320 includes a floor 322, at least one sidewall 324 and a cover 326 that together define an internal cavity. The floor 322 and the sidewalls may, for example, be a monolithic structure that is formed by die casting. The cover 326 may be a separate metal piece and may comprise a sheet metal cover in some embodiments. An opening 323 is provided in the floor 322 of the housing 320. The opening 323 provides access to a first internal chamber 330-1 that extends into the internal cavity. The first internal chamber 330-1 may be defined by internal walls 332 of the housing 320. The first internal chamber 330-1 may, for example, comprise a cylindrical tube that is open on one end. The input port 340 may comprise, for example, an end section of a conductive trace such as a metal trace of a stripline transmission line structure. The input port 340 may be positioned within the first internal chamber 330-1. It will be appreciated that the resonant cavity filter 310 may be a bidirectional device that performs filtering on signals transmitted by the active antenna module 100 and on signals received by the active antenna module 100. Here, the port 340 is an "input" port for signals transmitted by the active antenna module 100 (i.e., for downlink signals). It will be appreciated that for signals received by the active antenna module 100, port 340 will instead act as an "output" port. Thus, the port 340 may act as either an input port or an output port depending upon the direction of the signals travelling through the resonant cavity filter 310.

[0085] As is further shown in FIG. 9, the front surface of the EMI shield 124 includes an opening 370 that is aligned with the opening 323 in the floor 322 of the housing 320. The EMI shield 124 may include walls 380 that extend rearwardly from the opening 370 to define a passageway 382 having open ends and closed sidewalls. The passageway 382 may, for example, comprise a cylindrical tube that is defined by the walls 380. The first pogo pin connector assembly 200-1 is positioned between the input port 340 and the RF PA printed circuit board 136 to provide an electrical connection therebetween. A first portion of the first pogo pin connector assembly 200-1 is received within the passageway 382 of the EMI shield 124 and the remainder of the first pogo pin connector assembly 200-1 is received within the first internal chamber 330-1 of the resonant cavity filter 310. [0086] The dielectric spacer 260 of the first pogo pin connector assembly 200-1 may be inserted within the passageway 382 of the EMI shield 124 and may form an interference fit therewith. The dielectric spacer 260 therefore acts to hold the rear portion of the first pogo pin connector assembly 200-1 in a desired position and electrically isolates the first pogo pin connector assembly 200-1 from the EMI shield 124. The first pogo pin connector assembly 200- 1 further includes one or more additional dielectric spacers 262 which, in the depicted embodiment, are annular dielectric disks. These disks 262 may be mounted on the conductive pin 270 to hold the front portion of the first pogo pin connector assembly 200-1 in a desired position and to electrically isolate the first pogo pin connector assembly 200-1 from the internal walls 332 of the first internal chamber 330-1.

[0087] The distal end of the plunger 230 of the first pogo pin connector assembly 200-1 may contact a conductive structure 137 on the RF PA printed circuit board 136 such as, for example, a signal trace of an RF transmission line (e.g., a microstrip transmission line, a coplanar waveguide transmission line, a stripline transmission line, etc.). The conductive elements of the first pogo pin connector assembly 200-1 (e.g., the plunger 230, the metal ball 250, the spring 240, the barrel 220 and the conductive pin 270) form a conductive path that electrically connects the conductive structure 137 on the RF PA printed circuit board 136 to the input port 340 of the filter 310. The EMI shield 124 may be electrically connected to a ground plane of the RF PA printed circuit board 136. A first conductive gasket 350-1 may be positioned at the front edge of the opening 370 in the EMI shield 124. The first conductive gasket 350-1 may be a resilient conductive gasket 350-1 and may have a thickness such that a front edge of the first conductive gasket 350-1 extends forwardly with respect to a front surface of the EMI shield 124. The rear surface of the filter housing 320 may engage the first conductive gasket 350-1 so as to compress the first conductive gasket 350-1 when the filter unit 300 is mounted on the EMI shield 124. The first conductive gasket 350-1 may, therefor, provide an electrical connection between the EMI shield 124 and the filter housing 320 so that the ground plane of the RF PA printed circuit board 136 (which is electrically connected to the EMI shield 124) is electrically connected to the filter housing 320. As a result of the electrical connections between the ground plane of the RF PA printed circuit board 136 and (1) the EMI shield and (2) the filter housing 320, the walls 380 that define the passageway 382 in the EMI shield 124 and the internal walls 332 that define the first internal chamber 330-1 are maintained at electrical ground. Thus, the walls 332, 380 in conjunction with the first pogo pin connector assembly 200-1 form a stripline-like RF transmission line structure between the RF PA printed circuit board 136 and the input port 340 of filter 310.

[0088] The length of the conductive pin 270 is selected so that, when the first pogo pin connector assembly 200-1 is installed within the first internal chamber 330-1 of filter 310 and the passageway 382 of EMI shield 124, the plunger 230 of the first pogo pin connector assembly 200-1 will be forced rearwardly into the barrel 220, compressing the spring 240. The distal end 234 of the plunger 230 may rest on the conductive structure 137 on the RF PA printed circuit board 136. The spring 240 exerts a rearwardly directed force on the plunger 230 that maintains the plunger 230 in firm contact with the conductive structure 137 on the RF PA printed circuit board 136. This may ensure that a relatively low-PIM distortion electrical contact is formed between the input port 340 of filter 310 and the conductive structure 137 on the RF PA printed circuit board 136. The resilience of the first conductive gasket 350-1 likewise ensures that a relatively low-PIM distortion electrical contact is formed between the EMI shield 124 and the filter housing 320.

[0089] It will be appreciated that the first pogo pin connector assembly 200-1 and the first conductive gasket 350-1 are merely examples of possible spring-loaded members that may be used to electrically connect the input port 340 of filter 310 to an external structure. For example, other forms of spring-biased contacts may be used. It will also be appreciated that a wide variety of pogo pin connector designs may be used. For example, a double-plunger pogo pin connector assembly could be used that has plungers inserted into either side of the barrel in other embodiments. It will also be appreciated that the first pogo pin connector assembly 200-1 could be rotated 180° from the orientation shown in FIG. 9 so that the conductive pin 270 contacts the conductive structure 137 on the RF PA printed circuit board 136 and the pogo pin connector 210 contacts the input port 340. The orientation of the pogo pin connector 210 could likewise be rotated 180° (e.g., so that the barrel 220 contacts the RF PA printed circuit board 136 and the plunger 230 contacts the conductive pin 270). While the first pogo pin connector assembly 200-1 is shown in FIG. 9 as connecting to a conductive structure 137 on the RF PA printed circuit board 136, it will be appreciated that embodiments of the present invention are not limited thereto. For example, in other embodiments, the first pogo pin connector assembly 200-1 may connect the filter 310 to a different printed circuit board that includes active components, to a "passive" printed circuit board that does not include any active circuits thereon, or to a conductive structure other than a printed circuit board.

[0090] The filter unit 300 having the first pogo pin connector assembly 200-1 may have a number of advantages. First, the filter 310 may be electrically connected to the RF PA printed circuit board 136 by solderless connections. Eliminating soldered connections may significantly simplify the manufacturing process, as soldering is a labor-intensive operation. Moreover, since pogo pin connector assemblies are used to replace soldered connections, rework of a defective filter units becomes far simpler since the filter unit may be removed by simply removing some screws and a new filter unit may be installed in place of the defective unit. Additionally, eliminating the soldered connections also allows the filter unit to be mounted directly on the EMI shield, and the reflector to be mounted directly on the filter unit, since openings are no longer required for facilitating forming solder joints. The filter unit 300 may therefore have reduced manufacturing costs, may be manufactured more quickly and easily, and may be positioned more closely to other elements of the active antenna module 100.

[0091] The first pogo pin connector assembly 200-1 of filter unit 300 is used to form an electrical connection between the RF PA printed circuit board 136 and the input port 340 of the filter 310. Pursuant to further embodiments of the present invention, the filter unit 300 may alternatively or additionally include a second pogo pin connector assembly 200-2 that forms an electrical connection between an output port 342 of the filter 300 and an external structure such as, for example, a feed board printed circuit board 188 of the active antenna module 100. The second pogo pin connector assembly 200-2 of filter unit 300 is illustrated in FIGS. 10 and 11. In particular, FIG. 10 is a partial cross-sectional view of the filter unit 300, and FIG. 11 is a perspective view of a front portion of the pogo pin connector assembly of FIG. 10. FIGS. 12A and 12B are schematic plan views of the front and rear surfaces, respectively, of a small portion of the feed board printed circuit board 188 of FIG. 10.

[0092] Referring to FIG. 10, the housing 320 of filter 310 may include a second internal chamber 330-2 that has internal walls 332. The cover 326 of filter 310 may include an opening 327 that is aligned with the second internal chamber 330-2. The output port 342 may comprise, for example, a conductive trace such as a metal trace of a stripline transmission line structure.

The output port 342 may be positioned within the second internal chamber 330-2. [0093] As is further shown in FIG. 10, the reflector 182 of the active antenna module 100 is mounted in front of the filter 310, and a feed board printed circuit board 188 is mounted on the front side of the reflector 182. The reflector 182 includes an opening 183 that is aligned with the opening 327 in the cover 326 of filter 310. The second pogo pin connector assembly 200-2 is positioned between the output port 342 and the feed board printed circuit board 188 to provide an electrical connection therebetween. A first portion of the second pogo pin connector assembly 200-2 is received within the second internal chamber 330-2 of the filter 310 while the remainder of the second pogo pin connector assembly 200-2 extends out of the filter housing 320 and through the opening 183 in the reflector 182 to contact the feed board printed circuit board 188.

[0094] Referring to FIG. 12 A, the front surface of the feed board printed circuit board 188 includes a conductive pad 193 and a conductive trace 194 that extends from the conductive pad 193. The conductive trace 194 may, for example, connect (directly or indirectly) to one or more of the radiating elements 184 (FIG. 10). The feed board printed circuit board further includes a plurality of conductive vias 195 that extend through a dielectric layer 196 of the feed board printed circuit board 188. Referring to FIG. 12B, the rear surface of the feed board printed circuit board 188 includes a conductive pad 197 and a conductive ground plane 198 that are separated by an annular gap in which no metal is formed (thereby exposing the dielectric layer 196). The conductive vias 195 that extend through the dielectric layer 196 of the feed board printed circuit board 188 electrically connect the conductive pad 197 on the rear surface of feed board 188 to the conductive pad 193 on the front surface of feed board 188. Thus, an electrical signal input to conductive pad 197 may pass from the rear surface of the feed board 188 to the front surface thereof through the pads 197, 193 and the conductive vias 195.

[0095] Referring again to FIG. 10, the dielectric spacer 260 of the second pogo pin connector assembly 200-2 may be inserted within the second internal chamber 330-2 in the filter housing 320 and may form an interference fit therewith. The dielectric spacer 260 therefore acts to hold the rear portion of the second pogo pin connector assembly 200-2 in a desired position and electrically isolates the second pogo pin connector assembly 200-2 from the filter housing 320. An O-ring 264 may be mounted on the dielectric spacer to help protect against moisture ingress into the filter housing 320. [0096] The distal end of the plunger 230 of the second pogo pin connector assembly 200-2 may contact the output port 342, and the base of the barrel 220 may contact the conductive pad 197 on the rear surface of the feed board printed circuit board 188. Note that in the depicted embodiment the second pogo pin connector assembly 200-2 does not include a conductive pin 270, although such a conductive pin 270 could be included in other embodiments. The conductive elements of the second pogo pin connector assembly 200-2 form a conductive path that electrically connects the conductive structure 197 on the rear surface of the feed board 188 to the output port 342 of the filter 310. It will be appreciated that the pogo pin connector assembly 200-2 could be rotated 180° from the orientation pictured in FIG. 10 in other embodiments.

[0097] Referring to FIGS. 10 and 11, an annular sleeve 328 may be mounted in the cover 326. The annular sleeve 328 may be formed of metal, and may be interference fit within the cover 326. A portion of the second pogo pin connector assembly 200-2 (here, the barrel 220) extends through the center of the annular sleeve 328. A base of the annular sleeve 328 that is adjacent the cover 326 has a first internal diameter and a distal end of the annular sleeve 328 has a second internal diameter that is larger than the first internal diameter. A second conductive gasket 350-2 is mounted in the distal end of the annular sleeve 328 (i.e., in the portion with the larger internal diameter). The second conductive gasket 350-2 may be an annular conductive gasket.

[0098] The second conductive gasket 350-2 may be a resilient conductive gasket and may have a thickness such that a front edge of the second conductive gasket 350-2 extends forwardly past a forward edge of the annular sleeve 328. The rear surface of the reflector 182 may engage the second conductive gasket 350-2 so as to compress the second conductive gasket 350-2 when the reflector 182 is mounted on the filter unit 300. The second conductive gasket 350-2 may, therefore, provide an electrical connection between the filter housing 320 and the reflector 182 so that the reflector and the filter housing 320 are at a common ground potential. A ground plane 198 on the rear surface of the feed board printed circuit board 188 may be capacitively coupled to the reflector 182 through a solder mask (not shown).

[0099] The second pogo pin connector assembly 200-2 acts as the signal conductor of an RF transmission line structure, and the internal walls 332 of the second internal chamber 330-2, the cover 326, the annular sleeve 328, the second conductive gasket 350-2, the reflector 182 and the ground plane 198 of the feed board printed circuit board 188 act as the ground conductor of the RF transmission line structure. The RF transmission line structure may act like a stripline transmission line structure since the signal conductor is substantially surrounded by the ground conductor.

[00100] The spring bias of the second pogo pin connector assembly 200-2 ensures that a good electrical connection is provided between the output port 342 of filter 310 and the conductive pad 197 on the rear surface of the feed board 188. Similarly, the resilience of the second conductive gasket 350-2 likewise ensures that a good electrical connection is formed between the filter cover 326 and the reflector 182. This may ensure that the electrical connections between the filter unit 300 and the feed board printed circuit board 188 are relatively low-PIM distortion electrical connections.

[00101] The second pogo pin connector assembly 200-2 and the second conductive gasket 350-2 are spring-biased connections that apply forces to the external circuit. If both the second pogo pin connector assembly 200-2 and the second conductive gasket 350-2 are configured to contact the feed board printed circuit board 188, then the combined spring force may be sufficient to push the feed board printed circuit board 188 away from the reflector 182, which is undesirable for both mechanical and electrical performance reasons. By having the second conductive gasket 350-2 contact the reflector 182 as opposed to the feed board printed circuit board 188, the amount of force applied to the feed board printed circuit board 188 may be reduced in order to avoid the problem of too much force being applied to the feed board printed circuit board 188.

[00102] While the above example (FIGS. 10-12) describes an embodiment in which the second pogo pin connector assembly 200-2 forms an electrical connection between the output port 342 of filter 310 and a conductive pad 197 on a feed board 188, it will be appreciated that embodiments of the present invention are not limited thereto. For example, in other embodiments, the second pogo pin connector assembly 200-2 may connect to a printed circuit board that is not a feed board (e.g., a calibration circuit board). Likewise, while the above example depicts an embodiments where a feed board 188 is mounted on the front surface of a reflector 182, it will be appreciated that in other embodiments, the feed board 188 or other printed circuit board may be mounted behind the reflector 182 or, in some cases, a pair of printed circuit boards (e.g., a calibration printed circuit board and a feed board) may be provided, with one of the printed circuit boards behind the reflector 182 and the other printed circuit board in front of the reflector 182, and the second pogo pin connector assembly 200-2 may connect to one of these printed circuit boards. The two printed circuit boards may be electrically connected to each other by, for example, board-to-board connectors.

[00103] FIG. 13 is a schematic cross-sectional view of the filter unit 300 of FIGS. 9-11 that illustrates the various spring-biased connections. FIG. 13 illustrates the relationship between the respective first and second pogo pin connector assemblies 200-1, 200-2 shown in FIGS. 9 and 10. In particular, as shown in FIG. 13, the first and second pogo pin connector assemblies 200-1, 200-2 may be connected by a transmission line 312 of the resonant cavity filter in some embodiments. The first pogo pin connector assembly 200-1 connects a first side of the filter (here the rear of the filter 310, which is the floor 322) to a first external circuit (RF PA printed circuit board 136) while the second pogo pin connector assembly 200-2 connects a second, opposed side of the filter (here the cover 326 of the filter 310) to a second external circuit (feed board printed circuit board 188). The cover 326 may include screws 329 mounted therethrough that are used to attach the cover 326 to the remainder of the filter housing 320. Rivets 189 may be used to attach the feed board printed circuit board 188 to the reflector 182. As is further shown in FIG. 13, a third resilient conductive gasket 350-3 may be provided that electrically connects a ground region on the front surface of the RF PA printed circuit board to the walls 382 of the EMI shield 124 (the third conductive gasket 350-3 was not illustrated in FIG. 9 for convenience). As the remaining elements of FIG. 13 have been described previously with reference to FIGS. 9-11, further description of FIG. 13 will be omitted.

[00104] It will be appreciated that many modifications may be made to the above- described filter units (and active antenna modules that include such filter units) without departing from the scope of the present invention. For example, in the above-described embodiments, the RF input port 340 and the RF output port 342 are both within the internal cavity of the resonant cavity filter (namely in the internal chambers 330-1 and 330-2). In other embodiments, the RF input port 340 and/or the RF output port 342 may extend outside of the filter housing 320, and the corresponding pogo pin connector assemblies 200 may not extend into the metal housing 320.

[00105] 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.

[00106] 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.

[00107] 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.).

[00108] 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.

[00109] 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.

[00110] 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.