The present application claims priority under 35 U.S.C. § 119 from Chinese Patent Application Serial No. 201610930225.6, filed Oct. 31, 2016, the entire content of which is incorporated herein by reference.
The present invention relates generally to communications systems and, more particularly, to filtering devices that are suitable for use in cellular communications systems.
Cellular base stations are well known in the art and typically include, among other things, baseband equipment, radios and antennas.
Cellular base stations often use phased array antennas to provide increased antenna gain and/or to allow frequency reuse within a cell. A typical phased array antenna 32 may be implemented as one or more columns of radiating elements mounted on a panel, with perhaps ten radiating elements per column. Typically, each radiating element in a column is used to (1) transmit radio frequency (“RF”) signals that are received from a transmit port of an associated radio 24 and (2) receive RF signals from mobile users and feed such received signals to the receive port of the associated radio 24. Duplexers are typically used to connect the radio 24 to each respective radiating element of the antenna 32. A “duplexer” refers to a three-port filtering device that is used to connect both the transmit and receive ports of a radio to an antenna (or to one or more radiating elements thereof). The duplexer isolates the RF transmission paths to the transmit and receive ports of the radio from each other while allowing both RF transmission paths access to the antenna. In other words, a duplexer separates RF signals flowing in one direction based on the frequency thereof while allowing signals in the full frequency range to flow in the opposite direction. Typically, the transmit and receive frequency ranges are very close to each other, and the combination of the transmit and receive frequencies are considered to be a single frequency “band.”
In some cases, the radiating elements on a phased array antenna may comprise “wideband” radiating elements. Such wideband radiating elements may be used to transmit and receive RF signals in two or more different frequency bands. When wideband radiating elements are used, two or more radios that operate in different frequency bands may be coupled to the same column of radiating elements of a phased array antenna. RF diplexers or multiplexers may be used to separate the RF signals received at the radiating elements from each other for delivery to the respective radios, and to combine signals transmitted from the different radios for delivery to the radiating elements. When such wideband radiating elements are used, the antenna will typically include both diplexers for separating/combining signals in the different frequency bands and duplexers for separating/combining the transmit and receive paths within each frequency band.
As base station antennas become more complex to support a greater number of cellular services, the number of diplexers, duplexers, multiplexers and other filtering devices integrated into the antenna or otherwise provided on the tower has proliferated. Consequently, the size, weight and cost of these filtering devices has become an increasing concern. The trend to an increasing number of filtering devices has been exacerbated by the widespread incorporation of remote electronic tilt (“RET”) capabilities into base station antennas. With RET antennas, the effective tilt or “elevation” angle of the antenna beam can be adjusted electronically by, for example, controlling phase shifters that adjust the phase of the signal fed to each radiating element (or to sub-arrays of radiating elements) of the antenna 32. The phase shifters and other related circuitry are typically built into the antenna 32 and can be controlled from a remote location. This capability greatly simplifies the process of changing the effective coverage area for a base station antenna, as is often done as new base stations are brought into service in adjacent regions.
A RET antenna typically has both transmit and receive path phase shifters so that the tilt on each sub-band may be independently controlled. The transmit path phase shifters perform power dividing so that a single signal from a radio may be provided to multiple radiating elements or sub-arrays of radiating elements (with a phase shifter dividing the RF signal into five to seven sub-components being typical). The receive path phase shifters perform power combining so that the signals received at the radiating elements may be combined and fed to the receive port of the radio. As separate transmit and receive phase shifters are used, the duplexers that are used to allow each radiating element to both transmit and receive signals must necessarily be located along the RF transmission path between the phase shifters and the radiating elements. Thus, if each phase shifter performs, for example 1:7 power division, then seven duplexers are required for each pair of transmit and receive phase shifters. This further expands the number of filtering devices that are included in the antenna.
Conventionally, resonant cavity filtering devices have been used to implement the above-described duplexers, diplexers, multiplexers and other filtering devices for base station antennas. Resonant cavity filtering devices may be highly reliable and may provide sharp frequency responses. However, they also tend to be relatively large and heavy, and may be expensive to manufacture.
Referring to
The conventional duplexer 50 of
Pursuant to embodiments of the present invention, suspended microstrip filtering devices are provided that include a printed circuit board having a substrate with at least one resonator thereon; a ground plate; and an insulating separator interposed between the printed circuit board and the ground plate, the insulating separator having a plurality of air-filled openings. In some embodiments, the at least one resonator is electrically floating.
In some embodiments, the printed circuit board is a first printed circuit board, the filtering device further includes a second printed circuit board that is spaced apart from and in a vertically stacked relationship with the first printed circuit board, and the second printed circuit board also includes at least one resonator thereon.
In some embodiments, the suspended microstrip filtering device further includes a third printed circuit board between the first printed circuit board and the second printed circuit board, where the ground plate comprises a conductive layer on a top surface of the third printed circuit board, and the third printed circuit board further includes a conductive layer on a bottom surface thereof that forms a second ground plate. In such embodiments, the insulating separator may be between the first printed circuit board and the third printed circuit board, and the suspended microstrip filtering device may further include a second insulating separator that has a plurality of air-filled openings between the second printed circuit board and the third printed circuit board.
In some embodiments, the insulating separator may be between the first printed circuit board and the third printed circuit board, and the suspended microstrip filtering device may further include a second insulating separator that has a plurality of air-filled openings between the second printed circuit board and the third printed circuit board. In some embodiments, the at least one resonator on the first printed circuit board may comprise a plurality of resonators that together form a first filter, and the at least one resonator on the second printed circuit board may comprise a plurality of resonators that together form a second filter, the first and second filters together forming the suspended microstrip filtering device.
In some embodiments, the first printed circuit board may have a first input/output port that is connected to a first microstrip transmission line on the third printed circuit board by a first jumper and a second input/output port that is connected to a second microstrip transmission line on the third printed circuit board by a second jumper.
In some embodiments, the suspended microstrip filtering device may further include a housing having a top cover, a bottom cover and at least one sidewall, the top cover, the bottom cover and the at least one sidewall defining an internal cavity. In some embodiments, the printed circuit board may extend outside the housing through an opening in the housing. In some embodiments, the housing may have an internal ledge, and at least one of the printed circuit board and the insulating separator may be mounted on the internal ledge.
In some embodiments, the insulating separator may have a fishnet pattern.
In some embodiments, the at least one resonator may comprise a plurality of resonators, and the suspended microstrip filtering device may further include a slidable tuning stub that is configured to capacitively couple with a first of the resonators. The slidable tuning stub may comprise, for example, a tuning element in the form of a conductive strip disposed on a tuning stub substrate, and the tuning stub substrate may be configured to slide on the first of the resonators and separate the conductive strip from the first of the resonators. In some embodiments, the slidable tuning stub may further include a tuning stub mounting structure that slidably mounts the tuning element above the first of the resonators.
In some embodiments, the slidable tuning stub may be configured to slide along a longitudinal axis of the first of the resonators. In other embodiments, the slidable tuning stub may be configured to slidably rotate above the first of the resonators.
In some embodiments, the suspended microstrip filtering device may be a multiplexer, a duplexer or a diplexer.
In some embodiments, the suspended microstrip filtering device may further include at least one metallic jumper that connects a conductive line input/output port of the device to a conductive line on a second printed circuit board. The metallic jumper may comprise, for example, a bent strip of metal.
Pursuant to further embodiments of the present invention, microstrip filtering devices are provided that include a substrate having a resonator thereon and a slidable tuning stub that is configured to capacitively couple with the resonator.
In some embodiments, the slidable tuning stub may comprise a tuning element in the form of a conductive strip disposed on a tuning stub substrate.
In some embodiments, the tuning stub substrate may be configured to slide on the resonator and to separate the conductive strip from the resonator.
In some embodiments, the slidable tuning stub may further include a tuning stub mounting structure that slidably mounts the tuning element above the first of the resonators. In some embodiments, the tuning stub mounting structure may comprise a clamp, a bolt and a nut.
In some embodiments, the slidable tuning stub may be configured to slide along a longitudinal axis of the resonator. In other embodiments, the slidable tuning stub may be configured to slidably rotate above the resonator.
In some embodiments, the substrate and the resonator may be part of a first printed circuit board, and the microstrip filtering device may further include a ground plate and an insulating separator interposed between the first printed circuit board and the ground plate, the insulating separator having a plurality of air-filled openings. In such embodiments, the microstrip filtering device may further include a second printed circuit board that is spaced apart from and in a vertically stacked relationship with the first printed circuit board, and the second printed circuit board may include at least one resonator thereon. In some embodiments, the device may further include a third printed circuit board between the first printed circuit board and the second printed circuit board, the ground plate may comprise a conductive layer on a top surface of the third printed circuit board, and the third printed circuit board may further include a conductive layer on a bottom surface thereof that forms a second ground plate.
As the number of cellular users and the amount of data transmitted and received by these users continues to rapidly increase, wireless operators are constantly looking for ways to increase throughput. Wireless operators have purchased additional wireless spectrum, but even the deployment of additional frequency bands and types of service has been insufficient to keep up with the growing demand. Accordingly, wireless operators are also aggressively taking steps to increase the throughput of existing wireless resources. One way to achieve this is to deploy a number of remote cellular sites that are smaller than traditional base stations that use frequency division multiplexers to divide the total available bandwidth into a series of non-overlapping frequency bands. This approach may significantly increase the available throughput, but it may be important that the remote sites be less expensive than a traditional base station while still providing high performance.
In the above-described cellular communications systems, the cellular sites may employ frequency division multiplexers to ensure that each remote site only transmits and receive signals on a subset of the total available bandwidth. Frequency division multiplexers are a known type of RF filtering device that allows input RF signals in selected frequency bands to pass to respective outputs. In its simplest form, a frequency division multiplexer may comprise a three port device that has a common input and first and second outputs. When RF signals are received at the common input, only signals in a first frequency range are passed to the first output while frequencies in a second frequency range are passed to the second output. Such three port filtering devices are referred to as diplexers if the first and second frequency ranges are part of different frequency bands, and as duplexers if the frequency ranges are the transmit and receive sub-bands of the same frequency band. Diplexers and duplexers also work as combiners in the opposite direction, combining the signals received at the first and second outputs and passing the combined signal to the common input.
Ideally, a frequency division multiplexer such as a diplexer will be relatively small, lightweight and low cost, and will also exhibit low losses. In practice however, in order to achieve small insertion losses and sharp frequency responses it has been necessary to implement frequency division multiplexers for cellular systems using metallic waveguide and/or resonant cavity filter technologies. These types of multiplexers tend to be larger, heavier and more expensive.
Embodiments of the present invention provide small, light, low cost and easily manufactured and assembled filtering devices that can be used as duplexers, diplexers, multiplexers and/or as other filtering devices for cellular communications systems and other applications. The filtering devices according to embodiments of the present invention may comprise microstrip filtering devices that are implemented using printed circuit board based resonators which may reduce the cost and weight of the device. Microstrip refers to a type of RF transmission line that may be implemented using printed circuit board technology. Microstrip consists of a conductive strip that is separated from a ground plane by a dielectric layer. Since microstrip may be formed simply by patterning printed circuit board metal layers it may be smaller, lighter and cheaper than conventional waveguide technology. The microstrip filtering devices according to embodiments of the present invention may exhibit low insertion loss values and may be readily tunable over a broad range of frequencies.
In some embodiments, the microstrip filtering devices may include a printed circuit board that comprises a dielectric substrate that has at least one conductive resonator thereon. Herein a printed circuit board that includes at least one resonator may be referred to as a “resonator printed circuit board.” A conductive ground plate may be disposed on a side of the dielectric substrate of the resonator printed circuit board that is opposite the resonator. An insulating separator is interposed between the dielectric substrate of the resonator printed circuit board and the ground plate. The insulating separator has a plurality of air-filled openings. By using an insulating separator that includes air-filled openings to separate the resonator printed circuit board and the ground plate, the filtering device has a “suspended microstrip” configuration. This suspended microstrip configuration may reduce the insertion loss of the filtering device, as the air space between the resonators and the ground plate may reduce the dissipation loss of the filtering device. In some embodiments, the insulating separator may comprise a dielectric material formed in a fishnet grid, but any suitable insulating separator that includes air filled openings may be used.
In some embodiments, an optional housing may be provided. The housing may comprise top and bottom cover plates and, in some embodiments, one or more sidewalls. When a housing is provided, the top and/or bottom cover plates may act as the ground plate of the filtering device.
In some embodiments, the suspended microstrip filtering devices may include a plurality of printed circuit boards that are arranged in a stacked relationship. For example, in some embodiments, the microstrip filtering device may comprise first and second printed circuit boards, each of which comprise a substrate having one or more resonators thereon. An insulating separator that has a plurality of air-filled openings is interposed between the first and second printed circuit boards. Top and bottom cover plates may be provided that act as the ground plates for the filtering device. In other embodiments, one or more ground plates may be inserted between the first and second printed circuit boards. In such embodiments, a first insulating separator that has a plurality of air filled openings is interposed between the first printed circuit board and the ground plate(s) and a second insulating separator that has a plurality of air filled openings is interposed between the second printed circuit board and the ground plate(s). The ground plate(s) may comprise, for example, a pair of printed circuit board ground plates that are formed on either side of a substrate of a third printed circuit board. A printed circuit board that includes a ground plate on at least one side thereof may be referred to herein as a “ground plate printed circuit board.” The ground plate printed circuit board may include other elements of the antenna such as phase shifters, feed lines or the like and may provide a convenient way to integrate the microstrip filtering devices according to embodiments of the present invention with other elements of a base station antenna in a low-loss, easy to manufacture assembly.
Pursuant to still further embodiments of the present invention, microstrip filtering devices are provided that include slidable tuning stubs. These slidable tuning stubs may comprise conductive strips formed on a dielectric substrate that are slidable relative to an underlying resonator. As the tuning stub moves relative to the underlying resonator, the amount of overlap between a conductive strip of the tuning stub and the resonator varies, which in turn varies the effective length of the resonator. By changing the effective length of the resonator, one or more resonant frequencies of the microstrip filtering device may be adjusted. In some embodiments, the slidable tuning stubs may slide longitudinally over top of respective resonators. In other embodiments, the slidable tuning stubs may slide rotationally over top of the respective resonators.
The shape and relative locations of the resonators, the distances between the resonator printed circuit boards and the ground plates and the distances between the resonator printed circuit boards can be designed to provide a microstrip filtering device having a desired filter (frequency) response. If a housing is provided, it can be implemented, for example, as a frame that forms the sidewalls of the housing and a pair of planar metal sheets that act as top and bottom covers that are soldered to the frame. The frame may be manufactured by, for example, die-casting or by using computer numerical control (“CNC”) machines or a cross section stretch process. One or more resonator printed circuit boards may be mounted within a cavity defined by the housing. In some embodiments, one or more ledges may extend around the interior of the frame, and the resonator printed circuit board(s) and/or insulating separator may be mounted on these ledges.
In some embodiments, the microstrip filtering devices may comprise three port devices such as RF duplexers or diplexers. In other embodiments, the microstrip filtering devices may include additional ports to implement multiplexers, triplexers or the like.
The microstrip filtering devices according to embodiments of the present invention may be readily integrated into other microstrip systems of a base station antenna or other RF device. For example, a resonator printed circuit board or a ground plate printed circuit board of the microstrip filtering devices according to embodiments of the present invention may be mounted on a printed circuit board that includes other printed circuit based elements of the antenna such as, for example, phase shifters or feed structures for sub-arrays or individual radiating elements, or even radio components such as mixers or amplifiers. By integrating multiple components on a monolithic printed circuit board it may be possible to further reduce insertion losses and/or to improve passive intermodulation (“PIM”) distortion performance, as will be explained in greater detail below.
Embodiments of the present invention will now be described in greater detail with reference to
One way to reduce the size, weight and cost of the wireless communications system 100 of
As shown in
The insulating separator 340 may be any suitable structure that separates the microstrip printed circuit board 310 from the ground plate 350. In the depicted embodiment, the insulating separator 340 comprises a grid structure 342 that may be formed of a dielectric material. Openings 344 that are defined by the grid structure 342 may be air-filled openings. While the grid structure 342 comprises one example of an insulating separator, it will be appreciated that a wide variety of insulating separators 340 may be used. For example, as shown in
Referring again to
The conductive traces 330 may include a plurality of resonator traces 332 and input/output traces 334. The resonator traces 332 may be implemented, for example, as half-wavelength resonators or as quarter wavelength resonators. When quarter wavelength resonators are used, one end thereof may be electrically shorted to the ground plate 350 (e.g., for bandpass filters) or may be floating (e.g., for some band stop filters) In the depicted embodiment, half wavelength resonators 332 are provided. The input/output traces 334 may connect to other structures of, for example, an antenna in which the microstrip filtering device 300 is included. These connections may be direct connections or intervening structures may be interposed therebetween.
As is known to those of skill in the art, the insertion loss of an RF device refers to the amount of RF power that is lost as a result of interposing the RF device along an RF transmission line. RF power is lost when an RF signal traverses a microstrip printed circuit board due, for example, to coupling of the RF signal to the ground plane of the microstrip printed circuit board. Air has a very low loss constant, and hence by providing a primarily air dielectric between the conductive traces and the ground plane of the microstrip filtering device 300, the insertion loss of the filtering device 300 may be reduced as compared to conventional microstrip filtering devices.
The filtering device 400 differs from the filtering device 300 in that it includes multiple printed circuit boards 410-1, 410-2 that are layered to form a multi-layer structure. As shown in
As is further shown in
The resonators 432 on the first and second printed circuit boards 410-1, 410-2 form microstrip structures with the respective top cover 462 and bottom cover 464 act as the ground planes, with an air dielectric being interposed between the resonators 432 and their respective ground planes. The insulating separator 440 having the fishnet grid structure that is interposed between the printed circuit boards 410-1, 410-2 helps reduce the insertion loss for the filtering device 400. In some embodiments, the printed circuit boards 410-1, 410-2 may not be electrically connected to the housing 460.
As noted above, conventional microstrip filtering devices may exhibit unacceptably high insertion losses. The suspended microstrip filtering device 400 may reduce these losses through the use of air dielectrics between the conductive traces 430 and the respective ground planes and through the use of the fishnet grid separator 440 that separates the printed circuit boards 410-1, 410-2 from each other. Another potential problem with conventional microstrip filtering devices is that they lacked tuning structures. Consequently, once a conventional microstrip filtering device was fabricated, it generally was not possible to tune characteristics of the device such as the location of pass bands and stop bands. Pursuant to embodiments of the present invention, tunable microstrip filtering devices are provided. FIGS. 15-18 illustrate two example implementations of slidable microstrip filtering device tuning structures according to embodiments of the present invention.
Referring first to
As can best be seen in
The dielectric layer 574 is thin so the conductive layer 576 couples strongly with its associated underlying resonator 532. Consequently, each tuning element 572 effectively extends the length of its associated resonator 532. The effective length of each resonator 532 is a function of the actual length of the resonator 532, the actual length of the portion of the tuning element 572 that does not overlap the resonator 532 and the amount of coupling between the resonator 532 and the tuning element 572. The amount of coupling between the resonator 532 and the tuning element 572 is a function of the distance between therebetween (which is the thickness of the dielectric layer 574), the amount of overlap between resonator 532 and the tuning element 572, and the dielectric constant of the dielectric layer 574. Accordingly, by sliding a tuning element 572 longitudinally along the resonator 532 the effective length of a resonator 532 may be changed.
In order to slide a tuning element 572, the nuts 586 of its tuning stub mounting structure 580 are loosened, thereby loosening the plastic clamps 582. The tuning element 572 may then slide longitudinally along its respective resonator 532. Thus, a technician can readily adjust the length of each resonator 532 in order to tune the filtering device. Once a tuning element 572 is at a desired level of overlap with its associated resonator 532, the nut 586 for that tuning element 572 may be tightened to hold the tuning element 572 in that location.
Referring to
Pursuant to further embodiments of the present invention, suspended microstrip filtering devices are provided that may be integrated into other microstrip systems within a cellular base station.
Referring to
The length of the resonators 616, 626, the distance between adjacent resonators 616, 626, the number of the location of the resonators 616, 626 may determine, at least in part, the frequency response of the filtering device 600.
The first printed circuit board 610 includes a first input/output port 618-1 and a second input/output port 618-2. The first input/output port 618-1 may be electrically connected to a common port for the filtering device 600, and the second input/output port 618-2 may be electrically connected to a low frequency port for the filtering device 600, as will be described below. The second printed circuit board 620 includes a first input/output port 628-1 and a second input/output port 628-2. The first input/output port 628-1 may be electrically connected to the common port for the filtering device 600 and the second input/output port 628-2 may be electrically connected to a high frequency port for the filtering device 600, as will also be described below. The third printed circuit board 630 includes three input/output ports 640, 642, 644. Port 640 may comprise the common port for filtering device 600, port 642 may be the low frequency port for filtering device 600, and port 644 may be the high frequency port for filtering device 600.
A first conductive jumper 660-1 connects port 618-1 to port 640. A second conductive jumper 660-2 connects port 618-2 to port 642. A third conductive jumper 660-3 connects port 628-1 to port 640. A fourth conductive jumper 660-4 connects port 628-2 to port 644. Port 642 may be connected (either directly or indirectly) to, for example, the receive port of a radio (not shown). Port 644 may be connected (either directly or indirectly) to, for example, the transmit port of the radio. Port 640, which is the common port of diplexer 600, may be connected to, for example, a radiating element of an antenna or a sub-array of radiating elements.
In the above-described manner, a first conductive path may be formed that extends from the common port 618-1 of the low frequency filter 602 to common port 640 on the printed circuit board 630 using conductive jumper 660-1. Likewise, a second conductive path may be formed that extends from the common port 628-1 of the high frequency filter 604 to solder pad 670 using conductive jumper 660-3. The solder pad 670 is connected to the common port 640 on the printed circuit board 630 though the metal-filled hole 674. In other words, the conductive jumpers 660-1, 660-3 may be used to connect the common ports 618-1, 628-1 of the respective low frequency and high frequency filters 602, 604 to the common port 640 on the printed circuit board 630. Conductive jumper 660-2 may similarly be used to connect the low frequency port 618-2 of the low frequency filter 602 to the low frequency port 642 on the third printed circuit board 630, and conductive jumper 660-4 may be used to connect the high frequency port 628-2 of the high frequency filter 604 to the high frequency port 644 on the third printed circuit board 630.
As shown best in
While the diplexer 600 includes two printed circuit boards having filters formed thereon that are separated by a third “ground plane” printed circuit board, it will be appreciated that one or more additional printed circuit boards having resonators or ground planes formed thereon may be included in other embodiments.
As discussed above, the suspended microstrip filtering devices according to embodiments of the present invention may readily be integrated into other microstrip systems. For example, a duplexer 600′ according to embodiments of the present invention may have the same general design as the suspended microstrip diplexer 600 discussed above with reference to
As shown in
The filtering devices according to embodiments of the present invention may provide a number of advantages over conventional filtering devices. As discussed above, microstrip filtering devices may be smaller, lighter and less costly to manufacture as compared to conventional resonant cavity filtering devices. Additionally, the filtering devices according to embodiments of the present invention may exhibit good PIM distortion performance. As is known in the art, PIM distortion may occur when two or more RF signals encounter non-linear electrical junctions or materials along an RF transmission path. Such non-linearities may act like a mixer causing new RF signals to be generated at mathematical combinations of the original RF signals. If the newly generated RF signals fall within the bandwidth of existing RF signals, the noise level experienced by those existing RF signals is effectively increased. When the noise level is increased, it may be necessary reduce the data rate and/or the quality of service. PIM distortion can be an important interconnection quality characteristic for an RF communications system, as PIM distortion generated by a single low quality interconnection may degrade the electrical performance of the entire RF communications system. Thus, ensuring that components used in RF communications systems will generate acceptably low levels of PIM distortion may be desirable.
One possible source of PIM distortion is an inconsistent metal-to-metal contact along an RF transmission path. Referring again to
Additionally, if screws are used to assemble a filtering device, when the screws are tightened, small metal shavings may be torn away from outer surfaces of the screws and/or from inner surfaces of the internally-threaded holes that receive the screws. Such metal shavings are another well-known source of PIM distortion in RF components, and may be particularly troubling as the metal shavings can move around inside the filtering device resulting not only in increased PIM distortion, but PIM distortion levels that can change over time in unpredictable ways. If increased PIM distortion levels are identified during a PIM distortion test during qualification of a particular unit, then the filtering device in question can be opened and cleaned to remove the metal particles. However, if the metal particles are not initially detected it can be a significant problem, as PIM distortion may arise later after the filtering device has been installed, for example, on an antenna that is mounted on a cell tower, requiring a very expensive replacement operation, downtime of the cellular base station, etc. It should be noted that the use of slidable tuning stubs in place of tuning screws may avoid generation of metal shavings within the device that could otherwise result from adjustment of tuning screws.
While in the above-described embodiments that include multiple printed circuit boards, the printed circuit boards are stacked vertically to have a top printed circuit board, a bottom printed circuit board and perhaps one or more intervening printed circuit boards, it will be appreciated that embodiments of the present invention are not limited to this arrangement. For example, in other embodiments, the printed circuit boards may be arranged in a housing in a side-by-side relationship.
The filtering devices described herein may be conventional from an equivalent circuit viewpoint in that they may have resonators and cross-couplings that are conventional in nature and which provide a conventional frequency response. However, the mechanical design of the filtering devices according to embodiments of the present invention may be much simpler than conventional filtering devices used in base station antennas and various other applications so that the filtering devices may have far fewer parts, a smaller physical footprint, are lighter weight than conventional filtering devices and far easier to manufacture and assemble.
It will be appreciated that a wide variety of filtering devices may be implemented using the above-described techniques. Thus, while the description above primarily focuses on three port filtering devices such as diplexers, it will be appreciated that more complex filtering devices such as triplexers, multiplexers and the like may be implemented using the techniques described herein.
While the description above focuses on microstrip filtering devices for base station antennas, it will be appreciated that embodiments of the present invention may be implemented into other RF systems without departing from the scope of the present invention. For example, the filtering devices described herein could be used in other types of antenna systems, in wired RF systems and various other applications.
The present invention has been described above with reference to the accompanying drawings, in which certain 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.
In the above description, multiple instances of certain elements may be included in the embodiments shown in the figures. When this is the case, these elements may be referred to individually by a reference number that includes a dash (e.g., printed circuit boards 410-1 and 410-2), and may be referred to collectively by only the first portion of their reference number (e.g., the printed circuit boards 410).
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that when an element (e.g., a device, circuit, etc.) 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.
In the drawings and specification, there have been disclosed typical embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.
Number | Date | Country | Kind |
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201610930225.6 | Oct 2016 | CN | national |
Filing Document | Filing Date | Country | Kind |
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PCT/CN2017/101668 | 9/14/2017 | WO | 00 |