Patent Grant
11145978
The present invention relates to wireless communications and, more particularly, to phased array antennas suitable for use in cellular base stations.
Base station antennas for wireless base stations typically comprise one or more arrays of radiating elements such as dipoles that are mounted on, for example, a flat panel. Each array of radiating elements may produce an antenna beam that has desired characteristics such as, for example, a desired beam elevation angle, beam azimuth angle, and/or half power beam width. A signal that is to be transmitted by such a base station antenna is divided into multiple sub-components, and each sub-component may be fed through an antenna feed network to a respective one of the radiating elements.
Cellular operators are constantly looking for ways to increase network throughput to accommodate ever increasing subscriber traffic levels. Based on network coverage requirements, operators may find it advantageous to adjust the vertical elevation angle (i.e., the vertical angle of the antenna with respect to the horizon) or “tilt” of the main beam of a base station antenna in order to change the coverage area of the antenna. Such adjustment is typically referred to as “down-tilting” as the antenna is almost always tilted to point at an elevation angle of 0° or less with respect to the horizon such as, for example, an elevation angle of 0° to −10°, although down-tilts as large as 30° or more are used in some applications.
The tilt of a base station antenna may be adjusted mechanically and/or electrically. Mechanical tilt is implemented by physically adjusting the elevation angle of the antenna, either manually or by remote control of a motorized structure. Manual mechanical adjustment typically requires that a technician climb an antenna tower to physically adjust the tilt of the antenna, which can be expensive in practice. Remotely controlled mechanical adjustment avoids the tower climbs, but requires additional and/or more complex structures on the antenna tower such as motorized antenna mounts that are more expensive, increase the weight at the top of the tower, and/or result in more items of equipment that can potentially fail. Moreover, mechanically down-tilting an antenna causes the radiation that is emitted backwardly from the antenna (i.e., toward the flat panel) to be tilted upwardly, which is undesirable for several reasons. Thus, mechanical down-tilting of an antenna may be less than ideal in many applications.
A phased array antenna may be electrically down-tilted by controlling the phases of the sub-components of a signal that are transmitted through each radiating element of the array in a manner that changes the elevation angle of the main antenna beam. Such electrical down-tilt is typically performed by transmitting a control signal from a remote location to the base station antenna. In response to this control signal, the base station antenna adjusts settings of phase shifters that are included in the antenna feed network to implement the phase shifts. Such electrically controlled down-tilting of the antenna is often referred to as “remote electronic tilt.” Electrical down-tilting of a phased array antenna typically adjusts the radiation pattern of the antenna downwardly in all directions, and hence, electrical down-tilting is typically preferred over mechanical down-tilting as it provides a more desirable adjustment to the radiation pattern of the antenna. Network performance may be improved if the tilt of the base station antennas are adjusted to optimize the coverage patterns of the antenna. For example, a phased array antenna may be electrically down-tilted to correct for movement of the antenna that has occurred over time or to reduce the coverage area of the antenna as new cellular base stations are installed to provide increased cell density.
Electromechanical phase shifters are typically used to electronically down-tilt the radiation pattern of a phased array antenna. These phase shifters are typically integrated within the antenna according to one of two conventional approaches, namely in monolithic and non-monolithic implementations. In the monolithic implementation, a “centralized” phase shifter and each of the radiating elements of an array are mounted on a single printed circuit board. Typically, the radiating elements are mounted on the front side of the printed circuit board, and the phase shifter is mounted in a central location on the back side of the printed circuit board. Transmission lines are provided on the printed circuit board that connect each output of the centralized phase shifter to a respective one of the radiating elements. In some cases, the number of radiating elements may exceed the number of outputs on the phase shifter. In such cases, power dividers may be provided along the transmission lines that further sub-divide the signals, and additional transmission lines are provided that extend from each output of the power dividers to the respective radiating elements so that each output of the centralized phase shifter is connected to one or more of the radiating elements via the transmission lines and power dividers.
In the non-monolithic implementations, the phase shifters are implemented separately from the radiating elements. Two different non-monolithic implementations are commonly used. In the first non-monolithic implementation, a centralized phase shifter is provided that has outputs that connect to a corporate feed network. The centralized phase shifter typically has an input, a relatively large number (e.g., five, seven or nine) outputs, and a corresponding number of paths that extend between the input and the respective outputs. The centralized phase shifter may apply a different phase adjustment to each of these paths. For example, a five output phase shifter might decrease the phase delay at first and second outputs thereof by 2X° and X°, increase the phase delay at fourth and fifth outputs thereof by X° and 2X° and not adjust the phase delay at the third output thereof. Each of the five outputs of this example phase shifter would then be connected to a respective one of the radiating elements or to a respective sub-group of radiating elements. The above-described centralized phase shifters thus employ a parallel or “one-to-many” design in which different phase shifts are applied to each of a plurality of parallel paths. A wiper arc phase shifter such as the phase shifter disclosed in U.S. Pat. No. 7,463,190, the contents of which is incorporated herein by reference, is one example of a phase shifter that may be used to implement the above-described centralized phase shifter in the first non-monolithic implementation.
The second non-monolithic approach employs a serial-output phase shifter. A typical serial-output phase shifter is implemented using a plurality of directional couplers or power dividers and phase shifters. The directional couplers and phase shifters are arranged in series in alternating fashion, with the output of each phase shifter coupled to the input of the downstream directional coupler in the series. A first output of each directional coupler is connected to the input of the next downstream phase shifter in the series, and the second output of each directional coupler is connected to a respective one of the radiating elements. The phase shift applied to the signal coupled to each radiating element is the sum of the individual phase shifts applied by each of the phase shifters that are upstream of a particular radiating element.
Pursuant to embodiments of the present invention, a phased array antenna is provided that includes a panel, a plurality of feed boards on the panel, each of the feed boards including at least one radiating element, a base-level adjustable phase shifter including a plurality of outputs, a first feed board adjustable phase shifter mounted on a first of the feed boards and a first cable that forms a transmission path between a first of the outputs of the base-level adjustable phase shifter and the first feed board.
In some embodiments, the phased array antenna may further include a second feed board adjustable phase shifter mounted on a second of the feed boards and a second cable that forms a transmission path between a second of the outputs of the base-level adjustable phase shifter and the second feed board. The first and second of the feed boards may include the same numbers of radiating elements and/or have the same design in some embodiments. The base-level adjustable phase shifter may be mounted on a third of the feed boards, and the third of the feed boards includes a third feed board adjustable phase shifter and a plurality of additional radiating elements in some embodiments.
In some embodiments, a first end of the first cable may be coupled to the first of the output of the base-level adjustable phase shifter via a first radio frequency (RF) junction and a second end of the first cable may be coupled to an input of the first feed board adjustable phase shifter via a second RF junction.
In some embodiments, the first and second RF junctions may comprise first and second solder joints, respectively.
In some embodiments, the first and second RF junctions may comprise first and second capacitive connections, respectively.
In some embodiments, the first of the feed boards may include a plurality of radiating elements, the first feed board adjustable phase shifter may have a plurality of outputs, and each output of the first feed board adjustable phase shifter may be coupled to a respective at least one of the radiating elements on the first of the feed boards.
In some embodiments, the first feed board adjustable phase shifter may have three outputs, and each output of the first feed board adjustable phase shifter may be coupled to a single respective one of the radiating elements.
In some embodiments, the first feed board adjustable phase shifter may have three outputs, and at least one of the outputs of the first feed board adjustable phase shifter may be coupled to at least two of the radiating elements.
In some embodiments, the first cable may be coupled to an input of the first feed board adjustable phase shifter, and respective printed circuit board transmission lines may connect each output of the first feed board adjustable phase shifter to a respective at least one of the radiating elements.
In some embodiments, the first feed board adjustable phase shifter may be a trombone-style phase shifter.
In some embodiments, the first of the feed boards may include at least one power divider that unequally divides the power of an RF signal that is input to the first of the feed boards from the first cable.
In some embodiments, the first feed board adjustable phase shifter may include a main feed board, a wiper board that is mounted above the main feed board, and/or a biasing element that is mounted on the main feed board, the biasing element configured to apply a force onto an upper surface of the wiper board in order to bias the wiper board toward the main feed board.
In some embodiments, the first feed board adjustable phase shifter may include a main feed board, a wiper board that is mounted above the main feed board, and a multi-piece support that includes a first portion that is mounted on a first side of the panel and a second portion that is mounted on a second side of the panel that is opposite the first side, the support extending through a slot in the panel. In such embodiments, the wiper board may be mounted on the multi-piece support.
Pursuant to further embodiments of the present invention, a phased array antenna is provided that includes a first feed board, a plurality of radiating elements, a first subset of the radiating elements mounted on the first feed board, a base-level adjustable phase shifter that has an input and a plurality of outputs, and a first feed board adjustable phase shifter mounted on the first feed board. The first feed board adjustable phase shifter has an input that is coupled to a first of the outputs of the base-level adjustable phase shifter, and a plurality of outputs. Each output of the first feed board adjustable phase shifter is connected to a respective one or more of the radiating elements in the first subset of the radiating elements.
In some embodiments, the phased array antenna further includes a second feed board adjustable phase shifter mounted on a second feed board, the second feed board adjustable phase shifter having an input that is coupled to a second of the outputs of the base-level adjustable phase shifter, and a plurality of outputs. Each output of the second feed board adjustable phase shifter may be connected to a respective one or more of the radiating elements included in a second subset of the radiating elements that are mounted on the second feed board.
In some embodiments, the phased array antenna may further include a first cable that is coupled between the first of the outputs of the base-level adjustable phase shifter and the first feed board adjustable phase shifter and a second cable that is coupled between the second of the outputs of the base-level adjustable phase shifter and the second feed board adjustable phase shifter.
In some embodiments, the base-level adjustable phase shifter may be mounted on the first feed board, and the phased array antenna may further include a first cable that is coupled between the second of the outputs of the base-level adjustable phase shifter and the second feed board adjustable phase shifter.
In some embodiments, at least one of the outputs of the first feed board adjustable phase shifter may be coupled to at least two of the radiating elements in the first subset of the radiating elements.
In some embodiments, the base-level adjustable phase shifter and the first feed board adjustable phase shifter may comprise two of a plurality of adjustable phase shifters included as part of the phased array antenna, and no more than two of the adjustable phase shifters are on the RF transmission path between an input to the phased array antenna and any of the radiating elements.
In some embodiments, all of the radiating elements that are coupled to the base-level adjustable phase shifter may be configured to operate in the same frequency band.
In some embodiments, the first feed board adjustable phase shifter may be a trombone-style phase shifter.
In some embodiments, the first feed board may include at least one power divider that unequally divides the power of an RF signal that is input to the first feed board.
In some embodiments, the first feed board adjustable phase shifter may include a main feed board, a wiper board that is mounted above the main feed board, and a biasing element that is mounted on the main feed board, and the biasing element may be configured to apply a force onto an upper surface of the wiper board in order to bias the wiper board toward the main feed board.
In some embodiments, the first feed board adjustable phase shifter may include a main feed board, a wiper board that is mounted above the main feed board, and a multi-piece support that includes a first portion that is mounted on a first side of the panel and a second portion that is mounted on a second side of the panel that is opposite the first side, the support extending through a slot in the panel. In such embodiments, the wiper board may be mounted on the multi-piece support.
Pursuant to additional embodiments of the present invention, methods of transmitting a signal through a phased array antenna that has a plurality of radiating elements are provided in which the signal is coupled to a first base-level adjustable phase shifter that has a plurality of outputs, where phases of respective sub-components of the signal that are passed to each respective output of the base-level adjustable phase shifter are different. A first of the outputs of the first base-level adjustable phase shifter is coupled to an input of a first upper-level adjustable phase shifter that is mounted on a first feed board, the first upper-level adjustable phase shifter including a first subset of the radiating elements mounted thereon. At least two of the outputs of the first upper-level adjustable phase shifter are each connected to one or more of the radiating elements in the first subset of radiating elements by respective transmission lines on the first feed board.
In some embodiments, the method may further comprise coupling a second of the outputs of the first base-level adjustable phase shifter to an input of a second upper-level adjustable phase shifter that is mounted on a second feed board, the second upper-level adjustable phase shifter including a second subset of the radiating elements, where at least two of the outputs of the second upper-level adjustable phase shifter are each connected to one or more of the radiating elements in the second subset of radiating elements by respective transmission lines on the second feed board.
In some embodiments, the first and second feed boards may be part of a plurality of feed boards, and each output of the first base-level adjustable phase shifter may be connected by a respective one of a plurality of coaxial cables to a respective one of the plurality of feed boards. In such embodiments, the plurality of coaxial cables may be the only coaxial cables interposed on the RF transmission paths between an input to the first base-level adjustable phase shifter and the radiating elements.
Pursuant to further embodiments of the present invention, a feed board assembly is provided that includes a main feed board having an upper surface and a lower surface, a plurality of radiating elements mounted on the main feed board to extend upwardly from the upper surface of the main feed board, a wiper board mounted above the upper surface of the main feed board, the wiper board comprising part of an adjustable phase shifter and a wiper support that has a wiper board support portion that supports the wiper board, the wiper support extending through an opening in the main feed board.
In some embodiments, the wiper support may include a post that is received within a slot of a remote electronic downtilt mechanical linkage.
In some embodiments, the wiper support may connect to a remote electronic downtilt mechanical linkage underneath the lower surface of the main feed board.
In some embodiments, the wiper support may be a multi-piece wiper support, and at least two of the pieces of the wiper support clip together.
Each of the above described conventional approaches for implementing remote electronic tilt has certain drawbacks. Antennas implemented using the monolithic approach tend to be quite large and costly, as a monolithic design requires that the phase shifter and all of the radiating elements in the array be implemented on a single printed circuit board. State-of-the-art phased array antennas may include ten, twelve, sixteen or more radiating elements for some frequency bands, which are spread out across the panel, most typically in a linear array. In a monolithic approach, all of these radiating elements are mounted on the same printed circuit board, which is why the monolithic approach requires a large, more costly unit. This approach also tends to increase the overall weight of the antenna. Moreover, in order to reduce cost, relatively low cost printed circuit boards are typically used in base station antennas. Unfortunately, the transmission lines on such low cost printed circuit boards tend to exhibit relatively high insertion losses as compared to transmission lines that are implemented using coaxial cable segments. Relatively long transmission line segments may be used to connect the radiating elements at the ends of the array to the centralized phase shifter. Accordingly, the insertion losses may be relatively high. Because of the above short-comings, the monolithic approach is typically impractical on state-of-the-art flat panel phased array antennas for wireless base stations.
The non-monolithic approaches may allow for the use of smaller, lighter and/or lower loss components. However, the serial-output approach is typically not used because it requires a large number of separate phase shifters which may require an inordinate amount of space on the antenna and/or may be prohibitively expensive. The non-monolithic approach where a centralized phase shifter is incorporated into a corporate feed network is typically used today, but this approach tends to require a large number of solder joints that are used to connect the coaxial cables between the centralized phase shifter and respective feed boards on which the radiating elements are mounted. This will be explained in further detail with reference to
For example,
As further shown in
Respective coaxial cables 140-1 through 140-7 connect the seven outputs 134 of the phase shifter 130 to the respective feed boards 120-1 through 120-7. Typically, a first end 142 of each coaxial cable 140 is soldered to a respective one of the outputs 134 of the phase shifter 130 and a second end 144 of each coaxial cable 140 is soldered to an input 122 of the respective feed boards 120. Thus, a total of fourteen solder joints must be performed to connect the seven outputs 134 of the phase shifter 130 to the inputs 122 of the respective seven feed boards 120.
Unfortunately, the above-described soldered cable connections increase the costs of manufacturing the phased array antenna 100, as the solder joints are typically formed manually. Moreover, the solder connections are a possible point of failure in the field (particularly as wind, temperature fluctuations, earthquakes and other environmental factors may impart stresses on the solder joints).
Additionally, solder joints are a potential 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. Inconsistent metal-to-metal contacts along the RF transmission path are one potential source for PIM distortion, particularly when such inconsistent contacts are in high current density regions of the transmission path. The non-linearities that arise 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, reducing the number of solder connections may reduce the opportunity for PIM to arise.
Pursuant to embodiments of the present invention, phased array antennas are provided that include multi-level phase shifters. In some embodiments, these phased array antennas may comprise a base-level adjustable phase shifter that has a relatively small number of outputs which connect to the feed boards of the phased array antenna. Some or all of the feed boards may have an increased number of radiating elements mounted thereon as compared to a corresponding conventional design. Each feed board may also include an adjustable phase shifter mounted thereon (which is often referred to herein as a “feed board adjustable phase shifter”). The outputs of each feed board adjustable phase shifter may be connected to the respective radiating elements on the feed board via printed circuit board transmission lines. Since multiple radiating elements are included on each feed board, and a single coaxial cable feeds all of the radiating elements on each respective feed board, the total number of coaxial cables, and hence the number of solder joints required, may be reduced as compared to the corresponding conventional phased array antennas of
For example, the conventional sixteen radiating element phased array antenna of
Aspects of the present invention will now be described in greater detail with reference to
As shown in
Three feed boards 320-1 through 320-3 are provided, each of which includes a respective subset of the radiating elements 301-316. Each feed board 320 comprises a monolithic element that includes a subset of the radiating elements 301-316, a feed board adjustable phase shifter 324 that has an input 326, a wiper arm 327 and outputs 328, and transmission lines 329 that connect the outputs 328 of the feed board adjustable phase shifter 324 to the radiating elements 301-316. In some embodiments, each feed board 320 may comprise a printed circuit board.
As shown in
Feed boards 320-2 and 320-3 may be similar to feed board 320-1. Feed board 320-2 includes radiating elements 310-7 through 310-10 and a feed board adjustable phase shifter 324-2 that has an input 326, a wiper arm 327 and two outputs 328. A first transmission line 329 connects a first of the outputs 328 of the feed board adjustable phase shifter 324-2 to radiating elements 310-7 and 310-8, and a second transmission line 329 connects a second output 328 of the feed board adjustable phase shifter 324-2 to radiating elements 310-9 and 310-10. Feed board 320-3 includes radiating elements 310-11 through 310-16 and a feed board adjustable phase shifter 324-3 that has an input 326, a wiper arm 327 and three outputs 328. A first transmission line 329 connects the first output 328 of feed board adjustable phase shifter 324-3 to radiating elements 310-11 and 310-12, a second transmission line 329 connects the second output 328 of feed board adjustable phase shifter 324-3 to radiating elements 310-13 and 310-14, and a third transmission line 329 connects the third output 328 of feed board adjustable phase shifter 324-3 to radiating elements 310-15 and 310-16.
The antenna 300 also includes a base-level adjustable phase shifter 330. The adjustable phase shifter 330 includes an input 332, a wiper arm 336 and three outputs 334. Coaxial cables 340-1 through 340-3 connect the respective outputs 334 of the adjustable phase shifter 330 to the respective feed boards 320-1 through 320-3. The coaxial cables 340 are soldered to the respective outputs 334 of the adjustable phase shifter 330 and to the respective feed boards 320. Thus, a total of six solder joints must be performed to connect the three outputs 334 of the adjustable phase shifter 330 to the inputs 322 of the respective feed boards 320-1 through 320-3.
The centralized adjustable phase shifter 330 is referred to herein as a “base-level adjustable phase shifter” because it is located at the base or “root” level of a multi-level tree structure of phase shifters. The feed board adjustable phase shifters 324 are referred to herein as “upper-level adjustable phase shifters” because they are at a second (or higher) level of the multi-level tree structure of phase shifters.
Thus, the phased array antenna 300 requires less than half the solder joints that are used in the antenna 100 that has the same number of radiating elements. As discussed above, this reduction in solder joints may reduce manufacturing and testing costs and may improve the reliability of the antenna 300 as compared to the antenna 100. While the phased array antenna 300 does use a plurality of microstrip transmission lines 329, which generally have higher insertion losses as compared to the coaxial cables 140 used in antenna 100, the microstrip transmission lines 329 are of relatively short length since they extend from a middle of a feed board 320 to the radiating elements 310 that are implemented on that feed board 320. Thus, while this may result in a small increase in insertion loss along the transmission path to each respective radiating element 310, the increase in insertion loss may be acceptable.
The base-level adjustable phase shifter 330 and the upper-level feed board adjustable phase shifters 324 each comprise adjustable phase shifters which may be adjusted in response to a control signal. The same is true with respect to the base-level adjustable phase shifters and upper-level feed board adjustable phase shifters described below with respect to further embodiments of the present invention.
Feed board 420-1 includes radiating elements 410-1 through 410-4 and a feed board adjustable phase shifter 424-1 that has an input 426, a wiper arm 427 and first and second outputs 428. A first transmission line 429 connects the first output 428 of the feed board adjustable phase shifter 424-1 to radiating elements 410-1 and 410-2. A second transmission line 429 connects the second output 428 of the feed board adjustable phase shifter 424-1 to radiating elements 410-3 and 410-4. The adjustable phase shifters 424 and the transmission lines 429 may be implemented in the same fashion as the adjustable phase shifters 324 and transmission lines 329 that are described above, and hence further description thereof will be omitted.
Feed board 420-2 includes radiating elements 410-5 through 410-8 and a feed board adjustable phase shifter 424-2 that has an input 426, a wiper arm 427 and first and second outputs 428. A first transmission line 429 connects the first output 428 of the feed board adjustable phase shifter 424-2 to radiating elements 410-5 and 410-6, and a second transmission line 429 connects the second output 428 of the feed board adjustable phase shifter 424-2 to radiating elements 410-7 and 410-8. Feed board 420-3 includes radiating elements 410-9 through 410-12 and a feed board adjustable phase shifter 424-3 that has an input 426, a wiper arm 427 and first and second outputs 428. A first transmission line 429 connects the first output 428 of feed board adjustable phase shifter 424-3 to radiating elements 410-9 and 410-10, and a second transmission line 429 connects the second output 428 of feed board adjustable phase shifter 424-3 to radiating elements 410-11 and 410-12. The antenna 400 also includes a base-level adjustable phase shifter 430 that has an input 432 and three outputs 434. Coaxial cables 440-1 through 440-3 connect the outputs 434 of phase shifter 430 to the respective feed boards 420-1 through 420-3. A total of six solder joints must be performed to connect the three outputs 434 of base-level adjustable phase shifter 430 to the respective feed boards 420-1 through 420-3. Thus, antenna 400 only requires 60% of the solder joints that are used in the conventional antenna 200 that has the same number of radiating elements.
Feed boards 320-2, 420-1, 420-2 and 420-3 may all be identical, as each of these feed boards includes four radiating elements and an adjustable phase shifter with two outputs. Feed boards 320-1 and 320-3 may also be identical to each other. Thus, antennas 300 and 400 may, in some cases, be implemented using a total of two feed board designs, which simplifies manufacturing and inventory control.
The phased array antennas 300 and 400 of
As shown in
Like the phased array antenna 300, the phased array antenna 500 includes three coaxial cables 540-1 through 540-3 that connect the three outputs 534 of the base-level adjustable phase shifter 530 to the respective feed boards 520-1 through 520-3. Thus, the antenna 500 likewise includes a total of six solder joints.
As shown in
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Phased array antennas often include multiple sets of radiating elements. For example, phased array antennas routinely include at least one set of radiating elements that transmits and receives signals in a first frequency band and a second set of radiating elements that transmits and receives signals in a second, different frequency band. The frequency band at the higher frequencies is typically referred to as the “high band” and the frequency band at the lower frequencies is typically referred to as the “low band.” In some embodiments, the phased array antennas 300, 400, 500 and 600 that are described above may be used to implement the high band array(s) on a phased array antenna.
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The phased array antennas according to embodiments of the present invention use multiple levels of phase shifters (i.e., a base-level adjustable phase shifter and at least one upper-level adjustable phase shifter) to reduce the number of solder connections as compared to conventional phased array antennas. This may be beneficial for one or more reasons. As discussed above, solder connections are a potential source of PIM distortion. PIM distortion can degrade an entire RF system, and hence elimination of any potential sources of PIM distortion may be very valuable. Additionally, solder connections are typically formed by hand and hence are labor intensive. Solder connections also comprise a potential point of failure in the RF path. Thus, the phased array antennas according to embodiments of the present invention may have reduced cost, improved performance and/or increased reliability.
Another consideration is the insertion loss associated with the different phased array antenna designs. Generally speaking, relatively inexpensive printed circuit boards are used to implement the feed boards based on cost considerations. As noted above, the transmission lines on these lower cost feed boards may exhibit higher insertion losses than coaxial cables, which is one of the reasons that fully monolithic feed boards may be impractical in certain cases.
The antennas according to embodiments of the present invention also add a second level of phase shifters, which is another potential source for an increase in insertion loss (as two phase shifters are provided along the respective transmission paths to each radiating element). However, the insertion loss of conventional phase shifters for phased array antennas generally increases with an increasing number of outputs on the phase shifter. Consequently, it is anticipated that the multi-tiered arrangement of phase shifters used in the phased array antennas according to embodiments of the present invention may exhibit about the same, or even lower, insertion losses than the corresponding insertion loss associated with the single level of phase shifters employed in conventional phased array antennas.
As discussed above, the phase shifters used in the phase array antennas according to embodiments of the present invention may be used to electronically adjust the elevation angle (“tilt”) of the radiation pattern of the antenna. Thus, the phase shifters used in the antennas according to embodiments of the present invention may be adjustable phase shifters that may be adjusted using a control signal. Any conventional phase shifters may be used in the antennas according to embodiments of the present invention such as, for example, the wiper arc phase shifters disclosed in U.S. Pat. No. 7,463,190 (“the '190 patent”). Other suitable adjustable phase shifters are disclosed, for example, in U.S. Pat. Nos. 8,674,787 and 8,674,788, the disclosure of each of which is incorporated herein by reference. The '190 patent discloses variable phase shifters that have an input and a plurality of outputs that include a stationary printed circuit board and a mechanically rotatable printed circuit board mounted thereon. The rotatable printed circuit board may include multiple capacitively-coupled sections of different radii which couple to arcs on the stationary printed circuit board and thus create different lengths, which changes the electrical path length for at least some of the paths, typically by different amounts. This change in path length adjusts the phase.
In the above-described embodiments, at least two levels of phase shifters are incorporated into the feed network that is used to feed the radiating elements of a linear array. Each of the radiating elements is designed to transmit and receive signals in a particular frequency band. A multi-level phase shifter approach is used to reduce the number of solder joints in the antenna. It should be noted that a multi-level phase shifter approach has been used for other purposes. In particular, U.S. patent application Ser. No. 14/812,339 (“the '339 application”) discloses a phased array antenna which uses a multi-level phase shift approach that includes course and fine phase shifters in order to reduce the number of diplexers that are required in a diplexed phased array antenna having antenna elements that transmit and receive signals on two different but relatively closely-spaced frequency bands. The '339 application does not disclose or suggest using a multi-level phase shifter approach to reduce the number of solder joints nor does it disclose the arrangements between the feed boards and phase shifters that allow the reduction in solder joints to be achieved.
It will also be appreciated that in many cases multiple arrays of radiating elements may be mounted on the same flat panel of a phased array antenna. For example, a very typical phased array antenna design includes two linear arrays of high band radiating elements and one linear array of low band radiating elements. It will be appreciated that in such phased array antennas one or more of these multiple arrays may use the multi-level phase shifter approaches disclosed herein. For example,
In the embodiments of the present invention that are described above, the base-level adjustable phase shifter was mounted separately from the feed boards. In other embodiments, the base-level adjustable phase shifter may be mounted on one of the feed boards along with one of the feed board adjustable phase shifters. Such a configuration is illustrated in
Pursuant to further embodiments of the present invention, methods of transmitting a signal through a phased array antenna that has a plurality of radiating elements are provided.
In some embodiments, the first and second feed boards may be part of a plurality of feed boards, and each output of the base-level adjustable phase shifter may be connected by a respective one of a plurality of coaxial cables to a respective one of the plurality of feed boards. In some embodiments, the plurality of coaxial cables may be the only coaxial cables interposed on the RF transmission paths between an input to the first base-level adjustable phase shifter and the radiating elements.
As discussed above, various embodiments of the present invention include both first and second levels of phase shifters. For example, in the embodiment of
In some embodiments of the present invention, a common mechanical linkage may be used to drive both a first level phase shifter and one or more second level phase shifters. In particular, the radii of the arcs included on the phase shifters and the gear ratios of the mechanical linkage may be selected so that the appropriate amount of linear travel will be applied to phase shifters at both levels. This is shown pictorially in
As shown in
The low-band feed board 2100 includes first and second power dividers 2110-1, 2110-2, first and second phase shifters 2120-1, 2120-2, first delay lines 2140-1, 2140-2, and second delay lines 2142-1, 2142-2. The low-band feed board 2100 includes the main feed board 2150 and a pair of wiper boards 2160-1, 2160-2, as will be discussed below.
As can be seen in
Each power divider 2110 includes an input 2112 and first and second outputs 2114, 2116. The input 2112-1 of power divider 2110-1 is coupled to input port 2158-1, and the input 2112-2 of power divider 2110-2 is coupled to input port 2158-2. Each power divider 2110 may be designed to evenly or unevenly split the power that is received at its respective input port 2112. The first output 2114-1 of power divider 2110-1 is connected to a first input 2122-1 of the first phase shifter 2120-1, and the second output 2116-1 of power divider 2110-1 is connected to a second input 2124-1 of the first phase shifter 2120-1.
Phase shifter 2120-1 includes the first and second inputs 2122-1, 2124-1, a first pair of concentrically arranged arcuate traces 2126-1 that includes an inner trace 2128-1 and an outer trace 2130-1, a second pair of concentrically arranged arcuate traces 2132-1 that includes an inner trace 2134-1 and an outer trace 2136-1, and a connecting trace 2138-1. The first input 2122-1 is located at a first end of the inner trace 2128-1 of the first pair of concentrically arranged arcuate traces 2126-1. The second input 2124-1 is located at one end of connecting trace 2138-1. The second end of connecting trace 2138-1 connects to the first end of inner trace 2134-1 of the second pair of concentrically arranged arcuate traces 2132-1. The first ends of the outer traces 2130-1, 2136-1 of the first and second pairs of concentrically arranged arcuate traces 2126-1, 2132-1 are connected to the respective delay lines 2140-1, 2140-2. The second ends of the inner traces 2128-1, 2134-1 and the second ends of the outer traces 2128-1, 2134-1 are open-circuited. The first and second pairs of concentrically arranged arcuate traces 2126-1, 2132-1 are formed on the main feed board 2150.
Referring now to
Operation of the phase shifter 2120-1 will now be discussed with reference to
The phase of each of the two sub-components of the RF signal that pass through phase shifter 2120-1 will be determined by the path length of the RF transmission lines on the main feed board 2150 and the wiper boards 2160-1 that connect each output 2114-1, 2116-1 of the power divider 2110-1 to a respective one of the radiating elements 2190-1, 2190-2. As can be seen in
The path lengths of the RF transmission lines through the phase shifter 2110-1 for the respective sub-components of the RF signal are a function of the rotary position of the wiper board 2160-1. In particular, the sub-component of the RF signal that is output through output 2114-1 of the power divider 2110-1 passes to inner trace 2128-1 of the first pair of concentrically arranged arcuate traces 2126-1. This sub-component of the RF signal then capacitively couples to the inner arm 2174-1 of the arcuate U-shaped trace 2172-1 on the wiper board 2160-1, where it travels around the connecting portion 2178-1 of the “U” and onto the outer arm 2176-1 of the arcuate U-shaped trace 2172-1. The sub-component of the RF signal capacitively couples from the outer arm 2176-1 of the arcuate U-shaped trace 2172-1 onto the outer trace 2130-1 of the first pair of concentrically arranged arcuate traces 2126-1 and, from there, onto the delay line 2140-1.
Referring now to
Referring now to
As is also shown in
While the low-band feed board 2100 of
As is readily apparent from the above-description, the low-band feed board 2100 may allow the phase to each of the low-band radiating elements 2190 to be individually adjusted, while only requiring one coaxial cable connection for each polarization to the low-band feed board 2100. This may simplify the manufacture of an antenna that uses low-band feed board 2100, remove possible sources of PIM distortion (namely the additional coaxial cable connections that would be required if each of the two radiating elements were connected to a base-level adjustable phase shifter) while improving the performance of the antenna by allowing independent control of the phase. A further advantage of the compact differential trombone-style phase shifter implementation as compared to a reactive tee wiper arc implementation is that the uneven power split allows for additional control of the amplitude taper and improved elevation pattern sidelobe levels.
The high-band feed board 2200 includes eight power dividers 2210-1 through 2210-8, first and second phase shifters 2220-1, 2220-2, and a plurality of delay lines 2240. The high-band feed board 2200 includes a main feed board 2250 and a pair of wiper boards 2260. The wiper boards 2260 are not shown in
Referring to
Power divider 2210-1 includes an input that is connected to the first input port 2258-1, a first output that is connected to the mounting location 2256-3 for the third radiating element via a delay line 2240, and a second output. As the first output of power divider 2210-1 is connected by conductive traces directly to the mounting location 2256-3 for the third radiating element, the phase delay of the sub-component of an RF signal input at input port 2258-1 that is provided to the third radiating element will be fixed (i.e., not adjustable). The second output of power divider 2210-1 is connected to an input of the second power divider 2210-2. The first output of power divider 2210-2 is connected to a first input of the first phase shifter 2220-1, and the second output of power divider 2210-2 is connected to a second input of the first phase shifter 2220-1.
Phase shifter 2220-1 has the same design as the phase shifter 2120-1 discussed above, and hence the design and operation of phase shifter 2220-1 will not be repeated here. Phase shifter 2220-1 includes the first and second pairs of concentrically arranged arcuate traces 2226-1, 2232-1. Phase shifter 2220-1 includes first and second outputs that are located at the ends of the outer traces of the respective first and second pairs of concentrically arranged arcuate traces 2226-1, 2232-1.
The first output of phase shifter 2220-1 is connected to the third power divider 2210-3 via a delay line 2240, and the second output of phase shifter 2220-1 is connected to the fourth power divider 2210-4 via a delay line 2240. The first output of the third power divider 2210-3 is connected to the mounting location 2256-1 for the first radiating element via a delay line 2240, and the second output of the third power divider 2210-3 is connected to the mounting location 2256-2 for the second radiating element via another delay line 2240. The first output of the fourth power divider 2210-4 is connected to the mounting location 2256-4 for the fourth radiating element via another delay line 2240, and the second output of the fourth power divider 2210-4 is connected to the mounting location 2256-5 for the fifth radiating element via yet another delay line 2240.
Thus, an RF signal that is input at input port 2258-1 is split (either equally or unequally) by the first power divider 2210-1 into two sub-components, and the first sub-component is fed to the third radiating element with a fixed phase shift. The second sub-component of the RF signal is split into third and fourth sub-components, which are phase shifted different amounts by the phase shifter 2220-1. The phase-shifted third sub-component of the RF signal is fed to the third power divider 2210-3 where it is split (either equally or unequally) into fifth and sixth sub-components which are fed to the respective first and second radiating elements. The phase-shifted fourth sub-component of the RF signal is fed to the fourth power divider 2210-4 where it is split (either equally or unequally) into seventh and eighth sub-components that are fed to the respective fourth and fifth radiating elements. Thus, the feed board 2200 may provide a fixed phase shift to the third radiating element, a first variable phase shift to the signals fed to the first and second radiating elements, and a second variable phase shift to the signals fed to the fourth and fifth radiating elements. Additionally, a first fixed phase shift may also be implemented in the delay lines 2240 between the signals fed to the first and second radiating elements and a second fixed phase shift may be implemented in the delay lines 2240 between the signals fed to the fourth and fifth radiating elements.
It will also be appreciated that each potential modification to the feed board 2100 that is discussed above could also be applied to the feed board 2200.
As shown in
The reflector 2330 includes a pair of slots 2332. The lower and upper pieces 2310, 2320 of each support 2300 are clipped together through a respective one of the slots 2332 so that the lower piece 2310 is on the underside of the reflector 2330 and the upper piece 2320 is on the front side of the reflector. As is further shown in
When the arm 2342 of the remote electronic downtilt mechanical linkage 2340 is, for example, pulled to the lower left in
It will be appreciated that numerous modifications may be made to the above disclosed example embodiments. For example, the number of radiating elements may be changed from what is shown in the example embodiments herein. Typically, the number of radiating elements for a phased array will be selected based on a number of factors including a desired coverage pattern, the frequency band, etc. It will be appreciated that the multi-level phase shifter approach disclosed herein may be used with arrays having any number of radiating elements. It will likewise be appreciated that the number of radiating elements per feed board and the number of radiating elements per phase shifter output may also be varied. As yet another example, while embodiments of the present invention are discussed in terms of flat panel antennas, it will be appreciated that they are equally applicable to antennas that have curved or other non-planar profiles. Thus, it will be appreciated that the embodiments disclosed herein are merely provided as examples to ensure that the concepts of the present invention are fully disclosed to those of skill in the art.
It will also be appreciated that the multi-level phase shifter concept may be used on planar arrays (e.g., arrays of radiating elements that have multiple columns as well as multiple rows of radiating elements). In fact, as the radiating elements in such planar arrays may be subdivided into groups that are closer together, the use of multi-level phase shifters may be particularly useful in such antenna designs as the transmission lines may be shorter in such planar arrays.
The use of multiple levels of phase shifters is non-intuitive, as it would seem to increase the size, weight, cost and complexity of the antenna with no apparent improvement in performance and with an apparent decrease in reliability due to the expanded number of parts that are potentially subject to failure. In particular, each added phase shifter comprises another device that takes up room, requires power connections, adds insertion losses and is subject to failure. However, the present inventors appreciated that the change in performance and/or weight may be relatively minor, as smaller phase shifters may be used in the multi-level phase shifter approach, and because these smaller phase shifters may have lower insertion losses than phase shifters having a larger number of outputs. Moreover, by significantly reducing the number of solder joints the manufacturing and testing of the antenna may be simplified, the reliability of the antenna may be improved, and the potential source for PIM distortion may be significantly reduced.
It will likewise be appreciated that more than two levels of phase shifters could be used in other embodiments.
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.
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.
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.).
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.
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, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
All embodiments can be combined in any way and/or combination.
The present application is a 35 U.S.C. § 371 national stage application of PCT Application No. PCT/US2017/036984, filed on Jun. 12, 2017, which itself claims priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application Ser. No. 62/351,317, filed Jun. 17, 2016, and to U.S. Provisional Patent Application Ser. No. 62/400,433, filed Sep. 27, 2016, the entire content of each of which is incorporated herein by reference. The above referenced PCT Application was published in the English language as International Publication No. WO 2017/218396 A1 on Dec. 21, 2017.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2017/036984 | 6/12/2017 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2017/218396 | 12/21/2017 | WO | A |
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| Number | Date | Country | |
|---|---|---|---|
| 20200321697 A1 | Oct 2020 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62400433 | Sep 2016 | US | |
| 62351317 | Jun 2016 | US |
