Patent Application
20220336964
The present invention generally relates to radio communications and, more particularly, to radiating elements for base station antennas used in cellular communications systems
Cellular communications systems are well known in the art. In a cellular communications system, a geographic area is divided into a series of regions that are referred to as “cells” which are served by respective base stations. The base station may include one or more base station antennas that are configured to provide two-way radio frequency (“RF”) communications with mobile subscribers that are within the cell served by the base station. The base station antennas are often mounted on a tower, with the radiation patterns (also referred to herein as “antenna beams”) that are generated by the base station antennas directed outwardly. Many cells are divided into “sectors.” In perhaps the most common configuration, a hexagonally-shaped cell is divided into three 120° sectors, and each sector is served by one or more base station antennas that generate antenna beams that have an azimuth Half Power Beamwidth (HPBW) of approximately 65°. Typically, a base station antenna includes multiple phase-controlled antenna arrays that each include a plurality radiating elements that are arranged in one or more vertical columns when the antenna is mounted for use. Herein, “vertical” refers to a direction that is perpendicular to the horizontal plane that is defined by the horizon. Each antenna array generates a respective antenna beam, or two antenna beams if the antenna array is formed with dual-polarized radiating elements. The phase controlled antenna arrays include columns of radiating elements (as opposed to a single radiating element) in order to narrow the vertical or “elevation” beamwidth of the antenna beam, which may both increase the gain of the array and reduce interference with adjacent cells.
In order to accommodate the ever-increasing volume of cellular communications, cellular operators have added cellular service in a variety of new frequency bands. Cellular operators have applied a variety of approaches to support service in these new frequency bands, including increasing the number of linear arrays (or planar arrays) of radiating elements per antenna. As more columns of radiating elements are added to a typical antenna, efforts have been made to decrease the sizes of the radiating elements in order to reduce interactions between adjacent columns of radiating elements. Additionally, as the number of radiating elements included in an antenna increases, the advantage of lowering the unit cost of the radiating elements increases.
Pursuant to embodiments of the present invention, radiating elements are provided that include a conductive patch having first and second slots that each extend along a first axis and third and fourth slots that each extend along a second axis that is perpendicular to the first axis, a feed network that includes first through fourth feed lines, each feed line crossing a respective one of the first through fourth slots, and a conductive ring that at least partially surrounds a periphery of the conductive patch and that encloses each of the first through fourth slots.
In some embodiments, the conductive ring may be a continuous ring that completely surrounds the conductive patch when the radiating element is viewed in plan view.
In some embodiments, the conductive ring may have a plurality of sections, and each section may enclose a respective one of the first through fourth slots.
In some embodiments, the feed network may further include a first input, a first power divider that is coupled to the first input, a second input, and a second power divider that is coupled to the second input, and the first and second feed lines may be coupled to respective first and second outputs of the first power divider, and the third and fourth feed lines may be coupled to respective first and second outputs of the second power divider.
In some embodiments, at least a portion of the conductive patch may be implemented on a first metal layer of a printed circuit board, where the first through fourth feed lines comprise metal traces on a second metal layer of the printed circuit board, and where each of the first through fourth slots extend to the periphery of the conductive patch.
In some embodiments, the second metal layer of the printed circuit board may further include a plurality of metal pads that are each electrically connected to the conductive patch via one or more plated through holes that extend between the first and second metal layers of the printed circuit board.
In some embodiments, the conductive patch may include a first portion that is implemented on a first metal layer of a printed circuit board and a second portion that is implemented on a different metal layer of the printed circuit board. In some embodiments, the different metal layer of the printed circuit board may be the second metal layer of the printed circuit board.
In some embodiments, the conductive ring may be electrically floating. In other embodiments, the conductive ring may be electrically connected to the conductive patch. In some embodiments, the conductive ring may be coplanar with at least a portion of the conductive patch.
Pursuant to further embodiments of the present invention, radiating elements for a base station antenna are provided that include a printed circuit board that includes a conductive patch having first and second slots that each extend along a first axis and third and fourth slots that each extend along a second axis that is perpendicular to the first axis, a first coaxial cable and a second coaxial cable that each extend from a reflector of the base station antenna to the printed circuit board, and a conductive stub that physically and electrically connects an outer conductor of the first coaxial cable to an outer conductor of the second coaxial cable.
In some embodiments, the printed circuit board may be mounted forwardly from the reflector at a distance that is greater than one-quarter of a wavelength corresponding to the center frequency of the operating frequency band of the radiating element.
In some embodiments, the conductive stub may be located at approximately one quarter of the wavelength corresponding to the center frequency of the operating frequency band of the radiating element from the printed circuit board. In some embodiments, the conductive stub may be located closer to the reflector than it is to the printed circuit board.
In some embodiments, the outer conductors of the first and second coaxial cables may be soldered to the printed circuit board.
In some embodiments, the radiating element may further include first and second conductive tubes that are positioned adjacent the first and second coaxial cables.
In some embodiments, the printed circuit board may further include a feed network that has a first input that is electrically connected to an inner conductor of the first coaxial cable, a first power divider that is coupled to the first input, first and second transmission lines that extend from the first power divider to cross the respective first and second slots, a second input that is electrically connected to an inner conductor of the second coaxial cable, a second power divider that is coupled to the second input, and third and fourth transmission lines that extend from the second power divider to cross the respective third and fourth slots.
In some embodiments, the conductive patch may be implemented at least partially on a first metal layer of the printed circuit board, where the feed network is implemented on a second metal layer of the printed circuit board, where the second metal layer further includes a plurality of metal pads that are each electrically connected to the conductive patch, and where each of the first through fourth slots extend to a periphery of the conductive patch.
Pursuant to still further embodiments of the present invention, radiating elements for a base station antenna are provided that include a printed circuit board that includes a conductive patch having first and second slots that each extend along a first axis and third and fourth slots that each extend along a second axis that is perpendicular to the first axis and a feed stalk that mounts the printed circuit board in front of a reflector of the base station antenna. A first metal layer of the printed circuit board includes a first portion of the conductive patch and a second metal layer of the printed circuit board includes a second portion of the conductive patch.
In some embodiments, the first portion of the conductive patch may be capacitively coupled to the second portion of the conductive patch. In other embodiments, the first portion of the conductive patch may be galvanically connected to the second portion of the conductive patch.
In some embodiments, the printed circuit board may further include a feed network that includes a first input, a first power divider that is coupled to the first input, and first and second transmission lines that extend from the first power divider to cross the respective first and second slots, and a second input, a second power divider that is coupled to the second input, and third and fourth transmission lines that extend from the second power divider to cross the respective third and fourth slots.
In some embodiments, the feed network may be implemented on the second metal layer of the printed circuit board.
In some embodiments, the first portion of the conductive patch may comprise a central portion of the conductive patch and the second portion of the conductive patch may comprise a first annular-shaped metal layer having an inner portion that overlaps the central portion of the conductive patch and an exterior portion that extends outwardly beyond the central portion of the conductive patch.
In some embodiments, the conductive patch may further include a third portion that comprises a second annular-shaped metal layer having an inner portion that overlaps the first annular-shaped metal layer of the second portion of the conductive patch and an exterior portion that extends outwardly beyond the first annular-shaped metal layer of the second portion of the conductive patch.
In some embodiments, the third portion of the conductive patch may be implemented in the first metal layer.
In some embodiments, each of the first through fourth slots may extend to a periphery of the conductive patch.
Pursuant to additional embodiments of the present invention, radiating elements for a base station antenna are provided that include a conductive patch having first through fourth slots that each extend along a first axis and fifth through eighth slots that each extend along a second axis that is perpendicular to the first axis, each of the first through fourth slots extending to a periphery of the conductive patch, the first through eighth slots dividing the conductive patch into four conductive arms and a first trace that extends from the first conductive arm to the second conductive arm to separate the first slot from the second slot.
In some embodiments, a second trace that extends from the second conductive arm to the third conductive arm to separate the fifth slot from the sixth slot, a third trace that extends from the third conductive arm to the fourth conductive arm to separate the third slot from the fourth slot, and a fourth trace that extends from the fourth conductive arm to the first conductive arm to separate the seventh slot from the eighth slot.
In some embodiments, the radiating element may further include a feed stalk that mounts a printed circuit board in front of a reflector of the base station antenna.
Pursuant to further embodiments of the present invention, methods of suppressing a common mode resonance in a base station antenna are provided. The base station antenna may include at least a reflector, an array of first radiating elements that are configured to operate in a first operating frequency band and an array of second radiating elements that are configured to operate in a second operating frequency band. Each second radiating element includes a radiator unit that is positioned forwardly of the reflector and at least one coaxial feed cable that connects to the radiator unit. Pursuant to these methods, an outer conductor of a first of the coaxial feed cables that feeds a first of the second radiating elements is electrically connected to the reflector at a grounding position that is selected so that the physical distance of the RF transmission path that extends between the grounding position and the radiator unit of the first of the second radiating elements is a distance that is not resonant at any frequency in the first operating frequency band
In some embodiments, the grounding position may be a position where an outer conductor of the first of the coaxial feed cables is galvanically connected to a rear surface of the reflector. For example, the first of the coaxial feed cables may be galvanically connected to a rear surface of the reflector by exposing a portion of the outer conductor and soldering the exposed portion of the outer conductor to the reflector. The first of the coaxial feed cables may extend between the radiator unit and a printed circuit board, and the printed circuit board may include a grounding tab where a ground conductor of the printed circuit board is coupled to the reflector.
In some embodiments, the physical distance of the RF transmission path that extends between the grounding position and the radiator unit of the first of the second radiating elements may be the sum of the length of the first of the coaxial feed cables and a distance between the location where the first of the coaxially feed cables connects to the printed circuit board and the grounding tab.
The physical distance of the RF transmission path that extends between the grounding position and the radiator unit of the first of the second radiating elements may, for example, not be a multiple of a quarter wavelength of any frequency in the first operating frequency band.
In some embodiments, a second of the coaxial feed cable may also feed the first of the second radiating elements, and a conductive stub may physically and electrically connect an outer conductor of the first of the coaxial feed cables to an outer conductor of the second of the coaxial feed cables. In such embodiments, the radiator unit of first of the second radiating elements may be mounted forwardly from the reflector at a distance that is greater than one-quarter of a wavelength corresponding to the center frequency of the second operating frequency band, and the conductive stub may be located at approximately one quarter of the wavelength corresponding to the center frequency of the second operating frequency band of the radiating element from the radiator unit. In some embodiments, the conductive stub may be located closer to the reflector than it is to the radiator unit.
Pursuant to embodiments of the present invention, small, low-cost dual-polarization radiating elements are provided that are suitable for use in base station antennas. In some embodiments, the radiating elements may be configured to operate in the 1427-2690 MHz frequency band or a portion thereof. For example, in some embodiments the radiating elements may be designed to operate in the 1695-2690 MHz frequency band. It will be appreciated, however, that the radiating elements according to embodiments of the present invention may be scaled to operate in other frequency bands. The radiating elements may exhibit high levels of port-to-port isolation, good cross-polarization discrimination, low insertion loss and suitable azimuth beamwidth performance across a wide operating frequency band.
In some embodiments, the radiating elements may include a radiator unit and a feed stalk. The feed stalk may be used to mount the radiator unit a suitable distance forwardly of a reflector of a base station antenna. The radiating element may optionally include a director and a director support. The radiator unit may comprise a conductive patch that has first and second slots that extend along a first axis and third and fourth slots that extend along a second axis that is perpendicular to the first axis. Each of the first through fourth slots may extend from a periphery of the conductive patch towards the middle or “central region” of the conductive patch, and the four slots may divide the conductive patch into four arms. Each arm may be a generally pie-shaped wedge in some embodiments, and the four arms may be electrically connected to each other in a central region of the conductive patch.
In some embodiments, the radiator unit may be implemented using a printed circuit board. In such embodiments, the printed circuit board may include a first metallization layer that includes at least a portion of a conductive patch and a second metallization layer that includes a feed network, where the two metal layers are separated by a dielectric layer. In some embodiments, the conductive patch may be implemented in its entirety on the first metallization layer of the printed circuit board, while in other embodiments, a second portion of the conductive patch may be implemented on a different metallization layer which may be the second metallization layer and/or a third metallization layer in various embodiments. In other embodiments, the conductive patch may be a sheet metal patch and any suitable feed network may be used to feed RF signals to the slots in the sheet metal patch. The conductive patch may have any appropriate shape including a circular shape, a square shape, an octagonal shape, etc. As shown in the drawings, the conductive patch may also be a variation and/or an approximation of such shapes.
The feed network may include first through fourth feed lines, where each feed line crosses a respective one of the first through fourth slots. The feed lines may be implemented as microstrip transmission lines or coplanar waveguide transmission lines in example, non-limiting embodiments. The feed network may also include a first input, a first power divider that is coupled to the first input, a second input, and a second power divider that is coupled to the second input. The first and second feed lines may be coupled to respective first and second outputs of the first power divider, and the third and fourth feed lines may be coupled to respective first and second outputs of the second power divider.
In some embodiments, the radiator unit may further include a conductive ring that at least partially surrounds the periphery of the conductive patch and encloses each of the first through fourth slots. In some embodiments, the conductive ring may be a continuous metal ring that completely surrounds the conductive patch, while in other embodiments, the conductive ring may comprise a plurality of sections, wherein each section encloses a respective one of the first through fourth slots. The conductive ring may be electrically connected to ground or may be electrically floating. The conductive ring may capacitively load the conductive patch, which may improve the cross-polarization discrimination performance of the radiating element, particularly at lower frequencies.
In some embodiments, the feed stalk may comprise a pair of coaxial feed cables that couple respective first and second RF ports of an antenna to the radiator unit. The feed stalk may further include a structural support such as, for example, a plastic support stalk. The structural support may be used to mount the radiator unit in front of the reflector and/or to maintain the coaxial feed cables in proper position for connecting to the radiator units. In order to increase the bandwidth of the radiating element, the feed stalk may mount the radiator unit more than a quarter wavelength in front of the reflector of the base station antenna in which the radiating element is used, where the wavelength refers to the wavelength corresponding to the center frequency of the operating frequency band of the radiating element. In some embodiments, the outer conductors of the two coaxial feed cables may be soldered or otherwise electrically connected together. For example, the two outer conductors may be soldered together at a distance of approximately one quarter wavelength from the radiator unit. This may improve the port-to-port isolation performance of the radiating element. A pair of metal rods may be provided on either side of the coaxial feed cables. The rods may provide a more symmetric structure behind the radiator unit, which may help improve the port-to-port isolation performance of the radiating element.
In still other embodiments, the conductive patch may be elongated in the vertical direction, which may narrow the elevation beamwidth and/or reduce the magnitude of the grating lobes in the antenna beam formed by the radiating element. In still other embodiments, the slots in the conductive patch may extend from a center of the conductive patch outwardly, and may be closed off at the periphery of the metal patch. In yet other embodiments, four meandered traces may be used to electrically connect adjacent arms of the conductive patch near the periphery of the conductive patch.
Pursuant to still further embodiments of the present invention, techniques are provided for suppressing common mode resonances that the coaxial feed cables used to feed RF signals to the above-described radiator units may generate in the responses of other nearby radiating elements that operate in different operating frequency bands. Pursuant to these techniques, the outer conductor of each coaxial feed cable may be electrically connected to a common ground reference such as the reflector of the base station antenna at a location where the length of the RF transmission path that extends between the grounding location and the radiator unit may not be a length that is resonant in the operating frequency band of other nearby radiating elements that operate in different frequency bands. The length of each RF transmission path may be the length of the coaxial feed cable plus the length of any additional path between the end of the coaxial feed cable and the grounding location. Ideally, the length of the RF transmission path that extends between the grounding location and the radiator unit may be kept as short as possible in order to reduce insertion losses, but is also selected so that the electrical length of the monopole formed by the coaxial feed cable (and other RF transmission path to the grounding location) is not resonate in the operating frequency band of the other nearby radiating elements.
Pursuant to still further embodiments of the present invention, radiating elements are provided that include a conductive patch having first and second slots that each extend along a first axis and third and fourth slots that each extend along a second axis that is perpendicular to the first axis. These radiating elements also include a feed network that includes first through fourth feed lines, each feed line crossing a respective one of the first through fourth slots. The first and second feed lines are forward of a first major surface of the conductive patch and the third and fourth feed lines are rearward of a second major surface of the conductive patch.
In some embodiment, the conductive patch may be formed of sheet metal. The radiating element may also include a metal stalk that includes first and second air microstrip transmission lines. A signal trace of the first air microstrip transmission line and the first and second feed lines may be formed as a first monolithic feed structure, and a signal trace of the second air microstrip transmission line and the third and fourth feed lines may be formed as a second monolithic feed structure. The first monolithic feed structure may extend through an opening in the conductive patch, while the second monolithic feed structure does not extend through any opening in the conductive patch. In some embodiments, outer edges of the conductive patch are bent (e.g., upwardly and/or downwardly) at an angle of at least 30° with respect to an inner portion of the conductive patch.
The radiating elements according to embodiments of the present invention may have a number of advantages. First, the radiating elements may have small physical footprints, and hence may exhibit improved column-to-column isolation. Second, the radiating elements may be inexpensive to manufacture, and may require fewer soldered connections than many conventional radiating elements. The reduced number of solder joints may simplify assembly while also reducing the number of potential sources for passive intermodulation distortion. Additionally, the radiating elements may have very large operating frequency bands while meeting all necessary performance metrics.
Embodiments of the present invention will now be discussed in greater detail with reference to the accompanying figures.
As shown in
As shown in
A plurality of dual-polarized low-band radiating elements 32 and a plurality of dual-polarized high-band radiating elements 42 are mounted to extend forwardly from the reflector 24. The low-band radiating elements 32 are mounted in a vertical column to form a linear array 30 of low-band radiating elements 32, and the high-band radiating elements 42 are mounted in two vertical columns to form two linear arrays 40-1, 40-2 of high-band radiating elements 42. The linear array 30 of low-band radiating elements 32 may be positioned between the two linear arrays 40-1, 40-2 of high-band radiating elements 42. Each linear array 30, 40-1, 40-2 may be used to form a pair of antenna beams, namely a first antenna beam having a +45° polarization and a second antenna beam having a −45° polarization. Note that herein when multiple like elements are provided, the elements may be identified by two-part reference numerals. The full reference numeral (e.g., linear array 40-2) may be used to refer to an individual element, while the first portion of the reference numeral (e.g., the linear arrays 40) may be used to refer to the elements collectively.
The low-band radiating elements 32 may be configured to transmit and receive signals in a first frequency band. In some embodiments, the first frequency band may comprise the 694-960 MHz frequency range or a portion thereof. The high-band radiating elements 42 may be configured to transmit and receive signals in a second frequency band. In some embodiments, the second frequency band may comprise the 1427-2690 MHz frequency range or a portion thereof. It will be appreciated that the number of linear arrays of radiating elements may be varied from what is shown in
As noted above, embodiments of the present invention provide low cost, high performance dual-polarized radiating elements that may be used, for example, to implement each of the high-band radiating elements 42 shown in
The feed stalk 110 may be used to mount the radiating element 100 to extend forwardly from the reflector 24 of base station antenna 10. The feed stalk 110 in the illustrated embodiment includes a support stalk 120 which may be made, for example, of plastic, and a pair of coaxial feed cables 130-1, 130-2. The radiator unit 140 may be mounted on the plastic support stalk 120 in some embodiments. The plastic support stalk 120 may include internal guide features 122 that are used to maintain the coaxial feed cables 130-1, 130-2 in their proper positions, as well as a mounting base 124 that is used to mount the plastic support stalk 120 in openings in the reflector 24 (
In order to increase the bandwidth of radiating element 100, the feed stalk 110 may be designed to mount the radiator unit 140 more than a quarter wavelength in front of the reflector 24 of base station antenna 100, where the wavelength refers to the wavelength corresponding to the center frequency of the operating frequency band of the radiating element 100.
While the support stalk 110 of
The director unit 190 may comprise a director support 192 and a director 194. The director 194 may comprise, for example, a flat piece of metal that is somewhat smaller than a conductive patch that is included in the radiator unit 140. The director support 192 is used to mount the director 194 at a suitable height above the radiator unit 140. The director 194 may help narrow the radiation pattern of the radiating element 100 in both the azimuth and elevation planes.
The radiator unit 140 included in radiating element 100 will now be described with reference to
As shown in
As shown in
The second metallization layer 146 of printed circuit board 142 may face forwardly, and may include a feed network 160 that is used to couple RF signals to and from the conductive patch 150. The feed network 160 may include first through fourth feed lines 166-1 through 166-4, where each feed line 166-1 through 166-4 crosses a respective one of the first through fourth slots 152-1 through 152-4. The feed lines 166 may be implemented as microstrip transmission lines in some embodiments. As shown in
The feed network 160 may further include first and second inputs 162-1, 162-2 and first and second power dividers 164-1, 164-2. The inputs 162 may each comprise a metal pad. A hole 163 may extend through a center of each metal pad 162 and through the dielectric layer 148 of the printed circuit board 142 so that center conductors of the respective coaxial feed cables 130-1, 130-2 may be inserted through the printed circuit board 142 and through the respective metal pads 162-1, 162-2. The center conductors of coaxial feed cables 130-1, 130-2 may be soldered (or otherwise electrically connected) to the respective metal pads 162-1, 162-2. The outer conductors of coaxial feed cables 130-1, 130-2 may be soldered (or otherwise electrically connected) to the conductive patch 150. Each input pad 162-1, 162-2 may act as a respective power divider 164-1, 164-2 that splits an RF signal that is input to the respective input pads 162. Feed lines 166-1 and 166-2 extend from the two outputs of the first power divider 164-1 and cross the respective first and second slots 152-1, 152-2, and feed lines 166-3 and 166-4 extend from the two outputs of the second power divider 164-2 and cross the respective third and fourth slots 152-3, 152-4. In the depicted embodiment, each feed line 166-1 through 166-4 terminates into a respective one of four quarter wavelength stubs 168-1 through 168-4. As a result, RF signals that are input on feed lines 166-1 through 166-4 feed the respective slots 152-1 through 152-4. In particular, when feed lines 166-1 and 166-2 are excited, slots 152-1 and 152-2 are fed, causing the conductive patch 150 to radiate RF energy having a −45° polarization. Likewise, when feed lines 166-3 and 166-4 are excited, slots 152-3 and 152-3 are fed, causing the conductive patch 150 to radiate RF energy having a +45° polarization.
As is further shown in
As shown in
The radiating element 200 may be identical to the radiating element 100 discussed above with one exception, which is that the outer conductors of coaxial feed cables 130-1, 130-2 are electrically connected together by a conductive stub 232 in radiating element 200. Note that various features of radiating element 200 are not shown in
The outer conductors of each coaxial feeder cable 130-1, 130-2 are nominally at ground potential. However, the coaxial feed cables 130-1, 130-2 may not connect to a common ground in the vicinity of radiating element 200 and, as a result, the two outer conductors may not actually be at a common potential. This difference in potential may result in unbalanced currents flowing on the coaxial feed cables 130-1, 130-2, which may degrade both the port-to-port isolation and the cross-polarization antenna pattern performance of the radiating element. As discussed above, the radiator unit 140 may be mounted more than a quarter wavelength in front of the reflector 24. This may result in unbalanced currents flowing in the coaxial feed cables 130-1, 130-2. In order to balance the currents, a conductive stub 232 is used to physically and electrically connect the outer conductors of the coaxial feed cables 130-1, 130-2. In some embodiments, the conductive stub 232 may comprise a solder joint. In other embodiments, the conductive stub 232 may comprise a conductive element that is soldered or otherwise connected to the outer conductors of the coaxial feed cables 130-1, 130-2. In some embodiments, the conductive stub 232 may be positioned about one quarter wavelength from the radiating unit 140.
As shown in
By elongating the radiator unit 440 in the vertical direction, the distance between adjacent elements in a column of radiating elements may be reduced. This may help reduce the magnitude of grating lobes, which refer to sidelobes in the elevation pattern (and in particular at high elevation angles) that are in undesired directions. The azimuth pattern for a radiating element that includes radiator unit 440 may generally be the same as the azimuth pattern for a radiating element that includes radiator unit 110, while the beamwidth of the main lobe in the elevation pattern for the radiating element that includes radiator unit 440 may be reduced. The improvements in elevation beamwidth and grating lobe reduction, however, have to be balanced against an expected degradation in port-to-port isolation.
A conductive ring 670 surrounds the outer portion 651-2 of the conductive patch 650. The conductive ring 670 is formed on the front metallization layer 646 of the printed circuit board 642 in the depicted embodiment, although it may be formed on rear metallization layer 644 in other embodiments. The feed network for radiator unit 640, which is not shown in
A conductive ring 770 surrounds the middle portion 751-2 of the conductive patch 750. The conductive ring 770 is formed on the front metallization layer 746 of the printed circuit board 742 in the depicted embodiment, although it may be formed on rear metallization layer 744 in other embodiments. The feed network for radiator unit 740, which is not shown in
It will be appreciated that the above-described radiating elements according to embodiments of the present invention may be combined in any way to provide many additional embodiments. For example, the conductive stub 232 of radiating element 200 and/or the conductive tubes 336 of radiating element 300 may be included in any of the other radiating elements described herein. Similarly, the conductive ring structures of
Similar to the radiator unit 140 discussed above with reference to
The outer conductors of the two feed cables 130-1, 130-2 (
Referring to
The radiator unit 940 of
There are several differences between the radiator unit disclosed in FIGS. 7-8 of U.S. Pat. No. 7,688,271 and the radiator unit 940 of
Pursuant to further embodiments of the present invention, techniques for grounding radiating elements are provided that may be used to suppress a common mode resonance that may distort the radiation pattern of nearby radiating elements that operate in a different frequency band. These techniques may be used, for example, with any of the radiating elements according to embodiments of the present invention that are disclosed herein. As described above, coaxial feed cables may be used as the feed elements for the radiating elements according to embodiments of the present invention. As is also described above, in some embodiments, the outer conductors of the coaxial feed cables 130 may not be coupled to the reflector 24 underneath the radiating elements, but instead may be coupled to the reflector 24 elsewhere within the antenna. As a result, the outer conductors of the coaxial feed cables 130 may appear as a monopole element that has a length equal to the distance from where the outer conductor of each coaxial feed cable 130 is grounded to the reflector 24 at the point where the coaxial feed cable 130 connects to one of the radiator units (e.g., radiator unit 140) according to embodiments of the present invention. If the monopole element formed by the outer conductor of a coaxial feed cable 130 has a length that is resonant within an operating frequency band of other radiating elements that may be included in the base station antenna, then the coaxial feed cables 130 may generate common mode resonances in the response of these other radiating elements, degrading the performance thereof.
Pursuant to embodiments of the present invention, the points where the outer conductors of the coaxial feed cables 130 for a radiating element are coupled to a common ground reference such as the reflector of an antenna may be selected so that common mode resonances will not be generated in the response of other radiating elements included in the antenna. In particular, the length of the “monopole” segment of each coaxial feed cable that extends from the radiator unit that the coaxial feed cable 130 feeds to the point where the coaxial feed cable 130 is connected to a common ground reference (e.g., the reflector 24) may be set to be a length that will not resonate in the operating frequency band of any other nearby radiating elements. Thus, for example, if the coaxial feed cables are used to feed so-called high band radiating elements that operate in the 1,695-2,690 MHz frequency band that are mounted adjacent other so-called low-band radiating elements that operate in the 696-960 MHz frequency band, then the lengths of the above-described “monopole” segments of the coaxial feed cables 130 will be selected so that they are not resonant in the 696-960 MHz frequency band (e.g., the lengths of the monopole segments will not be equal to a quarter wavelength, a half, wavelength, three quarters of a wavelength, one wavelength, etc. for any frequency within the 696-960 MHz frequency band). This technique may be used to suppress a common mode resonance that otherwise could degrade the performance of the low band radiating elements.
As shown in
As shown in
As is further shown in
As shown in
RF energy emitted by another radiating element 1070 that operates in a different frequency band may be present in the vicinity of the first segments 1032 of the coaxial feed cables 1030. As noted above, the first segments 1032 of the coaxial feed cables 1030 may appear as monopole elements that extend forwardly from the reflector 1000. Moreover, since each coaxial feed cable 1030 has a ground connection to the reflector 1000 at one of the grounding tabs 1059, the effective length of these monopole elements is not the length L1 of the first segments 1032 that extend forwardly from the reflector 1000, but instead is the sum of L1+L2+L3 for each coaxial feed cable 1030. If this effective length is a length that is resonant within the operating frequency band of the radiating element 1070, then the RF energy emitted by radiating element 1070 may induce currents on the coaxial feed cables 1030, generating the common mode resonance in the frequency response of the radiating element 1070. This common mode resonance will occur in a relatively tight range of frequencies for which the effective length of the monopole element is resonant within the operating frequency band of radiating element 1070. Unfortunately, this common mode resonance can degrade the performance of radiating element 1070.
An antenna designer may select the distance L2 based on the location of the power divider printed circuit board 1050 with respect to the radiating elements 1010, and may select the distance L3 based on the size of the power divider printed circuit board and the locations of the grounding tabs 1059 and the output ports 1054. As such, the antenna designer can select the effective length of the monopole element formed by each coaxial feed cable 1030. By selecting these effective lengths to not be lengths where the monopole elements will be resonant in the operating frequency band(s) of other nearby radiating elements, the generation of a common mode resonance in the response of the nearby radiating elements may be suppressed.
While
The radiating elements discussed above have primarily been implemented using radiator unit printed circuit boards having two metal layers, with a conductive patch of the radiating element implemented at least primarily on one metal layer and the feed network implemented primarily on the other layer of the printed circuit board. Embodiments of the present invention, however, are not limited thereto. For example,
Referring first to
As shown in
As shown in
While the feed stalk 1110 of
The first and second slots 1152-1, 1152-2 may extend along a first common plane and the third and fourth slots 1152-3, 1152-4 may extend along a second common plane that is perpendicular to the first common plane. Each of the slots 1152 may extend from a periphery of the conductive patch 1150 towards the middle or “central region” of the conductive patch 1150, and the four slots 1152 may divide the conductive patch 1150 into the four arms 1154-1 through 1154-4. The four arms 1154 are electrically connected to each other in a central region of the conductive patch 1150 and extend outwardly from the central region of the conductive patch 1150.
Openings in the form of slots 1158-1 through 1158-4 are formed in the respective upwardly bent outer edges 1156 of the square piece of sheet metal 1142. Thus, a slot 1158 is formed in each arm 1154. The slots 1158 may be generally T-shaped slots in some embodiments, as shown. Each slot 1158 may extend to a distal portion of a respective arm 1154. Four small printed circuit boards 1144 are provided. Each printed circuit board 1144 includes a dielectric substrate (not shown) that directly contacts a respective one of the upwardly bent outer edges 1156 of the square piece of sheet metal 1142, and a metal layer formed on the outer side of dielectric substrate. Each printed circuit board 1144 overlaps a respective one of the upwardly bent outer edges of the square piece of sheet metal 1142. The printed circuit boards 1144 may be attached to the upwardly bent outer edges 1156 of the square piece of sheet metal 1142 be any appropriate fashion including, for example, adhesives, double-sided tapes, rivets, screws or other fasteners. Each printed circuit board 1144 may cover a respective one of the slots 1158. In other embodiments, the printed circuit boards 1144 may be replaced with metal sheets that may be attached to the upwardly bent outer edges 1156 of the square piece of sheet metal 1142 via adhesive tape or other means that allow the metal sheets to capacitively couple to the upwardly bent outer edges 1156 of the square piece of sheet metal 1142. Each metal layer (whether in the form of a metal layer on a printed circuit board 1144 or a metal sheet) may capacitively couple with the outer edge 1156 of a respective one of the arms 1154.
As noted above, the traces 1132-1, 1132-2 are each part of a respective feed structure 1130-1, 1130-2. Each feed structure 1130-1, 1130-2 may comprise a monolithic piece of stamped and bent sheet metal. Feed structure 1130-1 includes first and second feed lines 1166-1, 1166-2, while feed structure 1130-2 includes third and fourth feed lines 1166-3, 1166-4. Thus, the first and second feed lines 1166-1, 1166-2 are physically and electrically connected to the first trace 1132-1, and the third and fourth feed lines 1166-3, 1166-4 are electrically connected to the second trace 1132-2.
Feed line 1166-1 crosses the first slot 1152-1 and feed line 1166-2 crosses the second slot 1152-2. Accordingly, RF signals that are incident on the first trace 1132-1 split so that a portion of the RF energy passes to each of the first and second feed lines 1166-1, 1166-2. Feed line 1166-3 crosses the third slot 1152-3 and feed line 1166-4 crosses the fourth slot 1152-4. Thus, RF signals that are incident on the second trace 1132-2 split so that a portion of the RF energy passes to each of the third and fourth feed lines 1166-3, 1166-4. The RF energy passes along each feed line 1166 to cross a respective one of the slots 1152. Each feed line 1166 terminates into a respective one of four quarter wavelength stubs 1168. As a result, RF signals that are input on feed lines 1166-1 through 1166-4 feed the respective slots 1152-1 through 1152-4, causing the conductive patch 1150 to radiate RF energy.
The first and second feed lines 1166-1, 1166-2 are positioned forwardly of the conductive patch 1150, as can best be seen in
It will be appreciated that many modifications may be made to the radiating element 1100 of
Notably, positioning the first and second feed lines 1166-1, 1166-2 on one side of the conductive patch 1150 while positioning the third and fourth feed lines 1166-3, 1166-4 on the other side of the conductive patch 1150 eliminates any need to provide special structures to prevent conductive lines 1166-1 and 1166-3 from electrically short-circuiting at the location where they “cross” when viewed from the front. However, it will be understood that all of the feed lines 1166 may be implemented on the same side (either front or back) of the conductive patch 1150 in other embodiments, as shown above with respect to other radiating elements according to embodiments of the present invention.
While monolithic sheet metal feed structures 1130-1, 1130-2 are used in the depicted embodiment, it will be appreciated that in other embodiments the first and second feed lines 1166-1, 1166-2 may be implemented using a first printed circuit board, and that the third and fourth feed lines 1166-3, 1166-4 may be implemented using a second printed circuit board. The traces 1132-1, 1132-2 may be electrically coupled to the respective printed circuit boards. If printed circuit boards are used, the feed branches may be implemented as coplanar waveguide or grounded coplanar waveguide transmission lines in the same manner discussed above with other embodiments of the present invention.
Bending the outer edges of the first piece of stamped metal 1142 may reduce the “footprint” of the radiating element 1100 (i.e., the area of the radiating element 1100 when viewed from the front). This may allow an array of radiating elements 1100 included in an antenna to be positioned closer to other arrays. As the radiating element 1100 may be formed primarily of stamped sheet metal it may be cheaper to fabricate than comparable radiating elements formed using printed circuit boards.
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, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, operations, elements, components, and/or groups thereof.
Aspects and elements of all of the embodiments disclosed above can be combined in any way and/or combination with aspects or elements of other embodiments to provide a plurality of additional embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202010061865.4 | Jan 2020 | CN | national |
| 202010168550.X | Mar 2020 | CN | national |
The present application claims priority under 35 U.S.C. 120 as a continuation of U.S. patent application Ser. No. 17/151,854, filed Jan. 19, 2021, which in turn claims priority to Chinese Patent Application 202010061865.4, filed Jan. 20, 2020, and to Chinese Patent Application 202010168550.X, filed Mar. 12, 2020, the entire content of each of the above are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 17151854 | Jan 2021 | US |
| Child | 17853975 | US |
