Patent Publication Number: US-11038286-B2

Title: Antenna array

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of U.S. provisional patent application Ser. No. 62/595,274, filed Dec. 6, 2017 and provisional patent application Ser. No. 62/647,989, filed Mar. 26, 2018, the entire contents of which are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present disclosure generally relates to antenna, and more particularly relates to antenna arrays. 
     BACKGROUND 
     Antenna arrays having multiple antennas therein are often used to transmit and receive data to and from multiple sources. Cellular tower antennas, for example, are often in communication with numerous cellular phones or other electronic devices. Electronic devices may be capable of utilizing multiple communication protocols such as 3G, 4G, 5G, or the like, to communicate with an antenna array. Often, a single antenna array is designed to be capable of handling the different communication protocols which may use different frequency bands. 
     BRIEF SUMMARY 
     In accordance with one embodiment, an antenna array is provided. The antenna array may include, but is not limited to, a first plurality of reflectors, each of the first plurality of reflectors having a face, a first edge and a second edge, wherein the first edge of each of the first plurality of reflectors is coupled to the second edge of another of the first plurality of reflectors, a first plurality of antenna elements arranged on the face of at least one of the first plurality of reflectors, the first plurality of antenna elements configured to radiate within a first frequency band, a second plurality of antenna elements arranged at a corner of at least two of the first plurality of reflectors, the corner comprising an area where the first edge of one of the first plurality of reflectors is coupled to the second edge of another one of the first plurality of reflectors, the second plurality of antenna elements configured to radiate within a second frequency band different than the first frequency band, a second plurality of reflectors, the second plurality of reflectors mounted to an end of the first plurality of reflectors, and a third plurality of antenna elements arranged on a face of at least one of the second plurality of reflectors, the third plurality of antenna elements configured to radiate within a third frequency band different than the first frequency band and the second frequency band. 
     In accordance with another embodiment, an antenna array is provided. The antenna array may include, but is not limited to a first plurality of reflectors arranged in a first shape, the shape comprising at least two faces and at least two edges, a first plurality of dipole antennas arranged on the at least two faces of the first plurality of reflectors, the first plurality of dipole antennas configured to radiate within a first frequency band, a second plurality of dipole antennas arranged at the at least two edges of the first plurality of reflectors, the second plurality of dipole antennas configured to radiate within a second frequency band different than the first frequency band, a second plurality of reflectors arranged in a second shape, the second shape comprising at least two faces and at least two edges, and a third plurality of dipole antennas arranged on a face of at least one of the second plurality of reflectors, the third plurality of dipole antennas configured to radiate within a third frequency band different than the first frequency band and the second frequency band. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
         FIG. 1  is a perspective view of an antenna array, in accordance with an embodiment; 
         FIG. 2  is a perspective view of an antenna array, in accordance with an embodiment; 
         FIG. 3  is a perspective view of another antenna array, in accordance with an embodiment; 
         FIG. 4  is a perspective view of another antenna array, in accordance with an embodiment; and 
         FIGS. 5 and 6  are polar plots illustrating the radiation patterns for antenna arrays, in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” Thus, any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described herein are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary, or detail of the following detailed description. 
     There are sometimes size restrictions relative to the size (e.g., height and width) of an antenna array depending upon where the antenna array is to be installed. When numerous communication protocols, and thus numerous frequency bands, have to be handled by a single antenna, it can be difficult to fit all of the required antenna elements within the single antenna array. An antenna array including an arrangement of antenna elements which are interleaved in an azimuth plane is discussed herein. As discussed in further detail below, the arrangement allows more antenna elements to be placed within a given area, which allows for omni-directional performance across multiple frequency bands within a smaller antenna array. 
       FIG. 1  is a perspective view of an antenna array  100 , in accordance with an embodiment. The antenna array  100  may be used, for example, as a cellular phone tower antenna, satellite communication antenna, a radar antenna, or the like. The antenna array  100  includes multiple antenna elements  105 . The antenna elements  105  may be, for example, dipole antennas, monopole antennas, patch antennas, folded dipole antennas, or the like, and any combination thereof. In the embodiment illustrated in  FIG. 1 , the antenna elements  105  are illustrated as dual-polarized dipole antennas, however, the number of antenna elements  105 , the configuration of the antenna elements  105 , and the type of antenna elements  105  can vary. The size of certain portions of the antenna element  105  control the frequency range that the antenna elements  105  operate over. For example, when the antenna element  105  is a dipole antenna, the length of the dipole arms control the frequency range over which the dipole antenna can operate. As seen in  FIG. 1 , the antenna array may include multiple different sized antenna elements  105  which allows the antenna array to operate over a different frequency ranges. By operating over multiple frequency ranges, the antenna array  100  can service different communication protocols (e.g., 3G, 4G, 5G, etc.) while also increasing the available bandwidth of the antenna array  100 . 
     The antenna array  100  further includes multiple reflectors  110  which form the internal structure of the antenna array  100 . The reflectors  110  may be formed from any conductive material. The reflectors  110  may be galvanically connected to one another, galvanically isolated from one another, or a combination thereof. In the embodiment illustrated in  FIG. 1 , the antenna array includes four reflectors  110  connected in a square or diamond pattern. However, the antenna array  100  may include two or more reflectors  110  arranged in any shape. For example, three reflectors  110  may be arranged in a triangle formation, five reflectors  110  may be arranged in a pentagonal formation, six reflectors  110  may be arranged in a hexagonal formation, and the like. While the above examples cite to regular shapes (i.e., triangles, squares, etc.), the reflectors  110  may be arrange in any regular or irregular shape. 
     The number of reflectors  110  may depend upon the number of frequency bands the antenna array  100  is intended to cover and the desired bandwidth of the antenna array  100 . In general, the more antenna elements  105  that can be arranged inside of an antenna array  100 , the more bandwidth the antenna array may cover. Furthermore, in order to achieve an omni-directional radiation pattern, antenna elements  105  generally should be arranged on multiple sides of the antenna array  100 . 
     As discussed above, size restrictions may be placed upon an antenna array  100  which may limit the height and width of the antenna array  100 . The size restrictions would generally limit the size of the reflectors  110 , and thus the number of antenna elements  105  that could be placed inside the antenna array  100 . Size restrictions can also be limiting with respect to the number of frequency bands the antenna array  100  can cover. These limitations can prevent an antenna array from having a functional omni-directional pattern across all of the frequency bands used therein. 
     In order to overcome limitations in size, to increase the number of antenna elements  105  within the antenna array  100 , and/or to increase the number of frequency bands available to the antenna array  100 , the antenna array  100  includes antenna elements  105  which are mounted on the face of the reflectors  110  and antenna elements  105  which are mounted on at the corners of the reflectors  110 . In the example illustrated in  FIG. 1 , the antenna array  100  includes four faces  115 ,  120 ,  125  and  130 , with each of the faces being a reflector  110 , and four corners  135 ,  140 ,  145  and  150  where the reflectors  110  meet. As discussed above, the reflectors  110  may be galvanically connected to one another, galvanically isolated from one another, or any combination thereof. While not illustrated in  FIG. 1 , the antenna array may include structure to hold the reflectors in place and either galvanically couple or isolate them as needed for the particular antenna array. 
     As seen in  FIG. 1 , antenna elements  155  and  160  are arranged on one of the faces of the antenna array  100  and antenna elements  165  are arranged on one of the corners of the antenna array  100 . By arranging antenna elements  105  on the faces  115 - 130  as well as the corners  135 - 150 , the antenna elements  105  are interleaved in both azimuth and elevation planes. In other words, the antenna elements  155  and  160  are mounted on the reflectors at a first angle relative to the angle of the reflectors (i.e., an angle of zero as they are mounted flat upon each reflector), and the antenna elements  165  are mounted on the reflectors at a second angle relative to the angle of the reflectors  110 . The angle that the antenna elements  165  are mounted may vary depending upon the number of reflectors  110 . In the embodiment illustrated in  FIG. 1 , the antenna elements  165  may be mounted at a forty-five-degree angle relative to either of the reflectors  110  the antenna element  165  is mounted to. 
     The antenna elements  165  which are arranged at the corners  135 - 150  of the reflectors  110  may have to be compensated for their position. Adjustments to the length of the radiating elements (e.g., dipole arms, etc.), the dimensions of a parasitic element if used, the width and/or length of a balun, and the like, may be made to compensate for the position of the antenna elements  165 . 
     The antenna elements  165  which are arranged on the corners  135 - 150  of the reflectors  110  may be mounted on a feed board  170 . The feed board  170  receives a radio frequency signal and splits the signal that will be sent to each antenna element  165 . The feed board  170  includes transmission lines which are distributed such that each antenna element  165  receives equal power and that the phase of the radio frequency signal is appropriate for the antenna element  165 . For example, when the antenna element  165  is a dual polarized dipole antenna, as illustrated in  FIG. 1 , the feed board  170  provides each dipole of the dual-polarized dipole antenna with the proper phase. Likewise, each feed board  170  may receive the radio signal from a splitter  175  providing equal power and phase to each feed board  170 . The feed boards  170  may be mounted to the reflectors via non-conductive standoffs  180 . The non-conductive standoffs  180  may be made from, for example, plastic, or any other non-conductive material. While only the antenna elements  165  are illustrated as being mounted on feed boards, any of the antenna elements  105  may be mounted on a feed board to aid in the distribution of the radio frequency signals. 
       FIG. 2  is a perspective view of an antenna array  200 , in accordance with an embodiment. The antenna array  200  includes reflectors  205 ,  210 ,  215 ,  220 ,  225  and  230  arranged in a hexagon formation. The antenna array  200  is intended to provide omni-directional coverage for all of the antenna elements therein. However, the antenna array architecture discussed herein could be used in directional antenna arrays as well. In order to provide omni-directional radiation pattern, identical antenna elements are formed on reflectors  205 ,  215  and  225 . Likewise, identical antenna elements are formed on reflectors  210 ,  220  and  230 . 
     The reflectors  205 ,  215  and  225  include dipole antennas  235  and  240 . In the embodiment illustrated in  FIG. 2 , each reflector  205 ,  215  and  225  includes two dual-polarized dipole antennas  235 . The dipole antennas  235  may operate over a frequency range of, for example, 698-960 MHz. As seen in  FIG. 2 , each dipole antenna  235  includes a parasitic element  245 . The parasitic element  245  may broaden the frequency range over which the dual-polarized dipole antenna  235  can operate. The dipole antennas  235  may be fed, for example, via electromagnetic coupling or the like. In the embodiment illustrated in  FIG. 2 , each reflector  205 ,  215  and  225  includes four dual-polarized dipole antennas  240 . The dipole antennas  240  are mounted on a feed board  250  which feeds the dual-polarized dipole antennas  240  as discussed above. The dual-polarized dipole antennas  240  may operate over, for example, a frequency range of 5150-5925 MHz. The antenna array  200  may further include a conductive fence  255  mounted at the top of the feed board  250 . The conductive fence  255  may be used, for example, to improve an elevation sidelobe for the dual-polarized dipole antennas  240 . The reflectors  205 ,  215  and  225  may further include one or more non-conductive posts  260 . The non-conductive posts  260  may support a radome (not illustrated) which covers the antenna array  200  and prevents the radome from hitting any of the antenna elements therein. 
     The reflectors  210 ,  220  and  230  may each include eight dual-polarized dipole antennas  265 . The dipole antennas  265  may operate over, for example, a frequency range of 3550-3700 MHz. The eight dual-polarized dipole antennas  265  may be mounted on two feed boards  270  which feed the dual-polarized dipole antennas  265 . 
     The antenna array  200  further includes dual-polarized dipole antennas  275  which are mounted at the edges of the reflectors  205 - 230 . In other words, the dual-polarized dipole antennas  275  are mounted at the boundary between two of the reflectors  205 - 230 . In the embodiment illustrated in  FIG. 2 , the dual-polarized dipole antennas  275  are mounted on all six edges of the reflectors  205 - 230 . By mounting the dual-polarized dipole antennas  275  at the edges of the reflectors  205 - 230 , the number of antenna elements within the antenna array  200  can be increased without having to increase the size of the antenna array. In other words, unlike other array designs which either increase a number of reflectors, and thus a width of the antenna array, or lengthen their reflectors to mount more antenna elements on the face of the reflectors, the antenna array  200  can include more antenna elements within a smaller package. The dual-polarized dipole antennas may operate over a frequency range of, for example, 1695-2400 MHz. The dual-polarized dipole antennas  275  may be mounted on feed boards  280  and fed signals in a similar way as discussed above. 
     While the antenna array  200  is described as covering four frequency bands (i.e., 698-960 MHz, 1695-2400 MHz, 3550-3700 MHz and 5150-5925 MHz), the number of frequency bands and their exact frequency ranges can vary depending upon the needs of the antenna array  200  by increasing, or decreasing, the number of antenna elements and by adjusting the operating frequency thereof. 
     In one embodiment, for example, the antenna array  200  may utilize twelve input/output (I/O) ports to cover the four bands. For example, two I/O ports may cover the 698-960 MHz band, four I/O ports may cover the 1695-2400 MHz band, four I/O ports may cover the 3550-3700 MHz band, and two I/O ports may cover the 5150-5925 MHz band. Each I/O port offers an omni-directional pattern which is obtained by combining three sectors (i.e., antenna elements on different reflectors or edges). Each sector of each band has four antenna elements in elevation plane except the 698-960 MHz band which has two elements. Each of the sets of dual-polarized dipoles are in group of four which are fed with a four-way splitter with proper phase and amplitude difference. To make omnidirectional pattern the three panels are combined with a three-way splitter with equal power and phase. As can be seen dipoles for 698-960 MHz, 1695-2400 MHz, and 3550-3700 MHz bands are in close proximity. The antenna array  200  illustrated in  FIG. 2 , for example, can be housed within a cylinder having a fourteen-inch diameter. As discussed above, the different dipole elements are interleaved in the azimuth and elevation planes. 
       FIG. 3  is a perspective view of another antenna array  300 , in accordance with an embodiment. Like the antenna arrays  100  and  200 , the antenna array  300  includes antenna elements mounted on the face of reflectors and antenna elements mounted at the edges of reflectors. 
     The antenna array is made with dual-polarized dipoles  310  operating in the 2 GHz range (1695-2690 MHz), dual-polarized dipoles  320  operating in the 3.5 GHz range (3550-3700 MHz), and dual-polarized dipoles  330  operating in the 5 GHz range (5150-5925 MHz). As seen in  FIG. 3 , the dual-polarized dipoles  310  are mounted on all six of the faces of the reflectors  340  and the dual-polarized dipoles  320  are mounted on all six of the edges of the reflectors  340  on feed boards  350 . In one embodiment, for example, the dual-polarized dipoles  320  may be mounted at an angle of sixty-degrees relative to the adjacent reflectors  340 . 
     In the embodiment illustrated in  FIG. 3 , the antenna array  300  includes ten ports covering the three bands. However, the number of ports and the number of antenna elements can vary. In this embodiment, the antenna array  300  includes four-ports covering the 1695-2690 MHz band, four-ports covering the 3550-3700 MHz band, and two-ports covering the 5150-5925 MHz band. Each antenna port offers an omni-directional pattern which is obtained by combining three sectors (e.g., three reflectors, three edges, etc.). Each sector of each band has four antenna elements in elevation plane. In other words, two dual-polarized antennas, each having two dipoles, on three opposing reflectors comprise each sector. The opposing reflectors may be each separated by, for example, one-hundred twenty degrees. The two dual-polarized antennas are fed with a four-way splitter with proper phase and amplitude difference. To make omnidirectional pattern the three panels are combined with a 3-way splitter with equal power and phase. As can be seen dipoles for 1695-2690 MHz, and 3550-3700 MHz bands are in close proximity. The antenna array  300  illustrated in  FIG. 3 , for example, can be housed within a cylinder having a less than ten-inch diameter. As discussed above, the different dipole elements are interleaved in the azimuth and elevation planes. 
     One benefit of the embodiment illustrated in  FIG. 3  is that by mounting the dual-polarized dipoles  320  on the edges of the reflectors  305 , where the dual-polarized dipoles  310  are mounted, reduces the size of the antenna array  300  relative to antenna arrays which only mount antenna elements on the face of the reflectors. This leaves enough room within a size constrained antenna array (e.g., no more than two feet tall), to have the dual-polarized dipoles  330  isolated from the other antenna elements on the reflectors, which improves the radiation pattern of the dual-polarized dipoles  330 . 
       FIG. 4  is a perspective view of another antenna array  400 , in accordance with an embodiment. The antenna array  400  is similar to the antenna array  300  illustrated in  FIG. 3 , but utilizes two different sized reflectors, as discussed below. The antenna array  400  includes six reflectors  410  arranged in a hexagonal formation. Antenna elements  420  are mounted on the face of each of the reflectors. In this embodiment, the antenna elements  420  are dual-polarized dipole antennas. The antenna array further includes antenna elements  430  mounted at the edges of the reflectors  410 . Like the embodiments discussed above, the antenna elements  430  may be mounted on feed boards  440  which may be connected to the reflector edges using non-conductive standoffs. 
     Each of the reflectors  410  may have a width based upon the size of the antenna elements mounted thereon, namely, the antenna elements  420 . In other words, the size of the reflectors  410  is based upon the frequency range of the antenna elements  420  thereon. In one embodiment, for example, the antenna array  400  may need better than twenty decibels coupling between adjacent elements. In this exemplary embodiment, in order to have better than twenty decibels coupling between adjacent elements, the width of the reflectors may around 0.6-0.8λ, or in this example, around eighty millimeters. 
     The antenna array  400  further includes reflectors  450 . As seen in  FIG. 4 , the antenna array  400  includes three reflectors  450  arranged in a triangular configuration. The reflectors  450  are mounted on top of the reflectors  410  via a mounting plate  460 . The antenna array  400  further includes antenna elements  470  mounted on the face of the reflectors  450 . The size of the reflectors  450  is based upon the operating frequency range of the antenna elements  470 . In other words, if the antennal elements  470  operate in the 5 GHz range, the reflectors  450  would be sized in width to properly reflect frequencies in that range. In one embodiment, for example, the antenna array  400  may need better than twenty decibels coupling between adjacent elements. In this exemplary embodiment, in order to have better than twenty decibels coupling between adjacent elements, the width of the reflectors  450  may around 0.6-0.8λ, or in this example, around fifty millimeters. 
     As discussed above, because the antenna elements  430  are mounted at the corners of the reflectors  410 , the overall size of the antenna array  400  is reduced as the antenna elements  430  would otherwise need to be mounted on separate reflectors adjacent to the antenna elements  420  (i.e., the antenna array would be wider as there would be more reflectors), or placed on the reflectors above or below the antenna elements  420  (i.e., the antenna array would be taller as the reflectors  410  would need to be longer to fit the antenna elements  430  on the faces thereof). Accordingly, by arranging the antenna elements  430  at the corner of the reflectors, there is space within a predefined requirement (e.g., a limit of two feet tall), to fit the antenna elements  470  on the separate reflectors  450 . By having reflectors of two sizes, the omni-directional pattern for the antenna elements  470  is improved.  FIGS. 5 and 6  are polar plots illustrating the radiation patterns for antenna arrays  300  and  400 , respectively. In particular,  FIGS. 5 and 6  show antenna azimuth patterns for the +/−forty-five degree polarized dual band antennas illustrated in  FIGS. 3 and 4 , respectively, at different frequencies over a 5150-5925 MHz range. As seen in  FIGS. 5 and 6 , by including the reflectors  450  which are sized for the antenna elements  470 , the nulls for the antenna array  400  illustrated in  FIG. 6  are much smaller than the nulls for the antenna array  300  illustrated in  FIG. 5 . In other words, the antenna array  400  has a better omni-directional pattern across all of the frequency bands. 
     Returning to  FIG. 4 , while the reflectors  410  are arranged in a hexagon pattern (i.e., six reflectors) and the reflectors  450  are arranged in a triangular pattern (i.e., three reflectors), the number of reflectors in each sector can vary depending upon the needs of the antenna array. In other words, the number of sectors (i.e., the number of differently sized reflector sections), and the number of reflectors in each sector can vary depending upon the desired number of frequency bands in the antenna array, the desired bandwidth of the antenna array, and any size constraints for the antenna array. Furthermore, any of the reflector sectors may have antenna elements arranged at the junction of multiple reflectors (i.e., arranged at the corners), as discussed above. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.