Patent Publication Number: US-11641055-B2

Title: Base station antennas having staggered linear arrays with improved phase center alignment between adjacent arrays

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Chinese Patent Application No. 202010901489.5, filed Sep. 1, 2020, the entire content of which is incorporated herein by reference as if set forth fully herein. 
     FIELD 
     The present invention relates to a communication system, and more particularly, to a base station antenna for a cellular communication system. 
     BACKGROUND 
     Base station antennas used in wireless communication systems are used to transmit radio frequency (“RF”) signals to and receive RF signals from fixed and mobile users of cellular communication services. Base station antennas generally comprise a linear array or a two-dimensional array of radiating elements, such as crossed dipoles or patch radiating elements. In order to increase the system capacity, beamforming base station antennas are being deployed at present, which comprise a plurality of closely spaced linear arrays of radiating elements (simply referred to as “arrays” or “columns” herein). A typical goal of an antenna with such beamforming capabilities is to generate a narrow antenna beam in the azimuth plane. The RF signals emitted by the radiating elements of the different columns combine to create this antenna beam. This increases the signal power transmitted in the desired user direction and reduces interference. 
     If the arrays of radiating elements in the beamforming antenna are closely spaced, the antenna beam can be scanned to a very wide angle in the azimuth plane (e.g., 60°) without generating large magnitude sidelobes. However, as the arrays are spaced more closely together, the mutual coupling between the radiating elements in adjacent arrays increases, which reduces other performance parameters of the base station antenna, such as co-polarization performance. In order to maintain close spacing between adjacent arrays of beamforming antennas and increase isolation between radiating elements in adjacent arrays, it may be necessary to stagger adjacent arrays in the longitudinal direction of the base station antenna, which increases the physical spacing between “adjacent” radiating elements in “adjacent” arrays. This staggered structure reduces the mutual coupling between adjacent elements, thus increasing the isolation. 
     As shown in  FIG.  1   , a base station antenna comprises radiating elements  1  operating in a lower frequency band and radiating elements  2  operating in a higher frequency band. The radiating elements  1  are respectively arranged in arrays (also called columns)  11  and  12  along the longitudinal direction of the base station antenna, and the radiating elements  2  are respectively arranged in arrays (also called columns)  21  to  24  along the longitudinal direction of the base station antenna. The arrays  11  and  12  are not staggered in the longitudinal direction. For example, as shown by the dotted line A, the physical centers of the two radiating elements in the two arrays are basically transversely aligned. When feeding arrays  11  and  12 , the radiating elements  1  in the arrays  11  and  12  can be divided into a plurality of sub-arrays (also called “subsets”). In this specification, each sub-array comprises one or a plurality of adjacent (i.e., continuously positioned) radiating elements. The sub-arrays may include one or a plurality of radiating elements and are represented in the figures by a solid square frame that surrounds the radiating element(s). Each of the arrays  11  and  12  is fed by a phase shifter, and each sub-array is coupled to a corresponding output of the phase shifter (see the description of  FIG.  2    for details). Generally, a sub-array comprises two or three radiating elements that are mounted on a feed board and coupled to an output of the phase shifter. It should be understood that one sub-array may comprise other numbers of radiating elements. In the example shown in  FIG.  1   , because the arrays  11  and  12  are not staggered in the longitudinal direction, the phase centers of the corresponding sub-arrays are basically aligned. For example, as shown by dashed lines F and I, the phase center D of sub-array  111  of array  11  is basically aligned with the phase center E of sub-array  121  of array  12 , and the phase center G of sub-array  112  is basically aligned with the phase center H of sub-array  122 . 
     When the phase centers of a first element X and a second element Y are basically aligned, the phase of electromagnetic radiation of element X is basically consistent with that of element Y at any point on the elevation plane (i.e., at any elevation angle). The elements X and Y may each be a single radiating element, a combination of radiating elements, a sub-array, a combination of sub-arrays, an array, etc. 
     Two adjacent arrays in the arrays  21  to  24  are staggered in the longitudinal direction. For example, the longitudinal position of each radiating element  2  in array  21  is staggered with respect to that of the corresponding radiating element  2  in array  22 , as shown by the dotted lines B and C in  FIG.  1   , and the amount of stagger s is equal to half of the longitudinal distance d between two adjacent radiating elements in the same array, that is, s=0.5 d. If the arrays  21  to  24  adopt a feeding mode similar to that of the arrays  11  and  12 , as shown in  FIG.  2   , the phase centers of adjacent arrays will also shift accordingly. Each of the arrays  21  to  24  is fed by a phase shifter (for each polarization), and each sub-array is coupled to a corresponding output of the phase shifter. For simplicity, only the feeding configuration of the array  24  is shown in  FIG.  2   , and the feeding configurations of the arrays  21  to  23  are similar. The phase shifter  3  feeds the array  24 . The array  24  comprises sub-arrays  241  to  245 , each of which comprises two or three radiating elements. Each of the sub-arrays  241  to  245  is coupled to a corresponding output ( 31  to  35 ) of the phase shifter  3 . Each of the arrays  21 ,  22 ,  23  are likewise coupled to a respective phase shifter (not shown), with each sub-array of the respective arrays coupled to a corresponding output of the respective phase shifter. The phase center of a sub-array (e.g., sub-array  241 ) that contains three radiating elements is approximately at the center of the middle radiating element, and the phase center of a sub-array containing 2 radiating elements is approximately halfway between the two radiating elements. If the arrays  21  to  24  are fed as shown in  FIG.  2   , the phase centers of the two corresponding sub-arrays in two adjacent arrays will be misaligned. For example, the phase center of each of the sub-arrays  211  to  214  in array  21  is longitudinally staggered from the phase center of the corresponding sub-array in array  22 , and the stagger amount (also called staggered distance) is s. Since the number of radiating elements in array  22  or  24  is one less than that in array  21  or  23 , the phase centers of the sub-arrays located at the lowest end of each array are aligned with each other, for example, the sub-array  215  and the corresponding sub-array in the array  22 . 
     The above-mentioned feeding configuration of arrays  21  to  24  not only results in a stagger of the phase centers of corresponding sub-arrays between adjacent arrays, but also staggers the phase centers of adjacent arrays. For example, the phase center of array  21  is offset upward from the phase center of array  22 . This phase center offset between adjacent arrays causes spatial phase difference between arrays, which will distort the radiation pattern of antenna beams formed by these arrays. 
     In addition, it is also desirable to electrically adjust the elevation angle of the antenna beams generated by the beamforming antenna so as to adjust the coverage area of the antenna in the elevation plane. This can be done separately for each array using the electromechanical phase shifters. However, the disadvantage is that, with the increase of the applied electrical tilt angle, the distortion to the antenna beam caused by the offset of the phase centers of adjacent arrays may increase. To compensate for this distortion, different amplitudes and/or phase weights can be adopted for different radiating element arrays. However, including this compensation system will increase the design difficulty and/or cost of the antenna system. 
     SUMMARY 
     According to the first aspect of the present invention, a base station antenna is provided, comprising: a first array that includes a plurality of first radiating elements arranged along the longitudinal direction of the base station antenna; and a second array that includes a plurality of second radiating elements arranged along the longitudinal direction of the base station antenna, the second array transversely adjacent the first array, wherein the longitudinal position of each second radiating element is staggered from that of the corresponding first radiating element, wherein, the first array comprises first and second sub-arrays, each of which comprises one or a plurality of adjacent first radiating elements, and wherein a phase center of the combination of the first and second subarrays is basically aligned with a sub-phase center of the second array. 
     According to a second aspect of the present invention, a base station antenna is provided, comprising: a first column of radiating elements, wherein the first column has a first sub-phase center; and a second column of radiating elements transversely adjacent to the first column, the longitudinal positions of the first column and the second column being staggered by a first staggered amount, wherein the second column has a second sub-phase center, the longitudinal positions of the first sub-phase center and the second sub-phase center are basically aligned, the first column comprises first and second subsets of radiating elements, and a phase center of the combination of the first and second subsets basically coincides with the first sub-phase center. 
     According to a third aspect of the present invention, a base station antenna is provided, comprising: a first column of radiating elements, wherein the first column comprises a first phase center; and a second column of radiating elements adjacent to the first column, wherein the second column comprises a second phase center, the first and second columns are staggered in the longitudinal direction of the base station antenna, the first and second phase centers are basically aligned, the first column comprises first and second subsets, and any one of the first and second subsets comprises one or a plurality of adjacent radiating elements, and the phase center of the combination of the first and second subsets basically coincides with the first phase center. 
     According to a fourth aspect of the present invention, a base station antenna is provided, comprising: a first array that includes a plurality of first radiating elements arranged along a longitudinal direction of the base station antenna; a second array that includes a plurality of second radiating elements arranged along the longitudinal direction of the base station antenna, the second array transversely adjacent the first array, wherein the longitudinal positions of the second radiating elements are staggered from the longitudinal positions of the first radiating elements, wherein a phase center of a first sub-array of the first array is a first distance above a phase center of the first array, wherein a phase center of a second sub-array of the first array is the first distance below the phase center of the first array, wherein a phase center of a first sub-array of the second array is a second distance above a phase center of the second array, wherein a phase center of a second sub-array of the second array is the second distance below the phase center of the second array, wherein the phase center of the first array and the phase center of the second array are aligned along a transverse direction, and wherein the first distance is different from the second distance. 
     According to a fifth aspect of the present invention, a base station antenna is provided, comprising: a first array that includes a plurality of first radiating elements arranged along a longitudinal direction of the base station antenna; and a second array that includes a plurality of second radiating elements arranged along the longitudinal direction of the base station antenna and transversely adjacent to the first array, wherein the longitudinal positions of the second radiating elements are staggered from that of the longitudinal positions of the first radiating elements, wherein a phase center of a combination of a first sub-array and a second sub-array of the first array is aligned along a transverse axis with a phase center of a combination of a first sub-array and a second sub-array of the second array. 
     Other features and advantages of the present invention will be made clear by the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG.  1    is a schematic front view of a radiating element array in a conventional base station antenna and a schematic diagram of a feeding configuration of some arrays. 
         FIG.  2    is a schematic front view showing the feeding configuration of other arrays in  FIG.  1   . 
         FIG.  3 A  is a schematic front view of the feeding configurations for some of the arrays in a base station antenna according to an embodiment of the present invention. 
         FIG.  3 B  is a schematic diagram of some of the sub-arrays in  FIG.  3 A . 
         FIGS.  4 A to  4 C  are schematic front views of the feeding configurations for some arrays in base station antennas according to further embodiments of the present invention. 
         FIGS.  5 A to  5 E  are schematic front views of the feeding configurations for some arrays in base station antennas according to still further embodiments of the present invention. 
     
    
    
     Note, in the embodiments described below, the same signs may be used in different drawings to denote the same parts or parts with the same functions, and repeated descriptions thereof are omitted. In some cases, similar labels and letters are used to indicate similar items. 
     For ease of understanding, the position, size, and range of each structure shown in the drawings and the like may not indicate the actual position, size, and range. Therefore, the present invention is not limited to the position, size, range, etc. disclosed in the drawings. 
     DETAILED DESCRIPTION 
     The present invention will be described below with reference to the accompanying drawings, which show several embodiments of the present invention. However, it should be understood that the present invention can be presented in many different ways and is not limited to the embodiments described below. In fact, the embodiments described below are intended to make the present invention more complete and to fully explain the protection scope of the present invention to those skilled in the art. It should also be understood that the embodiments disclosed herein may be combined in various ways so as to provide additional embodiments. 
     It should be understood that the terms used herein are only used to describe specific embodiments, and are not intended to limit the scope of the present invention. All terms used herein (including technical terms and scientific terms) have meanings normally understood by those skilled in the art unless otherwise defined. Well-known functions or structures may not be described in detail. 
     As used herein, when an element is said to be “on” another element, “attached” to another element, “connected” to another element, “coupled” to another element, or “in contact with” another element, etc., the element may be directly on another element, attached to another element, connected to another element, coupled to another element, or in contact with another element, or an intermediate element may be present. In contrast, when an element is said to be “on” another element, “attached” to another element, “connected” to another element, “coupled” to another element, or “in contact with” another element, etc., no intermediate element may be present. As used herein, when one feature is arranged “adjacent” to another feature, it may mean that one feature has a part overlapping with the adjacent feature or a part located above or below the adjacent feature. 
     As used herein, spatial relationship terms such as “upper”, “lower”, “left”, “right”, “front”, “back”, “high” and “low” can explain the relationship between one feature and another in the drawings. It should be understood that, in addition to the orientations shown in the attached drawings, the terms expressing spatial relations also comprise different orientations of a device in use or operation. For example, when a device in the attached drawings is turned upside down, the features originally described as being “below” other features now can be described as being “above” the other features. The device may also be oriented in other directions (rotated by 90 degrees or in other orientations), and in this case, a relative spatial relation will be explained accordingly. 
     As used herein, the term “A or B” comprises “A and B” and “A or B”, not exclusively “A” or “B”, unless otherwise specified. 
     As used herein, the word “basically” means including any minor changes caused by design or manufacturing defects, device or component tolerances, environmental influences, and/or other factors. The word “basically” also allows for deviation from the perfect or ideal situation due to parasitic effects, noise, and other practical considerations that may be present in the actual implementation. 
     In addition, for reference purposes only, “first”, “second” and similar terms may also be used herein, and thus are not intended to be limiting. For example, unless the context clearly indicates, the words “first”, “second” and other such numerical words involving structures or elements do not imply a sequence or order. 
     It should also be understood that when the terms “comprise” and “include” and other forms thereof indicate the presence of the specified feature, entirety, step, operation, unit and/or component, but does not exclude the presence or addition of one or a plurality of other features, steps, operations, units and/or components and/or combinations thereof. 
     It should be noted that, as used herein, phase centers other than the phase center of an entire array, such as the phase centers of radiating elements, phase centers of sub-arrays and the phase centers of the combination of sub-arrays, are also called “sub-phase centers” of arrays. 
       FIG.  3 A  is a schematic diagram of the feeding configuration of some arrays in a base station antenna according to an embodiment of the present invention. The base station antenna comprises a plurality of transversely adjacent arrays  41  to  44 , each of which includes a plurality of radiating elements that are arranged along the longitudinal direction of the antenna, and each array is fed by a corresponding phase shifter (not shown). In two adjacent arrays, the longitudinal position of each radiating element in one array is staggered with respect to that of the corresponding radiating element in the other array by a stagger amount s, which is equal to half of the distance d between two adjacent radiating elements in one array. 
     The radiating elements in each array can be divided into sub-arrays, and each sub-array is coupled to a corresponding output of the phase shifter. In adjacent arrays  41  and  42 , the phase centers of sub-array  411  of array  41  and sub-array  421  of array  42 , and those of sub-arrays of  413  and  423 , and those of sub-arrays of  415  and  425 , are basically aligned, while the phase centers of sub-arrays  412  and  422 , and those of sub-arrays of  414  and  424  are staggered by a distance s. It can be understood that because the longitudinal positions of the arrays  41  and  42  are staggered, the numbers of radiation elements comprised in the sub-arrays whose phase centers are basically aligned at the corresponding positions of the two arrays are different. For example, the phase-aligned sub-arrays shown in the figure comprise two and three radiating elements, respectively. It should be understood that sub-arrays including other numbers of radiating elements can also be phase-aligned, for example, sub-arrays respectively including one and two radiating elements, sub-arrays respectively including one and four radiating elements, etc. 
     If the phase centers of all sub-arrays in one array are aligned with the phase centers of the corresponding sub-arrays in an adjacent array, then the phase centers of the two arrays are aligned. Therefore, those aligned sub-arrays will not make the phase centers of the two arrays staggered. For the convenience of analysis, only the sub-arrays  412 ,  414 ,  422 ,  424  with misaligned phase centers in the arrays  41  and  42  are shown in  FIG.  3 B , and those sub-arrays that do not offset the phase centers of the arrays  41  and  42  are omitted. When the electronic downtilt angles of the arrays  41  and  42  are θ, the phases to φ1 of φ8 the radiating elements  51  to  58  ( FIG.  3 B ) at a specific elevation angle of the elevation plane are as follows, respectively, where the radiating element  58  is set as a reference point, that is, the phase of the radiating element  58  is 0.
         φ1=−φ0+6kd sin θ   φ2=−φ0+5.5kd sin θ   φ3=0+5kd sin θ   φ4=0+4.5kd sin θ   φ5=−φ0+1.5kd sin θ   φ6=−φ0+kd sin θ   φ7=0+0.5kd sin θ   φ8=0
 
where φ0 is the preset phase difference (for example, caused by the feeding line) between two radiating elements in a sub-array (for example, a group of radiating elements which are coupled to the output of the same phase shifter and fed by the same feeding plate), k is the transmission coefficient of electromagnetic waves in vacuum, and its value is
       

     
       
         
           
             
               
                 2 
                 ⁢ 
                 π 
                 ⁢ 
                 f 
               
               c 
             
             . 
           
         
       
     
     When the electronic downtilt angle is θ, the phase of the combination of sub-arrays  412  and  414  at the specific elevation angle is −0.5φ0+3kd sin θ. In particular, the phase of sub-array  412  is the average of the phase centers of radiating elements  55  whose phase is −φ0+1.5kd sin θ and  57  whose phase is 0+0.5kd sin θ, which is −0.5φ0+kd sin θ. Similarly, the phase of sub-array  414  is the average of the phase centers of radiating elements  52  whose phase is −φ0+5.5kd sin θ and  54  whose phase is 0+4.5kd sin θ, which is −0.5φ0+5kd sin θ. The phase of the combination of sub-arrays  412  and  414  at the specific elevation angle of the elevation plane is −0.5φ0+3kd sin θ. The phase of the combination of sub-arrays  422  and  424  at the specific elevation angle of the elevation plane can similarly be calculated as −0.5φ0+3kd sin θ. It can be seen that the phase of the combination of sub-arrays  412  and  414  is consistent with that of the combination of sub-arrays  422  and  424 , and this is true for any elevation angle. That is, at any point on the elevation plane, the phase of the combination of sub-arrays  412  and  414  is consistent with that of the combination of sub-arrays  422  and  424 . Therefore, the phase center of the combination of sub-arrays  412  and  414  is aligned with the phase center of the combination of sub-arrays  422  and  424 . It should be noted that although sub-arrays  412  and  414  of array  41  are coupled to different outputs of the phase shifter, they are all fed by the same phase shifter. The phase shifter has only one input (usually connected with radio devices other than the base station antenna by cable), that is, the time that the signal is fed to the sub-array  412  is the same as the time that the signal is fed to the sub-array  414 , so the electromagnetic radiation of the sub-array  412  and that of the sub-array  414  can be superimposed in space, and the concept of the phase or phase center of the combination of the sub-arrays  412  and  414  exists. The same is true for sub-arrays  422  and  424 . 
     In sum, in adjacent arrays  41  and  42 , the phase centers of sub-arrays  411  and  421 , sub-arrays  413  and  423 , and sub-arrays  415  and  425  are basically aligned, and the phase centers of sub-arrays  412  and  414 , and sub-arrays  422  and  424  are also basically aligned, so the phase center of array  41  is basically aligned with that of array  42 . In the base station antenna according to this embodiment of the present invention, by designing the feeding configuration of two adjacent arrays of radiating elements, the phase centers of two arrays with staggered positions are aligned as much as possible, so that the base station antenna not only has the advantage of staggered array positions, but also can reduce or even eliminate the adverse effects caused by the misalignment of phase centers between arrays. 
     Thus, the base station antenna of  FIG.  3 A  includes a first array  41  that has a plurality of first radiating elements arranged along a longitudinal direction and a second array  42  that includes a plurality of second radiating elements arranged along the longitudinal direction. The second array  42  is transversely adjacent the first array  41 . The longitudinal positions of the second radiating elements are staggered from the longitudinal positions of the first radiating elements. The first array  41  comprises first and second sub-arrays (e.g., sub-arrays  412 ,  414 ), each of which comprises one or a plurality of adjacent first radiating elements. Moreover, a sub-phase center of the combination of the first and second subarrays (e.g., sub-arrays  412 ,  414 ) is basically aligned with a sub-phase center of the second array (e.g., the phase center of sub-array  423  and/or the phase center of the combination of sub-arrays  422 ,  424 ). 
     The first array  41  may comprise a first column of first radiating elements, and the second array  42  may comprise a second column of second radiating elements that is transversely adjacent the first column. The longitudinal positions of the first column and the second column are staggered by a first staggered amount. The first column has a first sub-phase center (e.g., the phase center of sub-array  413 ) and the second column has a second sub-phase center (e.g., the phase center of sub-array  423 ), and the longitudinal positions of the first and second sub-phase centers are basically aligned. The first column comprises first and second subsets of radiating elements (e.g., sub-arrays  412 ,  414 ), and a phase center of the combination of the first and second subsets basically coincides with the first sub-phase center. 
     As can also be seen in  FIG.  3 A , a phase center of a first sub-array (sub-array  412 ) of the first array  41  is a first distance above a phase center of the first array  41 , and a phase center of a second sub-array (sub-array  414 ) of the first array  41  is the first distance below the phase center of the first array  41 . Likewise, a phase center of a first sub-array (sub-array  422 ) of the second array  42  is a second distance above a phase center of the second array  42 , and a phase center of a second sub-array (sub-array  424 ) of the second array  42  is the second distance below the phase center of the second array  42 . The phase center of the first array  41  and the phase center of the second array  42  are aligned along a transverse direction, and the first distance is different from the second distance. 
     The difference between the first distance and the second distance is less than the distance “d” between two adjacent first radiating elements in the first array. The difference between the first distance and the second distance may equal to half the distance “d” between two adjacent first radiating elements in the first array. As can also be seen from  FIG.  3 A , a phase center of the combination of the first and second sub-arrays  412 ,  414  of the first array  41  may be co-located with the phase center of the first array  41 . 
     It should be noted that each array  41 - 44  includes radiating elements that are exactly aligned along respective longitudinal axes. It will be appreciated that in other cases, the arrays/columns  41 - 44  may have some degree of horizontal stagger. 
     The positions of the two combined sub-arrays in the arrays can be arranged as required. Combined with the above description with reference to  FIG.  3 B , it can be known that the phase of each radiating element is related to its position in the array (i.e., the distance from the reference point) when the elevation angle and downtilt angle are fixed. Moreover, when the numbers of radiating elements in the mutually combined sub-arrays are the same, the two sub-arrays are symmetrical with respect to the transverse axis passing through the phase center of the combination. Therefore, it is only necessary to symmetrically arrange the two sub-arrays combined with each other on both sides of the transverse axis passing through the phase center of the combination, without limiting the distance from the sub-arrays to the phase center of the combination. 
     For example, in the embodiment shown in  FIG.  4 A , the phase center of the combination of the uppermost sub-array  411  and the lowermost sub-array  415  of the array  41  is basically aligned with the phase center of the combination of the uppermost sub-array  421  and the lowermost sub-array  425  of the array  42 . Other sub-arrays  412  and  422 , sub-arrays  413  and  423 , sub-arrays  414  and  424  whose phase centers are aligned with each other are located in the middle of the respective arrays  41  and  42 . 
     In the above embodiments, the sub-arrays that are combined with each other to have matching phase centers with a combination of sub-arrays in an adjacent array have two radiating elements. It should be understood that other numbers of radiating elements can be included in the sub-arrays that are combined with each other. For example, in the embodiment shown in  FIG.  4 B , the phase center of the combination of sub-array  412  containing three radiating elements and sub-array  414  containing three radiating elements is basically aligned with that of the combination of sub-array  422  containing three radiating elements and sub-array  423  containing three radiating elements. In addition, the array  41  also comprises a sub-array  413  whose phase center is aligned with the phase center of the array  41 . In this case, although there is no sub-array aligned with the sub-array  413  in the array  42 , the phase centers of the arrays  41  and  42  are still aligned. It should be noted that in the embodiment shown in  FIG.  4 B , the numbers of sub-arrays in arrays  41  and  42  are different, with array  41  including five sub-arrays  411  to  415  and array  42  including four sub-arrays  421  to  424 . Array  41  can be fed with a phase shifter having 5 outputs, and array  42  can be fed with a phase shifter having 4 outputs, or can be fed with 4 outputs of a phase shifters having 5 outputs. The feeding modes of phase shifters in the following adjacent arrays with different sub-arrays are similar, so they will not be described again. 
     In some cases, the phase centers of the arrays can be slightly staggered. As long as the staggered amount of the phase centers of the arrays is smaller than the staggered amount of the physical centers of the arrays, it can obtain smaller distortion than the arrays with the feeding mode shown in  FIG.  2   , that is, better RF performance. It can be understood that the smaller the stagger amount of the phase centers between arrays, the smaller the distortion of radiation patterns of these arrays. In the embodiment shown in  FIG.  4 C , the phase centers of sub-arrays  411  and  421  and sub-arrays  413  and  423  are basically aligned, and the phase centers of the combination of sub-arrays  412  and  414  and the combination of sub-arrays  422  and  424  are basically aligned, while the phase centers of sub-arrays  415  and  425  located at the lowermost ends of the arrays  41  and  42  are staggered by a distance s. Experiments show that there are no phase-aligned sub-arrays in a few radiating element sub-arrays, which will not cause noticeable adverse effects on the RF performance of the base station antenna. Especially, as in this embodiment, the sub-arrays with misaligned phases are arranged at the end of the array, i.e., where the amplitude of the fed RF signal is the smallest, so as to minimize the influence of the phase offset of the sub-arrays on the phase offset of the entire array. 
     In the above-described embodiment, the feeding configurations of arrays  43  and  44  are the same as those of arrays  41  and  42 , respectively, so they will not be described again. In the embodiment described below, only two adjacent arrays  61  and  62  of the base station antenna are shown. It should be understood that the base station antenna can also comprise more arrays with similar feeding configurations or arrays with other known feeding configurations. 
     In some cases, the physical centers of two adjacent arrays are basically aligned. For example, the numbers of radiating elements in two arrays differ by one. In these cases, it is only necessary to adjust the phase center of each array to the physical center of the array by designing the feeding configuration so as to make the phase centers of two adjacent arrays basically aligned. In addition, adjacent arrays may not even comprise sub-arrays with aligned phase centers. In the embodiment shown in  FIG.  5 A , two adjacent arrays  61  and  62  do not comprise sub-arrays with aligned phase centers, and the phase centers of the corresponding sub-arrays  611  and  621 , sub-arrays  612  and  622 , sub-arrays  614  and  623 , and sub-arrays and  615  and  624  are all staggered by a distance s. In addition, in array  62 , there is no sub-array aligned with the phase center of sub-array  613  located in the middle of the array  61 . Nevertheless, the phase center of the combination of sub-arrays  611  and  615 , the phase centers of the combination of sub-arrays  612  and  614 , and the phase center of sub-array  613  may all basically coincide with the physical center of the array  61 . The phase center of the combination of sub-arrays  621  and  624  and the phase center of the combination of sub-arrays  622  and  623  may all basically coincide with the physical center of the array  62 . The physical centers of the arrays  61  and  62  are basically aligned. Therefore, the phase centers of the arrays  61  and  62  are basically aligned. 
     In the above embodiments, the sub-arrays combined with each other all contain more than one radiating element. In the embodiment shown in  FIG.  5 B , the phase centers of sub-arrays  611  and  621 , sub-arrays  612  and  622 , sub-arrays  614  and  625 , and sub-arrays  615  and  626  are basically aligned, and the phase center of the combination of sub-arrays  623  and  624  is basically aligned with the phase center of sub-array  613 . Therefore, the phase centers of the entire arrays  61  and  62  are basically aligned. In the embodiment shown in  FIG.  5 C , the phase centers of sub-arrays  612  and  621 , sub-arrays  613  and  622 , sub-arrays  615  and  625 , and sub-arrays  616  and  626  are basically aligned. The phase center of the combination of sub-arrays  623  and  624  and the phase center of the combination of sub-arrays  611  and  617  are basically aligned with the phase center of sub-array  614 . Therefore, the phase centers of arrays  61  and  62  are basically aligned. 
     The number of radiating elements contained in the combined sub-arrays of one array may be different from that of radiating elements contained in the combined sub-arrays of another array. In the embodiment shown in  FIG.  5 D , the phase centers of sub-arrays  612  and  621 , sub-arrays  613  and  622 , sub-arrays  615  and  625 , and sub-arrays  616  and  626  are basically aligned. The phase center of the combination of sub-arrays  623  and  624  and the phase center of the combination of sub-arrays  611  and  617  are basically aligned with the phase center of sub-array  614 . Therefore, the phase centers of arrays  61  and  62  are basically aligned. In the embodiment shown in  FIG.  5 E , the phase centers of the sub-arrays  613  and  623  are basically aligned. The phase center of the combination of sub-arrays  612  and  614  and the phase center of the combination of sub-arrays  611  and  615  are basically aligned with the phase center of sub-array  613 . The phase center of the combination of sub-arrays  622  and  624  and the phase center of the combination of sub-arrays  621  and  625  are basically aligned with the phase center of sub-array  623 . Therefore, the phase centers of arrays  61  and  62  are basically aligned. 
     Although some specific embodiments of the present invention have been described in detail by examples, those skilled in the art should understand that the above examples are only for illustration, not for limiting the scope of the present invention. The embodiments disclosed herein can be combined arbitrarily without departing from the spirit and scope of the present invention. Those skilled in the art should also understand that various modifications can be made to the embodiments without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the claims attached.