Patent Publication Number: US-2022231427-A1

Title: Circular polarization array antenna device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application of International Patent Application No. PCT/JP2020/031600, filed Aug. 21, 2020, which claims priority to Japanese Patent Application No. 2019-192022, filed Oct. 21, 2019, the entire contents of each of which being incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a circular polarization array antenna device. 
     BACKGROUND ART 
     The circular polarization array antenna is realized by arranging a plurality of radiation elements each radiating a circularly polarized wave in proximity to each other. In an ideal circularly polarized wave, a magnitude of a rotating electric field is constant, but in reality, the magnitude of the rotating electric field may not be constant and may be distorted into an elliptical shape. A ratio of a minor axis to a major axis of the elliptical shape of the circularly polarized wave is referred to as an “axial ratio”. In order to make a circularly polarized wave an ideal circularly polarized wave, it is required to improve axial ratio characteristics. 
     As a technique for improving the axial ratio characteristics of the circular polarization array antenna, there is a technique called a sequential array. In the sequential array, a plurality of circularly polarized radiation elements are arranged while each of which is rotated at an arbitrary angle. It is known that such an arrangement may improve the axial ratio characteristics of the entire circular polarization array antenna even when the axial ratio characteristics of a single radiation element are not preferable. 
     Japanese Unexamined Patent Application Publication No. 6-140835 discloses a circular polarization array antenna device in which a plurality of circularly polarized radiation elements are arranged in a matrix. In this circular polarization array antenna, 16 circularly polarized radiation elements are sequentially arranged in a matrix of four rows and four columns (even-numbered rows and even-numbered columns) such that a positional relationship between adjacent radiation elements comes into a positional relationship in which the radiation elements are rotated by a predetermined angle with each other and translated. 
     CITATION LIST 
     Patent Document 
     Patent Document 1: Japanese Unexamined Patent Application Publication No. 6-140835 
     SUMMARY 
     Technical Problem 
     In a case that a plurality of circularly polarized radiation elements are arranged in a matrix, arranging the plurality of circularly polarized radiation elements in a matrix of even-numbered rows and even-numbered columns as in the circular polarization array antenna disclosed in Japanese Unexamined Patent Application Publication No. 6-140835 may more effectively improve the axial ratio characteristics. 
     However, the size of the circular polarization array antenna may be restricted depending on the size of a device to which the circular polarization array antenna is attached, and there may be a case that the number of rows of the arrangement has to be an odd number instead of an even number (that is, the number of radiation elements in a single column has to be an odd number). In this case, the plurality of radiation elements are arranged in a matrix of odd-numbered rows and even-numbered columns, and improving the axial ratio characteristics is considered to be hard. 
     The present disclosure has been made in order to solve the problem above, and one object of the present disclosure is to make it simple to improve axial ratio characteristics even in the case that a plurality of radiation elements each capable of radiating a circularly polarized wave are arranged in a matrix of odd-numbered rows and even-numbered columns. 
     Solution to Problem 
     A circular polarization array antenna device according to the present disclosure includes an element group including a plurality of elements each capable of radiating a circularly polarized wave. The plurality of elements are arranged in a matrix of N rows and M columns, in which N is an odd number of three or more and M is four or more being a multiple of four. The plurality of elements include the same number of elements of four types having a positional relationship rotationally symmetric with each other. The plurality of elements are arranged such that adjacent elements are of types different from each other. 
     In the element group described above, the plurality of elements are arranged in a matrix of odd-numbered rows (N rows) and even-numbered columns (M columns). The plurality of elements include the same number of elements of four types and are arranged such that adjacent elements are of types different from each other. Consequently, even in the case that a plurality of elements each radiating a circularly polarized wave are arranged in a matrix of odd-numbered rows and even-numbered columns, it may be made simple to improve the axial ratio characteristics. 
     A circular polarization array antenna device according to another aspect of the present disclosure includes an element group that includes a plurality of elements each capable of radiating a circularly polarized wave and arranged in a matrix of three rows and K columns, in which K is an even number of four or more. The plurality of elements include elements of four types having a positional relationship rotationally symmetric with each other. The elements of four types include a first type element, a second type element obtained by rotating the first type element by 90 degrees in a predetermined direction, a third type element obtained by rotating the first type element by 270 degrees in the predetermined direction, and a fourth type element obtained by rotating the first type element by 180 degrees in the predetermined direction. The plurality of elements are included in: a plurality of first element groups each of which includes four elements arranged in two rows and two columns and which are disposed in a zigzag manner in a column direction; and a plurality of second element groups each of which includes two elements arranged in one row and two columns and each of which is disposed adjacent to a corresponding one of the plurality of first element groups in a row direction. The four elements included in the first element group include each one of the elements of four types. The two elements included in the second element group include elements of two of the four types. 
     Advantageous Effects 
     According to the present disclosure, even in a case that a plurality of radiation elements each capable of radiating a circularly polarized wave are arranged in a matrix of odd-numbered rows and even-numbered columns, it may be made simple to improve the axial ratio characteristics. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an example of a block diagram of a communication device to which an antenna device is applied. 
         FIG. 2  is a transparent perspective view of the communication device illustrating the inside thereof. 
         FIG. 3  is a diagram illustrating an arrangement of a plurality of radiation elements in the antenna device. 
         FIG. 4  is a diagram illustrating an arrangement pattern of a first type radiation element. 
         FIG. 5  is a diagram illustrating an arrangement pattern of a second type radiation element. 
         FIG. 6  is a diagram illustrating an arrangement pattern of a third type radiation element. 
         FIG. 7  is a diagram illustrating an arrangement pattern of a fourth type radiation element. 
         FIG. 8  is a graph illustrating axial ratio characteristics of a circularly polarized wave radiated from the antenna device. 
         FIG. 9  is a transparent view of an antenna layer, a wiring layer, and a GND layer of the antenna device viewed in a Z axis direction. 
         FIG. 10  is a diagram illustrating an example of an arrangement of a plurality of radiation elements in an antenna device according to Modification 1. 
         FIG. 11  is a transparent view of an antenna layer, a wiring layer, and a GND layer of an antenna device according to Modification 2 viewed in the Z axis direction. 
         FIG. 12  is a transparent view of an antenna layer, a wiring layer, and a GND layer of an antenna device according to Modification 3 viewed in the Z axis direction. 
         FIG. 13  is a diagram illustrating an arrangement of a plurality of radiation elements in an antenna device according to Modification 6. 
         FIG. 14  is a diagram illustrating an arrangement of a plurality of radiation elements in an antenna device according to a comparative example. 
         FIG. 15  is a diagram illustrating an arrangement of the plurality of radiation elements in the antenna device according to Modification 6. 
         FIG. 16  is a graph comparing the axial ratio characteristics of the antenna device according to the comparative example with the axial ratio characteristics of the antenna device according to Modification 6. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference signs, and description thereof will not be repeated. 
     (Basic Configuration of Communication Device) 
       FIG. 1  is an example of a block diagram of a communication device  10  to which an antenna device  120  according to the present embodiment is applied. The communication device  10  is configured to be capable of transmitting a circularly polarized wave from the antenna device  120 . The communication device  10  may be, for example, a terminal transmitting data to a wearable terminal (such as a head-mounted display, for example) whose relative position to the communication device  10  may change. In addition, the communication device  10  may be a communication terminal supporting “WiGig” which is a wireless communication standard mainly using 60 GHz band radio, for example. 
     The communication device  10  includes an antenna module  100  including the antenna device  120  and a BBIC  200  constituting a baseband signal processing circuit. The antenna module  100  includes an RFIC  110  that is an example of a power feeding component in addition to the antenna device  120 . The communication device  10  up-converts a signal transferred from the BBIC  200  to the antenna module  100  into a radio frequency signal and radiates the radio frequency signal from the antenna device  120 . The communication device  10  down-converts a radio frequency signal received by the antenna device  120  and processes the signal in the BBIC  200 . 
     The antenna device  120  includes a plurality of radiation elements  121  each configured to be capable of radiating a circularly polarized wave. In  FIG. 1 , for ease of explanation, only a configuration corresponding to four radiation elements  121  among the plurality of radiation elements  121  included in the antenna device  120  is illustrated, and configurations corresponding to other radiation elements  121  having the same configuration are omitted. In the present embodiment, the radiation element  121  is a patch antenna having a substantially square flat plate shape. 
     The RFIC  110  includes switches  111 A to  111 D,  113 A to  113 D, and  117 , power amplifiers  112 AT to  112 DT, low noise amplifiers  112 AR to  112 DR, attenuators  114 A to  114 D, phase shifters  115 A to  115 D, a signal multiplexer/demultiplexer  116 , a mixer  118 , and an amplifier circuit  119 . 
     When transmitting a radio frequency signal, the switches  111 A to  111 D and  113 A to  113 D are switched to the power amplifiers  112 AT to  112 DT side, and the switch  117  is switched to a transmission-side amplifier in the amplifier circuit  119 . When a radio frequency signal is received, the switches  111 A to  111 D and  113 A to  113 D are switched to the low noise amplifiers  112 AR to  112 DR side, and the switch  117  is switched to a reception-side amplifier in the amplifier circuit  119 . 
     A signal transferred from the BBIC  200  is amplified by the amplifier circuit  119 , and is up-converted by the mixer  118 . The transmission signal, which is an up-converted radio frequency signal, is divided into four waves by the signal multiplexer/demultiplexer  116 . The waves pass through four signal paths and are fed to the respective different radiation elements  121 . At this time, by individually adjusting phase shift degrees in the phase shifters  115 A to  115 D disposed in respective signal paths, circularly polarized waves having the same phase are radiated from the respective radiation elements  121  of the antenna device  120 . 
     Reception signals, which are radio frequency signals received by the radiation elements  121 , pass through respective four different signal paths and are combined by the signal multiplexer/demultiplexer  116 . The combined received signal is down-converted by the mixer  118 , amplified by the amplifier circuit  119 , and transferred to the BBIC  200 . 
     The RFIC  110  is formed as a single chip integrated circuit component including the circuit configuration described above, for example. Alternatively, the devices (switches, power amplifiers, low noise amplifiers, attenuators, and phase shifters) corresponding to each radiation element  121  in the RFIC  110  may be formed as a single chip integrated circuit component for each corresponding radiation element  121 . 
     (Antenna Device and Arrangement of Radiation Elements) 
       FIG. 2  is a transparent perspective view of the communication device  10  illustrating the inside thereof. The communication device  10  is covered with a housing  11 . The housing  11  accommodates the antenna device  120 , the RFIC  110 , a mounting substrate  20 , and the like. 
     The antenna device  120  includes a plate-shaped dielectric substrate  131  having a multilayer structure, and the plurality of radiation elements  121  disposed inside the dielectric substrate  131 . The dielectric substrate  131  is disposed on a side surface  22  of the mounting substrate  20  with the RFIC  110  interposed therebetween. Hereinafter, as illustrated in  FIG. 2 , a normal direction of the side surface  22  of the mounting substrate  20  is referred to as a “Z axis direction”, a normal direction of a main surface  21  of the mounting substrate  20  is referred to as an “X axis direction”, and a direction perpendicular to the Z axis direction and the X axis direction is referred to as a “Y axis direction”. 
     The dielectric substrate  131  is provided with an antenna layer in which the plurality of radiation elements  121  are arranged. In the antenna layer, the plurality of radiation elements  121  are arranged in a matrix along the X axis direction and the Y axis direction. Specifically, 12 radiation elements  121  are arranged in a matrix of three rows and four columns with the X axis direction being a “row” and the Y axis direction being a “column”. 
     In general, in a case that a plurality of circularly polarized radiation elements are arranged in a matrix, arranging the plurality of circularly polarized radiation elements in a matrix of even-numbered rows and even-numbered columns, such as in the circular polarization array antenna disclosed in Japanese Unexamined Patent Application Publication No. 6-140835, may more effectively improve the axial ratio characteristics. 
     However, in the antenna device  120  according to the present embodiment, the length of the dielectric substrate  131  in the X axis direction is limited by the thickness (length in the X axis direction) T of the housing  11 , and thus, the number of rows of the arrangement of the plurality of radiation elements  121  is three rows (odd-numbered rows). Accordingly, without any countermeasures, it may be hard to improve the axial ratio characteristics as compared with the case that the plurality of radiation elements  121  are arranged in a matrix of even-numbered rows and even-numbered columns. 
     Then, in the antenna device  120  according to the present embodiment, arranging the plurality of radiation elements  121  in the following manner makes it simple to improve the axial ratio characteristics even in the case that the plurality of radiation elements  121  are arranged in a matrix of three rows and four columns (odd-numbered rows and even-numbered columns). 
       FIG. 3  is a diagram illustrating an arrangement of the plurality of radiation elements  121  in the antenna device  120  according to the present embodiment. In the present embodiment, the 12 radiation elements  121  are arranged in a matrix of three rows and four columns, as described above. Each radiation element  121  has two feed points. Two radio frequency signals having a phase difference of 90° relatively to each other are supplied from a hybrid circuit  132  illustrated in  FIG. 9 , which will be described later, to the two feed points of each radiation element  121 . With this, a circularly polarized wave is radiated from each radiation element  121 . 
     The 12 radiation elements  121  include radiation elements of four types having a positional relationship rotationally symmetric with each other. That is, the 12 radiation elements  121  include a first type radiation element  121   a,  a second type radiation element  121   b,  a third type radiation element  121   c,  and a fourth type radiation element  121   d.  The same numbers (that is, three) of the radiation elements  121   a  to  121   d  of four types are included. 
       FIG. 4  is a diagram illustrating an arrangement pattern of the first type radiation element  121   a.    FIG. 5  is a diagram illustrating an arrangement pattern of the second type radiation element  121   b.    FIG. 6  is a diagram illustrating an arrangement pattern of the third type radiation element  121   c.    FIG. 7  is a diagram illustrating an arrangement pattern of the fourth type radiation element  121   d.  In the following description, any integer from 1 to 3 is denoted by n, any integer from 1 to 4 is denoted by m, and a position of the n-th row and the m-th column in a matrix is denoted by (n×m). 
     As illustrated in  FIG. 4 , the first type radiation element  121   a  is disposed at positions of (1×1), (2×3), and (3×1). Each radiation element  121   a  includes a feed point P 1   a  disposed at a negative direction side of the Y axis relative to a surface center, and a feed point P 2   a  disposed at a positive direction side of the X axis relative to the surface center. 
     As illustrated in  FIG. 5 , the second type radiation element  121   b  is disposed at positions of (1×2), (2×4), and (3×2). Each radiation element  121   b  includes a feed point P 1   b  disposed at the negative direction side of the X axis relative to the surface center, and a feed point P 2   b  disposed at the negative direction side of the Y axis relative to the surface center. The second type radiation element  121   b  is obtained by rotating the first type radiation element  121   a  clockwise by 90 degrees and translating the rotated first type radiation element  121   a.    
     As illustrated in  FIG. 6 , the third type radiation element  121   c  is disposed at positions of (1×3), (2×1), and (3×3). Each radiation element  121   c  includes a feed point P 1   c  disposed at the positive direction side of the X axis relative to the surface center, and a feed point P 2   c  disposed at the positive direction side of the Y axis relative to the surface center. The third type radiation element  121   c  is obtained by rotating the first type radiation element  121   a  clockwise by 270 degrees and translating the rotated first type radiation element  121   a.    
     As illustrated in  FIG. 7 , the fourth type radiation element  121   d  is disposed at positions of (1×4), (2×2), and (3×4). Each radiation element  121   d  includes a feed point P 1   d  disposed at the positive direction side of the Y axis relative to the surface center, and a feed point P 2   d  disposed at the negative direction side of the X axis relative to the surface center. The fourth type radiation element  121   d  is obtained by rotating the first type radiation element  121   a  clockwise by 180 degrees with surface center being the rotational axis, and translating the rotated first type radiation element  121   a.    
     With the arrangement above, the plurality of radiation elements  121  are arranged such that any one radiation element  121  and the radiation elements  121  disposed around (vertically, horizontally, and obliquely) the one radiation element  121  are of types different from each other. For example, the first type radiation element  121   a  at (1×1) is of a different type from any of the third type radiation element  121   c  at (2×1) adjacent in the lower side, the second type radiation element  121   b  at (1×2) adjacent in the right side, and the fourth type radiation element  121   d  at (2×2) adjacent in the obliquely lower right. Further, for example, the first type radiation element  121   a  at (2×3) is of a different type from any of: the third type radiation element  121   c  at (1×3) adjacent in the upper side, the third type radiation element  121   c  at (3×3) adjacent in the lower side, the fourth type radiation element  121   d  at (2×2) adjacent in the left side, the second type radiation element  121   b  at (2×4) adjacent in the right side, the second type radiation element  121   b  at (1×2) adjacent in the obliquely upper left, the second type radiation element  121   b  at (3×2) adjacent in the obliquely lower left, the fourth type radiation element  121   d  at (1×4) adjacent in the obliquely upper right, and the fourth type radiation element  121   d  at (3×4) adjacent in the obliquely lower right. 
     By arranging the radiation elements  121   a  to  121   d  of four types as described above, the plurality of radiation elements  121  are uniformly and sequentially arranged, and overall balance is achieved. Consequently, even in the case that the plurality of radiation elements  121  are arranged in a matrix of three rows and four columns, it may be made simple to improve the axial ratio characteristics. 
     With the rotation position (rotation angle) of the first type radiation element  121   a  being “reference (0 degrees)”, the clockwise rotation position of each radiation element  121  is expressed as follows. The rotation position of the second type radiation element  121   b  is “90 degrees”, the rotation position of the third type radiation element  121   c  is “270 degrees”, and the rotation position of the fourth type radiation element  121   d  is “180 degrees”. In light of the above, the phase shift degrees of the phase shifters  115 A to  115 D are individually adjusted as follows when the phase of a signal supplied to the first type radiation element  121   a  is expressed as a “reference phase”. The phase of a signal supplied to the second type radiation element  121   b  is “reference phase minus 90 degrees”, the phase of a signal supplied to the third type radiation element  121   c  is “reference phase minus 270 degrees”, and the phase of a signal supplied to the fourth type radiation element  121   d  is “reference phase minus 180 degrees”. With this, circularly polarized waves of the same phase are radiated from the respective radiation elements  121  of the antenna device  120 . 
       FIG. 8  is a graph illustrating axial ratio characteristics of a circularly polarized wave radiated from the antenna device  120  according to the present embodiment. In  FIG. 8 , the horizontal axis represents a frequency (GHz in unit), and the vertical axis represents an axial ratio (dBA in unit). In general, with 3 dBA being a threshold value, the axial ratio characteristics is evaluated as preferable when the axial ratio is 3 dBA or less. In the antenna device  120  according to the present embodiment, the axial ratio is suppressed to be substantially less than 1 dBA in the frequency band of about 60 GHz with the above-described arrangement pattern, and therefore, it may be understood that the axial ratio characteristics are preferable. 
     As described above, in the antenna device  120  according to the present embodiment, the 12 radiation elements  121  each radiating a circularly polarized wave are arranged in a matrix of three rows and four columns. The 12 radiation elements  121  includes three sets of radiation elements  121   a  to  121   d  of four types having a positional relationship rotationally symmetric with each other. The first type radiation element  121   a  is disposed at positions of (1×1), (2×3), and (3×1). The second type radiation element  121   b  is disposed at positions of (1×2), (2×4), and (3×2). The third type radiation element  121   c  is disposed at positions of (1×3), (2×1), and (3×3). The fourth type radiation element  121   d  is disposed at positions of (1×4), (2×2), and (3×4). 
     With the arrangement above, the plurality of radiation elements  121  are sequentially arranged such that radiation elements  121  adjacent to each other in vertical, horizontal, and oblique directions are of different types. Consequently, even in the case that the plurality of radiation elements  121  are arranged in a matrix of three rows and four columns, it may be made simple to improve the axial ratio characteristics. 
     The “antenna device  120 ” and the “12 radiation elements  121 ” according to the present embodiment may correspond to the “circular polarization array antenna device” and the “plurality of elements” of the present disclosure, respectively. The element group including the 12 radiation elements  121  according to Modification 1 may correspond to the “element group” of the present disclosure. Further, the “first type radiation element  121   a ”, the “second type radiation element  121   b ”, the “third type radiation element  121   c ”, and the “fourth type radiation element  121   d ” according to the present embodiment may correspond to the “first type element”, the “second type element”, the “third type element”, and the “fourth type element” of the present disclosure, respectively. 
     (Configuration of Hybrid Circuit) 
     The antenna device  120  has a multilayer structure in which an antenna layer, a wiring layer, and a GND layer are laminated in this order from the positive direction to the negative direction of the Z axis. 
       FIG. 9  is a diagram in which the antenna layer, the wiring layer, and the GND layer of the antenna device  120  are viewed transparently in the Z axis direction and arranged in this order from the top. Note that, only an arrangement area of any single radiation element  121  is illustrated in  FIG. 9 . 
     The above-described radiation element  121  is arranged in the antenna layer. In  FIG. 9 , a shape of the radiation element  121  in which four corners are cut out is illustrated as an example. 
     In the wiring layer, one hybrid circuit  132  is disposed for one radiation element  121 . That is, 12 hybrid circuits  132  corresponding to the respective 12 radiation elements  121  are disposed in the wiring layer of the antenna device  120 . The hybrid circuit  132  is a 90 degrees hybrid circuit for supplying two radio frequency signals having a phase difference of 90 degrees to respective two feed points P 1  and P 2  of the corresponding radiation element  121 . 
     Specifically, the hybrid circuit  132  includes three terminals T 1  to T 3  and four linear transmission lines L 1  to L 4 . The terminals T 1  and T 2  are coupled to the feed points P 1  and P 2  of the radiation element  121  by lines, which are not illustrated, respectively. The terminal T 3  is coupled to the RFIC  110  by a line, which is not illustrated. 
     Each of the four transmission lines L 1  to L 4  is configured such that an electrical length thereof is ¼ of the wavelength of the radio frequency signal. The four transmission lines L 1  to L 4  are annularly coupled in this order. That is, one end of the transmission line L 1  is coupled to one end of the transmission line L 2 , another end of the transmission line L 2  is coupled to one end of the third transmission line, another end of the transmission line L 3  is coupled to one end of the transmission line L 4 , and another end of the transmission line L 4  is coupled to another end of the transmission line L 1 . The terminal T 1  is coupled to a coupling point between the transmission line L 1  and the transmission line L 2 . The terminal T 2  is coupled to a coupling point between the transmission line L 2  and the transmission line L 3 . The terminal T 3  is coupled to a coupling point between the transmission line L 1  and the transmission line L 4 . 
     A ground electrode  133  is disposed in the GND layer. The ground electrode  133  is provided with a power supply land H. A line for supplying a radio frequency signal from the RFIC  110  to the terminal T 3  of the hybrid circuit  132  is coupled to the power supply land H. 
     By supplying the radio frequency signal from the RFIC  110  to the hybrid circuit  132 , two radio frequency signals having a relative phase difference of 90° are supplied to the respective two feed points P 1  and P 2  of the radiation element  121 . That is, a signal inputted to the terminal T 3  of the hybrid circuit  132  from the RFIC  110  is branched into a signal outputted from the terminal T 1  to the feed point P 1  of the radiation element  121  through the transmission line L 1 , and a signal outputted from the terminal T 2  to the feed point P 2  of the radiation element  121  through the transmission lines L 4  and L 3 . The phase of the outputted signal from the terminal T 2  is delayed by 180 degrees (½ wavelength) relative to the signal inputted to the terminal T 3 , while the phase of the outputted signal from the terminal T 1  is delayed by 90 degrees (¼ wavelength) relative to the signal inputted to the terminal T 3 . With this, the phase of the outputted signal from the terminal T 2  may be delayed by 90 degrees (¼ wavelength) relative to the outputted signal from the terminal T 1 . Consequently, two radio frequency signals having a phase difference of 90 degrees may be supplied to the two feed points P 1  and P 2  of the radiation element  121 . 
     &lt;Modification 1&gt; 
     In the embodiment described above, there has been described the antenna device  120  in which the plurality of radiation elements  121  are arranged in a matrix of three rows and four columns. However, it is sufficient that the antenna device according to the present disclosure includes an element group in which a plurality of radiation elements are arranged in a matrix of odd-numbered rows and even-numbered columns, and the number of rows and the number of columns when a plurality of radiation elements are arranged in a matrix are not necessarily limited to the “three rows” and the “four columns” described above. 
       FIG. 10  is a diagram illustrating an example of an arrangement of the plurality of radiation elements  121  in an antenna device  120 A according to Modification 1. In the example illustrated in  FIG. 10 , 30 radiation elements  121  are arranged in a matrix of three rows and ten columns. In the arrangement above, a portion arranged in three rows and four columns in the center portion is defined as an “element group U”, and the element group U may have the arrangement pattern of the embodiment described above ( FIG. 3  to  FIG. 7 ), for example. With this, at least the portion of the element group U becomes the sequential arrangement, and therefore, it may be made simple to improve the axial ratio characteristics of the entire antenna device  120 A. 
     Further, also in the above-described “element group U”, it is sufficient that the number of rows and the number of columns when a plurality of radiation elements are arranged in a matrix, are respectively an odd number of three or more and four or more being a multiple of four (even number). The number of rows and the number of columns are not necessarily limited to the above-described “three rows” and “four columns”. The “element group U” according to Modification 1 may correspond to the “element group” of the present disclosure. 
     &lt;Modification 2&gt; 
     In the embodiment described above, there has been described an example in which the hybrid circuit  132  including the four linear transmission lines L 1  to L 4  is used (see  FIG. 9 ) as a circuit for supplying two radio frequency signals having a phase difference of 90 degrees to each radiation element  121 . However, in this example, the power supply land H is close to the end portion of the arrangement area of the radiation element  121  as illustrated in  FIG. 9 , and it is considered that forming the power supply land H in the arrangement area becomes hard. 
     Accordingly, in Modification 2, the two transmission lines L 1  and L 3  of the four transmission lines L 1  to L 4  are formed in a curved shape, so that the power supply land H is brought close to the center of the arrangement area of the radiation element  121  to make it simple to form the power supply land H in the arrangement area. 
       FIG. 11  is a diagram in which an antenna layer, a wiring layer, and a GND layer of the antenna device  120 A according to Modification 2 are viewed transparently in the Z axis direction and arranged in this order from the top. 
     In the wiring layer of the antenna device  120 A, a hybrid circuit  132 A is disposed instead of the above-described hybrid circuit  132 . The hybrid circuit  132 A differs from the above-described hybrid circuit  132  in that the linear transmission lines L 1  and L 3  are replaced by transmission lines L 1   a  and L 3   a  curved in an L-shape. Since other configurations of the hybrid circuit  132 A are basically the same as those of the above-described hybrid circuit  132 , detailed description thereof will not be repeated here. 
     As illustrated in  FIG. 11 , in the hybrid circuit  132 A according to Modification 2, the terminal T 3  is arranged at a position close to the terminals T 1  and T 2  by making the transmission lines L 1   a  and L 3   a  be a curved shape. With this, since the power supply land H becomes close to the center of the arrangement area of the radiation element  121 , it may be made simple to form the power supply land H in the arrangement area. 
     The “hybrid circuit  132 A”, “terminal T 1 ”, “terminal T 2 ”, “terminal T 3 ”, “first transmission line L 1   a ”, “second transmission line L 2 ”, “third transmission line L 3   a ”, and “fourth transmission line L 4 ” according to the present modification may correspond to the “hybrid circuit”, “first terminal”, “second terminal”, “third terminal”, “first transmission line”, “second transmission line”, “third transmission line”, and “fourth transmission line” of the present disclosure, respectively. 
     &lt;Modification 3&gt; 
     In the embodiment described above, there has been described an example in which the hybrid circuit  132  is used (see  FIG. 9 ) as a circuit for supplying two radio frequency signals having a phase difference of 90 degrees to each radiation element  121 . However, the hybrid circuit  132  may be changed to a simple branch circuit. 
       FIG. 12  is a diagram in which an antenna layer, a wiring layer, and a GND layer of an antenna device  120 B according to Modification 3 are viewed transparently in the Z axis direction and arranged in this order from the top. 
     A branch circuit  140 , instead of the above-described hybrid circuit  132 , is disposed in the wiring layer of the antenna device  120 B. 
     The branch circuit  140  is obtained by omitting the transmission lines L 1 , L 3  and L 4  from the above-described hybrid circuit  132 , and further, adding a transmission line L 5  for coupling the terminal T 1  and the terminal T 3  to the above-described hybrid circuit  132 . By supplying a radio frequency signal from the RFIC  110  to the branch circuit  140  above, two radio frequency signals having a phase difference of 90 degrees may be supplied to the radiation element  121 . That is, a signal inputted from the RFIC  110  to the terminal T 3  of the branch circuit  140  is branched into a signal outputted from the terminal T 1  to the feed point P 1  of the radiation element  121  through the transmission line L 5 , and a signal outputted from the terminal T 2  to the feed point P 2  of the radiation element  121  through the transmission lines L 5  and L 2 . The phase of the outputted signal from the terminal T 2  is delayed by 90 degrees (¼ wavelength), which is the electrical length of the transmission line L 2 , relative to the outputted signal from the terminal T 1 . Consequently, two radio frequency signals having a phase difference of 90 degrees may be supplied to the two feed points P 1  and P 2  of the radiation element  121 . 
     &lt;Modification 4&gt; 
     In the embodiment described above, there has been described the radiation element  121  of the two-point feed system as the circularly polarized radiation element. However, a radiation element of a single point feed system, which uses degeneracy obtained by making the shape of the radiation electrode asymmetric, may be used as a circularly polarized radiation element. 
     &lt;Modification 5&gt; 
     In the embodiment described above, there has been described an example in which the radiation element  121  is a patch antenna. However, it is sufficient that the radiation element  121  is an antenna capable of radiating a circularly polarized wave, and the radiation element  121  is not necessarily limited to a patch antenna. For example, the radiation element  121  may be a slot antenna. 
     &lt;Modification 6&gt; 
     In the embodiment described above, the arrangement of the radiation elements  121  in the antenna device  120  illustrated in  FIG. 3  to  FIG. 7  described above is regarded as a pattern in which three sets of radiation elements  121   a  to  121   d  of four types are arranged such that adjacent radiation elements are of types different from each other. However, the arrangement of the radiation elements  121  in the above-described antenna device  120  may be regarded as follows. 
       FIG. 13  is a diagram illustrating an arrangement of the plurality of radiation elements  121  in the antenna device  120  according to Modification 6. The antenna device  120  illustrated in  FIG. 13  is the same as the antenna device  120  illustrated in  FIG. 3  to  FIG. 7  described above. Accordingly, the arrangement itself of the radiation elements  121  illustrated in  FIG. 13  is the same as the arrangement illustrated in  FIG. 3  to  FIG. 7  described above. However, in Modification 6, the arrangement of the radiation elements  121  in the antenna device  120  is regarded as an arrangement pattern satisfying the following requirements 1 to 3. 
     (Requirement 1) A plurality of first element groups U 1  each including the four radiation elements  121  arranged in two rows and two columns are disposed in a zigzag manner in the column direction. The four radiation elements  121  included in each first element group U 1  include each one of the radiation elements  121   a  to  121   d  of four types. 
     (Requirement 2) Each of a plurality of second element groups U 2  includes the two radiation elements  121  arranged in one row and two columns and is disposed adjacent to corresponding one of the first element groups U 1  in the row direction. The two radiation elements  121  included in each of the second element groups U 2  include two types of the radiation elements  121  among the radiation elements  121   a  to  121   d  of four types. That is, one of the two radiation elements  121  included in each of the second element groups U 2  is an element of a type obtained by rotating the other by 90 degrees or 180 degrees. 
     (Requirement 3) Each of the two radiation elements  121  included in each of the second element groups U 2  is an element of a type obtained by rotating at least one of the radiation elements  121  in the first element group U 1 , both of which are adjacent to the two radiation elements  121 , by 90 degrees. 
     In Modification 6, the arrangement pattern of the radiation elements  121  in the antenna device  120  is regarded as an arrangement pattern satisfying the requirements 1 to 3 above. That is, in the case of the arrangement pattern satisfying the requirements 1 to 3 above, even when the plurality of radiation elements  121  are arranged in a matrix of three rows and four columns, it may be made simple to improve the axial ratio characteristics similarly to the embodiment described above. 
     As long as the arrangement pattern satisfies the requirements 1 to 3 above, it is sufficient that the number of columns is an even number when a plurality of radiation elements are arranged in a matrix, and the number of rows is not necessarily limited to a multiple of four. That is, when any even number of four or more is defined as K, the arrangement pattern satisfying the requirements 1 to 3 above may be applied to a circular polarization array antenna device that includes an element group including the plurality of radiation elements  121  arranged in a matrix of three rows and K columns. 
       FIG. 14  is a diagram illustrating the arrangement of the plurality of radiation elements  121  in an antenna device according to a comparative example. In the comparative example illustrated in  FIG. 14 , the plurality of radiation elements  121  are arranged in a matrix of three rows and six columns. Note that, in the comparative example illustrated in  FIG. 14 , three first element groups U 1 , each of which includes one set of the radiation elements  121   a  to  121   d  of four types, are linearly disposed in the column direction. This arrangement pattern does not satisfy the requirement 1 described above. 
       FIG. 15  is a diagram illustrating the arrangement of the plurality of radiation elements  121  in an antenna device  120 C according to Modification 6. In the antenna device  120 C, the plurality of radiation elements  121  are arranged in a matrix of three rows and six columns. 
     In the antenna device  120 C, three first element groups U 1 , each of which includes one set of the radiation elements  121   a  to  121   d  of four types, are disposed in a zigzag manner in the column direction. Accordingly, this arrangement pattern satisfies the requirement 1 described above. 
     Further, in the antenna device  120 C, three second element groups U 2 , each of which includes two types of the radiation elements  121  among the radiation elements  121   a  to  121   d  of four types, are disposed adjacent to the respective first element groups U 1  in the row direction. Accordingly, this arrangement pattern satisfies also the requirement 2 described above. 
     Further, in the antenna device  120 C, each of the two radiation elements  121  in each of the second element groups U 2  is an element of a type obtained by rotating at least one of the radiation elements  121  in the first element group U 1 , both of which are adjacent to the two radiation elements  121 , by 90 degrees. For example, the first type radiation element  121   a  disposed at (3×1) in the second element group U 2  is obtained by rotating clockwise the fourth type radiation element  121   d  disposed at (2×1) in the first element group U 1 , which is adjacent to the radiation element  121   a  at (3×1), by 90 degrees, and translating the rotated fourth type radiation element  121   d.  The second type radiation element  121   b  disposed at (3×2) in the second element group U 2  is obtained by rotating counterclockwise the third type radiation element  121   c  disposed at (2×2) in the first element group U 1 , which is adjacent to the radiation element  121   b  at (3×2), by 90 degrees, and translating the rotated third type radiation element  121   c.  Further, the second type radiation element  121   b  disposed at (3×2) in the second element group U 2  is obtained by rotating clockwise the first type radiation element  121   a  disposed at (2×3) in the first element group U 1 , which is adjacent to the radiation element  121   b  at (3×2), by 90 degrees, and translating the rotated first type radiation element  121   a.  Accordingly, this arrangement pattern satisfies also the requirement 3 described above. 
       FIG. 16  is a graph comparing the axial ratio characteristics of the antenna device according to the comparative example illustrated in  FIG. 14  with the axial ratio characteristics of the antenna device  120 C according to Modification 6 illustrated in  FIG. 15 . In  FIG. 16 , the axial ratio characteristics of the antenna device according to the comparative example are indicated by a dashed line, and the axial ratio characteristics of the antenna device  120 C according to Modification 6 are indicated by a solid line. From the difference in characteristics illustrated in  FIG. 16 , it is understood that the axial ratio characteristics are improved in the antenna device  120 C relative to in the comparative example. 
     As described above, by making the arrangement of the radiation elements  121  in the antenna device as the arrangement pattern satisfying the requirements 1 to 3 above, it may be made simple to improve the axial ratio characteristics similarly to the embodiment described above, even in the case that the plurality of radiation elements  121  are arranged in a matrix of odd-numbered rows and even-numbered columns. 
     Among the three requirements 1 to 3 described above, satisfying the requirements 1 and 2 makes it possible to expect the improving effect of the axial ratio characteristics, even in the case that the requirement 3 is not satisfied. 
     The “first element group U 1 ” and the “second element group U 2 ” according to Modification 6 may correspond to the “first element group” and the “second element group” of the present disclosure, respectively. 
     The features of the embodiment described above and Modification 1 to Modification 6 thereof can be appropriately combined with each other within a range that no contradiction occurs. 
     It should be understood that the embodiment disclosed herein is exemplary and non-restrictive in every respect. The scope of the present disclosure is indicated by the scope of claims rather than the description of the embodiment described above, and it is intended to include all modifications within the meaning and range of equivalency of the scope of claims.