Patent Publication Number: US-2021194126-A1

Title: Antenna module and communication apparatus equipped with the same

Description:
This is a continuation of U.S. Application Ser. No. 17/029,224 filed on Sep. 23, 2020 which is a continuation of International Application No. PCT/JP2019/011064 filed on Mar. 18, 2019 which claims priority from Japanese Patent Application No. 2018-070045 filed on Mar. 30, 2018. The contents of these applications are incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     Technical Field 
     The present disclosure relates to an antenna module and a communication apparatus equipped with the antenna module, and more particularly, to an impedance matching technique of an antenna module operating at a plurality of frequencies. 
     A technology in which a stub is provided on a transmission line for supplying radio frequency power to an antenna element to widen a frequency range of the antenna, has been well-known. 
     Japanese Unexamined Patent Application Publication No. 2002-271131 (Patent Document 1) discloses a configuration in which, by providing stubs of different shapes at substantially the same location on a transmission line of a patch antenna, a band width of a radio frequency signal that can be radiated by the patch antenna is widened. 
     Patent Document 1: Japanese Unexamined Patent Application Publication No. 2002-271131 
     BRIEF SUMMARY 
     In recent years, mobile terminals, such as smartphones have become popular, and in addition, electric household appliances, electronic devices, and the like having a wireless communication function have been increasing by technological innovations, such as IoT. This raises a concern that communication speeds and communication quality are lowered due to an increase in communication traffic of wireless networks. 
     As one of measures for solving such a problem, the fifth generation mobile communication system (5G) has been developed. In 5G, it is intended to achieve a large increase in communication speed and an improvement in communication quality by performing sophisticated beamforming and spatial multiplexing while using a large number of power supply elements, and by using, in addition to signals of 6-GHz band frequencies having been commonly used, signals of a millimeter wave band having higher frequencies (several tens of GHz). 
     In 5G, frequencies of a plurality of millimeter wave bands are used in some case, in which the frequency bands are separate from each other. In this case, it is suitable to transmit and receive signals of the plurality of frequency bands with one antenna. 
     A patch antenna disclosed in Patent Document 1 cited above is configured to match the impedance for a single frequency by using stubs, but does not consider matching the impedance for a plurality of frequency bands. 
     The present disclosure provides an antenna module able to appropriately match the impedance for a plurality of frequency bands. 
     An antenna module according to a certain aspect of the present disclosure includes a dielectric substrate having a multilayer structure, a power supply element and a ground electrode disposed in or on the dielectric substrate, a parasitic element disposed in a layer between the power supply element and the ground electrode, a first power supply wiring line, and a first stub and a second stub to be connected to the first power supply wiring line. The first power supply wiring line passes through the parasitic element, and supplies radio frequency power to the power supply element. The first stub is connected to a position different from a connection position of the second stub in the first power supply wiring line. 
     The first stub can be connected to the first power supply wiring line at a first position corresponding to a first frequency of a radio frequency signal radiated at the power supply element. The second stub can be connected to the first power supply wiring line at a second position corresponding to a second frequency of a radio frequency signal radiated at the parasitic element. 
     A distance from a connection position between the power supply element and the first power supply wiring line to the first position along the first power supply wiring line can be determined in accordance with the first frequency. A distance from a position where the first power supply wiring line passes through the parasitic element to the second position along the first power supply wiring line can be determined in accordance with the second frequency. 
     The first stub can have a line length corresponding to a wave length of a radio frequency signal radiated at the power supply element. The second stub can have a line length corresponding to a wave length of a radio frequency signal radiated at the parasitic element. 
     The antenna module can further include a power supply circuit mounted in or on the dielectric substrate and configured to supply radio frequency power to the power supply element. 
     The first stub and the second stub can be formed in a layer between the parasitic element and the ground electrode. 
     The first stub and the second stub can be formed in a layer between a mounting surface of the dielectric substrate and the ground electrode. 
     Each of the first stub and the second stub can be an open stub. 
     Each of the first stub and the second stub can be a short stub in which an end portion on an opposite side to an end portion connected to the first power supply wiring line is grounded. 
     The antenna module can further include a second power supply wiring line that passes through the parasitic element and supplies radio frequency power to the power supply element, and a third stub and a fourth stub to be connected to the second power supply wiring line. The third stub can be connected to a position different from a connection position of the fourth stub in the second power supply wiring line. 
     An antenna module according to another aspect of the present disclosure includes a dielectric substrate having a multilayer structure, a ground electrode disposed in or on the dielectric substrate, and a plurality of antennas including a first antenna and a second antenna. The first antenna and the second antenna are disposed adjacent to each other in the dielectric substrate. Each of the first antenna and the second antenna includes (i) a power supply element to be supplied with radio frequency power, (ii) a parasitic element disposed in a layer between the power supply element and the ground electrode, (iii) a first power supply wiring line and a second power supply wiring line that pass through the parasitic element and supply radio frequency power to the power supply element, (iv) a first stub and a second stub to be connected to the first power supply wiring line, and (v) a third stub and a fourth stub to be connected to the second power supply wiring line. The first stub is connected to a position different from a connection position of the second stub in the first power supply wiring line. The third stub is connected to a position different from a connection position of the fourth stub in the second power supply wiring line. Between the first antenna and the second antenna, there is formed at most one of the first power supply wiring line and the second power supply wiring line of any of the first antenna and the second antenna. 
     When the antenna module is seen in a plan view from a normal direction of the dielectric substrate, the first antenna can be disposed in a mode to be line-symmetrical to the second antenna. 
     When the antenna module is seen in a plan view from the normal direction of the dielectric substrate, the second antenna can be disposed adjacent to the first antenna in a mode of rotating the first antenna by 90 degrees. 
     An antenna module according to still another aspect of the present disclosure includes a dielectric substrate having a multilayer structure, a ground electrode disposed in or on the dielectric substrate, and a plurality of antennas. Each of the plurality of antennas includes (i) a power supply element to be supplied with radio frequency power, (ii) a parasitic element disposed in a layer between the power supply element and the ground electrode, (iii) a power supply wiring line that passes through the parasitic element and supplies radio frequency power to the power supply element, and (iv) two stubs connected at different positions along the power supply wiring line. The power supply wiring line and the stubs of each of the plurality of antennas do not overlap with the power supply wiring lines and the stubs of the other antennas when the antenna module is seen in a plan view. 
     A communication apparatus according to still another aspect of the present disclosure includes the antenna module according to any one of the above aspects. 
     In the antenna module of the present disclosure, the power supply element and the parasitic element are provided, and the power supply wiring line passes through the parasitic element and supplies radio frequency power to the power supply element. The first stub and the second stub are connected to different positions of the power supply wiring line. This makes it possible to appropriately match the impedance for a plurality of frequency bands. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a block diagram of a communication apparatus to which an antenna module according to an embodiment is applied. 
         FIG. 2  is a cross-sectional view of an antenna module according to an embodiment. 
         FIG. 3  is a perspective view illustrating a portion of a radiation element and a power supply wiring line of the antenna module in  FIG. 2 . 
         FIG. 4  is a diagram illustrating another example of a cross-sectional view of an antenna module according to an embodiment. 
         FIG. 5  is a perspective view illustrating a portion of a radiation element and a power supply wiring line of an antenna module according to Modification 1. 
         FIG. 6  is a perspective view illustrating a portion of a radiation element and a power supply wiring line of an antenna module according to Modification 2. 
         FIG. 7  is a diagram illustrating a first arrangement example of antennas in an antenna array. 
         FIG. 8  is a diagram illustrating a second arrangement example of antennas in an antenna array. 
         FIG. 9  is a diagram illustrating a third arrangement example of antennas in an antenna array. 
         FIG. 10  is a diagram illustrating a fourth arrangement example of antennas in an antenna array. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. Note that the same or corresponding constituent elements in the drawings are denoted by the same reference signs, and the description thereof will not be repeated. 
     Basic Configuration of Communication Apparatus 
       FIG. 1  is a block diagram of an example of a communication apparatus  10  to which an antenna module  100  according to Embodiment 1 is applied. The communication apparatus  10  is, for example, a mobile terminal, such as a cellular phone, a smartphone or a tablet, or a personal computer having a communication function. 
     Referring to  FIG. 1 , the communication apparatus  10  includes the antenna module  100  and a BBIC  200  constituting a baseband signal processing circuit. The antenna module  100  includes an RFIC  110 , which is an example of a power supply circuit, and an antenna array  120 . The communication apparatus  10  up-converts a signal transmitted from the BBIC  200  to the antenna module  100  into a radio frequency signal and radiates the radio frequency signal from the antenna array  120 , and down-converts a radio frequency signal received by the antenna array  120  and processes the down-converted signal in the BBIC  200 . 
     In  FIG. 1 , for ease of description, among a plurality of power supply elements  121  included in the antenna array  120 , only a configuration corresponding to four power supply elements  121  is illustrated, and a configuration corresponding to the other power supply elements  121  having the same configuration is omitted. In the present embodiment, a case where the power supply element  121  is a patch antenna having a rectangular flat plate shape will be described as an example. 
     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 synthesizer/demultiplexer  116 , a mixer  118 , and an amplification 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 side of the power amplifiers  112 AT to  112 DT, and the switch  117  is connected to a transmission-side amplifier of the amplification circuit  119 . When receiving a radio frequency signal, the switches  111 A to  111 D and  113 A to  113 D are switched to the side of the low-noise amplifiers  112 AR to  112 DR, and the switch  117  is connected to a reception-side amplifier of the amplification circuit  119 . 
     A signal transmitted from the BBIC  200  is amplified by the amplification circuit  119 , and then up-converted by the mixer  118 . A transmission signal, which is an up-converted radio frequency signal, is demultiplexed by the signal synthesizer/demultiplexer  116  into four signal waves; the demultiplexed signal waves pass through four signal paths, and are supplied to different power supply elements  121 , respectively. At this time, the directivity of the antenna array  120  may be adjusted by individually adjusting the phase shift degrees of the phase shifters  115 A to  115 D disposed in the respective signal paths. 
     Reception signals, each of which is a radio frequency signal received by each power supply element  121 , respectively pass through four different signal paths, and are multiplexed by the signal synthesizer/demultiplexer  116 . The multiplexed reception signal is down-converted by the mixer  118 , amplified by the amplification circuit  119 , and then transmitted to the BBIC  200 . 
     The RFIC  110  is formed as, for example, a one-chip integrated circuit component including the above-described circuit configuration. Alternatively, the devices (switches, power amplifiers, low-noise amplifiers, attenuators, and phase shifters) in the RFIC  110  corresponding to the power supply elements  121  may be formed as a one-chip integrated circuit component for each corresponding power supply element  121 . 
     Structure of Antenna Module 
     The structure of the antenna module  100  will be described with reference to  FIGS. 2 and 3 .  FIG. 2  is a cross-sectional view of the antenna module  100 . Referring to  FIG. 2 , the antenna module  100  includes, in addition to the power supply element  121  and the RFIC  110 , a dielectric substrate  130 , a ground electrode GND, a parasitic element  125 , and a power supply wiring line  140 . In  FIG. 2 , a case in which only one power supply element  121  is disposed will be described for ease of description, but a configuration in which the plurality of power supply elements  121  is disposed may be employed. In the following description, the power supply element  121  and the parasitic element  125  are also collectively referred to as a “radiation element”. 
       FIG. 3  is a perspective view for explaining positions of the radiation elements and the power supply wiring line  140 . In  FIG. 3 , for facilitating the understanding, only constituent elements including the power supply element  121 , the parasitic element  125 , the power supply wiring line  140 , and stubs  150  and  152 , which will be explained later, are described, and the description of the dielectric substrate  130  and the RFIC  110  is omitted. In the following description, a configuration including the radiation elements (the power supply element  121  and the parasitic element  125 ), the power supply wiring line  140 , and the stubs  150  and  152  illustrated in  FIG. 3  will also be referred to as an “antenna”. 
     The dielectric substrate  130  is, for example, a substrate in which resin, such as epoxy or polyimide is formed in a multilayer structure. The dielectric substrate  130  may be formed by using a liquid crystal polymer (LCP) having a lower dielectric constant or a fluorine-based resin. 
     The power supply element  121  is disposed on a first surface  132  of the dielectric substrate  130  or in an inner layer of the dielectric substrate  130 . The RFIC  110  is mounted on a second surface (mounting surface)  134  on a side opposite to the first surface  132  of the dielectric substrate  130  via a connection electrode, such as a solder bump (not illustrated). The ground electrode GND is disposed between the layer where the power supply element  121  is disposed and the second surface  134  in the dielectric substrate  130 . 
     The parasitic element  125  is disposed in a layer between the power supply element  121  and the ground electrode GND of the dielectric substrate  130  in such a manner as to face the power supply element  121 . The size of the parasitic element  125  (the area of a radiation surface) is larger than the size of the power supply element  121 , and the overall power supply element  121  is so disposed as to overlap with the parasitic element  125  when the antenna module  100  is seen in a plan view from the normal direction of the first surface  132  of the dielectric substrate  130 . 
     Resonant frequencies of the power supply element  121  and the parasitic element  125  are generally determined by the size of each element. In general, as the element size is large, the resonant frequency tends to be lower, while as the element size is smaller, the resonant frequency tends to be higher. The size of the power supply element  121  and the size of the parasitic element  125  are determined in accordance with the frequency of a radio frequency signal to be transmitted by the antenna module. 
     The power supply wiring line  140  extends from the RFIC  110  and passes through the ground electrode GND and the parasitic element  125 , so as to be connected to the power supply element  121 . More specifically, as illustrated in  FIG. 3 , the power supply wiring line  140  extends upward from the RFIC  110  to a layer between the ground electrode GND and the parasitic element  125  by a via  141 , is offset by a wiring pattern  142  to a position under the parasitic element  125  in the layer, and further extends upward therefrom to a power supply point SP 1  of the power supply element  121  while passing through the parasitic element  125  by a via  143 . The power supply wiring line  140  supplies the radio frequency power from the RFIC  110  to the power supply element  121 . As described above, the power supply wiring line  140  having reached the layer between the ground electrode GND and the parasitic element  125  bends to extend in a direction toward the center of the power supply element  121 , and further bends at the position immediately under the power supply point SP 1  of the power supply element  121  to extend in a direction toward the first surface  132  of the dielectric substrate  130 , so as to connect to the power supply element  121  while passing through the parasitic element  125 . 
     The stubs  150  and  152  are connected to the power supply wiring line  140  at different positions thereof. The stub  150  and the stub  152  extend in opposite directions to each other with the wiring pattern  142  of the power supply wiring line  140  interposed therebetween. 
     The stubs  150  and  152  are provided to adjust the impedance at resonant frequencies of the power supply element  121  and the parasitic element  125 , respectively. Therefore, a line length L 1  of the stub  150  is determined in accordance with the wave length of the radio frequency signal radiated from the power supply element  121 , and a line length L 2  of the stub  152  is determined in accordance with the wave length of the radio frequency signal radiated from the parasitic element  125 . Each of the stubs  150  and  152  also has a function, along with the above-described impedance adjustment function, as a band pass filter configured to allow a signal in a frequency band wider than a target frequency band to pass therethrough. Therefore, the line length L 1  of the stub  150  corresponding to the power supply element  121  configured to radiate a signal on a relatively high frequency side is set to a dimension longer than a quarter of a wave length λ1 of the radio frequency signal radiated from the power supply element  121 . On the other hand, the line length L 2  of the stub  152  corresponding to the parasitic element  125  configured to radiate a signal on a relatively low frequency side is set to a dimension shorter than a quarter of a wave length λ2 of the radio frequency signal radiated from the parasitic element  125 . Each of the stubs  150  and  152  may not be formed with a constant line width, and the line width may be changed midway in the stub. 
     The stub  150  is connected to the power supply wiring line  140  at a position P 1  (first position) corresponding to a frequency f 1  of the radio frequency signal radiated from the power supply element  121 . The stub  152  is connected to the power supply wiring line  140  at a position P 2  (second position) corresponding to the frequency of the radio frequency signal radiated from the parasitic element  125 . More specifically, a distance D 1  from a connection position between the power supply element  121  and the power supply wiring line  140  (that is, the power supply point SP 1 ) to the connection position P 1  of the stub  150  along the power supply wiring line  140  is determined in accordance with the frequency f 1  of the radio frequency signal radiated from the power supply element  121 . A distance D 2  from a position (SP 2 ), at which the power supply wiring line  140  passes through the parasitic element  125 , to the connection position P 2  of the stub  152  along the power supply wiring line  140  is determined in accordance with a frequency f 2  of the radio frequency signal radiated from the parasitic element  125 . For example, the distance D 1  is one third of the wave length λ1 of the radio frequency signal, and the distance D 2  is one thirtieth of the wave length λ2 of the radio frequency signal. 
     As described above, in the antenna module  100  according to the present embodiment, the stubs respectively corresponding to the power supply element  121  and the parasitic element  125  are provided at the positions on the power supply wiring line  140  corresponding to the radio frequency signals radiated from the respective elements. By doing so, it is possible to individually adjust the impedance for each frequency band of the elements. 
     In the antenna module  100  illustrated in  FIG. 2 , an example in which the stubs  150  and  152  are formed in the layer between the parasitic element  125  and the ground electrode GND is described. However, the layer in which the stubs are formed in a layer between the ground electrode GND and the RFIC  110  as in the antenna module  100  #illustrated in  FIG. 4 . 
     Modification 1 
     In the above-described embodiment, an example of the configuration has been described in which a radio frequency signal of one polarized wave is radiated from each of the power supply element  121  and the parasitic element  125 . 
     In Modification 1, an example in which radio frequency signals radiated from each element are two polarized waves will be described. 
       FIG. 5  is a perspective view illustrating a portion of a radiation element and a power supply wiring line of an antenna module  100 A according to Modification 1. The antenna module  100 A of  FIG. 5  includes, in addition to the power supply wiring line  140  in  FIG. 4 , a power supply wiring line  140 A configured to supply a radio frequency signal of another polarized wave. 
     Similarly to the power supply wiring line  140 , the power supply wiring line  140 A extends upward from the RFIC  110  to a layer between the ground electrode GND and the parasitic element  125  by a via  141 A, is offset by a wiring pattern  142 A to a position under the parasitic element  125  in the layer, and further extends upward therefrom to a power supply point SP 1 A of the power supply element  121  while passing through the parasitic element  125  by a via  143 A. 
     The power supply point SP 1 A is disposed at a position where the power supply point SP 1  is rotated by 90 degrees with respect to an intersection point C 1  of the diagonal lines of the power supply element  121 . 
     Stubs  150 A and  152 A are connected to the power supply wiring line  140 A at different positions thereof. The stub  150 A and the stub  152 A extend in opposite directions to each other with the wiring pattern  142 A of the power supply wiring line  140 A interposed therebetween. The line length of the stub  150 A and the connection position thereof in the power supply wiring line  140 A are determined in accordance with the frequency f 1  and the wave length λ1 of the radio frequency signal radiated from the power supply element  121 . The line length of the stub  152 A and the connection position thereof in the power supply wiring line  140 A are determined in accordance with the frequency f 2  and the wave length λ2 of the radio frequency signal radiated from the parasitic element  125 . 
     As described above, as for the antenna module of the two-polarized-wave type as well, in each of the power supply wiring lines, the stubs respectively corresponding to the power supply element and the parasitic element are provided at the positions corresponding to the radio frequency signals to be radiated. By doing so, it is possible to individually adjust the impedance for each frequency band of the elements, with respect to each polarized wave of the radio frequency signals. 
     Modification 2 
     In Modification 1, an example has been described in which the stubs connected to each power supply wiring line are an open stub where an end portion on the opposite side to an end portion connected to the power supply wiring line is open. 
     In Modification 2, an example in which stubs connected to each power supply wiring line are a short stub will be described. 
       FIG. 6  is a perspective view illustrating a portion of a radiation element and a power supply wiring line of an antenna module  100 B according to Modification 2. In the antenna module  100 B of  FIG. 6 , in each stub connected to the power supply wiring line  140  or  140 A, an end portion of the stub on the opposite side to an end portion thereof connected to the power supply wiring line is connected to the ground electrode GND by a via. As a result, each stub serves as a short stub. 
     As described above, when the stubs connected to the power supply wiring line are set as short stubs, static electricity charged in the antenna flows to the ground electrode GND. Thus, an electronic device, such as an RFIC, connected to the power supply wiring line may be protected from electrostatic discharge (ESD) caused by the stub. 
     The antenna module  100 B in  FIG. 6  has a configuration in which each stub is a short stub in the case of two polarized waves, but a short stub may also be used for the one-polarized-wave type antenna module as illustrated in  FIG. 2 or 4 . 
     Antenna Arrangement in Antenna Array 
     As described in  FIG. 1 , in the antenna module, the antenna array  120  in which a plurality of antennas is two-dimensionally arranged is formed. 
     As described above, when the stubs are formed on the wiring pattern of the power supply wiring line, the power supply wiring line is so formed as to protrude to an outer side portion relative to the radiation elements (the power supply element  121  and the parasitic element  125 ) of the antenna. As a result, the power supply wiring lines are formed between the antennas adjacent to each other, and when the antenna array  120  is seen in a plan view, the power supply wiring line and/or the stub of one of the antennas overlaps with the power supply wiring line and/or the stub of the other one of the antennas in some case. 
     When the power supply wiring lines and/or the stubs of the adjacent antennas overlap with each other as described above, there arises a risk that mutual electromagnetic coupling occurs and causes noise or the like. 
     In particular, in the two-polarized-wave type antennas as described in Modifications 1 and 2, there are included two power supply wiring lines and four stubs. Accordingly, the overlapping of the power supply wiring lines and the stubs is likely to occur unless the antennas are appropriately arranged. 
     In  FIGS. 7 to 10  given below, arrangement examples in which power supply wiring lines and stubs of adjacent antennas do not overlap with each other will be described while exemplifying a case of an antenna array that includes eight two-polarized-wave type antennas in the form of two by four. For ease of description, in each of the drawings of  FIGS. 7 to 10 , antennas on the upper stage are denoted by reference signs, such as  160 - 11 ,  160 - 12 ,  160 - 13 , and  160 - 14  from the left, while antennas on the lower stage are denoted by reference signs, such as  160 - 21 ,  160 - 22 ,  160 - 23 , and  160 - 24  from the left. 
     Arrangement Example 1 
       FIG. 7  is a diagram illustrating an arrangement example of antennas  160  in an antenna array  120 . In each antenna  160  in  FIG. 7 , two power supply wiring lines  140  and  140 A are formed to extend in directions orthogonal to each other as illustrated in  FIG. 5 . As a result, all the antennas  160  are arranged facing the same direction. More specifically, the power supply wiring line  140  is formed to extend in the negative direction of an X-axis from the power supply element  121 , and the power supply wiring line  140 A is formed to extend in the positive direction of a Y-axis from the power supply element  121 . 
     In this arrangement example, between two antennas adjacent to each other in the X-axis direction, only the power supply wiring line  140  of one of the adjacent antennas is formed. Between two antennas adjacent to each other in the Y-axis direction, only the power supply wiring line  140 A of one of the adjacent antennas is formed. Accordingly, when the antenna array  120  is seen in a plan view, between two antennas adjacent to each other, none of the power supply wiring lines and the stubs thereof overlap each other. 
     Arrangement Example 2 
       FIG. 8  is a diagram illustrating an arrangement example of antennas  160 A in an antenna array  120 A. In each antenna  160 A in  FIG. 8 , two power supply wiring lines  140  and  140 B are formed to extend in opposite directions to each other. More specifically, in each of the antennas  160 A- 11 ,  13 ,  22 , and  24 , the power supply wiring line  140  is formed to extend in the negative direction of the Y-axis from the power supply element  121 , and the power supply wiring line  140 B is formed to extend in the positive direction of the Y-axis from the power supply element  121 . 
     On the other hand, the arrangement of each of the antennas  160 A- 12 ,  14 ,  21 , and  23  is such that the arrangement of each of the antennas  160 A- 11 ,  13 ,  22 , and  24  is rotated by 90 degrees, and the power supply wiring line  140  is formed to extend in the negative direction of the X axis from the power supply element  121  while the power supply wiring line  140 B is formed to extend in the positive direction of the X axis from the power supply element  121 . 
     In this arrangement example, between two antennas adjacent to each other in the X-axis direction and between two antennas adjacent to each other in the Y-axis direction, only the power supply wiring line  140  or  140 B of one of the adjacent antennas is formed. Accordingly, when the antenna array  120 A is seen in a plan view, between two antennas adjacent to each other, none of the power supply wiring lines and the stubs thereof overlap each other. 
     Arrangement Example 3 
       FIG. 9  is a diagram illustrating an arrangement example of antennas  160 B in an antenna array  120 B. In the antenna array  120 B in  FIG. 9 , the antennas  160 B are arranged line-symmetrically with respect to a line LN, which is parallel to the Y-axis and passes through between two antennas (for example, the antenna  160 B- 12  and the antenna  160 B- 13 ) arranged in a central portion of the antennas  160 B aligned in the X-axis direction. 
     More specifically, similarly to  FIG. 7 , in each of the antennas  160 B- 11 ,  12 ,  21 , and  22 , the power supply wiring line  140  is formed to extend in the negative direction of the X-axis from the power supply element  121 , and the power supply wiring line  140 A is formed to extend in the positive direction of the Y-axis from the power supply element  121 . 
     On the other hand, in each of the antennas  160 B- 13 ,  14 ,  23 , and  24 , the power supply wiring line  140  is formed to extend in the positive direction of the X-axis from the power supply element  121 , and the power supply wiring line  140 A is formed to extend in the positive direction of the Y-axis from the power supply element  121 . 
     In this arrangement example, except for an area between two antennas in the central portion (between the antenna  160 B- 12  and the antenna  160 B- 13  and between the antenna  160 B- 22  and the antenna  160 B- 23 ), between two antennas adjacent to each other in the X-axis direction, only the power supply wiring line  140  of one of the adjacent antennas is formed, and between two antennas adjacent to each other in the Y-axis direction, only the power supply wiring line  140 A of one of the adjacent antennas is formed. Accordingly, when the antenna array  120 B is seen in a plan view, between two antennas adjacent to each other, none of the power supply wiring lines and the stubs thereof overlap each other. 
     By line-symmetrically arranging the antennas in the antenna array as in Arrangement Example 3 described above, it is possible to cause the radiated polarized waves to have symmetric characteristics. 
     Alternatively or additionally, the upper-stage antennas and the lower-stage antennas may be arranged line-symmetrically with respect to a line parallel to the X-axis. 
     Arrangement Example 4 
       FIG. 10  is a diagram illustrating an arrangement example of antennas  160 C in an antenna array  120 C. In the antenna array  120 C in  FIG. 10 , the antennas  160 C are arranged in such a manner that two adjacent antennas aligned in the X-axis direction are rotated by 90 degrees relative to each other. 
     More specifically, in each of the antennas  160 C- 11  and  21 , the power supply wiring line  140  is formed to extend in the negative direction of the Y-axis from the power supply element  121 , and the power supply wiring line  140 A is formed to extend in the negative direction of the X-axis from the power supply element  121 . In each of the antennas  160 C- 12  and  22 , the power supply wiring line  140  is formed to extend in the negative direction of the X-axis from the power supply element  121 , and the power supply wiring line  140 A is formed to extend in the positive direction of the Y-axis from the power supply element  121 . 
     In each of the antennas  160 C- 13  and  23 , the power supply wiring line  140  is formed to extend in the positive direction of the Y-axis from the power supply element  121 , and the power supply wiring line  140 A is formed to extend in the positive direction of the X-axis from the power supply element  121 . In each of the antennas  160 C- 14  and  24 , the power supply wiring line  140  is formed to extend in the positive direction of the X-axis from the power supply element  121 , and the power supply wiring line  140 A is formed to extend in the negative direction of the Y-axis from the power supply element  121 . 
     In this arrangement example as well, between two antennas adjacent to each other in the X-axis direction and between two antennas adjacent to each other in the Y-axis direction, at most only one of the power supply wiring lines of one of the adjacent antennas is formed. Accordingly, when the antenna array  120 C is seen in a plan view, between two antennas adjacent to each other, none of the power supply wiring lines and the stubs thereof overlap each other. 
     The arrangement examples illustrated in  FIGS. 7 to 10  are merely examples, and other arrangements may also be employed in which power supply wiring lines and stubs do not overlap with each other between adjacent antennas. Further, the number of antennas to be aligned and the formation positions of the power supply wiring lines in each antenna may be different from those described above. 
     In the antenna module, the number of ground electrodes may not be limited to one; for example, another ground electrode disposed in a layer closer to the stub may be disposed only at a position overlapping with the stub. According to this configuration, since it is possible to reduce the line width of the stub, the overall antenna module may be reduced in size. Furthermore, according to this configuration, since the coupling amount between the stub and the ground electrode can be adjusted, when the stub functions as a band pass filter, it is possible to adjust the characteristics of the band pass filter. 
     In the above description, an example of a case where the number of parasitic elements through which the power supply wiring line passes is one has been discussed. However, the number of parasitic elements is not limited thereto, and a configuration in which two or more parasitic elements are disposed may also be employed. Note that, as in the above-described embodiment, in the case where the radio frequency signals of different frequency bands are radiated from the power supply element and the parasitic element by using the respective power supply wiring lines, it is desirable that the number of parasitic elements through which the power supply wiring lines pass is one. 
     It is to be considered that the embodiment disclosed herein is illustrative in all respects and is not restrictive. The scope of the present disclosure is indicated by the claims rather than the description of the above-described embodiment, and it is intended to include all modifications within the meaning and scope equivalent to the claims. 
     REFERENCE SIGNS LIST 
       10  COMMUNICATION APPARATUS 
       100 ,  100 A,  100 B ANTENNA MODULE 
       111 A to  111 D,  113 A to  113 D,  117  SWITCH 
       112 AR to  112 DR LOW-NOISE AMPLIFIER 
       112 AT to  112 DT POWER AMPLIFIER 
       114 A to  114 D ATTENUATOR 
       115 A to  115 D PHASE SHIFTER 
       116  SIGNAL SYNTHESIZER/DEMULTIPLEXER 
       118  MIXER 
       119  AMPLIFICATION CIRCUIT 
       120 ,  120 A to  120 C ANTENNA ARRAY 
       121  POWER SUPPLY ELEMENT 
       125  PARASITIC ELEMENT 
       130  DIELECTRIC SUBSTRATE 
       132 ,  134  SURFACE 
       140 ,  140 A,  140 B POWER SUPPLY WIRING LINE 
       141 ,  141 A,  143 ,  143 A VIA 
       142 ,  142 A WIRING PATTERN 
       150 ,  150 A,  152 ,  152 A STUB 
       160 ,  160 A to  160 C ANTENNA GND GROUND ELECTRODE 
     SP 1 A, SP 1  POWER SUPPLY POINT