Abstract:
An antenna device includes a first dielectric having a plate-like shape that has a first surface and a second surface, the first surface opposing the second surface; a second dielectric having a plate-like shape, the second dielectric rising from the second surface, the second dielectric forming a T-shaped configuration with the first dielectric, the second dielectric having a distal end opposing the second surface; and an antenna arranged on the distal end, the antenna being configured to radiate a millimeter wave having an electric field changing in a thickness direction of the second dielectric, wherein wireless communication is performed through the first surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2015-163832, filed on Aug. 21, 2015, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The embodiments discussed herein are related to an antenna device and a communication module. 
       BACKGROUND 
       [0003]    To date, an electronic apparatus including a housing having a first surface and an induced electric field antenna has been provided. The induced electric field antenna is disposed in the housing and includes a coupling electrode disposed opposite to a first area in the first surface. The electronic apparatus further includes a millimeter wave antenna which is disposed in the housing on the opposite side of the first area with respect to the induced electric field antenna and includes a plurality of millimeter wave antenna elements which are disposed at an outer side than the outer edge of the bottom of the induced electric field antenna such that a neighboring space of the first area is included in a cover area of the millimeter wave antenna. The electronic apparatus further includes a proximity wireless communication unit which is disposed in the housing, and transmits and receives a radio signal having a first frequency band through the induced electric field antenna, and transmits and receives a radio signal having a higher millimeter wave band than the first frequency band through the millimeter wave antenna. For example, refer to Japanese Laid-open Patent Publication No. 2012-090228. 
       SUMMARY 
       [0004]    According to an aspect of the invention, an antenna device includes a first dielectric having a plate-like shape that has a first surface and a second surface, the first surface opposing the second surface; a second dielectric having a plate-like shape, the second dielectric rising from the second surface, the second dielectric forming a T-shaped configuration with the first dielectric, the second dielectric having a distal end opposing the second surface; and an antenna arranged on the distal end, the antenna radiating a millimeter wave having an electric field changing in a thickness direction of the second dielectric, wherein wireless communication is performed through the first surface. 
         [0005]    The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
         [0006]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0007]      FIG. 1  is a diagram illustrating an electronic apparatus including an antenna device; 
           [0008]      FIG. 2  is a perspective view illustrating the antenna device; 
           [0009]      FIG. 3  is a cross-sectional view taken along line A 1 -A 2  of  FIG. 2 ; 
           [0010]      FIG. 4  is a cross-sectional view taken along line B 1 -B 2  of  FIG. 2 ; 
           [0011]      FIG. 5  is a plan view illustrating an antenna included in the antenna device; 
           [0012]      FIG. 6  is a diagram illustrating a direction of an electric field of a millimeter wave that leaks outside a plate; 
           [0013]      FIG. 7  is a diagram illustrating a direction of an electric field of a millimeter wave that leaks outside a plate; 
           [0014]      FIG. 8  is a diagram illustrating distribution of the S 21  parameter of the antenna device; 
           [0015]      FIG. 9  is a diagram illustrating distribution of the S 21  parameter by a comparative antenna device; 
           [0016]      FIG. 10  is a diagram illustrating distribution of the S 21  parameter by a comparative antenna device; 
           [0017]      FIGS. 11A, 11B, and 11C  are diagrams illustrating a dipole antenna, a slot antenna and a loop antenna, respectively; 
           [0018]      FIG. 12  is a cross-sectional view illustrating an antenna device according to a first variation of a first embodiment; 
           [0019]      FIG. 13  is a cross-sectional view illustrating an antenna device according to a second variation of the first embodiment; 
           [0020]      FIG. 14  is a cross-sectional view illustrating an antenna device according to a third variation of the first embodiment; and 
           [0021]      FIG. 15  is a cross-sectional view illustrating a communication module including an antenna device according to a fourth variation of the first embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0022]    A millimeter wave antenna in the related-art electronic apparatus includes a plurality of millimeter wave antenna elements. This is because the millimeter wave antenna elements have high straightness and narrow communication possible areas, and thus this is for the purpose of expanding a communication possible area. 
         [0023]    However, when a plurality of millimeter wave antenna elements are used, power consumption becomes high. 
         [0024]    Accordingly, there is a problem in that the millimeter wave antenna in the related-art electronic apparatus has high power consumption. 
         [0025]    Thus it is desirable to provide an antenna device and a communication module that have a secure communication possible area with reduced power consumption. 
         [0026]    In the following, a description will be given of embodiments to which an antenna device and a communication module according to the present disclosure is applied. 
       Embodiments 
       [0027]      FIG. 1  is a diagram illustrating an electronic apparatus  10  including an antenna device  100 . The electronic apparatus  10  is a notebook-sized personal computer (PC). 
         [0028]    The electronic apparatus  10  includes a keyboard  11 , a touch pad  12 , a housing  13 , a display panel  14 , a housing  15 , and the antenna device  100 . 
         [0029]    The keyboard  11 , the touch pad  12 , and the antenna device  100  are disposed on the housing  13 . The antenna device  100  is disposed on the side of the touch pad  12  on the housing  13 . The display panel  14  is disposed on the housing  15 . 
         [0030]    The antenna device  100  is a communication device that performs near field wireless communication using a millimeter wave. The antenna device  100  is disposed on the housing  13  such that a radiation surface  101  is exposed from an opening  13 B of a surface  13 A of the housing  13 , and radiates a millimeter wave from the radiation surface  101 . The parts other than the radiation surface  101  of the antenna device  100  are contained inside the housing  13 , and thus the parts are not viewed from the outside of the electronic apparatus  10 . 
         [0031]    Here, a description will be given of a configuration in which the antenna device  100  transfers data with a smartphone terminal, on which an antenna device capable of communicating with the antenna device  100  is mounted, by near field wireless communication as an example. 
         [0032]    In this regard, a near field mentioned here represents a distance within a few millimeters from the surface  13 A as an example, and the smartphone terminal may contact the surface  13 A. Also, near field wireless communication may be referred to as proximity wireless communication. 
         [0033]    Also, in the following, a description will be given of a configuration in which the antenna device  100  radiates a millimeter wave from the radiation surface  101 . However, it is possible for the antenna device  100  to receive a millimeter wave from another communication device disposed in the vicinity of the radiation surface  101 . 
         [0034]    Next, a description will be given of the antenna device  100  with reference to  FIGS. 2 to 5 . 
         [0035]      FIG. 2  is a perspective view illustrating the antenna device  100 .  FIG. 3  is a cross-sectional view taken along line III-III of  FIG. 2 .  FIG. 4  is a cross-sectional view taken along line IV-IV of  FIG. 2 .  FIG. 5  is a plan view illustrating an antenna  120  included in the antenna device  100 . In this regard, in the following, a description will be given using an XYZ coordinate system, which is an orthogonal coordinate system. 
         [0036]    The antenna device  100  includes a radiation plate  110 , an antenna  120 , and a substrate  130 . 
         [0037]    The radiation plate  110  includes plates  111  and  112 , and has a T-shaped configuration as viewed from the Y-axis direction. 
         [0038]    The plate  111  is a plate-like member parallel to an XY plane, and is made of a dielectric material. The plate  111  is an example of a first dielectric. The thickness of the plate  111  is preferably as thick as having a small loss when the plate  111  functions as a waveguide. The thickness of the plate  111  is 2 mm as an example. 
         [0039]    A surface  111 A of the plate  111  on the positive direction side of the Z-axis is a radiation surface from which the antenna device  100  radiates a millimeter wave, and is the radiation surface  101  illustrated in  FIG. 1 . 
         [0040]    An end part of the plate  112  on the positive direction side of the Z-axis is connected to a surface  111 B of the plate  111  on the negative direction side. In other words, the plate  112  vertically protrudes from the surface  111 B of the plate  111  in the negative direction of the Z-axis. 
         [0041]    The plate  112  is a plate-like member parallel to the YZ plane, and is made of a dielectric material. The relative dielectric constant of the plate  112  is equal to the relative dielectric constant of the plate  111 . The plate  112  is an example of a second dielectric. The plate  112  rises from the surface  111 B of the plate  111  in the negative direction of the Z-axis. The thickness of the plate  112  is preferably as thick as having a small loss when the plate  112  functions as a waveguide, and may be the same as the thickness of the plate  111 . The thickness of the plate  112  is 2 mm as an example. 
         [0042]    The plate  112  protrudes from the center in the X-axis direction of the plate  111  toward the negative direction of the Z-axis side. The length of the plate  112  in the Y-axis direction is equal to the length of the plate  111  in the Y-axis direction. The end part on the negative direction of the Z-axis side of the plate  112  comes in contact with the antenna  120 . The plate  112  is integrally formed with the plate  111 . 
         [0043]    The antenna  120  is disposed on the surface  130 A on the positive direction side of the Z-axis of the substrate  130 . The end part on the negative side of the Z-axis of the plate  112  comes in contact with the positive direction side of the Z-axis of the antenna  120 . 
         [0044]    The antenna  120  is an antenna that radiates, in the Z-axis direction, a millimeter wave having an electric field changing in the X-axis direction. Here, the antenna  120  is a patch antenna, for example. As illustrated in  FIG. 5 , the antenna  120  built as a patch antenna is square-shaped in an XY planar view, two sides out of the four sides of the square are parallel to the X-axis, and the remaining two sides are parallel to the Y-axis. The length of one side of the patch antenna  120  is 1.5 mm as an example. 
         [0045]    The antenna  120  falls in the width of the X-axis direction of the plate  112  in the X-axis direction, and also falls in the width of the Y-axis direction of the plate  112  in the Y-axis direction. 
         [0046]    A feed point  121  (refer to  FIG. 5 ) of the antenna  120  is disposed at the center in the Y-axis direction at the end part in the negative direction side of the X-axis or at the left end of the antenna  120 . The core wire of a coaxial cable, not illustrated in  FIG. 5 , is coupled to the feed point  121 , and is supplied with a high frequency power in order to achieve a millimeter wave. The high frequency power that achieves a millimeter wave is 60 GHz, as an example. 
         [0047]    The antenna  120  is supplied with power at the feed point  121  so as to radiate, in the Z-axis direction, a millimeter wave having an electric field that changes in the X-axis direction. The length of each of the four sides of the patch antenna used as the antenna  120  is a half of the wavelength (a half wavelength) in electrical length of the millimeter wave. 
         [0048]    The antenna  120  is disposed on the surface  130 A on the positive direction of the Z-axis side of the substrate  130 . The substrate  130  is a substrate included in the housing  13  of the electronic apparatus  10  illustrated in  FIG. 1 , for example. The substrate  130  may be a substrate conforming to the standard for the Flame Retardant type 4 (FR4), for example. In this case, the antenna  120  may be formed by patterning a metal layer, such as a copper foil or the like disposed on the surface of the substrate  130 . Also, an electronic component chip, or the like may be mounted on the substrate  130 . 
         [0049]    Also, the substrate  130  may be a part of the internal structure of the housing  13 , for example, or may be a specialized member for disposing the antenna  120  thereon. 
         [0050]    In the antenna device  100  having the above configuration, the radiation plate  110  functions as a T-shaped waveguide to guide, to the surface  111 A, the millimeter wave generated and radiated by the antenna  120  in the positive direction of the Z-axis. 
         [0051]    The millimeter wave radiated by the antenna  120  in the positive direction of the Z-axis is a linearly-polarized electromagnetic wave having an electric field changing in the X-axis direction, and the radiated millimeter wave enters the plate  112  from the end part on the negative direction side of the Z-axis of the plate  112 . The antenna  120  is aligned with the end part on the negative side of the Z-axis of the plate  112  or the lower end of the plate  112  so as to fall in the X-axis direction width and the Y-axis direction width of the plate  112 , and thus the millimeter wave radiated from the antenna  120  in the positive direction of the Z-axis enters the plate  112 . 
         [0052]    The electric field of the millimeter wave changes in the thickness direction (the X-axis direction) of the plate  112 , and thus the millimeter wave is propagated in the positive direction of the Z-axis while being reflected in the plate  112 . In this regard, a part of the millimeter wave leaks outside the plate  112 . 
         [0053]    When the millimeter wave approaches a joining part of the plate  112  and the plate  111 , the plate  112  and the plate  111  function like a T-shaped waveguide, the millimeter wave is propagated inside the plate  111  in a stretching direction of the XY plane. The electric field of the millimeter wave changes in the Z-axis direction inside the plate  111 . 
         [0054]    The millimeter wave is reflected at the end parts of the plate  111  inside the plate  111 . Accordingly, the millimeter wave is propagated in various directions so that the XY plane stretches inside the plate  111 . Also, at this time, a part of the millimeter wave leaks outside the plate  111 . 
         [0055]    Here, a description will be given of the direction of the electric field of the millimeter wave that leaks outside the plate  111  with reference to  FIG. 6  and  FIG. 7 . 
         [0056]      FIG. 6  and  FIG. 7  are diagrams illustrating a direction of an electric field of a millimeter wave that leaks outside the plate  111 . In  FIG. 6  and  FIG. 7 , a direction of the electric field of the millimeter wave is indicated by an arrow.  FIG. 6  illustrates a cross-sectional view taken along line III-III in the same manner as  FIG. 3 .  FIG. 7  illustrates a cross-sectional view taken along line IV-IV in the same manner as  FIG. 4 . 
         [0057]    Also, in  FIG. 6  and  FIG. 7 , a smartphone terminal  20  is illustrated. The smartphone terminal  20  includes an antenna device  21  capable of communicating with the antenna device  100 . 
         [0058]    As illustrated in  FIG. 6  and  FIG. 7 , the electric field of the millimeter wave that is propagated inside the plate  112  changes in the Z-axis direction as illustrated by an arrow C. The electric field of the millimeter wave that is propagated inside the plate  111  changes in the Z-axis direction as illustrated by an arrow A. Also, the electric field of the millimeter wave that leaks from the plate  111  in the positive direction and the negative direction of the Z-axis is folded back at the positions within a few millimeters from the surface  111 A of the plate  111  as illustrated by an arrow B. 
         [0059]    In this manner, when the electric field is folded back, a component Bx (refer to  FIG. 6 ) in the X-axis direction and a component By (refer to  FIG. 7 ) in the Y-axis direction occur. 
         [0060]    Here, only the component Bx (refer to  FIG. 6 ) in the X-axis direction and the component By (refer to  FIG. 7 ) in the Y-axis direction are illustrated. However, the millimeter wave is propagated in various directions in the XY plane inside the plate  111 , and thus when the millimeter waves that have leaked outside the plate  111  are folded back, the components that are parallel to the XY plane in various directions occur. 
         [0061]    In this manner, the components of the electric field that are parallel to the XY plane occur in an area within a few millimeters from the surface  111 A of the plate  111 . 
         [0062]    Accordingly, it is possible to perform near field wireless communication between the antenna device  100  and the antenna device  21  which is capable of receiving the electric field components that are parallel to the XY plane, such as the components Bx and By. 
         [0063]    In this regard, as the antenna device  21 , it is possible to use various kinds of antennas, for example, a patch antenna, a dipole antenna, a monopole antenna, a slot antenna, or the like. 
         [0064]    Here, a description will be given of a result of simulation with reference to  FIG. 8  to  FIG. 10 . 
         [0065]      FIG. 8  is a diagram illustrating distribution of the S 21  parameter of the antenna device  100 .  FIG. 8  illustrates an XY plane view of the plate  111  and the antenna  120 . The length of the plate  111  in the X-axis direction is 90 mm, and the length in the Y-axis direction is 50 mm. 
         [0066]    The origin P 0  (0, 0) of the XY coordinates were defined as illustrated in  FIG. 8 , and the values of the S 21  parameters of the electric field in the X-axis direction and the Y-axis direction were obtained by simulation at a point P 1  (45, 25), a point P 2  (90, 25), a point P 3  (45, 0), a point P 4  (90, 0) on the surface  111 A (refer to  FIG. 2 ) of the plate  111 . The simulated values of the S 21  parameter in the X-axis and Y-axis directions at each point are indicated respectively X and Y as illustrated in  FIG. 8 . 
         [0067]    The center of the antenna  120  is positioned just under the point P 1  (45, 25). 
         [0068]    As a result, the S 21  parameter in the X-axis direction at the point P 1 (45, 25) was calculated as −30.15 dB, and the S 21  parameter of the electric field in the Y-axis direction was calculated as −48.35 dB. 
         [0069]    Also, the S 21  parameter in the X-axis direction at the point P 2 (90, 25) was calculated as −38.79 dB, and the S 21  parameter of the electric field in the Y-axis direction was calculated as −47.42 dB. 
         [0070]    Also, the S 21  parameter in the X-axis direction at the point P 3 (45, 0) was calculated as −34.45 dB, and the S 21  parameter of the electric field in the Y-axis direction was calculated as −56.06 dB. 
         [0071]    Also, the S 21  parameter in the X-axis direction at the point P 4 (90, 0) was calculated as −41.54 dB, and the S 21  parameter of the electric field in the Y-axis direction was calculated as −42.39 dB. 
         [0072]    As described above, it is understood that a value higher than −60 dB is obtained at all the points P 1  to P 4 . Also, in  FIG. 8 , the values of the S 21  parameters were obtained in an area on the positive direction side of the X-axis and on the negative direction side of the Y-axis with respect to the point P 0  as the center of the plate  111 . This area is ¼ of the entire area of the plate  111  as the XY plane view, and from the symmetry of the plate  111 , this results in obtaining a value higher than −60 dB in all the areas of the plate  111 . 
         [0073]    That is to say, it is possible for the antenna device  100  to communicate with the antenna device  21  of the smartphone terminal  20  in all the areas of the surface  111 A (refer to  FIG. 2 ) of the plate  111 . 
         [0074]      FIG. 9  and  FIG. 10  are diagrams illustrating distribution of the S 21  parameter by a comparative antenna device. 
         [0075]    In  FIG. 9 , a dipole antenna  1  including antenna elements  1 A and  1 B that are disposed along the X-axis direction is disposed on the surface  130 A (refer to  FIG. 2 ) of the substrate  130  in place of the antenna  120 , and the values of the S 21  parameters of the electric field in the X-axis direction at the points P 1  to P 4  were obtained. In this regard, in  FIG. 9 , the radiation plate  110  is not used. The antenna elements  1 A and  1 B are examples of the first antenna element and the second antenna element, respectively. 
         [0076]    In  FIG. 9 , the radiation plate  110  is not used, and thus the area corresponding to an area in which the radiation plate  110  in  FIG. 8  is positioned is denoted by an area D. 
         [0077]    In the same manner, in  FIG. 10 , a dipole antenna  2  including antenna elements  2 A and  2 B that are disposed along the Y-axis direction is disposed on the surface  130 A (refer to  FIG. 2 ) of the substrate  130  in place of the antenna  120 , and the values of the S 21  parameters of the electric field in the Y-axis direction at the points P 1  to P 4  were obtained. In  FIG. 10 , the radiation plate  110  is not used. 
         [0078]    In  FIG. 10 , the radiation plate  110  is not used, and thus the area corresponding to an area in which the radiation plate  110  in  FIG. 8  is positioned is denoted by an area D. 
         [0079]    As illustrated in  FIG. 9 , when the dipole antenna  1  was used in place of the antenna  120  without using the radiation plate  110 , the S 21  parameter in the X-axis direction at a point P 1 (45, 25) was −18.78 dB, and the S 21  parameter in the X-axis direction at a point P 2 (90, 25) was −67.82 dB. 
         [0080]    Also, the S 21  parameter in the X-axis direction at the point P 3 (45, 0) was −32.79 dB, and the S 21  parameter in the X-axis direction at the point P 4 (90, 0) was −53.66 dB. 
         [0081]    As just described, when the dipole antenna  1  is used, the S 21  parameter values at the point P 1  and the point P 3  are favorable, but the S 21  parameter value at the point P 2  is less than −60 dB. It is therefore understood that the distribution or the range of variation of the intensity in the electric field is large in the XY plane. 
         [0082]    When the distribution of the intensity in the electric field is large, there arises a portion in the area D in which the communication with the antenna device  21  of the smartphone terminal  20  is not established. 
         [0083]    As illustrated in  FIG. 10 , when the dipole antenna  2  was used in place of the antenna  120  without using the radiation plate  110 , the S 21  parameter value in the Y-axis direction at the point P 1 (45, 25) was calculated as −64.87 dB, and the S 21  parameter value in the Y-axis direction at the point P 2 (90, 25) was calculated as −87.14 dB. 
         [0084]    Also, the S 21  parameter value in the Y-axis direction at the point P 3 (45, 0) was calculated as −84.35 dB, and the S 21  parameter value in the Y-axis direction at the point P 4 (90, 0) was calculated −47.53 dB. 
         [0085]    Just as described, when the dipole antenna  2  is used, the S 21  parameter values at the points P 1  to P 3  other than the point P 4  are all less than −60 dB, and it is understood that the distribution or the range of variation of the intensity in the electric field is large in the XY plane. 
         [0086]    When the distribution of the intensity in the electric field is large, a portion in the area D that is incapable of communicating with the antenna device  21  of the smartphone terminal  20  arises. 
         [0087]    As described above, with the embodiment, it is possible to provide the antenna device  100  capable of near field communication using a millimeter wave radiated from the surface  111 A of the plate  111 . Also, it is possible to provide the antenna device  100  capable of receiving a millimeter wave from another communication device disposed in the vicinity of the surface  111 A through the surface  111 A of the plate  111 . 
         [0088]    The end part of the plate  112  is in contact with the antenna  120  using the radiation plate  110 , which is formed by joining the plate  111  and the plate  112  in a T-shaped configuration, so that it is possible to guide a millimeter wave that is generated by the antenna  120  and changes the electric field in the X-axis direction in the plate  112  to the joining part between the plate  112  and the plate  111 . The direction of the millimeter wave is converted by 90 degrees such that the electric field changes in the Z-axis direction at the joining part of the plate  112  and the plate  111 . The Z-axis direction is the thickness direction of the plate  111 . 
         [0089]    The millimeter wave is propagated in a direction along in the XY plane inside the plate  111 , and is reflected at the end faces, and thus the millimeter wave is propagated inside the plate  111  in various directions in the XY plane. 
         [0090]    Accordingly, the electric field of the millimeter waves that leaks from the surface  111 A of the plate  111  out of the plate  111  and are folded back toward the plate  111  travel toward various directions in the XY plane. 
         [0091]    Accordingly, when the antenna device  21  in the smartphone terminal  20  is brought close to the surface  111 A of the plate  111  so as to become parallel to the XY plane, it is possible for the antenna device  21  to communicate with the antenna device  100  even when the antenna device  21  faces toward any direction in the XY plane. 
         [0092]    Also, it is possible for the antenna device  21  to communicate with the antenna device  100  even when the antenna device  21  is placed at any position on the surface  111 A of the plate  111 . 
         [0093]    Also, the antenna device  100  uses one antenna  120 , and thus it is possible to reduce power consumption compared with the related-art millimeter wave antenna including a plurality of millimeter wave antenna elements. 
         [0094]    Accordingly, with the embodiment, it is possible to provide the antenna device  100  that achieves reduction of power consumption while expanding a communication possible area in a planar manner using a radio wave having a millimeter wave band. 
         [0095]    In this regard, in the above, a description has been given of the case where the plate  112  protrudes from the center of the plate  111  in the X-axis direction toward the negative direction side of the Z-axis. However, the position to which the plate  112  protrudes from the plate  111  may be shifted from the center of the plate  111  in the X-axis direction. The position that is shifted from the center of the plate  111  in the X-axis direction may be at any position between the end part in the negative X-axis side of the plate  111  and the end part of the positive X-axis side. 
         [0096]    Also, in the above, a description has been given of the configuration in which the length of the plate  112  in the Y-axis direction is equal to the length of the plate  111  in the Y-axis direction. However, the length of the plate  112  in the Y-axis direction may be shorter than the length of the plate  111  in the Y-axis direction. The length of the plate  112  in the Y-axis direction may be equal to the length (the thickness of the plate  112 ) of the plate  112  in the X-axis direction. 
         [0097]    In this case, the positional relationship between the plate  112  and the antenna  120  may be set such that the antenna  120  falls in the X-axis direction width of the plate  112  in the X-axis direction, and in the Y-axis direction width of plate  112  in the Y-axis direction. 
         [0098]    Also, in the above, a description has been given of the configuration in which the antenna device  100  is disposed on the housing  13  such that the radiation surface  101  is exposed from the opening  13 B of the surface  13 A of the housing  13 . However, the radiation surface  101  may be covered with the housing  13 , another thin film, or the like. 
         [0099]    Also, in the above, a description has been given of the case where a patch antenna is used for the antenna  120 . However, a dipole antenna or slot antenna may be used in place of the antenna  120  formed by the patch antenna. 
         [0100]      FIGS. 11A, 11B, and 11C  are diagrams illustrating a dipole antenna, a slot antenna, and a loop antenna, respectively. 
         [0101]    A dipole antenna  120 A illustrated in  FIG. 11A  may be used in place of the antenna  120  formed by the patch antenna. The dipole antenna  120 A includes antenna elements  120 A 1  and  120 A 2 . The antenna elements  120 A 1  and  120 A 2  extend along the X-axis, and are supplied with power at center-side feed point  121 A 1  and  121 A 2 , respectively. It is also possible to radiate a millimeter wave having the electric field that changes in the X-axis in the positive direction of the Z-axis using the dipole antenna  120 A like this. 
         [0102]    In this regard, when the dipole antenna  120 A is used, the positional relationship between the plate  112  and the dipole antenna  120 A is set preferably such that the dipole antenna  120 A falls in the width of the plate  112  in the X-axis direction and the width of the plate  112  in the Y-axis. 
         [0103]    Also, a ground plane may be disposed, to form a monopole antenna, in place of either one of the antenna elements  120 A 1  and  120 A 2 . 
         [0104]    Also, a slot antenna  120 B illustrated in  FIG. 11B  may be used in place of the antenna  120  formed by the patch antenna. The slot antenna  120 B is produced by forming a slot  120 B 1  on the rectangular metal layer in the XY plane view. The slot  120 B 1  is a long and narrow rectangular opening in the Y-axis direction, and is disposed in the center of the rectangular metal layer. When the slot antenna  120 B like this is provided with a feed point  121 B on the negative direction side of the X-axis of the slot  120 B 1  to be supplied with power, it is possible to radiate a millimeter wave having the electric field that changes in the X-axis direction in the positive direction of the Z-axis. In this regard, the feed point  121 B may be disposed on the positive direction side of the X-axis of the slot  120 B 1 . 
         [0105]    Also, when the slot antenna  120 B is used, the positional relationship between the plate  112  and the slot antenna  120 B is set preferably such that the slot  120 B 1  falls in the width in the X-axis direction of the plate  112  in the X-axis direction, and in the width in the Y-axis direction of the plate  112  in the Y-axis direction. 
         [0106]    Also, a loop antenna  120 C illustrated in  FIG. 11C  may be used in place of the antenna  120  formed by the patch antenna. The loop antenna  120 C is an antenna that includes a rectangular loop, and is supplied with power between the feed points  121 C 1  and  121 C 2 . It is possible to radiate a millimeter wave having an electric field that changed in the X-axis direction in the positive direction of the Z-axis using the loop antenna  120 C like this. 
         [0107]    In this regard, when the loop antenna  120 C is used, the positional relationship between the plate  112  and the loop antenna  120 C is set preferably such that the loop antenna  120 C falls in the width in the X-axis direction of the plate  112  in the X-axis direction, and in the width in the Y-axis direction of the plate  112  in the Y-axis direction. 
         [0108]    Also, in the above, a description has been given of the case where the plate  111  and the plate  112  of the radiation plate  110  are integrally formed. However, as illustrated in  FIG. 12 , the plate  111  and the plate  112  may be separate members. 
         [0109]      FIG. 12  is a cross-sectional view illustrating an antenna device  100 A according to a first variation of the first embodiment.  FIG. 12  is the cross-sectional view corresponding to  FIG. 3 . 
         [0110]    The antenna device  100 A includes a radiation plate  110 A, an antenna  120 , and a substrate  130 . 
         [0111]    The radiation plate  110 A includes the plates  111  and  112 , and has a T-shaped configuration as viewed from the Y-axis direction. The plates  111  and  112  of the radiation plate  110 A are separate members, and the plate  112  is joined with the surface  111 B of the plate  111 . 
         [0112]    The antenna device  100 A is the same as the antenna device  100  illustrated in  FIG. 2  to  FIG. 5  except that the plate  111  and the plate  112  are separate members. 
         [0113]    In this manner, the radiation plate  110 A may be formed by joining the plate  111  and the plate  112 , which are separate members. 
         [0114]    Also, in the above, the radiation plate  110  is a separate member of the housing  13  of the electronic apparatus  10  (refer to  FIG. 1 ). However, the radiation plate  110  and the housing  13  may be integrally formed. 
         [0115]      FIG. 13  is a cross-sectional view illustrating an antenna device  100 B according to a second variation of the first embodiment.  FIG. 13  is the cross-sectional view corresponding to  FIG. 3 . 
         [0116]    The antenna device  100 B includes a radiation plate  110 B, an antenna  120 , and a substrate  130 . The radiation plate  110 B includes plates  111 C and  112 C, and has a T-shaped configuration as viewed from the Y-axis direction. 
         [0117]    The plates  111 C and  112 C are formed integrally with the housing  13 . The plates  111 C and  112 C are made of the same dielectric material as that of the housing  13 . 
         [0118]    The plate  111 C indicates a thicker potion which protrudes toward the back side opposite to the surface  13 A of the housing  13 , and is provided with the plate  112 C on the negative direction side of the Z-axis. The sizes of the plates  111 C and  112 C are equal to those of the plates  111  and  112  illustrated in  FIG. 3 , respectively. 
         [0119]    A millimeter wave propagated inside the plate  112 C in the Z-axis direction is propagated inside the plate  111 C in a direction parallel to the XY plane. This is the same as the plates  111  and  112  illustrated in  FIG. 3 . 
         [0120]    The thicknesses of the plate  111 C and the housing  13  are set such that a millimeter wave propagated, in the XY plane view, in the plate  111 C toward the boundary between the plate  111 C and the housing  13  is reflected by the boundary between the plate  111 C and the housing  13 . 
         [0121]    The thinner the dielectric, the higher the transmission loss of the electromagnetic wave, and thus the millimeter wave hardly invades the inside of the wall part of the housing  13  from the end part of the plate  111 C. 
         [0122]    Accordingly, the millimeter wave is reflected by the end portions of the plate  111 C in the same manner as the plate  111  illustrated in  FIG. 3 . The thicknesses of the plate  111 C and the housing  13  are different by about three times, for example. The plate  111 C is set preferably as thick as having a small loss so as to function as a waveguide, and thus have preferably the same thickness as that of the plate  112 C. On the other hand, the housing  13  has preferably a thickness smaller than the thickness for functioning as a waveguide. 
         [0123]    In this manner, with the antenna device  100 B including the radiation plate  110 B built by the plates  111 C and  112 C integrally formed with the housing  13 , it is possible to reduce power consumption using a radio wave of the millimeter wave band while expanding the communication possible area in a planar manner. 
         [0124]      FIG. 14  is a cross-sectional view illustrating an antenna device  100 C according to a third variation of the first embodiment.  FIG. 14  is the cross-sectional view corresponding to  FIG. 3 . 
         [0125]    The antenna device  100 C includes a radiation plate  110 C, an antenna  120 , and a substrate  130 . The radiation plate  110 C is formed by the configuration in which the plates  111 C and  112 C illustrated in  FIG. 13  are separate members. The plate  112 C is joined with the surface  111 B of the plate  111 C. 
         [0126]    The antenna device  100 C is the same as the antenna device  100 B illustrated in  FIG. 13  except that the plates  111 C and  112 C are separate members. 
         [0127]    In this manner, the radiation plate  110 C may be configured by joining the plates  111 C and  112 C as separate members. 
         [0128]      FIG. 15  is a cross-sectional view illustrating a communication module  300  including an antenna device  100 D according to a fourth variation of the first embodiment.  FIG. 15  is the cross-sectional view corresponding to  FIG. 3 . 
         [0129]    The communication module  300  includes an antenna device  100 D, a millimeter wave module  140 , a signal processing unit  150 , and an antenna device  200 . 
         [0130]    The antenna device  100 D includes a radiation plate  110  and an antenna  120 . The antenna device  100 D includes a configuration in which the substrate  130  is removed from the antenna device  100  illustrated in  FIG. 2  to  FIG. 5 . The antenna  120  of the antenna device  100 D is disposed on the millimeter wave module  140 . 
         [0131]    The millimeter wave module  140  converts a signal input from the signal processing unit  150  through a via  160  into a millimeter wave, and outputs the millimeter wave to the antenna  120 . 
         [0132]    The signal processing unit  150  is disposed on the negative direction side of the Z-axis of the antenna device  200 , and is connected to the millimeter wave module  140  through the via  160 . The signal processing unit  150  includes a power supply unit that supplies power to the antenna  120 . The signal processing unit  150  supplies power to the antenna  120  through the via  160  and performs baseband processing. 
         [0133]    The via  160  passes through a through hole (via hole) of the substrate  210  of the antenna device  200  and the inside a cavity  221  that is disposed on the antenna  220  of the antenna device  200 , and electrically connects the millimeter wave module  140  and the signal processing unit  150 . The power and the signal that are output from the signal processing unit  150  are transmitted to the millimeter wave module  140  through the via  160 . 
         [0134]    Also, the signal received by the antenna  120  is transmitted from the millimeter wave module  140  to the signal processing unit  150  through the via  160 . 
         [0135]    The antenna device  200  includes a substrate  210 , an antenna  220 , a communication module  230 , and a wiring line  240 . The antenna device  200  is an example of the second antenna device. 
         [0136]    The antenna device  200  is a communication device that performs near field communication by a band less than 6 GHz, for example. The substrate  210  is an FR4 standard substrate, for example, and is provided with the antenna  220  on the surface on the positive direction side of the Z-axis. As an example, the substrate  210  has the same size as the plate  111  in the XY plane view. In this regard, the size of the substrate  210  in the XY plane view may be different from the size of the plate  111 . 
         [0137]    The antenna  220  is a rectangular patch antenna in the XY plane view, for example, and the size of the patch is set in accordance with communication by a predetermined frequency band less than 6 GHz. The antenna  220  is supplied with power by the communication module  230  through the wiring line  240 . 
         [0138]    Also, the antenna  220  includes the cavity  221 , and the via  160  is inserted into the inside of the cavity  221 . 
         [0139]    In this regard, the antenna  220  is not limited to a patch antenna, and may be a loop antenna that forms a loop in the XY plane, for example. A loop antenna including a loop having a size in accordance with the communication by a predetermined frequency band less than 6 GHz may be used as the antenna  220 . In this case, the millimeter wave module  140  is preferably disposed in the loop of the antenna  220  in the XY plane view. 
         [0140]    The antenna device  100 D is piled with the antenna device  200  that performs communication by a band less than 6 GHz in the Z-axis direction to form the communication module  300 . 
         [0141]    Accordingly, it is possible to perform near field communication using a millimeter wave that the plate  111  radiates or receives using the communication module  300 , and to perform near field communication using a radio wave having the band of less than 6 GHz that the antenna  220  radiates or receives. 
         [0142]    In the above, descriptions have been given of the antenna devices according to the exemplary embodiments of the present disclosure and communication module. However, the present disclosure is not limited to the specifically disclosed embodiments, and various variations and changes are possible without departing from the scope of the appended claims. 
         [0143]    All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.