Patent Publication Number: US-11652302-B2

Title: Antenna device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is based on Japanese Patent Application No. 2021-23685 filed on Feb. 17, 2021, disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to an antenna device. 
     BACKGROUND 
     In an antenna device, an array antenna and a waveguide are formed on a same substrate. A strip line is used to supply power to the array antenna. 
     SUMMARY 
     One object of the present disclosure is to provide an antenna device that can reduce loss while improving gain. 
     An antenna device disclosed herein includes 
     a substrate having a base material containing a dielectric and a conductor arranged in the base material, 
     a waveguide that is arranged in the base material as a part of the conductor, and has an upper wall portion, a lower wall portion facing the upper wall portion in a plate thickness of the base material, and a side wall portion connected to the upper wall portion and the lower wall portion, 
     an antenna that is arranged in the base material as a part of the conductor, and has a plurality of patch portions arranged in an array so as to face the upper wall portion in the plate thickness direction, a plurality of feeding lines extending in the plate thickness direction from the patch portion and individually provided for the patch portions, and a plurality of short-circuit portions individually provided for the patch portions and electrically connecting the patch portion and the upper wall portion, and 
     a matching portion that is arranged in the base material as a part of the conductor and is individually provided with respect to the patch portion in order to match an impedance of the waveguide and an impedance of the antenna. 
     The upper wall portion has a plurality of openings individually formed with respect to the feeding lines. 
     Each of the feeding lines extends into the waveguide through the corresponding opening. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view showing an example of an antenna device according to a first embodiment; 
         FIG.  2    is a cross-sectional view taken along a line II-II of  FIG.  1   ; 
         FIG.  3    is a cross-sectional view taken along a line III-III of  FIG.  1   ; 
         FIG.  4    is an enlarged view of region IV of  FIG.  3   ; 
         FIG.  5    is a perspective view showing an example of four elements. 
         FIG.  6    is an exploded perspective view of the antenna device illustrated in  FIG.  5   ; 
         FIG.  7    is a diagram showing radiation characteristics of two elements; 
         FIG.  8    is a diagram showing radiation characteristics of four elements; 
         FIG.  9    is a cross-sectional view showing a modified example; 
         FIG.  10    is a cross-sectional view showing an antenna device according to a second embodiment; 
         FIG.  11    is a cross-sectional view showing an antenna device according to a third embodiment; 
         FIG.  12    is a cross-sectional view showing an antenna device according to a fourth embodiment; 
         FIG.  13    is a perspective view showing an antenna device according to a fifth embodiment; 
         FIG.  14    is a diagram showing radiation characteristics; 
         FIG.  15    is a perspective view showing an antenna device according to a sixth embodiment; and 
         FIG.  16    is a diagram showing radiation characteristics. 
     
    
    
     DETAILED DESCRIPTION 
     In an assumable example of an antenna device, an array antenna and a waveguide are formed on a same substrate. A strip line is used to supply power to the array antenna. The disclosure of the patent document (JP 2008-5164 A) relating to the strip line is incorporated herein by reference as an explanation of the technical elements in this disclosure. 
     When a band such as a millimeter wave band becomes high, a radiation loss increases due to the increase in the amount of radiation from the strip line. Further, in an electric field formed in a plate thickness direction of the substrate for radio wave propagation of the strip line, the amount of the electric field spreading in the substrate increases, so that the dielectric loss increases. Further improvements are required in the antenna device in the above-mentioned viewpoint or in other viewpoints not mentioned. 
     One object of the present disclosure is to provide an antenna device that can reduce loss while improving gain. 
     An antenna device disclosed herein includes 
     a substrate having a base material containing a dielectric and a conductor arranged in the base material, 
     a waveguide that is arranged in the base material as a part of the conductor, and has an upper wall portion, a lower wall portion facing the upper wall portion in a plate thickness of the base material, and a side wall portion connected to the upper wall portion and the lower wall portion, 
     an antenna that is arranged in the base material as a part of the conductor, and has a plurality of patch portions arranged in an array so as to face the upper wall portion in the plate thickness direction, a plurality of feeding lines extending in the plate thickness direction from the patch portion and individually provided for the patch portions, and a plurality of short-circuit portions individually provided for the patch portions and electrically connecting the patch portion and the upper wall portion, and 
     a matching portion that is arranged in the base material as a part of the conductor and is individually provided with respect to the patch portion in order to match an impedance of the waveguide and an impedance of the antenna. 
     The upper wall portion has a plurality of openings individually formed with respect to the feeding lines. 
     Each of the feeding lines extends into the waveguide through a corresponding opening. 
     According to the disclosed antenna device, the waveguide, the antenna, and the matching portion are formed in the substrate. The antenna has a plurality of patch portions arranged in an array, and a gain can be improved. Further, the feeding line extends from the patch portion to the inside of the waveguide through the opening. The feeding line extends in the plate thickness direction from the patch portion, instead of extending in a direction orthogonal to the plate thickness direction as in the strip line. Therefore, even in a high frequency band such as a millimeter wave band, radiation from the feeding line can be suppressed, that is, radiation loss can be suppressed. It is not a power supply by forming an electric field in the plate thickness direction for radio wave propagation like a microstrip line, so that the amount of electric field spreading in the substrate is small, and the dielectric loss due to the feeding line can be suppressed. As a result, it is possible to provide the antenna device that can reduce the loss. 
     The disclosed aspects in this specification adopt different technical solutions from each other in order to achieve their respective objectives. The objects, features, and advantages disclosed in this specification will become apparent by referring to following detailed descriptions and accompanying drawings. 
     Hereinafter, multiple embodiments will be described with reference to the drawings. The same reference numerals are assigned to the corresponding elements in each embodiment, and thus, duplicate descriptions may be omitted. When only a part of the configuration is described in the respective embodiments, the configuration of the other embodiments described before may be applied to other parts of the configuration. Further, not only the combinations of the configurations explicitly shown in the description of the respective embodiments, but also the configurations of the plurality of embodiments can be partially combined even when they are not explicitly shown as long as there is no difficulty in the combination in particular. 
     FIRST EMBODIMENT 
     The antenna device is configured to transmit and/or receive radio waves of a predetermined operating frequency. The antenna device is used, for example, in a high-speed wireless transmission system in the 80 GHz band. 
     &lt;Antenna Device&gt; 
     First, the antenna device will be described with reference to  FIGS.  1  to  4   .  FIG.  1    is a perspective view showing a schematic configuration of an example of an antenna device.  FIG.  2    is a cross-sectional view taken along a line II-II of  FIG.  1   .  FIG.  3    is a cross-sectional view taken along a line III-III of  FIG.  1   .  FIG.  4    is an enlarged view of the region IV shown by an alternate long and short dash line in  FIG.  3    in order to show a configuration of a matching portion. That is, in  FIGS.  1  to  3   , the matching portion  50  is shown in a simplified manner. The white arrows shown in  FIGS.  1  and  2    indicate a feeding direction. In other figures as well, the feeding direction is indicated by the white arrow. 
     As shown in  FIGS.  1  to  4   , the antenna device  10  includes a substrate  20 , a waveguide  30 , an antenna  40 , and a matching portion  50 . In the following, a plate thickness direction of the substrate  20  is defined as a Z direction, and one direction orthogonal to the Z direction is defined as a X direction. A direction orthogonal to the Z direction and the X direction is defined as a Y direction. Unless otherwise specified, a shape viewed in a plane from the Z direction, that is, a shape along an XY plane defined by the X and Y directions is referred to as a planar shape. The plan view from the Z direction may be simply referred to as a plan view. 
     The substrate  20  has a base material  21  and a conductor  22 . The substrate  20  may be referred to as a printed circuit board or a wiring board. The substrate  20  includes a front surface  20   a  and a back surface  20   b  as a surface opposite to the front surface  20   a  in the Z-direction. The base material  21  contains a dielectric material such as a resin. By using the base material  21 , a wavelength shortening effect by the dielectric material can be expected. As the base material  21 , for example, a material made of only a resin, a combination of a resin and a glass cloth, a non-woven fabric, or the like, a material containing ceramic, or the like can be adopted. The base material  21  is sometimes referred to as an insulating base material. The base material  21  is configured by, for example, laminating an insulating layer containing a dielectric material in multiple layers. 
     The conductor  22  is arranged in the base material  21 . The conductor  22  is formed on a printed circuit board by using a general wiring technique. The conductor  22  includes a conductor pattern and a via conductor. The conductor pattern is sometimes referred to as a conductor layer. The conductor pattern is arranged in multiple layers in the base material  21 . That is, the substrate  20  is a multilayer substrate. The conductor pattern is formed by patterning a metal foil such as a copper foil. A via conductor is formed by arranging a conductor such as plating in a through hole (via) formed in an insulating layer constituting the base material  21 . 
     In the antenna device  10 , elements other than the substrate  20  are arranged in the base material  21  as a part of the conductor  22 . The waveguide  30 , the antenna  40 , and the matching portion  50  are configured by using the conductor  22 . That is, the waveguide  30 , the antenna  40 , and the matching portion  50  are formed on the substrate  20 . The substrate  20  may include only the components of the waveguide  30 , the antenna  40 , and the matching portion  50  as the conductor  22 , or may include circuit elements other than the above-mentioned components. 
     The waveguide  30  is a transmission path for supplying power to the antenna  40 . Radio waves propagate in the waveguide  30 . As described above, the waveguide  30  is arranged in the base material  21  as a part of the conductor  22 . The waveguide  30  has an upper wall portion  31 , a lower wall portion  32 , and a side wall portion  33 . The upper wall portion  31 , the lower wall portion  32 , and the side wall portion  33  are a part of the conductor  22  arranged in the base material  21 . The upper wall portion  31  and the lower wall portion  32  are arranged to face each other with a predetermined distance in the Z direction. 
     In the present embodiment, the lower wall portion  32  is formed by a surface layer pattern on the back surface  20   b  side of the substrate  20 . The surface layer pattern is a conductor pattern arranged on the surface layer (front surface) of the base material  21 . On the other hand, an inner layer pattern described later is a conductor pattern arranged inside the base material  21 . The upper wall portion  31  is located between the lower wall portion  32  and a patch portion  41  described later in the Z direction. That is, the upper wall portion  31  is arranged at a position closer to the patch portion  41  than the lower wall portion  32 . The side wall portion  33  is connected to the upper wall portion  31  and the lower wall portion  32 . As described above, the waveguide  30  is a transmission path having a tunnel structure surrounded by the upper wall portion  31 , the lower wall portion  32 , and the side wall portion  33 . The waveguide  30  extends in the X direction, and power is supplied to the waveguide  30  from one end side in the X direction. 
     The waveguide  30  has a substantially rectangular ring shape. Such a waveguide  30  is sometimes referred to as a rectangular waveguide. The base material  21  is arranged inside the waveguide  30 . In the waveguide  30 , a width, which is an opening length in the Y direction, is longer than a height, which is the opening length in the Z direction. The width of the waveguide  30  is set within the range of 0.5×λε or more and 1×λε or less, that is, ½ wavelength or more and 1 wavelength or less with respect to a wavelength λε of a radio wave of an operating frequency. The wavelength λε is a wavelength in consideration of the dielectric material (relative dielectric constant). The wavelength λε can be obtained by a square root of a value obtained by dividing (300 [mm/s]/operating frequency [GHz]) by the dielectric constant of the base material  21 . The height of the waveguide  30  is set to about ½ wavelength, for example, in the range of 0.4×λε to 0.6×λε. By setting such a length, radio waves propagate in the waveguide  30 . 
     The waveguide  30  has an opening  34 . The opening  34  is formed in the upper wall portion  31 . The opening  34  penetrates the upper wall portion  31  in the Z direction. The opening  34  is formed so that a feeding line  42 , which will be described later, can be extended to an inside of the waveguide  30 . The openings  34  are individually formed with respect to the feeding line  42 . The opening  34  is formed so as to overlap a part of the corresponding patch portion  41  in a plan view. The opening  34  is formed in such a size that it does not come into contact with the feeding line  42  and radio waves do not leak from the waveguide  30 . 
     The opening  34  has a substantially circular shape in a plan view. A diameter D of the opening  34  can be calculated from a following equation (1). Here, d is the diameter of the feeding line  42 , ε is the relative permittivity of the base material  21 , and Z 0  is an impedance converted by the matching portion  50 . 
     
       
         
           
             
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     1 
                   
                   ] 
                 
               
               
                  
               
             
             
               
                 
                   
                     Z 
                     0 
                   
                   = 
                   
                     
                       138 
                       
                         ϵ 
                       
                     
                     ⁢ 
                     
                       log 
                       10 
                     
                     ⁢ 
                     
                       D 
                       d 
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
     The antenna  40  has the patch portion  41 , the feeding line  42 , and a short-circuit portion  43 . The antenna  40  uses the upper wall portion  31  (waveguide  30 ) as a ground board of the antenna  40 . The upper wall portion  31  functions as the ground board of the antenna  40 . The ground board is connected to a feeder circuit (not shown) to supply a ground potential of the antenna device  10 . An opening is provided in the lower wall portion  32  of the waveguide  30 , and the upper wall portion  31  provides a ground potential by electrically connecting, for example, a standard waveguide, an outer conductor of a coaxial cable, or the like. The direction perpendicular to a plate surface of the ground board  30  is also substantially parallel to the Z direction. In a plan view, the area of the ground board is larger than the area of the patch portion  41 . The ground board has a size that includes the patch portion  41 . The ground board preferably has a size necessary for the antenna  40  to operate stably. 
     The patch portion  41  is arranged in the base material  21  as a part of the conductor  22  so as to function as a radiation element. The patch portion  41  includes the conductor pattern described above. The arrangement of the conductor patterns constituting the patch portion  41  in the Z direction is not particularly limited. It may be a surface layer pattern or an inner layer pattern. The patch portion  41  is arranged to face the upper wall portion  31  so as to have a predetermined distance from the ground board, that is, the upper wall portion  31  in the Z direction. The patch portion  41  may be referred to as a radiation element or an antenna element. In a plan view, the entire patch portion  41  overlaps with the upper wall portion  31 . That is, the entire plate surface (lower surface) of the patch portion  41  faces the upper wall portion  31  in the Z direction. The patch portion  41  is arranged substantially parallel to the upper wall portion  31 . Substantially parallel is not limited to perfect parallelism. 
     The patch portion  41  of the present embodiment is arranged on the front surface  20   a  of the substrate  20 . The patch portion  41  is a surface layer pattern on the front surface  20   a  side of the substrate  20 . A basic shape of the patch portion  41  is a substantially square in the plan view. The basic shape is an outer contour of the patch portion  41  in a plan view. The patch portion  41  has four sides that define the outer contour in the plan view. The patch portion  41  may have slits on at least one of the four sides. 
     By arranging the patch portion  41  facing the upper wall portion  31  which is the ground board, a capacitor is formed according to the area of the patch portion  41  and the distance from the ground board. The patch portion  41  is formed to have a size that forms a capacitance that performs parallel resonance with the inductance of the short-circuit portion  43  at a target frequency. The area of the patch portion  41  is appropriately designed to provide the desired capacitance and thus to operate at the operating frequency. 
     In the present embodiment, the basic shape, in other words, the outer contour of the patch portion  41  is square as an example, but as another configuration, the planar shape of the patch portion  41  may be circular, regular octagon, regular hexagon, or the like. The basic shape of the patch portion  41  may have a line-symmetrical shape, that is, a bidirectional line-symmetric shape, with each of two straight lines orthogonal to each other as axes of symmetry. The bidirectional line symmetrical shape refers to a figure that is line-symmetric with a first straight line as an axis of symmetry, and that is also line-symmetric with respect to a second straight line that is orthogonal to the first straight line. The bidirectional line symmetrical shape corresponds to, for example, an ellipse, a rectangle, a circle, a square, a regular hexagon, a regular octagon, a rhombus, or the like. Further, the patch portion  41  may also be a point-symmetrical figure such as a circle, a square, a rectangle, or a parallelogram. 
     The feeding line  42  is arranged in the base material  21  as a part of the conductor  22  in order to supply power to the patch portion  41 . The feeding line  42  is electrically connected to the patch portion  41 . The feeding line  42  includes the via conductor described above. The power supply method is not limited to a direct power supply method. A power supply method in which the feeding line  42  and the patch portion  41  are electromagnetically coupled may also be adopted. One of the ends of the feeding line  42  is electrically connected to the patch portion  41 . The electrical connection part between the patch portion  41  and the feeding line  42  is the feeding point. The feeding line  42  extends in the Z direction. Another end of the feeding line  42  is located inside the waveguide  30 . The feeding line  42  extends from the patch portion  41  (feeding point) to the inside of the waveguide  30  through the opening  34  formed in the upper wall portion  31 . The current input from the waveguide  30  to the feeding line  42  is conducted to the patch section  41  and resonates the patch portion  41 . The feeding line  42  of the present embodiment is composed of a plurality of via conductors arranged side by side in the Z direction. 
     The short-circuit portion  43  is arranged in the base material  21  as a part of the conductor  22  in order to electrically connect, that is, short-circuit the upper wall portion  31  which is the ground board and the patch portion  41 . The short-circuit portion  43  includes the via conductors described above. One of the ends of the short circuit portion  43  is connected to the upper wall portion  31  and the other end is connected to the patch portion  41 . The short-circuit portion  43  has, for example, a substantially circular in the plan view. By adjusting the diameter and length of the short-circuit portion  43 , the inductance provided in the short-circuit portion  43  can be adjusted. The short-circuit portion  43  is connected to substantially the center of the patch portion  41  in a plan view. Further, the center of the patch portion  41  corresponds to the centroid of the patch portion  41 . 
     Since the patch portion  41  according to the present embodiment has a square shape in the plan view, the center corresponds to an intersection of two diagonal lines of the patch portion  41 . The number of via conductors constituting the short-circuit portion  43  is not particularly limited. In the present embodiment, one via conductor includes the short-circuit portion  43 . The short-circuit portion  43  may be formed by a plurality of via conductors arranged in parallel between the upper wall portion  31  and the patch portion  41 . 
     The antenna  40  has a plurality of patch portions  41 , feeding lines  42 , and short-circuit portions  43  having the above-described configurations. The plurality of patch portions  41  are arranged to face the common (single) upper wall portion  31 . The plurality of patch portions  41  are arranged in an array in the plan view. In the embodiment shown in  FIGS.  1  to  4   , a plurality of patch portions  41  are arranged along the X direction. Specifically, the three patch portions  41  are lined up in a row. A distance between the centers of the patch portions  41  arranged in a row is set within a range of 0.25×λε or more and 1×λε or less, that is, within a range of ¼ wavelength or more and 1 wavelength or less. 
     In the following, the number of elements may be indicated by the number of patch portions  41 .  FIGS.  1  to  4    show an example of three elements. The plurality of feeding lines  42  are individually provided with respect to the patch portion  41 . The feeding line  42  is configured to be able to supply power to a plurality of patch portions  41  individually. A plurality of short-circuit portions  43  are also individually provided with respect to the patch portion  41 . That is, the feeding line  42  and the short-circuit portion  43  are provided for each patch portion  41 . 
     The matching portion  50  matches the impedance of the waveguide  30  with the impedance of the antenna  40 . The matching portion  50  is sometimes referred to as a conversion portion because it converts impedance between the waveguide  30  and the antenna  40 . For example, the impedance of the waveguide  30  is 1000 or more, and the impedance of the antenna  40  is 50 to 75Ω. The matching portion  50  converts, for example, into an impedance intermediate between the waveguide  30  and the antenna  40 . The matching portion  50  may convert the impedance of the waveguide  30  to a value substantially equal to the impedance of the antenna  40 . 
     The matching portion  50  is also arranged in the base material  21  as a part of the conductor  22 . The matching portion  50  is individually provided with respect to the patch portion  41 , that is, the radiation element. The matching portion  50  of the present embodiment is arranged inside the waveguide  30 . As shown in  FIG.  4   , the matching portion  50  includes an inner layer pattern  51  and a via conductor  55 . The inner layer pattern  51  corresponds to the first inner layer pattern, and the via conductor  55  corresponds to the second via conductor. 
     The inner layer pattern  51  is connected to the feeding line  42  at a position away from the patch portion  41  so as to face the lower wall portion  32 . The inner layer pattern  51  is arranged inside the waveguide  30 . The inner layer pattern  51  is located between the upper wall portion  31  and the lower wall portion  32  in the Z direction. One of the ends of the via conductor  55  is connected to the conductor pattern constituting the lower wall portion  32 , and the other end is connected to the inner layer pattern  51 . In this way, the matching portion  50  is connected to an inner surface  32   a  of the lower wall portion  32  and has a predetermined height from the inner surface  32   a . The number of via conductors  55  interposed between the inner layer pattern  51  and the lower wall portion  32  is not particularly limited. Only one via conductor  55  may be arranged, or a plurality of via conductors may be arranged. In the present embodiment, three or more via conductors  55  are arranged for one inner layer pattern  51 . 
     The matching portion  50  is connected to a tip of the feeding line  42 . The conductor  22  that constitutes the matching portion  50  is electrically connected to the conductor  22  that constitutes the feeding line  42 . The feeding line  42  and/or the feeding line  42  including the matching portion  50  extends below the center of the height of the waveguide  30 . That is, the feeding line  42  arranged inside the waveguide  30  and/or the feeding line  42  including the matching portion  50  has a length of ¼ wavelength or more. 
       FIGS.  5  and  6    show a more specific configuration example of the antenna device  10 .  FIG.  5    is a perspective view of the antenna device  10 . In  FIG.  5   , the matching portion  50  is shown in a simplified manner.  FIG.  6    is an exploded perspective view.  FIGS.  5  and  6    show an example of four elements. The four patch portions  41  are arranged in a row in the X direction. The base material  21  is formed by laminating three insulating layers  210 ,  211 , and  212 . The conductor pattern has the patch portion  41  and the lower wall portion  32  which are surface layer patterns, and the upper wall portion  31  and the inner layer pattern  51  which are inner layer patterns. That is, four layers of conductor patterns are arranged in the base material  21 . 
     The side wall portion  33  of the waveguide  30  is composed of a plurality of via conductors  330 . The plurality of via conductors  330  are arranged at intervals so that radio waves do not leak out. The plurality of via conductors  330  are arranged so that one end side in the X direction is open so that power can be supplied and the other end side is closed. The plurality of via conductors  330  are arranged in a substantially U-shape in the plane view. The via conductor  330  is sometimes referred to as a post. The side wall portion  33  composed of the plurality of via conductors  330  is sometimes referred to as a post wall. The waveguide  30  having the side wall portion  33  made of the via conductor  330  is sometimes referred to as a post wall waveguide. 
     The feeding line  42  is composed of a via conductor  420 . The via conductor  420  corresponds to the first via conductor. A plurality of via conductors  420  are connected to each other through the opening  34  to form the feeding line  42 . The short-circuit portion  43  is composed of the via conductor  430 . One of the ends of the via conductor  430  is connected to the patch portion  41  and the other end is connected to the upper wall portion  31 . As described above, the matching portion  50  is composed of the inner layer pattern  51  and the via conductor  55 . Four via conductors  55  are interposed between the lower wall portion  32  and one inner layer pattern  51 . 
     &lt;Antenna Operation&gt; 
     Next, the operation of the antenna  40  will be described. As described above, the antenna  40  has a structure in which the ground board (upper wall portion  31 ) and the patch portion  41  facing each other are connected by the short-circuit portion  43 . This structure is a so-called mushroom structure, which is the same as a basic structure of metamaterials. Since the antenna  40  is an antenna to which a metamaterial technology is applied, the antenna  40  is sometimes called a metamaterial antenna. 
     Since the antenna  40  of the present embodiment is designed to operate in the zeroth-order resonant mode at a desired operating frequency, the antenna device may also be referred to as a zeroth-order resonant antenna. Among the dispersion characteristics of metamaterials, a phenomenon of resonance at a frequency at which a phase constant β becomes zero (0) is the zeroth-order resonance. The phase constant β is an imaginary part of a propagation coefficient γ of a wave propagating on a transmission line. The antenna  40  can satisfactorily transmit and/or receive radio waves in a predetermined band including the frequency at which the zeroth-order resonance occurs. 
     The antenna  40  operates by LC parallel resonance of a capacitor formed between the ground board and the patch portion  41  and an inductor provided in the short-circuit portion  43 . The patch portion  41  is short-circuited to the ground board by the short-circuit portion  43  provided in the central region thereof. The area of the patch portion  41  is an area that forms a capacitor that resonates in parallel with the inductor of the short-circuit portion  43  at a desired frequency (operating frequency). A value of the inductor is determined according to the dimension of each part of the short-circuit portion  43 , for example, the diameter and the length of the short-circuit portion  43 . The value of the inductor may also be referred to as inductance. 
     Therefore, when electric power of the operating frequency is supplied, parallel resonance occurs due to energy exchange between the inductor and the capacitor, and an electric field perpendicular to the ground board is generated between the ground board and the patch portion  41 . That is, an electric field in the Z direction is generated. This vertical electric field propagates from the short-circuit portion  43  toward the edge portion of the patch portion  41  becomes vertically polarized at the edge portion of the patch portion  41 , and propagates in space. The vertically polarized wave here refers to a radio wave in which the vibration direction of the electric field is perpendicular to the ground board and the patch portion  41 . Further, the antenna device  10  receives a vertically polarized wave coming from the outside of the antenna device  10  by LC parallel resonance. 
     The resonance frequency of the zeroth-order resonance does not depend on the antenna size. Therefore, the length of one side of the patch portion  41  can be made shorter than ½ wavelength of the zeroth-order resonance frequency. For example, even if one side has a length equivalent to a one-quarter wavelength, zeroth-order resonance can be generated. It is possible to make one side shorter than a one-quarter wavelength. However, for instance, the gain such as antenna gain is reduced. 
     &lt;Directivity and Antenna Gain&gt; 
       FIGS.  7  and  8    illustrate a result of electromagnetic field simulation of the antenna device  10  having the above configuration.  FIG.  7    shows an example of two elements.  FIG.  8    shows an example of four elements as shown in  FIGS.  5  and  6   . The other conditions are the same as those in  FIGS.  7  and  8    except that the number of elements is different. For example, the operating frequency is 82.3 GHz and the dielectric constant is 3.6. 
     As shown in  FIG.  7   , in the case of two elements, the maximum gain is 5.9 dBi. As shown in  FIG.  8   , in the case of 4 elements, the maximum gain is 8.6 dBi. By increasing the number of elements in this way, the maximum gain of the antenna  40  is improved. Further, each of the two elements and the four elements shows directivity in the X direction, which is the arrangement direction of the elements (patch portion  41 ). 
     Summary of First Embodiment 
     A metamaterial antenna has a low gain as a single unit. Therefore, in order to improve the gain, arraying is required. The metamaterial antenna is configured to have the short-circuit portion (via conductor) constituting an inductor, and the ground board and the patch portion constituting a capacitor on the substrate containing a dielectric material. A strip line is commonly used to array metamaterial antennas with such a structure. However, the strip line extends from the feeding point with the patch portion on the same surface as the patch portion, and faces the ground board in the plate thickness direction of the substrate. Therefore, when the frequency band such as the millimeter wave band becomes high, the radiation amount from the strip line increases and the radiation loss increases. Further, in an electric field formed in a plate thickness direction of the substrate for radio wave propagation of the strip line, the amount of the electric field spreading in the substrate increases, so that the dielectric loss increases. In this way, the loss tends to be large. 
     In the present embodiment, the waveguide  30 , the antenna  40 , and the matching portion  50  are formed in the substrate  20 . The antenna  40  has a plurality of patch portions  41  arranged in an array. Gain can be improved by arranging. Further, the feeding line  42  extends from the patch portion  41  to the inside of the waveguide  30  through the opening  34  formed in the upper wall portion  31 . The feeding line  42  does not extend in the direction orthogonal to the Z direction like the strip line, but extends in the Z direction from the patch portion  41 . Therefore, even in a high frequency band such as a millimeter wave band, radiation from the feeding line  42  can be suppressed, that is, radiation loss can be suppressed. It is not a power supply by forming an electric field in the Z direction for radio wave propagation like a microstrip line, so that the amount of electric field spreading in the substrate  20  is small, and the dielectric loss due to the feeding line  42  can be suppressed. As a result, it is possible to provide the antenna device  10  that can reduce the loss. 
     Further, in the present embodiment, each of the feeding lines  42  includes the via conductor  420 . As a result, the feeding line  42  extending in the Z direction can be realized in the substrate  20 . In addition, the configuration of the feeding line  42  can be simplified. 
     Further, in the present embodiment, the matching portion  50  includes the inner layer pattern  51  and the via conductor  55  arranged inside the waveguide  30 . The inner layer pattern  51  is connected to the feeding line  42  at a position away from the patch portion  41  so as to face the lower wall portion  32 . The via conductor  55  is connected to the inner layer pattern  51 . The matching portion  50  is connected to the inner surface  32   a  of the lower wall portion  32  and has a predetermined height from the inner surface  32   a.    
     In this way, by providing the matching portion  50  having a predetermined height from the inner surface  32   a  of the lower wall portion  32 , the opening area of the waveguide  30  becomes narrower in the arranged portion of the matching portion  50  than in the non-arranged portion thereof. Therefore, the impedance of the waveguide  30  can be converted into a value close to the impedance of the antenna  40  or a value equal to the impedance of the antenna  40 . For example, assuming that the impedance of the waveguide  30  is 100Ω and the impedance of the antenna  40  is 50Ω, the impedance of the matching portion  50  can be 75Ω or 50Ω. Since the matching portion  50  can be configured by a part of the conductor  22  of the substrate  20 , the configuration can be simplified. Since the matching portion  50  is provided on each of the feeding lines  42 , the impedance can be matched between each of the elements and the waveguide  30 . 
     The configuration of the matching portion  50  is not limited to the above example. In the modified example shown in  FIG.  9   , the matching portion  50  is arranged inside the waveguide  30  as in  FIG.  4   . The matching portion  50  is composed of the inner layer patterns  51  and the via conductors  55  arranged in multiple stages. Specifically, it has a two-stage structure by adding one stage including the via conductor  55  and an inner layer pattern  51  to the matching portion  50  shown in  FIG.  4   . According to this structure, the height of the matching portion  50  can be made higher, and the opening area of the waveguide  30  can be made smaller. 
     In  FIG.  9   , the area of the upper inner layer pattern  51  near the patch portion  41  is smaller than the area of the lower inner layer pattern  51 . According to this configuration, the band can be widened. The area is an area when viewed in a plan view, that is, an area facing the lower wall portion  32 . The area relationship between the upper inner layer pattern and the lower inner layer pattern is not limited to the above example. For example, the upper inner layer pattern may have the same configuration as the lower inner layer pattern. Further, the number of stages of the matching portion  50  is not limited to two-stage structure. The number of stages of the matching portion  50  may be 3 or more. 
     SECOND EMBODIMENT 
     The second embodiment is a modification of the preceding embodiment as a basic configuration and may incorporate description of the preceding embodiments. In the above embodiment, the matching portion was formed by the inner layer pattern and the via conductor located between the upper wall portion and the lower wall portion. Instead of this configuration, the matching portion may be formed by the inner layer pattern located at the opening. 
       FIG.  10    is a cross-sectional view showing the antenna device  10  according to the second embodiment.  FIG.  10    corresponds to  FIG.  2   . As shown in  FIG.  10   , the matching portion  50  includes an inner layer pattern  52  arranged in the opening  34 . The inner layer pattern  52  is also connected to the feeding line  42  at a position away from the patch portion  41  so as to face the lower wall portion  32 . The inner layer pattern  52  is connected not at the tip of the feeding line  42  but in a middle thereof. The inner layer pattern  52  is arranged on the same surface as the upper wall portion  31  in the substrate  20 . The inner layer pattern  52  corresponds to the second inner layer pattern. Other configurations are the same as those described in the prior embodiments. 
     Summary of Second Embodiment 
     As described above, the matching portion  50  of the present embodiment includes the inner layer pattern  52 . By providing the inner layer pattern  52 , the capacitors are connected in parallel and the inductors are connected in series with respect to the impedance of the waveguide  30 . As a result, the impedance is made smaller than that of the waveguide  30  by the matching portion  50 , and the impedance of the waveguide  30  and the impedance of the antenna  40  can be matched. 
     Further, since the inner layer pattern  52  is arranged on the same surface as the upper wall portion  31 , it can be formed by the same process as the upper wall portion  31 . That is, the manufacturing process can be simplified. 
     THIRD EMBODIMENT 
     The second embodiment is a modification of the preceding embodiment as a basic configuration and may incorporate description of the preceding embodiments. In the above embodiments, the matching portion is configured by the inner layer pattern located in the waveguide. Instead of this configuration, the matching portion may be configured by an inner layer pattern located outside the waveguide. 
       FIG.  11    is a cross-sectional view showing the antenna device  10  according to the present embodiment.  FIG.  11    corresponds to  FIG.  12   . As shown in  FIG.  11   , the matching portion  50  includes an inner layer pattern  53  arranged between the patch portion  41  and the upper wall portion  31  in the Z direction. The inner layer pattern  53  is also connected to the feeding line  42  at a position away from the patch portion  41  so as to face the lower wall portion  32 . The inner layer pattern  53  is connected not at the tip of the feeding line  42  but in a middle thereof. The inner layer pattern  53  may be smaller than the opening  34  in a plan view, or may have a size consistent with the opening  34 . Furthermore, it may be larger than the opening  34 . The inner layer pattern  53  corresponds to the third inner layer pattern. Other configurations are the same as those described in the prior embodiments. 
     Summary of Third Embodiment 
     As described above, the matching portion  50  of the present embodiment includes the inner layer pattern  53 . By providing the matching portion  50  at a position away from the lower wall portion  32 , the capacitor is connected in parallel and the inductor is connected in series with respect to the impedance of the waveguide  30  as in the configuration of the second embodiment. As a result, the impedance is made smaller than that of the waveguide  30  by the matching portion  50 , and the impedance of the waveguide  30  and the impedance of the antenna  40  can be matched. 
     Fourth Embodiment 
     The second embodiment is a modification of the preceding embodiment as a basic configuration and may incorporate description of the preceding embodiments. The matching portion can be combined in various ways as shown in the preceding embodiments. 
       FIG.  12    is a cross-sectional view showing the antenna device  10  according to the present embodiment.  FIG.  12    corresponds to  FIG.  2   . As shown in  FIG.  12   , the matching portion  50  is a combination of the configuration shown in  FIG.  4    and the configuration shown in  FIG.  11   . That is, the matching portion  50  includes the inner layer pattern  51  and the via conductor  55  arranged inside the waveguide  30 , and the inner layer pattern  53  arranged outside the waveguide  30 . Other configurations are the same as those described in the prior embodiments. 
     Summary of Fourth Embodiment 
     According to the configuration shown in  FIG.  12   , the opening area of the waveguide  30  is reduced by the inner layer pattern  51  and the via conductor  55  in the matching portion  50 . Further, the capacitor and the inductor are connected to the impedance of the waveguide  30  by the inner layer pattern  53  of the matching portion  50 . With the above two configurations, the impedance is made smaller than that of the waveguide  30  by the matching portion  50 , and the impedance of the waveguide  30  and the impedance of the antenna  40  can be matched. 
     In addition to the example shown in  FIG.  12   , the matching portion  50  can be combined in various ways. For example, as the matching portion  50 , a combination of the configuration shown in  FIG.  4    and the configuration shown in  FIG.  10    may be adopted. Needless to say, in combination of the configurations shown in  FIGS.  10  and  11   , the configuration shown in  FIG.  9    may be adopted instead of the configuration shown in  FIG.  4   . 
     FIFTH EMBODIMENT 
     The second embodiment is a modification of the preceding embodiment as a basic configuration and may incorporate description of the preceding embodiments. In the prior embodiments, the patch portions were arranged in a row. Instead of this arrangement, the patch portions may be arranged in a plurality of rows. 
       FIG.  13    is a perspective view showing the antenna device  10  according to the present embodiment.  FIG.  13    corresponds to  FIG.  5   . As shown in  FIG.  13   , the antenna  40  includes a plurality of element rows  44  in which a plurality of elements are arranged in a line. The element row is sometimes referred to as an array row. Specifically, it includes four element rows  44 . Each of the element rows  44  has six patch portions  41 . The six patch portions  41  constituting one element row  44  are arranged side by side in the X direction with the above-mentioned predetermined intervals. The intervals adjacent to each other in the X direction are equal to each other in each element row  44 . The four element rows  44  are arranged side by side in the Y direction. The plurality of patch portions  41  are arranged in a grid pattern. 
     A plurality of waveguides  30  are provided in the substrate  20  corresponding to the element rows  44 . Specifically, four waveguides  30  are partitioned by the via conductors  330  that constitute the side wall portions  33 . Each of the waveguides  30  extends in the X direction. The four waveguides  30  are arranged side by side in the Y direction. The element rows  44  are arranged directly above the four waveguides  30 . Other configurations are the same as those described in the prior embodiments. 
     Summary of Fifth Embodiment 
       FIG.  14    shows the result of performing an electromagnetic field simulation on the antenna device  10  shown in  FIG.  13   . The simulation conditions are the same as those in  FIGS.  7  and  8    except that the number of elements was different. In this simulation, the operating frequency is 82.3 GHz and the dielectric constant is 3.6. 
     As shown in  FIG.  14   , the maximum gain was 13.3 dBi. As described above, by increasing the number of elements not only in the X direction but also in the Y direction, the maximum gain of the antenna  40  is further improved. Further, the antenna  40  shows directivity in the X direction. 
     The number of patch portions  41  constituting one element row  44  is not limited to six. Further, the number of element rows  44  is not limited to four. 
     SIXTH EMBODIMENT 
     The second embodiment is a modification of the preceding embodiment as a basic configuration and may incorporate description of the preceding embodiments. 
       FIG.  15    is a perspective view showing the antenna device  10  according to the present embodiment.  FIG.  15    corresponds to  FIG.  13   . As shown in  FIG.  15   , the antenna device  10  includes a phase unit  60 . The phase unit  60  is individually provided with respect to the waveguide  30 . The phase unit  60  adjusts the phase of the current flowing through the element row  44  of the antenna  40 . The antenna  40  provided with the phase unit  60  is sometimes referred to as a phased array antenna. 
     The waveguide  30  has a configuration in which both ends in the X direction are closed by the via conductors  330 . In each waveguide  30 , the opening  35  is formed in the lower wall portion  32 . The opening  35  is formed on one end side of the waveguide  30  in the X direction. The opening  35  penetrates the lower wall portion  32  in the Z direction. The phase unit  60  is connected to the waveguide  30  through the opening  35 . Other configurations are the same as those described in the prior embodiments. 
     Summary of Sixth Embodiment 
       FIG.  16    shows the result of performing an electromagnetic field simulation on the antenna device  10  shown in  FIG.  15   .  FIG.  16    shows the radiation directivity along the XY plane. The simulation conditions are the same as in  FIG.  13   .  FIG.  16    shows the results when the phases of the four element rows  44  are the same, when the phases are shifted by 15 degrees, and when the phases are shifted by −15 degrees. 
     As shown in  FIG.  16   , in the case of the same phase, the radiation direction of the main beam is the X direction. By shifting the phase, the radiation direction of the main beam can be shifted to the left or right with reference to the radiation direction of the same phase. In this way, the beam can be directed in an arbitrary direction by adjusting the phase of the current flowing through each element row  44  of the antenna  40 . 
     OTHER EMBODIMENTS 
     The disclosure in this specification and drawings is not limited to the exemplified embodiments. The disclosure encompasses the illustrated embodiments and modifications by those skilled in the art based thereon. For example, the disclosure is not limited to the combinations of components and/or elements shown in the embodiments. The disclosure may be implemented in various combinations. The disclosure may have additional portions that may be added to the embodiments. The disclosure encompasses omission of components and/or elements of the embodiments. The disclosure encompasses the replacement or combination of components and/or elements between one embodiment and another. The disclosed technical scope is not limited to the description of the embodiments. It should be understood that some disclosed technical ranges are indicated by description of claims, and includes every modification within the equivalent meaning and the scope of description of claims. 
     The disclosure in the specification, drawings and the like is not limited by the description of the claims. The disclosures in the specification, the drawings, and the like encompass the technical ideas described in the claims, and further extend to a wider variety of technical ideas than those in the claims. Therefore, various technical ideas can be extracted from the disclosure of the specification, the drawings and the like without being limited to the description of the claims. 
     When an element or a layer is described as “disposed above” or “connected”, the element or the layer may be directly disposed above or connected to another element or another layer, or an intervening element or an intervening layer may be present therebetween. In contrast, when an element or a layer is described as “disposed directly above” or “directly connected”, an intervening element or an intervening layer is not present. Other terms used to describe the relationships between elements (for example, “between” vs. “directly between”, and “adjacent” vs. “directly adjacent”) should be interpreted similarly. As used herein, the term “and/or” includes any combination and all combinations relating to one or more of the related listed items. For example, the term A and/or B includes only A, only B, or both A and B. 
     Spatial relative terms “inside”, “outside”, “back”, “bottom”, “low”, “top”, “high”, etc. are used herein to facilitate the description that describes relationships between one element or feature and another element or feature. Spatial relative terms can be intended to include different orientations of a device in use or operation, in addition to the orientations depicted in the drawings. For example, when the device in the figure is flipped over, an element described as “below” or “directly below” another element or feature is directed “above” the other element or feature. Therefore, the term “below” can include both above and below. The device may be oriented in the other direction (rotated 90 degrees or in any other direction) and the spatially relative terms used herein are interpreted accordingly. 
     An example including the inner layer pattern  51  and the via conductor  55  as the matching portion  50  arranged between the upper wall portion  31  and the lower wall portion  32  has been shown, but the present disclosure is not limited thereto. The configuration may include only the inner layer pattern  51 . That is, the matching portion  50  may be arranged between the upper wall portion  31  and the lower wall portion  32  and may not be connected to the lower wall portion  32 . 
     An example is shown in which the feeding line  42  including the matching portion  50  is connected to the lower wall portion  32 , but the present disclosure is not limited to this configuration. As described above, the feeding line  42  and/or the feeding line  42  including the matching portion  50  is extended below the center of the height of the waveguide  30  for feeding from the waveguide  30 . For example, in the configuration shown in  FIG.  10   , the feeding line  42  may not be connected to the lower wall portion  32 .