Patent Publication Number: US-2023163454-A1

Title: Communication device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application of International Patent Application No. PCT/JP2021/017898, filed May 11, 2021, which claims priority to Japanese Patent Application No. 2020-136777, filed Aug. 13, 2020, the entire contents of each of which being incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a communication device, and more particularly, to a technique for stabilizing antenna characteristics in a communication device including a patch antenna. 
     BACKGROUND ART 
     Japanese Unexamined Patent Application Publication No. 2017-40497 (Patent Document 1) discloses an impact-resistant structure for protecting a patch antenna disposed inside an electronic apparatus such as a satellite radio-controlled clock from an impact caused by dropping or the like. In Japanese Unexamined Patent Application Publication No. 2017-40497 (Patent Document 1), between a patch antenna and a holding member, a gap is formed in which relief portions are formed at a side corner portion and an end corner portion of the patch antenna. When an impact is applied to the electronic apparatus and the patch antenna is caused to relatively move inside the electronic apparatus, the relief portion avoids collision of the holding member with the side corner portion and the end corner portion of the patch antenna. Further, by providing a gently protruding shape to a surface portion of the holding member, a collision area is increased when the surface portion of the holding member collides with a planar region of the patch antenna. This makes it possible to distribute the stress applied to the patch antenna. With the configurations above, the patch antenna may be prevented from being damaged. 
     CITATION LIST 
     Patent Document 
     
         
         Patent Document 1: Japanese Unexamined Patent Application Publication No. 2017-40497 
       
    
     SUMMARY 
     Technical Problems 
     In an electronic apparatus having a communication function, a cover member that covers an antenna module is provided in many cases. Such a cover member corresponds to an impact-resistant holding member as disclosed in Japanese Unexamined Patent Application Publication No. 2017-40497 (Patent Document 1), a housing of an electronic apparatus main body, or the like. 
     In a case that a wide space is formed between a radiation surface of a radiating element in an antenna module and a cover member, when the cover member is deformed, a dielectric constant in a radiation direction of a radio wave changes, and thus, an antenna frequency changes. Among other things, this raises a possibility that desired antenna characteristics cannot be achieved. 
     Accordingly, it is desirable to dispose a member between the cover member and the radiating element so that a gap between the cover member and the radiating element is constant. However, when a member is disposed to widely cover a radiating element, to the contrary, there is a possibility that the antenna characteristics deteriorate because of an antenna frequency change or impact resistance deteriorates. 
     The present disclosure has been made to solve such a problem, as well as other problems, and an aspect of the disclosure is to make a separation between a cover member and a radiating element constant while suppressing deterioration of antenna characteristics in a communication device. 
     Solutions to Problems 
     Among other things, the present disclosure describes a communication device that includes a dielectric substrate, a radiating element that has a flat shape and that is disposed on the dielectric substrate, a cover member that covers the dielectric substrate, and a pressing member. The pressing member is disposed in contact with the cover member and the dielectric substrate and projects from an inner surface of the cover member toward the first radiating element. A feed point, to which a radio frequency signal is supplied from a feed circuit, is formed on the radiating element. In a plan view from a normal direction of the dielectric substrate, the pressing member and the dielectric substrate are in contact with each other in a center surface portion relative to the feed point of the radiating element. 
     Advantageous Effects 
     With the use of the communication device according to the present disclosure, a pressing member and a dielectric substrate disposed between a cover member and a radiating element are in contact with each other in a center side region relative to a feed point of the radiating element. Since electric field strength at a center portion of a radiating element is weaker than that at a peripheral portion, when a pressing member is in contact with the center portion, an influence on impedance of a radiating element is small. Accordingly, it is possible to make a distance between a cover member and a radiating element constant while suppressing the deterioration of antenna characteristics. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a block diagram of a communication device according to an Embodiment. 
         FIG.  2    is a sectional view and a plan view of an antenna module in the communication device of  FIG.  1   . 
         FIG.  3    is a diagram and a graph for explaining an influence of rib disposition on a return loss. 
         FIG.  4    is a diagram illustrating an example of rib disposition in an array antenna. The diagram includes three subparts ( 4 ( a ),  4 ( b ), and  4 ( c )), and therefore sometimes referred to as  FIG.  4 ( a ) ,  FIG.  4 ( b ) , and  FIG.  4 ( c ) . 
         FIG.  5    is a graph for explaining a gain in the example of  FIG.  4   . 
         FIG.  6    is a sectional view of a communication device of Modification 1. 
         FIG.  7    is a sectional view of a communication device of Modification 2. 
         FIG.  8    is a sectional view of a communication device of Modification 3. 
         FIG.  9    is a sectional view of a communication device of Modification 4. 
         FIG.  10    is a sectional view of a communication device of Modification 5. 
         FIG.  11    is a sectional view of a communication device of Modification 6. 
         FIG.  12    is a sectional view of a communication device of Modification 7. 
         FIG.  13    is a sectional view of a communication device of Modification 8. 
         FIG.  14    is a sectional view of a communication device of Modification 9. 
         FIG.  15    is a sectional view of a communication device of Modification 10. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. Note that the same or corresponding portions in the drawings are denoted by the same reference signs, and a description thereof will not be repeated. 
     [Basic Configuration of Communication Device] 
       FIG.  1    is an example of a block diagram of a communication device  10  according to the present embodiment. The communication device  10  is a mobile terminal such as a mobile phone, a smartphone, or a tablet; a personal computer having a communication function; a base station; or the like, for example. An example of a frequency band of a radio wave used in an antenna module  100  according to the present embodiment is a radio wave in a millimeter wave band whose center frequency is 28 GHz, 39 GHz, 60 GHz, or the like, for example. However, a radio wave in a frequency band other than the above may be adopted. 
     Referring to  FIG.  1   , the communication device  10  includes the antenna module  100  and a BBIC  200  constituting a baseband signal processing circuit. The antenna module  100  includes an RFIC  110  being an example of a feed circuit and an antenna unit  120 . The communication device  10  up-converts a signal, which is transferred from the BBIC  200  to the antenna module  100 , into a radio frequency signal and radiates the radio frequency signal from the antenna unit  120 ; and down-converts a radio frequency signal received by the antenna unit  120  and processes the down-converted signal in the BBIC  200 . 
     In  FIG.  1   , for facilitating the explanation, only a configuration corresponding to four radiating elements  121  among the multiple radiating elements  121  constituting the antenna unit  120  is illustrated, and a configuration corresponding to other radiating elements  121  having the same configuration is omitted. Although  FIG.  1    illustrates an example in which the antenna unit  120  is formed by the multiple radiating elements  121  arranged in a two-dimensional array, the number of radiating elements  121  is not necessarily plural, and the antenna unit  120  may be formed by one radiating element  121 . Alternatively, a one-dimensional array in which the multiple radiating elements  121  are arranged in a line may be used. In the present embodiment, the radiating element  121  is described taking a patch antenna having a substantially square flat shape as an example, but the shape of the radiating element  121  may be a circle, an ellipse, or other polygons such as a hexagon. 
     The RFIC  110  includes switches  111 A to  111 D,  113 A to  113 D, and  117 , power amplifiers  112 AT to  112 DT, low-noise amplifiers  112 AR to  112 DR, attenuators  114 A to  114 D, phase shifters  115 A to  115 D, a signal combiner/divider  116 , a mixer  118 , and an amplifier  119 . 
     When a radio frequency signal is transmitted, the switches  111 A to  111 D and  113 A to  113 D are changed over to the power amplifiers  112 AT to  112 DT side, and the switch  117  is connected to a transmission side amplifier of the amplifier  119 . When a radio frequency signal is received, the switches  111 A to  111 D and  113 A to  113 D are changed over to the low-noise amplifiers  112 AR to  112 DR side, and the switch  117  is connected to a reception side amplifier of the amplifier  119 . 
     A signal transferred from the BBIC  200  is amplified by the amplifier  119  and up-converted by the mixer  118 . A transmission signal, which is an up-converted radio frequency signal, is divided into four signals by the signal combiner/divider  116 , then the four signals pass through four signal paths, and are respectively fed to the radiating elements  121  different from each other. At this time, the directivity of the antenna unit  120  may be adjusted by individually adjusting a phase shift degree in each of the phase shifters  115 A to  115 D disposed in the respective signal paths. Further, the attenuators  114 A to  114 D adjust the intensity of a transmission signal. 
     Reception signals, which are radio frequency signals received by the radiating elements  121 , respectively pass through four different signal paths, and are combined by the signal combiner/divider  116 . The combined reception signal is down-converted by the mixer  118 , amplified by the amplifier  119 , and transferred to the BBIC  200 . 
     The RFIC  110  is formed as a single-chip integrated circuit component including the above-described circuit configuration, for example. Alternatively, devices (switch, power amplifier, low-noise amplifier, attenuator, and phase shifter) corresponding to each radiating element  121  in the RFIC  110  may be formed as a single-chip integrated circuit component for each corresponding radiating element  121 . 
     [Configuration of Antenna Module] 
       FIG.  2    includes a sectional view ( FIG.  2 (A) ) and a plan view ( FIG.  2 (B) ) of the antenna module  100  in the communication device  10  of  FIG.  1   . Referring to  FIG.  2   , in the communication device  10 , the antenna module  100  is accommodated in a housing  50 . 
     The antenna module  100  includes a dielectric substrate  130 , a ground electrode GND, and feed wirings  141  and  142 , in addition to the radiating element  121  and the RFIC  110 . Note that  FIG.  2    illustrates an example of a configuration in which the antenna module  100  includes two radiating elements  121 , but the number of radiating elements  121  may be one or three or more. Further, the number of feed points of the radiating element  121  may be one, and in that case, the number of feed wirings is also one. In the following description, a thickness direction of the antenna module  100  is defined as a Z-axis direction, and a plane perpendicular to the Z-axis direction is defined as an X-axis and a Y-axis. Further, in each drawing, a positive direction of the Z-axis is referred to as an upper surface side, and a negative direction thereof is referred to as a lower surface side in some cases. 
     The dielectric substrate  130  is, for example, a low temperature co-fired ceramics (LTCC) multilayer substrate, a multilayer resin substrate formed by laminating multiple resin layers configured of resin such as epoxy or polyimide, a multilayer resin substrate formed by laminating multiple resin layers configured of liquid crystal polymer (LCP) having a lower dielectric constant, a multilayer resin substrate formed by laminating multiple resin layers configured of fluororesin, a multilayer resin substrate formed by laminating multiple resin layers configured of a polyethylene terephthalate (PET) material, or a ceramics multilayer substrate other than LTCC. Note that the dielectric substrate  130  does not necessarily have a multilayer structure, and may be a single-layer substrate. 
     The dielectric substrate  130  has a substantially rectangular shape in a plan view from a normal direction (Z-axis direction), and the radiating element  121  is disposed on an upper surface  131  (surface in the positive direction of the Z-axis) thereof. In  FIG.  2   , the two radiating elements  121  are adjacently arranged along the X-axis. Further, the ground electrode GND is disposed on a layer of a lower surface  132  side of the dielectric substrate  130  so as to face the radiating element  121 . The radiating element  121  may have an aspect to be exposed on the upper surface  131  of the dielectric substrate  130  as in the example of  FIG.  2   , or may be disposed on an inner layer of the dielectric substrate  130  near the upper surface  131 . 
     The RFIC  110  is mounted on the lower surface  132  of the dielectric substrate  130  via solder bumps  150 . Note that the RFIC  110  may be connected to the dielectric substrate  130  using a multi-pole connector instead of a solder connection. 
     A radio frequency signal is transferred from the RFIC  110  to each of the radiating elements  121  via the feed wirings  141  and  142 . The feed wiring  141  penetrates through the ground electrode GND from the RFIC  110 , and is connected to a feed point SP 1  from a lower surface side of the radiating element  121 . Further, the feed wiring  142  penetrates through the ground electrode GND from the RFIC  110 , and is connected to a feed point SP 2  from the lower surface side of the radiating element  121 . 
     In each of the radiating elements  121 , the feed point SP 1  is formed at a position offset from a center of the radiating element  121  in a positive direction of the Y-axis. When a radio frequency signal is supplied to the feed point SP 1 , a radio wave having a polarization direction in the Y-axis direction is radiated from the radiating element  121 . Further, the feed point SP 2  is formed at a position offset from the center of the radiating element  121  in a negative direction of the X-axis. When a radio frequency signal is supplied to the feed point SP 2 , a radio wave having a polarization direction in the X-axis direction is radiated from the radiating element  121 . That is, the antenna module  100  is a dual-polarization type antenna module capable of radiating radio waves in two different polarization directions. 
     The antenna module  100  is disposed inside the housing  50  such that a distance GP between the dielectric substrate  130  and the housing  50  is a predetermined distance. A pressing member (e.g., rib, protrusion, bump, or ridge)  51  that protrudes from an inner surface of the housing (e.g., cover)  50  is formed in the housing  50 . A tip portion of the rib  51  is formed in a conical shape or a spherical shape. The tip of the rib  51  is in contact with the dielectric substrate  130  in a region RG 1  near the center of the radiating element  121  in a plan view from a normal direction of the dielectric substrate  130 . The region RG 1  is a region near the center of the radiating element  121  relative to the feed points SP 1  and SP 2 , and is indicated by a broken line portion in a plan view of  FIG.  2 (B) . Note that as illustrated in  FIG.  2 (B) , the region RG 1  may be a region inside a quadrangle whose apexes are the feed points SP 1  and SP 2 , or may be a region inside a circle whose radius is a distance from the center of the radiating element  121  to the feed point. Further, a contact region between the rib  51  and the dielectric substrate  130  may slightly swell out from the region RG 1 . 
     The housing  50  of the communication device  10  may more or less be deformed by force applied from an outside. When the housing  50  deforms, the distance GP between the housing  50  and the dielectric substrate  130  varies, and a dielectric constant in a radiation direction of a radio wave may vary. A resonant frequency of the radiating element varies due to a variation in the dielectric constant, and there may arise a case that desired antenna characteristics cannot be realized. 
     In the communication device  10  with the configuration of the present embodiment, since the rib  51  formed on the housing  50  can suppress a variation in the distance GP between the dielectric substrate  130  and the housing  50 , the deterioration of antenna characteristics may be prevented. Further, since the radiating element  121  is pressed by the rib  51 , the separation of the radiating element  121  from the dielectric substrate  130  may also be suppressed. 
       FIG.  3    is a diagram and a graph for explaining an influence of the disposition of the rib  51  on a return loss of an antenna module. In  FIG.  3   , with respect to an antenna module  100 A of a one-dimensional array in which four radiating elements  121 A to  121 D are arranged in a line (upper column), compared are the return losses due to the presence or absence of the rib  51  and due to a difference in a pressing position of the rib  51  (lower column). In the antenna module  100 A, the sides of the substantially square radiating element  121  are disposed to be inclined by 45° relative to the X-axis and the Y-axis, and the two polarization directions are also inclined by 45° relative to the X-axis and the Y-axis. Note that,  FIG.  3    illustrates an example of a simulation result in a case that a target frequency band is a 39 GHz band. 
     In the middle column of  FIG.  3   , variations (comparative examples) of the pressing position of the rib  51  are illustrated. Comparative Example 1 is an example of a case that no rib  51  is disposed. Comparative Example 2 is an example of a case that the ribs  51  are disposed so that the radiating element  121  is pressed in regions RG 2  along the Y-axis. Comparative Example 3 is an example of a case that the ribs  51  are disposed so that the radiating element  121  is pressed in cross-shaped regions RG 3  passing through the center of the radiating element  121 . Comparative Example 4 is an example of a case that the rib  51  is disposed so that a region RG 4  being an outer peripheral edge of the radiating element  121  is pressed. 
     In the graph illustrating the return loss in the lower column of  FIG.  3   , the case of the present embodiment is indicated by a solid line LN 10 , and the case of Comparative Example 1 is indicated by a broken line LN 11 . Further, Comparative Example 2 to Comparative Example 4 are respectively indicated by a dash-dotted line LN 12 , an alternate long and two short dashes line LN 13 , and a dash-dotted line LN 14 . Note that in  FIG.  3   , variations of the frequency exhibiting a return loss minimum value, in the present embodiment and other Comparative Example 2 to Comparative Example 4, are compared with that in Comparative Example 1 in which no rib is provided as a reference. 
     Referring to  FIG.  3   , the return loss minimum values occur at resonant frequencies f 1  and f 2  in the case of Comparative Example 1 in which no rib is disposed, and the return loss minimum values occur at substantially the same frequencies also in the case of the present embodiment. On the other hand, in the cases of Comparative Example 2 to Comparative Example 4, the minimum values corresponding to the resonant frequencies f 1  and f 2  are both shifted to a lower frequency side. This means that impedance varies under the influence of the electric field strength of the radiating element  121 , and as a result, the resonant frequency shifts. 
     As in the present embodiment, by bringing the rib  51  and the radiating element  121  into contact with each other avoiding the end portion of the radiating element  121  where the electric field strength becomes large, the influence of the rib  51  on the antenna characteristics may be minimized. 
     Next, with reference to  FIG.  4    and  FIG.  5   , in the communication device including the antenna module  100 A having the four radiating elements  121 A to  121 D illustrated in  FIG.  3   , the influence on the directivity when the number of ribs  51  pressing the radiating elements  121  is changed will be described. 
       FIG.  4 (A)  is a sectional view of a communication device  10 X being a comparative example in which no rib  51  is formed.  FIG.  4 (B)  is a sectional view of a communication device  10 A in which the ribs  51  are formed so as to press the radiating elements  121 A and  121 D at both ends. Further,  FIG.  4 (C)  is a sectional view of a communication device  10 B in which the ribs  51  are formed so as to press all of the four radiating elements  121 A to  121 D. 
       FIG.  5    is a graph illustrating a peak gain in a case that the normal direction (Z-axis direction, that is, 0° direction) of the radiating element  121  is the radiation direction. The horizontal axis of  FIG.  5    represents an angle from the Z-axis direction to the X-axis direction, and the vertical axis represents the peak gain. In  FIG.  5   , a peak gain of the communication device  10 B is illustrated by a solid line LN 20 , a peak gain of the communication device  10 A is illustrated by a broken line LN 21 , and a peak gain of the communication device  10 X of the comparative example is illustrated by a dash-dotted line LN 22 . Note that  FIG.  5    is also a simulation result in a case that the target frequency band is the 39 GHz band. 
     Referring to  FIG.  5   , in the three communication devices illustrated in  FIG.  4   , the peak gain in the radiation direction of the communication device  10 B (solid line LN 20 ) is the largest. Further, as the angle from the radiation direction increases, the peak gain of the communication device  10 B becomes smaller than those of other communication devices. That is, it can be seen that a “lens effect” in which energy is concentrated in the radiation direction is obtained by disposing the ribs  51  corresponding to the respective radiating elements  121 . 
     The communication device  10 A (broken line LN 21 ), in which the ribs  51  are formed on the radiating elements  121 A and  121 D at both ends, has intermediate characteristics between those of the communication device  10 B and the communication device  10 X of the comparative example. Thus, the lens effect of a gain tends to increase as the number of radiation electrodes increases on which the ribs  51  are disposed. 
     As described above, in a communication device, by disposing a rib formed on a housing to be in contact with the dielectric substrate at a center portion of a radiating element where electric field strength becomes weak, deformation of the housing may be reduced while an influence on impedance is suppressed. With this, a distance between the housing and the radiating element may be made constant while suppressing the deterioration of antenna characteristics. 
     Further, in an array antenna in which multiple radiating elements are arranged in an array, gain characteristics may be improved by disposing ribs for more radiating elements. 
     Note that a configuration has been described above in which ribs are disposed between a housing of a communication device main body and an antenna module. However, in a case that, inside a housing, an antenna module is covered with a case or a protective cover, ribs may be disposed between the case or the cover and the antenna module. The above-described “housing”, “case”, and “cover” correspond to “cover member” in the present disclosure. 
     [Modifications] 
     In the following description, modifications of a shape of a dielectric substrate on which a radiating element is formed and a disposition of a rib will be described. 
     (Modification 1) 
       FIG.  6    is a sectional view of a communication device  10 C of Modification 1. An antenna module  100 C illustrated in  FIG.  6    has a configuration in which the dielectric substrate  130  in the antenna module  100  described in  FIG.  2    is replaced with a dielectric substrate  130 C. In  FIG.  6    and  FIG.  7    to  FIG.  15    to be described later, the description of elements overlapping with  FIG.  2    will not be repeated. Further, In  FIG.  6    to  FIG.  15   , the RFIC  110 , the ground electrode GND, and the feed wirings  141  and  142  are omitted. 
     Referring to  FIG.  6   , in the antenna module  100 C of Modification 1, a recess  135  is formed at a portion of the dielectric substrate  130 C facing the rib  51  of the housing  50 , and the radiating element  121  is disposed at a bottom portion of the recess  135 . Then, inside the recess  135 , the rib  51  formed on the housing  50  is in contact with the radiating element  121 . In the same manner as in  FIG.  2   , the rib  51  is in contact with the radiating element  121  in a center side region (region RG 1  in  FIG.  2   , where the center side region is also referred to as a center surface portion) relative to the feed point of the radiating element  121 . 
     With such a configuration, a portion of the dielectric substrate  130 C around the recess  135  may be used as a region for disposing a wiring, a filter, or the like. Thus, the degree of layout freedom in a dielectric substrate may be increased. Further, since the rib  51  of the housing  50  enters the recess  135 , positional deviation between the antenna module and the housing  50  may be suppressed. 
     (Modification 2) 
       FIG.  7    is a sectional view of a communication device  10 D of Modification 2. An antenna module  100 D illustrated in  FIG.  7    has a configuration in which the dielectric substrate  130  in the communication device  10  described in  FIG.  2    is replaced with a dielectric substrate  130 D. 
     Referring to  FIG.  7   , in the antenna module  100 D of Modification 2, a recess  136  is formed at a portion of the dielectric substrate  130 D facing the rib  51  of the housing  50 , and the radiating element  121  is disposed at a bottom portion of the recess  136 . With this, in the same manner as in Modification 1, the degree of layout freedom in a dielectric substrate may be increased. 
     Further, in the recess  136 , a surface facing the housing  50  is formed in a spherical shape centered on the center of the radiating element  121 , and the radius of curvature of the spherical surface of the recess  136  is larger than the radius of curvature of a tip end of the rib  51 . With such a shape, the positioning of the tip end of the rib  51  at a center portion of the recess  136  becomes easier, and the positioning of the rib  51  and the radiating element  121  may further be facilitated. 
     (Modification 3) 
       FIG.  8    is a sectional view of a communication device  10 E of Modification 3. An antenna module  100 E illustrated in  FIG.  8    has a configuration in which the dielectric substrate  130  in the communication device  10  described in  FIG.  2    is replaced with a dielectric substrate  130 E. 
     Referring to  FIG.  8   , in the antenna module  100 E of Modification 3, a protrusion  137  is formed at a portion of the dielectric substrate  130 E facing the rib  51  of the housing  50 , and the radiating element  121  is disposed on an upper surface of the protrusion  137 . Then, the rib  51  formed on the housing  50  is in contact with the radiating element  121  on the protrusion  137 . 
     Although omitted in  FIG.  8   , the RFIC  110  is mounted in some cases on the dielectric substrate  130 E as illustrated in  FIG.  2   . Since a power amplifier and a low-noise amplifier are included in the RFIC  110 , heat may be generated during transmission operation and reception operation of a radio wave. In the communication device  10 E of Modification 3, a gap, between the dielectric substrate  130 E and the housing  50  at a portion other than the protrusion  137  where the radiating element  121  is disposed, is wider than that of the dielectric substrate  130  of  FIG.  2   . This makes it possible to enhance a cooling effect of the dielectric substrate  130 E. 
     Further, as compared with the dielectric substrate  130  of  FIG.  2   , since the amount of the dielectric material in the dielectric substrate is reduced, an effective dielectric constant may be decreased. With this, the frequency band width of a radiated radio wave may be expanded. 
     (Modification 4) 
       FIG.  9    is a sectional view of a communication device  10 F of Modification 4. The communication device  10 F illustrated in  FIG.  9    has a configuration in which a space portion, between the dielectric substrate  130  and the housing  50  of the communication device  10  described in  FIG.  2   , that is, the periphery of the rib  51 , is filled with a resin layer  160 . With such a configuration, the variation in the distance between the housing  50  and the dielectric substrate  130  may further be decreased. 
     Note that, in a case that an end portion of the radiating element  121  is supported by a dielectric, the antenna characteristics are likely to be affected as illustrated in  FIG.  3   . Thus, the resin layer  160  is preferably made of a material having a dielectric constant lower than the dielectric constant of the rib  51  and the dielectric constant of the dielectric substrate  130 . 
     (Modification 5) 
       FIG.  10    is a sectional view of a communication device  10 F 1  of Modification 5. The communication device  10 F of Modification 4 has a configuration in which the space portion between the dielectric substrate  130  and the housing  50  is filled with the resin layer  160  after the housing  50  is disposed on the dielectric substrate  130 . On the other hand, the communication device  10 F 1  of Modification 5 is provided with an intermediate layer  165  in which an opening  166  is formed at a portion corresponding to the radiating element  121 , and the housing  50  is disposed on the dielectric substrate  130  on which the intermediate layer  165  is formed. The intermediate layer  165  is a resist used as a protective film, for example. 
     The opening  166  of the intermediate layer  165  is formed to have a size corresponding to an outer shape of the rib  51  of the housing  50 , and the rib  51  can enter the opening  166 . By making the size of the opening  166  to be substantially the same as that of the rib  51 , movement of the rib  51  in the opening  166  is suppressed. Accordingly, the positional deviation in an XY plane of the housing  50  disposed on the radiating element  121  may be suppressed. 
     (Modification 6) 
       FIG.  11    is a sectional view of a communication device  10 G of Modification 6. In the communication device  10 G illustrated in  FIG.  11    has a configuration in which a rib  138  is formed on an antenna module  100 G instead of the rib  51  of the housing  50 . 
     The rib  138  is formed in a columnar shape, and is disposed in the center side region relative to the feed point of the radiating element  121  in a plan view from a normal direction of a dielectric substrate  130 G. Note that the rib  138  may be formed as part of the dielectric substrate  130 G or may be formed by attaching a member, different from the dielectric substrate  130 G, to the dielectric substrate  130 G. 
     Thus, even in the configuration in which a rib is formed on a dielectric substrate side, the rib is formed at the center portion of the radiating element where the electric field strength is relatively weak. This makes it possible to make the distance between the housing and the radiating element constant while suppressing the deterioration of antenna characteristics. 
     (Modification 7 to Modification 9) 
     With regard to Modification 7 to Modification 9, in an antenna module in which four or more radiating elements are formed, variations of rib disposition will be described in a case that the rib is formed for part of radiating elements. 
       FIG.  12    and  FIG.  13    are views of a communication device  10 H (Modification 7) and a communication device  10 I (Modification 8) respectively including antenna modules  100 H and  100 I in which four radiating elements  121 A to  121 D are one dimensionally arranged. 
     In the communication device  10 H of  FIG.  12   , the ribs  51  are formed corresponding to the radiating elements  121 A and  121 D at both ends, and no ribs  51  are formed for the inner side radiating elements  121 B and  121 C. On the other hand, in the communication device  10 I of  FIG.  13   , the ribs  51  are formed corresponding to the inner radiating elements  121 B and  121 C, and no ribs  51  are formed for the radiating elements  121 A and  121 D at both ends. 
     When attention is paid to mechanical strength of the housing  50 , the communication device  10 H supporting the housing  50  at both ends is more preferable than the communication device  10 I because the deformation of the housing  50  may be reduced. In the communication device  10 I, the deformation of the housing  50  near the radiating elements  121 A and  121 D at both ends tends to be large. 
     On the other hand, as described in  FIG.  5   , forming the ribs  51  increases the peak gain by the lens effect. When attention is paid to the gain characteristics, the lens effect becomes more remarkable when the ribs  51  are formed on the radiating elements  121 B and  121 C close to a center portion of an array antenna as in the communication device  10 I. Accordingly, the peak gain is increased more in the communication device  10 I than in the communication device  10 H. 
       FIG.  14    is a diagram of a communication device  10 J (Modification 9) including an antenna module  100 J in which five radiating elements  121 A to  121 E are one dimensionally arranged. In the communication device  10 J, the ribs  51  are formed corresponding to the radiating elements  121 A and  121 E at both ends, and the radiating element  121 C at the center, and no ribs  51  are formed for the radiating elements  121 B and  121 D. In other words, the ribs  51  are formed on every other radiating element. 
     With such a configuration, the gain characteristics near the center may be improved while maintaining the mechanical strength of a housing. Further, since a space between an antenna module and a housing can be ensured, a heat dissipation effect may be expected. 
     In a case that a greater number of radiating elements are arranged in an antenna module, ribs may be formed on every third radiating element, for example. Note that, in order to ensure the symmetry of radio waves radiated from an entire array antenna, it is preferable to symmetrically dispose ribs with respect to a radiating element. 
     As described above, in an antenna module in which multiple radiating elements are arranged in an array, the number and formation position of ribs may be determined in consideration of mechanical strength, gain characteristics, heat dissipation characteristics, and the like. 
     (Modification 10) 
       FIG.  15    is a sectional view of a communication device  10 K of Modification 10. In an antenna module  100 K of the communication device  10 K illustrated in  FIG.  15   , radiating elements  121  and  122  of sizes different from each other are arranged adjacent to each other. That is, the antenna module  100 K is a dual-band type antenna module capable of radiating radio waves in frequency bands different from each other. 
     The size of the radiating element  122  is larger than that of the radiating element  121 . Accordingly, a frequency band (second frequency band) of a radio wave radiated from the radiating element  122  is lower than a frequency band (first frequency band) of a radio wave radiated from the radiating element  121 . 
     Then, in the communication device  10 K, the rib  51  is formed for the radiating element  121  of a higher frequency side, and no rib  51  is formed for the radiating element  122  of a lower frequency side. In general, it is known that the following relational equation (1) is satisfied in the lens effect, when D is a spot diameter before entering a lens, d is a spot diameter after passing through the lens, f is a spot focal distance, and λ is a wavelength of a radio wave. 
         d= 4· f ·λ/(π· D )  (1)
 
     That is, as a wavelength of a radio wave becomes shorter, the spot diameter d after the passing becomes smaller, so that the lens effect becomes remarkable. Accordingly, in a dual-band type antenna module such as the antenna module  100 K, when it is necessary to form the ribs  51  thinning out for the heat dissipation characteristics, the ribs  51  are formed for the radiating elements of a relatively higher frequency side. This makes it possible to improve the heat dissipation characteristics while suppressing deterioration of the gain characteristics. 
     The “radiating element  121 ” and the “radiating element  122 ” in the present embodiment respectively correspond to a “first radiating element” and a “second radiating element” in the present disclosure. 
     It should be understood that the embodiment disclosed herein is illustrative in all respects and is not restrictive. The scope of the present invention is defined not by the above description of the embodiment but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. 
     REFERENCE SIGNS LIST 
       10 ,  10 A to  10 K,  10 F 1 ,  10 X COMMUNICATION DEVICE,  50  HOUSING,  51 ,  138  RIB,  100 ,  100 A,  100 C to  100 E,  100 G to  100 K ANTENNA MODULE,  110  RFIC,  111 A to  111 D,  113 A to  113 D,  117  SWITCH,  112 AR to  112 DR LOW-NOISE AMPLIFIER,  112 AT to  112 DT POWER AMPLIFIER,  114 A to  114 D ATTENUATOR,  115 A to  115 D PHASE SHIFTER,  116  SIGNAL COMBINER/DIVIDER,  118  MIXER,  119  AMPLIFIER,  120  ANTENNA UNIT,  121 ,  121 A to  121 E,  122  RADIATING ELEMENT,  130 ,  130 C to  130 E,  130 G DIELECTRIC SUBSTRATE,  135 ,  136  RECESS,  137  PROTRUSION,  141 ,  142  FEED WIRING,  150  SOLDER BUMP,  160  RESIN LAYER,  165  INTERMEDIATE LAYER,  166  OPENING,  200  BBIC, GND GROUND ELECTRODE, SP 1 , SP 2  FEED POINT