Patent Publication Number: US-2022216605-A1

Title: Antenna module, communication device mounted with the same, and circuit board

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application of International Patent Application No. PCT/JP2020/026388, filed Jul. 6, 2020, which claims priority to Japanese Patent Application No. 2019-177383, filed Sep. 27, 2019, the entire contents of each of which being incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to an antenna module and a communication device mounted with the antenna module and more particularly to a structure of an antenna module that improves antenna characteristics. 
     BACKGROUND ART 
     In Japanese Unexamined Patent Application Publication No. 2018-148290 (Patent Document 1), an antenna device in which a plurality of tabular radiation elements (patch antennas) are formed on a rectangular substrate is disclosed. 
     In such patch antennas as disclosed in Patent Document 1, a tabular ground electrode is provided so as to face the radiation elements and radio waves are radiated by way of electromagnetic field coupling between the radiation elements and the ground electrode. 
     CITATION LIST 
     Patent Document 
     Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-148290 
     SUMMARY 
     Technical Problems 
     Such an antenna device as disclosed in Japanese Unexamined Patent Application Publication No. 2018-148290 (Patent Document 1) is used in a portable terminal such as a cellular phone or a smartphone, for instance. For such a portable terminal, there are still great demands for reduction in size and thickness and further reduction in size of an antenna device built in the portable terminal is required accordingly. In recent years, particularly, there has been a tendency in which a region in a casing where the antenna device can be placed is restricted with enlargement of screens of smartphones and thus the antenna device may be placed in a narrow region on a side face of the casing, for instance. 
     In order to attain desired antenna characteristics in a patch antenna, ideally, it is necessary to provide a ground electrode having a sufficiently large area, compared with a radiation element. In case where the antenna device is placed in such a restricted narrow region as described above, however, it may be impossible to ensure the sufficiently large area of the ground electrode, compared with the radiation element. Meanwhile, it may be impossible to attain a symmetrical shape of the ground electrode, depending on an installation site of the antenna device or positional relation thereof with peripheral instruments. There is a fear, as recognized by the present inventors, that such restrictions on the size and shape of the ground electrode may cause turbulence of electric lines of force between the radiation elements and the ground electrode and may influence antenna characteristics such as gain, frequency band, or directivity. 
     The present disclosure has been made in order to solve such problems, as well as other problems, and aims at maintaining satisfactory antenna characteristics in an antenna module in which a patch antenna is formed and in which the size and/or shape of the ground electrode is restricted. 
     Solutions to the Problems 
     An antenna module according to a first aspect of the present disclosure includes a dielectric substrate including a plurality of dielectric layers that are laminated, and a radiation element, a ground electrode, and peripheral electrodes that are disposed in or on the dielectric substrate. The radiation element is configured to radiate radio waves in a first polarization direction. The ground electrode is positioned so as to face the radiation element. The peripheral electrodes are arranged in a plurality of layers between the radiation element and the ground electrode and are electrically connected to the ground electrode. The peripheral electrodes are symmetrically positioned with respect to at least one of a first direction parallel to the first polarization direction or a second direction orthogonal to the first polarization direction. 
     An antenna module according to a second aspect of the present disclosure includes a dielectric substrate including a plurality of dielectric layers that are laminated, and a first radiation element, a second radiation element, a ground electrode, and peripheral electrodes that are disposed in or on the dielectric substrate. The first radiation element and the second radiation element are positioned so as to adjoin each other. The ground electrode is positioned so as to face the first radiation element, and the second radiation element. The peripheral electrodes are arranged in a plurality of layers between the first radiation element and the ground electrode and a plurality of layers between the second radiation element and the ground electrode and are electrically connected to the ground electrode. The peripheral electrodes are symmetrically positioned with respect to at least one of a first direction parallel to a polarization direction of radiated radio waves or a second direction orthogonal to the polarization direction, for each of the first, radiation element and the second radiation element. 
     A circuit board according to a third aspect of the present disclosure is a device to feed radio frequency signals to a radiation element and includes a dielectric substrate including a plurality of dielectric layers that, are laminated, a ground electrode, and peripheral electrodes. The radiation element radiates radio waves in a first polarization direction. The ground electrode is positioned to face the radiation element. The peripheral electrodes are arranged in a plurality of layers between the radiation element and the ground electrode and are electrically connected to the ground electrode. The peripheral electrodes are symmetrically positioned with respect to at least one of a first direction parallel to the first polarization direction or a second direction orthogonal to the first polarization direction. 
     Advantageous Effects 
     In the antenna module and the circuit board according to the present disclosure, the peripheral electrodes electrically connected to the ground electrode are placed in the plurality of layers of the dielectric substrate between the radiation element and the ground electrode. Further, the peripheral electrodes are placed at the positions that are symmetrical with respect to at least either of the first direction parallel to the polarization direction of the radiation element and the second direction orthogonal to the first direction. By the placement of the peripheral electrodes at the positions that are symmetrical with respect to the radiation element, the electric lines of force generated in the radiation element can be homogenized in this manner and therefore the deterioration in the antenna characteristics on condition that the size and/or shape of the ground electrode is restricted can be suppressed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating a communication device to which an antenna module according to Embodiment 1 is applied. 
         FIG. 2  is a plan view of a first example of the antenna module according to Embodiment 1. 
         FIG. 3  is a perspective side view of the antenna module of  FIG. 2 . 
         FIG. 4  is a diagram for illustration of a state of electric lines of force between a radiation element and a ground electrode on condition that no peripheral electrodes are provided. 
         FIG. 5  is a diagram for illustration of a state of the electric lines of force between the radiation element and the ground electrode on condition that peripheral electrodes are provided. 
         FIG. 6  is a plan view of a second example of the antenna module according to Embodiment 1. 
         FIG. 7  is a perspective view of the antenna module of  FIG. 6 . 
         FIG. 8  is a diagram for illustration of antenna characteristics in accordance with presence or absence of the peripheral electrodes. 
         FIG. 9  is a diagram illustrating a first modification of placement of the peripheral electrodes. 
         FIG. 10  is a diagram illustrating a second modification of placement of the peripheral electrodes. 
         FIG. 11  is a perspective view of an antenna module according to Embodiment 2. 
         FIG. 12  is a plan view of a second substrate on condition that the antenna module of  FIG. 11  is seen from the X-axis direction. 
         FIG. 13  is a diagram for illustration of antenna characteristics in accordance with the presence or absence of the peripheral electrodes in Embodiment 2. 
         FIG. 14  is a plan view of an antenna module of Modification 1. 
         FIG. 15  is a plan view of an antenna module of Modification 2. 
         FIG. 16  is a plan view of an antenna module according to Embodiment 3. 
         FIG. 17  is a diagram for illustration of isolation of two polarizations in accordance with the presence or absence of the peripheral electrodes in Embodiment 3. 
         FIG. 18  is a plan view of an antenna module according to Embodiment 4. 
         FIG. 19  is a plan view of an antenna module of Modification 3. 
         FIG. 20  is a plan view of an antenna module of Modification 4. 
         FIG. 21  is a plan view of an antenna module according to Embodiment 5. 
         FIG. 22  is a perspective view of the antenna module of  FIG. 21 . 
         FIG. 23  is a diagram for illustration of gain characteristics of the antenna module of Embodiment 5. 
         FIG. 24  is a diagram for illustration of directivity of the antenna module of Embodiment 5. 
         FIG. 25  is a perspective side view of an antenna module according to Embodiment 6. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinbelow, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, identical components or corresponding components are provided with identical reference characters and description thereof will not be iterated. 
     Embodiment 1 
     (Basic Configuration of Communication Device) 
       FIG. 1  is an example of a block diagram illustrating a communication device  10  to which an antenna module  100  according to Embodiment  1  is applied. The communication device  10  is a portable terminal such as a cellular phone, a smartphone, or a tablet, a personal computer having a communication function, or the like, for instance. An example of a frequency band of radio waves to be used for the antenna module  100  according to the present embodiment is a millimeter waveband with a center frequency of 28 GHz, 39 GHz, 60 GHz, or the like, for instance, whereas application to radio waves of frequency bands other than the above may be made as well. 
     In reference to  FIG. 1 , the communication device  10  includes the antenna module  100  and a baseband integrated circuit (BBIC)  200  that forms a baseband signal processing circuit. The antenna module  100  includes a radio-frequency integrated circuit (RFIC)  110  as an example of a feed circuit and an antenna device  120 . The circuity of the communication device  10  up-converts signals, transferred from the BBIC  200  to the antenna module  100 , into radio frequency (RF) signals in the RFIC  110  and radiates the signals from the antenna device  120 . Additionally, the communication device  10  conveys radio frequency signals received by the antenna device  120  to the RFIC  110 , which then down-converts the RF signals before processing them in the BBIC  200 . 
     In  FIG. 1 , for facilitation of description, only configurations corresponding to four feed elements  121  among a plurality of feed elements (radiation elements)  121  that form the antenna device  120  are illustrated and configurations corresponding to the other feed elements  121  that, have a similar configuration are omitted. Though an example in which the antenna device  120  is formed of the plurality of feed elements  121  arranged, in shape of a two-dimensional array is illustrated in  FIG. 1 , a one-dimensional array in which the plurality of feed elements  121  are arranged in a line may be used. The antenna device  120  may also have a configuration in which a single feed element  121  is provided. In the embodiment, the feed elements  121  are patch antennas having tabular shapes (i.e., flat or planar, like a table-top). 
     The RFIC  110  includes switches  111 A to HID,  113 A to  113 D, and  117 , power amplifiers  112 AT to  112 DT, low-noise amplifiers  112 /AR to  112 DR, attenuators  114 A to  114 D, phase shifters  115 A to  115 D, a signal synthesizer/branching filter  116 , a mixer  118 , and an amplifier circuit  119 . 
     For transmission of the radio frequency signals, the switches  111 A to  111 D and  113 A to  113 D are switched to states that select the power amplifiers  112 AT to  112 D 7  and the switch  117  is connected to a transmitting-side amplifier in the amplifier circuit  119 . For reception of the radio frequency signals, the switches  111 A to HID and  113 A to  113 D are switched to states that select the low-noise amplifiers  112 AR to  112 DR and the switch  117  is connected to a receiving-side amplifier in the amplifier circuit  119 . 
     The signals transferred from the BBIC  200  are amplified by the amplifier circuit  119  and are up-converted by the mixer  118 . Transmission signals that are the up-converted radio frequency signals are branched into four parts by the signal synthesizer/branching filter  116 , are passed through four signal paths, and are respectively fed into the different feed elements  121 . Then, directivity of the antenna device  120  can be adjusted via individual phase adjustments made by the phase shifters  115 A to  115 D provided respectively in the signal paths. 
     Reception signals that are the radio frequency signals received by the feed elements  121  are respectively passed through the four different signal paths and are multiplexed by the signal synthesizer/branching filter  116 . The multiplexed reception signals are down-converted by the mixer  118 , are amplified by the amplifier circuit  119 , and are transferred to the BBIC  200 . 
     The RFIC  110  is formed as a one-chip integrated-circuit component including an above-described circuit configuration, for instance. Alternatively, circuitry components (switch, power amplifier, low-noise amplifier, attenuator, and phase shifter) corresponding to each of the feed elements  121  in the RFIC  110  may be separately, or in sub groups, formed as one-chip integrated-circuit component for the corresponding feed element  121 . 
     First Example 
     With reference to  FIG. 2  and  FIG. 3 , details of a configuration of the antenna module according to Embodiment 1 will be described.  FIG. 2  is a plan view of a first example of the antenna module  100  of Embodiment 1.  FIG. 3  is a perspective side view of the antenna module  100 . In the plan view of  FIG. 2 , dielectric layers are omitted so that inner electrodes may be seen. 
     In reference to  FIG. 2  and  FIG. 3 , the antenna module  100  includes a dielectric substrate  130 , feeder wiring  140  (the term “wiring” is used broadly to mean provide a conductive path), peripheral electrodes  150 , and ground electrodes GND 1  and GND 2 , in addition to the feed element  121  and the RFIC  110 . In following description, a normal direction (radiation direction of radio waves) with respect to the dielectric substrate  130  is defined as the Z-axis direction and a plane perpendicular to the Z-axis direction is defined by the X axis and the Y axis. In the drawings, a positive direction along the Z axis may be referred to as upside and a negative direction may be referred to as downside. 
     The dielectric substrate  130  is a low temperature co-fired ceramics (LTCC) multilayer substrate, a multilayer resin substrate that is formed of a lamination of a plurality of resin layers made of resin such as epoxy or polyimide, a multilayer resin substrate that is formed of a lamination of a plurality of resin layers made of liquid crystal polymer (LCP) having a lower permittivity, a multilayer resin substrate that is formed of a lamination of a plurality of resin layers made of fluorine-based resin, or a ceramics multilayer substrate other than LTCC, for instance. 
     The dielectric substrate  130  has a substantially rectangular shape arid has the feed element  121  placed in a layer (upside layer) near to a top surface  131  (surface facing in the positive direction along the Z axis) thereof. The feed element  121  may be embodied so as to be exposed on a surface of the dielectric substrate  130  or may be placed within an inner layer in the dielectric substrate  13 C as shown in the example of  FIG. 3 . Though the example in which only the feed elements are used as radiation elements is described as Embodiment I for facilitation of description, a configuration in which passive elements and/or parasitic elements are provided in addition to the feed elements may be adopted. 
     In a layer (downside layer) closer to a bottom surface  132  (surface facing in the negative direction along the Z axis) than the feed element  121  in the dielectric substrate  130 , the tabular (or flat) ground electrode GND 2  is placed so as to face the feed element  121 . The ground electrode GND 1  is placed in a layer between the feed element  121  and the ground electrode GND 2 . 
     A layer between the ground electrode GND 1  and the ground electrode GND 2  is used as a wiring region. In the wiring region, a wiring pattern  170  is placed, the wiring pattern  170  forming the feeder wiring to feed the radio frequency signals to the radiation element, stubs and filters to be connected to the feeder wiring, connection wiring to be connected to other electronic components, and the like. Once again “wiring” should be construed and a one or more electrically conductive paths, and not necessarily a “wire” of any particular gauge. Unnecessary coupling between the feed element  121  and the wiring pattern  170  can be suppressed by formation of the wiring region in the dielectric layer opposed to the feed element  121  with respect to the ground electrode GND 1  in this manner. 
     Below the bottom surface  132  of the dielectric substrate  130 , the RFIC  110  is mounted with solder bumps  100  interposed therebetween. The RFIC  110  may be connected to the dielectric substrate  130  with use of multi-pole connectors instead of solder connection. 
     The radio frequency signals are fed from the RFIC  110  through the feeder wiring  140  to a feeding point SP 1  of the feed element  121 . The feeder wiring  140  rises from the RFIC  110  through the ground electrode GND 2  and extends in the wiring region. Further, the feeder wiring  140  rises from immediately below the feed element  121  through the ground electrode GND 1  and is connected to the feeding point SRI of the feed element  121 . 
     In the example structure of  FIG. 2  and  FIG. 3 , the feeding point SP 1  of the feed element  121  is placed at a position offset from a center of the feed element.  121  in a positive direction along the Y axis. With placement of the feeding point SP 1  at such a position, radio waves having a polarization direction along the Y axis are radiated from the feed element  121 . 
     The peripheral electrodes  150  are formed in end portions of the dielectric substrate  130  and in a plurality of dielectric layers between the feed element  121  and the ground electrode GND 1 . In the antenna module  100 , the peripheral electrodes  150  are placed along sides of the rectangular feed element  121  in plan view from the normal direction (positive direction along the Z axis) with respect to the dielectric substrate  130 . The peripheral electrodes  150  placed along the sides are placed at positions that are symmetrical with respect to the polarization direction (Y-axis direction) of the feed element  121  and a direction (X-axis direction) orthogonal to the polarization direction. 
     In plan view of the dielectric substrate  130 , the peripheral electrodes  150  are placed  30  as to be overlaid in a direction of the lamination (i.e., a footprint of one peripheral electrode  150  at least partially overlaps ail others). That is, the peripheral electrodes  150  form a virtual conductor wall along the sides of the dielectric substrate  130 . The peripheral electrodes  150  adjoining in the direction of the lamination are electrically connected to each other by connecting conductors  151 , sometimes referred to as vias  151 . In this context, a “via” is a vertical structure extending between peripheral electrodes  150  and may be provided with an electrically conductive material so as to make an electrical connection between them. In this context the term “via” is a connecting conductor. Further, the peripheral electrodes  150  at bottom are electrically connected to the ground electrode GND 1  by the connecting conductors  151 . That is, the peripheral electrodes  150  substantially have a configuration equivalent to a configuration in which end portions of the ground electrode GND 1  are extended in the direction of the lamination. Incidentally, the peripheral electrodes  150  need not have an identical shape, and respective sizes of the electrodes may be increased with approximation to the ground electrode GND 1  in the direction of the lamination of the dielectric substrate  130 , for instance. 
     In the antenna module  100 , the connecting conductors  151  formed in the dielectric layers adjoining in the direction of the lamination are preferably placed so that successive connecting conductors  151  do not to overlap in plan view from the normal direction with respect to the dielectric substrate  130 . Moreover, as seen from a side view, cross-section, a set of connecting conductors  151  are staggered so a first connecting conductor  151  is on a first side, a next connecting conductor  151  is on the other side, and then the next connecting conductor  151  after that is on the first side, and so on. Electrical conducting material (copper, typically) forming the connecting conductors  151  exhibits smaller compressibility than dielectric material, when being pressurized. Therefore, when the dielectric substrate  130  is pressed for pressure bonding of the dielectric layers in case where all the connecting conductors  151  in the layers are placed at the same positions in plan view from the normal direction with respect to the dielectric substrate  130 , portions made of the connecting conductors  151  exhibit a smaller rate of decrease in thickness, compared with other dielectric portions, which may cause a variation in thickness in the entire dielectric substrate  130 . Thus accuracy in thickness of the dielectric substrate  130  having undergone forming can be increased by placement of the connecting conductors  151  in the dielectric layers adjoining in the direction of the lamination in different positions as described above. 
     Electrical connections between the peripheral electrodes  150  themselves, and between the peripheral electrodes  150  and the ground electrode GND 1  are not limited to direct connections through the connecting conductors  151  and may include a configuration in which some or all of the connections are attained by capacitance coupling. 
     From a patch antenna including such a tabular radiation element, radio waves are radiated by way of electromagnetic field coupling between the radiation element and the ground electrode. In order to attain desired antenna characteristics, the ground electrode has a sufficiently large area, compared with the radiation element. 
     On the other hand, for portable terminals such as cellular phones or smartphones in which patch antennas are used, there are still great demands for reduction in size and thickness, so that further reduction in size of antenna devices built in the portable terminals is required. 
     In a situation where the antenna device is placed in a limited space in a casing, however, it may be impossible to ensure the sufficiently large area of the ground electrode, compared with the radiation element. Meanwhile, it may be impossible to attain a symmetrical shape of the ground electrode, depending on an installation site of the antenna device or positional relation thereof with peripheral instruments. There is a concern that such restrictions on the size and shape of the ground electrode may cause turbulence of electric lines of force between the radiation element and the ground electrode and may influence the antenna characteristics such as gain, frequency band, or directivity. 
       FIG. 4  is a diagram for illustration of a state of the electric lines of force (electric field lines) between the radiation element and the ground electrode in case where a sufficient area of the ground electrode cannot be ensured, compared with the radiation element. When radio frequency signals are fed to the feed element  121  (radiation element), the electromagnetic field coupling is brought about between end portions of the feed element  121  and the ground electrode GND 1 . Then electric lines of force are emitted from one end portion of the feed element  121  to the ground electrode GND 1  and the other end portion receives electric lines of force from the ground electrode GND 1 . 
     In a case where the ground electrode GND 1  has a sufficiently large area compared with the feed element  121 , electric lines of force are given and received on a surface of the ground electrode GND 1  facing the feed element  121 . In case where the sufficient area of the ground electrode GND 1  cannot be ensured, however, a portion of the electric lines of force may go around onto a back surface of the ground electrode GND 1 , as illustrated in  FIG. 4 . In such a case, increase in a proportion of radio waves radiated to a back surface side of the antenna device may cause deterioration in antenna gain in a desired direction due to a disturbance in the directivity, decrease in a frequency bandwidth, or variation in the polarization direction, like circular polarization. 
     In the antenna module  100  of Embodiment 1, the peripheral electrodes  150  electrically connected to the ground electrode GND 1  are placed in the layers between the feed element  121  and the ground electrode GND 1 , as in  FIG. 5 . Distances between the peripheral electrodes  150  and the feed element  121  are shorter than a distance between the ground electrode GND 1  and the feed element  121  and thus the peripheral electrodes  150  are higher in degree of the electromagnetic field coupling with the feed element  121  than the ground electrode GND 1 . Accordingly, the electric lines of force that, would otherwise go around onto the back surface side of the ground electrode GND 1  in  FIG. 4  are generated toward and from the peripheral electrodes  150  in  FIG. 5 . Thus radiation of radio waves to the back surface side of the antenna device is suppressed, so that the deterioration in the antenna characteristics such as gain can be suppressed. 
     The peripheral electrodes  150  are placed at positions that are symmetrical with respect to the polarization direction of the radio waves and/or the direction orthogonal to the polarization direction. Thus symmetry of the electric lines of force generated between the feed element  121  and the ground electrode GND 1  can be improved, so that the variation in the polarization direction can be suppressed. 
     With a free space wavelength of the radio waves radiated from the feed element  121  defined as λ o , the peripheral electrodes  150  are preferably provided on condition that a length (distance LG in  FIG. 2 ) from a surface center CP of the feed element  121  to an end portion of the ground electrode GND 1  along the polarization direction is smaller than λ o /2. 
     Second Example 
       FIG. 6  and  FIG. 7  are diagrams illustrating a second example of the antenna module according to Embodiment 1.  FIG. 6  is a plan view of an antenna module  100 A and  FIG. 7  is a perspective view of the antenna module  100 A. In  FIG. 6  and  FIG. 7  as well, the dielectric layers are omitted for facilitation of description. 
     The antenna module  100 A of  FIG. 6  is an example in which the sizes of the ground electrodes are further restricted compared with the antenna module  100  of  FIG. 2  and intervals between the end portions of the feed element  121  and the end portions of the ground electrode GND 1  in plan view are further narrowed on condition that the feed element  121  is placed as in the antenna module  100 . 
     Therefore, the antenna module  100 A has a configuration in which the feed element  121  is placed with a tilt of 45° around the Z axis with the surface center CP of the feed element  121  as the center in order that the distances from the surface center CP of the feed element  121  to the end portions of the ground electrode GND 1  in the polarization direction may be ensured so as to be as long as possible. That is, the feeding point SP 1  is placed at a position offset from the surface center CP of the feed element  121  by equal distances in the negative direction along the X axis and the positive direction along the Y axis. In the antenna module  100 A, therefore, the polarization direction is a direction (direction along a chain line CL 1  in  FIG. 6 ) that results from 45° tilting of the positive direction along the Y axis in the negative direction along the X axis. Such placement of the feed element  121  enables ensuring of the intervals between the end portions of the teed element  121  and the end portions of the ground electrode GND 1  in plan view and suppression of the decrease in the frequency band width. 
     In the antenna module  100 A, the feed element  121  is made to protrude from an extent of the ground electrode GND 1  (that is, an extent of the dielectric substrate  130 ) as a result of the tilting of the feed element  121  and thus four corner portions of the square feed element  121  are cut off so that the feed element  121  is substantially shaped like an octagon. 
     In the antenna module  100 A, peripheral electrodes  150 A that are substantially shaped like right triangles are placed along sides of the feed element  121  that extend along the polarization direction and sides thereof that are orthogonal to the polarization direction and in layers between the feed element  121  and the ground electrode GND 1 . The peripheral electrodes  150 A are placed so as to have hypotenuses facing in a first direction parallel to the polarization direction or in a second direction orthogonal to the polarization direction. Such placement of the peripheral electrodes  150 A at positions that are symmetrical with respect to the polarization direction of the radio waves and/or the direction orthogonal to the polarization direction increases the degree of the coupling between the feed element  121  and the ground electrode GND 1  and improves the symmetry of electric lines of force generated between the feed element  121  and the ground electrode GND 1 , so that the deterioration in the antenna characteristics can be suppressed. 
     Though the peripheral electrodes  150 A substantially shaped like the right triangle are illustrated in  FIG. 6  and  FIG. 7 , the peripheral electrodes may be in a shape of a triangle other than a right triangle or may be rectangular as in  FIG. 2 . It is preferable that a size of the peripheral electrodes  150 A should be greater than or equal to a length of a facing side of the feed element  121 . With the free space wavelength of radio waves radiated from the feed element  121  defined as λ o , the peripheral electrodes  150 A are preferably provided on condition that a length (distance LGA in  FIG. 6 ) from the surface center CP of the feed element  121  to an end portion of the ground electrode GND 1  along the polarization direction (direction along the chain line CL 1  in  FIG. 6 ) is smaller than λ o /2. 
     (Comparison of Antenna Characteristics) 
     With use of  FIG. 8 , antenna characteristics in accordance with presence or absence of the peripheral electrodes will be described. In  FIG. 8 , results of simulations with a configuration of the antenna module  100 A of the second example illustrated in  FIG. 6  and Comparative example  1  including no peripheral electrodes are illustrated. In  FIG. 8 , perspective views of. antenna modules, plan views thereof, current distribution diagrams concerning the ground electrode, and antenna gains are illustrated in descending order from top. In the current distribution diagrams, contour lines each denoting currents with an identical strength are illustrated as dashed lines. In the antenna gains, peak gains with angles from the radiation direction (Z-axis direction) are illustrated on an X-Y plane having an origin at the surface center of the feed element  121 . 
     In an antenna module  100 # 1  of Comparative example 1, in reference to  FIG. 8 , placement of the feed element  121  and the ground electrode GND 1  is similar to the antenna module  100 A, whereas the peripheral electrodes  150 A are not provided. Therefore, a portion of electric lines of force may go around onto the back, surface of the ground electrode GND 1  in the antenna module  100 # 1  of Comparative example 1. In the antenna module  100 # 1  of Comparative example 1, accordingly, the gains on the back surface side (between 120° and 180°, in particular) are increased and a peak gain in total is 4.8 [dBi]. In the antenna module  100 A including the peripheral electrodes  150 A, by contrast, the gains on the back surface side are decreased and the peak gain in total is improved to 5.3 [dBi]. That is, it is observed that, the electric lines of force which go around onto the back surface side are suppressed by the peripheral electrodes  150 A. 
     In both of the antenna module  100 A and the antenna module  100 # 1  of Comparative example 1, a dimension of the ground electrode GND 1  along the Y-axis direction is smaller than a dimension thereof along the X-axis direction and a shape of the ground electrode is asymmetrical with respect to the polarization direction passing through the surface center CP of the feed element  121 . Accordingly, a current distribution in the ground electrode of the antenna module  100 # 1  is shaped like a distorted ellipse having a minor axis along the Y-axis direction. In the antenna module  100 A of Embodiment 1, by contrast, the peripheral electrodes  150 A are placed at the positions that are symmetrical with respect to the polarization direction and the direction orthogonal to the polarization direction. Accordingly, it is observed that a current distribution in the ground electrode is closer to a true circle, compared with Comparative example 1, and that symmetry of currents is improved. 
     Thus the symmetrical placement of the peripheral electrodes electrically connected to the ground electrode enables suppression of the electric lines of force that are generated between the radiation element and the ground electrode and that go around onto the back surface and improvement in the symmetry of the electric lines of force even if the area of the ground electrode cannot be made sufficiently large, compared with the radiation element, and/or even if the ground electrode is asymmetrical with respect to the polarization direction passing through the surface center of the feed element. Thus, the deterioration in the antenna characteristics on condition that the size and/or shape of the ground electrode is restricted can be suppressed. 
     (Modification) 
       FIG. 9  is a diagram (perspective side view) illustrating a first modification of placement of the peripheral electrodes. In an antenna module  100 B of  FIG. 9 , placement of the peripheral electrodes with respect to the direction of the lamination is different compared with the antenna module  100  illustrated in  FIG. 3 . In the antenna module  100 B, more specifically, the closer to the ground electrode GND 1  a dielectric layer where a peripheral electrode  150 B is formed is, the more inside in the dielectric substrate  130  the peripheral electrode  150 B is placed. In other words, the peripheral electrodes  150 B are placed so as to get. close to the feed element  121  with approximation to the ground electrode GND 1 , in plan view from the normal direction with respect to the dielectric substrate  130 . 
     In such a configuration as well, the degree of the coupling between the feed element  121  and the ground electrode GND 1  can be increased, so that the antenna characteristics can be improved. Further, dielectrics surrounded by the feed element  121 , the ground electrode GND 1 , and a conductor wall of the peripheral electrodes  150 B are reduced in amount, compared with the configuration of the antenna module  100  illustrated in  FIG. 2 , so that electrostatic capacity between the feed element  121  and the ground electrode GND 1  is decreased. Thus increase in the frequency band width of radiated radio waves is enabled. 
       FIG. 10  is a diagram (plan view) illustrating a second modification of placement of the peripheral electrodes. In an antenna module  100 C of  FIG. 10 , compared with the antenna module  100  illustrated in  FIG. 2 , a peripheral electrode  150 C is placed so as to form a loop around the feed element  121 . By such a shape of the peripheral electrode as well, the electric lines of force that go around onto the back surface side are suppressed and the symmetry of the electric lines of force can be improved, because the peripheral electrode is placed at positions that are symmetrical with respect to the polarization direction and the direction orthogonal to the polarization direction. Accordingly, the antenna characteristics can be improved. 
     Embodiment 2 
     In Embodiment 1, the configuration in which the radiation element is singularly provided has been described. In Embodiment 2, a configuration in which peripheral electrodes are used in an array antenna provided with a plurality of radiation elements will be described. 
       FIG. 11  is a perspective view of an antenna module  100 D according to Embodiment 2. In reference to  FIG. 11 , an antenna device  120 A of the antenna module  100 D is an array antenna in which a plurality of feed elements  121  are placed on a dielectric substrate  130 A substantially shaped like a letter L. 
     The dielectric substrate  130 A includes a first substrate  1301  and a second substrate  1302  that differ in the normal direction each other and that are tabular and curving portions  135  to connect the first substrate  1301  and the second substrate  1302 . 
     The first substrate  1301  is a rectangular flat plate having the normal direction along the Z-axis direction and has four feed elements  121  arrayed thereon along the Y-axis direction. The RFIC  110  is placed on a back surface side of the first substrate  1301 . 
     The second substrate  1302  is a flat plate having the normal direction along the X-axis direction and has four feed elements  121  arrayed thereon along the Y-axis direction. In the second substrate  1302 , cutout portions  136  are formed in portions to be connected to the curving portions  135  and protruding portions  133  that protrude in the positive direction along the Z axis from the cutout, portions  136  are formed. At least a portion of each of the feed elements  121  arrayed on the second substrate  1302  is formed on the protruding portions  133 . 
     Such a configuration is used for an instrument that is shaped like a thin plate, such as a smartphone for instance, and that radiates radio waves in two directions from a main surface side and a side surface side. In the antenna module  100 D, the first substrate  1301  corresponds to the main surface side and the second substrate  1302  corresponds to the side surface side. On the second substrate  1302  placed on the side surface side in this configuration, the ground electrode GND 1  having a sufficient area may not be ensured due to a restriction on a dimension of the instrument along a direction of thickness that is, the Z-axis direction. Additionally, the cutout portions  136  for connection to the curving portions  135  make the shape of the ground electrode GND 1  asymmetrical with respect to the polarization direction passing through the surface center of each of the feed elements  121  and further make the shape of the ground electrode GND 1  different for each of the feed elements  121 . Then the antenna characteristics of the feed elements  121  of the array antenna become heterogeneous and thus the characteristics of the entire array antenna may be deteriorated. 
     In Embodiment 2, therefore, the antenna characteristics of the plurality of feed elements forming the array antenna are homogenized by application of such peripheral electrodes as described in Embodiment 1 to the array antenna, so that the antenna characteristics of the entire array antenna are improved. 
       FIG. 12  is a plan view of the second substrate  1302  on condition that the antenna module  100 D of  FIG. 11  is seen from the X-axis direction. In  FIG. 12 , the dielectric layers are omitted. The feed elements  121  placed on the second substrate  1302  have a configuration similar to the antenna module  100 A described in the second example of Embodiment 1. 
     More specifically, each of the feed elements  121  has the feeding point SP 1  (that is, the polarization direction) placed with a tilt, of 45° with respect to the Z axis and further has an octagonal shape resulting from deletion of four corners. The peripheral electrodes  150 A are placed at positions facing sides of the feed element  121  that extend along the polarization direction and sides thereof that extend along the direction orthogonal to the polarization direction and in layers between the feed element  121  and the ground electrode GND 1 . With such a configuration, the antenna characteristics can be homogenized by the peripheral electrodes even if a variation among the ground electrodes corresponding to the feed elements is brought about by restrictions on the sizes and/or shapes of the ground electrodes. 
       FIG. 13  is a diagram for illustration of differences in the antenna characteristics in accordance with the presence or absence of the peripheral electrodes in such an array antenna illustrated in  FIG. 11  and  FIG. 12 . In  FIG. 13 , results of simulations with a portion made of the second substrate  1302  in the antenna module  100 D of Embodiment 2 and an antenna module  100 # 2  of Comparative example 2 in which the peripheral electrodes  150 A are not provided are illustrated. In  FIG. 13 , return losses in two adjoining feed elements  121 - 1  and  121 - 2  are illustrated in middle sections and antenna gains with radiation of radio waves from four feed elements  121 - 1  to  121 - 4  are illustrated in bottom sections. 
     With regard to the return losses, solid lines LN 20  and LN 20 # denote the feed element  121 - 1  and dashed lines LN 21  and LN 21 # denote the feed element  121 - 2 . With regard to the antenna gains, peak gains of a main lobe ML 1  among the main lobe ML 1  and side lobes SL 1  and SL 2  of radio waves radiated in the X-axis direction are illustrated. Regarding the antenna gains, a solid line LN 25  denotes the antenna module  100 D of Embodiment 2 and a dashed line LN 26  denotes the antenna module  100 # 2  of Comparative example 2. 
     In the antenna module  1002  of Comparative example 2, in reference to  FIG. 13 , frequencies that decrease the return losses and a frequency band width that attains a specified return loss are slightly deviated between the two feed elements. That is, the two adjoining feed elements have different antenna characteristics. In the antenna module  100 D of Embodiment 2, by contrast, the two adjoining feed elements are substantially identical in the frequencies that decrease the return losses and the frequency band width and variations in the antenna characteristics are decreased. 
     It is thus observed that the antenna module  100 D (solid lines LN 25 ) of Embodiment 2 is larger in the antenna gains in a pass band as well, compared with the antenna module  100 # 2  (dashed line LN 26 ) of Comparative example 2, and improves the antenna characteristics. 
     As described above, the placement of the peripheral electrodes at the positions that are symmetrical with respect to the polarization direction and/or the direction orthogonal to the polarization direction for each of the radiation elements enables decrease in the variations in the antenna characteristics among the radiation elements and improvement in the antenna characteristics of the entire antenna module, even if the sizes and/or shapes of the ground electrodes with respect to the radiation elements are restricted in the antenna module in which the array antenna is formed. 
     (Modification 1) 
     In the antenna module  100 D of Embodiment 2 illustrated in  FIG. 11  and  FIG. 12 , the configuration in which the peripheral electrodes are individually provided for each of the adjoining feed elements has been described. In Modification 1, a configuration in which the antenna characteristics are further improved by commonality of the peripheral electrodes for the adjoining feed elements in an array antenna will be described. 
       FIG. 14  is a plan view of an antenna module  100 D 1  according to Modification 1. In the antenna module  100 D 1 , the peripheral electrodes  150 A between the feed element  121 - 1  and the feed element  121 - 2  and the peripheral electrodes  150 A between the feed element  121 - 3  and the feed element  121 - 4  are electrically connected and integrated by connection electrodes  151 . The peripheral electrodes  150 A and the connection electrodes  151  may be integrally formed instead of being made of individual elements connected. 
     Thus the commonality of the adjoining peripheral electrodes increases an area of the peripheral electrodes that receives the electric lines of force emitted from the feed elements and therefore enables suppression of the electric lines of force that go around onto the back surface of the ground electrode GND 1 . As a result, the deterioration in the antenna characteristics such as deterioration in the antenna gains, narrowing of the frequency band width, or the variation in the polarization direction can be further suppressed. 
     Though the commonality of some of the peripheral electrodes may deteriorate symmetry of a distribution of the electric lines of force in each feed element, sizes, shapes, and/or the like of the peripheral electrodes provided with no commonality may be appropriately adjusted in such a case. 
     (Modification 2) 
     In Modification 1, a configuration in which the peripheral electrodes for the adjoining feed elements are integrated by the separate connection electrodes has been described. 
     An antenna module  100 D 2  of Modification  2  illustrated in  FIG. 15  has a configuration in which the feed element  121  are placed so that the peripheral electrodes  150 A themselves are brought into contact with each other without use of the connection electrodes  151  of  FIG. 14  and in which coupling and the commonality of the adjoining peripheral electrodes  150 A are attained. In the antenna module  100 D 2  of  FIG. 15  as well, the area of the peripheral electrodes that receives the electric lines of force emitted from the feed elements is increased and therefore the deterioration in the antenna characteristics such as the deterioration in the antenna gains, the narrowing of the frequency band width, or the variation in the polarization direction can be further suppressed. 
     Embodiment 3 
     In Embodiment 1 and Embodiment 2, the configurations in which radio waves having the single polarization direction are radiated from one radiation element have been described. In Embodiment 3, an example of a configuration with application of the peripheral electrodes to a so-called dual-polarization antenna module in which radio waves having two different polarization directions can be radiated from one radiation element will be described. 
       FIG. 16  is a plan view of an antenna module  100 E according to Embodiment 3. The antenna module  100 E is an array antenna similar to the antenna module  100 D of Embodiment 2 but differs in that two feeding points SP 1  and SP 2  are provided for each of the feed elements  121 - 1  to  121 - 4 . When radio frequency signals are fed to the feeding point SP 1  of each of the feed elements  121 - 1  to  121 - 4 , radio waves having a polarization direction along a direction (direction in which a chain line CL 2  extends) that is tilted by 45° in the negative direction along the Y axis with respect to the Z axis are radiated. When radio frequency signals are fed to the feeding point SP 2 , radio waves having a polarization direction along a direction (direction in which a chain line CL 2  extends) that is tilted by 45° in the positive direction along the Y axis with respect to the Z axis are radiated. 
     The feed element  121 - 2  is placed so as to be turned by 180 ° with respect to the adjoining feed element  121 - 1 . The feed element  121 - 4  is placed so as to be turned by 180° with respect to the adjoining feed element  121 - 3 . Radio frequency signals having inverted phases are fed to identical feeding points of the feed elements that are placed so as to be turned by 180° with respect to each other. The phases of the radio waves radiated from each feed element and having each polarization direction can be made to coincide by such phase adjustment. Further, cross polarization discrimination (XPD) can be improved by placement of the feed elements, placed so as to adjoin, with turning by 180°. 
     In the antenna module  100 E as well, the peripheral electrodes  150 A are placed at the positions that are symmetrical, with respect to the polarization direction and the direction orthogonal to the polarization direction, for each of the feed elements  121 - 1  to  121 - 4 . Thus the variations in the antenna characteristics among the feed elements that are associated with the restrictions on the size and/or shape of the ground electrode GND 1  can be decreased and the antenna characteristics of the entire antenna module can be improved. 
       FIG. 17  is a diagram for illustration of isolation of two polarizations in accordance with the presence or absence of the peripheral electrodes in the dual-polarization antenna module. In  FIG. 17 , results of simulations of isolation between two feeding points in the antenna module  100 E of Embodiment 3 and an antenna module  100 # 3  of Comparative example 3 in which the peripheral electrodes  150 A are not provided are illustrated. As evident from  FIG. 17 , in a desired pass band, the isolation in the antenna module  100 E of Embodiment 3 is improved compared with the isolation in the antenna module  100 # 3  of Comparative example 3. Improvement in the isolation between the two polarizations results in improvement in the return losses and the gains and further leads to improvement in active impedance. 
     In the dual-polarization antenna module as well, as described above, the antenna characteristics can be improved, even in presence of restrictions on the ground electrode, by the placement of the peripheral electrodes at the positions that are symmetrical with respect to the polarization direction and/or the direction orthogonal to the polarization direction for each of the radiation elements. 
     Though the example in which the peripheral electrodes are applied to the dual-polarization array antenna has been described in above description, the peripheral electrodes may be applied to the dual-polarization antenna module having a single radiation element as described in Embodiment 1. 
     Embodiment 4 
     In the embodiments described above, the configurations in which the radio waves radiated from the radiation elements have a single frequency band have been described. In Embodiment 4, a configuration with application of such peripheral electrodes as described above to a so-called dual-band antenna module In which radio waves having two different frequency bands can be radiated from each radiation element will be described. 
       FIG. 18  is a plan view of an antenna module  100 F according to Embodiment 4. The antenna module  100 F is a dual-polarization array antenna as with Embodiment 3 but differs in that passive elements  122  are provided in addition to feed elements  121 A, as radiation elements. 
     The passive elements  122  are placed in layers between the feed elements  121 A and the ground electrode GND 1 . Feeder wiring from the RFIC  110  is connected through the passive elements  122  to the feeding points SP 1  and SP 2  of the feed elements  121 A. A dimension of the passive elements  122  in the polarization direction is greater than a dimension of the feed elements  121 A in the polarization direction. Accordingly, a resonant frequency of the passive elements  122  is lower than a resonant frequency of the feed elements  121 A. Feeding of radio frequency signals corresponding to the resonant frequency of the passive elements  122  causes the passive elements  122  to radiate radio waves that are lower in frequency band than from the feed elements  121 A. That is, the antenna module  100 F is the dual-band antenna module capable of radiating radio waves having two different frequency bands. 
     The feed elements  121 A and the passive elements  122  are placed so that the polarization direction is tilted by 45°0 with respect to the Z-axis direction, due to the restriction on the size of the ground electrode GND 1 . Further, the passive elements  122  have an octagonal shape resulting from deletion of four corner portions that protrude from the ground electrode GND 1 . 
     Herein, the feed elements  121 A on a higher-frequency side function as antennas by way of electromagnetic field coupling with the passive elements  122 . Meanwhile, the passive elements  122  function as antennas by way of electromagnetic field coupling with the ground electrode GND 1 . For the ground electrode GND 1 , as with Embodiment 2 and Embodiment 3, a sufficient area is not ensured with respect to the passive elements  122  and a shape that is asymmetrical with respect to the polarization direction passing through a surface center of a passive element  122  is further provided. 
     In the antenna module  100 F, therefore, the peripheral electrodes  150 A are placed at positions facing sides of the passive elements  122 . that extend along the polarization direction and sides thereof that, extend along the direction orthogonal to the polarization direction and in layers between the passive elements  122  and the ground electrode GND 1 . Thus the variations in the antenna characteristics among the passive elements  122  can be decreased and the antenna characteristics of the entire antenna module can be improved. 
     In the antenna module  100 F, though an example of a configuration in which the feed elements and the passive elements are provided as the radiation elements has been described, both the two radiation elements may be feed elements. 
     (Modification 3) 
       FIG. 19  is a plan view of an antenna module  100 F 1  according to Modification 3. In the antenna module  100 F 1  of Modification 3, as with Modification 1 described in  FIG. 14 , the coupling and commonality among the peripheral electrodes  150 A for adjoining radiation elements in the antenna module  100 F 1  are attained by the connection electrodes  151 . By such a configuration, electric lines of force emitted from the passive elements  122  and going around onto the back surface of the ground electrode GND 1  can be suppressed, so that the deterioration in the antenna characteristics can be further suppressed, compared with the antenna module  100 F of Embodiment 4. 
     (Modification 4) 
       FIG. 20  is a plan view of an antenna module  100 F 2  according to Modification 4. As with Modification 2 described in  FIG. 16 , the antenna module  100 F 2  of Modification 4 has a configuration in which the feed elements  121 A are placed so that adjoining peripheral electrodes  150 A are brought into contact with each other and so that the commonality between the peripheral electrodes  150 A is attained. In such a configuration as well, electric lines of force emitted from the passive elements  122  and going around onto the back surface of the ground electrode GND 1  can be suppressed, so that the deterioration in the antenna characteristics can be further suppressed, compared with the antenna module  100 F of Embodiment 4. 
     Embodiment 5 
     The area for the peripheral electrodes is preferably increased in order that the electric lines of force going around onto the back surface of the ground electrode may be suppressed with use of the peripheral electrodes. On the other hand, in case where other elements such as stubs or filters are formed in the dielectric substrate, a layout of those elements may be restricted by increase in the size of the peripheral electrodes. 
     In Embodiment 5, a configuration that may attain both ensuring of freedom of layout in the dielectric substrate and reduction in the electric lines of force going around onto the back surface of the substrate will be described. 
       FIG. 21  and  FIG. 22  are diagrams illustrating an antenna module  100 G according to Embodiment 5.  FIG. 21  is a plan view of the antenna module  100 G and  FIG. 22  is a perspective view of the antenna module  100 G. In  FIG. 21  and  FIG. 22  as well, the dielectric layers are omitted for facilitation of description. In the antenna module  100 G, peripheral electrodes  100 D are provided in place of the peripheral electrodes  150 A in the antenna module  100 A described in the second example of Embodiment 1. In  FIG. 21  and  FIG. 22 , description of elements that are common to the antenna module  100 A illustrated in  FIG. 6  and  FIG. 7  will not be iterated. 
     In reference to  FIG. 21  and  FIG. 22 , the peripheral electrodes  150 D in the antenna module  150 A are formed so as to have slightly smaller sizes than the peripheral electrodes  150 A illustrated in  FIG. 6  and  FIG. 7 . More specifically, the peripheral electrodes  150 A are each substantially shaped like the right triangle in plan view of the dielectric substrate, whereas an example of the peripheral electrodes  150 D of Embodiment 5 is substantially shaped like a trapezoid that results from removal of a portion (egion RG 1  of dashed lines in  FIG. 21 ) of a vertex portion having a right angle of the right triangle described above. Such alteration in the shape and size reduction of the peripheral electrodes enable expansion of spaces on the dielectric substrate where other elements may be placed. 
     With use of  FIG. 23  and  FIG. 24 , subsequently, antenna characteristics of the antenna module  100 G of Embodiment 5 will be described in comparison with the antenna characteristics of the antenna module  100 A.  FIG. 23  illustrates frequency characteristics in antenna gain and  FIG. 24  illustrates directivity. 
     In  FIG. 23 , the frequency characteristics are of the antenna gains on condition that the pass band has a center frequency of 28 GHz. In  FIG. 23  and  FIG. 24 , solid lines LN 40  and LN 50  denote a case with the antenna module  100 A and dashed lines LN 41  and LN 51  denote a case with the antenna module  100 G. 
     As illustrated in  FIG. 23 , the site of the peripheral electrodes of the antenna module  100 G of Embodiment 5 is reduced compared with the antenna module  100 A and the antenna module  100 G is slightly lower in the antenna gain than the case with the antenna module  100 A in general. In the intended pass band (25 GHz to 29.5 GHz), however, the antenna gains higher than or equal to 7 dBi are ensured throughout the band. 
     A graph of  FIG. 24  illustrates the directivity on condition that radio waves with the center frequency of 28 GHz are radiated and angles from the normal direction of the feed element  121  with respect to a section along the polarization direction are represented on a horizontal axis. In comparison of the peak gains at the angle of 0°, it is observed that the case with the antenna module  100 G attains the peak gain of 8 dBi, which is about 0.2 dBi lower compared with the case with the antenna module  100 A. 
     In a region with the angles greater than 100° and a region with the angles less than −100°, the gains of the antenna module  100 G are slightly greater than the gains of the antenna module  100 A. This indicates enhancement of going around onto the back surface of the dielectric substrate. That is, the case with the antenna module  100 G attains the directivity within a targeted specification range in general, though exhibiting a slight reduction, compared with the antenna module  100 A. 
     As described above, the antenna module  100 G of Embodiment 5 is slightly inferior in the antenna characteristics to the antenna module  100 A illustrated in  FIG. 6  but is capable of improving the antenna characteristics, compared with cases in which no peripheral electrodes are used. On the other hand, the freedom of layout in the dielectric substrate can be improved by the reduction in the size of the peripheral electrodes. 
     Which of the configuration of the antenna module  100 A and the configuration of the antenna module  100 G is to be adopted is appropriately selected in accordance with the required antenna characteristics and presence or absence of elements to be provided in the antenna module. 
     Embodiment 6 
     In the embodiments and modifications that have been described above, the configurations in which the radiation elements and the ground electrode are placed on the same dielectric substrate have been described. The radiation elements, however, may have a configuration in which the radiation elements are formed on a dielectric substrate differing from a dielectric substrate where the other elements are formed. 
       FIG. 25  is a perspective side view of an antenna module  100 H according to Embodiment 6. The antenna module  100 H has a configuration in which the feed element  121  in the antenna module  100  illustrated in  FIG. 3  for Embodiment 1 is formed in or on a dielectric substrate  130   b  and in which elements other than the feed element  121  are formed in or on a circuit board  300  independent from the dielectric substrate  130 B. In the circuit board  300 , the elements other than the feed element  121  in the antenna module  100  of  FIG. 3  are placed in or on a dielectric substrate  130 C and the RFIC  110  is mounted on a bottom surface side of the dielectric substrate  130 C. 
     A bottom surface of the dielectric substrate  130 B is placed so as to face a top surface of the dielectric substrate  130 C in the circuit board  300 . The feeder wiring  140  is connected to the feed element  121  through a connection terminal  161  placed between the dielectric substrate  130 B and the dielectric substrate  130 C. A solder bump, a connector, or a connecting cable is used as the connection terminal  161 . 
     Thus freedom of instrument placement in a communication device can be increased by the configuration in which the circuit board to be provided with the RFIC and the dielectric substrate to toe formed with the radiation element are formed as separate substrates. For instance, a configuration in which the circuit board is placed on a motherboard and in which the radiation element are placed in a casing may be adopted. 
     It is to be understood that the embodiments disclosed herein are exemplary in all respects and are not restrictive. A scope of the present disclosure is intended to be designated by the claims instead of the description of embodiments described above and to encompass all modifications within purport and a scope that are equivalent to the claims. 
     Reference Signs List 
       10  communication device 
       100 ,  100 A to  100 H,  100 D 1 ,  100 D 2 ,  100 F 1 ,  100 F 2  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 synthesizer/branching filter 
       118  mixer 
       119  amplifier circuit 
       120 ,  120 A antenna device 
       121 ,  121 A feed element 
       122  passive element 
       130 ,  130 A to  130 C dielectric substrate 
       131  top surface 
       132  bottom surface 
       133  protruding portion 
       135  curving portion 
       136  cutout portion 
       140  feeder wiring 
       150 ,  150 A to  150 D peripheral electrode 
       151  connection electrode 
       155  via 
       160  solder bump 
       161  connection terminal 
       170  wiring pattern 
       200  BBIC 
       300  circuit board 
       1301  first substrate 
       1302  second substrate 
     CP surface center 
     GND, GND 1 , GND 2  ground electrode 
     ML 1  main lobe 
     SL 1 , SL 2  side lobe 
     SP 1 , SP 2  feeding point