Patent Publication Number: US-2018053735-A1

Title: Wireless module

Description:
This application claims priority from Japanese Patent Application No. 2016-161614 filed on Aug. 22, 2016. The content of this application is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE DISCLOSURE 
     1. Field of the Disclosure 
     The present disclosure relates to a wireless module. 
     2. Description of the Related Art 
     A high-frequency wireless module obtained by modularizing an antenna element, a passive element, and a high-frequency integrated circuit element having a transmission/reception function in a high-frequency band, is publicly known (Japanese Unexamined Patent Application Publication No. 2007-129304). For example, electronic components such as a high-frequency integrated circuit element and a passive element are mounted on a board and sealed by a sealing member. A shield electrode is provided within the sealing member, and an antenna conductor such as a patch antenna is provided on the upper surface of the sealing member. The shield electrode for shielding the high-frequency integrated circuit element also serves as ground for the antenna. 
     The interval between the antenna conductor and the shield electrode that operates as ground influences the characteristics of the patch antenna. When the interval between the shield electrode and the antenna conductor is decreased, the operating band of the antenna becomes narrow. In order to widen the frequency band, the interval between the shield electrode and the antenna conductor has to be ensured to some extent. In the thickness direction of the board, since an antenna device including the antenna conductor and the shield electrode (ground) is stacked on a portion from the upper surface of the board to the shield electrode in which portion the high-frequency integrated circuit element is housed, it is difficult to reduce the thickness of the wireless module. 
     BRIEF SUMMARY OF THE DISCLOSURE 
     Accordingly, it is an object of the present disclosure to provide a wireless module having a structure suitable for thickness reduction. 
     A wireless module according to a first aspect of the present disclosure includes: a dielectric board; a ground plane provided to the dielectric board; a high-frequency integrated circuit element mounted on the dielectric board; a shield member provided on the dielectric board and electromagnetically shielding the high-frequency integrated circuit element; a first antenna element provided on the dielectric board and disposed at the same side as the shield member with respect to the ground plane; and a first feed line connecting the first antenna element to the high-frequency integrated circuit element, wherein in a plan view, a portion of the first antenna element is disposed outside the shield member, and a remaining portion of the first antenna element overlaps with the shield member, or an entire range of the first antenna element is disposed outside the shield member, and a spaced distance from the shield member to the first antenna element is not greater than about ½ of a resonant wavelength of the first antenna element. 
     In the thickness direction of the dielectric board, a portion occupied by an antenna device including the first antenna element and the ground plane and a portion occupied by the shield member partially overlap each other. Therefore, it is possible to reduce the thickness of the wireless module as compared to a configuration in which the antenna device and the shield member are stacked in the thickness direction. Here, the resonant wavelength means an effective wavelength that takes into consideration the dielectric constant of the space between the first antenna element and the shield member, in the frequency band in which the first antenna element resonates. 
     In a wireless module according to a second aspect of the present disclosure, in addition to the configuration of the wireless module according to the first aspect, the shield member is connected to the ground plane. 
     It is possible to shield the high-frequency integrated circuit element by the ground plane and the shield member. 
     In addition to the configuration of the wireless module according to the first or second aspect, a wireless module according to a third aspect of the present disclosure includes: a second antenna element provided on the dielectric board and disposed at a side opposite to the shield member with respect to the ground plane; and a second feed line connecting the second antenna element to the high-frequency integrated circuit element. 
     By operating either the first antenna element or the second antenna element, it is possible to switch the direction of strong directivity. 
     In a wireless module according to a fourth aspect of the present disclosure, in addition to the configuration of the wireless module according to the first to third aspects, the first antenna element is a patch antenna and a portion of the patch antenna overlaps with the shield member in a plan view. 
     At a portion where the patch antenna and the shield member overlap each other, the patch antenna and the shield member capacitively couple to each other. Therefore, the amount of radio waves radiated from the edge of the patch antenna that overlaps with the shield member is smaller than the amount of radio waves radiated from the edge of the patch antenna that does not overlap the shield member. As a result, it is possible to regard the patch antenna approximately as one wave source, and thus it is possible to achieve wider directivity. 
     In a wireless module according to a fifth aspect of the present disclosure, in addition to the configuration of the wireless module according to the first to third aspects, the first antenna element is a monopole antenna disposed at a position at which a spaced distance from the shield member thereto is not greater than about ½ of the resonant wavelength of the first antenna element in a plan view. 
     It is possible to reduce the thickness of the wireless module as compared to a configuration in which a monopole antenna is stacked on the shield member. 
     In a wireless module according to a sixth aspect of the present disclosure, in addition to the configuration of the wireless module according to the first to third aspects, an end of the monopole antenna is short-circuited to the shield member. 
     Since the first antenna element operates as a folded monopole antenna, it is possible to increase the impedance of the first antenna element and widen the band of the first antenna element. 
     Other features, elements, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of preferred embodiments of the present disclosure with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of a wireless module according to a first embodiment; 
         FIG. 2  is a schematic cross-sectional view of a wireless module according to a comparative example; 
         FIG. 3  is a schematic diagram of a wireless module according to a second embodiment; 
         FIG. 4  shows a plan view of a wireless module according to a third embodiment; 
         FIG. 5  is a schematic cross-sectional view of a wireless module according to a fourth embodiment; and 
         FIG. 6  is a schematic cross-sectional view of a wireless module according to a fifth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     First Embodiment 
     A wireless module according to a first embodiment will be described with reference to  FIG. 1 . 
       FIG. 1  is a schematic cross-sectional view of the wireless module according to the first embodiment. Ground planes  11  are provided to a dielectric board  10 . The ground planes  11  may be disposed only within the dielectric board  10 , or may be disposed both on the surface of the dielectric board  10  and within the dielectric board  10 .  FIG. 1  shows an example in which the ground planes  11  are disposed on the upper surface of the dielectric board  10  and within the dielectric board  10 . A partial region of the ground plane  11  disposed on the upper surface is used as a ground land. Furthermore, signal lands  12  are provided on the upper surface of the dielectric board  10 . 
     A high-frequency integrated circuit element  21  and a passive component  22  are mounted on the upper surface of the dielectric board  10 . Part of terminals of the high-frequency integrated circuit element  21  is connected to the ground plane  11 , and other part of the terminals is connected to the signal lands  12 , respectively. Each terminal of the passive component  22  is also connected to the ground plane  11  or the signal land  12 . 
     A shield member  25  provided on the dielectric board  10  covers the high-frequency integrated circuit element  21  and the passive component  22 . The shield member  25  is connected to the ground plane  11  and electromagnetically shields the high-frequency integrated circuit element  21  and the passive component  22 . For example, a shield case including an upper plate and side plates made of metal may be used as the shield member  25 . 
     The shield member  25  may include a metal film and a plurality of conductor bars. The plurality of conductor bars forming the shield member  25  are disposed so as to surround the high-frequency integrated circuit element  21  and the passive component  22  in a plan view and project upward from the surface of the dielectric board  10 . The metal film is disposed above the high-frequency integrated circuit element  21  and the passive component  22  and connected to the plurality of conductor bars in the vicinity of the outer periphery thereof. 
     A sealing member  30  made of resin is disposed on the dielectric board  10 . When the shield case is used as the shield member  25 , the sealing member  30  seals the shield member  25 . When the shield member  25  includes the metal film and the plurality of conductor bars, the high-frequency integrated circuit element  21  and the passive component  22  are sealed by the sealing member  30 , and the plurality of conductor bars are embedded within the sealing member  30 . The upper surface of the metal film forming the shield member  25  is also covered by the sealing member  30 . 
     A first antenna element  35  is provided on the upper surface of the sealing member  30 . The first antenna element  35  is disposed at the same side as the shield member  25  with respect to the ground plane  11 . For example, a patch antenna is used as the first antenna element  35 . The first antenna element  35  is connected to the high-frequency integrated circuit element  21  via a first feed line  36 . The first feed line  36  includes a conductor bar  37  extending within the sealing member  30  in a thickness direction, and a transmission line  38  provided in the dielectric board  10 . 
     In a plan view, a portion of the first antenna element  35  is disposed outside the shield member  25 , and the remaining portion of the first antenna element  35  overlaps with the shield member  25 . The first antenna element  35  has, for example, a substantially square or rectangular planar shape, one edge  35   a  is disposed inside the shield member  25 , and an edge  35   b  opposing to the edge  35   a  is disposed outside the shield member  25 . The one edge  35   a  is referred to as inner edge, and the edge  35   b  opposing to the edge  35   a  is referred to as outer edge. The first antenna element  35  is excited in a direction perpendicular to the inner edge  35   a  and the outer edge  35   b  inside and outside the shield member  25  (the right-left direction in  FIG. 1 ). 
     A second antenna element  15  is provided on the lower surface of the dielectric board  10 . The second antenna element  15  is disposed at a side opposite to the shield member  25  with respect to the ground plane  11 . For example, a patch antenna is used as the second antenna element  15 . The second antenna element  15  is connected to the high-frequency integrated circuit element  21  via a second feed line  16  provided in the dielectric board  10 . 
     The first antenna element  35  radiates radio waves upward with respect to the dielectric board  10  when being supplied with power from the high-frequency integrated circuit element  21 . The second antenna element  15  radiates radio waves downward with respect to the dielectric board  10  when being supplied with power from the high-frequency integrated circuit element  21 . 
     Next, advantageous effects of the wireless module according to the first embodiment shown in  FIG. 1  will be described in comparison with a comparative example shown in  FIG. 2 . 
       FIG. 2  is a schematic cross-sectional view of a wireless module according to the comparative example. In the wireless module according to the comparative example, a shield film  27  is used instead of the shield member  25  in  FIG. 1 . The shield film  27  is disposed over substantially the entire range of the upper surface of the sealing member  30 . The shield film  27  is connected to the ground plane  11  via a ground connection via  28 . 
     A dielectric layer  32  is disposed on the shield film  27 . The first antenna element  35  is disposed on the upper surface of the dielectric layer  32 . The conductor bar  37  for connecting the first antenna element  35  to the high-frequency integrated circuit element  21  penetrates the dielectric layer  32 , the shield film  27 , and the sealing member  30  in the thickness direction. A cavity is provided in the shield film  27  and at a position where the conductor bar  37  penetrates the shield film  27 , so that the shield film  27  and the conductor bar  37  are insulated from each other. The shield film  27  operates as ground for the first antenna element  35 . 
     In the first embodiment shown in  FIG. 1 , the interval from the ground plane  11  provided on the upper surface of the dielectric board  10  to the upper surface of the shield member  25  is represented by z 1 , and the interval from the upper surface of the shield member  25  to the first antenna element  35  is represented by z 2 . In the comparative example shown in  FIG. 2 , the interval from the ground plane  11  provided on the upper surface of the dielectric board  10  to the shield film  27  corresponds to the interval z 1  ( FIG. 1 ) in the first embodiment, and the interval from the shield film  27  to the first antenna element  35  corresponds to the interval z 2  ( FIG. 1 ) in the first embodiment. 
     In the first embodiment shown in  FIG. 1 , the interval between the outer edge  35   b  of the first antenna element  35  and the ground plane  11  provided on the upper surface of the dielectric board  10  is nearly equal to z 1 +z 2 , and the interval between the inner edge  35   a  and the upper surface of the shield member  25  is equal to z 2 . The extension of a fringing electric field spreading outward from the outer edge  35   b  of the first antenna element  35  depends on the interval z 1 +z 2 . On the other hand, in the comparative example shown in  FIG. 2 , each of the intervals between the four edges of the first antenna element  35  and the shield film  27  is equal to z 2 . The extension of a fringing electric field spreading outward from one edge of the first antenna element  35  according to the comparative example is influenced by the interval z 2  but is not influenced by the interval z 1  below the shield film  27 . 
     In the first embodiment, the fringing electric field spreading outward from the outer edge  35   b  of the first antenna element  35  more widely spreads due to the influence of the interval z 1 , and thus the effective size of the first antenna element  35  increases. As a result, in the first antenna element  35  according to the first embodiment, it is possible to achieve more favorable characteristics as compared to the first antenna element  35  according to the comparative example. 
     In the comparative example, in order to ensure the effective size of the first antenna element  35  equal to that in the first embodiment, the interval z 2  has to be made larger than the corresponding interval z 2  of the wireless module according to the first embodiment. When the interval z 2  is increased, the wireless module becomes thick. In other words, it is possible to reduce the thickness of the wireless module according to the first embodiment as compared to the wireless module according to the comparative example. 
     In addition, under a condition that the interval z 2  of the wireless module according to the first embodiment is nearly equal to the corresponding interval z 2  of the wireless module according to the comparative example and the effective size of the first antenna element  35  is the same, the first antenna element  35  according to the first embodiment is smaller than the first antenna element  35  according to the comparative example. The resonant frequency or the operating frequency of the first antenna element  35  depends on the effective size of the first antenna element  35 . Therefore, in the wireless module according to the first embodiment, it is possible to reduce the size of the first antenna element  35  by making the effective size of the first antenna element  35  the same while keeping the resonant frequency or the operating frequency constant, as compared to the comparative example. 
     Furthermore, in the wireless module according to the first embodiment shown in  FIG. 1 , the interval z 2  between the inner edge  35   a  of the first antenna element  35  and the shield member  25 , which serves as ground, is smaller than the interval z 1  between the outer edge  35   b  and the ground plane  11 . By the inner edge  35   a  of the first antenna element  35  and the shield member  25  capacitively coupling to each other, the amount of radio waves radiated from the inner edge  35   a  becomes smaller than that from the outer edge  35   b.  On the other hand, in the wireless module according to the comparative example shown in  FIG. 2 , each of the intervals from a pair of edges opposing to each other to the shield member  25 , which serves as ground, is equal to z 2 . Thus, the amounts of radio waves radiated from the pair of edges are nearly equal to each other. That is, two wave sources are present. 
     In the first embodiment, when the amount of radio waves radiated from the inner edge  35   a  of the first antenna element  35  is smaller than that from the outer edge  35   b,  it is possible to substantially regard the first antenna element  35  as a single wave source. Therefore, in the wireless module according to the first embodiment, it is possible to achieve wider directivity characteristics. 
     Furthermore, it is made possible to control the directivity and widen the band on the basis of the positional relationship or connection between the first antenna element  35  and the shield member  25 . In addition, the second antenna element  15  is disposed below the ground plane  11 , and the first antenna element  35  is disposed above the ground plane  11 . Therefore, it is possible to direct a main lobe of the directivity characteristics of the wireless module in either the downward direction or the upward direction with respect to the ground planes  11 . 
     When radio waves are radiated only upward with respect to the dielectric board  10 , the second antenna element  15  and the second feed line  16  may be omitted. 
     Second Embodiment 
     Next, a wireless module according to a second embodiment will be described with reference to  FIG. 3 . Hereinafter, the difference from the first embodiment shown in  FIG. 1  will be described, and the description of the configuration common with the first embodiment is omitted. 
       FIG. 3  is a schematic diagram of the wireless module according to the second embodiment. In the first embodiment, a portion of the first antenna element  35  overlaps with the shield member  25  in a plan view. However, in the second embodiment, the entire range of the first antenna element  35  is disposed outside the shield member  25  in a plan view. When the spaced distance from the shield member  25  to the first antenna element  35  in an in-plane direction is represented by L 1 , the spaced distance L 1  is not smaller than about 0. 
     The positional relationship between the outer edge  35   b  of the first antenna element  35  and the ground plane  11  is the same as that in the first embodiment. Unlike the structure of the first embodiment, the edge  35   a  opposing to the outer edge  35   b  is not disposed inside the shield member  25 , but the interval from the edge  35   a  to the shield member  25  is set so as to be smaller than the interval from the edge  35   b  to the ground plane  11 . Therefore, the substantially same advantageous effects as those of the first embodiment are also achieved in the second embodiment. 
     Next, a preferable range of the spaced distance L 1  will be described. When the spaced distance L 1  is excessively large, the effect caused by the first antenna element  35  and the shield member  25  capacitively coupling to each other is not achieved. In order to achieve the effect caused by the first antenna element  35  and the shield member  25  capacitively coupling to each other, the spaced distance L 1  is preferably not greater than about ½ of the resonant wavelength of the first antenna element  35 . Here, the resonant wavelength means an effective wavelength that takes into consideration the dielectric constant of the space between the first antenna element  35  and the shield member  25 , in the frequency band in which the first antenna element  35  resonates. 
     Third Embodiment 
     Next, a wireless module according to a third embodiment will be described with reference to  FIG. 4 . Hereinafter, the difference from the wireless module according to the first embodiment shown in  FIG. 1  will be described, and the description of the configuration common with the wireless module according to the first embodiment is omitted. 
       FIG. 4  shows a plan view of the wireless module according to the third embodiment. The first antenna element  35  is disposed on the upper surface of the sealing member  30 . The first antenna element  35  has a patch array antenna structure in which a plurality of radiation electrodes  39  are aligned in a row. Each radiation electrode  39  has a substantially square or rectangular planar shape. In a plan view, one edge  39   a  of each radiation electrode  39  is disposed inside the shield member  25 , and an edge  39   b  opposing to the edge  39   a  is disposed outside the shield member  25 . The other two edges intersect with the contour line of the shield member  25  in a plan view. 
     The second antenna element  15  is disposed on the lower surface of the dielectric board  10 . The second antenna element  15  also has a patch array antenna structure in which a plurality of radiation electrodes  19  are aligned in a row. It is possible to cause the first antenna element  35  and the second antenna element  15  to operate as a phased array antenna by controlling the phase of a high-frequency signal supplied to each radiation electrode  39  or  19 . 
     Fourth Embodiment 
     Next, a wireless module according to a fourth embodiment will be described with reference to  FIG. 5 . Hereinafter, the difference from the wireless module according to the first embodiment shown in  FIG. 1  will be described, and the description of the configuration common with the wireless module according to the first embodiment is omitted. 
       FIG. 5  is a schematic cross-sectional view of the wireless module according to the fourth embodiment. In the first embodiment, a patch antenna is used as the first antenna element  35 . However, in the present embodiment, a monopole antenna is used as the first antenna element  35 . The first antenna element  35  is composed of a conductor bar connected to the signal land  12  on the dielectric board  10 . The conductor bar extends in a direction parallel to the thickness direction of the dielectric board  10  and is embedded in the sealing member  30 . 
     The length of the monopole antenna as the first antenna element  35  is nearly equal to the thickness of the sealing member  30 . The first antenna element  35  is disposed near the shield member  25  in a plan view, and the side plate of the shield member  25  serves as a reflection plate for the first antenna element  35 . In order to cause the side plate of the shield member  25  to serve as a reflection plate, a spaced distance L 2  from the shield member  25  to the first antenna element  35  is preferably not greater than about ½ of the resonant wavelength of the first antenna element  35 . The resonant wavelength of the first antenna element  35  is equal to about  4  times of the length of the monopole antenna. 
     Next, advantageous effects of the wireless module according to the fourth embodiment will be described. The first antenna element  35  of the wireless module according to the fourth embodiment has strong directivity in the direction in which an end surface of the dielectric board  10  faces. In addition, similarly to the first embodiment, the second antenna element  15  has strong directivity in the direction in which the lower surface of the dielectric board  10  faces. As described above, in the fourth embodiment, it is possible to have strong directivity in one of or both of the direction in which the end surface of the dielectric board  10  faces and the direction in which the lower surface of the dielectric board  10  faces. 
     In addition, in the fourth embodiment, it is possible to reduce the thickness of the entire wireless module as compared to a structure in which a monopole antenna is stacked on the shield member  25 . 
     In  FIG. 5 , an example is shown in which the height of the shield member  25  is nearly equal to the length of the monopole antenna. However, it is not necessary to make the heights of the shield member  25  and the monopole antenna equal to each other. 
     Fifth Embodiment 
     Next, a wireless module according to a fifth embodiment will be described with reference to  FIG. 6 . Hereinafter, the difference from the wireless module according to the fourth embodiment shown in  FIG. 5  will be described, and the description of the configuration common with the wireless module according to the fourth embodiment is omitted. 
       FIG. 6  is a schematic cross-sectional view of the wireless module according to the fifth embodiment. In the fourth embodiment, a monopole antenna is used as the first antenna element  35 . However, in the fifth embodiment, a folded monopole antenna is used as the first antenna element  35 . Specifically, the first antenna element  35  includes: a conductor bar  40  extending in the thickness direction within the sealing member  30 ; and a short-circuit member  41  which short-circuits an end (upper end) of the conductor bar  40  to the shield member  25 . 
     The end of the conductor bar  40  and the upper surface of the shield member  25  are exposed on the upper surface of the sealing member  30 . The short-circuit member  41  is disposed so as to extend from the end of the conductor bar  40  exposed on the upper surface of the sealing member  30  to the upper surface of the shield member  25  exposed on the upper surface of the sealing member  30 . 
     In the fifth embodiment, by using the folded monopole antenna as the first antenna element  35 , it is possible to increase the impedance of the first antenna element  35  and widen the band of the first antenna element  35  as compared to the fourth embodiment. 
     Each embodiment is illustrative, and it is needless to say that the components shown in the different embodiments may be partially replaced or combined. The same advantageous effects achieved by the same configuration in multiple embodiments are not mentioned successively in each embodiment. Furthermore, the present disclosure is not limited to the above-described embodiments. For example, it is obvious to a person skilled in the art that various changes, modifications, combinations, etc. may be made. 
     While preferred embodiments of the disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the disclosure. The scope of the disclosure, therefore, is to be determined solely by the following claims.