Patent Publication Number: US-2018034154-A1

Title: Antenna and communication device

Description:
TECHNICAL FIELD 
     The present invention relates to an antenna and a communication device including the antenna. 
     BACKGROUND ART 
     Pattern antennas are widely used in which a planar antenna element is formed on a substrate, and power is supplied to the antenna element through a coaxial cable so that the antenna element functions as an antenna. 
     Patent Literature (hereinafter, referred to as “PTL”) 1, for example, discloses an antenna composed of three components: a substrate having antenna elements formed on its surface; a coaxial cable; and an RF connector which is attached to an end of the coaxial cable for coupling with a receiving circuit. 
     In this antenna, inner and outer conductors of the coaxial cable are soldered to the antenna elements, respectively. A signal received at the antenna element is then transmitted to the receiving circuit via the coaxial cable. 
     CITATION LIST 
     Patent Literature 
     PTL 1 
     
         
         Japanese Patent Application Laid-Open No. H10-313207 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     With the related art disclosed in PTL 1, however, signals are transmitted via the coaxial cable and this leads to difficulty in size reduction of a communication device, lower gain, and increased manufacturing costs. Further, since the antenna and the receiving circuit are connected to each other by a bendable coaxial cable, another member is required for fixing the installation direction of the antenna. 
     The present invention has been made in view of the aforementioned problem and aims to provide: an antenna which enables easy size reduction, higher gain, lower manufacturing costs, and easy fixing of the installation direction; and a communication device. 
     Solution to Problem 
     An antenna according to the present invention is an antenna to be attached to a radio module including a first substrate, a radio circuit to be fixed to the first substrate, and a first coaxial connector to be fixed to the first substrate and to be connected to the radio circuit, the antenna including: a second substrate; a conductor formed on one surface side of the second substrate; and a second coaxial connector to be fixed to the second substrate in a state where the second coaxial connector is connected to the conductor, and to be detachably coupled to the first coaxial connector, in which the second substrate is fixed parallel to the first substrate in a state where the second coaxial connector is coupled to the first coaxial connector. 
     A communication device according to the present invention includes the antenna and the radio module. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to provide: an antenna which enables easy size reduction, higher gain, lower manufacturing costs, and easy fixing of the installation direction; and a communication device. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating an exemplary configuration of a communication device according to an embodiment of the present invention; 
         FIG. 2  is a diagram illustrating an exemplary configuration of a radio module forming the communication device; 
         FIG. 3  is a diagram illustrating an exemplary configuration of an antenna forming the communication device; 
         FIG. 4  is a plan view illustrating a coaxial connector of the antenna; 
         FIG. 5  is a bottom view illustrating the coaxial connector of the antenna; 
         FIG. 6  is a side view illustrating the coaxial connector of the antenna; and 
         FIG. 7  is a diagram illustrating radiation patterns of the communication device. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the following, an embodiment of the present invention is described in detail with reference to the accompanying drawings. 
       FIG. 1  is a diagram illustrating an exemplary configuration of communication device  1  according to the embodiment of the present invention.  FIG. 2  is a diagram illustrating an exemplary configuration of radio module  2  forming communication device  1 .  FIG. 3  is a diagram illustrating an exemplary configuration of antenna  3  forming communication device  1 . 
     As shown in  FIG. 1 , communication device  1  includes radio module  2  and antenna  3 . Radio module  2  performs radio communication with other communication devices by transmitting and receiving radio waves via antenna  3 . 
     As shown in  FIG. 2 , radio module  2  includes: substrate  4 ; electronic component  7  on which a radio circuit, a microcomputer, a memory, a peripheral circuit, and the like are mounted; coaxial connector  8  for coupling radio module  2  and antenna  3 ; and a battery holder (not shown) for accommodating a battery such as a coin type battery that supplies power to electronic component  7 . 
     Coaxial connector  8  is a male connector which includes inner conductor  8   a  having a pin-shaped portion adopted to contact coaxial connector  9  to be described later and outer conductor  8   b  having a cylindrical portion adopted to contact coaxial connector  9 . 
     As shown in  FIG. 3 , antenna  3  includes substrate  5 , conductor  6  formed on the surface of substrate  5 , coaxial connector  9 , and double-sided adhesive tape  10 . Conductor  6  forms a loop-like pattern, and the two ends of conductor  6  face each other. By supplying power to the two ends, antenna  3  functions as a loop antenna. 
     Also, female coaxial connector  9  adopted to couple to coaxial connector  8  of radio module  2  is provided in an area where the two ends of conductor  6  are disposed, and coaxial connector  9  is fixed to substrate  5  in a state of being connected to conductor  6 . 
     In  FIG. 3 , coaxial connector  9  is indicated by a dotted line, where the detailed shape of coaxial connector  9  is not shown. The shape and the like of coaxial connector  9  will be described later in detail with reference to  FIGS. 4 to 6 . 
     Coaxial connector  8  and coaxial connector  9  are detachably coupled. When coaxial connector  8  and coaxial connector  9  are coupled, substrate  4  of radio module  2  and substrate  5  of antenna  3  are fixed in parallel. 
     In the manner described above, detachably coupling coaxial connector  8  and coaxial connector  9  allows an antenna having a conductor pattern different from that of antenna  3  to be used depending on the purpose of use or the use environment, and enables adjusting the directivity and the gain. For example, an antenna having a conductor pattern such as that of a dipole antenna can be used. 
     Further, since antenna  3  can be fixed to radio module  2 , the radiation direction of radio waves can be set to a certain direction, and another member for fixing the installation direction of antenna  3  is unnecessary, which allows for size reduction of communication device  1 . 
     Moreover, double-sided adhesive tape  10 , a separate fixing member from coaxial connectors  8  and  9 , is used for coupling substrates  4  and  5 . Thereby, substrates  4  and  5  are more firmly fixed to each other. Note that it is not always necessary to use double-sided adhesive tape  10 , and substrates  4  and  5  may be fixed to each other only by coupling coaxial connectors  8  and  9 . 
     Alternatively, instead of double-sided adhesive tape  10 , substrates  4  and  5  may be fixed to each other by a screw, or substrates  4  and  5  may be fixed to each other by accommodating radio module  2  and antenna  3  in a case. Further, substrates  4  and  5  may be fixed by a fixing member other than double-sided adhesive tape  10 , a screw, or a case. 
     Next, the shape and the like of coaxial connector  9  of antenna  3  will be described in detail.  FIG. 4  is a plan view of coaxial connector  9 ,  FIG. 5  is a bottom view of coaxial connector  9 , and  FIG. 6  is a side view of coaxial connector  9 . Note that a part of  FIG. 6  is a cross-sectional view to illustrate the inside of coaxial connector  9 . 
     As shown in  FIG. 4 , coaxial connector  9  includes inner conductor  9   a  having a hole through which a pin-shaped portion of inner conductor  8   a  of coaxial connector  8  is to be inserted; outer conductor  9   b  adopted to contact the cylindrical portion of outer conductor  8   b  of coaxial connector  8 ; and groove  9   c  for allowing the cylindrical portion of outer conductor  8   b  to enter and causing outer conductor  8   b  and outer conductor  9   b  to contact with each other. 
     As shown in  FIGS. 5 and 6 , inner conductor  9   a  extends to the bottom surface of coaxial connector  9  and is connected to the end portion of conductor  6  at the center of coaxial connector  9  shown in  FIG. 3 . On the other hand, outer conductor  9   b  also extends to the bottom surface of coaxial connector  9  and is connected to the end portion of conductor  6  at the corner of coaxial connector  9  shown in  FIG. 3 . 
     Connecting coaxial connector  9  and conductor  6  in the manner described above and supplying power from radio module  2  to the end portion of conductor  6  allows antenna  3  to function as a loop-antenna. 
       FIG. 7  is a diagram illustrating a radiation pattern when communication device  1  shown in  FIG. 1  is disposed such that the normal direction of substrates  4  and  5  is in the horizontal direction. The solid line in  FIG. 7  indicates the horizontal radiation pattern of communication device  1 , and the dotted line in  FIG. 7  indicates the vertical radiation pattern of communication device  1 . 
     As shown in  FIG. 7 , the directivity of communication device  1  is similar to the directivity of widely used dipole antennas. As described above, since the general characteristics can be obtained in communication device  1 , handling of the communication device  1  becomes easy. 
     Further, in communication device  1 , the radio module and the antenna are not connected using a coaxial cable but are connected by coaxial connectors  8  and  9  unlike the related art, so that communication device  1  can be further reduced in size and the manufacturing costs of communication device  1  can be reduced as well. 
     Furthermore, in communication device  1 , since no coaxial cable is used for coupling radio module  2  and antenna  3 , cable loss by the coaxial cable is eliminated, and communication device  1  with higher gain can be obtained. 
     INDUSTRIAL APPLICABILITY 
     The present invention is suitable for use in an antenna and a communication device. 
     REFERENCE SIGNS LIST 
     
         
           1  Communication Device 
           2  Radio Module 
           3  Antenna 
           4 ,  5  Substrate 
           6  Conductor 
           7  Electronic Component 
           8 ,  9  Coaxial Connector 
           8   a ,  9   a  Inner Conductor 
           8   b ,  9   b  Outer Conductor 
           9   c  Groove 
           10  Double-Sided Adhesive Tape