Patent Publication Number: US-2018034132-A1

Title: Electronic device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Japanese Patent Application No. 2016-147553 filed on Jul. 27, 2016, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to an electronic device provided with an antenna corresponding to a plurality of communication bands. 
     BACKGROUND 
     Electronic devices having communication functions, such as mobile phones or smartphones, have been known. 
     SUMMARY 
     An electronic device according to one embodiment of the present disclosure includes an antenna corresponding to a plurality of communication bands, a conductive member, a GND terminal, a first circuit, a second circuit having an impedance lower than that of the first circuit and a switching circuit. The first circuit and the second circuit can each connect the conductive member and the GND terminal. The switching circuit switches a circuit connecting the conductive member and the GND terminal between the first circuit and the second circuit depending on the communication band for use. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a perspective view of an electronic device according to one embodiment; 
         FIG. 2  is a diagram of an internal structure of the electronic device&#39;s lower part viewed from back; 
         FIG. 3  is a schematic diagram of a circuit group connecting a conductive member and a substrate; 
         FIG. 4  is a circuit diagram schematically illustrating a circuit group connecting the conductive member and the substrate; 
         FIG. 5  is a diagram illustrating a position of a connection of the conductive member; 
         FIG. 6  is a diagram illustrating an antenna gain of the electronic device in communication using a single band of 700 MHz; 
         FIG. 7  is a diagram illustrating an antenna gain of the electronic device in communication using a single band of 800 MHz; 
         FIG. 8  is a diagram illustrating an antenna gain of the electronic device in communication using a single band of 2 GHz; 
         FIG. 9  is a diagram illustrating an antenna gain of the electronic device in a simultaneous multiband communication; and 
         FIG. 10  is a functional block diagram of a component that controls operation of the electronic device; 
         FIG. 11  is a diagram illustrating the setting information stored in a memory of the electronic device; 
         FIG. 12  is a flow chart illustrating an operation of the electronic device. 
     
    
    
     DETAILED DESCRIPTION 
     For example, an antenna built in a mobile communication terminal and having multi-band characteristics has been known. Miniaturization of electronic devices has occasionally been desired. However, miniaturization of an electronic device may decrease the distance between an antenna and a conductive member disposed around the antenna and may block electromagnetic waves, and thus antenna characteristics may be reduced. Thus, reduction in deterioration of antenna characteristics has been desired for the electronic devices known in the art. 
     It is an object of the present disclosure to provide an electronic device that reduces deterioration of antenna characteristics of an antenna corresponding to a plurality of communication bands. 
     According to an electronic device of one embodiment of the present disclosure, deterioration of the antenna characteristics of an antenna corresponding to a plurality of communication bands is reduced. 
     One embodiment will be described below with reference to drawings. 
     An electronic device  10  according to one embodiment will be described with reference to  FIG. 1 . In one embodiment, the electronic device  10  is a smartphone, for example. In the other embodiment, the electronic device  10  may include any device having a communication function, such as a personal computer (PC), a mobile phone, a tablet terminal and a game machine. For example, the electronic device  10  illustrated in  FIG. 1  has three physical buttons  11  in the lower part on its front side. 
     An internal structure of the electronic device  10  around an antenna  12 , which is built in the electronic device  10 , will be described with reference to  FIG. 2 .  FIG. 2  illustrates the antenna  12  built in the lower part of the electronic device  10 , two conductive members  13  and a substrate  14 . Hereinafter the two conductive members  13  are referred to also as a first conductive member  13   a  and a second conductive member  13   b  if needed. 
     The antenna  12  is a multiband antenna corresponding to a plurality of communication bands. In one embodiment, the antenna  12  corresponds to three types of communication bands including 700 MHz band, 800 MHz band and 2 GHz band. The antenna  12  has a first antenna element  15  corresponding to 700 MHz band and 800 MHz band and a second antenna element  16  corresponding to 2 GHz band. 
     In one embodiment, the electronic device  10  provided with the antenna  12  can communicate with four types of communication systems including communication using a single band of 700 MHz, communication using a single band of 800 MHz, communication using a single band of 2 GHz and simultaneous multiband communication in which above three communication bands are simultaneously used. In the other embodiment, the electronic device  10  may communicate with a communication system in which any number of above communication bands may be simultaneously used. The first antenna element  15  and the second antenna element  16  extend from a feeding point  17  in directions different from each other. The antenna  12  may have not only the above described configuration but also may have any configurations capable of corresponding to a plurality of communication bands. 
     In one embodiment, the conductive member  13  is a key flexible printed circuit (FPC) that transmits input signals for the physical button  11  to the substrate  14 . A terminal  18  with a plurality of wiring patterns passing thereover is extendedly provided to the conductive member  13 . The conductive member  13  is connected to the substrate  14  through the terminal  18 . The wiring pattern includes a ground (GND) wiring pattern for grounding and an output wiring pattern for outputting input signals for the physical button  11 . The GND wiring pattern is connected to a first GND terminal provided to the substrate  14 . The output wiring pattern is connected to the input terminal of the substrate  14  that receives input signals for the physical button  11 . Hereinafter a path by which the conductive member  13  and the first GND terminal of the substrate  14  are connected through the terminal  18  is referred to also as a first connection path. In the other embodiment, the conductive member  13  is not limited to a key FPC, and may be any conductive and grounded member. 
     The conductive member  13  is disposed near the antenna  12 . Near the antenna  12  means that the distance between the antenna  12  and the conductive member  13  is small enough to cause deterioration of the antenna characteristics, such as antenna gain, in a practical use due to the effects of electromagnetic waves blocked by the grounded conductive member  13  and capacitive coupling between the antenna  12  and the conductive member  13 . For example, the conductive member  13  disposed near the antenna  12  may deteriorate the antenna characteristics to less than the predetermined performance. In the example illustrated in  FIG. 2 , the antenna  12  and the conductive member  13  are disposed so that they are overlapped with each other in the thickness direction of the electronic device  10 . The area of the region where the antenna  12  and the first conductive member  13   a  are overlapped with each other is larger than the area of the region where the antenna  12  and the second conductive member  13   b  are overlapped with each other. Thus, the first conductive member  13   a  may have a greater effect on the antenna characteristics than the second conductive member  13   b  may have. 
     In one embodiment, as illustrated in  FIG. 3 , for example, the conductive member  13  and the substrate  14  are connected by the above described first connection path and the second connection path  19  which is different from the first connection path, respectively. This configuration reduces deterioration of the antenna characteristics caused by the conductive member  13 . The second connection path  19  and reduction in deterioration of the antenna characteristics may be described in detail later. 
     Various elements required for operating the electronic device  10 , such as a memory and a processor described later, are disposed on the substrate  14 . For example, the above described first GND terminal and input terminal and a second GND terminal  21  described later are disposed on the substrate  14 . 
     The second connection path  19  connecting the conductive member  13  and the substrate  14  is described in detail with reference to  FIG. 3 . In  FIG. 3 , the first connection path is not illustrated for visibility. 
     A second connection path  19   a  of the first conductive member  13   a  is a path that connects a connection  20   a  provided on the first conductive member  13   a  and a second GND terminal  21   a  provided on the substrate  14 , as illustrated in  FIG. 3 , for example. The connection  20   a  is an exposed portion of GND wiring patterns of the first conductive member  13   a , for example, and is only needed to be electrically connected with the GND wiring patterns. The position of the connection  20   a  on the first conductive member  13   a  will be described later. The second connection path  19   a  includes a first circuit  22 , a second circuit  23  and a switching circuit  24 . 
     The first circuit  22  is a resonance circuit including an inductor and a condenser connected in series. The first circuit  22  has a high impedance in a predetermined communication band. A high impedance means a large impedance value. For example, the impedance of the first circuit  22  in the first communication band of a plurality of communication bands corresponding to the antenna  12  is larger than that of the first circuit  22  in the second communication band thereof. In one embodiment, the first communication band is 2 GHz band and the second communication band is 800 MHz band. The first circuit  22  can connect the connection  20   a  of the first conductive member  13   a  and the second GND terminal  21   a  of the substrate  14  depending on the operation of the switching circuit  24  described later. 
     The second circuit  23  is a circuit including a conductor or a resistor. The second circuit  23  has the frequency characteristics of impedance which is different from that of the first circuit  22 . In one embodiment, the second circuit  23  has an impedance lower than that of the first circuit  22 . The low impedance means that an impedance value is small. Specifically, the impedance of the second circuit  23  in 800 MHz band is lower than the impedance of the first circuit  22  in 800 MHz band. The second circuit  23  can connect the connection  20   a  of the first conductive member  13   a  and the second GND terminal  21   a  of the substrate  14  depending on the operation of the switching circuit  24  described later. 
     The switching circuit  24  includes two switching terminals and one common terminal. The switching circuit  24  includes a switch that can switch between either one of the two switching terminals to be electrically connected to the common terminal. In one embodiment, two switching terminals of the switching circuit  24  are connected to the first circuit  22  terminal and the second circuit  23  terminal, respectively. The second GND terminal  21   a  of the substrate  14  is connected to the common terminal of the switching circuit  24 . The other terminals of the first circuit  22  and the second circuit  23  are respectively connected to the connection  20   a  of the first conductive member  13   a . In the other embodiment, the connection  20   a  may be connected to the common terminal of the switching circuit  24  and the second GND terminal  21   a  may be connected to each of the other terminals of the first circuit  22  and the second circuit. 
     The switching circuit  24  switches the circuit connecting the connection  20   a  of the first conductive member  13   a  and the second GND terminal  21   a  of the substrate  14  between the first circuit  22  and the second circuit  23  depending on the communication band for use. A specific operation of the switching circuit  24  depending on the communication band for use will be described later. 
     The second connection path  19   b  of the second conductive member  13   b  is a path that connects the connection  20   b  provided on the second conductive member  13   b  and the second GND terminal  21   b  provided on the substrate  14  through a third circuit  25 . The connection  20   b  is an exposed portion of the GND wiring pattern of the second conductive member  13   b , for example, and is only needed to be electrically connected with the GND wiring pattern. The position of the connection  20   b  on the second conductive member  13   b  will be described later. 
     The third circuit  25  is a resonance circuit having an inductor and a condenser connected in series. The third circuit  25  has a high impedance in a predetermined communication band. For example, the impedance of the third circuit  25  in 2 GHz band is higher than that of the third circuit  25  in 800 MHz band among the communication bands corresponding to the antenna  12 . The configuration of the third circuit  25  may be the same as that of the above described first circuit  22 . One of the terminals of the third circuit  25  is connected to the connection  20   b  of the second conductive member  13   b  and the other terminal is connected to the second GND terminal  21   b  of the substrate  14 . 
     A circuit configuration in which the first conductive member  13   a  and the substrate  14  are connected through the first connection path  26   a  and the second connection path  19   a  will be described with reference to  FIG. 4 . The first connection path  26   a  connects the GND wiring pattern  27   a  of the first conductive member  13   a  and the first GND terminal  28   a  of the substrate  14 . The resistance R illustrated on the first connection path  26   a  in  FIG. 4  is a resistance, such as a conductor and a resistor. 
     Hereinafter the state where the connection  20   a  and the second GND terminal  21   a  are connected through the first circuit  22  of the second connection path  19   a  is referred to as a first connection state and the state where the connection  20   a  and the second GND terminal  21   a  are connected through the second circuit  23  is referred to as a second connection state. 
     When the second connection path  19   a  is in the first connection state, the connection  20   a  and the second GND terminal  21   a  are connected through an inductor and a condenser disposed in series. The first connection path  26   a  and the second connection path  19   a  serve as a parallel resonance circuit that connects the first conductive member  13   a  and the GND terminal of the substrate  14 . 
     According to the experimental data described later, when the second connection path  19   a  is in the first connection state, the antenna gain in communication using a single band of 2 GHz and simultaneous multiband communication is improved compared to that in the second connection state. As described above, the first circuit  22  has a relatively high impedance in 2 GHz band. When the impedance of the second connection path  19   a  is sufficiently high, the first conductive member  13   a  is electrically separated when viewed from the antenna  12  in communication using 2 GHz band. Thus, it is assumed that deterioration of antenna characteristics due to the effects of the first conductive member  13   a  is reduced. 
     Meanwhile, when the second connection path  19   a  is in the second connection state, the connection  20   a  and the second GND terminal  21   a  are connected through the resistance R. The resistance R illustrated on the second connection path  19   a  in  FIG. 4  is a resistance, such as a conductor or a resistor. 
     According to the experimental data described later, when the second connection path  19   a  is in the second connection state, the antenna gain in communication using a single band of 700 MHz and communication using a single band of 800 MHz is improved compared to that in the first connection state. In communication using a single band of 700 MHz and communication using a single band of 800 MHz, when the second connection path  19   a  is in the first connection state where its impedance is relatively high, it is assumed that the first conductive member  13   a  that is electrically separated when viewed from the antenna  12  and the first antenna element  15  of the antenna  12  are capacitively coupled. When the first conductive member  13   a  is capacitively coupled with the first antenna element  15 , the electrical length of the first antenna element  15  varies, and thus the antenna characteristics may be deteriorated in communication using a single band of 700 MHz and communication using a single band of 800 MHz. Meanwhile, as described above, the second circuit  23  has an impedance lower than that of the first circuit  22  in 800 MHz band. Thus when the second connection path  19   a  is in the second connection state, it is assumed that deterioration of antenna characteristics may be reduced in communication using a single band of 700 MHz and communication using a single band of 800 MHz. 
     The position of the connection  20  on the conductive member  13  will be described with reference to  FIG. 5 . In  FIG. 5 , the terminal  18  is not illustrated for visibility. The length from the connection  20  to the end of the conductive member  13  may be other than an integer multiple of quarter wavelength of the frequency in a plurality of communication bands to which the antenna  12  corresponds. In one embodiment, the length may be a physical length or an electrical length. In this configuration, block of electromagnetic waves by the conductive member  13  is reduced, and thus deterioration of antenna characteristics may further be reduced. In the other embodiment, a plurality of connections  20  may be provided to the conductive member  13 . In this case, the length between any two of the connections  20  may be other than an integer multiple of a quarter wavelength of the frequency in a plurality of communication bands to which the antenna  12  corresponds. 
     The experimental data of the antenna characteristics in the first conductive member  13   a  depending on the connection state of the second connection path  19   a  will be described with respect to  FIGS. 6 to 9 . In the graphs illustrated in  FIGS. 6 to 9 , the horizontal axis represents the frequency of electromagnetic waves transmitted by the electronic device  10  and the vertical axis represents the antenna gain. 
       FIG. 6  illustrates the antenna gain in communication using a single band of 700 MHz. As obvious from  FIG. 6 , the antenna gain of the second connection path  19   a  of the first conductive member  13   a  is larger when it is in the second connection state than that in the first connection state. Thus, in communication using a single band of 700 MHz, the second connection path  19   a  of the first conductive member  13   a  may preferably be in the second connection state, that is, in the state where the first conductive member  13   a  and the second GND terminal  21   a  of the substrate  14  are connected through the second circuit  23 . 
       FIG. 7  illustrates the antenna gain in communication using a single band of 800 MHz. As obvious from  FIG. 7 , the antenna gain of the second connection path  19   a  of the first conductive member  13   a  is larger when it is in the second connection state than that in the first connection state. Thus, in communication using a single band of 800 MHz, as with communication using a single band of 700 MHz, the second connection path  19   a  of the first conductive member  13   a  may preferably be in the second connection state. 
       FIG. 8  illustrates the antenna gain in communication using a single band of 2 GHz. As obvious from  FIG. 8 , the antenna gain is larger when the second connection path  19   a  of the first conductive member  13   a  is in the first connection state than that in the second connection state. Thus, in communication using a single band of 2 GHz, the second connection path  19   a  of the first conductive member  13   a  may preferably be in the first connection state, that is, in the state where the first conductive member  13   a  and the second GND terminal  21   a  of the substrate  14  are connected through the first circuit  22 . 
       FIG. 9  illustrates the antenna gain in simultaneous multiband communication. As obvious from  FIG. 9 , the antenna gain in 700 MHz band and 2 GHz band is larger when the second connection path  19   a  of the first conductive member  13   a  is in the first connection state than that in the second connection state. Meanwhile, the antenna gain in 800 MHz band is smaller when the second connection path  19   a  of the first conductive member  13   a  is in the first connection state than that in the second connection state. However, reduction in the antenna gain in 800 MHz band is within an allowable range in a practical use. Thus, in simultaneous multiband communication, as with the communication using a single band of 2 GHz, the second connection path  19   a  of the first conductive member  13   a  may preferably be in the first connection state. 
     In one embodiment, in communication using a single band of 700 MHz and communication using a single band of 800 MHz, the second connection path  19   a  of the first conductive member  13   a  is dynamically switched to the second connection state. Meanwhile, in communication using a single band of 2 GHz and simultaneous multiband communication, the second connection path  19   a  of the first conductive member  13   a  is dynamically switched to the first connection state. 
     The configuration of the electronic device  10  that dynamically switches the connection state of the second connection path  19   a  of the first conductive member  13   a  will be described with reference to  FIG. 10 . The electronic device  10  includes a memory  29  and a processor  30 . 
     The memory  29  includes a primary storage device and a secondary storage device, for example. The memory  29  may include a semiconductor memory, a magnetic memory, or an optical memory, for example. In one embodiment, the memory  29  stores various information and programs required for operating the electronic device  10 . 
     For example, the memory  29  stores multiple pieces of setting information used for controlling the switching circuit  24 . In one embodiment, each piece of setting information indicates a circuit that connects the first conductive member  13   a  and the second GND terminal  21   a  of the substrate  14 . In the other embodiment, each piece of setting information may indicate the connection state of the second connection path  19   a  of the first conductive member  13   a . As illustrated in  FIG. 11 , each piece of setting information is associated with the communication system of the electronic device  10  and the communication band used for the communication system. In one embodiment, communication using a single band of 700 MHz band and communication using a single band of 800 MHz are each associated with the setting information indicating the second circuit  23 . Meanwhile, communication using a single band of 2 GHz and simultaneous multiband communication are each associated with the setting information indicating the first circuit  22 . 
     The processor  30  includes one or more general purpose processors that read a specific program to implement a specific function or one or more dedicated processors for a specific processing. The processor  30  controls the entire operation of the electronic device  10 . 
     For example, the processor  30  controls the operation of the switching circuit  24  and switches the circuit connecting the first conductive member  13   a  and the second GND terminal  21   a  of the substrate  14  between the first circuit  22  and the second circuit  23  depending on the communication band for use. Specifically, the processor  30  detects the communication band employed by the communication system for use. In one embodiment, the processor  30  detects the communication band used in any one of the communication systems, such as communication using a single band of 700 MHz, communication using a single band of 800 MHz, communication using a single band of 2 GHz and simultaneous multiband communication. The processor  30  reads the setting information corresponding to the detected communication band from the memory  29 . The processor  30  switches the circuit connecting the first conductive member  13   a  and the second GND terminal  21   a  of the substrate  14  to the circuit indicated by the read out setting information. Switching of the circuit is performed by driving a switch included in the switching circuit  24 . 
     With this configuration, the switching circuit  24  connects the first conductive member  13   a  and the second GND terminal  21   a  of the substrate  14  through the second circuit  23  in communication using a single band of 700 MHz band and communication using a single band of 800 MHz. Meanwhile, the switching circuit  24  connects the first conductive member  13   a  and the second GND terminal  21   a  of the substrate  14  through the first circuit  22  in communication using a single band of 2 GHz and simultaneous multiband communication. 
     An operation of the electronic device  10  to dynamically switch the connection state of the second connection path  19   a  of the first conductive member  13   a  will be described with reference to  FIG. 12 . 
     In step S 100 , the processor  30  detects the communication band used by the communication system for use. 
     In step S 101 , the processor  30  reads out the setting information corresponding to the detected communication band from the memory  29 . 
     In step S 102 , the processor  30  controls the switching circuit  24  and switches the circuit connecting the first conductive member  13   a  and the second GND terminal  21   a  of the substrate  14  between the first circuit  22  and the second circuit  23  depending on the setting information read out in step S 101 . 
     As described above, the electronic device  10  according to one embodiment switches the circuit connecting the first conductive member  13   a  and the second GND terminal  21   a  of the substrate  14  between the first circuit  22  and the second circuit  23  having an impedance lower than that of the first circuit  22  depending on to the communication band for use. This configuration allows for reduction in deterioration of the antenna  12  characteristics of the antenna corresponding to a plurality of communication bands. 
     Although the present disclosure has been described with reference to the accompanying drawings and embodiments, it is to be noted that various changes and modifications will be apparent to those skilled in the art based on the present disclosure. Therefore, such changes and modifications are to be understood as included within the scope of the present disclosure. For example, the functions and the like included in the members, steps, and the like may be reordered in any logically consistent way. Furthermore, members, steps, and the like may be combined into one or divided. 
     For example, specific configurations of the first circuit  22  and the second circuit  23  each having frequency characteristics of impedance different from each other are not limited to the above described embodiment. The specific configurations of the first circuit  22  and the second circuit  23  may each be adjusted depending on the shape and the size of the antenna  12  and the conductive member  13  and the positional correlation between them. 
     In the above described embodiment, the electronic device  10  is described assuming that it can communicate using four types of communication systems, such as communication using a single band of 700 MHz, communication using a single band of 800 MHz, communication using a single band of 2 GHz and simultaneous multiband communication using the above three communication bands. However, the communication system is not limited thereto. The electronic device  10  may communicate using communication systems, such as communication using a single band of 800 MHz, communication using a single band of 1.7 GHz, communication using a single band of 2 GHz and simultaneous multiband communication using these three communication bands. Moreover, the electronic device  10  may communicate using communication systems, such as communication using a single band of 800 MHz, communication using a single band of 1.5 GHz, communication using a single band of 2 GHz and simultaneous multiband communication using these three communication bands. Further, the electronic device  10  may communicate using communication systems, such as communication using a single band of 900 MHz, communication using a single band of 1.8 GHz, communication using a single band of 2.1 GHz and simultaneous multiband communication using these three communication bands. Also in these cases, the electronic device  10  may only need to switch the circuit connecting the first conductive member  13   a  and the second GND terminal  21   a  of the substrate  14  between the first circuit  22  and the second circuit  23  having an impedance lower than that of the first circuit depending on the communication band for use.