Electronic device

Abstract

There is provided an electronic device including an antenna for performing wireless communication, a noise source causing generation of a radiation current, and a conductive member disposed on a propagation path of the radiation current from the noise source to the antenna and having a protruding portion protruding from the propagation path. The electrical length of the tip to the protruding portion is equal to or greater than one eighth but equal to or less than three eighth of the wavelength used in wireless communications.

Description

Technical Field

[0001] The present invention relates to an electronic device having an antenna for wireless communication. Background Art

[0002] An electronic device is known that can perform wireless communication connection with another communication device, for example, wireless local area network (LAN) communication based on the IEEE802.11 standard or wireless communication based on the Bluetooth (registered trademark) standard. Such an electronic device has an antenna for performing wireless communication. Summary of the Invention

[0003] [Technical Issues]

[0004] Electronic components installed in electronic devices contain potential noise sources that generate radiated currents, such as communication connectors used to transmit and receive signals externally at relatively high clock speeds. Radiated currents generated by these noise sources propagate through the ground plane of the electronic device's circuits and can adversely affect wireless communications using antennas.

[0005] The present invention has been made in view of the circumstances as described above, and one of the objects of the present invention is to provide an electronic device capable of suppressing propagation of radiation current from a noise source to an antenna.

[0006] [Solution to the problem]

[0007] According to the present invention, there is provided an electronic device including an antenna for performing wireless communication, a noise source that causes a radiation current to be generated, and a conductive member disposed on a propagation path of the radiation current from the noise source to the antenna and having a protruding portion that protrudes from the propagation path. The electrical length to the tip of the protruding portion is equal to or greater than one-eighth but equal to or less than three-eighths of a wavelength used in wireless communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] [ Figure 1 ]

[0009] Figure 1 is a diagram showing a board incorporated in an electronic device according to a first embodiment of the present invention.

[0010] [ Figure 2 ]

[0011] Figure 2 This is a diagram showing a conductive member included in the electronic device according to the first embodiment of the present invention, as viewed from a horizontal direction.

[0012] [ Figure 3 ]

[0013] Figure 3: is a diagram showing an example of the distribution of the radiation current in a case where no conductive member is provided.

[0014] [ Figure 4 ]

[0015] Figure 4 is a diagram showing an example of the distribution of radiation current in a case where a conductive member is provided.

[0016] [ Figure 5 ]

[0017] Figure 5 is a diagram showing a plurality of boards incorporated in an electronic device according to a second embodiment of the present invention.

[0018] [ Figure 6 ]

[0019] Figure 6 It is a diagram for explaining a board incorporated in an electronic device according to a modified example of the present invention.

[0020] [ Figure 7 ]

[0021] Figure 7 This is a diagram showing a conductive member included in an electronic device according to another modified example of the present invention, as viewed from a horizontal direction.

[0022] [ Figure 8 ]

[0023] Figure 8 This is a diagram showing a conductive member included in an electronic device according to another modified example of the present invention, as viewed from a horizontal direction.

[0024] [ Figure 9 ]

[0025] Figure 9 This is a diagram showing a conductive member included in an electronic device according to another modified example of the present invention, as viewed from a horizontal direction. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present invention are described in detail with reference to the accompanying drawings.

[0027] [First embodiment]

[0028] The electronic device 1a according to the first embodiment of the present invention is, for example, a personal computer, a fixed game device, a portable game device, a smart phone, etc., and includes a board 10, an antenna 20 for wireless communication connection with another electronic device, and a connector 30 for wired communication connection with another electronic device. Figure 1 An exemplary appearance of the board 10 incorporated in the electronic device 1 a is shown.

[0029] The board 10 is an electronic circuit board on which various circuit elements for realizing the functions of the electronic device 1a are mounted. Figure 1 The plate 10 is shown as a flat plate shaped like a rectangle in plan view. Hereinafter, for ease of explanation, the transverse and longitudinal directions of the plate 10 are represented by the X-axis and the Y-axis, respectively, and it is assumed that the plate 10 is arranged parallel to the XY plane. Furthermore, the direction perpendicular to the plate 10 is represented by the Z-axis, where the direction toward the front surface side of the plate 10 is referred to as the positive Z-axis direction, and the direction toward the rear surface side of the plate 10 is referred to as the negative Z-axis direction.

[0030] Antenna 20 is a circuit element used by electronic device 1a to wirelessly communicate with another communication device. In this embodiment, antenna 20 is a pattern antenna formed on board 10. Furthermore, antenna 20 is positioned near one of the four sides that form the outer boundary of board 10. The side of each side that forms the outer boundary of board 10, the side positioned closest to antenna 20, is hereinafter referred to as side N. In this example, side N is the side that extends along the X-axis direction.

[0031] Connector 30 is a circuit component used to establish a wired communication connection between electronic device 1a and another communication device. It can be, for example, a Universal Serial Bus (USB) receptacle for communicating with another USB device based on the USB 3.0 standard. Alternatively, connector 30 can be a High-Definition Multimedia Interface (HDMI; registered trademark) connector for transmitting and receiving video signals based on the HDMI standard. In this embodiment, connector 30 is fixed along side N, facing outward (the negative side in the Y-axis direction).

[0032] When another communication device is connected to connector 30 via a cable or the like and communication is established between electronic device 1a and the connected communication device, a radiation current is generated in the ground pattern formed on the front surface of board 10. This radiation current propagates through the ground of board 10 on which connector 30 is mounted, which may adversely affect other circuit elements. In this regard, connector 30 acts as a noise source.

[0033] The radiated current generated from connector 30 propagates primarily along the outer edge of board 10. In this embodiment, since both antenna 20 and connector 30 are located along side N of board 10, unless countermeasures are taken, there is a high probability that the radiated current generated from connector 30 and propagating along side N of board 10 will interfere with wireless communication with antenna 20. To suppress such radiated current, screws 40 are secured near side N of board 10.

[0034] The screw 40 is a conductive member formed of a conductive material such as iron, and is provided at a position near the side N of the board 10 between the antenna 20 and the connector 30. In addition, the screw 40 has a head portion 41 located on the front surface side of the board 10 and a body portion 42 provided so as to extend through the through hole 11 defined in the board 10 and face in the negative direction of the Z axis.

[0035] Figure 2 This diagram schematically illustrates screw 40 secured to board 10, viewed from a horizontal direction. The radiation current generated by connector 30 propagates along the ground pattern formed on the front surface of board 10. Since the bottom surface 41a of head 41 of screw 40 contacts this ground pattern, screw 40 is electrically connected to the radiation current propagation path. Consequently, the radiation current flows along a bypass path along the surface of body portion 42 protruding from bottom surface 41a, with body portion 42 of screw 40 acting as a stub. This illustrates how the propagation of radiation current is suppressed at the location of screw 40.

[0036] In order for the screw 40 to effectively suppress the propagation of radiation current, the electrical length of the portion serving as the stub is desirably a length corresponding to the wavelength of the noise to be suppressed. In the following description, the portion serving as the stub is referred to as the stub portion. The stub portion is a protruding portion formed as part of a conductive member (in this example, the screw 40) that is used to suppress the propagation of radiation current. If no conductive member is provided, this protruding portion protrudes relative to the portion that would electrically contact the propagation path of the radiation current and is not electrically connected to any other conductive member. In the following description, the physical length of the stub portion is represented by L, and the electrical length of the stub portion is represented by Le. In this embodiment, the entire body portion 42 of the screw 40 serves as the stub portion, and the length of the body portion 42, namely, the length from the bottom surface 41a of the head portion 41 to the tip 42b of the body portion 42, is substantially the same as the stub portion length L.

[0037] When the wavelength corresponding to the frequency used by antenna 20 for wireless communications is represented by λ, the electrical length Le of the stub portion of screw 40 is preferably equal to or greater than one-eighth of λ but equal to or less than three-eighths of λ, and more preferably is approximately λ / 4. When the stub portion is disposed in air without any object in contact with it, the electrical length Le of the stub portion is approximately the same as the actual length L. Conversely, when the stub portion has a surface in contact with a dielectric, the electrical length Le of this surface portion becomes greater than the actual length, depending on the relative permittivity of the dielectric. Specifically, when a portion of the stub portion having a length Lx contacts a dielectric having a relative permittivity ε, the electrical length Lex of this portion becomes √ε times the length Lx. Therefore, the larger the portion in contact with the dielectric, the smaller the physical length of the main body 42 of screw 40 required to suppress radiation current of the same wavelength.

[0038] In this embodiment, the screw 40 is fixed to the screw receiver 45, as shown in FIG. Figure 2 As shown. The screw receiver 45 is formed of a dielectric and has a screw hole 45a for engaging with the screw 40. The screw 40 is fastened to the screw receiver 45 with the board 10 interposed therebetween, so that the screw 40 is fixed to the board 10. The screw receiver 45 makes the electrical length Le of the main body portion 42 of the screw 40 greater than the physical length L.

[0039] Furthermore, screw receiver 45 can be a member that is secured to the housing of electronic device 1a, etc. With this configuration, screw 40 not only functions to suppress radiation current but also serves to secure board 10, incorporated into electronic device 1a, to the housing. In other words, by setting the length L of the short column portion of screw 40 to correspond to the wavelength of radio waves used in wireless communications, the screw 40 used to secure board 10 can be given the additional function of suppressing the propagation of radiation current. Consequently, radiation current can be suppressed without requiring additional features.

[0040] Figure 3 and Figure 4 The simulation results of the distribution of the radiation current generated from the connector 30 provided on the board 10 are shown, and each figure depicts the board 10 viewed in a plan view. In these figures, the portion with higher density indicates where a stronger radiation current is generated. Figure 3 shows the distribution of the radiation current in the absence of the screw 40, while Figure 4 FIG4 shows the distribution of the radiation current in the presence of the screw 40. In the absence of the screw 40, the radiation current generated from the connector 30 mainly propagates along the propagation path along the side N where the connector 30 is provided, as shown in FIG4. Figure 3 At the same time, in the presence of screw 40, as shown Figure 4 As shown, although a strong radiation current appears around screw 40, this radiation current does not propagate beyond screw 40, and the area near antenna 20, located on the opposite side of connector 30 across screw 40, is substantially unaffected by this radiation current. Thus, with screw 40 in place, the effect of the radiation current generated by connector 30 on antenna 20 is suppressed.

[0041] As previously described, screw 40 is positioned along side N between connector 30 and antenna 20, effectively suppressing the propagation of radiated current from connector 30 to antenna 20. Furthermore, screw 40 can be positioned closer to connector 30 (i.e., closer to connector 30 than to antenna 20). This allows the area affected by radiated current to be narrowed.

[0042] As described above, with the electronic device 1 a according to the present embodiment, the screw 40 can suppress the propagation of the radiation current generated on the board 10 due to communication via the connector 30 , and can suppress the influence of the radiation current on the antenna 20 .

[0043] [Second embodiment]

[0044] Next, refer to Figure 5 An electronic device 1b according to a second embodiment of the present invention is described. Note that in the following description, constituent elements that perform actions similar to those of the corresponding constituent elements in the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0045] In this embodiment, the antenna 20 and the connector 30 are not on the same board, but are provided on different boards. Specifically, the antenna 20 is provided on the board 10 as the main board of the electronic device 1b, and the connector 30 is provided on the sub-board 50.

[0046] The board 10 has a rectangular shape in a plan view and is arranged parallel to the XY plane as in the first embodiment. In addition, the antenna 20 is provided along the side N extending parallel to the X axis.

[0047] Sub-board 50 is positioned parallel to the XZ plane, on the negative Y-axis side relative to side N of board 10. That is, sub-board 50 is positioned perpendicular to board 10. Connector 30 is positioned on sub-board 50, facing the negative Y-axis direction.

[0048] Although antenna 20 and connector 30 are mounted on separate boards in this embodiment, in typical electronic devices, the ground is shared across the boards. That is, the ground for board 10 and the ground for sub-board 50 are electrically connected. Therefore, even if antenna 20 and connector 30 are mounted on separate boards, the radiated current generated by connector 30 could propagate to antenna 20, interfering with wireless communication with antenna 20. To address this issue, as in the first embodiment, a conductive member such as a screw, serving as a short stud, is placed midway along the propagation path of the radiated current from connector 30 to antenna 20. This suppresses the propagation of the radiated current.

[0049] Specifically, in this embodiment, the shielding member 60 is fixed to the board 10 , and the shielding member 70 is fixed to the sub-board 50 .

[0050] The shield 60 is formed of, for example, a conductive material such as a metal plate having a flat plate shape, and is fixed to the board 10 in such a manner as to cover at least a portion of the front surface of the board 10. Note that the shield 60 is provided not to cover the antenna 20 but to cover other areas of the board 10. The shield 60 is in contact with the ground pattern of the board 10 and is therefore electrically connected to the ground of the board 10.

[0051] Furthermore, in this embodiment, the shield 60 is formed with a blade portion 61. The blade portion 61 has a plate shape placed parallel to the front surface of the board 10 and is provided at a position such that the blade portion 61 protrudes from the main body of the shield 60 toward the Y-axis negative direction side and does not overlap with the board 10.

[0052] The shield 70 is also formed of a conductive material such as a metal plate like the shield 60, and is fixed to the sub-board 50 in such a manner as to cover at least a portion of the front surface of the sub-board 50. In addition, the shield 70 is in contact with the ground pattern of the sub-board 50 and is thus electrically connected to the ground of the sub-board 50.

[0053] Furthermore, in this embodiment, the shield 70 is formed with a blade portion 71. The blade portion 71 is plate-shaped and perpendicular to the front surface of the sub-plate 50. The blade portion 71 is formed so as to bend at the end of the shield 70's main body on the negative X-axis side and extend in the negative Y-axis direction. The blade portion 71 is also connected to a bent portion 72 extending in a direction orthogonal to the blade portion 71. Specifically, the bent portion 72 is connected to the end of the blade portion 71 on the positive Z-axis side and extends in the negative Y-axis direction. It is arranged parallel to the front surface of the substrate 10. Furthermore, when the shield 60 and shield 70 are respectively fixed to the plate 10 and the sub-plate 50, the bent portion 72 overlaps and contacts the distal end of the blade portion 61 of the shield 60.

[0054] Furthermore, through-holes are provided in the bent portion 72 and the top portion of the blade portion 61, respectively, with these through-holes positioned overlapping one another. In this embodiment, screws 40 having a short column portion are fitted into these through-holes for securing. Note that, as in the first embodiment, the screws 40 can be fastened to screw receivers (not shown) that are secured to, for example, the housing of the electronic device 1b. Thus, the shielding members 60 and 70 are fastened together by the screws 40, and the screws 40 are electrically connected to both the shielding members 60 and 70.

[0055] With this configuration, assuming the absence of screw 40, it is believed that the radiation current generated from connector 30 would primarily propagate along a path from the ground of sub-board 50 to shield 70, from the bent portion 72 of shield 70 to the blade portion 61 of shield 60, and further from shield 60 to the ground of board 10, thereby affecting antenna 20. By placing screw 40, acting as a short stud, midway along the radiation current propagation path, the effect of the radiation current on antenna 20 can be suppressed.

[0056] Specifically, as in the first embodiment, the bottom surface of the head portion 41 of the screw 40 contacts the blade portion 61, so that the main body portion 42 of the screw 40 functions as a stub portion. By setting the electrical length Le of the stub portion to a value greater than (1 / 8)λ and less than (3 / 8)λ (λ is the wavelength corresponding to the frequency used by the antenna 20 for wireless communication), it is possible to prevent the component of the radiation current having a wavelength λ from propagating beyond the screw 40.

[0057] In this embodiment, the screws 40 are fixed to the shields 60 and 70. Thus, even when it is difficult to directly fix the screws 40 to the board 10 or the sub-board 50 due to layout problems, the effect of suppressing the propagation of radiation current can be obtained.

[0058] Furthermore, when screw 40 is fastened to a screw receiver formed of a dielectric as described above, the electrical length Le of the main portion 42 of screw 40 becomes greater than the physical length L due to contact with the screw hole provided in the screw receiver formed of the dielectric. Therefore, the propagation of radiation current of the target wavelength can be suppressed with a relatively small length L. Furthermore, screw 40 is fastened to the screw receiver to secure shield 60 and shield 70 together, meaning that screw 40 secures shield 60 and shield 70. When this screw receiver is secured to the housing of electronic device 1b, screw 40 also serves to secure the entire unit comprising board 10, sub-board 50, shield 60, and shield 70 to the housing of electronic device 1b. Therefore, as in the first embodiment, the screw 40 used to secure the various boards and shield to the housing of electronic device 1b can be additionally assigned the function of suppressing the propagation of radiation current. Consequently, radiation current can be suppressed without requiring additional structures.

[0059] [Modifications]

[0060] The embodiments of the present invention are not limited to the above-described embodiments and may be modified in various ways.

[0061] For example, the antenna 20 and the connector 30 may be disposed along different sides of the same board 10 . Figure 6 An example of this embodiment is shown. In the example shown in this figure, connector 30 is positioned along the side located on the negative Y-axis side, and antenna 20 is positioned along a side located on the positive X-axis side that is different from the side located on the negative Y-axis side. In this case as well, since the radiated current generated by connector 30 propagates along the outer edge of board 10, placing screw 40 in the middle of this propagation path can suppress the propagation of the radiated current.

[0062] Furthermore, even when the antenna 20 and connector 30 are provided on different boards as in the second embodiment, the screw 40 can be fixed to either board or to another location on the shield 60 or 70. Furthermore, the orientation of the screw 40 can be altered from the above-described orientation, and for example, the screw 40 can be provided in the opposite orientation. In any case, by fixing the screw 40, which serves as a short post, in the middle of the propagation path of the radiation current from the connector 30 to the antenna 20, the propagation of the radiation current can be suppressed.

[0063] In addition, although the screw 40 is directly in contact with the ground of the board 10 or the shield 60 on the propagation path of the radiation current in the above description, this is not the only example. The screw 40 may be electrically connected to the propagation path of the radiation current through capacitive coupling.

[0064] Figure 7 is a diagram showing an example of such an embodiment. Figure 2 Same, Figure 7 The screw 40 is shown viewed in the horizontal direction. In the example of the figure, the dielectric layer 12 is formed on the front surface of the board 10, and the screw 40 is not in direct contact with the ground of the board 10. However, the ground pattern of the front surface of the board 10 is capacitively coupled to the bottom surface 41a of the head 41 of the screw 40, with the dielectric layer 12 interposed therebetween. In this case as well, as in the first embodiment, the main body portion 42 protruding from the bottom surface 41a of the head 41 of the screw 40 serves as a short column portion. Thereby, the propagation of the radiation current of the wavelength corresponding to the electrical length Le of the main body portion 42 of the screw 40 can be suppressed. It is to be noted that although in Figure 7 Although not shown in the figure, the screw 40 can be fixed to the Figure 2 The dielectric in the screw receiver is formed.

[0065] In the description so far, the main body portion 42 of the screw 40 is used as the short column portion in any embodiment. However, the embodiments of the present invention are not limited to such a case, and any conductive member can be used instead of the screw 40 as long as the conductive member is electrically connected to the propagation path of the radiation current and has a short column portion protruding from the propagation path.

[0066] For example, when the screw 40 is fixed to a screw receiver formed of a conductor rather than a dielectric, the screw 40 alone does not function as a stub. However, since the main body 42 of the screw 40 contacts the screw receiver formed of a conductor, the propagation of radiation current can be suppressed when the entire unit including the screw receiver formed of a conductor functions as a stub.

[0067] Figure 8 1 is a diagram showing an example of this embodiment. In the example of the figure, although the screw 40 is as shown in FIG. Figure 2 The screw receiver 45 is fastened to a screw hole 45a defined in the screw receiver 45 as in the first embodiment, but the screw receiver 45 has a generally rod-shaped shape and, unlike the first embodiment, is formed from a conductive material. Note that in the example shown in the figure, the upper surface 45b of the screw receiver 45 contacts the rear surface of the board 10. Therefore, the front surface portion of the screw receiver 45 protrudes from the ground of the board 10, which is included in the propagation path of the radiation current, and serves as a stub. In other words, the longitudinal length of the screw receiver 45 (the length from the upper surface 45b to the bottom surface 45c) becomes the length L of the stub.

[0068] The conductive member having the portion serving as the stub portion may be a positioning boss. Figure 9 1 is a diagram showing an example of such an embodiment. In the example of the figure, the boss 80 is inserted through the through hole 11 defined in the plate 10, and the end of the boss 80 is inserted into the hole 85a defined in the boss receiver 85 formed of the dielectric. The plate 10 is thus positioned relative to the boss receiver 85. It should be noted that Figure 2 Like the screw receiver 45 in FIG. 1 , the boss receiver 85 is a member fixed to the housing of the electronic device.

[0069] In this example, the boss 80 has a side surface that contacts the through hole 11 defined in the board 10, so that the boss 80 is electrically connected to the ground of the board 10. Therefore, the portion of the boss 80 that protrudes from the rear surface side of the circuit board 10 serves as a stub portion. In this case, the length L of the stub portion is equal to the length of the portion of the boss 80 from the rear surface of the circuit board 10 to the end portion, as shown in the figure.

[0070] As described above, the conductive member having the portion serving as the stub portion may be a member having any of various shapes and sizes as a whole, but preferably, the portion serving as the stub portion is substantially rod-shaped, and preferably, the conductive member has such a shape that the longitudinal length L of the portion serving as the stub portion (the length to the tip of the portion protruding from the propagation path of the radiation current) is greater than its length in the other direction.

[0071] It should be noted that while only one conductive member having a stub portion is provided between antenna 20 and connector 30 in the above description, multiple such conductive members may be provided. In this case, by varying the electrical lengths of the stub portions in each conductive member, radiation currents of multiple wavelengths can be suppressed. For example, if antenna 20 performs wireless communications at two wavelengths (i.e., λ1 and λ2), by providing two conductive members between antenna 20 and connector 30 (i.e., a conductive member having a stub portion with an electrical length Le corresponding to wavelength λ1 and a conductive member having a stub portion with an electrical length Le corresponding to wavelength λ2), noise reduction can be achieved at both wavelengths.

[0072] Furthermore, while the connector 30, which performs relatively high-speed communication, is described above as a noise source causing the generation of radiated current, this is not restrictive. Any of various circuit elements that generate radiated current that propagates through the ground of the circuit in the electronic device can be a noise source. Furthermore, while the antenna 20 is described above as a pattern antenna formed on the board 10, this is not restrictive. The antenna 20 can be any of a variety of antennas connected to the board 10.

[0073] [Reference Signs List]

[0074] 1a, 1b: Electronic equipment

[0075] 10: Board

[0076] 20: Antenna

[0077] 30: Connector

[0078] 40: Screw

[0079] 45: Screw Receiver

[0080] 50: Vice board

[0081] 60, 70: Shielding parts

[0082] 80: Boss

[0083] 85: Boss Receiver

Claims

1. An electronic device comprising: an antenna for performing wireless communication; a noise source causing a radiation current to be generated; and a conductive member provided on a propagation path of the radiation current from the noise source to the antenna and having a protruding portion protruding from the propagation path, wherein an electrical length to the tip of the protruding portion is equal to or greater than one eighth but equal to or less than three eighths of a wavelength used in the wireless communication.

2. The electronic device according to claim 1, further comprising: board, the antenna is connected to the board, Wherein, the conductive member is a screw fixed to the plate.

3. The electronic device according to claim 1, further comprising: a board to which the antenna is connected; and a shield covering at least a portion of the plate, Wherein, the conductive member is a screw fixed to the shielding element.

4. The electronic device according to claim 3, further comprising: a second board different from the board to which the antenna is connected, the noise source being connected to the second board; and a second shield covering at least a portion of the second plate, the second shielding member having a portion overlapping with the shielding member, The shielding member and the second shielding member are fastened together at the overlapping portion by screws.

5. The electronic device according to any one of claims 2 to 4, wherein: The screw is secured to a screw fixture formed of a dielectric.

6. The electronic device according to claim 1, further comprising: board, the antenna is connected to the board, wherein the screws are fixed to the plate, and The conductive member is a screw receiver to which the screw is fixed.

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