Wireless communication device

Abstract

To reduce the size of a wireless communication device installed in a vehicle.SOLUTION: The wireless communication device that is capable of wireless communication with an electronic key of a vehicle includes: a circuit board which is square in plan view; a first antenna that is placed at a predetermined distance away along a first edge of the circuit board from one vertex of the circuit board; a second antenna that is placed at a predetermined distance away from the vertex of the circuit board along a second edge of the circuit board that is different from the first edge; and a first GND placed near the vertex of the circuit board.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to wireless communication devices. [Background technology]

[0002] When there is only one antenna for wireless communication, there are frequencies and angles at which wireless communication performance deteriorates depending on the antenna's characteristics (frequency band and directivity). Patent Document 1 discloses that, in a shark antenna mounted on a vehicle, two antennas with different frequency characteristics are placed on both sides of a substrate to complement the frequency characteristics. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2016-504799 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a known technology in which a wireless communication device mounted on a vehicle receives instructions via wireless communication from an electronic key of the vehicle and controls the operation of the vehicle. By mounting two antennas on the wireless communication device, it is possible to suppress deterioration of communication quality, as disclosed in Patent Document 1. Therefore, there is a demand for miniaturization of wireless communication devices equipped with two antennas.

[0005] The present disclosure aims to reduce the size of a wireless communication device that is mounted on a vehicle and that has at least two antennas. [Means for solving the problem]

[0006] The present disclosure provides a wireless communication device that is mounted on a vehicle and is capable of wireless communication with the vehicle's electronic key and a smartphone, the wireless communication device comprising: a substrate that is rectangular in plan view; a first antenna that is positioned a predetermined distance from one vertex of the substrate along a first side of the substrate and extends along the first side; a second antenna that is positioned a predetermined distance from the vertex of the substrate along a second side different from the first side of the substrate and extends along the second side; and a first GND that is positioned near the vertex of the substrate.

[0007] These comprehensive or specific aspects may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to reduce the size of a wireless communication device that is mounted on a vehicle and that has at least two antennas. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing a vehicle and an electronic key according to a first embodiment; [Figure 2] FIG. 1 is a block diagram showing an example of the configuration of an ECU and an electronic key according to a first embodiment. [Figure 3] 1 is a flowchart showing an example of a method for measuring the distance between an ECU and an electronic key according to the first embodiment. [Figure 4] FIG. 1 is a perspective view showing a configuration example of a board of an ECU according to a first embodiment; [Figure 5] Graph showing an example of antenna directivity of antenna 21A and antenna 21B according to embodiment 1. [Figure 6] FIG. 10 is a perspective view showing a configuration example of a first layer of a substrate of an ECU according to a second embodiment; [Figure 7] FIG. 10 is a plan view showing a configuration example of a first layer (L1 layer) of a substrate of an ECU according to a second embodiment; [Figure 8] FIG. 10 is a plan view showing a configuration example of a second layer (L2 layer) of a board of an ECU according to a second embodiment; [Figure 9] FIG. 10 is a plan view showing a configuration example of a third layer (L3 layer) of the substrate of the ECU according to the second embodiment; [Figure 10] FIG. 10 is a plan view showing a configuration example of a fourth layer (L4 layer) of a substrate 50 of an ECU according to a second embodiment. [Figure 11] Graph showing an example of antenna directivity of antenna 21A and antenna 21B according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with appropriate reference to the drawings. However, more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0011] (Embodiment 1) FIG. 1 is a schematic diagram showing a vehicle 2 and an electronic key 10 according to the first embodiment.

[0012] An ECU 20 installed in a vehicle 2 and an electronic key 10 carried by a user 1 of the vehicle 2 can communicate wirelessly. When a user 1 of the vehicle 2 approaches the vehicle 2 while carrying the electronic key 10 for the vehicle 2, distance measurement is performed between the ECU 20 and the electronic key 10 (FOB key) using the phase difference and radio wave intensity (RSSI) of radio waves. If it is determined that the vehicle 2 is within a predetermined distance, and if the vehicle 2 is a motorcycle, the user 1 can turn a knob on the vehicle 2 to unlock the handlebar lock and activate the ignition, and press an engine start switch to start the engine. If it is determined that the vehicle 2 is within a predetermined distance, and if the vehicle 2 is a four-wheeled motor vehicle, the user 1 can touch a door handle of the vehicle 2 to unlock the door, or turn a start / stop switch or knob to unlock the handlebar lock, activate the ignition, and start the engine. ECU stands for Electronic Control Unit.

[0013] The ECU 20 measures the distance to the electronic key 10 using a wireless signal (radio wave). In the first embodiment, a configuration and method for accurately measuring the distance between the ECU 20 and the electronic key 10 using a wireless signal will be described. In the first embodiment, an example will be described in which the vehicle 2 is a motorcycle. However, the vehicle 2 is not limited to a motorcycle (motorcycle), and may be, for example, a four-wheeled motor vehicle such as a car or truck, or a special-purpose vehicle such as a forklift or excavator. Furthermore, the electric key may be interpreted as an FOB key.

[0014] <Block configuration> FIG. 2 is a block diagram showing an example of the configuration of the ECU 20 and the electronic key 10 according to the first embodiment.

[0015] The ECU 20 includes an antenna 21A, an antenna 21B, a power feeder 22A, a power feeder 22B, a changeover switch 23, and a control circuit 24. The antenna 21A, the antenna 21B, the power feeder 22A, the power feeder 22B, the changeover switch 23, and the control circuit 24 may constitute a wireless communication device.

[0016] The antenna 21A is connected to the changeover switch 23 through a power feeder line 22A. The antenna 21B is connected to the changeover switch 23 through a power feeder line 22B. The changeover switch 23 is connected to a control circuit 24.

[0017] The control circuit 24 controls the changeover switch 23 to switch between the power supply to the power feeder 22A and the antenna 21A and the power supply to the power feeder 22B and the antenna 21B. That is, the control circuit 24 controls the changeover switch 23 to switch between the use of the antenna 21A and the antenna 21B.

[0018] The control circuit 24 may transmit and receive information to and from each device mounted on the vehicle 2 via a Controller Area Network (CAN), which is an example of on-board communication, and / or serial communication (for example, UART), to control the vehicle.

[0019] The control circuit 24 may detect the state and switching of a knob switch 31 mounted on the vehicle 2. The control circuit 24 may control the display of an indicator 32 mounted on the vehicle 2. The control circuit 24 may control the lighting, blinking, extinguishing, etc. of a turn signal 33 mounted on the vehicle 2.

[0020] The electronic key 10 includes antennas 11A and 11B, power feeders 12A and 12B, a selector switch 13, a control circuit 14, and an operation button 15. The antennas 11A and 11B, power feeders 12A and 12B, the selector switch 13, and the control circuit 14 may form a wireless communication device. The electronic key 10 may also be composed of only the antenna 11A, power feeder 12A, control circuit 14, and operation button 15.

[0021] The antenna 11A is connected to the changeover switch 13 through a power feeder line 12A. The antenna 11B is connected to the changeover switch 13 through a power feeder line 12B. The changeover switch 13 is connected to a control circuit 14.

[0022] The control circuit 14 controls the changeover switch 13 to switch between supplying power to the power feeder 12A and the antenna 11A and supplying power to the power feeder 12B and the antenna 11B. That is, the control circuit 14 controls the changeover switch 13 to switch between using the antenna 11A and the antenna 11B. The control circuit 14 detects the operation of the operation button 15.

[0023] The ECU 20 and the electronic key 10 can communicate wirelessly via antennas 21A, 21B, 11A, and 11B. The wireless communication method is Bluetooth (registered trademark). In this case, the control circuit 24 may be an IC chip for controlling Bluetooth wireless communication. Note that Bluetooth may be either Bluetooth Low Energy or Bluetooth Classic. However, the wireless communication method is not limited to Bluetooth and may be, for example, LTE, 4G, 5G, Wi-Fi (registered trademark), or the like.

[0024] Once the ECU 20 and electronic key 10 are paired, the ECU 20 sends a distance measurement start trigger to the electronic key 10 within their communication range, and performs distance measurement at regular intervals using the radio wave phase difference and RSSI. The ECU 20 calculates the distance to the electronic key 10, and if it determines that it is within a predetermined distance, the user 1 can turn the knob on the vehicle 2 to unlock the steering wheel, turn on the ignition, and press the engine start switch to start the engine.

[0025] At this time, the ECU 20 executes the command if the electronic key 10 is within a predetermined distance, and does not execute the command if the electronic key 10 is outside the predetermined distance. This is to prevent, for example, an unauthorized person who is not the owner of the vehicle 2 from transmitting an unauthorized wireless signal to the vehicle 2 from a distant location to unlock the vehicle 2. For this reason, the ECU 20 measures the distance to the electronic key 10 using wireless communication.

[0026] In this embodiment, the electronic key 10 and the ECU 20 each have two antennas, which provides a spatial diversity effect and prevents the occurrence of angles or frequency bands where distance cannot be measured accurately. However, the number of antennas each of the electronic key 10 and the ECU 20 is not limited to two and may be three or more.

[0027] <How to measure distance> FIG. 3 is a flowchart showing an example of a method for measuring the distance between the ECU 20 and the electronic key 10 according to the first embodiment.

[0028] The control circuit 24 of the ECU 20 turns on the distance measurement start flag (S11).

[0029] The control circuit 24 of the ECU 20 selects one of the unselected paths between the ECU 20 and the electronic key 10 (S12). For example, in the configuration shown in FIG. 2, there are four paths: a path 41 for communication between the antenna 21A and the antenna 11A, a path 42 for communication between the antenna 21A and the antenna 11B, a path 43 for communication between the antenna 21B and the antenna 11A, and a path 44 for communication between the antenna 21B and the antenna 11B. In step S12, one of the four paths 41, 42, 43, and 44 that has not yet been selected is selected. In the following description of FIG. 3, the path selected in step S12 is referred to as the selected path.

[0030] The control circuit 24 of the ECU 20 transmits radio waves on two or more channels to the electronic key 10 via the selected path (i.e., from an antenna corresponding to the selected path) (S13). Radio waves on two or more channels refer to two or more radio waves with different frequencies.

[0031] The control circuit 14 of the electronic key 10 receives the radio waves transmitted from the ECU 20 in step S13 via the selected path (i.e., via the antenna corresponding to the selected path), and temporarily stores the Received Signal Strength Indicator (RSSI) and In-Phase / Quadrature-Phase (IQ) of the received signal in memory (not shown) (S14).

[0032] The control circuit 24 of the ECU 20 (or the control circuit 14 of the electronic key 10) determines whether all four paths 41, 42, 43, 44 have been selected (S15).

[0033] First, the case where an unselected path remains among the four paths 41, 42, 43, and 44 (S15: YES) will be described.

[0034] The control circuit 14 of the electronic key 10 transmits radio waves on two or more channels to the ECU 20 via the selected path (i.e., from the antenna corresponding to the selected path) (S16).

[0035] The control circuit 14 of the ECU 20 receives the radio waves transmitted from the electronic key 10 in step S16 via the selected path (i.e., via the antenna corresponding to the selected path) and temporarily stores the RSSI and IQ of the received signal in memory (not shown) (S17). Then, the process returns to step S12.

[0036] Next, a case where all four paths 41, 42, 43, and 44 are selected (S15: NO) will be described.

[0037] The control circuit 14 of the electronic key 10 transmits radio waves on two or more channels to the ECU 20 via the last selected path (i.e., from the antenna corresponding to the selected path), and also transmits all RSSI and IQ values ​​temporarily stored in memory to the ECU 20 (S21).

[0038] The control circuit 24 of the ECU 20 receives the radio waves transmitted from the electronic key 10 in step S21 via the last selected path (i.e., via the antenna corresponding to the selected path), and also receives all RSSI and IQ transmitted from the electronic key 10, and temporarily stores these in memory (S22). As a result, the memory of the ECU 20 stores the RSSI and IQ received by the ECU 20 from the electronic key 10 and the RSSI and IQ received by the electronic key 10 from the ECU 20 for each of the four paths 41, 42, 43, and 44.

[0039] The control circuit 24 of the ECU 20 identifies the path with the highest RSSI among the four paths 41, 42, 43, and 44 (S23). For example, the control circuit 24 of the ECU 20 calculates the average value (hereinafter referred to as average RSSI) of the RSSI when the ECU 20 receives the signal from the electronic key 10 and the RSSI when the electronic key 10 receives the signal from the ECU 20 for each of the four paths 41, 42, 43, and 44, and identifies the path with the highest average RSSI.

[0040] The control circuit 24 of the ECU 20 calculates the distance between the ECU 20 and the electronic key 10 based on the phase difference of the radio waves between the channels on the path identified in step S23 (hereinafter referred to as the “identified path”) (S24). For example, the control circuit 24 of the ECU 20 calculates the distance according to the following steps (A1) to (A4). (A1) The control circuit 24 converts the IQ measured on a specific path into a phase. (A2) The control circuit 24 calculates the first phase by combining the phase obtained by converting the IQ of the first channel when the ECU 20 in the specific path receives it from the electronic key 10 with the phase obtained by converting the IQ of the first channel when the electronic key 10 in the specific path receives it from the ECU 20. (A3) The control circuit 24 calculates the second phase by combining the phase obtained by converting the IQ of the second channel when the ECU 20 on the specific path receives it from the electronic key 10 with the phase obtained by converting the IQ of the second channel when the electronic key 10 on the specific path receives it from the ECU 20. (A4) The control circuit 24 calculates the phase difference between the first phase and the second phase, and calculates the distance between the ECU 20 and the electronic key 10 based on the phase difference.

[0041] As a result, since the distance between the ECU 20 and the electronic key 10 can be calculated using the specific path with the best communication quality, the distance can be measured with high accuracy.

[0042] <Configuration of the ECU board> [[ID=,10]]FIG. 4 is a perspective view showing a configuration example of the board 50 of the ECU 20 according to Embodiment 1.

[0043] As shown in FIG. 4, the ECU 20 has a board 50 having a substantially rectangular shape in plan view, and on the board 50, an antenna 21A, an antenna 21B, a feeding line 22A, a feeding line 22B, a changeover switch 23, a control circuit 24, other circuits 25, and a connector 26 are arranged.

[0044] In Embodiment 1, as shown in FIG. 4, an axis perpendicular to the plane of the board 50 is defined as the Y-axis, and axes parallel to the plane of the board 50 are defined as the X-axis and the Z-axis. Further, the X-axis is parallel to the first side 51 of the board 50, and the Z-axis is parallel to the second side 52 of the board 50. Also, for convenience of explanation, the positive direction of the Y-axis may be referred to as "up" and the negative direction of the Y-axis may be referred to as "down". Note that the expressions related to these directions are used for convenience of explanation and are not intended to limit the posture of the structure during actual use.

[0045] ] The antenna 21A is arranged in an L-shape near the vertex P1 on the first end side of the second side 52 of the board 50. The antenna 21B is arranged in an L-shape near the vertex P2 on the second end side of the second side 52 of the board 50. However, the antennas 21A and 21B may have an arrangement different from the L-shape. The antennas 21A and 21B are monopole antennas. However, the antennas 21A and 21B may be inverted F antennas or patch antennas (or microstrip antennas).

[0046] The changeover switch 23 is arranged near the center of the board 50.

[0047] Feed line 22A is disposed so as to electrically connect the end of L-shaped antenna 21A and changeover switch 23. Feed line 22B is disposed so as to electrically connect the end of L-shaped antenna 21B and changeover switch 23. The angle formed by a line that is an imaginary extension of feed line 22A and a line that is an imaginary extension of feed line 22B may be approximately 90 degrees.

[0048] A GND 61A for ensuring isolation between the power feed lines is placed in the angular gap formed by the power feed line 22A and the power feed line 22B.

[0049] Antenna 21A and antenna 21B are placed at a predetermined distance or more (for example, 30 mm or more) apart to obtain a spatial diversity effect. However, the distance between antenna 21A and antenna 21B may be less than 30 mm.

[0050] A GND hole 71A is formed in the space surrounded by the antenna 11A, the antenna 21B, and the GND 61A.

[0051] These configurations make it possible to prevent interference of radio waves and noise between antenna 21A and power feeder 22A and antenna 21B and power feeder 22B.

[0052] The control circuit 24 is disposed adjacent to the changeover switch 23 on the positive side of the X axis, and is electrically connected to the changeover switch 23 .

[0053] The GND 61B for the IC is arranged adjacent to the control circuit 24 on the negative side of the Z axis. The GND 61C for the IC is arranged adjacent to the control circuit 24 on the positive side of the Z axis.

[0054] A GND hole 71B is formed in the space surrounded by the IC GND 61B, the power feed line 22A, and the antenna 21A. A GND hole 71C is formed in the space surrounded by the IC GND 61C, the power feed line 22B, and the antenna 21B.

[0055] The other circuit 25 is disposed, for example, next to the control circuit 24 on the positive side of the X axis.

[0056] The connector 26 is disposed, for example, near a third side 53 opposite to the first side 51 of the substrate 50.

[0057] When each component and GND are arranged on a board 50 as shown in Fig. 4, for example, the components and GND can be arranged on a board 50 having a first side 51 of 95 mm and a second side 52 of 55 mm as shown in Fig. 4. However, the board 50 may be of any size.

[0058] The arrangement of the antennas 21A, 21B, the power feeders 22A, 22B, etc. shown in FIG. 4 may be applied to the circuit board of the electronic key 10.

[0059] <Antenna directivity graph> FIG. 5 is a graph showing an example of the antenna directivity of the antenna 21A and the antenna 21B according to the first embodiment.

[0060] Graph 100A in Fig. 5 shows the 360-degree antenna directivity on the XY plane of antenna 21 A. In graph 100A, solid line 101A shows the gain of horizontally polarized waves, and dotted line 102A shows the gain of vertically polarized waves.

[0061] Graph 100B in Fig. 5 shows the 360-degree antenna directivity on the XY plane of antenna 21B. In graph 100B, solid line 101B indicates the gain of horizontally polarized waves, and dotted line 102B indicates the gain of vertically polarized waves.

[0062] 4, when the antennas 21A, 21B and the power feeders 22A, 22B are arranged, radio waves can be transmitted and received in approximately 360-degree directions, as shown in graphs 100A and 100B. In other words, there are no angles or frequency bands where distance cannot be measured accurately. Therefore, regardless of the direction in which the electronic key 10 is positioned relative to the vehicle 2, the ECU 20 can accurately measure the distance to the electronic key 10.

[0063] (Embodiment 2) In Embodiment 2, the size of the substrate 50 can be made smaller than that in Embodiment 1, and the configuration of the ECU 20 (wireless communication device) having 360-degree antenna directivity with the same performance as in the case of Embodiment 1 will be described. Note that, regarding the content common to Embodiment 1 such as the distance measurement method, the description may be omitted in Embodiment 2.

[0064] <Configuration of the ECU Substrate> FIG. 6 is a perspective view showing a configuration example of the first layer of the substrate 50 of the ECU 20 according to Embodiment 2. FIG. 7 is a plan view showing a configuration example of the first layer (L1 layer) of the substrate 50 of the ECU 20 according to Embodiment 2. As shown in FIG. 7 and FIGS. 8 to 10 described later, the substrate 50 has a configuration in which the first layer (L1 layer), the second layer (L2 layer), the third layer (L3 layer), and the fourth layer (L4 layer) are laminated (that is, a multilayer substrate).

[0065] As shown in FIGS. 6 and 7, the ECU 20 has a substrate 50 having a substantially rectangular shape in plan view, and on the substrate 50, an antenna 21A, an antenna 21B, a feeding line 22A, a feeding line 22B, a switching switch 23, a control circuit 24, other circuits 25, and a connector 26 are arranged.

[0066] In Embodiment 2, as shown in FIGS. 6 and 7, an axis perpendicular to the surface of the substrate 50 is defined as the Y axis, and axes parallel to the surface of the substrate 50 are defined as the X axis and the Z axis. Also, the X axis is parallel to the first side 51 of the substrate 50, and the Z axis is parallel to the second side 52 of the substrate 50. For the sake of convenience of explanation, the positive direction of the Y axis may be referred to as "up", and the negative direction of the Y axis may be referred to as "down". Note that these expressions regarding the directions are used for convenience of explanation and are not intended to limit the posture during actual use of the structure.

[0067] The antenna 21A is arranged in an I shape along the first side 51 at a position a predetermined distance away from the vertex P1 of the substrate 50 along the first side 51. The antenna 21B is arranged in an I shape along the second side 52 at a position a predetermined distance away from the vertex P1 of the substrate 50 along the second side 52.

[0068] The antennas 21A and 21B are patch antennas (or microstrip antennas). However, the antennas 21A and 21B may also be monopole antennas or inverted-F antennas. If the antennas 21A and 21B are monopole antennas, they are folded back at a predetermined position and connected to GND as shown in FIG.

[0069] Antenna 21A and antenna 21B are placed at a predetermined distance or more (for example, 30 mm or more) apart to obtain a spatial diversity effect. However, the distance between antenna 21A and antenna 21B may be less than 30 mm.

[0070] The changeover switch 23 is disposed at a position a predetermined distance away from the vertex P1 of the substrate 50 toward the center of the substrate 50.

[0071] Feed line 22A is arranged to electrically connect an end of antenna 21A and selector switch 23 in an L-shape. A portion of L-shaped feed line 22A extending from antenna 21A along first side 51 is referred to as feed line portion 81A, and a portion of L-shaped feed line 22A extending from selector switch 23 along second side 52 is referred to as feed line portion 82A.

[0072] Feed line 22B is arranged to electrically connect an end of antenna 21B and selector switch 23 in an L-shape. A portion of L-shaped feed line 22B extending from antenna 21B along second side 52 is referred to as feed line portion 81B, and a portion of L-shaped feed line 22B extending from selector switch 23 along first side 51 is referred to as feed line portion 82B.

[0073] The angle formed by a line that is a virtual extension of the longitudinal direction of antenna 21A and a line that is a virtual extension of the longitudinal direction of antenna 21B may be approximately 90 degrees. Also, the angle formed by a line that is a virtual extension of feeder line portion 81A and a line that is a virtual extension of feeder line portion 81B may be approximately 90 degrees.

[0074] A GND 62 for ensuring isolation between the power feed lines is disposed in a space surrounded by the vertex P1 of the substrate 50, the changeover switch 23, the power feed line 22A, and the power feed line 22B.

[0075] The control circuit 24 is disposed near the center of the substrate 50 and is electrically connected to the changeover switch 23 .

[0076] The IC GND 63A is arranged between the control circuit 24 and the antenna 21A. The IC GND 63B is arranged between the control circuit 24 and the feeder line portion 81B. The IC GND 63C is arranged next to the control circuit 24 on the positive side of the Z axis. Because the antennas 21A and 22B are patch antennas, they are less affected by the surrounding GNDs, which allows the components and GNDs to be arranged around the antennas 21A and 22B in this manner. Note that the number, size, and arrangement of the IC GNDs shown in FIG. 6 are merely an example and are not limited to these.

[0077] The other circuit 25 is disposed, for example, next to the control circuit 24 on the positive side of the X axis.

[0078] The connector 26 is disposed, for example, near a third side 53 opposite to the first side 51 of the substrate 50.

[0079] 7, the antennas 21A and 22B have a size of, for example, 13 mm on the long side and 4.5 mm on the short side, but the size of the antennas 21A and 22B is not limited to this.

[0080] As shown in FIG. 7, the first layer of the substrate 50 is hollowed out in areas where the antennas 21A and 22B are to be disposed.

[0081] When the components and GND are arranged on the board 50 as shown in Figures 6 and 7, the components and GND can be arranged on the board 50 having a first side 51 of 75 mm and a second side 52 of 45 mm, for example, as shown in Figures 6 and 7. That is, according to the arrangement of the components and GND shown in Figures 6 and 7, the board 50 and ECU 20 can be made smaller than the arrangement of the components and GND shown in Figure 4 in the first embodiment.

[0082] FIG. 8 is a plan view showing a configuration example of the second layer (L2 layer) of the substrate 50 of the ECU 20 according to the second embodiment.

[0083] As shown in FIG. 8, the second layer of the substrate 50 has holes cut out at the portions where the antennas 21A and 21B are to be disposed.

[0084] Furthermore, on the second layer of the substrate 50, power supply lines and communication lines 90 are arranged in an area where the control circuit 24 and other circuits 25, 27 (see FIG. 10) on the other layers are arranged. Power is supplied to and data is transmitted and received from the control circuit 24 and other circuits 25, 27 on the other layers through the power supply lines and communication lines 90 on the second layer.

[0085] On the second layer of the substrate 50, a GND 65A for the IC is arranged next to the negative side of the X-axis of the power supply line and communication line 90. On the second layer of the substrate 50, a GND 65B is arranged in the space between the antenna 21A and the antenna 21B.

[0086] FIG. 9 is a plan view showing a configuration example of the third layer (L3 layer) of the substrate 50 of the ECU 20 according to the second embodiment.

[0087] 9, the third layer of the substrate 50 has a hole cut out in the area where the antennas 21A and 21B are to be disposed. The third layer of the substrate 50 has a GND hole 72 formed therein.

[0088] FIG. 10 is a plan view showing a configuration example of the fourth layer (L4 layer) of the substrate 50 of the ECU 20 according to the second embodiment.

[0089] On the fourth layer of the substrate 50, other circuits 27 are arranged in approximately the same area as other circuits 25 on the first layer.

[0090] As shown in FIG. 10, the fourth layer of the substrate 50 has holes cut out at the portions where the antennas 21A and 22B are to be disposed.

[0091] The antennas 21A and 21B are patch antennas having a predetermined height (thickness), and are disposed in the hollowed-out portions of the fourth, third, second, and first layers of the substrate 50.

[0092] GND 66A is arranged adjacent to antenna 21A on the positive side of the Z axis, and antenna 21A is connected to GND 66A.

[0093] A GND 66B is placed in the space between antenna 21A and antenna 21B. A GND 66C for IC and a GND 66D for IC are placed next to antenna 21B on the positive side of the X axis.

[0094] The arrangement of the antennas 21A, 21B, the power feeders 22A, 22B, etc. shown in FIGS. 8 to 10 may be applied to the circuit board of the electronic key 10.

[0095] <Antenna directivity graph> FIG. 11 is a graph showing an example of the antenna directivity of the antenna 21A and the antenna 21B according to the second embodiment.

[0096] Graph 110A in Fig. 11 shows the 360-degree antenna directivity on the XY plane of antenna 21A. In graph 110A, solid line 111A shows the gain of horizontally polarized waves, and dotted line 112A shows the gain of vertically polarized waves.

[0097] Graph 110B in Fig. 11 shows the 360-degree antenna directivity on the XY plane of antenna 21B. In graph 110B, solid line 111B shows the gain of horizontally polarized waves, and dotted line 112B shows the gain of vertically polarized waves.

[0098] When the antennas 21A, 21B and the power feeders 22A, 22B are arranged as shown in FIGS. 6 to 10, radio waves can be transmitted and received in approximately 360-degree directions, as shown in graphs 110A and 110B. In other words, there are no angles or frequency bands where distance cannot be measured accurately. Therefore, regardless of the direction in which the electronic key 10 is positioned relative to the vehicle 2, the ECU 20 can accurately measure the distance to the electronic key 10. Furthermore, the graphs 110A and 110B shown in FIG. 11 do not exhibit degradation in wireless communication characteristics when compared to the graphs 100A and 100B shown in FIG. 5 of the first embodiment.

[0099] Therefore, according to the configuration shown in Figures 6 to 10 of embodiment 2, the size of the substrate 50 (the size of the ECU 20) can be reduced without degrading the wireless communication characteristics, compared to the configuration shown in Figure 4 of embodiment 1.

[0100] Summary of the Disclosure The above description of the second embodiment discloses the following techniques.

[0101] <Technology 1> A wireless communication device (e.g., ECU 20) mounted on a vehicle (2) and capable of wireless communication with an electronic key (10) of the vehicle includes a substrate (50) that is rectangular in plan view, a first antenna (21A) that is arranged at a position a predetermined distance from one vertex (P1) of the substrate along a first side (51) of the substrate and extends along the first side, a second antenna (21B) that is arranged at a position a predetermined distance from the vertex of the substrate along a second side (52) different from the first side of the substrate and extends along the second side, and a first GND (62) that is arranged near the vertex of the substrate. This makes it possible to reduce the size of the board while suppressing interference between the first antenna and the second antenna.

[0102] <Technology 2> The wireless communication device described in Technology 1 further includes a first feeder line (22A) including a first feeder line portion (81A) extending from the first antenna (21A) along the first side (51) toward the vertex (P1), a second feeder line (22B) including a second feeder line portion (81B) extending from the second antenna (21B) along the second side (52) toward the vertex, and a changeover switch (23) to which the first feeder line and the second feeder line are connected, and the first GND (62) is arranged in a region surrounded by the changeover switch, the first feeder line, the second feeder line, and the vertex. This makes it possible to reduce the size of the board while suppressing interference between the first antenna and the first feed line and the second antenna and the second feed line.

[0103] <Technology 3> In the wireless communication device according to Technique 2, the angle formed by the imaginary extension of the first feeder line portion and the imaginary extension of the second feeder line portion is 90 degrees. This makes it possible to suppress interference between the first and second power feed lines.

[0104] <Technology 4> In the wireless communication device according to any one of techniques 1 to 3, the first antenna and the second antenna are patch antennas. This allows the antenna to be made smaller, and therefore the substrate to be made smaller.

[0105] <Technology 5> The wireless communication device according to any one of techniques 1 to 4 further includes a control circuit (24) to which the changeover switch is connected, and the control circuit controls the changeover switch to switch between using the first antenna and the second antenna. This allows the control circuit to switch between using the first antenna and the second antenna to perform wireless communication with the electronic key, and to detect a path with high communication quality.

[0106] <Technology 6> The wireless communication device described in Technology 5 further includes a second GND (63A) arranged between the control circuit and the first antenna on the substrate, and a third GND (63B) arranged between the control circuit and the second antenna on the substrate. Because the first and second antennas are patch antennas, they are less affected by the surrounding GND, which allows the second GND to be placed near the first antenna and the third GND to be placed near the second antenna, resulting in a smaller board.

[0107] <Technology 7> In the wireless communication device according to any one of techniques 1 to 6, the first antenna and the second antenna are spaced apart by a predetermined distance or more. This makes it possible to obtain a spatial diversity effect, and to prevent the occurrence of frequencies or angles that degrade wireless communication with the electronic key.

[0108] Although the embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications, alterations, substitutions, additions, deletions, and equivalents within the scope of the claims, and it is understood that these also fall within the technical scope of the present disclosure. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention. [Industrial Applicability]

[0109] The technology of the present disclosure is useful for wireless communication devices mounted on vehicles. [Explanation of symbols]

[0110] 1 user 2 vehicles 10 Electronic Key 11A, 11B antenna 12A,12B feeder line 13. Selector switch 14 Control circuit 15 Operation buttons 20 ECU 21A, 21B Antenna 22A,22B feeder line 23 Selector switch 25 Other circuits 26 Connectors 27 Other circuits 31 Knob Switch 32 indicators 33 Turn signal 41, 42, 43, 44 Pass 50 boards 51 Side 1 52 Side 2 53 Third Side 61A,61B,61C,62,62C,63A,63B,63C,65A,65B,66A,66B,66C,66D GND 81A, 81B, 82A, 82B feeder line part 90 Power lines and communication lines 100A, 100B, 110A, 110B graph P1, P2 vertices

Claims

1. A wireless communication device that is mounted in a vehicle and can communicate wirelessly with an electronic key of the vehicle, A substrate that is rectangular in plan view; a first antenna disposed at a position along a first side of the substrate at a predetermined distance from one vertex of the substrate and extending along the first side; a second antenna disposed at a position a predetermined distance from the vertex of the substrate along a second side different from the first side of the substrate and extending along the second side; a first GND disposed near the apex of the substrate; Wireless communication device.

2. 2. The wireless communication device according to claim 1, a first feed line including a first feed line portion extending from the first antenna along the first side toward the vertex; a second feed line including a second feed line portion extending from the second antenna along the second side toward the vertex; a changeover switch to which the first power supply line and the second power supply line are connected, the first GND is disposed in a region surrounded by the changeover switch, the first power supply line, the second power supply line, and the vertex; Wireless communication device.

3. 3. The wireless communication device according to claim 2, an angle formed by a line that is a virtual extension of the first power supply line portion and a line that is a virtual extension of the second power supply line portion is 90 degrees; Wireless communication device.

4. 3. The wireless communication device according to claim 2, the first antenna and the second antenna are patch antennas. Wireless communication device.

5. 5. The wireless communication device according to claim 4, Further, a control circuit connected to the changeover switch is provided. the control circuit controls the changeover switch to switch between using the first antenna and the second antenna; Wireless communication device.

6. 6. The wireless communication device according to claim 5, a second GND disposed between the control circuit and the first antenna on the substrate; a third GND disposed between the control circuit and the second antenna on the substrate; Wireless communication device.

7. 7. The wireless communication device according to claim 1, The first antenna and the second antenna are spaced apart by a predetermined distance or more. Wireless communication device.

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