Kick sensor

Abstract

To provide a kick sensor capable of preventing erroneous detection.SOLUTION: A kick sensor 1, which is designed to detect a movement of a human leg serving as a trigger of controlling a vehicle door when installed in a vehicle, includes a first antenna 10 that receives radio waves from at least the side of the vehicle door, and a second antenna 20 that receives radio waves from at least the bottom of the vehicle door.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a kick sensor that is provided in a vehicle and detects the movement of a person's leg, which serves as a trigger for controlling the door of the vehicle. [Background technology]

[0002] Conventionally, door opening and closing devices have been used that have the function of automatically locking and unlocking vehicle doors and opening and closing doors. For example, one such door opening and closing device is described in Patent Document 1, the source of which is shown below.

[0003] The door opening and closing device described in Patent Document 1 includes a non-contact detection unit that detects the presence of a user positioned near a vehicle door, changes the vehicle door from a locked state to an unlocked state, and then opens the door. This detection unit includes a detection sensor that is attached near the door and detects an object positioned below the door. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-116824 Summary of the Invention [Problem to be solved by the invention]

[0005] The door opening and closing device described in Patent Document 1 is configured such that the detection sensor detects an object located below the door. Therefore, even if the detection sensor detects, for example, a cat or a person (person's leg) who has no intention of opening the door within its detection range, the door may be mistakenly opened.

[0006] Therefore, there is a need for a kick sensor that can prevent false detection. [Means for solving the problem]

[0007] The characteristic configuration of the kick sensor of the present invention is that it is installed in a vehicle and detects the movement of a person's leg, which triggers the control of the vehicle door, and is equipped with a first antenna that receives radio waves from at least the side of the vehicle door, and a second antenna that receives radio waves from at least the bottom of the vehicle door.

[0008] With this characteristic configuration, the vehicle door state can be switched from one of an open state and a closed state to the other, or the door lock can be switched from one of a locked state and an unlocked state to the other, based on the reception of radio waves from the side by the first antenna and from below by the second antenna. Therefore, compared to a configuration in which the vehicle door state is switched from one of an open state and a closed state to the other, or the door lock can be switched from one of a locked state and an unlocked state to the other, based on the reception of radio waves from only one of the side and below, false detection can be prevented, for example, when an animal passes near the kick sensor or when a person passes or moves without intending to switch the state of the vehicle door or door lock. In this way, the kick sensor can detect the movement (motion) of a person's leg and appropriately switch the state of the vehicle door or door lock. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a vehicle equipped with a kick sensor. [Figure 2] FIG. 2 is a plan view of the kick sensor. [Figure 3] FIG. 4 is a diagram illustrating the directivity characteristics of a first antenna. [Figure 4] FIG. 4 is a diagram illustrating the directional characteristics of a second antenna. [Figure 5] 10A and 10B are diagrams illustrating input forms of opening and closing commands using a person's legs. [Figure 6] FIG. 10 is a plan view of a kick sensor according to another embodiment. [Figure 7]FIG. 10 is a plan view of a kick sensor according to another embodiment. [Figure 8] FIG. 10 is a plan view of a kick sensor according to another embodiment. [Figure 9] FIG. 2 is a diagram illustrating switching between a first state and a second state. DETAILED DESCRIPTION OF THE INVENTION

[0010] The kick sensor according to the present invention is capable of detecting an operation command for switching the state of a vehicle door or door lock. The kick sensor 1 according to this embodiment will be described below. However, the kick sensor 1 is not limited to the following embodiment, and various modifications are possible within the scope of the gist thereof.

[0011] As shown in FIG. 1, a kick sensor 1 is provided on a vehicle 2. As described above, the kick sensor 1 detects an operation command for switching the state of the door 3 and door lock of the vehicle 2. The door 3 of the vehicle 2 corresponds to a door 3 provided on the vehicle 2 that can be opened and closed by an actuator. Specifically, for example, this corresponds to a back door 3A (rear gate) provided at the rear of the vehicle 2, or a sliding door 3B provided on the side of the vehicle 2. The door lock corresponds to a mechanism provided on these doors 3 that can be switched between a locked state in which the door 3 does not open and an unlocked state in which the door 3 can be opened. In the following, the back door 3A will be described as an example of the door 3 of the vehicle 2.

[0012] Switching the state of the doors 3 and door locks of the vehicle 2 means controlling the doors 3 of the vehicle 2. Specifically, this means both switching the doors 3 of the vehicle 2 that are in an open state to a closed state, and switching the doors 3 of the vehicle 2 that are in a closed state to an open state. Furthermore, this means both switching the doors from a locked state to an unlocked state, and switching the doors from an unlocked state to a locked state. An operation command corresponds to a command input by the person 4 that triggers control to switch the states of the doors 3 and door locks of the vehicle 2. Such a command is input by the movement of the legs 4A of the person 4.

[0013] Therefore, the kick sensor 1 is configured to detect a command input by the movement of the leg 4A of the person 4, which triggers switching the back door 3A of the vehicle 2 in an open state to a closed state, and a command input by the movement of the leg 4A of the person 4, which triggers switching the back door 3A of the vehicle 2 in a closed state to an open state.The kick sensor 1 is also configured to detect a command input by the movement of the leg 4A of the person 4, which triggers switching the door lock from a locked state to an unlocked state, and a command input by the movement of the leg 4A of the person 4, which triggers switching the door lock from an unlocked state to a locked state.

[0014] FIG. 2 shows a plan view of the kick sensor 1. As shown in FIGS. 1 and 2, the kick sensor 1 includes a first antenna 10, a second antenna 20, and a control unit 30. The first antenna 10 receives radio waves from at least the sides of the door 3 of the vehicle 2. The sides of the door 3 of the vehicle 2 refer to directions along a horizontal direction centered on the door 3 of the vehicle 2, and include not only both sides (left and right sides) in the vehicle width direction of the vehicle 2 but also the rear of the vehicle 2. In this embodiment, the sides of the door 3 of the vehicle 2 are described as being rear of the back door 3A of the vehicle 2. Therefore, the first antenna 10 of this embodiment receives radio waves propagating through the air from behind the back door 3A of the vehicle 2 as radio waves from the sides of the door 3 of the vehicle 2.

[0015] In this embodiment, the first antenna 10 is configured as a patch antenna (microstrip antenna). The first antenna 10 is configured as a pattern formed on a substrate 5. The substrate 5 is configured as a multilayer printed circuit board (a printed circuit board including four conductor layers in this embodiment). If the four conductor layers are a first conductor layer, a second conductor layer, a third conductor layer, and a fourth conductor layer, the substrate 5 is configured by stacking the conductor layers in the order of the first conductor layer, the second conductor layer, the third conductor layer, and the fourth conductor layer from the bottom up, with an insulating layer provided between any two stacked conductor layers. The first antenna 10 has a first antenna element 10A and a second antenna element 10B provided on different conductor layers. The first antenna element 10A is formed on the fourth conductor layer, and the second antenna element 10B is formed on the third conductor layer. The first antenna element 10A and the second antenna element 10B are each formed in a rectangular shape in a plan view, and in a plan view, the size (area) of the first antenna element 10A is configured to be larger than the size (area) of the second antenna element 10B. Note that, although the second antenna element 10B is shown by a dashed line in Fig. 2, this is for ease of understanding, and it cannot actually be seen when the substrate 5 is viewed from the surface 5A side.

[0016] The first antenna element 10A and the second antenna element 10B can transmit and receive radio waves at different frequencies. The first antenna element 10A and the second antenna element 10B are each electrically connected to the first conductor layer via a through-hole TH, and a capacitor can be mounted across the land extending from the through-hole TH and the ground pattern on the surface opposite to the surface 5A of the substrate 5. The impedance can be adjusted by changing the capacitance value of this capacitor.

[0017] The conductor pattern of the first conductor layer and the conductor pattern of the second conductor layer have portions that face each other in the stacking direction, sandwiching an insulating layer provided between the first and second conductor layers. As a result, in addition to the capacitor described above, a capacitance is formed by the conductor pattern of the first conductor layer, the conductor pattern of the second conductor layer, and the insulating layer. This capacitance also makes it possible to adjust the impedance.

[0018] The third conductor layer includes a third-layer pattern-forming region where the second antenna element 10B is formed and a ground region surrounding the third-layer pattern-forming region. The first-layer pattern-forming region where the conductor pattern of the first conductor layer is formed includes an overlapping region that overlaps with the second antenna element 10B in a planar view, and at least a portion of this overlapping region has a cutout region where the first-layer pattern is not formed. This suppresses the confinement of electric field lines between the first antenna element 10A and the second antenna element 10B, enabling efficient radiation and incidence of radio waves. The overlapping region corresponds to the region directly below the second antenna element 10B.

[0019] The second antenna 20 receives radio waves from at least below the door 3 of the vehicle 2. Below the door 3 of the vehicle 2 means the side of the road surface 200 (see FIG. 5) of the road on which the vehicle 2 is parked. Therefore, the second antenna 20 receives radio waves propagating through the air from the side of the road surface 200 of the road on which the vehicle 2 is parked.

[0020] In this embodiment, the second antenna 20 is configured as a Vivaldi antenna. The second antenna 20 is also configured as a pattern formed on the substrate 5. In this embodiment, the first antenna 10 and the second antenna 20 are configured on a single substrate 5. The second antenna 20 has a first antenna element 21 provided for antenna matching (impedance matching) and a second antenna element 22 for receiving radio waves. In FIG. 2, the first antenna element 21 is configured as a square in a plan view, but it may also be circular or rectangular. Of course, it may also be triangular or n-sided (n is an integer greater than or equal to 5). The second antenna element 22 is formed to extend from the first antenna element 21 toward the opposite end of the substrate 5 from the end on which the first antenna element 21 is provided. The second antenna element 22 is configured so that its width in a direction perpendicular to the direction of extension toward the opposite end gradually increases with increasing distance from the first antenna element 21. In this embodiment, the width is configured to increase exponentially. The first antenna element 21 and the second antenna element 22 are formed on a first conductor layer, and the second, third, and fourth conductor layers that overlap the first conductor layer are removed.

[0021] 1, the substrate 5 is provided on the rear end side of the vehicle 2 with a surface 5A of the substrate 5 on which the first antenna 10 and the second antenna 20 are formed facing rearward in the traveling direction of the vehicle 2. Specifically, the substrate 5 is provided on the rear bumper 1B of the vehicle 2 in an upright state with the surface 5A of the substrate 5 on which the first antenna 10 and the second antenna 20 are formed facing rearward of the vehicle 2. If the rear bumper 1B is made of a resin material, the substrate 5 may be provided inside the rear bumper 1B. Of course, the substrate 5 may be provided in a state exposed from the rear bumper 1B.

[0022] Fig. 3 shows the directional characteristics of the first antenna 10. The first antenna 10 has a circular directional characteristic as shown in Fig. 3. The first antenna 10 also has a circular directional characteristic when the substrate 5 is viewed from a direction parallel to the surface 5A (not shown). Therefore, the first antenna 10 has directionality with respect to radio waves from the side (in this embodiment, the rear of the vehicle 2).

[0023] The first antenna 10 is also capable of transmitting radio waves to the rear of the vehicle 2, and is configured to be able to transmit and receive vertically polarized radio waves and horizontally polarized radio waves. This allows the first antenna 10 to not only detect the legs 4A of the person 4, but also to be used for communication with, for example, a mobile terminal associated with the vehicle 2 and having an electronic key stored therein.

[0024] FIG. 4 shows the directional characteristics of the second antenna 20. The second antenna 20 has the second antenna element 22 as described above. As shown in FIG. 4, the second antenna 20 has a strong directivity in the direction in which the second antenna element 22 extends (a direction along 270 degrees in FIG. 4) and a weak directivity in the direction opposite to the direction in which the second antenna element 22 extends (a range from 0 degrees to 180 degrees in FIG. 4). The second antenna 20 also has a significantly weak directional characteristic in a direction perpendicular to the surface 5A of the substrate 5 on which the second antenna 20 is provided (not shown). Therefore, the second antenna 20 has directivity with respect to radio waves from below (the road surface 200 side in this embodiment), and is configured to transmit radio waves toward the road surface 200 side and to transmit and receive polarized radio waves that oscillate parallel to the surface 5A.

[0025] FIG. 5 is a diagram showing input forms of open / close commands based on the movement of the leg 4A of the person 4. As described above, the kick sensor 1 is provided near the rear end of the vehicle 2. The first antenna 10 receives radio waves from the rear of the vehicle 2. In the example of FIG. 5, radio waves are received from the shin of the leg 4A of the person 4. Meanwhile, the second antenna 20 receives radio waves from the road surface 200. In the example of FIG. 5, radio waves are received from the toe of the leg 4A of the person 4. In this manner, the kick sensor 1 detects an open / close command as a trigger for switching the state of the door 3 of the vehicle 2 at both the first antenna 10 and the second antenna 20. The detection results of the first antenna 10 and the second antenna 20 are transmitted to the control unit 30. When both the first antenna 10 and the second antenna 20 receive radio waves within a predetermined time, the control unit 30 switches the state of the door 3 of the vehicle 2 from one of an open state and a closed state to the other, or switches the door lock from one of an unlocked state and a locked state to the other.

[0026] In this way, according to the kick sensor 1, the state of the door 3 and the door lock are changed when both the first antenna 10 and the second antenna 20 detect radio waves, so changes in the state of the door 3 and the door lock due to erroneous detection can be reduced compared to a configuration in which the state of the door 3 and the door lock are switched when one of the first antenna 10 and the second antenna 20 detects radio waves.

[0027] In the kick sensor 1, the first antenna 10 and the second antenna 20 each emit radio waves at predetermined time intervals and are then able to receive radio waves that are reflected from the emitted radio waves. The control unit 30 switches each of the first antenna 10 and the second antenna 20 between a radio wave emission state and a radio wave reception state. That is, the first antenna 10 emits radio waves toward the rear of the vehicle 2 at predetermined time intervals and is in a reception state where it can receive radio waves from the time of the first radio wave emission until the time of the next radio wave emission. The second antenna 20 emits radio waves toward the road surface 200 at predetermined time intervals and is in a reception state where it can receive radio waves from the time of the first radio wave emission until the time of the next radio wave emission.

[0028] With the above configuration, the kick sensor 1 can detect the action (movement) of the person 4's leg 4A related to the opening / closing command given by the person 4 via the leg 4A, even if the person 4 using the vehicle 2 is carrying luggage with both hands, as shown in Figure 1, and can appropriately switch the state of the door 3 and door lock of the vehicle 2.

[0029] Other Embodiments Next, other embodiments of the kick sensor 1 will be described.

[0030] In the above embodiment, the second antenna 20 has been described as having a first antenna element 21 and a second antenna element 22, and the second antenna element 22 is configured to expand exponentially with increasing distance from the first antenna element 21. However, the second antenna element 22 of the second antenna 20 may be configured to expand linearly with increasing distance from the first antenna element 21, as shown in Fig. 6 .

[0031] In the above embodiment, the first antenna 10 has been described as a patch antenna. However, the first antenna 10 may be configured using a Vivaldi antenna as shown in Fig. 7. Alternatively, the first antenna 10 may be an antenna in which an element portion protrudes from a ground pattern as shown in Fig. 8.

[0032] In the above embodiment, it has been described that the first antenna 10 and the second antenna 20 each emit radio waves at predetermined time intervals and then enter a state in which they can receive radio waves that are reflected from the emitted radio waves. For example, the control unit 30 may be configured to alternately switch the states of the first antenna 10 and the second antenna 20 between a first state in which one of the first antenna 10 and the second antenna 20 transmits radio waves and a second state in which the other of the first antenna 10 and the second antenna 20 transmits radio waves.

[0033] 9, in the first state, the first antenna 10 transmits radio waves toward the side and downward of the vehicle 2 (#11), and the first antenna 10 receives radio waves from the shins of the legs 4A of the person 4 in response to the transmitted radio waves (#12), and the second antenna 20 receives radio waves from the toes of the legs 4A in response to the transmitted radio waves (#13). Meanwhile, in the second state, the second antenna 20 transmits radio waves toward the downward direction of the vehicle 2 (#21), and the first antenna 10 and the second antenna 20 receive radio waves from the toes of the legs 4A of the person 4 in response to the transmitted radio waves (#22). In this case, the second antenna 20 does not transmit radio waves toward the side of the vehicle 2, making it difficult to receive radio waves from the side of the vehicle 2.

[0034] In the first state, the control unit 30 may, for example, cause the first antenna 10 to transmit radio waves at predetermined time intervals, and place both the first antenna 10 and the second antenna 20 in a receiving state during the period from when the radio waves are transmitted until the next radio wave transmission. In the second state, the control unit 30 may cause the second antenna 20 to transmit radio waves at predetermined time intervals, and place both the first antenna 10 and the second antenna 20 in a receiving state during the period from when the radio waves are transmitted until the next radio wave transmission. In this configuration, the number of times radio waves are transmitted can be reduced compared to when radio waves are transmitted and received by each of the first antenna 10 and the second antenna 20, thereby enabling power consumption to be reduced.

[0035] In this case, the control unit 30 may be configured to determine whether or not a movement of the leg 4A of the person 4 has occurred based on the ratio between the strength of the radio waves received by the first antenna 10 and the strength of the radio waves received by the second antenna 20. For example, if the ratio between the strength of the radio waves received by the first antenna 10 and the strength of the radio waves received by the second antenna 20 is within a range including a predetermined value, and both the strength of the radio waves received by the first antenna 10 and the second antenna 20 are stronger than the predetermined value, it can be determined that the movement of the leg 4A of the person 4 is to the side or below the door 3 and has the intention of switching the state of the door 3 or door lock of the vehicle 2. This makes it possible to prevent erroneous detection.

[0036] [Summary of the above embodiment] The kick sensor 1 described above will now be outlined.

[0037] (1) The kick sensor 1 is provided in a vehicle 2 and detects the movement of a person 4's leg 4A, which triggers the control of the door 3 of the vehicle 2. The kick sensor 1 is equipped with a first antenna 10 that receives radio waves from at least the side of the door 3 of the vehicle 2, and a second antenna 20 that receives radio waves from at least the bottom of the door 3 of the vehicle 2.

[0038] According to this configuration, the state of the door 3 of the vehicle 2 can be switched from one of an open state and a closed state to the other, or the door lock can be switched from one of a locked state and an unlocked state to the other, based on the reception of radio waves from the side by the first antenna 10 and from below by the second antenna 20. Therefore, compared to a case where the state of the door 3 of the vehicle 2 is switched from one of an open state and a closed state to the other, or the door lock is switched from one of a locked state and an unlocked state to the other, based on only the reception of radio waves from the side or from below, erroneous detection can be prevented, for example, when an animal passes near the kick sensor 1 or when a person passes or moves without intending to switch the state of the door 3 or the door lock of the vehicle 2. In this way, the kick sensor 1 can detect the movement (motion) of the leg 4A of the person 4 and appropriately switch the state of the door 3 or the door lock of the vehicle 2.

[0039] (2) In the kick sensor 1 described in (1), it is preferable that the first antenna 10 has directionality with respect to radio waves coming from the side.

[0040] According to this configuration, radio waves can be properly received from the side by the first antenna 10. Therefore, the kick sensor 1 can properly detect the shin of the leg 4A of the person 4.

[0041] (3) In the kick sensor 1 described in (1) or (2), it is preferable that the second antenna 20 has directivity for radio waves from below.

[0042] According to this configuration, radio waves from below can be properly received by the second antenna 20. Therefore, the kick sensor 1 can properly detect the toe of the leg 4A of the person 4.

[0043] (4) In the kick sensor 1 described in (1) to (3), it is preferable that the first antenna 10 and the second antenna 20 are configured as patterns formed on a single substrate 5.

[0044] According to this configuration, when the substrate 5 is configured by, for example, a printed circuit board, the kick sensor 1 can be configured inexpensively by forming the first antenna 10 and the second antenna 20 on a single printed circuit board.

[0045] In the kick sensor 1 described in (5)(4), it is preferable that the substrate 5 is provided on the rear end side of the vehicle 2 with the surface 5A of the substrate 5 on which the first antenna 10 and the second antenna 20 are formed facing rearward in the direction of travel of the vehicle 2.

[0046] According to this configuration, the kick sensor 1 can be used to control the opening and closing of the back door 3A (rear gate) of the vehicle 2. Therefore, the first antenna 10 can detect the shin of the leg 4A that is extended from the rear side of the vehicle 2 toward the kick sensor 1, and the second antenna 20 can detect the toe of the leg 4A that is extended downward from the rear side of the vehicle 2.

[0047] (6) In the kick sensor 1 described in (1) to (5), it is preferable that the first antenna 10 is capable of transmitting and receiving vertically polarized radio waves and horizontally polarized radio waves.

[0048] For example, when a mobile terminal is used to lock or unlock the lock mechanism of the vehicle 2 with an electronic key, the radio waves from the mobile terminal are often horizontally polarized radio waves. Therefore, by configuring the first antenna 10 to be able to transmit and receive vertically polarized radio waves and horizontally polarized radio waves, it becomes possible to use the first antenna 10 not only for communication with the leg 4A of the person 4 who switches the state of the door 3 of the vehicle 2 from one of the open state and the closed state to the other, but also for communication with the mobile terminal.

[0049] (7) In the kick sensor 1 described in (1) to (6), it is preferable that the first antenna 10 can transmit radio waves laterally, and the second antenna 20 can transmit radio waves downward.

[0050] According to this configuration, the first antenna 10 and the second antenna 20 can also be used to transmit radio waves for detecting the person 4. Therefore, it is possible to configure a low-cost and compact transmitting and receiving antenna.

[0051] (8) In the kick sensor 1 described in (1) to (7), it is preferable to further include a control unit 30 that alternately switches the states of the first antenna 10 and the second antenna 20 between a first state in which one of the first antenna 10 and the second antenna 20 transmits radio waves and a second state in which the other of the first antenna 10 and the second antenna 20 transmits radio waves.

[0052] According to this configuration, in the first state, for example, the first antenna 10 transmits radio waves at predetermined time intervals, and both the first antenna 10 and the second antenna 20 can be in a receiving state from the time the radio waves are transmitted until the next time the radio waves are transmitted. Also, in the second state, the second antenna 20 transmits radio waves at predetermined time intervals, and both the first antenna 10 and the second antenna 20 can be in a receiving state from the time the radio waves are transmitted until the next time the radio waves are transmitted. With this configuration, the number of times radio waves are transmitted can be reduced compared to when radio waves are transmitted and received by each of the first antenna 10 and the second antenna 20, and therefore power consumption can be reduced.

[0053] In the kick sensor 1 described in (9)(8), it is preferable to determine whether or not a movement has been made in the leg 4A of the person 4 based on the ratio between the strength of the radio waves received by the first antenna 10 and the strength of the radio waves received by the second antenna 20.

[0054] According to this configuration, for example, if the ratio of the strength of the radio waves received by the first antenna 10 to the strength of the radio waves received by the second antenna 20 (strength of the radio waves received by the first antenna 10 / strength of the radio waves received by the second antenna 20) is greater than a predetermined value, it can be determined that there has been movement on the side of the door 3, and if the ratio of the strength of the radio waves received by the first antenna 10 to the strength of the radio waves received by the second antenna 20 (strength of the radio waves received by the first antenna 10 / strength of the radio waves received by the second antenna 20) is equal to or less than a predetermined value, it can be determined that there has been movement below the door 3. On the other hand, if the ratio of the strength of the radio waves received by the first antenna 10 to the strength of the radio waves received by the second antenna 20 (strength of the radio waves received by the first antenna 10 / strength of the radio waves received by the second antenna 20) is within a range including a predetermined value, and both the strength of the radio waves received by the first antenna 10 and the strength of the radio waves received by the second antenna 20 are stronger than the predetermined value, it can be determined that this is the movement of the leg 4A of a person 4 to the side or below the door 3 who intends to change the state of the door 3 or door lock of the vehicle 2. Therefore, erroneous detection can be prevented. [Industrial Applicability]

[0055] The technology disclosed herein can be used in a kick sensor that is provided in a vehicle and detects the movement of a person's leg, which triggers the control of the vehicle door. [Explanation of symbols]

[0056] 1: kick sensor, 2: vehicle, 3: door, 4: person, 4A: leg, 5: circuit board, 5A: surface, 10: first antenna, 20: second antenna, 30: control unit

Claims

1. A kick sensor provided in a vehicle for detecting a leg movement of a person that triggers a door control of the vehicle, a first antenna for receiving radio waves from at least a side of a door of the vehicle; a second antenna for receiving radio waves from at least a lower part of the door of the vehicle; A kick sensor comprising:

2. The kick sensor according to claim 1 , wherein the first antenna has directionality with respect to the radio waves from the side.

3. The kick sensor according to claim 1 or 2, wherein the second antenna has directivity with respect to the radio wave from below.

4. 3. The kick sensor according to claim 1, wherein the first antenna and the second antenna are configured as patterns formed on a single substrate.

5. The kick sensor of claim 4, wherein the substrate is provided at the rear end of the vehicle with the surface of the substrate on which the first antenna and the second antenna are formed facing rearward in the direction of travel of the vehicle.

6. The kick sensor according to claim 1 or 2, wherein the first antenna is capable of transmitting and receiving vertically polarized radio waves and horizontally polarized radio waves.

7. the first antenna is capable of transmitting radio waves to the side, The kick sensor according to claim 1 or 2, wherein the second antenna is capable of transmitting radio waves downward.

8. 3. The kick sensor of claim 1, further comprising a control unit that alternately switches the states of the first antenna and the second antenna between a first state in which one of the first antenna and the second antenna transmits the radio waves and a second state in which the other of the first antenna and the second antenna transmits the radio waves.

9. 3. The kick sensor according to claim 1, wherein the sensor determines whether the person's leg has moved based on the ratio between the strength of the radio waves received by the first antenna and the strength of the radio waves received by the second antenna.

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