阅读说明：本技术 检测设备以及检测系统 (Detection device and detection system ) 是由 山本光一 藤浪一友 宫本博史 西崎良平 柳田曜 山田邦彦 于 2019-05-27 设计创作，主要内容包括：提供能够提升检测精度的检测设备以及检测系统。开关部(22)根据检测对象的状态而切换为将环形天线(21)的增益降低的增益降低状态或不将环形天线(21)的增益降低的增益非降低状态。开关部(22)在电波的波长为λ时,具有用于在从第1电路端子(23a)起沿环形天线(21)的第1延伸方向到离开λ/8的位置为止的环形天线(21)上的范围(K1)内降低环形天线(21)的增益的开关端子(22a、22b)。开关部(22)还具有用于在从第2电路端子(23b)起沿环形天线(21)的第2延伸方向到离开λ/8的位置为止的环形天线(21)上的范围(K2)内降低环形天线(21)的增益的开关端子(22d、22e)。(provided are a detection device and a detection system capable of improving detection accuracy. The switch unit (22) switches between a gain reduction state in which the gain of the loop antenna (21) is reduced and a gain non-reduction state in which the gain of the loop antenna (21) is not reduced, depending on the state of the object to be detected. The switch unit (22) has switch terminals (22a, 22b) for reducing the gain of the loop antenna (21) in a range (K1) over the loop antenna (21) from the 1 st circuit terminal (23a) in the 1 st extending direction of the loop antenna (21) to a position separated by λ/8 when the wavelength of the radio wave is λ. The switch unit (22) further has switch terminals (22d, 22e) for reducing the gain of the loop antenna (21) in a range (K2) on the loop antenna (21) from the 2 nd circuit terminal (23b) in the 2 nd extending direction of the loop antenna (21) to a position separated by λ/8.)

1. A detection device, characterized in that,

The disclosed device is provided with:

An antenna that transmits and receives an electric wave including a signal;

A signal output unit configured to include a 1 st circuit terminal and a 2 nd circuit terminal connected to the antenna, to start up using a signal for power supply included in a signal received by the antenna as power, and to output a detection signal to the antenna; and

A gain reduction unit that switches between a gain reduction state in which the gain of the antenna is reduced and a gain non-reduction state in which the gain of the antenna is not reduced, depending on a state of a detection target,

The gain reduction unit has a 1 st action point and a 2 nd action point, and when the wavelength of the radio wave is λ, the 1 st action point is configured to reduce the gain of the antenna in a range on the antenna from the 1 st circuit terminal to a position spaced from λ/8 in a 1 st extending direction of the antenna, and the 2 nd action point is configured to reduce the gain of the antenna in a range on the antenna from the 2 nd circuit terminal to a position spaced from λ/8 in a 2 nd extending direction of the antenna.

2. The detection apparatus of claim 1,

The 1 st operating point and the 2 nd operating point are operating points for bringing the signal output unit and the antenna into a conductive state or a non-conductive state.

3. The detection apparatus of claim 1 or 2,

The gain reduction unit is configured to include: a 1 st switch circuit capable of switching a 1 st terminal and a 2 nd terminal, which are the 1 st operating point, to a connected state or a non-connected state in which the terminals are electrically connected to each other; and a 2 nd switch circuit, the 2 nd switch circuit being capable of switching a 3 rd terminal and a 4 th terminal as the 2 nd action point to a connected state or a non-connected state in which they are electrically connected to each other,

The gain reduction unit is capable of switching between the gain non-reduction state in which the 1 st terminal and the 2 nd terminal are connected and the 3 rd terminal and the 4 th terminal are connected and the gain reduction state in which the 1 st terminal and the 2 nd terminal are disconnected and the 3 rd terminal and the 4 th terminal are disconnected.

4. The detection apparatus of claim 1 or 2,

The gain reduction unit is configured to include: a 1 st capacitor circuit capable of switching a 1 st plate and a 2 nd plate, which are the 1 st operating point, to a chargeable state or a non-chargeable state; and a 2 nd capacitor circuit, the 2 nd capacitor circuit being capable of switching the 3 rd plate and the 4 th plate as the 2 nd operating point to a chargeable state or a non-chargeable state,

The gain reduction unit can switch between the gain non-reduction state in which the 1 st plate and the 2 nd plate are in the electric storage enabled state and the 3 rd plate and the 4 th plate are in the electric storage enabled state, and the gain reduction state in which the 1 st plate and the 2 nd plate are in the electric storage disabled state and the 3 rd plate and the 4 th plate are in the electric storage disabled state.

5. The detection apparatus of claim 1,

The gain reduction unit is configured to include a 3 rd switching circuit, the 3 rd switching circuit being capable of switching the 1 st operating point and the 2 nd operating point to a connected state or a non-connected state in which the operating points are electrically connected to each other,

The 3 rd switch circuit is capable of switching between the gain non-reduction state and the gain reduction state, the gain non-reduction state setting the 1 st action point and the 2 nd action point to a non-connection state, and the gain reduction state setting the 1 st action point and the 2 nd action point to a connection state.

6. A detection system is characterized in that a detection device is provided,

The disclosed device is provided with:

A reading device that transmits and receives a radio wave including a signal and transmits a transmission signal including at least a signal for power supply;

a detection apparatus configured to include: an antenna that mutually transceives signals with the reading device; a signal output unit which has a 1 st circuit terminal and a 2 nd circuit terminal connected to the antenna, is activated by using, as power, a signal for circuit supply included in a signal received by the antenna, and outputs a detection signal to the antenna; and a gain reduction unit that switches between a gain reduction state in which the gain of the antenna is reduced and a gain non-reduction state in which the gain of the antenna is not reduced, depending on a state of a detection target; and

a determination unit connected to the reading device and configured to determine a state of the detection target based on the detection signal received by the reading device,

The gain reduction unit has a 1 st action point and a 2 nd action point, and when the wavelength of the radio wave is λ, the 1 st action point is configured to reduce the gain of the antenna in a range on the antenna from the 1 st circuit terminal to a position spaced from λ/8 in a 1 st extending direction of the antenna, and the 2 nd action point is configured to reduce the gain of the antenna in a range on the antenna from the 2 nd circuit terminal to a position spaced from λ/8 in a 2 nd extending direction of the antenna.

Technical Field

the invention relates to a detection device and a detection system.

Background

conventionally, as a detection device, for example, patent document 1 discloses a seatbelt-side device that detects the attachment and detachment of a vehicle seatbelt. The seatbelt-side device is configured to include: a detection switch that is provided at a buckle portion of the seat belt and is turned on when a tongue piece portion of the seat belt is attached to the buckle portion; and an RFID tag that transmits a mounting signal of the seat belt when the detection switch is turned on.

Disclosure of Invention

Technical problem to be solved by the invention

However, the seatbelt-side device described in patent document 1 may transmit a seatbelt attachment signal even when the tongue portion of the seatbelt is not attached to the buckle portion and the detection switch is off, for example, and may erroneously detect the seatbelt attachment signal.

Accordingly, the present invention has been made in view of the above problems, and an object thereof is to provide a detection apparatus and a detection system capable of improving detection accuracy.

Means for solving the problems

in order to solve the above problems and achieve the object, a detection device according to the present invention includes: an antenna that transmits and receives an electric wave including a signal; a signal output unit configured to include a 1 st circuit terminal and a 2 nd circuit terminal connected to the antenna, to start up using a signal for power supply included in a signal received by the antenna as power, and to output a detection signal to the antenna; and a gain reduction unit that switches between a gain reduction state in which the gain of the antenna is reduced and a gain non-reduction state in which the gain of the antenna is not reduced, depending on a state of a detection target, wherein the gain reduction unit has a 1 st operating point and a 2 nd operating point, and when the wavelength of the radio wave is λ, the 1 st operating point is used to reduce the gain of the antenna in a range on the antenna from the 1 st circuit terminal to a position separated by λ/8 in a 1 st extending direction of the antenna, and the 2 nd operating point is used to reduce the gain of the antenna in a range on the antenna from the 2 nd circuit terminal to a position separated by λ/8 in a 2 nd extending direction of the antenna.

In the above-described detection device, it is preferable that the 1 st operating point and the 2 nd operating point are operating points for bringing the signal output unit and the antenna into a conductive state or a non-conductive state.

In the above detection device, it is preferable that the gain reduction unit includes: a 1 st switch circuit capable of switching a 1 st terminal and a 2 nd terminal, which are the 1 st operating point, to a connected state or a non-connected state in which the terminals are electrically connected to each other; and a 2 nd switch circuit, the 2 nd switch circuit being capable of switching a 3 rd terminal and a 4 th terminal as the 2 nd operating point to a connected state or a disconnected state in which they are electrically connected to each other, the gain reduction unit being capable of switching the gain non-reduced state and the gain reduced state, the gain non-reduced state setting the 1 st terminal and the 2 nd terminal to a connected state and setting the 3 rd terminal and the 4 th terminal to a connected state, the gain reduced state setting the 1 st terminal and the 2 nd terminal to a disconnected state and setting the 3 rd terminal and the 4 th terminal to a disconnected state.

In the above detection device, it is preferable that the gain reduction unit includes: a 1 st capacitor circuit capable of switching a 1 st plate and a 2 nd plate, which are the 1 st operating point, to a chargeable state or a non-chargeable state; and a 2 nd capacitor circuit, the 2 nd capacitor circuit being capable of switching a 3 rd plate and a 4 th plate which are the 2 nd operating point to a chargeable state or an uncharged state, the gain reduction unit being capable of switching the gain non-reduction state in which the 1 st plate and the 2 nd plate are in an chargeable state and the 3 rd plate and the 4 th plate are in an chargeable state and the gain reduction state in which the 1 st plate and the 2 nd plate are in an uncharged state and the 3 rd plate and the 4 th plate are in an uncharged state.

In the above-described detection device, it is preferable that the gain reduction unit includes a 3 rd switching circuit, the 3 rd switching circuit is capable of switching the 1 st operating point and the 2 nd operating point to a connected state or an unconnected state in which they are electrically connected to each other, and the 3 rd switching circuit is capable of switching the gain non-reduced state in which the 1 st operating point and the 2 nd operating point are set to the unconnected state and the gain reduced state in which the 1 st operating point and the 2 nd operating point are set to the connected state.

The detection system according to the present invention is characterized by comprising: a reading device that transmits and receives a radio wave including a signal and transmits a transmission signal including at least a signal for power supply; a detection apparatus configured to include: an antenna that mutually transceives signals with the reading device; a signal output unit which has a 1 st circuit terminal and a 2 nd circuit terminal connected to the antenna, is activated by using, as power, a signal for circuit supply included in a signal received by the antenna, and outputs a detection signal to the antenna; and a gain reduction unit that switches between a gain reduction state in which the gain of the antenna is reduced and a gain non-reduction state in which the gain of the antenna is not reduced, depending on a state of a detection target; and a determination unit that is connected to the reader and determines a state of the detection target based on the detection signal received by the reader, wherein the gain reduction unit has a 1 st operating point and a 2 nd operating point, and when a wavelength of the radio wave is λ, the 1 st operating point is configured to reduce a gain of the antenna in a range on the antenna from the 1 st circuit terminal to a position spaced from λ/8 in a 1 st extending direction of the antenna, and the 2 nd operating point is configured to reduce the gain of the antenna in a range on the antenna from the 2 nd circuit terminal to a position spaced from λ/8 in a 2 nd extending direction of the antenna.

Effects of the invention

in the detection device and the detection system according to the present invention, the gain reduction unit has a 1 st operating point for reducing the gain of the antenna in a range from the 1 st circuit terminal of the signal output unit to a position separated by λ/8, and has a 2 nd operating point for reducing the gain of the antenna in a range from the 2 nd circuit terminal of the signal output unit to a position separated by λ/8. With this configuration, the detection device and the detection system can deactivate the antenna according to the state of the detection object, and can improve the detection accuracy.

Drawings

fig. 1 is a schematic diagram showing a configuration example of a detection system according to embodiment 1.

Fig. 2 is a block diagram showing an example of the configuration of the detection system according to embodiment 1.

Fig. 3 is a schematic diagram showing an example of installation of the detection system according to embodiment 1.

Fig. 4 is a schematic diagram showing an example of installation of the detection device according to embodiment 1.

Fig. 5 is a flowchart showing an operation example of the detection system according to embodiment 1.

fig. 6 is a schematic diagram showing an example of the configuration of a detection device according to modification 1 of embodiment 1.

Fig. 7 is a schematic diagram showing an example of the configuration of a detection device according to modification 2 of embodiment 1.

Fig. 8 is a schematic diagram showing an example of the configuration of a detection device according to modification 3 of embodiment 1.

Fig. 9 is a schematic diagram showing an example of the configuration of the detection device according to embodiment 2.

Fig. 10 is a schematic diagram showing an example of the configuration of a detection device according to a modification of embodiment 2.

Fig. 11 is a schematic diagram showing an example of the configuration of the detection device according to embodiment 3.

Fig. 12 is a schematic diagram showing an example of the configuration of a detection device according to a modification of embodiment 3.

description of the symbols

1 detection system

10 RFID reader (reading device)

20. 20A, 20B, 20C, 20D, 20E, 20F, 20G detection device

21 Loop antenna (aerial)

22 switch part (gain reducing part)

22R 1 st switch circuit

22L 2 nd switch circuit

22a, 22b switch terminals (1 st action point, 1 st terminal, 2 nd terminal)

22d, 22e switch terminals (2 nd action point, 3 rd terminal, 4 th terminal)

23 RFID detection circuit (Signal output part)

23a 1 st circuit terminal

23b 2 nd circuit terminal

24 capacitor part (gain reduction part)

24R 1 st capacitor circuit

24L 2 nd capacitor circuit

24a, 24b plates (1 st site, 1 st plate, 2 nd plate)

24c, 24d plates (2 nd site, 3 rd plate, 4 th plate)

25d 1 st connection point

25e 2 nd connection point

25 switching circuit (3 rd switching circuit, gain reduction part)

30 ECU (determination section)

40 dipole antenna

k1 and K2 ranges

Detailed Description

Embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. The components described below include those that can be easily conceived by those skilled in the art or substantially the same. Further, the following configurations may be combined as appropriate. Various omissions, substitutions, and changes in the structure can be made without departing from the spirit of the invention.

(embodiment 1)

A detection system 1 and a detection apparatus 20 according to embodiment 1 will be described. The detection system 1 is a system that determines the state of a detection object based on the detection result of the detection device 20. The detection system 1 is provided in, for example, a vehicle 2 and determines a state of a detection object in the vehicle 2. The detection system 1 determines the movement of the occupant, for example, by seating of the occupant, but is not limited thereto. The detection system 1 will be described in detail below.

As shown in fig. 1, the detection system 1 includes: an RFID (Radio Frequency identification) reader 10 as a reading device; a plurality of detection devices 20; and an ECU (Electronic Control Unit)30 as a determination section. Here, the detection system 1 is a system that performs Near Field Communication using Communication technology such as RFID or NFC (Near Field Communication). The detection system 1 is not limited to RFID and NFC, as long as it is a technology of short-range wireless communication.

the RFID reader 10 is a reading device that transmits and receives signals. The RFID reader 10 is provided in the vehicle 2, for example, in an AV console, a meter, a room light, a window glass, a sunroof, or the like. The RFID reader 10 transmits a transmission signal including a signal for power supply and a carrier wave for transmitting a signal by each detection device 20, for example. In addition, the RFID reader 10 receives detection signals from the respective detectors 20. As shown in fig. 2, the RFID reader 10 includes a transmitting/receiving unit 11 and a reading-side antenna 12. The transmission/reception unit 11 includes a transmission unit 11a and a reception unit 11 b.

The transmission unit 11a is a circuit connected to the reading-side antenna 12 and transmits radio waves including signals. The transmitter 11a outputs a transmission signal including, for example, a signal for power supply and a carrier wave for transmission of the signal by each detection device 20 to the reading-side antenna 12. The transmission signal may include a command signal or the like as a command in addition to the power supply signal and the carrier wave.

The receiving unit 11b is a circuit connected to the reading-side antenna 12 and receives radio waves including signals. The signal receiving unit 11b receives the detection signals transmitted from the detection devices 20 via the reading-side antenna 12. The receiver 11b demodulates the received detection signal and outputs the demodulated detection signal to the ECU 30.

The reading-side antenna 12 is a device that transmits and receives radio waves including signals. The reader antenna 12 is connected to the transmitter 11a, and transmits a transmission signal including a power supply signal and a carrier wave output from the transmitter 11a to each detection device 20. In addition, the reading-side antenna 12 receives detection signals from the respective detection devices 20, and outputs the received detection signals to the receiving section 11 b.

each detection device 20 is provided in the vehicle 2, and transmits a detection signal to the RFID reader 10. Each detection device 20 does not have a battery for storing electric power, and uses a passive RFID that is activated by using a signal for power supply (also called electric power) transmitted from the RFID reader 10 as power. The detection devices 20 are respectively provided at different positions of the vehicle 2. As shown in fig. 3 and 4, the detection devices 20 are provided in a plurality of seats 2a of the vehicle 2, for example. Each detection device 20 is provided, for example, on the seating surface portion 2b of the seat 2 a.

Each detection device 20 includes: a loop antenna 21 as an antenna, a switch section 22 as a gain reduction section, and an RFID detection circuit 23 as a signal output section. The loop antenna 21 transmits and receives signals to and from the RFID reader 10. The loop antenna 21 is formed by annularly winding an antenna conductor one or more times. The loop antenna 21 includes a winding start end portion 21a on the winding start side and a winding end portion 21b on the winding end side (see fig. 1). The loop antenna 21 is connected to an RFID detection circuit 23 via a switch unit 22. In the loop antenna 21, for example, a start end portion 21a is connected to a 1 st switch circuit 22R described later, and an end portion 21b is connected to a 2 nd switch circuit 22L. When the 1 st and 2 nd switching circuits 22R and 22L are in a connected state (on), the loop antenna 21 receives a transmission signal including a signal for power supply and a carrier transmitted from the RFID reader 10. The loop antenna 21 outputs the received transmission signal to the RFID detection circuit 23 via the 1 st and 2 nd switching circuits 22R and 22L. Then, the loop antenna 21 transmits the detection signal output from the RFID detection circuit 23 via the 1 st and 2 nd switch circuits 22R and 22L to the RFID reader 10. On the other hand, when the 1 st and 2 nd switching circuits 22R and 22L are in the disconnected state (disconnected), the loop antenna 21 does not receive the transmission signal including the power supply signal and the carrier wave transmitted from the RFID reader 10.

The switch unit 22 is a push-type, slide-type, or other switch. The switch unit 22 includes a 1 st switch circuit 22R and a 2 nd switch circuit 22L. The 1 st switching circuit 22R is a circuit that switches the electrical connection on or off. The 1 st switching circuit 22R is provided between the 1 st circuit terminal 23a of the RFID detection circuit 23 and the leading end portion 21a of the loop antenna 21. The 1 st switch circuit 22R is configured to include a switch terminal 22a as a 1 st terminal, a switch terminal 22b as a 2 nd terminal, and a switching lever 22 c. The switch terminals 22a and 22b function as the 1 st operating point for reducing the gain of the loop antenna 21. The switch terminals 22a and 22b are located within a range K1 on the loop antenna 21 from the 1 st circuit terminal 23a of the RFID detection circuit 23 to a position separated by λ/8 in the 1 st extending direction of the loop antenna 21. Here, "λ" refers to the wavelength of the radio wave received by the loop antenna 21. The switch terminal 22a is connected to the 1 st circuit terminal 23a of the RFID detection circuit 23. The switch terminal 22b is connected to the start end portion 21a of the loop antenna 21. The switching lever 22c switches the switch terminals 22a and 22b to a state of being electrically connected to each other (on) or a state of being not electrically connected to each other (off). That is, the switching lever 22c switches the 1 st circuit terminal 23a of the RFID detection circuit 23 and the leading end portion 21a of the loop antenna 21 to the energized state or the non-energized state.

The 2 nd switch circuit 22L is a circuit that switches the electrical connection on or off. The 2 nd switch circuit 22L is provided between the 2 nd circuit terminal 23b of the RFID detection circuit 23 and the terminal portion 21b of the loop antenna 21. The 2 nd switch circuit 22L includes a switch terminal 22d as a 3 rd terminal, a switch terminal 22e as a 4 th terminal, and a switching lever 22 f. The switch terminals 22d and 22e function as the 2 nd operating point for reducing the gain of the loop antenna 21. The switch terminals 22d and 22e are located within a range K2 on the loop antenna 21 from the 2 nd circuit terminal 23b of the RFID detection circuit 23 to a position apart from λ/8 in the 2 nd extending direction of the loop antenna 21. The switch terminal 22d is connected to the 2 nd circuit terminal 23b of the RFID detection circuit 23. The switch terminal 22e is connected to the terminal portion 21b of the loop antenna 21. The switching lever 22f switches the switch terminals 22d and 22e to a state of being electrically connected to each other (on) or a state of being not electrically connected to each other (off). That is, the switching lever 22f switches the 2 nd circuit terminal 23b of the RFID detection circuit 23 and the terminal portion 21b of the loop antenna 21 to an energized state or a non-energized state.

the switch unit 22 sets the 1 st and 2 nd switch circuits 22R and 22L to either on or off states when an external force is applied due to the movement of the passenger to be detected. When no external force is applied by the movement of the passenger, the switch unit 22 sets the 1 st and 2 nd switch circuits 22R and 22L to the other of the on and off states. In embodiment 1, the switch unit 22 is turned on when an external force is applied thereto, and is turned off when no external force is applied thereto (momentary operation). The switch unit 22 is switched to the on state by the pressing force of the passenger when the passenger is seated on the seat 2a, for example, and is switched to the off state by being released from the pressing force of the passenger when the passenger is not seated on the seat 2 a.

For example, when an occupant is not seated in the seat 2a, the switch unit 22 is switched to a gain reduction state in which the gain of the loop antenna 21 is reduced by setting the switch terminals 22a and 22b of the 1 st switch circuit 22R to a non-connected state (off) and setting the switch terminals 22d and 22e of the 2 nd switch circuit 22L to a non-connected state (off). That is, when the passenger is not seated on the seat 2a, the switch unit 22 switches the 1 st and 2 nd switch circuits 22R and 22L to the off state, and thereby the antenna matching between the RFID detection circuit 23 and the loop antenna 21 is brought into a mismatch state. In other words, the switch unit 22 switches the 1 st and 2 nd switch circuits 22R and 22L to the off state, and the impedance of the RFID detection circuit 23 and the loop antenna 21 does not match. Thereby, the detection device 20 has a reduced reception sensitivity in a case where the passenger is not seated on the seat 2a, so that the RFID detection circuit 23 can be deactivated.

On the other hand, when the passenger is seated in the seat 2a, the switch unit 22 is switched to the gain non-reduction state in which the gain of the loop antenna 21 is not reduced by setting the switch terminals 22a and 22b of the 1 st switch circuit 22R to the connection state (on) and setting the switch terminals 22d and 22e of the 2 nd switch circuit 22L to the connection state (on). That is, when the passenger sits on the seat 2a, the switch unit 22 switches the 1 st and 2 nd switch circuits 22R and 22L to the on state, and thereby brings the antenna matching between the RFID detection circuit 23 and the loop antenna 21 into the matching state. In other words, the switch unit 22 switches the 1 st and 2 nd switch circuits 22R and 22L to the on state, thereby matching the impedances of the RFID detection circuit 23 and the loop antenna 21. Thereby, the detection device 20 does not decrease in reception sensitivity when an occupant is seated in the seat 2a, so the RFID detection circuit 23 can be activated by a signal for power supply from the RFID reader 10.

The RFID detection circuit 23 is a circuit that outputs a detection signal. Here, the detection signal is a signal including an identifier (for example, a serial number, a symbol, or the like) different for each detection device 20. The RFID detection circuit 23 drives the power supply signal transmitted from the RFID reader 10 as power to generate a detection signal. The RFID detection circuit 23 includes, for example, the 1 st and 2 nd circuit terminals 23a and 23b, a rectifier circuit 23c, a storage unit 23d, and an IC circuit 23 e. The 1 st and 2 nd circuit terminals 23a and 23b are portions electrically connected to an external device. The 1 st circuit terminal 23a is connected to the switch terminal 22a of the 1 st switch 22R, and the 2 nd circuit terminal 23b is connected to the switch terminal 22d of the 2 nd switch circuit 22L.

The rectifier circuit 23c is connected to the loop antenna 21 via the 1 st and 2 nd switching circuits 22R and 22L, etc., and rectifies alternating current (a signal for power supply) output from the loop antenna 21 to generate direct current. The rectifier circuit 23c is connected to the storage unit 23d and the IC circuit 23e, and supplies the generated dc power to the storage unit 23d and the IC circuit 23e via a filter circuit not shown.

The storage unit 23d is a circuit that stores identifiers different for each detection device 20. The storage unit 23d is connected to the IC circuit 23e, and the identifier is referred to by each IC circuit 23.

The IC circuit 23e is connected to the storage unit 23d and the loop antenna 21, acquires the identifier stored in the storage unit 23d, and outputs the detection signal obtained by modulating the carrier wave to the loop antenna 21 via the 1 st and 2 nd switching circuits 22R and 22L, and the like, based on the acquired identifier.

The ECU30 is an electronic circuit that controls the entire vehicle 2. The ECU30 is configured to include an electronic circuit mainly including a known microcomputer including: CPU, ROM, RAM and interface which constitute the memory. The ECU30 is connected to the RFID reader 10, for example, and determines the state of the detection target in the vehicle 2 based on the detection signal received by the RFID reader 10. The ECU30 associates in advance the identifier included in the detection signal with the state of the detection target in the vehicle 2. For example, the ECU30 associates different identifiers with the seats 2a of the vehicle 2. Thus, the ECU30 can determine the state of each seat 2a based on the identifier. The ECU30 can control the transmitter 11a to transmit a transmission signal including a signal for power supply and a carrier wave to each detection device 20 at predetermined intervals (for example, 1 second intervals).

Next, an operation example of the detection system 1 will be described with reference to fig. 5. The ECU30 of the detection system 1 determines whether the ACC (accessory) electric power source or the IG (ignition) electric power source is on (step S1). When the ACC power source or the IG power source is turned on (step S1; yes), the ECU30 detects each detection device 20 by the RFID reader 10 (step S2). For example, the ECU30 transmits a transmission signal including a signal for power supply and a carrier wave from the RFID reader 10 to each detection device 20 at predetermined intervals (for example, at 1 second intervals). Next, the ECU30 determines whether there is a response by each detection device 20 (step S3). When the 1 st and 2 nd switching circuits 22R and 22L are turned on by an external force caused by the movement of the passenger, the RFID detection circuit 23 and the loop antenna 21 are electrically connected to each detection device 20, and the gain of the loop antenna 21 is not lowered, so that each detection device 20 is activated. In this case, each detection device 20 transmits a detection signal from the RFID detection circuit 23 to the RFID reader 10 via the loop antenna 21. When the 1 st and 2 nd switching circuits 22R and 22L are in the off state due to the fact that the external force due to the movement of the passenger is not applied to each detection device 20, the electrical connection between the RFID detection circuit 23 and the loop antenna 21 is cut off, and the gain of the loop antenna 21 is lowered, so that the detection device 20 is not activated. In this case, each detection device 20 does not transmit a detection signal from the RFID detection circuit 23 to the RFID reader 10 via the loop antenna 21.

When receiving the detection signal from each detection device 20, the RFID reader 10 outputs an identifier of the received detection signal to the ECU 30. When the identifier is output from the RFID10, the ECU30 determines that there is a response from each detection device 20. When the ECU30 determines that there is a response from each detection device 20 (step S3; yes), it determines the state of the detection object in the vehicle 2 based on the identifier (step S4). For example, the ECU30 determines that the passenger is seated in the seat 2a corresponding to the identifier output from the RFDI reader 10. Next, the ECU30 determines whether the ACC electric power source or the IG electric power source is on (step S5). When the ACC power source or the IG power source is turned off (step S5; YES), the ECU30 ends the processing. When the ACC power source or the IG power source is turned on (step S5; no), the ECU30 returns to step S2 and detects each detection device 20 by the RFID reader 10. In step S1, if the ACC power supply or the IG power supply is turned off (step S1; no), the ECU30 ends the process. In addition, in the above-described step S3, in the case where there is no response from each of the inspection devices 20 (step S3; NO), the ECU30 again detects each of the inspection devices 20 using the RFID reader 10 (steps S1, S2).

As described above, the detection device 20 according to embodiment 1 includes: a loop antenna 21; an RFID detection circuit 23; and a switch section 22. The loop antenna 21 transmits and receives radio waves including signals. The RFID detection circuit 23 includes a 1 st circuit terminal 23a and a 2 nd circuit terminal 23b connected to the loop antenna 21. The RFID detection circuit 23 starts up with a signal for circuit supply included in the signal received by the loop antenna 21 as power, and outputs a detection signal to the loop antenna 21. The switch unit 22 switches between a gain reduction state in which the gain of the loop antenna 21 is reduced and a gain non-reduction state in which the gain of the loop antenna 21 is not reduced, depending on the state of the detection target. Here, when the wavelength of the radio wave is λ, the switch unit 22 has the switch terminals 22a and 22b for reducing the gain of the loop antenna 21 in a range K1 on the loop antenna 21 from the 1 st circuit terminal 23a to a position separated by λ/8 in the 1 st extending direction of the loop antenna 21. The switch unit 22 further includes switch terminals 22d and 22e for reducing the gain of the loop antenna 21 in a range K2 on the loop antenna 21 from the 2 nd circuit terminal 23b to a position separated by λ/8 in the 2 nd extending direction of the loop antenna 21.

According to this configuration, the detection device 20 can completely electrically disconnect the loop antenna 21 and the RFID detection circuit 23 according to the state of the detection object. Thereby, the detection device 20 can mismatch the impedances of the RFID detection circuit 23 and the antenna 21, and can realize a gain reduction state in which the gain of the loop antenna 21 is reduced. Thereby, the detection device 20 can reduce the reception sensitivity of the loop antenna 21 to invalidate the loop antenna 21, and cannot activate the RFID detection circuit 23 even if a signal for power supply is transmitted. In addition, the detection device 20 can electrically connect the loop antenna 21 and the RFID detection circuit 23 according to the state of the detection object. Thereby, the detection device 20 can match the impedances of the RFID detection circuit 23 and the antenna 21, and can realize a gain non-reduction state in which the gain of the loop antenna 21 is not reduced. Thus, the detection device 20 can activate the loop antenna 21 without lowering the reception sensitivity of the loop antenna 21, and can activate the RFID detection circuit 23 by a signal for power supply. As a result, the detection device 20 can suppress erroneous detection that a detection signal is output even if, for example, a passenger is not seated on the seat 2a, and can improve the detection accuracy of the detection object. The detection device 20 can further reduce the reception sensitivity of the RFID detection circuit 23 by directly connecting the switch terminals 22a, 22d to the 1 st and 2 nd circuit terminals 23a, 23b, respectively, to shorten the remaining conductor length at both ends of the RFID detection circuit 23. Thereby, the distance between the detection device 20 and the RFID reader 10 can be relatively shortened, and the detection area can be enlarged.

In the above-described detection apparatus 20, the switch terminals 22a, 22b, 22d, 22e are points of action at which the RFID detection circuit 23 and the loop antenna 21 are set in an energized state or a non-energized state. According to this configuration, the detection device 20 can completely electrically disconnect the loop antenna 21 and the RFID detection circuit 23 according to the state of the detection object, thereby enabling a gain reduction state.

In the above-described detection device 20, the switch section 22 is configured to include: a 1 st switch circuit 22R capable of switching the switch terminals 22a and 22b to a mutually electrically connected state or a non-connected state; and a 2 nd switch circuit 22L capable of switching the switch terminals 22d, 22e to a mutually electrically connected state or a non-connected state. The switch unit 22 can switch between a gain non-reduced state in which the switch terminals 22a and 22b are connected and the switch terminals 22d and 22e are connected and a gain reduced state in which the switch terminals 22a and 22b are disconnected and the switch terminals 22d and 22e are disconnected. According to this configuration, the detection device 20 can completely electrically disconnect the loop antenna 21 and the RFID detection circuit 23 according to the state of the detection object, thereby enabling a gain reduction state. In addition, the detection device 20 can electrically connect the loop antenna 21 and the RFID detection circuit 23 according to the state of the detection object, thereby enabling a gain non-reduction state.

The detection system 1 according to embodiment 1 includes an RFID reader 10, a detection device 20, and an ECU 30. The RFID reader 10 transmits and receives radio waves including signals, and transmits transmission signals including at least signals for power supply. The detection device 20 is constituted to include: a loop antenna 21, an RFID detection circuit 23, and a switch unit 22. The loop antenna 21 transmits and receives signals to and from the RFID reader 10. The RFID detection circuit 23 has a 1 st circuit terminal 23a and a 2 nd circuit terminal 23b connected to the loop antenna 21, and outputs a detection signal to the loop antenna 21 using a power supply signal included in a signal received by the loop antenna 21 as power. The switch unit 22 switches to a gain reduction state in which the gain of the loop antenna 21 is reduced or a gain non-reduction state in which the gain of the loop antenna 21 is not reduced, depending on the state of the detection target. The ECU30 is connected to the RFID reader 10, and determines the state of the detection target based on the detection signal received by the RFID reader 10. Here, when the wavelength of the radio wave is λ, the switch unit 22 has switch terminals 22a and 22b for reducing the gain of the loop antenna 21 in a range K1 on the loop antenna 21 from the 1 st circuit terminal 23a along the 1 st extending direction of the loop antenna 21 to a position separated by λ/8. The switch unit 22 further includes switch terminals 22d and 22e for reducing the gain of the loop antenna 21 in a range K2 on the loop antenna 21 from the 2 nd circuit terminal 23b along the 2 nd extending direction of the loop antenna 21 to a position separated by λ/8. With this configuration, the detection system 1 can achieve the same effects as those of the detection device 20 described above.

(modification of embodiment 1)

Next, a detection device 20A according to modification 1 of embodiment 1 will be described with reference to fig. 6. In modification 1 of embodiment 1, the same reference numerals are used for the components equivalent to those of embodiment 1, and detailed description thereof is omitted. The detection apparatus 20A differs from the detection apparatus 20 of embodiment 1 in that: the 1 st and 2 nd switching circuits 22R and 22L are connected to the loop antenna 21 via electric wires 26A and 26B. The detection device 20A includes a loop antenna 21, 1 st and 2 nd switching circuits 22R and 22L, electric wires 26A and 26B, and an RFID detection circuit 23. The electric wire 26A is configured to include: 2 conductors 26a and a sheath 26b covering each conductor 26 a. Each conductor 26a extends in the extending direction. One end of the one conductor 26a is connected to the 1 st circuit terminal 23a of the RFID detection circuit 23, and the other end is connected to the switch terminal 22a of the 1 st switch circuit 22R. The other conductor 26a has one end connected to the start end 21a of the loop antenna 21 and the other end connected to the switch terminal 22b of the 1 st switch circuit 22R. The conductors 26a are arranged adjacent to each other in a direction intersecting the extending direction. The conductors 26a are disposed adjacent to each other, and thereby cancel at least a part of magnetic fields generated by the currents flowing through the current paths. That is, the conductors 26a cause the current flowing through one current path and the current flowing through the other current path to flow in opposite directions to each other, thereby canceling the magnetic fields from each other. This allows each conductor 26a to suppress the influence of the magnetic field on the loop antenna 21.

Similarly, the electric wire 26B is configured to include: 2 conductors 26c and a sheath 26d covering each conductor 26 c. Each conductor 26c extends in the extending direction. One end of the one conductor 26c is connected to the 2 nd circuit terminal 23b of the RFID detection circuit 23, and the other end is connected to the switch terminal 22d of the 2 nd switch circuit 22L. The other conductor 26c has one end connected to the terminal portion 21b of the loop antenna 21 and the other end connected to the switch terminal 22e of the 2 nd switch circuit 22L. The conductors 26c are arranged adjacent to each other in a direction intersecting the extending direction. The conductors 26c are disposed adjacent to each other, and thereby cancel at least a part of magnetic fields generated by the currents flowing through the current paths. That is, the conductors 26c cause the current flowing through one current path and the current flowing through the other current path to flow in opposite directions to each other, thereby canceling the magnetic fields from each other. This allows each conductor 26c to suppress the influence of the magnetic field on the loop antenna 21.

As described above, in the detection device 20A according to the 1 st modification of the 1 st embodiment, the 1 st and 2 nd switches 22R and 22L are connected to the loop antenna 21 via the wires 26A and 26B. According to this configuration, the detection device 20A can dispose the 1 st and 2 nd switching circuits 22R, 22L apart from the loop antenna 21, and can improve the degree of freedom of design. In addition, the detection device 20A can suppress the influence of the magnetic field of the electric wires 26A, 26B on the antenna characteristics of the loop antenna 21, and therefore can suppress the performance degradation of the loop antenna 21.

Next, a detection device 20B according to variation 2 of embodiment 1 will be described with reference to fig. 7. The detection apparatus 20B is different from the detection apparatus 20 of embodiment 1 in that: the 1 st and 2 nd switching circuits 22R and 22L are connected to the loop antenna 21 via coaxial cables 27A and 27B. The detection device 20B includes a loop antenna 21, 1 st and 2 nd switching circuits 22R and 22L, coaxial cables 27A and 27B, and an RFID detection circuit 23. The coaxial cable 27A is configured to include: a core wire 27 a; a shield braid 27b provided concentrically with the core wire 27 a; and an insulator (not shown) that insulates the core wire 27a and the shield braid 27 b. The coaxial cable 27A extends in the extending direction. One end of the core wire 27a is connected to the 1 st circuit terminal 23a of the RFID detection circuit 23, and the other end is connected to the switch terminal 22a of the 1 st switch circuit 22R. One end of the shield braid 27b is connected to the leading end portion 21a of the loop antenna 21, and the other end is connected to the switch terminal 22b of the 1 st switch circuit 22R. Since the coaxial cable 27A restricts the magnetic field when the current flows inside the shield braid 27b, the influence of the magnetic field on the loop antenna 21 can be suppressed.

Similarly, the coaxial cable 27B is configured to include: a core wire 27 c; a shield braid 27d provided concentrically with the core wire 27 c; and an insulator (not shown) that insulates the core wire 27c and the shield braid 27 d. The coaxial cable 27B extends in the extending direction. One end of the core wire 27c is connected to the 2 nd circuit terminal 23b of the RFID detection circuit 23, and the other end is connected to the switch terminal 22e of the 2 nd switch circuit 22L. One end of the shield braid 27d is connected to the terminal portion 21b of the loop antenna 21, and the other end is connected to the switch terminal 22d of the 2 nd switch circuit 22L. Since the coaxial cable 27B restricts the magnetic field when the current flows inside the shield braid 27d, the influence of the magnetic field on the loop antenna 21 can be suppressed.

As described above, in the detection device 20B according to the 2 nd modification of the 1 st embodiment, the 1 st switch and the 2 nd switches 22R and 22L are connected to the loop antenna 21 via the coaxial cables 27A and 27B. According to this configuration, the detection device 20B can dispose the 1 st and 2 nd switching circuits 22R and 22L apart from the loop antenna 21, and can improve the degree of freedom in design. In addition, the detection apparatus 20B can suppress the influence of the magnetic field of the coaxial cables 27A, 27B on the antenna characteristics of the loop antenna 21, and therefore can suppress the performance degradation of the loop antenna 21.

Next, a detection device 20C according to modification 3 of embodiment 1 will be described with reference to fig. 8. The detection device 20C is different from the detection device 20 of embodiment 1 in that a dipole antenna 40 is provided instead of the loop antenna 21. The detection device 20C includes a dipole antenna 40, 1 st and 2 nd switching circuits 22R and 22L, and an RFID detection circuit 23. The dipole antenna 40 includes a 1 st element 41 and a 2 nd element 42, and transmits and receives radio waves including signals. The 1 st switch circuit 22R is provided between the 1 st circuit terminal 23a of the RFID detection circuit 23 and one end 41a of the 1 st element 41. The switch terminals 22a and 22b of the 1 st switch circuit 22R are located within a range K1 on the dipole antenna 40 from the 1 st circuit terminal 23a of the RFID detection circuit 23 to a position separated by λ/8 in the 1 st extending direction of the dipole antenna 40. Here, "λ" refers to the wavelength of the radio wave received by the dipole antenna 40. The switch terminal 22a of the 1 st switch circuit 22R is connected to the 1 st circuit terminal 23a of the RFID detection circuit 23, and the switch terminal 22b is connected to the one end 41a of the 1 st element 41. The 1 st switch circuit 22R switches the 1 st circuit terminal 23a of the RFID detection circuit 23 and the one end 41a of the 1 st element 41 to an energized state or a non-energized state.

The 2 nd switch circuit 22L is provided between the 2 nd circuit terminal 23b of the RFID detection circuit 23 and one end 42a of the 2 nd element 42. The switch terminals 22d and 22e of the 2 nd switch circuit 22L are located within a range K2 on the dipole antenna 40 from the 2 nd circuit terminal 23b of the RFID detection circuit 23 to a position separated by λ/8 in the 2 nd extending direction of the dipole antenna 40. The switch terminal 22d of the 2 nd switch circuit 22L is connected to the 2 nd circuit terminal 23b of the RFID detection circuit 23, and the switch terminal 22e is connected to the one end 42a of the 2 nd element 42. The 2 nd switch circuit 22L switches the 2 nd circuit terminal 23b of the RFID detection circuit 23 and the one end 42a of the 2 nd element 42 to an energized state or a non-energized state.

The detection device 20C switches to a gain reduction state for reducing the gain of the dipole antenna 40 by, for example, setting the switch terminals 22a, 22b of the 1 st switch circuit 22R to a non-connected state (off) and setting the switch terminals 22d, 22e of the 2 nd switch circuit 22L to a non-connected state (off) according to the state of the detection object. In addition, the detection device 20C switches to a gain non-reduction state in which the gain of the dipole antenna 40 is not reduced by setting the switch terminals 22a, 22b of the 1 st switch circuit 22R to a connection state (on) and setting the switch terminals 22d, 22e of the 2 nd switch circuit 22L to a connection state (on) according to the state of the detection object.

As described above, the detection device 20C according to modification 3 of embodiment 1 can completely electrically disconnect the dipole antenna 40 and the RFID detection circuit 23 according to the state of the detection object. Thereby, the detection device 20C can realize a gain reduction state, and can deactivate the dipole antenna 40. In addition, the detection device 20C can electrically connect the dipole antenna 40 and the RFID detection circuit 23 according to the state of the detection object. Thereby, the detection device 20C can realize the gain non-reduction state, and can activate the dipole antenna 40. As a result, the detection apparatus 20C can improve the detection accuracy of the detection object. The detection device 20C can further reduce the reception sensitivity of the RFID detection circuit 23 by directly connecting the switch terminals 22a, 22d to the 1 st and 2 nd circuit terminals 23a, 23b, respectively, to shorten the remaining conductor length at both ends of the RFID detection circuit 23. Thereby, the distance between the detection device 20C and the RFID reader 10 can be relatively shortened, and the detection area can be enlarged.

(embodiment 2)

Next, referring to fig. 9, a detection device 20D according to embodiment 2 will be described. In embodiment 2, the same reference numerals are used for the same components as those in embodiment 1, and detailed description thereof is omitted. The detection device 20D according to embodiment 2 is different from the detection device 20 according to embodiment 1 in that a capacitance unit 24 is provided instead of the switch unit 22. The detection device 20D includes a loop antenna 21, a capacitor 24 as a gain reduction unit, and an RFID detection circuit 23. The capacitor unit 24 includes a 1 st capacitor circuit 24R and a 2 nd capacitor circuit 24L. The 1 st capacitance circuit 24R can switch the loop antenna 21 to a gain-reduced state or a gain-non-reduced state. The 1 st capacitance circuit 24R is provided between the 1 st circuit terminal 23a of the RFID detection circuit 23 and the leading end portion 21a of the loop antenna 21. The 1 st capacitor circuit 24R is configured to include a plate 24a as a 1 st plate, a plate 24b as a 2 nd plate, and a 1 st plate driving mechanism (not shown). The pair of flat plates 24a and 24b can function as the 1 st action point for reducing the gain of the loop antenna 21. The pair of flat plates 24a and 24b are disposed to face each other and are movably provided. The pair of flat plates 24a and 24b are brought into a chargeable state, which is a state in which they can store electric charges, by being brought close to each other, and are brought into an uncharged state, which is a state in which they cannot store electric charges, by being separated from each other. The pair of flat plates 24a and 24b are located within a range K1 on the loop antenna 21 from the 1 st circuit terminal 23a of the RFID detection circuit 23 to a position separated by λ/8 in the 1 st extending direction of the loop antenna 21. One flat plate 24a is connected to the 1 st circuit terminal 23a of the RFID detection circuit 23. The other plate 24b is connected to the leading end portion 21a of the loop antenna 21. The 1 st plate drive mechanism is switched to a chargeable state by bringing the pair of flat plates 24a, 24b close to each other, and to an uncharged state by moving the pair of flat plates 24a, 24b away from each other.

The 2 nd capacitor circuit 24L includes a plate 24c as a 3 rd plate, a plate 24d as a 4 th plate, and a 2 nd plate drive mechanism (not shown). The pair of flat plates 24c and 24d can function as the 2 nd action point for reducing the gain of the loop antenna 21. The pair of flat plates 24c and 24d are disposed to face each other and are movably provided. The pair of flat plates 24c and 24d are brought into a chargeable state, which is a state in which charge can be stored, by being brought close to each other, and are brought into an uncharged state, which is a state in which charge cannot be stored, by being separated from each other. The pair of flat plates 24c and 24d are located within a range K2 on the loop antenna 21 from the 2 nd circuit terminal 23b of the RFID detection circuit 23 to a position separated by λ/8 in the 2 nd extending direction of the loop antenna 21. One flat plate 24c is connected to the 2 nd circuit terminal 23b of the RFID detection circuit 23. The other plate 24d is connected to the terminal portion 21b of the loop antenna 21. The 2 nd plate drive mechanism is switched to a chargeable state by bringing the pair of flat plates 24c, 24d close to each other, and to an uncharged state by bringing the pair of flat plates 24c, 24d away from each other.

The detection device 20D switches to a gain reduction state in which the gain of the loop antenna 21 is reduced by setting the pair of plates 24a, 24b of the 1 st capacitor circuit 24R to an uncharged state and setting the pair of plates 24c, 24D of the 2 nd capacitor circuit 24L to an uncharged state according to the state of the detection object. In addition, the detection device 20D switches the gain non-reduction state in which the gain of the loop antenna 21 is not reduced by setting the pair of plates 24a and 24b of the 1 st capacitor circuit 24R to the chargeable state and setting the pair of plates 24c and 24D of the 2 nd capacitor circuit 24L to the chargeable state according to the state of the detection object.

As described above, the detection device 20D according to embodiment 2 is configured to include: a 1 st capacitor circuit 24R that switches the pair of flat plates 24a, 24b to a chargeable state or a non-chargeable state; and a 2 nd capacitance circuit 24L that switches the pair of flat plates 24c, 24d to a chargeable state or a non-chargeable state. The detection device 20D is capable of switching a gain non-lowered state that sets the pair of flat plates 24a, 24b to a chargeable state and the pair of flat plates 24c, 24D to a chargeable state and a gain lowered state; the gain-reduced state sets the pair of flat plates 24a, 24b to the non-chargeable state and sets the pair of flat plates 24c, 24d to the non-chargeable state.

According to this configuration, the detection device 20D can completely electrically disconnect the loop antenna 21 and the RFID detection circuit 23 according to the state of the detection object. Thereby, the detection device 20D can realize a gain reduction state, and can deactivate the loop antenna 21. In addition, the detection device 20D can electrically connect the loop antenna 21 and the RFID detection circuit 23 according to the state of the detection object. Thereby, the detection device 20D can realize the gain non-reduction state, and can make the loop antenna 21 effective. As a result, the detection device 20D can improve the detection accuracy of the detection object. Since the detection device 20D uses the capacitor unit 24, the contact point of the switch unit 22 of embodiment 1 is not necessary, and the problem of contact failure can be solved. The detection device 20D can further reduce the reception sensitivity of the RFID detection circuit 23 by directly connecting the flat plates 24a, 24c to the 1 st and 2 nd circuit terminals 23a, 23b, respectively, to shorten the remaining conductor length at both end portions of the RFID detection circuit 23. Thereby, the distance between the detection device 20D and the RFID reader 10 can be relatively shortened, and the detection area can be enlarged.

(modification of embodiment 2)

Next, a detection device 20E according to a modification of embodiment 2 will be described with reference to fig. 10. The detection device 20E is different from the detection device 20D of embodiment 2 in that a dipole antenna 40 is provided instead of the loop antenna 21. The detection device 20E includes a dipole antenna 40, 1 st and 2 nd capacitance circuits 24R and 24L, and an RFID detection circuit 23. The 1 st capacitance circuit 24R is provided between the 1 st circuit terminal 23a of the RFID detection circuit 23 and one end 41a of the 1 st element of the loop antenna 40. The pair of flat plates 24a and 24b of the 1 st capacitor circuit 24R is located in a range K1 on the dipole antenna 40 from the 1 st circuit terminal 23a of the RFID detection circuit 23 to a position separated by λ/8 in the 1 st extending direction of the dipole antenna 40. In the 1 st capacitor circuit 24R, the plate 24a is connected to the 1 st circuit terminal 23a of the RFID detection circuit 23, and the plate 24b is connected to the one end 41a of the 1 st element 41.

The 2 nd capacitance circuit 24L is provided between the 2 nd circuit terminal 23b of the RFID detection circuit 23 and one end 42a of the 2 nd element 42. The pair of plates 24c and 24d of the 2 nd capacitance circuit 24L is located within a range K2 on the dipole antenna 40 from the 2 nd circuit terminal 23b of the RFID detection circuit 23 to a position separated by λ/8 in the 2 nd extending direction of the dipole antenna 40. In the 2 nd capacitor circuit 24L, the plate 24c is connected to the 2 nd circuit terminal 23b of the RFID detection circuit 23, and the plate 24d is connected to the one end 42a of the 2 nd element 42.

The detection device 20E switches to a gain reduction state in which the gain of the dipole antenna 40 is reduced by setting the pair of flat plates 24a and 24b of the 1 st capacitance circuit 24R to an uncharged state and setting the pair of flat plates 24c and 24d of the 2 nd capacitance circuit 24L to an uncharged state according to the state of the detection object. The detection device 20E switches the pair of plates 24a and 24b of the 1 st capacitor circuit 24R to a chargeable state and the pair of plates 24c and 24d of the 2 nd capacitor circuit 24L to a chargeable state according to the state of the detection object, thereby switching the state to a gain non-reduction state in which the gain of the dipole antenna 40 is not reduced.

As described above, the detection device 20E according to the modification of embodiment 2 can completely electrically disconnect the dipole antenna 40 and the RFID detection circuit 23 according to the state of the detection object. Thereby, the detection device 20E can realize a gain reduction state, and can deactivate the dipole antenna 40. In addition, the detection device 20E can electrically connect the dipole antenna 40 and the RFID detection circuit 23 according to the state of the detection object. Thereby, the detection device 20E can realize the gain non-reduction state, and can activate the dipole antenna 40. As a result, the detection device 20E can improve the detection accuracy of the detection object. The detection device 20E can further reduce the reception sensitivity of the RFID detection circuit 23 by directly connecting the flat plates 24a, 24c to the 1 st and 2 nd circuit terminals 23a, 23b, respectively, to shorten the remaining conductor length at both end portions of the RFID detection circuit 23. Thereby, the distance between the detection device 20E and the RFID reader 10 can be relatively shortened, and the detection area can be enlarged.

(embodiment 3)

Next, referring to fig. 11, a detection device 20F according to embodiment 3 will be described. In embodiment 3, the same reference numerals are used for the same components as those in embodiment 1, and detailed description thereof is omitted. The detection device 20F according to embodiment 3 is different from the detection device 20 according to embodiment 1 in that conductors of the loop antenna 21 are connected to each other. The detection device 20F includes: the loop antenna 21, the conductive line portion 28, the switch circuit 25 as the gain reduction portion, the 1 st connection point 25d as the 1 st action point, the 2 nd connection point 25e as the 2 nd action point, and the RFID detection circuit 23. The 1 st and 2 nd connection points 25d and 25e function as points of action for reducing the gain of the loop antenna 21. The 1 st connection point 25d is located within a range K1 on the loop antenna 21 from the 1 st circuit terminal 23a of the RFID detection circuit 23 in the 1 st extending direction of the loop antenna 21 to a position apart from λ/8. The 2 nd connection point 25e is located within a range K2 on the loop antenna 21 from the 2 nd circuit terminal 23b of the RFID detection circuit 23 to a position apart from λ/8 in the 2 nd extending direction of the loop antenna 21. The 1 st and 2 nd connection points 25d and 25e are connected to the conductive line part 28.

The conductive line portion 28 is a member for connecting the conductors of the loop antenna 21. The conductive line portion 28 is formed of a conductive member and includes conductive lines 28a and 28 b. The conduction line 28a has one end connected to the 1 st connection point 25d and the other end connected to the switch terminal 25a of the switch circuit 25. The conduction line 28b has one end connected to the 2 nd connection point 25e and the other end connected to the switch terminal 25b of the switch circuit 25. The conductive line part 28 is conductive by turning on the switching circuit 25, and is non-conductive by turning off the switching circuit 25.

The switch circuit 25 is a device that switches electrical connection on or off. The switch circuit 25 is provided between the conduction line 28a and the conduction line 28b, and is connected in parallel with the RFID detection circuit 23. The switch circuit 25 includes a switch terminal 25a, a switch terminal 25b, and a switching lever 25 c. In the switch circuit 25, the switch terminal 25a is connected to the other end of the conductive line 28a, and the switch terminal 25b is connected to the other end of the conductive line 28 b. The switching lever 25c switches the switch terminals 25a and 25b to a state of being electrically connected to each other (on) or a state of being not electrically connected to each other (off). That is, the switching lever 25 switches the conducting line 28a and the conducting line 28b to the conducting state or the non-conducting state.

The detection device 20F sets the switch terminals 25a, 25b of the switch circuit 25 to a connected state (on) in accordance with the state of the detection object, for example, thereby bringing the conduction line 28a and the conduction line 28b into an energized state, and sets the antenna matching of the RFID detection circuit 23 and the loop antenna 21 to a mismatched state. In other words, the detection device 20F turns on the switch circuit 25, mismatching the impedances of the RFID detection circuit 23 and the loop antenna 21, thereby switching the loop antenna 21 to the gain-reduced state. The detection device 20F can further appropriately make the impedance mismatch by setting the on-resistance of the switch circuit 25 to be relatively small. The on-resistance of the switching circuit 25 is preferably 1 Ω or less, for example. The detection device 20F sets the switch terminals 22a and 22b of the switch circuit 25 to a non-connected state (disconnected) in accordance with the state of the detection object, thereby setting the conduction line 28a and the conduction line 28b to a non-energized state, and setting the antenna matching of the RFID detection circuit 23 and the loop antenna 21 to a matched state. In other words, the detection device 20F turns off the switch circuit 25, matches the impedance of the RFID detection circuit 23 and the loop antenna 21, and thereby switches the loop antenna 21 to the gain non-reduced state.

As described above, the detection device 20F of embodiment 3 is configured to include the switch circuit 25, and the switch circuit 25 can switch the 1 st connection point 25d and the 2 nd connection point 25e to the state of being electrically connected to each other or the non-connected state. The switch circuit 25 can switch to a gain non-reduction state in which the 1 st connection point 25d and the 2 nd connection point 25e are set in a non-connection state or a gain reduction state in which the 1 st connection point 25d and the 2 nd connection point 25e are set in a connection state.

According to this configuration, the detection device 20F can mismatch the impedances of the RFID detection circuit 23 and the loop antenna 21 according to the state of the detection object. Thereby, the detection device 20F can realize a gain reduction state, and can deactivate the loop antenna 21. In addition, the detection device 20F can match the impedance of the RFID detection circuit 23 and the loop antenna 21 according to the state of the detection object. Thereby, the detection device 20F can realize the gain non-reduction state, and can make the loop antenna 21 effective. As a result, the detection device 20F can improve the detection accuracy of the detection object.

(modification of embodiment 3)

Next, a detection device 20G according to a modification of embodiment 3 will be described with reference to fig. 12. The detection device 20G is different from the detection device 20F of embodiment 3 in that a dipole antenna 40 is provided instead of the loop antenna 21. The detection device 20F includes: dipole antenna 40, conductive line section 28, switch circuit 25, 1 st connection point 25d, 2 nd connection point 25e, and RFID detection circuit 23. The 1 st and 2 nd connection points 25d and 25e function as points of action for reducing the gain of the dipole antenna 40. The 1 st connection point 25d is located within a range K1 on the 1 st element 41 from the 1 st circuit terminal 23a of the RFID detection circuit 23 along the 1 st extending direction of the 1 st element 41 of the dipole antenna 40 to a position separated by λ/8. The 2 nd connection point 25e is located within a range K2 on the 2 nd element 42 from the 2 nd circuit terminal 23b of the RFID detection circuit 23 to a position apart from λ/8 in the 2 nd extending direction of the 2 nd element 42. The 1 st and 2 nd connection points 25d and 25e are connected to the conductive line part 28.

The conductive line part 28 is a member for connecting the conductors of the dipole antenna 40. The conductive line 28a of the conductive line part 28 has one end connected to the 1 st connection point 25d and the other end connected to the switch terminal 25a of the switch circuit 25. The conduction line 28b has one end connected to the 2 nd connection point 25e and the other end connected to the switch terminal 25b of the switch circuit 25. The conductive line part 28 is conductive by turning on the switching circuit 25, and is nonconductive by turning off the switching circuit 25.

The detection device 20G switches the conduction line 28a and the conduction line 28b to the conduction state by, for example, setting the switch terminals 25a and 25b of the switch circuit 25 to the connection state (on) in accordance with the state of the detection object, and switches to the gain reduction state in which the gain of the dipole antenna is reduced. The detection device 20G switches the conduction lines 28a and 28b to a non-conduction state by disconnecting (disconnecting) the switch terminals 22a and 22b of the switch circuit 25 in accordance with the state of the detection object, and switches to a gain non-reduction state in which the gain of the dipole antenna 40 is not reduced.

as described above, the detection device 20G according to the modification example of embodiment 3 can mismatch the impedances of the RFID detection circuit 23 and the dipole antenna 40 according to the state of the detection object. Thereby, the detection device 20G can realize a gain reduction state, and can deactivate the dipole antenna 40. In addition, the detection device 20G can match the impedance of the RFID detection circuit 23 and the dipole antenna 40 according to the state of the detection object. Thereby, the detection device 20G can realize the gain non-reduction state, and can activate the dipole antenna 40. As a result, the detection device 20G can improve the detection accuracy of the detection object.

The antennas of the detection devices 20 to 20G are exemplified by the loop antenna 21 and the dipole antenna 40, but the antennas are not limited thereto, and may be antennas such as monopole antennas.

The detection system 1 is described by taking an example in which each detection device 20 is provided in the seating surface portion 2b of the seat 2a and determines the seating of the passenger, but the detection system is not limited to this. For example, the detection system 1 may determine the fixation of the seat belt by the passenger by providing each detection device 20 to a buckle (not shown) of the seat belt. In this case, the 1 st and 2 nd switching circuits 22R and 22L are turned off when, for example, a tongue plate of a seat belt is not mounted on a buckle, and the loop antenna 21 is set to a gain-reduced state without activating the RFID detection circuit 23. The 1 st and 2 nd switching circuits 23R and 22L are turned on when the tongue plate of the seat belt is mounted on the buckle, and the RFID detection circuit 23 is activated by setting the loop antenna 21 in a gain non-reduction state.

Further, although each detection device 20 is described as being mounted on the vehicle 2, the present invention is not limited to this, and may be mounted on a ship, an airplane, a building, or the like.

The detection device 20C may connect the 1 st and 2 nd switching circuits 22R and 22L to the dipole antenna 40 via the wires 26A and 26B (coaxial cables 27A and 27B). The detection device 20D may connect the 1 st and 2 nd capacitance circuits 24R and 24L to the loop antenna 21 via the wires 26A and 26B (coaxial cables 27A and 27B). The detection device 20E may connect the 1 st and 2 nd capacitance circuits 24R and 24L to the dipole antenna 40 via the wires 26A and 26B (coaxial cables 27A and 27B). The detection device 20F may connect the switch circuit 25 to the loop antenna 21 via an electric wire 26A (coaxial cable 27A). The detection device 20G may connect the switch circuit 25 to the dipole antenna 40 via the electric wire 26A (coaxial cable 27A).