JP2013117750A - Tag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless tag for receiving a start signal from a tag reader and transmitting a response signal thereto capable of efficiently obtaining the power from a radio wave received through an antenna on a wireless tag not only while in reception processing the start signal but also while in transmission processing of the response signal.SOLUTION: A tag 10 includes an LF antenna circuit 15 having antenna coils A1 and A2. While a radio circuit 13 performs reception processing of the start signal, a first drive power is generated from a first electromotive force which is induced on the entire of an antenna coil A1. When the radio circuit performs transmission processing of the start signal, a second drive power is generated from a second electromotive force which is induced on a part of the antenna coil. The radio circuit 13 is configured to operate using the power generated on the entire or a part of the antenna coil corresponding to the respective processing.

Description

  The present invention relates to a wireless tag that performs reception processing of an activation signal and transmission processing of a response signal, and more particularly to a technology that efficiently uses power obtained from radio waves received by an antenna.

The operation of a wireless tag (hereinafter referred to as “tag”) that transmits and receives signals to and from a tag reader has two operation modes depending on the method of supplying power.
An active mode that operates with electric power from a built-in power supply (for example, a battery) and a passive mode that operates with electric power obtained from electromagnetic waves from the outside. Usually, a tag that operates in the active mode has a function that operates in the passive mode so that the tag can be authenticated even when the battery runs out.

  The communication distance is different between the active mode and the passive mode, and is several meters (meter) in the active mode and several centimeters (centimeter) in the passive mode. In the passive mode, since it is necessary to hold the tag over the tag reader, it is also referred to as proximity authentication mode, and is used not only when the battery runs out but also when strictly managing entry / exit to / from an important area or the like.

  It operates in both these modes. In the active mode, it receives a start signal in the LF (Low Frequency) band and transmits a response signal in the RF (Radio Frequency) band. In the passive mode, it receives a start signal in the LF band. A tag that transmits a response signal in the LF band using power obtained from a received radio wave is known (Patent Document 1).

JP 2010-108039 A

  However, in passive mode, in order to ensure that the response signal transmitted by the tag is received by the tag reader, in order to increase the transmission strength of the response signal as much as possible, a large amount of power is required compared to the activation signal reception processing and consumed by the radio circuit. The current to be changed greatly. Due to this change, the input impedance of the wireless circuit viewed from the power supply side (hereinafter referred to as “the impedance of the wireless circuit”) does not match the impedance of the antenna for receiving power, and is received during the response signal transmission process. There is a problem that power from radio waves cannot be used efficiently.

  Therefore, the present invention has been made in view of such a problem, and in a tag operating in the passive mode, not only at the time of reception signal reception processing but also from the radio wave received by the antenna at the time of response signal transmission processing. An object is to provide a tag that enables efficient use of electric power.

  In order to solve the above problems, a tag according to the present invention is a tag that generates power for driving a radio circuit from an electromotive force induced in an antenna circuit by radio waves, the antenna circuit including an antenna coil, When the circuit receives the activation signal, the circuit generates first drive power from the first electromotive force induced in the entire antenna coil, and when the wireless circuit performs the response signal transmission process, a part of the antenna coil is generated. The second drive power is generated from the second electromotive force induced in.

  Here, the impedance determined by the whole antenna coil is a first impedance that matches the input impedance of the wireless circuit viewed from the power supply side during reception processing, and the first electromotive force is an electromotive force corresponding to the first impedance. The impedance determined by a part of the antenna coil is a second impedance that matches the input impedance viewed from the power supply side when the transmission process is performed, and the second electromotive force is an electromotive force corresponding to the second impedance. You may make it be electric power.

Here, a connection terminal is provided at a position where a part of the antenna coil is formed starting from one end of the antenna coil, and the antenna circuit is connected to the other end of the antenna coil and the radio circuit when executing transmission processing. It may be switched from the connected state to a state in which the connection terminal and the wireless circuit are connected.
Here, at the end of the transmission process, the antenna circuit may be switched from a state where the connection terminal and the wireless circuit are connected to a state where the other end of the antenna coil and the wireless circuit are connected.

Here, the antenna coil is obtained by connecting N (N> 0) chip coils in series, the first electromotive force is an electromotive force induced in the N chip coils, and the second electromotive force is The electromotive force induced in M (N>M> 0) continuous chip coils among the N chip coils may be used.
Here, the radio wave received by the antenna circuit is an LF band radio wave, and the response signal may be transmitted in the UHF band.

  The tag according to the present invention is a tag that generates power for driving a radio circuit from an electromotive force induced in an antenna circuit by radio waves, includes an antenna coil, and the radio circuit performs a start signal reception process. Generates a first electromotive force that is induced in the entire antenna coil, and the wireless circuit generates a second electromotive force that is induced in a part of the antenna coil in response signal transmission processing, and a wireless circuit. An impedance measuring unit that repeatedly measures the input impedance of the wireless circuit viewed from the power supply side during the operation of the circuit, and the antenna circuit performs the second generation from the generation of the first electromotive force based on the measurement result of the impedance measuring unit. Either the switching to the generation of the electromotive force or the switching from the generation of the second electromotive force to the generation of the first electromotive force is performed, and the driving power for receiving the start signal is generated from the first electromotive force. It is, drive power for transmitting the response signal characterized in that it is produced from the second electromotive force.

  According to the tag according to the present invention having the above-described configuration, in the passive mode, it is possible to efficiently use the power from the radio wave received by the antenna not only during the reception signal reception process but also during the response signal transmission process. It becomes possible.

1 is a schematic configuration diagram of a tag authentication system using a tag according to Embodiment 1. FIG. The figure which shows the timing of transmission / reception of the starting signal and response signal of a tag authentication system. The figure which shows the consumption current at the time of the starting signal reception process in the radio | wireless circuit of a tag, and a response signal transmission process. FIG. 3 is a block diagram illustrating a functional configuration of a tag according to the first embodiment. (A) The block diagram of the data in the starting signal of a tag reader. (B) The block diagram of the data in the response signal of a tag. 4 is a flowchart of coil connection terminal switching processing according to the first embodiment. FIG. 4 is a block diagram illustrating a functional configuration of a tag according to a second embodiment. The figure which shows the data structure and content example of the corresponding | compatible table of the impedance value of the LF antenna circuit at the time of connecting with the connection terminal ID of the coil of Embodiment 2, and its connection terminal. 9 is a flowchart of tag signal transmission / reception processing according to the second embodiment. The flowchart of the connection terminal switching process of the coil in the LF antenna circuit of the tag of Embodiment 2. FIG. The block diagram which shows the function structure of the tag of a modification.

<Embodiment 1>
<1-1. Overview>
FIG. 1 is a schematic configuration diagram of a tag authentication system 1 using a tag 10 according to an embodiment. The tag authentication system 1 includes a tag reader 20 and a tag 10. A configuration including the control unit 21, the LF transmission unit 22, the UHF reception circuit 23, and the UHF antenna 24 is referred to as a tag reader 20.

The door 30 is locked with an electric lock 31, and the electric lock 31 is locked and unlocked according to an instruction from the control unit 21 of the tag reader 20.
FIG. 2 is a diagram illustrating transmission / reception timings of the activation signal and the response signal of the tag authentication system 1.
The LF transmission unit 22 of the tag reader 20 transmits an activation signal in the LF band (for example, 135 kHz) every fixed period ct (for example, 500 milliseconds) according to the instruction of the control unit 21. The time required for transmitting the activation signal is st (for example, 102.6 milliseconds). The tag reader 20 continues to transmit a carrier wave to supply power to the tag 10 for a time corresponding to the time required for the tag 10 to transmit the response signal after the activation signal has been transmitted. When the user holds the tag 10 over the LF transmission unit 22, an electromotive force is generated by electromagnetic induction between a coil of an LF antenna (not shown) of the LF transmission unit 22 and a coil of an LF antenna circuit (described later) of the tag 10. The electric power is supplied to the tag 10.

  The tag 10 processes data included in the activation signal with the supplied power, and transmits a response signal in the UHF band (for example, 426 MHz). The time required for transmission of the response signal is rt (for example, 25 milliseconds). As described above, the tag 10 receives the activation signal from the tag reader 20 and transmits a response signal. As shown in FIG. 3, the tag 10 receives the activation signal using the radio wave in the UHF band as shown in FIG. Since the transmission is performed so that the response signal reaches farther than the time, the current consumption of the radio circuit (described later) of the tag 10 is greatly different. In the figure, the current consumption of the radio circuit is several mA (milliampere) (for example, 1.2 mA) during the activation signal reception process, while the current consumption is several ten mA (for example, 10 mA) during the response signal transmission process. ), And there is a large difference in current consumption in the radio circuit between the activation signal reception process and the response signal transmission process.

  Since the radio circuit of the tag 10 is designed to operate at a constant voltage (for example, 3 V (volt)), the fact that the consumption current changes greatly means that the impedance of the radio circuit changes greatly. To do. If the LF antenna circuit is designed to match the impedance of the radio circuit during the activation signal reception process, the impedance of the LF antenna circuit will not match the impedance of the radio circuit during the response signal transmission process. For this reason, such a tag cannot efficiently use the power obtained from the tag reader 20 during the response signal transmission process.

  Therefore, the tag 10 is connected to the wireless circuit at a position in the middle of the coil so that the number of turns from one end of the coil of the LF antenna circuit is the number of turns of impedance that matches the impedance of the wireless circuit at the time of response signal transmission processing. The connection terminal is switched so that one end of the coil and this connection terminal are connected to the wireless circuit when transmitting a response signal, so that the electric power obtained from the tag reader 20 can be used efficiently.

  The tag reader 20 receives the response signal from the tag 10 by the UHF receiving circuit 23 via the UHF antenna 24, and the control unit 21 authenticates whether the tag 10 is a pre-registered tag based on the response signal. If the tag registered in advance is authenticated, the electric lock 31 is unlocked. In this way, the user can enter the room from the door 30 where the electric lock 31 is unlocked.

Hereinafter, the tag 10 according to the first embodiment will be described with reference to the drawings.
<1-2. Functional configuration>
FIG. 4 is a functional block diagram of the tag 10.
The tag 10 includes a control circuit 11, a storage unit 12, a radio circuit 13, a UHF antenna 14, an LF antenna circuit 15, a switch 16, a power feeding circuit 17, a power supply 18, and a power switch 19.

  The control circuit 11 generates a response signal 200 based on the activation signal reception processing function for processing the tag reader ID and the operation mode flag information included in the received activation signal 100, and the data included in the activation signal 100, and the response signal Either the power supply 18 or the power feeding circuit 17 is connected to the radio circuit 13 according to the response signal transmission processing function for controlling the transmission of 200 and the operation mode (active mode or passive mode) included in the activation signal of the tag reader 20. And a function for controlling switching of the connection terminal of the LF antenna circuit during the start signal reception process and the response signal transmission process. The control circuit 11 includes a CPU (Central Processing Unit) that executes a control program, a ROM (Read Only Memory) that stores the control program, and a nonvolatile memory (for example, a flash memory). This function is realized by the CPU executing a program stored in the ROM.

The storage unit 12 is realized by a storage medium such as a non-volatile memory, and stores identification information of its own device (hereinafter referred to as “tag ID”) registered in advance by a registration operation by a system administrator.
The radio circuit 13 receives the activation signal 100 via the LF antenna circuit 15, sends data included in the received activation signal 100 to the control circuit 11, receives the response signal 200 generated by the control circuit 11, and receives the UHF antenna 14. It has the function to transmit via.

The data structure of the activation signal 100 is shown in FIG.
As shown in the figure, the activation signal 100 includes a PR (Preamble) 101, a UW (Unique Word) 102, a reader ID 103, a flag 104, and a CRC (Cyclic Redundancy Check) 105.
PR101 is a bit string (synchronization code) indicating the start of data of the activation signal 100, and UW102 is a so-called frame synchronization signal.

The reader ID 103 is identification information of the tag reader 20 that is the transmission source of the activation signal 100.
The flag 104 is information indicating in which operation mode the active mode or the passive mode is used for communication. In the first embodiment, “0” is set for communication in the active mode, and “1” is set for communication in the passive mode. Hereinafter, the activation signal with the flag 104 “0” is referred to as an activation signal in the active mode, and the activation signal with “1” is referred to as the activation signal in the passive mode.

The CRC 105 is data for detecting whether the tag 10 that has received the activation signal 100 has an error in the activation signal 100.
Next, FIG. 5B shows the data structure of the response signal 200.
The response signal 200 includes a PR 201, a UW 202, a reader ID 203, a tag ID 204, and a CRC 205, and is generated by the control circuit 11.

PR201 is a bit string (synchronization code) indicating the start of data of the response signal 200, and UW202 is a so-called frame synchronization signal. The CRC 205 is data for the tag reader 20 that has received the response signal 200 to detect whether an error has occurred in the response signal 200.
The reader ID 203 represents identification information of the tag reader 20, and indicates which tag reader the response signal 200 corresponds to from the activation signal. That is, the response signal 200 is a response signal transmitted in response to the activation signal transmitted from the tag reader indicated by the reader ID 203.

The tag ID 204 is identification information of the tag 10 and is generated based on the tag ID stored in advance in the storage unit 12 of the own device.
The LF antenna circuit 15 has a coil (for example, a length of 20 mm (millimeters), a diameter of 11.3 mm, the number of turns from one end of a ferrite core (with magnetic permeability of 25 (H / m)) is determined by the wireless circuit 13 during the start signal reception process. The connection terminal N1 having an impedance matching with the impedance of (for example, 66 windings and an inductance of 770 μH (microhenry)) and the number of windings (for example, 33 windings) impedance matching with the impedance of the wireless circuit 13 during the response signal transmission process , Having a connection terminal N2 having a length of 10 mm and an inductance of 251 μH).

The switch 16 is a switch that selectively switches the connection terminals N1 and N2 connected to the wireless circuit 13 during the start signal reception process and the response signal transmission process in accordance with an instruction from the control circuit 11.
The power supply circuit 17 includes a bridge rectifier circuit including diodes D1 to D4, a smoothing capacitor C1, and a Zener diode D5 for generating a constant voltage. The electromotive force induced in the coil of the LF antenna circuit 15 by radio waves from the tag reader 20 Is a circuit that converts the alternating current generated by the above into a direct current of a constant voltage (for example, 3 V) and supplies power to the wireless circuit 13. Since the operation of each element is well known, description thereof is omitted.

The power source 18 is composed of, for example, a coin-type lithium battery, and supplies power for operating each circuit of the tag 10 during the active mode operation.
The power switch 19 is a switch for switching a circuit that supplies power to the wireless circuit 13 to the power supply circuit 17 in the passive mode and to the power supply 18 in the active mode.
<1-3. Operation>
FIG. 6 is a flowchart showing the processing of the control circuit 11 of the tag 10.

When the power switch (not shown) of the tag 10 is turned on, the tag 10 is initialized. Immediately after the power switch is turned on, the radio circuit 13 is connected to the power source 18 and the LF antenna circuit when receiving the activation signal. The connection terminal N1 is connected to the wireless circuit 13.
The tag reader 20 continuously transmits the activation signal 100 and a carrier wave for supplying power repeatedly (for example, every 500 milliseconds). When receiving the activation signal 100 from the tag reader 20 (step S10: YES), the control circuit 11 determines whether or not the passive mode activation signal has been received (step S11). Specifically, when the value of the flag 104 included in the received activation signal 100 is “1”, the activation signal is determined to be a passive mode activation signal (step S11: YES).

  If YES in step S11, the control circuit 11 disconnects the power source 18 from the radio circuit 13 and disconnects the radio circuit 13 if the radio circuit 13 and the power feeding circuit 17 are not connected (step S12: NO). An instruction to connect the power supply circuit 13 to the power supply circuit 17 is sent to the power switch 19. The power switch 19 disconnects the power supply 18 from the radio circuit 13 according to the instruction of the control circuit 11, and connects the power supply circuit 17 and the radio circuit 13 (step S13).

In the case of YES in step S12, the wireless circuit 13 and the power feeding circuit 17 are connected, and the tag 10 is in a state of operating in the passive mode, so it is necessary to switch the circuit for supplying power to the wireless circuit 13. Absent.
If YES in step S12 or the processing in step S13 is completed, the control circuit 11 reads the reader ID obtained from the information of the reader ID 103 included in the activation signal 100, and the tag ID of the own device obtained from the storage unit 12. Is generated and sent to the radio circuit 13 (step S14).

Next, the control circuit 11 switches the connection terminal of the LF antenna circuit 15 connected to the radio circuit 13 to the switch 16 to the connection terminal N2 having the number of turns of the impedance matching the impedance of the radio circuit 13 at the time of response signal transmission processing. Send instructions. The switch 16 switches the connection terminal connected to the radio circuit 13 to the connection terminal N2 according to the instruction of the control circuit 11 (step S15).
The radio circuit 13 receives the radio wave transmitted from the tag reader 20 and transmits the response signal 200 sent from the control circuit 11 via the UHF antenna 14 using the power generated in the LF antenna circuit 15 (step S16). .

  When the process of step S16 is completed, the control circuit 11 turns the connection terminal of the LF antenna circuit 15 connected to the switch 16 to the radio circuit 13 with an impedance that matches the impedance of the radio circuit 13 during the response signal transmission process. An instruction to switch from the connection terminal N2 to the connection terminal N1 having the number of turns of the impedance matching the impedance of the wireless circuit 13 during the activation signal reception process is sent. The switch 16 switches the connection terminal connected to the radio circuit 13 from the connection terminal N2 to the connection terminal N1 in accordance with an instruction from the control circuit 11 (step S17).

  On the other hand, when the activation signal 100 is not the activation signal in the passive mode (step S11: NO), that is, in the case of the activation signal in the active mode, the control circuit 11 does not connect the wireless circuit 13 and the power source 18 (step S18). : NO), the power supply circuit 17 is disconnected from the wireless circuit 13, and an instruction to connect the wireless circuit 13 and the power supply 18 is sent to the power supply switch 19. The power switch 19 disconnects the power feeding circuit 17 from the wireless circuit 13 in accordance with an instruction from the control circuit 11, and connects the power supply 18 and the wireless circuit 13 (step S19). If YES in step S18, the radio circuit 13 and the power source 18 are connected, and the tag 10 is in an active mode, so it is necessary to switch the circuit for supplying power to the radio circuit 13. Absent.

Next, the control circuit 11 generates a response signal 200 in the same procedure as in step S14 and sends it to the radio circuit 13 (step S20).
The radio circuit 13 transmits the response signal 200 sent from the control circuit 11 through the UHF antenna 14 using the power of the power source 18 (step S21).
When the process of step S17 or the process of step S21 is completed, the control circuit 11 repeats the process from step S10.

As described above, in the passive mode, the tag 10 according to the first embodiment is configured so that the connection terminal of the coil of the LF antenna circuit connected to the wireless circuit 13 is wireless in each operation in the activation signal reception process and the response signal transmission process. By switching so as to connect to the connection terminal having the number of turns that matches the impedance of the circuit 13, the power obtained from the tag reader 20 can be used efficiently.
<Embodiment 2>
In the tag 10 according to the first embodiment, it is known in advance that the current consumption of the wireless circuit 13 is greatly different between the activation signal reception process and the response signal transmission process. The embodiment of switching the connection terminal of the LF antenna circuit to be connected has been described.

In the second embodiment, the tag 10b that detects a change in impedance of the wireless circuit 13 and switches the connection terminal of the LF antenna circuit connected to the wireless circuit 13 when operating in the passive mode is described in the first embodiment. The description of the points that are not changed and the points that are not changed will be omitted, and the points that are changed will be described mainly.
<2-1. Configuration>
The difference between the tag 10b and the tag 10 is that, in the tag 10b, as shown in FIG. 7, an impedance measurement circuit 111 is provided between the output terminal of the power feeding circuit 17 and the power switch 19 and the control circuit 11b Instead of the function of controlling the switching of the connection terminal of the coil of the LF antenna circuit during the start signal reception process and the response signal transmission process, the voltage across the resistor R of the impedance measurement circuit 111 is measured, and the operating radio circuit 13 has the function of calculating the impedance of 13 and controlling the switching of the connection terminal of the coil connected to the wireless circuit 13 based on the calculation result of the impedance.

In addition, the storage unit 12b includes a connection terminal ID for specifying each connection terminal provided in the coil of the LF antenna circuit 15 of the tag 10b and the impedance of the LF antenna circuit 15 when the connection terminal is connected to the wireless circuit 13. The difference is that a correspondence table 300 in which values are associated is stored in advance.
FIG. 8 shows the data structure of the correspondence table 300.

The correspondence table 300 includes, as items, a coil connection terminal ID 301 and an impedance value 302 of the LF antenna circuit 15 when the connection terminal is connected to the wireless circuit 13.
In the correspondence table 300 of FIG. 8, the number of turns of the coil of the LF antenna circuit 15 is the connection terminal N1 of the coil having the number of turns matched to the impedance of the wireless circuit 13 at the start signal transmission process, and the response signal transmission process. The connection terminal N2 of the coil having the number of turns of the impedance matched to the impedance of the wireless circuit 13 and the impedance value of the LF antenna circuit 15 when connected by each connection terminal are stored in advance.

  The impedance measurement circuit 111 is a circuit composed of a resistor R having a resistance value R1 (for example, 10Ω (ohms)), and both ends of the resistor R are connected to the radio circuit 13 in order to measure a voltage. Then, the control circuit 11b repeatedly measures the voltage Er1 across the resistor R of the impedance measurement circuit 111. The current Ir1 flowing through the resistor R is a current flowing through the wireless circuit 13, and can be calculated by Ir1 = Er1 / R1.

  Since the wireless circuit 13 operates at a constant voltage Ec, the impedance Zc of the wireless circuit 13 when the current Ir1 flows can be calculated by Zc = Ec / Ir1. That is, the impedance Zc can be calculated by Zc = Ec / Er1 × R1. Since the values of Ec and R1 are known in advance at the time of designing the tag 10b, the impedance Zc of the operating radio circuit 13 can be calculated by measuring the voltage Er1.

  While the power is supplied from the power supply circuit 17, the control circuit 11b repeatedly measures the voltage across the resistor R (for example, every 2 milliseconds), and calculates the impedance Zc based on the voltage value. Next, the impedance Zc and the impedance value of the correspondence table 300 of the storage unit 12b are compared, the connection terminal of the coil corresponding to the closest impedance value is selected, and switching is performed so that the selected connection terminal is connected to the wireless circuit 13. The instrument 16 is instructed. The switch 16 switches to the connection terminal instructed by the control circuit 11b.

In this way, by repeatedly measuring the impedance of the wireless circuit 13 in operation, the LF antenna circuit is connected to the connection terminal of the number of turns of the coil that becomes an LF antenna circuit having an impedance matched to the impedance of the wireless circuit 13 during each operation. 15 and the radio circuit 13 can be connected.
<2-2. Operation>
FIG. 9 shows a flowchart of signal transmission / reception processing of the control circuit 11b.

The control circuit 11b performs connection terminal switching processing of the coil of the LF antenna circuit, which will be described later, by interrupt processing while executing the processing of step S31, step S35, and step S36 in the passive mode, and connects to the wireless circuit 13. Switch the coil connection terminal.
The tag reader 20 continuously transmits the activation signal 100 and a carrier wave for supplying power repeatedly (for example, every 500 milliseconds). The control circuit 11b receives the activation signal 100 from the tag reader 20, and acquires the values of the reader ID 103 and the flag 104 of the activation signal 100 (step S31).

Next, it is determined whether or not the received activation signal 100 is a passive mode activation signal (step S32). Specifically, when the value of the flag 104 of the received activation signal 100 is “1”, it is determined that the activation signal is a passive mode activation signal (step S32: YES).
In the case of YES in step S32, the control circuit 11b disconnects the power supply 18 from the wireless circuit 13 and disconnects the wireless circuit 13 and the wireless circuit 13 when the wireless circuit 13 and the power feeding circuit 17 are not connected (step S33: NO). An instruction to connect the power feeding circuit 17 is sent to the power switch 19. The power switch 19 disconnects the wireless circuit 13 and the power supply 18 according to the instruction of the control circuit 11, and connects the power supply circuit 17 and the wireless circuit 13 (step S34). If YES in step S33, the wireless circuit 13 and the power feeding circuit 17 are connected, and the tag 10b is in a state of operating in the passive mode, so that the circuit for supplying power to the wireless circuit 13 is switched. Is not necessary.

If YES in step S33 or if the processing in step S34 is completed, the control circuit 11b reads the reader ID obtained from the information of the reader ID 103 included in the activation signal 100, and the tag ID of the own device obtained from the storage unit 12b. Is generated and sent to the radio circuit 13 (step S35).
The radio circuit 13 transmits the response signal 200 sent from the control circuit 11b via the UHF antenna 14 (step S36).

  On the other hand, when the activation signal 100 is not the activation signal in the passive mode (step S32: NO), that is, in the case of the activation signal in the active mode, the control circuit 11b does not connect the wireless circuit 13 and the power source 18 (step S32). S37: NO), the power supply circuit 17 is disconnected from the wireless circuit 13, and an instruction to connect the wireless circuit 13 and the power supply 18 is sent to the power supply switch 19. The power switch 19 disconnects the power feeding circuit 17 from the wireless circuit 13 and connects the wireless circuit 13 and the power supply 18 in accordance with the instruction from the control circuit 11b (step S38). If YES in step S37, the wireless circuit 13 and the power source 18 are connected, and the tag 10b is in the active mode, so that switching of the circuit for supplying power to the wireless circuit 13 is necessary. Absent.

Next, the control circuit 11b generates a response signal 200 in the same procedure as in step S35, and sends it to the radio circuit 13 (step S39).
The radio circuit 13 transmits the response signal 200 sent from the control circuit 11b using the power of the power source 18 via the UHF antenna 14 (step S40).
When the process of step S36 or the process of step S40 is completed, the control circuit 11b repeats the process from step S31.

Next, when the tag 10b is executing the processing of step S31, step S35, and step S36 in the passive mode, the impedance of the coil of the LF antenna circuit that has an impedance that matches the impedance of the wireless circuit 13 that is operating by the interrupt processing. Processing for switching connection terminals will be described.
FIG. 10 shows a flowchart of the coil connection terminal switching process of the LF antenna circuit 15 of the control circuit 11b.

  When the tag 10 b is held over the tag reader 20, an electromotive force is generated in the LF antenna circuit 15 of the tag 10 b, and a current converted into a constant voltage direct current flows through the resistor R of the impedance measurement circuit 111. The control circuit 11b measures the voltage Er1 across the resistor R of the impedance measurement circuit 111 (step S41), and calculates the impedance Zc using the formula Zc = Ec / Er1 × R1 (step S42).

  The control circuit 11b compares the impedance value 302 corresponding to each connection terminal ID 301 of the correspondence table 300 stored in advance in the storage unit 12b with the value of the impedance Zc (step S43). Specifically, the control circuit 11b calculates the absolute value of the difference between the impedance value 302 corresponding to each connection terminal ID301 and Zc, and connects the connection terminal ID having the smallest impedance value. The terminal is selected as a connection terminal to be connected to the wireless circuit 13. The control circuit 11 b sends an instruction to connect the connection terminal of the selected connection terminal ID and the wireless circuit 13 to the switch 16. The switch 16 connects the connection terminal selected by the control circuit 11b and the radio circuit 13 (step S44).

When the process of step S44 is completed, the control circuit 11b repeats the process from step S41.
As described above, the tag 10b according to the second embodiment measures the impedance of the wireless circuit while executing each process by repeatedly interrupting the connection terminal switching process, and based on the measurement result, the wireless circuit The connection terminal of the coil of the LF antenna circuit 15 connected to the connection terminal 13 can be switched to a connection terminal that matches the impedance of the operating radio circuit 13.

<Modification>
The tag according to the present invention has been described above based on the embodiment. However, the tag can be modified as follows, and the present invention is not limited to the tag as described in the above embodiment. Of course.
(1) In Embodiments 1 and 2, the coil of the LF antenna circuit is a coil with a ferrite core having a length of 20 mm, a diameter of 11.3 mm, a winding number of 66 and a magnetic permeability of 25 H / m. Absent.

What is necessary is just to determine the magnitude | size of a coil, the number of turns, etc. so that the impedance of LF antenna circuit may become the impedance which matches the impedance of a radio | wireless circuit.
(2) In the first and second embodiments, the coil of the LF antenna circuit is described as a configuration in which one winding coil is used and a connection terminal is provided in the middle of the coil. However, the coil of the LF antenna circuit 15 has one winding. There is no need to use coils.

For example, as shown in FIG. 11, the coil of the LF antenna circuit 15c of the tag 10c has a configuration in which a plurality of chip coils are aligned and connected in series. And the connection terminal for connecting with the radio | wireless circuit 13 between the both ends of the connected chip coil and a chip coil is provided, and it connects with the radio | wireless circuit 13 with the connection terminal provided between the both ends or one end of the chip coil, and the chip coil. . Thus, the LF antenna circuit can be reduced in size by using the chip coil, and the connection terminal can be easily provided between the chip coil and the chip coil.
(3) In the first and second embodiments, the transmission cycle of the tag reader activation signal is set every 500 milliseconds, but the present invention is not limited to this.

The transmission period of the activation signal may be an interval equal to or longer than the time required for the transmission process of the activation signal and the time necessary for the transmission process of the response signal.
(4) In the first embodiment, as illustrated in FIG. 3, the tag reader 20 has been described as repeatedly performing continuous transmission of an activation signal and a carrier wave for supplying power. However, it is not essential to continuously transmit the activation signal and the carrier wave for supplying power, and it is sufficient to transmit the carrier wave for supplying power after transmitting the activation signal. That is, there may be some time between the transmission of the activation signal and the transmission of the carrier wave for supplying power.

Further, in the first embodiment, as illustrated in FIG. 3, an example has been described in which transmission of a response signal to an activation signal received immediately before reception is started at a timing when the tag 10 receives a carrier wave for power supply. However, the transmission start timing of the response signal can be changed as appropriate according to the capacitance of the capacitor C1 of the power supply circuit 17, for example, the response signal for the activation signal received immediately before reception of the carrier wave for power supply is completed. May be started.
(5) Although the rectifier circuit of the tag power supply circuit of Embodiments 1 and 2 has a configuration of four diode bridge circuits, the present invention is not limited thereto.

Any rectifier circuit may be used as long as it can rectify an alternating current from the LF antenna circuit.
(6) In the first and second embodiments, the example in which the activation signal is received in the LF band and the response signal is transmitted in the UHF band has been described. The LF band is an example of the frequency band for receiving the activation signal, the UHF band is only an example of the frequency band for transmitting the response signal, the reception of the activation signal is not limited to the LF band, and the transmission of the response signal is It is not limited to the UHF band.
However, even when operating in the passive mode, signals may be transmitted and received using the same frequency band as the frequency band used for receiving the activation signal and the frequency band used for transmitting the response signal when the tag operates in the active mode. desirable.

In the first and second embodiments, the tag authentication system has been described as an example. However, the tag according to the present invention may be used in other systems such as a location management system.
In the first and second embodiments, the case where entrance / exit is managed for one door has been described as an example. However, for example, the present invention is applied to the case where entrance / exit of a plurality of doors is managed. be able to. In this case, one control unit may perform authentication related to each door, or a plurality of control units may share authentication related to each door.
(7) In the tag according to the second embodiment, the impedance of the wireless circuit is calculated and the connection terminal of the coil connected to the wireless circuit is switched. However, the present invention is not limited to this.

For example, in the tag according to Embodiment 2, since the operating voltage of the wireless circuit is constant, the impedance of the wireless circuit is inversely proportional to the current flowing through the wireless circuit. The current flowing through the wireless circuit is the current flowing through the resistance of the impedance measuring circuit, and is proportional to the voltage across the resistor. As a result, the impedance change can be detected by the voltage across the resistor of the impedance measurement circuit or the change in the current flowing through the resistor, so the connection terminal of the coil connected to the radio circuit based on the change of any one of these values can be detected. It may be switched.
(8) In the tags of the first and second embodiments, two connection terminals are described. However, the number of connection terminals to be switched is not limited to two.

Since the description has been made on the assumption that the impedance of the radio circuit greatly changes during the reception signal reception processing and the response signal transmission processing, two connection terminals are switched. However, when the impedance of the radio circuit changes greatly in processing performed from reception of the activation signal to completion of transmission of the response signal (for example, processing for extracting data included in the activation signal or processing for generating response signal data) If there are a plurality of connection terminals, a plurality of connection terminals are provided in the middle of the coil so that they can be connected with the number of turns of the coil that becomes an LF antenna circuit having an impedance matching the input impedance viewed from the power supply side when performing each processing. Alternatively, two connection terminals among a plurality of connection terminals including both ends of the coil may be selected and connected to the radio circuit.
(9) A part or all of the modifications (1) to (8) may be combined and applied to the tag according to the embodiment.
<Supplement>
Hereinafter, the configuration of the tag according to the embodiment of the present invention, its modification examples, and each effect will be described.
(A) A tag according to an embodiment of the present invention is a tag that generates electric power for driving a radio circuit from an electromotive force induced in the antenna circuit by radio waves, and the antenna circuit includes an antenna coil, and the radio circuit When the activation signal is received, the first drive power is generated from the first electromotive force induced in the entire antenna coil. When the wireless circuit performs the response signal transmission process, a part of the antenna coil is generated. Second drive power is generated from the induced second electromotive force.

In the tag of this configuration, the antenna circuit operates with the electric power generated by the radio wave from the tag reader, and when the activation signal is received, the radio circuit is operated with the electric power generated over the entire length of the antenna coil, and the response signal In the transmission process, the wireless circuit can be operated with power generated in a part of the antenna coil. That is, the tag having this configuration can generate power in the antenna circuit and operate the radio circuit in a state where the impedance of the antenna coil is different in each of the above processes.
Therefore, power can be generated by the antenna circuit having an impedance that can be efficiently used by the radio circuit from the power from the radio wave from the tag reader.
(B) Further, the impedance determined by the whole antenna coil is a first impedance that matches the input impedance seen from the power supply side in the reception process when viewed from the wireless circuit, and the first electromotive force corresponds to the first impedance. This is an electromotive force, and the impedance that is determined by a part of the antenna coil is a second impedance that matches the input impedance viewed from the power supply side in the transmission process, and the second electromotive force depends on the second impedance. The electromotive force may be changed.

  In the tag of this configuration, the impedance determined by the whole antenna coil can be set to an impedance that matches the input impedance of the wireless circuit viewed from the power supply side during reception processing. Further, the impedance determined by a part of the antenna coil can be set to an impedance that matches the input impedance of the wireless circuit viewed from the power supply side during transmission processing.

Therefore, the electric power from the radio wave from the tag reader can be efficiently supplied to the wireless circuit during each process in the wireless circuit.
(C) In addition, a connection terminal is provided at a position where a part of the antenna coil is formed starting from one end of the antenna coil, and the antenna circuit is connected to the other end of the antenna coil and the radio circuit when performing transmission processing. You may make it switch from the connected state to the state in which a connection terminal and a radio circuit are connected.

The tag of this configuration is a wireless circuit with a connection terminal in which when the response signal is transmitted from the UHF antenna, the impedance of the antenna coil becomes an impedance that matches the input impedance viewed from the power supply side in the transmission process. Can be switched to connect.
Therefore, when the response signal transmission process is executed, the electric power from the radio wave from the tag reader can be efficiently supplied to the wireless circuit.
(D) The antenna circuit may be switched from the state in which the connection terminal and the radio circuit are connected to the state in which the other end of the antenna coil and the radio circuit are connected at the end of the transmission process. Good.

The tag of this configuration can be switched so that the impedance of the antenna coil matches the input impedance seen from the power supply side in the reception process when the response signal transmission process is completed. .
Therefore, the power from the radio wave from the tag reader can be efficiently supplied to the wireless circuit during the reception process of the activation signal.
(E) The antenna coil is formed by connecting N (N> 0) chip coils in series, and the first electromotive force is an electromotive force induced in the N chip coils, and the second electromotive force. The electric power may be an electromotive force induced in M (N>M> 0) continuous chip coils among the N chip coils.

The tag having this configuration can be configured such that a plurality of chip coils are connected in series to a coil of an antenna circuit. Therefore, the antenna circuit can be downsized, and the connection terminals can be easily provided between the chip coils.
(F) The radio wave received by the antenna circuit is an LF band radio wave, and the response signal may be transmitted in the UHF band.

The tag having this configuration can receive an activation signal transmitted in the LF band and transmit a response signal in the UHF band. Therefore, the tag having this configuration can perform the same operation as in the active mode even in the passive mode.
(G) A tag according to an embodiment of the present invention is a tag that generates power for driving a wireless circuit from an electromotive force induced in the antenna circuit by radio waves, includes an antenna coil, and the wireless circuit is activated. During the signal reception process, a first electromotive force is generated that is induced in the entire antenna coil, and when the wireless circuit is in the response signal transmission process, the second electromotive force is induced in a part of the antenna coil. An antenna circuit to be generated, and an impedance measurement unit that repeatedly measures an input impedance of the radio circuit viewed from the power supply side during operation of the radio circuit. The antenna circuit is based on a measurement result of the impedance measurement unit. Driving power for receiving a start signal by performing either switching from generation of electromotive force to generation of second electromotive force or switching from generation of second electromotive force to generation of first electromotive force Generated from the first electromotive force, driving power for transmitting a response signal is generated from the second electromotive force.

  In the tag of this configuration, the antenna circuit operates with the electric power induced by the radio wave from the tag reader, and the change of the input impedance viewed from the power supply side when viewed from the wireless circuit can be repeatedly measured during the operation of the wireless circuit. And according to the change of the impedance, it can switch so that it may become an antenna circuit of the impedance most matched with the input impedance which looked at the radio | wireless circuit from the electric power supply side.

  Therefore, even when the impedance of the operating wireless circuit changes, the electric power from the radio wave from the tag reader can be efficiently supplied to the wireless circuit.

DESCRIPTION OF SYMBOLS 1 Tag authentication system 10, 10b, 10c Tag 11 Control circuit 12 Memory | storage part 13 Wireless circuit 14, 24 UHF antenna 15 LF antenna circuit 16 Switch 17 Power feeding circuit 19 Power switch 21 Control unit 22 LF transmission unit 23 UHF reception circuit

Claims (7)

A tag that generates power for driving a radio circuit from an electromotive force induced in an antenna circuit by radio waves,
The antenna circuit includes an antenna coil, and when the wireless circuit performs reception processing of the activation signal, the antenna circuit generates first driving power from the first electromotive force induced in the entire antenna coil, and the wireless circuit responds. In the signal transmission process, the second drive power is generated from the second electromotive force induced in a part of the antenna coil. The impedance determined by the entire antenna coil is a first impedance that matches the input impedance seen from the wireless circuit from the power supply side during the reception process,
The first electromotive force is an electromotive force according to the first impedance,
The impedance determined by a part of the antenna coil is a second impedance that matches the input impedance seen from the wireless circuit from the power supply side during the transmission process,
The tag according to claim 1, wherein the second electromotive force is an electromotive force corresponding to the second impedance. A connection terminal is provided at a position where a part of the antenna coil is formed starting from one end of the antenna coil,
The antenna circuit switches from a state in which the other end of the antenna coil and the wireless circuit are connected to a state in which the connection terminal and the wireless circuit are connected when the transmission process is executed. The tag according to claim 2, wherein the tag is characterized. The antenna circuit switches from a state in which the connection terminal and the wireless circuit are connected to a state in which the other end of the antenna coil and the wireless circuit are connected when the transmission process is completed. The tag according to claim 3 The antenna coil is formed by connecting N (N> 0) chip coils in series.
The first electromotive force is an electromotive force induced in N chip coils, and the second electromotive force is generated in M (N>M> 0) continuous chip coils among the N chip coils. The tag according to claim 1, wherein the tag is an induced electromotive force. The tag according to claim 1, wherein the radio wave received by the antenna circuit is an LF band radio wave, and the response signal is transmitted in the UHF band. A tag that generates power for driving a radio circuit from an electromotive force induced in an antenna circuit by radio waves,
Including an antenna coil, the wireless circuit generates a first electromotive force induced in the whole antenna coil when the activation signal is received, and the wireless circuit transmits the response signal when the response signal is transmitted. An antenna circuit for generating a second electromotive force induced in a part of the antenna coil;
An impedance measuring unit that repeatedly measures the input impedance of the wireless circuit viewed from the power supply side during operation of the wireless circuit;
The antenna circuit switches from the generation of the first electromotive force to the generation of the second electromotive force, and the generation of the first electromotive force from the generation of the second electromotive force based on the measurement result of the impedance measuring unit. Switch to
The drive power for receiving the activation signal is generated from the first electromotive force, and the drive power for transmitting the response signal is generated from the second electromotive force.

Images