JP2009064315A - Rf tag system, rf tag, and tag reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an RF tag system capable of setting flexibly a communication distance, without requiring labors and times for management for battery replacement or the like. <P>SOLUTION: In this RF tag system, an RF tag is provided with an electric power source generating part for generating an own operation electric power source from a carrier transmitted by a reader writer, and an electric power source accumulating part for accumulating operation electric power source power, and an operation mode is constituted executably with a passive mode operated by the electric power source supplied from the electric power source generating part, and for responding by backscattering system, and an active mode operated by the electric power source supplied from the electric power source accumulating part, and for modulating the carrier transmitted by own-self to conduct a response. The Rf tag transmits spontaneously the response at a period T1 when an operation is started by the active mode, and when the reader writer shuts off the carrier, switches a period Ta operated by the active mode and waiting a command transmission to a period Tp operated by the passive mode and waiting a command transmission, and vice versa, and conducts communication at the operation mode when receiving the command, when receiving the selected command from the reader writer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an RF tag system in which a tag reader and an RF tag communicate using electromagnetic waves, and an RF tag and a tag reader used in the system.

  Patent Document 1 includes a function of an RF tag having a general configuration (passive mode) that operates by being powered by a carrier transmitted from a reader / writer, and that modulates the carrier and returns a response. A hybrid tag corresponding to the ZigBee (registered trademark) standard used for communication) and configured as a ZigBee slave is disclosed. In the tag configured in this way, when a communication distance with a reader / writer is long and a response cannot be returned in the passive mode, a technology is disclosed in which a response is received in the active mode upon receiving power from the ZigBee slave.

Patent Document 2 discloses a technique in which a battery is built in a data carrier, and when response in passive mode is difficult as in Patent Document 1, power is supplied from the battery and response is returned in active mode. Has been.
Utility Model Registration No. 3128697 JP-A-11-131844

However, all of these technologies have a problem that, when the battery is exhausted, the communicable distance is eventually reduced, so it is necessary to replace the battery at an appropriate timing, and management is troublesome.
The present invention has been made in view of the above circumstances, and an object of the present invention is to use an RF tag system capable of more flexibly setting a communication distance without requiring troublesome management such as battery replacement and the system. An RF tag and a tag reader are provided.

  According to the RF tag system of claim 1, the RF tag includes a power generation unit that generates its own operation power source from electromagnetic waves transmitted from the tag reader, and a power storage unit that stores the operation power source power. As an operation mode, a passive mode that operates with the power supplied from the power generation unit and responds by the backscatter method, and a response that operates by the power supplied from the power storage unit and modulates the electromagnetic wave transmitted by itself It is possible to execute the active mode in which That is, the RF tag can select the passive mode and the active mode according to the power storage state of the power storage unit, and when the active mode is selected, the communication distance with the tag reader can be extended, and the communication is more stable. Can be done in the state.

  The operation state on the tag reader side includes a power supply period, a command transmission period, a carrier transmission period, and a carrier stop period. If the RF tag can operate in the operation mode specified by the tag reader, the operation mode When the tag reader receives a response from the RF tag, the tag reader performs communication by specifying the unique ID and the operation mode for the detected RF tag. Therefore, regardless of whether the RF tag side is operating in the active or passive mode, the tag reader can perform communication in the same procedure, and switching of the communication procedure according to the operation mode can be made unnecessary.

  According to the RF tag system of the second aspect, the tag reader repeats a control cycle composed of a power transmission period and a carrier stop period, and the RF tag is in a state capable of operating in the active mode and from the tag reader. If there is no command transmission, the tag reader spontaneously transmits its own unique ID information and information indicating the amount of accumulated power during the carrier stop period of the tag reader. When the tag reader receives a response from the RF tag, Communication is performed by specifying a unique ID and an operation mode.

  That is, the conventional RF tag does not voluntarily notify the tag reader of its own state. Therefore, in order to check whether the RF tag can operate in the active mode, the tag reader periodically issues a command. I had to send it and judge from the response. On the other hand, according to the configuration of claim 2, since the RF tag spontaneously transmits a response during the carrier stop period of the tag reader, the tag reader does not need to periodically detect the RF tag. Therefore, the detection process can be simplified and the processing speed can be increased.

  According to the RF tag system of the third aspect, when the RF tag voluntarily transmits to the tag reader, the RF tag operates in the active mode for a predetermined period and waits for the command transmission from the tag reader. If there is a command transmission, the RF tag continues in the active mode. Operate. On the other hand, when there is no command transmission, it operates in the passive mode if it can be operated, and shifts to the sleep mode if the operation in the passive mode is impossible. Then, after detecting the transmission of the carrier by the tag reader, the tag reader transmits again spontaneously when the tag reader shifts to the carrier stop period.

  That is, if the RF tag is continuously operated in the active mode, the power is consumed and the operation time is shortened. In addition, when the passive mode and the active mode are used together, it is necessary to switch between the two. . On the other hand, according to the configuration of claim 3, after the RF tag spontaneously transmits a response in the active mode, if there is no command transmission from the tag reader, the mode automatically shifts to the passive mode or the sleep mode. If the detection is stopped, the response transmission is repeated spontaneously, so that the power consumption of the power storage unit can be suppressed and the operation time can be extended. The “pause mode” is a mode in which only the tag reader carrier is detected by the power of the power storage unit when the power storage unit has a small amount of power and cannot operate in the passive mode.

According to the RF tag of the fourth aspect, the same effect as the RF tag in the system of the third aspect can be obtained.
According to the tag reader of claim 5, the same effect as the tag reader in the system of claim 1 can be obtained.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a functional block diagram showing the configuration of the RF tag. When the RF tag 1 receives the carrier (electromagnetic wave) transmitted from the reader / writer (tag reader) 2 by the antenna 3, the RF tag 1 smoothes the carrier in the power generation unit 4 to generate an operation power source. The power supply for operation is supplied to a power storage unit (power storage unit) 5 constituted by, for example, an electric double layer capacitor or a secondary battery, and power is stored (charged). Note that the RF tag 1 is configured in a size corresponding to the capacity of the power storage unit 5 so that the power stored in the power storage unit 5 can be operated, for example, about several minutes to several tens of minutes.

  The power output from the power generation unit 4 and the power storage unit 5 is supplied as an operation source power source for the RF tag 1 through the power selection unit 6. The power supply voltages V1 and V2 output from the power generation unit 4 and the power storage unit 5 are detected by a voltage detection unit (accumulation amount detection unit) 7, and the detection result is given to the control unit 8. That is, the amount of power stored in the power storage unit 5 can be detected from the terminal voltage level of the capacitor or the secondary battery. The control unit 8 is configured by a CPU or a microcomputer, and outputs a power supply selection signal to the power supply selection unit 6 in accordance with the power supply voltage detected by the voltage detection unit 7.

Also, the transmission signal from the reader / writer 2 received via the antenna 3 is demodulated by the demodulator 9 and the received data is output to the controller 8. The control unit 8 returns response data for the command included in the received data. When the response data is modulated via the response selection unit (response method selection unit) 10 and the modulation unit 11, the antenna 3 Is sent back to the reader / writer 2 side. The modulation unit 11 includes an active modulation unit 11A and a passive modulation unit 11P.
The passive modulation unit 11P executes a modulation method adopted by a general RF tag, and modulates a carrier transmitted from the reader / writer 2 by a backscatter method (load modulation method). On the other hand, the active modulation unit 11A internally oscillates and outputs a frequency signal (electromagnetic wave) corresponding to the carrier, and modulates (amplitude modulation) the frequency signal by, for example, an ASK (Amplitude Shift Keying) method.

  Here, FIG. 2A shows a schematic circuit image of the passive modulation unit 11P. In the backscatter method, the impedance of the antenna 3 is changed by turning on and off the switch according to the response data, and the amplitude is modulated by reflecting the carrier. FIG. 2B shows the waveform of the carrier that the reader / writer (RW) 2 transmits to the RF tag 1, and FIG. 2C shows the response data waveform that the RF tag 1 sends back to the reader / writer 2.

  FIG. 3A shows a schematic circuit image of the active modulation unit 11A. The modulated signal obtained by ASK modulation of the carrier by the active modulation unit 11A (the modulation unit is not shown) is amplified by an amplifier and transmitted from the antenna 3. FIG. 3B shows a carrier waveform transmitted from the reader / writer 2 to the RF tag 1. When the reader / writer 2 transmits a command, the carrier writer 2 stops the output of the carrier in order to receive a response from the RF tag 1. FIG. 3C shows a response signal waveform (ASK modulated wave) returned from the RF tag 1 to the reader / writer 2.

  FIG. 7 shows a response data waveform when the passive mode and the active mode are both achieved. As shown in FIG. 7A, the reader / writer 2 transmits a non-modulated carrier to the RF tag 1 after passing through a charging period (power supply period) in which the RF tag 1 is charged with operating power supply power. Send a command (command transmission period). The command is a signal that can be received in either the passive mode, the active mode, or both. If the operation mode when the command from the reader / writer 2 is received is the passive mode, the RF tag 1 returns a response to the reader / writer 2 in the passive response period (carrier transmission period) after receiving the command (FIG. 7 ( If the operation mode when the command is received is the active mode, a response is returned to the reader / writer 2 during the active response period (carrier stop period) in which the carrier transmission from the reader / writer 2 is stopped (see FIG. (Refer FIG.7 (c)).

  Refer to FIG. 1 again. Which modulation unit 11A, 11P modulates the response data output from the control unit 8 is determined by a modulation method selection signal output from the control unit 8 to the response selection unit 10. The response selection unit 10 is a demultiplexer, and outputs response data to one of the modulation units 11A and 11P according to the selection signal. The control unit 8 writes and stores necessary data in the nonvolatile memory 12.

Here, the operation mode of the RF tag 1 has the following three types depending on the combination of the power source to be used and the modulation method.
(1) Passive mode This is a mode that operates in the same way as a general RF tag, operates with the power supplied from the power generation unit 4, and performs load modulation on the carrier transmitted from the reader / writer 2 by the passive modulation unit 11P. Respond.
(2) Active mode It operates with the power supplied from the power storage unit 5, and responds by modulating (for example, ASK modulation) the carrier transmitted by the active modulation unit 11A.
(3) Semi-passive mode Although it operates with the power supplied from the power storage part 5, when returning a response signal to the reader / writer 2, the passive modulation part 11P is used like the passive mode of (1).

  FIG. 4 is a functional block diagram showing the configuration of the reader / writer 2. The configuration is almost the same as a general configuration. The control unit 13 is composed of a CPU or a microcomputer, and has a built-in memory 14, a timer 15, and the like, and communicates with a host device (host) 16. The control unit 13 communicates with the RF tag 1 through the transmission unit 17, the antenna 18, and the reception unit 19 in response to a trigger given from the higher-level device 16, and transmits the communication result to the higher-level device 16 side.

The transmission unit 17 includes a coding unit 20, a modulation unit 21, and an amplification unit 22. The encoding unit 20 encodes transmission data output from the control unit 13 by a predetermined encoding method, and the modulation unit 21 performs, for example, ASK modulation of the carrier based on the encoded data. The amplifying unit 22 amplifies the modulated signal and outputs the amplified signal to the antenna 18.
On the other hand, the reception unit 19 includes a demodulation unit 23, a decoding unit 24, and a carrier sense unit 25. The demodulator 23 demodulates the response signal from the RF tag 1 received by the antenna 18, and the decoder 24 decodes the response data from the demodulated signal and outputs the response data to the controller 13. Further, the carrier sense unit 25 detects whether or not another reader / writer is outputting a carrier for communication, and detects the carrier frequency and outputs it to the control unit 13.

  FIG. 5A shows a frame structure of data transmitted from the reader / writer 2 to the RF tag 1, and (1) and (2) are included when information specifying the ID of the RF tag 1 is not included. Each case is shown. The transmission frame is composed of “header”, in the case of (2), “tag ID”, “operation mode”, “command”, and “EDC (Error Detection Code)”. The “header” is information indicating a transmission frame, and the “operation mode” is information for designating any one of the modes (1) to (3). “Command” is information of a command transmitted by the reader / writer 2, and “EDC” is a code added for error check such as CRC (Cyclic Redundancy Check).

  FIG. 5B shows a frame structure of response data returned from the RF tag 1 to the reader / writer 2, which is composed of “header”, “tag ID”, “tag power”, “status”, and “EDC”. Yes. “Header” is information indicating a response frame, and “Tag ID” is ID information of the RF tag 1. “Tag power” is information indicating the terminal voltage V 2 of the power storage unit 5 detected by the voltage detection unit 7, and “Status” is information indicating the execution result of the command transmitted by the reader / writer 2.

  Next, the operation of the present embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing only the part related to the gist of the present invention, as the processing contents executed by the control unit 8 of the RF tag 1. The RF tag 1 operates in a passive mode by default. Upon receiving the command transmitted from the reader / writer 2 (step S1), the control unit 8 determines whether the response method specified by the “operation mode” of the transmission frame is active, semi-passive, or passive. (Steps S2, S3).

  When the designated method is passive (step S3: YES), it is determined whether or not the power supply voltage V1 of the power supply generation unit 4 detected by the voltage detection unit 7 is equal to or higher than the operable voltage Vp (step S4). ). If V1 ≧ Vp (YES), the control unit 8 selects the power source V1 of the power generation unit 4 by the power source selection unit 6 (step S5, no change if starting from default), and the response selection unit 10 The passive modulation unit 11p is selected (step S6). Then, response data is transmitted by the backscatter method (step S7). If V1 <Vp in step S4 (NO), the process is terminated without making a response to the reader / writer 2.

On the other hand, when the designated method is active or semi-passive (step S2: YES), whether or not the power supply voltage V2 of the power storage unit 5 detected by the voltage detection unit 7 is equal to or higher than the operable voltage Va. Is determined (step S8). If V2 ≧ Va (YES), the control unit 8 selects the power source V2 of the power storage unit 5 by the power source selection unit 6 (step S9), and selects the active modulation unit 11a by the response selection unit 10 (step S10). ). Then, the process proceeds to step S7, where the internally generated carrier is ASK modulated and response data is transmitted. If V2 <Va in step S8 (NO), no response is made to the reader / writer 2 and the process is terminated.
In step S9a, if the specified method is semi-passive, “NO” is determined, and the process proceeds to step S6. In this case, the power source V2 of the power storage unit 5 is selected as the power source for operation of the RF tag 1, and the passive modulation is selected as the response method.

  As described above, according to the present embodiment, the RF tag 1 has the power generation unit 4 that generates its own power supply for operation from the carrier transmitted from the reader / writer 2, and the power storage unit 5 that stores the power supply power. The operation mode includes a passive mode that operates with the power supplied from the power generation unit 4 and responds in a backscatter manner, and a carrier that operates with the power supplied from the power storage unit 5 and transmits itself. An active mode that modulates and responds is configured to be executable.

  When receiving a command specifying the response method transmitted by the reader / writer 2, the RF tag 1 sends a response signal according to the method if the response method specified based on the power storage amount of the power storage unit 5 can be executed. In response, the tag ID of the RF tag 1 and the information indicating the power storage amount are returned in response to the response signal. Therefore, the RF tag 1 can select the passive mode and the active mode according to the power storage state of the power storage unit 5, and when the active mode is selected, the communication distance with the reader / writer 2 can be extended. Communication can be performed in a more stable state. Further, the reader / writer 2 grasps the power storage state of the power storage unit 5 based on the response from the RF tag 1 and can determine which one of the subsequent response methods is designated according to the state.

  Further, the RF tag 1 can operate in the semi-passive mode in which the power selection unit 6 selects the power storage unit 5 and the response method selection unit 10 selects the passive modulation unit 11P as the operation mode. Can also extend the communication distance. And since the electric power accumulate | stored in the power storage part 5 is not consumed when returning a response to the reader / writer 2, operation time can be made longer.

  The operation state of the reader / writer 2 includes a charging period, a command transmission period, a passive response period, and an active response period. If the RF tag 1 can operate in the operation mode specified by the reader / writer 2. In response to the response period of the operation mode, when the reader / writer 2 receives a response from the RF tag 1, the reader / writer 2 communicates with the detected RF tag 1 by designating a unique ID and an operation mode. Therefore, regardless of whether the RF tag 1 is operating in the active or passive mode, the reader / writer 2 can perform communication in the same procedure, and it is not necessary to switch the communication procedure according to the operation mode. Can do.

(Second embodiment)
8 and 9 show a second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted. Hereinafter, different parts will be described. In the first embodiment, the basic operation mode of the RF tag 1 is shown. In the second embodiment, power is sufficiently stored in the power storage unit 5 of the RF tag 1 so that it can operate in the active mode. In such a case, the RF tag 1 is controlled to switch the operation mode spontaneously.

  FIG. 8 shows (a) the procedure of communication performed with the reader / writer 2 when the RF tag 1 is operable in the active mode, and (b) the switching state of the operation mode of the RF tag 1. It is shown. As shown in FIG. 8B, the RF tag 1 responds spontaneously to the reader / writer 2 every predetermined period T1 when the reader / writer 2 turns off the carrier and receives a tag response in the active mode (see FIG. 8B). 5 (b)) is transmitted. In the period T1, the period Ta operates in the active mode, and the subsequent period Tp operates in the passive mode.

  The reader / writer 2 turns off the carrier after a predetermined period T1, and the RF tag 1 starts the operation in the active mode when detecting the carrier OFF. When the reader / writer 2 receives a response spontaneously returned by the RF tag 1 every predetermined period T1, as shown in FIG. 8A, the reader / writer 2 thereafter responds in the same manner as in normal communication. A request for selecting the received RF tag 1 is transmitted. When the RF tag 1 returns a response to the selection request, the RF tag 1 continues to operate in the active mode.

  On the other hand, as shown in FIG. 9, the reader / writer 2 transmits the first request while the RF tag 1 is operating in the passive mode, and the RF tag 1 returns a response to the request, followed by the selection request and selection. When a response is exchanged, the RF tag 1 operates in the passive mode until the reader / writer 2 turns off the carrier.

  That is, if the RF tag 1 is operated in the active mode, the power of the power storage unit 5 is consumed. Therefore, if the operation in the active mode is continued, the operation time is shortened. On the other hand, the reader / writer 2 needs to periodically transmit a command to check whether there is an RF tag that can communicate in the active mode. Therefore, when the RF tag 1 becomes operable in the active mode, the reader / writer 2 can easily detect the RF tag 1 by spontaneously transmitting unique ID information or the like to the reader / writer 2. To. Moreover, the power consumption of the power storage unit 5 is suppressed by switching between the active mode and the passive mode.

  In the case of FIG. 9, after the RF tag 1 spontaneously transmits a response in the active mode, if there is no command transmission from the reader / writer 2 and the operation in the passive mode is impossible, the RF tag 1 is in the sleep mode. Migrate to The “pause mode” is a mode in which only carrier detection is performed on the power of the power storage unit 5 when the power storage unit 5 has a small amount of power and cannot operate in the passive mode.

  As described above, according to the second embodiment, the reader / writer 2 repeats the control cycle T1 including the charging period and the active response period, and the RF tag 1 is in a state in which the operation in the active mode is possible. When there is no command transmission from the reader / writer 2, when the reader / writer 2 receives the response from the RF tag 1, the unique ID information and the information indicating the power storage amount are spontaneously transmitted during the active response period. Then, communication is performed by designating a unique ID and an operation mode for the RF tag 1.

  That is, since the conventional RF tag does not voluntarily notify the reader / writer of its own state, the reader / writer periodically checks whether the RF tag can operate in the active mode. We had to send a command and judge from the response result. On the other hand, according to the configuration of the second embodiment, since the RF tag 1 spontaneously transmits a response during the active response period, the reader / writer 2 needs to periodically detect the RF tag 1. Disappear. Therefore, the detection process can be simplified and the processing speed can be increased.

  Further, when the RF tag 1 spontaneously transmits to the reader / writer 2, it operates in the active mode for a predetermined period, waits for command transmission from the reader / writer 2, and continues to operate in the active mode if there is a command transmission. On the other hand, when there is no command transmission, it operates in the passive mode if it can be operated, and shifts to the sleep mode if the operation in the passive mode is impossible. Thereafter, after detecting the carrier transmission by the reader / writer 2, when the reader / writer 2 shifts to the active response period, the transmission is spontaneously performed again.

  That is, if the RF tag 1 continuously operates in the active mode, the power is consumed and the operation time is shortened. In general, when the passive mode and the active mode are used together, it is necessary to switch between the two. There is. On the other hand, according to the configuration of the second embodiment, after the RF tag 1 spontaneously transmits a response in the active mode, if there is no command transmission, the RF tag 1 automatically shifts to the passive mode or the sleep mode, and the carrier ON → Since the response transmission is repeated spontaneously when the power is turned off, the power consumption of the power storage unit 5 can be suppressed and the operation time can be extended.

The present invention is not limited to the embodiments described above or shown in the drawings, and the following modifications or expansions are possible.
A configuration that operates in the semi-passive mode may be provided as necessary. In the case of not supporting the semi-passive mode, in the flowchart of FIG. 6, it is determined in step S2 only whether or not the mode is active, step S9a is deleted, and step S9 is directly shifted to step S10.
In the communication in the active mode, the modulation method adopted by the RF tag is not limited to the ASK modulation method.

1 is a functional block diagram showing a configuration of an RF tag according to a first embodiment of the present invention. (A) is a schematic circuit image of the passive modulation unit, (b) is a carrier waveform transmitted from the reader / writer to the RF tag, and (c) is a response data waveform returned from the RF tag to the reader / writer. FIG. 2 equivalent diagram corresponding to the active modulation section Functional block diagram showing the configuration of the reader / writer (A) is a frame configuration of data transmitted from the reader / writer to the RF tag, and (b) is a diagram illustrating a frame configuration of response data transmitted from the RF tag to the reader / writer. The flowchart which shows only the part which concerns on the summary of this invention about the processing content performed by the control part of RF tag Diagram showing response data waveform when both passive mode and active mode are compatible FIG. 5A is a second embodiment of the present invention, where FIG. 5A is a diagram illustrating a communication procedure performed between a reader / writer and an RF tag, and FIG. Equivalent to Fig. 8 (when request is received in passive mode)

Explanation of symbols

  In the drawings, 1 is an RF tag, 2 is a reader / writer (tag reader), 3 is an antenna, 4 is a power generation unit, 5 is a power storage unit (power storage unit), 6 is a power source selection unit, and 7 is a voltage detection unit (storage). (Quantity detection unit), 8 is a control unit, 10 is a response selection unit (response method selection unit), 11A is an active modulation unit, 11P is a passive modulation unit, and 12 is a nonvolatile memory.

Claims (5)

In an RF tag system in which a tag reader and an RF tag communicate using electromagnetic waves,
The RF tag includes an antenna that receives an electromagnetic wave transmitted from the tag reader, a power generation unit that generates its own operating power from the electromagnetic wave received by the antenna, and a power storage that stores the operating power. A storage amount detection unit that detects a power storage amount of the power storage unit, a control unit that switches an operation mode according to the power storage amount, the power generation unit and the power storage unit according to the operation mode A power source selection unit that switches whether to use the power source supplied from, a passive modulation unit that returns a response signal by a backscatter method using electromagnetic waves transmitted from the tag reader, and a power storage unit. An active modulation unit that modulates an electromagnetic wave transmitted by the power source and returns a response signal, and the passive modulation unit according to the operation mode And a response method selection unit for selecting one of said active modulator unit,
The operation mode of the RF tag is a passive mode in which the power source selection unit selects the power source generation unit and the response method selection unit selects the passive modulation unit, and the power source selection unit selects the power storage unit. And the response mode selection unit has an active mode for selecting the active modulation unit,
The RF tag receives electromagnetic waves transmitted from the tag reader, accumulates the operating power generated by the power generation unit in the power storage unit, and the generated operating power is at a level that is operable in the passive mode. It becomes possible to operate in the passive mode when it becomes, and it becomes possible to operate in the active mode when the amount of power stored in the power storage unit becomes more than the level that can be operated in the active mode,
The tag reader transmits a power to the RF tag by transmitting the unmodulated carrier, a period for transmitting a command to the RF tag by modulating a carrier, and a response from the RF tag in the passive mode. A carrier transmission period for receiving a response and a carrier stop period for receiving a response from the RF tag in an active mode, and an operation mode of the RF tag is designated by a command to be transmitted,
When the operation in the operation mode specified by the tag reader is possible, the RF tag responds with a response period in the operation mode, and includes information indicating at least its own unique ID in the response data,
When the tag reader receives a response from the RF tag, the tag reader performs communication by specifying a unique ID and an operation mode for the detected RF tag. The tag reader repeats a control cycle composed of the power transmission period and the carrier stop period,
The RF tag has its own unique ID information and the power during the carrier stop period of the tag reader when the stored power amount of the power storage unit is not less than a level at which it can operate in the active mode and no command is transmitted from the tag reader. Voluntarily send information indicating the amount of storage,
2. The RF tag system according to claim 1, wherein when the response from the RF tag is received, the tag reader performs communication by specifying a unique ID and an operation mode for the detected RF tag. When the RF tag spontaneously transmits to the tag reader, the RF tag operates in an active mode for a predetermined period and waits for a command transmission from the tag reader.
If there is no command transmission, it will operate in the passive mode if it can operate in the passive mode, and if it cannot operate in the passive mode, it will enter the sleep mode in which the operation is suspended, and then the carrier will be transmitted by the tag reader. 3. The RF tag system according to claim 2, wherein after detecting that the tag reader has been performed, when the tag reader shifts to the carrier stop period, the tag reader performs transmission again spontaneously. An antenna for receiving electromagnetic waves transmitted from a tag reader;
A power generation unit that generates its own operation power source from electromagnetic waves received by the antenna, a power storage unit that stores the operation power source power, and
A storage amount detection unit for detecting the power storage amount of the power storage unit;
A control unit that switches an operation mode in accordance with the power storage amount;
A power source selection unit that switches between using the power source supplied from the power source generation unit and the power storage unit according to the operation mode;
A passive modulation unit that returns a response signal by a backscatter method using electromagnetic waves transmitted from the tag reader;
An active modulation unit that modulates an electromagnetic wave transmitted by the power source supplied from the power storage unit and returns a response signal;
A response method selection unit that selects either the passive modulation unit or the active modulation unit according to the operation mode;
As the operation mode, the power selection unit selects the power generation unit and the response method selection unit selects the passive modulation unit, and the power selection unit selects the power storage unit and the response. An active mode in which a system selection unit selects the active modulation unit;
When the electromagnetic wave transmitted from the tag reader is received and the operation power generated by the power generation unit is stored in the power storage unit, the generated operation power becomes passive when the level is higher than the level operable in the passive mode. It becomes possible to operate in the active mode when it becomes possible to operate in the mode, and when the amount of power stored in the power storage unit exceeds the level that can be operated in the active mode,
When the operation in the operation mode specified by the tag reader is possible, the response is made in the response period in the operation mode, and the response data includes at least information indicating its own unique ID,
When the stored power amount of the power storage unit is equal to or higher than the level at which the power storage unit can operate in the active mode and no command is transmitted from the tag reader, the unique ID information of the tag reader during the carrier stop period and information indicating the power storage amount And voluntarily send
When it sends to the tag reader spontaneously, it operates in the active mode for a predetermined period and waits for the command transmission from the tag reader. If there is a command transmission, it continues to operate in the active mode,
If there is no command transmission, it operates in passive mode if it can operate in passive mode. After detection, when the tag reader shifts to a carrier stop period, the RF tag performs transmission again spontaneously. In a tag reader that communicates using an electromagnetic wave and an RF tag configured to be able to operate in the active mode using the power supplied from the built-in power storage unit and the operation in the passive mode,
In order to receive a response from the RF tag in a passive mode, a power supply period for transmitting power to the RF tag by transmitting an unmodulated carrier, a period for transmitting a command to the RF tag by modulating a carrier A carrier transmission period and a carrier stop period for receiving a response from the RF tag in the active mode,
When receiving a response from the RF tag, the tag reader performs communication by designating a unique ID and an operation mode for the detected RF tag.

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