JP2009054104A - Rf tag system, rf tag, and tag reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an RF tag system which is capable of more flexibly setting a communication distance without requiring time and labor for management such as battery replacement. <P>SOLUTION: In an RF tag 38, a conduction control part 36 is made conductive when a potential difference between a power source generation part 4 and a power storage part 34 becomes equal to or higher than a prescribed value Vd, and a control part 8 opens a switch 37 connected in parallel to the conduction control part 36 when operating in a passive mode and closes the switch 37 when operating in a charging mode, whereby the power storage part 34 is charged in the passive mode in the case that there is a surplus in the power even when the power consumed in the passive mode is deducted from the power generated by the power source generation part 4, and is preferentially charged in the charging mode. <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 to be used 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 And an active mode in which the power generated by the power generation unit by the received electromagnetic wave is preferentially stored in the power storage unit. When the RF tag receives a command specifying the response method transmitted by the tag reader, the RF tag can execute the specified response method based on the power storage amount of the power storage unit. A response signal including information and information indicating the power storage amount is returned.

  That is, the RF tag can select the “passive”, “active”, or “charge” mode according to the power storage state of the power storage unit, and if the active mode is selected, the communication distance with the tag reader can be extended. Communication can be performed in a more stable state. Further, since the tag reader can grasp the power storage state of the power storage unit based on the response from the RF tag, it can determine which of the subsequent response methods is designated according to the state.

  The RF tag operates in either “passive” or “charge” mode preset by the tag reader until the power storage amount exceeds the operable level of the active mode, and the power storage amount is in the active mode. When it exceeds the operable level, it operates “active”. When operating in “passive” or “active”, the operation mode during power storage is set to either “passive” or “charge” by a command transmitted from the tag reader.

  Therefore, when the power storage amount of the power storage unit tends to be insufficient and the operation in the active mode is difficult, if the RF tag is set to the charge mode, the power is generated by the electromagnetic wave transmitted by the tag reader. Prioritizing charging of the storage unit, the RF tag can reach a state operable in the active mode in a short time.

According to the RF tag system of the second aspect, when the RF tag starts operation in the charging mode and the power storage amount exceeds the operable level of the passive mode, the operation mode is switched to “passive”. If it is operating, information indicating the amount of stored power is returned in response to the tag reader. When the tag reader determines that the power storage amount exceeds the operable level of the active mode when receiving the response, the tag reader transmits a command for switching the operation mode to “active” to the RF tag.
Therefore, when the tag reader determines that the charging of the power storage unit proceeds during the period in which the RF tag is operating in the passive mode, and the power storage amount exceeds the operable level of the active mode due to the response from the RF tag, By switching the operation mode of the RF tag to “active”, the RF tag can be efficiently operated in the active mode.

  According to the RF tag system of the third aspect, when the RF tag operates in the active mode, the operation mode is changed to “passive” by the command transmitted from the tag reader. The operation mode can be switched when it is determined that the operation is unnecessary.

According to the RF tag system of the fourth aspect, in the RF tag, when the potential difference between the power generation unit and the power storage unit becomes equal to or greater than a predetermined value, the conduction control means inserted between the two conducts. The control unit of the RF tag opens the switch means connected in parallel to the conduction control means when operating in the passive mode, and closes the switch means when operating in the charge mode.
In other words, in the passive mode, communication with the tag reader is prioritized over charging to the power storage unit. Therefore, if there is a surplus even if the power consumed in the passive mode is subtracted from the power generated by the power generation unit, The power storage unit is charged via the control means. On the other hand, in the charge mode, the power storage unit can be preferentially charged by closing the switch unit and bypassing the conduction control unit.

  According to the RF tag system of the fifth aspect, since the switch means is configured by a latch type switch capable of maintaining the open / closed state, the next activation can be performed as “passive” even when the power accumulation amount of the RF tag becomes zero. The switch means can be kept open / closed depending on which mode is started.

  According to the RF tag system of the sixth aspect, the control unit of the RF tag controls to open the normally closed switch means for intermittently connecting between the antenna and the power generation unit when operating in the active mode. . Therefore, it is possible to improve the reception performance by avoiding that the signal received by the antenna wraps around to the power generation unit side.

  According to the RF tag of the ninth aspect, similarly to the RF tag constituting the RF tag system according to the first aspect, the power supply generation unit and the power storage unit are provided, and the operation modes are “passive”, “active”, “ Each mode of “charging” is configured to be executable. Then, when the command specifying the response method transmitted by the tag reader is received, if the response method specified based on the power storage amount of the power storage unit is executable, the unique ID information and the power storage amount of the power storage unit can be executed. And a response signal including information indicating.

  The RF tag operates in either “passive” or “charge” mode preset by the tag reader until the power storage amount exceeds the operable level of the active mode, and the power storage amount is in the active mode. When it exceeds the operable level, it operates “active”. When operating in “passive” or “active”, the operation mode during power storage is set to either “passive” or “charge” by a command transmitted from the tag reader. Therefore, an effect similar to that of the first aspect can be obtained.

  According to the tag reader of claim 10, similarly to the RF tag constituting the RF tag system of claim 1, the RF tag configured to be able to execute each mode of “passive”, “active”, and “charge” Command to set the operation mode for storing power in the power supply to either "passive" or "charging" mode when the RF tag is operating in "passive" or "active" mode Send. Therefore, as in claim 1, if the RF tag side tends to be short of power storage and the operation in the active mode is difficult, if the RF tag is set to the charging mode, The charging of the power storage unit is prioritized by the electromagnetic wave to be transmitted, and the RF tag can reach the state operable in the active mode in a short time.

(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 to 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.

  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, since the RF tag 1 can also select a semi-passive mode in which the power source selection unit 6 selects the power source storage unit 5 and the response method selection unit selects the passive modulation unit 11P as an operation mode. The communication distance can be extended. 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.

(Second embodiment)
7 and 8 show a second embodiment of the present invention. The same parts as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. Hereinafter, different parts will be described. The second embodiment is different from the first embodiment in the configuration of the RF tag. FIG. 7 is a partial equivalent diagram of FIG. 1, and a normally closed switch 31 (SW 2, switch means) is inserted between the antenna 3 and the power generation unit 4. The power generation unit 4 includes a diode 32 and a capacitor 33 (C1) as an example of a specific configuration.

  The power storage unit 34 replaces the power storage unit 5 of the first embodiment, and includes a power storage capacitor (for example, an electric double layer capacitor) 35 (C2). Between the positive side terminal of the capacitor 33 of the power generation unit 4, a conduction control unit (conduction control means) 36 configured by, for example, a series circuit of three diodes is disposed. A normally open switch 37 (SW1, switch means) is connected in parallel to the conduction control unit. Opening / closing control of the switches 31 and 37 is performed by the control unit 8.

  The RF tag 38 configured as described above can select “charging mode” as the fourth operation mode. When operating in the charging mode based on the command transmitted from the reader / writer 2, communication with the reader / writer 2 is not performed, and charging to the power storage unit 34 is prioritized.

  Next, the operation of the second embodiment will be described with reference to FIG. As an initial state of the RF tag 38, the switch 37 is OFF and the switch 31 is ON. The operation mode is “passive” by default. When the carrier is transmitted from the reader / writer 2 and communication is started and the RF tag 38 receives the operation mode setting command (step S11), the RF tag 38 determines whether or not the operation mode designated by the command is the charging mode. Judgment is made (step S12). If it is not the charging mode (NO), the process proceeds to step S17 to determine whether or not the designated operation mode is the passive mode. If the passive mode is designated (YES), the switch 31 is turned on and the switch 37 of the power storage unit 34 is turned off (step S18, but ON / OFF control is not necessary if starting from the default), It operates in the passive mode (step S19). In addition, you may transfer to step S4 of FIG. 6 here.

  That is, when operating in the passive mode, charging of the capacitor 35 of the power storage unit 34 is performed by 3VF (VF is a forward voltage of the diode, for example, the terminal voltage difference between the capacitors 35 and 33 is set in the conduction control unit 36. 0.6V) or more is not started. That is, when communicating with the reader / writer 2 by operating in the passive mode, the capacitor 35 of the power storage unit 34 is charged only when there is a surplus in received power even if the power consumed in the communication is subtracted. .

  On the other hand, if the designated operation mode is the charging mode in step S12 (YES), the control unit 8 turns on the switch 37 of the power storage unit 34 (switch 31 is also on, step S13). Then, since the conduction control unit 36 is bypassed, the power generated by the power generation unit 4 is supplied so as to charge the capacitor 35 first. In this state, the control unit 8 waits until the voltage V2 of the power storage unit 34 becomes equal to or higher than the operable voltage Va in the active mode via the voltage detection unit 7 (step S14), and when V2 ≧ Va ( YES) Switch 31 is turned OFF (step S15). Then, the operation mode is switched to the active (or semi-passive) mode (step S16), and thereafter the operation is performed in the switched mode. In addition, you may transfer to step S9 of FIG. 6 here.

  In step S15, the switch 31 is turned off because the power storage unit 34 does not need to be charged when operating in the active (or semi-passive) mode. Therefore, the switch 31 is opened and the received signal from the reader / writer 2 is supplied with power. The purpose is to prevent the storage unit 34 from turning around and improve the signal reception efficiency.

  In step S17, if the designated operation mode is active or semi-passive mode (NO), V2 ≧ Va is compared as in step S14 (step S20), and if V2 ≧ Va ( (YES) The process proceeds to step S15, and if V2 <Va (NO), the process ends. The above processing may be started when the operation mode of the RF tag 38 is “active” or “charge”.

As described above, according to the second embodiment, the RF tag 38 has either “passive” or “charge” set in advance until the voltage V2 of the power storage unit 34 exceeds the operable level Va in the active mode. In this mode, when V2 ≧ Va, it operates in the active mode. When the RF tag 38 is operating in “passive” or “active”, the reader / writer 2 transmits a command to charge the power storage unit 34 (during power storage) and set the operation mode to “passive”. ”Or“ Charge ”.
Therefore, when the power storage amount of the power storage unit 34 is insufficient and the operation in the active mode is difficult, the RF tag 38 is set to the charging mode, and the carrier transmitted by the reader / writer 2 depends on the carrier. Prioritizing charging of the power storage unit 34, the RF tag 38 can reach the state operable in the active mode in a short time.

Further, in the RF tag 38, when the potential difference between the power generation unit 4 and the power storage unit 34 becomes equal to or greater than the predetermined value Vd, the conduction control unit 36 conducts, and the control unit 8 of the RF tag 38 operates in the passive mode. Since the switch 37 connected in parallel to the conduction control unit 36 is opened and the switch 37 is closed when operating in the charging mode, in the passive mode, the power consumed in the passive mode is less than the power generated by the power generation unit 4. If there is a surplus even after subtraction, the power storage unit 34 can be charged. On the other hand, in the charging mode, the power storage unit 34 can be preferentially charged.
Furthermore, when the control unit 8 of the RF tag 38 operates in the active mode, the control unit 8 opens the switch 31 that connects and disconnects between the antenna 3 and the power generation unit 4, so that the signal received by the antenna 3 is the power generation unit 4 side. The reception performance can be improved by avoiding sneaking around.

(Third embodiment)
FIG. 9 shows a third embodiment of the present invention, where (a) is a communication procedure between the reader / writer 2 and the RF tag 38, (b) is an operation mode of the RF tag 38, and (c) is a power storage unit 34. It shows an example of the change of the voltage V2. The third embodiment shows a case where the power storage unit 34 is not charged at all and starts from a state where the voltage V2 is zero. That is, the operation before the “processing start” in the flowchart of the second embodiment is also included.
Further, the switch 37 of the RF tag 38 is configured by a latch type switch that can hold the open / closed state, and even when the power storage amount of the power storage unit 34 becomes zero, the next activation is “passive”, “ The open / close state of the switch 32 can be maintained depending on which mode of “charging” is started.

  In this case, the initial state of the RF tag 38 is a charging mode (FIG. 9B), and when the reader / writer 2 transmits a carrier, charging of the power storage unit 34 is started and the voltage V2 increases. When the voltage V2 exceeds the operable voltage Va in the passive mode, the RF tag 38 switches the operation mode to “passive” by itself.

  Then, when a command such as “request” or “selection” is transmitted from the reader / writer 2, the RF tag 38 returns a response in the passive mode. In the response, as in the second embodiment, the power storage unit 34 Send information about the amount of power stored. The control unit 13 (accumulation amount determination means) of the reader / writer 2 refers to the electric power accumulation amount included in the response, determines whether the level is operable in the active mode, and determines “operation is possible”. Then, a command for designating the operation mode to “active” is transmitted to the RF tag 38. When a command designating “active” is selected, the RF tag 38 switches the operation mode to “active”. Thereafter, when a command specifying the operation mode “passive” is selected from the reader / writer 2, the command is switched to “passive”.

  As described above, according to the third embodiment, the RF tag 38 starts operation in the charging mode and switches the operation mode to “passive” when the power storage amount exceeds the operable level Vp in the passive mode. ”Is returned in response to the reader / writer 2, and when the reader / writer 2 receives the response, the power storage amount exceeds the operable level of the active mode. If it is determined, a command for switching the operation mode to “active” is transmitted to the RF tag 38.

Therefore, the reader / writer 2 proceeds to charge the power storage unit 34 during the period in which the RF tag 38 is operating in the passive mode, and the power storage amount reaches the operable level in the active mode according to the response from the RF tag 38. If it is determined that it has exceeded, the operation mode of the RF tag 38 can be switched to “active” to efficiently operate in the active mode. Further, when the RF tag 38 is operating in the active mode, the operation mode is changed to “passive” by the command transmitted from the reader / writer 2, so that the reader / writer 2 side determines that the operation in the active mode is unnecessary. At that time, the operation mode can be switched.
In addition, since the switch 31 of the RF tag 38 is configured as a latch type switch, even when the power storage amount becomes zero, the next activation is started in “passive” or “charging” mode. Thus, the open / closed state of the switch 31 can be maintained.

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.
In the second embodiment, the RF tag 38 stores the operation mode specified last time by the reader / writer 2 and starts in the charging mode when starting in accordance with the stored operation mode. good.
What is necessary is just to change suitably the electric potential difference Vd set to the conduction | electrical_connection control part 36 according to each design.
The switch 31 may be arranged as necessary.
The switches 31 and 37 may use transistors.
The components shown in FIG. 7 may be configured as a single chip by configuring all components other than the antenna 3 on an IC chip.

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 FIG. 1 is a partial equivalent diagram of FIG. 1 showing a second embodiment of the present invention. 6 equivalent diagram FIG. 4 is a diagram illustrating a third embodiment of the present invention, where (a) is a communication procedure between a reader / writer and an RF tag, (b) is an RF tag operation mode, and (c) is an example of a change in voltage V2.

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, 12 is a non-volatile memory, and 13 is a control unit (accumulation amount determination means). , 34 is a power storage unit (power storage unit), and 38 is an RF tag.

Claims (10)

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,
As an operation mode of the RF tag,
When the power source selection unit selects the power source generation unit and the response method selection unit selects the passive modulation unit, if there is surplus power used as an operation power source, the surplus power is stored in the power storage unit Passive mode to
An active mode in which the power source selection unit selects the power storage unit and the response method selection unit selects the active modulation unit;
A charge mode for preferentially storing the power generated by the power generation unit by the received electromagnetic wave in the power storage unit;
The RF tag is
Until the power storage amount exceeds a level operable in the active mode, it operates in either the passive mode or the charging mode preset by the tag reader,
When the power storage amount exceeds a level operable in the active mode, the active mode operates.
When operating in the passive mode or the active mode, the operation mode during power storage can be changed to either the passive mode or the charging mode according to a command transmitted from the tag reader. RF tag system characterized by this. The RF tag starts operating in the charging mode, and when the power storage amount exceeds a level operable in the passive mode, the operation mode is switched to the passive mode,
When operating in the passive mode, it returns information indicating the power storage amount in response to the tag reader,
When the tag reader receives the response, the tag reader includes a storage amount determination unit that determines whether the power storage amount exceeds a level operable in the active mode, and the tag reader exceeds the operable level. 2. The RF tag system according to claim 1, wherein if it is determined, a command for switching an operation mode to the active mode is transmitted to the RF tag.   3. The RF tag system according to claim 1, wherein when the RF tag is operating in the active mode, the operation mode is changed to a passive mode by a command transmitted from the tag reader.   The RF tag is inserted between the power generation unit and the power storage unit, and is connected in parallel to the conduction control unit that conducts when the potential difference between the two becomes a predetermined value or more. The switch unit is configured to open the switch unit when operating in the passive mode and to close the switch unit when operating in the charge mode. The RF tag system according to any one of 1 to 3.   5. The RF tag system according to claim 4, wherein the switch means is constituted by a latch type switch capable of holding an open / closed state.   The RF tag includes a normally-closed switching unit that intermittently connects the antenna and the power generation unit, and the control unit controls the switching unit to open when operating in the active mode. The RF tag system according to any one of claims 1 to 5, wherein   An RF tag used in the RF tag system according to claim 1.   A tag reader used in the RF tag system according to claim 1. An antenna that receives an electromagnetic wave transmitted from the tag reader, a power generation unit that generates its own operating power source from the electromagnetic wave received by this antenna, a power storage unit that stores the operating power source power, and this power storage Supplied from any one of a storage amount detection unit that detects a power storage amount of a unit, a control unit that switches an operation mode according to the power storage amount, and the power generation unit and the power storage unit according to the operation mode. A power source selection unit that switches whether to use a power source to be used, a passive modulation unit that returns a response signal by a backscatter method using electromagnetic waves transmitted from the tag reader, and a power source supplied from the power storage unit An active modulation unit that modulates electromagnetic waves to be transmitted and returns a response signal, and the passive modulation unit and the active modulation according to the operation mode And a response method selection unit for selecting one of a,
As the operation mode,
When the power source selection unit selects the power source generation unit and the response method selection unit selects the passive modulation unit, if there is surplus power used as an operation power source, the surplus power is stored in the power storage unit Passive mode to
An active mode in which the power source selection unit selects the power storage unit and the response method selection unit selects the active modulation unit;
A charge mode for preferentially storing the power generated by the power generation unit by the received electromagnetic wave in the power storage unit;
Until the power storage amount exceeds a level operable in the active mode, it operates in either the passive mode or the charging mode preset by the tag reader,
When the power storage amount exceeds a level operable in the active mode, the active mode operates.
When operating in the passive mode or the active mode, the operation mode during power storage can be changed to either the passive mode or the charging mode according to a command transmitted from the tag reader. RF tag characterized by. Communication using an RF tag and electromagnetic waves configured to be able to operate in any of a passive mode, an active mode using a built-in power supply, and a charging mode in which received power is preferentially stored in the power supply. In the tag reader to perform,
When the RF tag is operating in the passive mode or the active mode, a command for causing the RF tag to set an operation mode for storing power in the power source to either the passive mode or the charging mode. A tag reader characterized by transmitting.

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