JP4779040B2 - RFID tag reading method - Google Patents

Description

  The present invention relates to a technology for reading a unique identifier of an RFID (Radio Frequency IDentification) tag by a reader, and more particularly, to a method for reading an RFID tag that activates a specific one of a plurality of RFID tags and reads the unique identifier. It relates to effective technology.

  In recent years, management systems for objects using RFID tags have become widespread in systems such as physical distribution management. In these systems, an RFID tag storing a unique identifier (which may be simply referred to as “ID” in the following) is attached to each managed object, and this information is used as an RFID reader (hereinafter simply “ May be referred to as a “reader”), and wirelessly communicates with the RFID tag to perform contactless reading. As a result, it is possible to identify the individual and type of the management object and accurately grasp the location and the like, thereby enabling efficient management.

  In communication between an RFID tag and a reader, generally, each RFID tag that has received a call (question) signal from the reader transmits its ID as a response to the reader. The reader transmits the received ID information to the RFID tag, so that each RFID tag recognizes whether or not its own ID has been read by the reader. Note that there are two types of RFID tag systems: an active type with a built-in battery, and a passive type that does not have a built-in battery and acquires power and carrier wave oscillation from a radio wave output from a reader.

  In systems such as physical distribution management, it is necessary to read RFID tags attached to a large number of articles existing in a relatively large area in a short time to detect the type of article or search for the target article. . For this reason, an active type having a wide communication range is mainly used. However, since the active type operates using a built-in battery, it is essential to reduce power consumption when long-term use is considered.

  On the other hand, for example, Japanese Patent Application Laid-Open No. 2006-339964 (Patent Document 1) discloses a first antenna that receives a signal in the first frequency band and a second antenna that transmits a signal in the second frequency band. Antenna, a control circuit that detects a control signal received by the first antenna and outputs control data, and a transmission circuit that outputs a response signal from the second antenna when the control data is input. A non-contact IC medium is described in which the first frequency band is set to a frequency band lower than the second frequency band.

  In the non-contact IC medium of Patent Document 1, the first frequency band is an LF (long wave) band (frequency 30 kHz to 300 kHz, wavelength 10 km to 1 km), and control is transmitted in the LF band (first frequency band). A busy tone that is control data superimposed on the control signal is extracted, and a non-contact IC medium corresponding to the busy tone has a second frequency band higher than the LF band (first frequency band). Efficient data transmission / reception is controlled by frequency. This eliminates the use of a high frequency band during standby, eliminating the need for a tuning circuit that operates at a high frequency, and greatly reducing power consumption in a control information input standby state as compared to conventional non-contact IC media. Making it possible.

  In a non-contact IC medium such as an RFID tag, in order to enable the above-described configuration, for example, a specific activation pattern is detected by waiting for a call signal (control signal) using an LF band from a reader, and a specific activation pattern is detected. As a control circuit that outputs a signal for starting a microcomputer or the like inside the RFID tag when a pattern is detected, a wake-up receiver (for example, Non-Patent Document 1) is used.

JP 2006-339964 A

“Product Information: AS3932 Programmable 3D Low Power LF Wakeup Receiver”, [online], austriamicrosystems, [searched on August 18, 2009], Internet <URL: http://www.austriamicrosystems.com/jpn/node_78/node_379 / Low-Frequency / AS3932>

  In the conventional RFID tag, as described above, only the control circuit (such as a wake-up receiver) that waits for the LF band call signal from the reader is used by using the LF band for the call signal from the reader. It operates with low power consumption, and other microcomputers are stopped to reduce power consumption during standby.

  However, in the RFID tag of the prior art, the activation pattern detected by the control circuit is normally set to be uniform for each unit such as a manufacturer of the RFID tag or the reader. Accordingly, in a system such as physical distribution management, RFID tags are attached to a large number of articles, and when a specific article (RFID tag) is searched for among them, a call signal (start pattern) from the reader is used. On the other hand, all RFID tags included in the readable range are activated once and transmit their IDs. This process is repeated until the target RFID tag is found (the reader receives the ID from the target RFID tag).

  As a result, the number of activations and the number of operations of each RFID tag increase and the power consumption increases as a whole, so that the built-in battery is consumed quickly. In addition, since RFID tags other than the intended ones are activated to transmit their own IDs, there is a high possibility that collisions and reading errors will occur in the reader, and the time required for reading will also increase.

  Therefore, an object of the present invention is to read only the ID of a specific RFID tag and to read the ID when the RFID tag is called by transmitting a startup pattern using a signal in a low frequency band such as the LF band from a reader. Is to provide a reading method.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.

  In the RFID tag reading method according to the representative embodiment of the present invention, a reader outputs a call signal including a specific activation pattern in a first frequency band, and the call signal in the first frequency band. When the active type RFID tag waiting for the detection detects the activation pattern that matches the first activation pattern set in the RFID tag in the call signal, the RFID tag activates the entire RFID tag, and the first frequency An RFID tag reading method in which the reader reads the ID of the RFID tag by transmitting the ID of the RFID tag to the reader in a second frequency band higher than the band. It is what has.

  That is, the RFID tag is set with the first activation pattern that is different for each of the one or more RFID tags, and the reader includes the activation signal included in the calling signal when outputting the calling signal. As the pattern, the first activation pattern set in the RFID tag to be called is dynamically set.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  According to a typical embodiment of the present invention, by using a signal in a low frequency band such as an LF band from a reader and setting and transmitting a specific activation pattern, only a target RFID tag to be called is transmitted. Can be activated. As a result, the power consumption of the entire RFID tag can be minimized, and since the reader does not read the ID transmitted from the unnecessary RFID tag, collisions and reading errors are reduced, and reading is performed. The time required can be shortened.

  In addition, according to a typical embodiment of the present invention, a control circuit that detects a specific activation pattern by waiting for a call signal in the LF band and outputs a signal that activates the whole when a specific activation pattern is detected Can be installed in the reader as a repeater, so that the reader can call and activate a specific repeater to communicate while avoiding interference with call signals for other RFID tags and repeaters. it can. Thereby, the ID information of the RFID tag read by the reader can be transferred by wireless communication to a remote site or terminal while minimizing the power consumption during standby.

It is the figure shown about the outline | summary of the reading method of the RFID tag which is Embodiment 1 of this invention. It is the figure which showed the outline | summary of the structural example of the reader in Embodiment 1 of this invention. It is the figure which showed the outline | summary of the structural example of the RFID tag in Embodiment 1 of this invention. It is the figure which showed the example of the calling signal transmitted from the reader in this Embodiment. It is the figure shown about the outline | summary of the reading method of the RFID tag which is Embodiment 2 of this invention. It is the figure which showed the outline | summary of the structural example of the repeater in Embodiment 2 of this invention. It is the flowchart which showed the example of the flow of the process in the reading method of the RFID tag which is Embodiment 2 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

<Embodiment 1>
[Overview]
FIG. 1 is a diagram showing an outline of an RFID tag reading method according to Embodiment 1 of the present invention. FIG. 1 shows an example in which a specific article is searched for from among a large number of articles attached with RFID tags, and the upper diagram shows an outline when a RFID tag attached to each article is called from a reader. The lower diagram shows an outline when an RFID tag activated in response to a call from a reader responds with an ID.

  In the upper diagram, it is assumed that each RFID tag A to C (200a to 200c) has a startup pattern of "A" to "C" as its own startup pattern. Only the operation of waiting for a call signal in the LF band from the reader 100 including the pattern is performed with low power consumption.

  On the other hand, the reader 100 has an LF antenna 111 for outputting a call signal in the LF band, and transmits a control signal including a specific activation pattern from the LF antenna 111 as a call signal. At this time, the reader 111 uses an activation pattern (“B” in the example of FIG. 1) corresponding to the RFID tag (RFID tag B (200b) in the example of FIG. 1) to be called as a specific activation pattern. It can be set dynamically.

  In response to the call signal from the reader 100, only the RFID tag B (200b) for which the activation pattern “B” is set reacts and activates in the lower diagram, and the own ID “BB” is called as a response. Transmission is performed using a frequency band (for example, 2.4 GHz band) higher than the LF band of the signal. At this time, the other RFID tag A (200a) and RFID tag C (200c) are activated because the activation pattern ("B") included in the calling signal is different from their own ("A", "C"). do not do.

  As a result, unnecessary RFID tag A (200a) and RFID tag C (200c) are not activated, so that the target RFID tag B (200b) can be quickly found out while suppressing power consumption, and the found RFID tag B (200b). It is possible to read the ID by performing reliable communication with.

[Equipment configuration]
FIG. 2 is a diagram showing an outline of a configuration example of the reader in the present embodiment. The reader 100 includes various units such as an LF transmission unit 110, an LF antenna 111, an RF unit 130, a control unit 140, a memory 150, and an input / output unit 160, for example. The LF transmission unit 110 has a function of generating a call signal including an activation pattern and outputting the call signal from the LF antenna 111 using the LF band. The LF transmitter 110 can be configured using, for example, a dedicated IC (Integrated Circuit). The LF antenna 111 is an antenna for outputting a calling signal including an activation pattern in the LF band. In the present embodiment, for example, a 400 mmΦ loop antenna is used.

  The RF unit 130 has a function of performing bidirectional communication such as transmission / reception of an ID with an RFID tag activated by a call signal using, for example, a 2.4 GHz band as a frequency band higher than the LF band of the call signal. . The RF unit 130 can be configured using, for example, a dedicated device including an antenna. In this embodiment, as a frequency band used for two-way communication, a 2.4 GHz band that can easily obtain a device for performing high-capacity data with high speed and power saving is used. However, the present invention is not limited to this, and other frequency bands may be used.

  The control unit 140 has an interface with each unit of the reader 100 and has a function of controlling the operation of each unit. The control unit 140 can be configured using, for example, a microcomputer having a CPU (Central Processing Unit). The control unit 140 further includes an activation pattern setting unit 141, and can set an activation pattern corresponding to the RFID tag to be called to the LF transmission unit 110 to set it as a calling signal. The activation pattern setting unit 141 may be configured to acquire an activation pattern to be instructed / set from a memory 150 (to be described later) based on, for example, an instruction from the user via the input / output unit 160 (to be described later). It is.

  The memory 150 is a storage medium that holds data unique to the reader 100, application data, and the like, and is configured by a nonvolatile memory such as an EEPROM (Electrically Erasable and Programmable Read Only Memory). In this memory 150, values of each activation pattern that can be transmitted by the reader 100 are stored in association with key data such as a display name that can be easily identified by the user.

  The input / output unit 160 has an input / output interface function for the user. For example, the terminal is connected to a terminal such as an external PC, and an operation instruction including designation of the activation pattern of the RFID tag to be called is input from the terminal, or information such as the ID of the RFID tag read to the terminal is input. It is possible to output. The reader 100 having the above-described configuration is disposed, for example, at a gate or the like through which a pallet on which a large number of articles with RFID tags are loaded passes in a system such as physical distribution management.

  FIG. 3 is a diagram showing an outline of a configuration example of the RFID tag in the present embodiment. The RFID tag 200 is an active type having a built-in battery 260, and includes various parts such as an LF receiving unit 220, an RF unit 230, a control unit 240, and a memory 250, for example.

  The LF reception unit 220 detects a call signal including an activation pattern that matches the own activation pattern held in the LF reception unit 220 among the call signals output from the reader 100 in the LF band, It has a function of outputting an activation signal for activating other components. The LF receiver 220 can be configured by using, for example, the above-described wake-up receiver IC, a receiving transponder coil, and the like, so that the RFID tag 200 as a whole is stopped. However, it is possible to continue the waiting operation of the call signal from the reader 100 at all times.

  Similar to the RF unit 130 of the reader 100, the RF unit 230 has a function of performing bidirectional communication such as ID transmission / reception with the reader 100 using, for example, a 2.4 GHz band. The RF unit 230 can be configured using, for example, a dedicated device including an antenna.

  Similar to the control unit 140 of the reader 100, the control unit 240 has an interface with each unit of the RFID tag 200, and has a function of controlling the operation of each unit. The control unit 240 can be configured using, for example, a microcomputer having a CPU. Similar to the memory 150 of the reader 100, the memory 250 is a storage medium that holds data unique to the RFID tag 200, application data, and the like, and is configured by a nonvolatile memory such as an EEPROM, for example.

  Usually, the current that always flows when the LF receiver 220 waits for a call signal in the LF band is about several μA. On the other hand, when a call signal having a matching activation pattern is detected and other units such as the control unit 240 are activated, a current of several mA to ten and several mA flows. Further, when the ID is transmitted to the reader 100 by the RF unit 230 thereafter, a current of several tens of mA is required.

  Therefore, the reader 100 uses the activation pattern as an identification signal in order to identify the RFID tag 200 to be called, thereby suppressing the activation of each part with high power consumption for the unnecessary RFID tag 200 that is not to be called. As a result, power consumption can be minimized.

[Call signal]
FIG. 4 is a diagram illustrating an example of a call signal transmitted from the reader 100 in the present embodiment. The call signal is composed of, for example, a preamble, an activation pattern, and data from the top. Here, the preamble is a CW wave (Continuous Wave: unmodulated continuous wave) for a certain period of time, enabling the identification of the calling signal by the LF receiver 220 of the RFID tag 200 and supplying power to the RFID tag 200. Is also used.

  The activation pattern is, for example, a value having a length of 8 bits. In this case, 256 activation patterns can be set. Depending on the type of wake-up receiver used in the LF receiver 220 of the RFID tag 200, a 16-bit value may be used. This activation pattern may be arbitrarily set so as to be unique for each target item, each item type, each location, or the like, and stored in the LF receiver 220 of the RFID tag 200. it can.

  The activation pattern set in the LF receiving unit 220 of the RFID tag 200 can be dynamically changed by an instruction from the reader 100 or the control unit 240 of the RFID tag 200 to the LF receiving unit 220. . Accordingly, for example, using a timer provided inside the RFID tag 200, it is determined whether or not a predetermined period has elapsed since the RFID tag 200 was attached to the article by the control unit 240, and the predetermined period Can be applied to a usage such as easily detecting an expired article by changing the activation pattern set in the LF receiving unit 220 to a specific one. .

  As described above, according to the reading method of the RFID tag 200 of the present embodiment, a specific activation pattern is set and transmitted from the reader 100 using a signal in a low frequency band such as the LF band. Thus, it is possible to activate only the target RFID tag 200 to be called and read the ID, so that the power consumption of the entire RFID tag 200 can be minimized. In addition, since the reader 100 does not read the ID transmitted from the unnecessary RFID tag 200, collisions and reading mistakes are reduced, and the time required for reading is shortened to quickly and reliably search for a specific article or the like. be able to.

<Embodiment 2>
[Overview]
FIG. 5 is a diagram showing an outline of the RFID tag reading method according to the second embodiment of the present invention. FIG. 5 shows an example in which the RFID tag ID information read by the reader is transferred by wireless communication to a remote site or terminal via a repeater.

  In the example of FIG. 5, the part in which the reader 100 outputs the calling signal including the activation pattern (activation pattern “B” in the example of FIG. 5) to each of the RFID tags A to C (200a to c) is described above. This is the same as FIG. 1 of the first embodiment. At this time, although not shown, the RFID tag B (200b) having the same activation pattern is activated and transmits its own ID “BB” to the reader 100, as in FIG. 1 of the first embodiment.

  When the reader 100 receives the ID “BB” from the RFID tag B (200b) to be called, the reader 100 sets the unique activation pattern “a” set in the repeater A (300a) and calls again using the LF band. Output a signal. When the repeater A (300a) is activated by detecting this calling signal, the reader 100, although not shown, reads the information of the read ID “BB” by bidirectional communication using the 2.4 GHz band. Forward to.

  When receiving the information of ID “BB” from the reader 100, the repeater A (300a) sets the unique activation pattern “b” set in the repeater B (300b) in the same manner as described above, and sets the LF band. The call signal by is output. When this call signal is detected and the repeater B (300b) is activated, the repeater A (300a) transmits the received ID “BB” information to the repeater by bidirectional communication in the 2.4 GHz band, although not shown. Transfer to B (300b).

  As described above, by repeating transfer processing (repeat hop) between repeaters using mutually unique activation patterns, the repeater at a remote location can be used without causing interference of the calling signal at each repeater. Information of ID “BB” read by the reader 100 can be reliably transferred to N (300n) by wireless communication. That is, it is possible to read the ID of the target RFID tag 200 from the RFID tags 200 attached to a large number of articles and grasp this information from a remote location.

  The distance between the reader 100 and the repeater A (300a) and each repeater is about 30 to 50 m at the maximum because the LF band is used for the calling signal, but each repeater A to N (300a -N), like the RFID tags A to C (200a to 200c), normally, only the standby operation for the call signal of the LF band is performed, and the power consumption is low. Therefore, long distance communication (ID transfer) can be performed by adopting a multi-hop configuration using a plurality of repeaters in this way.

[Equipment configuration]
FIG. 6 is a diagram showing an outline of a configuration example of the repeater in the present embodiment. The repeater 300 basically includes each unit of the reader 100 (the LF transmission unit 110, the LF antenna 111, the RF unit 130, the control unit 140, the memory 150, and the input / output unit 160) illustrated in FIG. A similar LF transmission unit 310, LF antenna 311, RF unit 330, control unit 340, memory 350, and input / output unit 360 are included. In addition to this, the LF receiving unit 320 similar to the LF receiving unit 220 in the RFID tag 200 shown in FIG.

  As a result, the repeater 300 outputs a calling signal including a specific activation pattern in the reader 100 in the LF band, and detects the output activation pattern and activates the other party (another repeater 300) to 2.4 GHz. The function of transmitting and receiving information such as ID by two-way communication using the band and the function of performing only the waiting operation of the calling signal by the LF band with low power consumption while the RFID tag 200 is normally stopped as a whole. It will be.

  Note that the memory 350 of the repeater 300 may hold an activation pattern for activating another repeater 300 at the transfer destination (hop destination). In this embodiment, the configuration of the reader 100 and each of the RFID tags A to C (200a to 200c) is the same as that in FIGS.

[Process flow]
FIG. 7 is a flowchart showing an example of a processing flow in the RFID tag reading method of the present embodiment. In FIG. 7, in order to simplify the description, in the example of FIG. 5, the information of the ID “BB” of the RFID tag B (200 b) read by the reader 100 is transferred to the repeater B (through the repeater A (300 a). 300b) and the relay B (300b) grasps the information of the ID “BB” of the RFID tag B (200b) (when the number of hops is 2).

  First, the reader 100 sets an activation pattern for calling the RFID tag B (200b) (S101). Here, the activation pattern setting unit 141 of the reader 100 may acquire and set a corresponding one from the activation patterns held in the memory 150, or between repeaters and between the repeater and the reader 100 as described later. The target activation pattern is designated to the reader 100 from the repeater B (300b) via the repeater A (300a) using the bidirectional communication in the 2.4 GHz band between It may be. In the example of FIG. 7, it is assumed that the activation pattern “B” set in the RFID tag B (200b) is set.

  Next, the reader 100 calls the target RFID tag B (200b) by outputting a calling signal including the set activation pattern “B” in the LF band (S102). As a result, the RFID tag B (200b) in which the activation pattern “B” is set is activated (S201). At this time, the repeater A (300a) does not start and does not interfere because the activation pattern is different for “a”.

  The RFID tag B (200b) activated by detecting the calling signal including the activation pattern “B” responds by transmitting its own ID “BB” to the reader 100 in the 2.4 GHz band (S202). The reader 100 that has received the response of the ID “BB” from the RFID tag B (200b) transmits a notification indicating that the ID “BB” has been read to the RFID tag B (200b) by transmitting in the 2.4 GHz band. (S103). The RFID tag B (200b) that has received the notification from the reader 100 stops operations other than the call signal waiting operation in the LF receiving unit 220 (S203).

  In step S103, the reader 100 that has notified the RFID tag B (200b) that the ID “BB” has been read next transfers the information of the read ID “BB” to the relay A (300a). The activation pattern “a” of the repeater A (300a) is set, and a call signal including this is output in the LF band, thereby calling the repeater A (300a) (S104). As a result, the repeater A (300a) in which the activation pattern “a” is set is activated (S301). At this time, the RFID tag B (200b) does not start and does not interfere because the activation pattern is different for “B”.

  The repeater A (300a) activated by detecting the calling signal including the activation pattern “a” transmits its own ID to the reader 100 in the 2.4 GHz band and responds (S302). The reader 100 that has received the response of the ID from the repeater A (300a) transmits to the repeater A (300a) that the ID has been received in the 2.4 GHz band and notifies it (S105). Thereafter, the read information of the ID “BB” is transferred to the repeater A (300a) in the 2.4 GHz band (S106).

  The relay A (300a) that has received the read ID “BB” information from the reader 100 next transfers the received ID “BB” information to the relay B (300b). By setting the activation pattern “b” of 300b) and outputting a call signal including this in the LF band, the repeater B (300b) is called (S303). Thereby, the repeater B (300b) set with the activation pattern “b” is activated (S311). At this time, the reader 100 is not particularly affected.

  The repeater B (300b) activated by detecting the calling signal including the activation pattern “b” responds by transmitting its ID to the repeater A (300a) in the 2.4 GHz band (S312). . The repeater A (300a) that has received the ID response from the repeater B (300b) transmits to the repeater B (300b) in the 2.4 GHz band and notifies that the ID has been received (S304). ). Thereafter, the information of the ID “BB” received from the reader 100 is transferred to the repeater B (300b) in the 2.4 GHz band (S305), and the operations other than the call signal waiting operation in the LF receiving unit 320 Is stopped (S306).

  The repeater B (300b) that has received the information of the ID “BB” read by the reader 100 from the repeater A (300a) displays this information on an external terminal or the like via the input / output unit 360, By outputting to the program, information of ID “BB” read by the reader 100 existing at the remote site is output (S313).

  As described above, according to the reading method of the RFID tag 200 of the present embodiment, the reader 100 and the repeater 300 are configured by adding the LF receiving unit 320 to the configuration of the reader 100 to form the repeater 300. In addition, while avoiding interference with call signals for other RFID tags 200 and other repeaters 300, it is possible to call and activate a specific repeater 300 to perform two-way communication. Thereby, the information on the ID of the RFID tag 200 read by the reader 100 can be reliably transferred to the remote repeater 300 by wireless communication while minimizing the power consumption in the entire standby state. That is, it is possible to read and grasp the ID of a specific RFID tag 200 from a remote place.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  The present invention can be used for a method of reading an RFID tag that activates a specific one of a plurality of RFID tags and reads its ID.

DESCRIPTION OF SYMBOLS 100 ... Reader, 110 ... LF transmission part, 111 ... LF antenna, 130 ... RF part, 140 ... Control part, 141 ... Activation pattern setting part, 150 ... Memory, 160 ... Input / output part,
200 ... RFID tag, 200a-c ... RFID tag A to C, 220 ... LF receiving unit, 230 ... RF unit, 240 ... control unit, 250 ... memory, 260 ... built-in battery,
300 ... repeater, 300a, b, n ... repeaters A, B, N, 310 ... LF transmission unit, 320 ... LF reception unit, 330 ... RF unit, 340 ... control unit, 341 ... activation pattern setting unit, 350 ... Memory, 360... Input / output unit.

Claims (4)

The leader outputs a calling signal including a specific activation pattern in the first frequency band,
When the RFID tag of the active type waiting for the calling signal in the first frequency band detects the activation pattern that matches the first activation pattern set in the RFID tag in the calling signal, the RFID Activating the entire tag and transmitting the RFID tag ID to the reader in a second frequency band higher than the first frequency band,
An RFID tag reading method in which the reader reads the ID of the RFID tag,
In the RFID tag, the first activation pattern that is different for each of the one or more RFID tags is set,
The reader, when outputting the calling signal, the as said start pattern the call signal comprises, dynamically set the RFID tag of the first activation pattern set in the subject to call, further calls subject When the information of the ID of the RFID tag is read, the call signal including the second activation pattern set in the first repeater is output in the first frequency band,
When the first repeater waiting for the call signal in the first frequency band detects the second activation pattern in the call signal, the first repeater is activated, and the first repeater is activated. Transmitting the ID of the first repeater to the reader in a frequency band of 2,
Thereafter, the RFID tag reading method is characterized in that the reader transmits the ID information of the RFID tag read by the reader to the first repeater . The RFID tag reading method according to claim 1 ,
When the first repeater receives the ID information of the RFID tag read by the reader , a third activation pattern set in the second repeater in the first frequency band The call signal including:
When the second repeater waiting for the call signal in the first frequency band detects the third activation pattern in the call signal, the second repeater is activated, and the second repeater is activated. Transmitting the ID of the second repeater to the first repeater in a frequency band of 2,
Then, the RFID tag reading method, wherein the ID information of the RFID tag read by the reader is transmitted from the first repeater to the second repeater and transferred. The RFID tag reading method according to claim 1 or 2 ,
The RFID tag reading method, wherein the first frequency band is an LF band. In the reading method of the RFID tag according to any one of claims 1 to 3 ,
The RFID tag is configured to change the first activation pattern set in the RFID tag based on an instruction from the reader or a predetermined processing result in the RFID tag. Method.