Tag communication device and specific wireless tag

Abstract

To provide a technique for reallocating a backscatter frequency to a specific wireless tag without stopping signal communication with wireless tags other than the specific wireless tag with which signal communication is interrupted.SOLUTION: A tag communication device includes a first communication execution unit that executes allocation communication with a plurality of wireless tags, the allocation communication being communication for assigning a different backscatter frequency to each of the plurality of wireless tags, a signal receiving unit that receives, from each of the plurality of wireless tags, a signal having a backscatter frequency assigned to the wireless tag, and a second communication execution unit that, when it is determined that an abnormality has occurred in a specific wireless tag among the plurality of wireless tags, executes countermeasure communication with the specific wireless tag to deal with the abnormality by using a specific frequency that is different from any of the backscatter frequencies assigned to each of one or more wireless tags other than the specific wireless tag.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a tag communication device capable of communicating with a plurality of wireless tags. [Background technology]

[0002] Patent Document 1 discloses a device that transmits radio waves to multiple wireless tags and receives signals having backscatter frequencies from each of the multiple wireless tags. The device assigns different backscatter frequencies to each of the multiple wireless tags. This makes it possible to avoid interference between signals from the multiple wireless tags. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-200180 A Summary of the Invention [Problem to be solved by the invention]

[0004] After a backscatter frequency is assigned to each of the multiple wireless tags, an abnormality may occur in a specific wireless tag among the multiple wireless tags. However, if communication with all the wireless tags is stopped to resolve the abnormality, a period will occur during which communication with any of the wireless tags is not possible.

[0005] This specification provides a technique for dealing with an abnormality that has occurred in a specific wireless tag without stopping signal communication with wireless tags other than the specific wireless tag in which the abnormality has occurred. [Means for solving the problem]

[0006] This specification discloses a tag communication device capable of communicating with a plurality of wireless tags. The tag communication device includes: a first communication execution unit that executes allocation communication with each of the plurality of wireless tags, the allocation communication being communication for assigning a different backscatter frequency to each of the plurality of wireless tags; a signal receiving unit that repeatedly transmits radio waves to each of the plurality of wireless tags after executing the allocation communication with each of the plurality of wireless tags, and receives a signal having the backscatter frequency assigned to the wireless tag from each of the plurality of wireless tags; and a second communication execution unit that, when it is determined that an abnormality has occurred in a specific wireless tag among the plurality of wireless tags in the signal communication with the plurality of wireless tags, executes a countermeasure communication with the specific wireless tag to counter the abnormality by using a specific frequency different from any of the backscatter frequencies assigned to one or more wireless tags other than the specific wireless tag among the plurality of wireless tags.

[0007] According to this configuration, in the countermeasure communication with the specific wireless tag, a specific frequency different from any of the backscatter frequencies assigned to one or more wireless tags other than the specific wireless tag is used. This makes it possible to prevent the countermeasure communication with the specific wireless tag from interfering with the signal communication with one or more wireless tags. In other words, it is possible to counter an abnormality occurring in the specific wireless tag without stopping the signal communication with one or more wireless tags.

[0008] The second communication execution unit may execute the allocation communication as the countermeasure communication with the specific wireless tag when it is determined that the signal communication with the specific wireless tag has been interrupted.

[0009] The wireless tag uses radio waves from the device as power. A backscatter frequency is assigned to the wireless tag by writing a setting value to the memory in the wireless tag. When the radio waves to the wireless tag are cut off and the power supply to the wireless tag is cut off, the setting value in the memory is automatically erased. If the power supply to a specific wireless tag is cut off while signals are being repeatedly received from multiple wireless tags, the signals from the specific wireless tag are also cut off. As described above, the setting value in the specific wireless tag is also erased. To resume signal communication with multiple wireless tags including the specific wireless tag, it is necessary to reassign a backscatter frequency to the specific wireless tag.

[0010] According to the above configuration, when signal communication with a specific wireless tag is interrupted, it is possible to execute assigned communication with the specific wireless tag while avoiding interference with one or more wireless tags.

[0011] The second communication execution unit may, by executing the assigned communication with the specific wireless tag, assign to the specific wireless tag the backscatter frequency that is the same as the backscatter frequency that was assigned to the specific wireless tag before it was determined that the signal communication with the specific wireless tag was interrupted.

[0012] With this configuration, it is possible to assign backscatter frequencies to a plurality of wireless tags within the same band that was used before it was determined that signal communication with a particular wireless tag had been lost.

[0013] The tag communication device may further include a demodulation unit that demodulates the signals received from each of the plurality of wireless tags, and a first judgment unit that judges that communication of the signals with the specific wireless tag has been interrupted when a demodulation success rate per unit time of the signals from the specific wireless tag falls below a predetermined first value.

[0014] When the demodulation success rate per unit time falls below the first value, it means that there is a time during the unit time during which a signal from a specific wireless tag could not be received. By using the demodulation success rate, it is possible to determine when signal communication with a specific wireless tag will be interrupted.

[0015] The tag communication device may further include a transmitting unit that transmits a specific command different from the radio waves to each of the plurality of radio tags while repeatedly transmitting the radio waves to each of the plurality of radio tags, and a second judgment unit that judges that the signal communication with the specific radio tag has been interrupted when a response to the specific command is received from the specific radio tag while repeatedly transmitting the radio waves to each of the plurality of radio tags.

[0016] Receiving a response to a specific command from a specific wireless tag means that there is a high possibility that the specific wireless tag has stopped transmitting radio wave responses, i.e., signals having backscatter frequencies. By using the reception of a response to a specific command, it is possible to determine that signal communication with a specific wireless tag has been lost.

[0017] The tag communication device may further include a third judgment unit that judges that signal communication with the specific wireless tag has been interrupted when the radio wave strength of the signal from the specific wireless tag falls below a predetermined second value.

[0018] When the radio wave strength falls below the second threshold, it means that there is a high possibility that the signal communication with the specific wireless tag will be interrupted. By using the radio wave strength, it is possible to determine that the signal communication with the specific wireless tag will be interrupted.

[0019] The allocation communication may include transmitting a command to the specific wireless tag to write a first setting value indicating the backscatter frequency to be assigned to the specific wireless tag to the specific wireless tag, and the tag communication device may further include a determination unit that determines a second setting value to be written to the specific wireless tag instead of the first setting value by using a map corresponding to the radio wave strength of a signal from the specific wireless tag, the map indicating a correlation between the backscatter frequency to be assigned to the specific wireless tag and the setting value to be written to the specific wireless tag, and the response communication may include transmitting a command to the specific wireless tag to write the second setting value to the specific wireless tag by using the specific frequency.

[0020] For example, the frequency of a signal from a specific wireless tag may deviate from the backscatter frequency assigned to the specific wireless tag depending on the environment in which the specific wireless tag is placed. Here, in an experiment, it was found that when the radio wave intensity of the signal from the wireless tag indicates a certain value, a correlation exists between the backscatter frequency to be assigned to the wireless tag and the setting value to be written to the wireless tag. According to the above configuration, the tag communication device can write the second setting value determined using the map corresponding to the radio wave intensity to the specific wireless tag while avoiding interference with one or more wireless tags. The deviation of the backscatter frequency can be eliminated.

[0021] In the allocation communication, a first backscatter frequency is assigned to the specific wireless tag, and a second backscatter frequency adjacent to the first backscatter frequency is assigned to other wireless tags among the plurality of wireless tags that are different from the specific wireless tag, and the countermeasure communication includes transmitting a change signal to the specific wireless tag using the specific frequency to change the backscatter frequency when the radio wave strength of the signal from the specific wireless tag is greater than the radio wave strength of the signal from the other wireless tags by a predetermined value or more, and after the countermeasure communication is executed, the backscatter frequency assigned to the specific wireless tag and the backscatter frequency assigned to the other wireless tags do not have to be adjacent to each other.

[0022] When the radio wave strength of a signal from a specific wireless tag is greater than the radio wave strength of signals from other wireless tags by a predetermined value or more, the signal from the other wireless tag may be hidden at the bottom of the band (spectrum width) of the signal from the specific wireless tag. According to the above configuration, when it is expected that the signal from the other wireless tag will be hidden at the bottom of the band of the signal from the specific wireless tag, the tag communication device transmits a change signal to the specific wireless tag. This makes it possible to prevent the backscatter frequency assigned to the specific wireless tag and the backscatter frequency assigned to the other wireless tags from being adjacent to each other, and to prevent the signal from the other wireless tag from being hidden at the bottom of the band of the signal from the specific wireless tag.

[0023] Each of the multiple wireless tags stores an adjustment setting value for adjusting the radio wave strength of the signal to the tag communication device, and the countermeasure communication includes transmitting an adjustment signal to the specific wireless tag using the specific frequency when the radio wave strength of the signal from the specific wireless tag is greater than a predetermined value or more than the radio wave strength of signals from other wireless tags among the multiple wireless tags that are different from the specific wireless tag, and the adjustment signal may be a signal for changing the adjustment setting value in the specific wireless tag to lower the radio wave strength of the signal from the specific wireless tag.

[0024] According to the above configuration, by lowering the radio wave strength of the signal from a specific wireless tag, it is possible to prevent signals from other wireless tags from being hidden in the tail of the band of the signal from the specific wireless tag.

[0025] The specific frequency is a specific backscatter frequency that is the backscatter frequency assigned to the specific wireless tag before it is determined that an abnormality has occurred in the signal communication with the specific wireless tag, and the band of the specific frequency may be narrower than the band of the specific backscatter frequency.

[0026] By using a specific frequency having a narrow band, it is possible to suppress signals from one or more wireless tags other than the specific wireless tag from becoming noise in the assigned communication.

[0027] The specific frequency may be a frequency different from any of the backscatter frequencies assigned to each of the multiple wireless tags before it is determined that an abnormality has occurred in the signal communication with the specific wireless tag.

[0028] By using a frequency different from any of the backscatter frequencies assigned to multiple wireless tags, it is possible to prevent signals from one or more wireless tags other than a specific wireless tag from becoming noise in the assigned communication.

[0029] This specification discloses a specific wireless tag capable of communicating with a tag communication device, the specific wireless tag including a memory, a storage control unit that executes an allocation communication with the tag communication device and stores a setting value indicating a specific backscatter frequency in the memory, a modulation unit that modulates a reflected wave of a radio wave from the tag communication device into a signal having the specific backscatter frequency according to the setting value in the memory after executing the allocation communication with the tag communication device, and a determination unit that determines whether the strength of the radio wave from the tag communication device is equal to or greater than a specific value, and the modulation unit may modulate the reflected wave into the signal by lowering the radio wave strength of the reflected wave below a default value when it is determined that the strength of the radio wave from the tag communication device is equal to or greater than the specific value.

[0030] When the radio wave strength of the radio wave from the tag communication device is equal to or greater than a specific value, the radio wave strength of the reflected wave for the radio wave may be greater than expected. When the radio wave strength of the reflected wave is greater than expected, signals from other radio tags different from the specific radio tag may be hidden at the bottom of the band of the signal from the specific radio tag. According to the above configuration, when it is expected that the signal from the specific radio tag will be hidden at the bottom of the band of the signal from the other radio tags, the specific radio tag voluntarily lowers the radio wave strength of the reflected wave below the default. This makes it possible to prevent the signal from the specific radio tag from being hidden at the bottom of the band of the signal from the other radio tags. It is possible to eliminate the situation in which the signal from the other radio tags is hidden at the bottom of the band of the signal from the specific radio tag. [Brief description of the drawings]

[0031] [Figure 1] 1 is a block diagram showing a tag communication device and a wireless tag. [Diagram 2] 4 is a sequence diagram showing communication between a tag communication device and a wireless tag. FIG. [Diagram 3] FIG. 4 is a flowchart of the processing executed by the tag communication devices according to the first to third embodiments. [Figure 4] FIG. 11 is a sequence diagram showing a specific case. [Diagram 5]FIG. 11 is a sequence diagram showing a comparative example. [Figure 6] FIG. 13 is a diagram showing a specific example of use. [Figure 7] FIG. 13 is a flowchart of a process executed by a tag communication device according to a fourth embodiment. [Figure 8] FIG. 2 is a diagram showing the signal bands of each wireless tag. [Figure 9] FIG. 13 is a flowchart of a process executed by a tag communication device according to a fifth embodiment. [Figure 10] FIG. 13 is a block diagram showing a wireless tag according to a sixth embodiment. [Figure 11] FIG. 2 is a diagram showing the signal bands of each wireless tag. [Figure 12] FIG. 13 is a flowchart of a process executed by a tag communication device according to a seventh embodiment. [Figure 13] FIG. 13 is a block diagram showing a wireless tag according to an eighth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] (First embodiment) (Configuration of tag communication device 10; Figure 1) The tag communication device 10 is a device capable of communicating with multiple wireless tags 100, 200, and 300. Although three wireless tags 100, 200, and 300 are illustrated in Fig. 1, the number of wireless tags is not limited to three, and may be two, four, or more. The wireless tag is, for example, a Radio Frequency Identification (RFID) tag.

[0033] The tag communication device 10 includes an antenna unit 12, a modulation unit 14, a demodulation unit 16, a filter unit 18, and a control unit 30. The antenna unit 12 includes an antenna that transmits a carrier wave to each wireless tag and receives a reflected wave of the carrier wave from each wireless tag. The configuration of the antenna unit 12 may be, for example, a known configuration, and detailed description will be omitted in this specification. In this embodiment, the antenna unit 12 transmits a carrier wave in the UHF band. In a modified example, the antenna unit 12 may transmit a carrier wave in a band other than the UHF band.

[0034] The modulation unit 14 is a circuit that modulates a UHF carrier wave and supplies it to the antenna unit 12. The modulation unit 14 can also supply a UHF carrier wave to the antenna unit 12 without modulating it. Hereinafter, a modulated carrier wave will be referred to as a "modulated wave", and an unmodulated carrier wave will be referred to as an "unmodulated wave". The demodulation unit 16 is a circuit that demodulates a reflected wave received by the antenna unit 12 and supplies it to the control unit 30. The filter unit 18 is a filter that removes noise and the like other than the reflected wave from the radio wave received by the antenna unit 12. The configurations of the modulation unit 14, the demodulation unit 16, and the filter unit 18 may be, for example, known configurations, and detailed description thereof will be omitted in this specification.

[0035] The tag communication device 10 includes four demodulation units 16. One of the four demodulation units 16 is assigned to one of the multiple wireless tags 100 to 300. By including four demodulation units 16, demodulation of signals received from four wireless tags can be performed simultaneously. Note that the number of demodulation units 16 is not limited to four, and may be, for example, two, three, five or more.

[0036] The control unit 30 is a circuit that controls each of the units 12, 14, and 16 in accordance with a program 40 stored in the memory 34. For example, the control unit 30 controls the modulation unit 14 to transmit a specific command onto a carrier wave to the antenna unit 12. The control unit 30 also obtains information from the digital signal obtained from the demodulation unit 16, and stores the information in the memory 34. The memory 34 includes a volatile memory and a non-volatile memory.

[0037] (Configuration of wireless tags 100 and 200; FIG. 1) The wireless tag 100 includes an antenna unit 112, a modulation unit 114, a demodulation unit 116, and a control unit 130. The antenna unit 112 includes an antenna that receives a carrier wave from the tag communication device 10 and transmits a reflected wave of the carrier wave. Here, the reflected wave has a backscatter frequency. The backscatter frequency is a frequency that is shifted from the frequency of the carrier wave, that is, the so-called carrier frequency, by a predetermined frequency. The backscatter frequency is a so-called subcarrier frequency. The backscatter frequency is, for example, within a range of 600 kHz before and after the frequency of the carrier wave. The configuration of the antenna unit 112 may be, for example, a known configuration, and detailed description thereof will be omitted in this specification.

[0038] The demodulation unit 116 demodulates the carrier wave received by the antenna unit 112 and supplies the demodulated signal to the control unit 130. The modulation unit 114 modulates the reflected wave of the carrier wave received by the antenna unit 112 and supplies the modulated signal to the antenna unit 112. The configurations of the modulation unit 114 and the demodulation unit 116 may be, for example, known configurations, and detailed description thereof will be omitted in this specification.

[0039] The control unit 130 is a circuit that controls the units 112, 114, and 116. For example, the control unit 130 controls the modulation unit 114 to transmit information stored in the memory 134 to the antenna unit 112 via a reflected wave.

[0040] The control unit 130 includes an oscillator circuit for generating a reflected wave having a backscatter frequency. The backscatter frequency is determined based on the frequency of the oscillator circuit. The oscillator circuit is, for example, a ring oscillator, and is a circuit that does not include an oscillator such as a crystal. By not using an oscillator, the oscillator circuit operates with low power consumption.

[0041] The control unit 130 includes a memory 134. The memory 134 includes a volatile memory and a non-volatile memory. The memory 134 stores a tag ID "t01" and a frequency setting value 140. The tag ID "t01" is an ID for identifying the wireless tag 100. The frequency setting value 140 is a setting value for adjusting the backscatter frequency. The backscatter frequency can be adjusted by changing the frequency setting value 140.

[0042] The control unit 130 is connected to the sensor 160. The sensor 160 is, for example, a sensor that measures acceleration. The measurement values ​​measured by the sensor 160 are stored in the memory 134.

[0043] Each of the units 112, 114, 116, and 130 of the wireless tag 100 uses a carrier wave as power. The wireless tag 100 is a so-called passive tag. The wireless tag 200 has a similar configuration to the wireless tag 100, and the wireless tags 200 and 300 store tag IDs "t02" and "t03" that identify the wireless tags 200 and 300.

[0044] (Communication between tag communication device 10 and wireless tag 100) With reference to FIG. 2, communication between the tag communication device 10 and the wireless tag 100 will be described. When the tag communication device 10 receives an instruction from a user to start communication with each wireless tag, it starts transmitting a carrier wave. The tag communication device 10 continuously transmits the carrier wave until it receives an instruction from the user to end communication with each wireless tag. Here, when the tag communication device 10 transmits a command to each wireless tag, it transmits a modulated wave to each wireless tag. On the other hand, when the tag communication device 10 receives information from each wireless tag, it transmits an unmodulated wave to each wireless tag. Here, the frequency of the modulated wave and unmodulated wave, which are each command, is the carrier frequency.

[0045] At T2, the tag communication device 10 transmits an inventory command to the wireless tag 100. The inventory command is a command for acquiring a tag ID. In reality, the inventory command includes multiple commands, and the tag communication device 10 transmits the multiple commands sequentially. The multiple commands include, for example, an ACK.

[0046] At the next T4, the tag communication device 10 transmits an unmodulated wave to the wireless tag 100. The wireless tag 100 transmits the tag ID "t01" as a response to the inventory at T2 on the reflected wave of the unmodulated wave from the tag communication device 10. As a result, the tag communication device 10 receives the tag ID "t01" from the wireless tag 100.

[0047] At T6, the tag communication device 10 transmits a write command to the wireless tag 100 to write a specific value to the frequency setting value 140. The write command includes the specific value and the tag ID "t01" acquired at T4. By writing the specific value to the frequency setting value 140, the wireless tag 100 is assigned a specific backscatter frequency corresponding to the specific value. Furthermore, since the write command includes the tag ID "t01", the wireless tag 100 is designated as the wireless tag that processes the write command. In other words, even if a write command including the tag ID "t01" is received by a wireless tag other than the wireless tag 100, the wireless tag other than the wireless tag 100 ignores the write command.

[0048] At the next T8, the tag communication device 10 transmits an unmodulated wave to the wireless tag 100. The wireless tag 100 transmits a response to the write command at T6 on the reflected wave of the unmodulated wave from the tag communication device 10. This notifies the tag communication device 10 that writing of the specific value to the frequency setting value 140 has been completed.

[0049] At T10, the tag communication device 10 transmits a command to start streaming to the wireless tag 100. Streaming is a process of repeatedly transmitting an unmodulated wave and repeatedly receiving the measurement value of the sensor 160 from each wireless tag. T12A to T12C represent streaming. The tag communication device 10 repeatedly receives the measurement value of the sensor 160 from each wireless tag by streaming. This makes it possible to continuously sample the measurement value of the sensor 160 at short intervals.

[0050] Communications from T2 to T12C are also performed between the other wireless tags 200 and 300. For example, at T6, the wireless tag 200 is assigned a backscatter frequency different from that of the wireless tag 100. By assigning different backscatter frequencies to the wireless tags 100 and 200, respectively, the streaming of the wireless tag 100 is distinguished from the streaming of the wireless tag 200. As a result, streaming can be performed simultaneously between the wireless tags 100 and 200. In other words, the measurement value of the wireless tag 100 can be synchronized with the measurement value of the wireless tag 200.

[0051] (Processing of tag communication device 10; FIG. 3) The process executed by the control unit 30 of the tag communication device 10 in accordance with the program 40 will be described with reference to Fig. 3. The process in Fig. 3 realizes the communication shown in Fig. 2.

[0052] In S10, the control unit 30 determines an assigned frequency, which is a backscatter frequency, to be assigned to each of a plurality of wireless tags (e.g., 100 to 300). For example, the assigned frequency to the wireless tag 100 is determined to be 920 MHz+200 kHz, the assigned frequency to the wireless tag 200 is determined to be 920 MHz+400 kHz, and the assigned frequency to the wireless tag 200 is determined to be 920 MHz+600 kHz.

[0053] In S12, the control unit 30 transmits an inventory command to each wireless tag. Through the process of S12, communications at T2 and T4 in Fig. 2 are executed, and the control unit 30 acquires a tag ID from each wireless tag.

[0054] In S14, the control unit 30 transmits a write command to each of the wireless tags. The write command includes the tag ID of the destination wireless tag and a setting value corresponding to the backscatter frequency determined in S10. The process of S14 executes the communications of T6 and T8 in FIG. 2, and the control unit 30 writes the setting value to each wireless tag.

[0055] In S16, the control unit 30 judges whether or not the error between the frequency of the reflected wave of each of all the wireless tags and the assigned frequency determined in S10 is within the allowable range. If the error is within the allowable range for each of the wireless tags, the control unit 30 judges that the allocation of the backscattering frequency to all the wireless tags has been successful. If the control unit 30 judges that the allocation of the backscattering frequency to all the wireless tags has been successful (YES in S16), the control unit 30 proceeds to the process of S18 and onwards. On the other hand, if the control unit 30 judges that the allocation of the backscattering frequency to any of the wireless tags has failed (NO in S16), the control unit 30 proceeds to S14. The process of S14 is repeatedly executed for each of all the wireless tags until the error between the frequency of the reflected wave of each of the wireless tags and the assigned frequency determined in S10 is within the allowable range.

[0056] In S18, the control unit 30 transmits a streaming start command to each wireless tag. This starts streaming, and the measured values ​​of the sensor 160 are repeatedly received from each wireless tag. The process of S18 executes the communication of T10 in FIG. 2.

[0057] When streaming starts, the control unit 30 executes monitoring of S20, S30, and S50. In S20, it monitors whether a streaming response is received from each wireless tag. The process of S20 executes the processes of T12A to T12C in FIG.

[0058] When the control unit 30 receives a streaming response from each wireless tag (YES in S20), the control unit 30 proceeds to S22. In S22, the control unit 30 executes processing on the demodulated data obtained by demodulating the response, i.e., the measurement value of the sensor 160. For example, the control unit 30 stores the measurement value of the sensor 160 in the memory 134. When S22 ends, the control unit 30 returns to monitoring from S20 to S50.

[0059] In addition, in S30, the control unit 30 monitors whether or not the demodulation success rate of each of all wireless tags performing streaming falls below a predetermined threshold value. Here, the demodulation success rate is the rate at which streaming responses are successfully demodulated per unit time.

[0060] As described above, the wireless tag is of a passive type. For example, a situation is assumed in which the radio waves from the tag communication device 10 have difficulty reaching the wireless tag (e.g., due to a shielding object) and the wireless tag moves to a null point of the radio waves from the tag communication device 10. In this case, the power supply to the wireless tag may be interrupted in the middle of streaming. For example, when the power supply to the wireless tag is interrupted, the response from the wireless tag is also interrupted. When the response is interrupted, demodulation of the response is not performed and the demodulation success rate decreases. In other words, when the demodulation success rate falls below a predetermined threshold, it means that there is a high possibility that the response from the wireless tag will be interrupted.

[0061] Furthermore, if the power supply to the wireless tag is interrupted, the value written in the frequency setting value 140 in the wireless tag is automatically erased. Therefore, in order to resume streaming with a wireless tag that has lost power, it is necessary to reassign a backscatter frequency to the wireless tag.

[0062] When the demodulation success rate for a specific wireless tag among all wireless tags performing streaming falls below a predetermined threshold (YES in S30), the control unit 30 executes the processes of S32 to S42. By executing the processes of S32 to S42, it is possible to reassign a backscatter frequency to the specific wireless tag from which responses have ceased (hereinafter, referred to as the "target tag").

[0063] In S32, the control unit 30 determines a reset frequency to be used for writing the inventory and the setting value. In this embodiment, the reset frequency is the same as the backscatter frequency assigned to the setting target tag. In other words, the reset frequency is a frequency different from any of the backscatter frequencies assigned to one or more wireless tags other than the setting target tag among the multiple wireless tags.

[0064] In S34, the control unit 30 determines an allocation frequency to be assigned to the tag to be set. In this embodiment, the allocation frequency determined in S34 is the same as the backscatter frequency that was assigned to the tag to be set. With this configuration, it is possible to assign a backscatter frequency to each of the multiple wireless tags within the same band that was used before it was determined that the signal communication with the tag to be set was interrupted.

[0065] In a modified example, the assigned frequency determined in S34 may be a frequency different from any of the backscattering frequencies assigned to all the wireless tags. With this configuration, it is possible to avoid reusing a proven frequency that has stopped responding. It is expected that the stability of streaming will be improved after the backscattering frequency is reset.

[0066] S36 is the same as S12, except that the frequency of the inventory command is the reset frequency. S38 is the same as S14, except that the frequency of the write command is the reset frequency. S40 is the same as S16, except that it determines whether or not the setting is successful for the target tag. S42 is the same as S18, except that the frequency of the start command is the reset frequency. When the process of S42 ends, the process returns to monitoring of S20 to S50.

[0067] Furthermore, in S50, the control unit 30 monitors whether an instruction to stop streaming has been received. When the control unit 30 receives an instruction to stop streaming (YES in S50), in S52, the control unit 30 stops transmitting radio waves to each wireless tag to stop streaming. When the process of S52 ends, the control unit 30 ends the process of FIG. 3.

[0068] (Specific case; Figure 4) In this case, the wireless tags 100 to 300 are assigned backscatter frequencies F1 to F3, respectively, and streaming is started (S18 in FIG. 3). At time t1, reception of a streaming response from the wireless tag 300 is interrupted. At time t2, the control unit 30 determines that the demodulation success rate of the wireless tag 300 falls below a predetermined threshold (YES in S30 in FIG. 3). In this case, the control unit 30 determines the reset frequency F4 (S32). In this embodiment, the reset frequency F4=F3. The control unit 30 transmits an inventory command having the reset frequency F4 and a write command having the reset frequency F4 to the wireless tag 300 (S36, S38), and writes a setting value corresponding to the assigned frequency F3 to the wireless tag 300. Then, the control unit 30 transmits a streaming start command having the reset frequency F4 to the wireless tag 300, and streaming of the wireless tag 300 is resumed after time t3.

[0069] As described above, the reset frequency F4 is different from the backscatter frequencies F1 and F2 assigned to the other wireless tags 100 and 200. This makes it possible to prevent each command, such as an inventory command, from interfering with the streaming responses from the other wireless tags 100 and 200. In other words, the backscatter frequency F3 can be reassigned to the wireless tag 300 without stopping the streaming of the other wireless tags 100 and 200.

[0070] For example, as shown in FIG. 5, a comparative example is assumed in which streaming of all three wireless tags 100-300 is stopped at time t2, and backscatter frequencies are reassigned to all three wireless tags 100-300. In this comparative example, it is not possible to receive the measurement values ​​of the sensor 160 from the wireless tags 100 and 200 other than the wireless tag 300 from time t2 to time t3. Furthermore, the backscatter frequencies F1-F3 are not used from time t2 to time t3, and the frequency utilization efficiency is poor. In contrast, in the case of FIG. 4 in this embodiment, the backscatter frequencies F1 and F2 are used from time t2 to time t3, and the frequency utilization efficiency is better than that of the comparative example.

[0071] In this embodiment, the reset frequency F4=F3, and the band of the reset frequency F4 is narrower than the band of the backscatter frequency F3 assigned to the wireless tag 300. Although the reset frequency F4 is different from the other backscatter frequencies F1 and F2, the portion where the band of the other backscatter frequency (e.g., F2) overlaps with the band of the reset frequency F4 may become noise of the command having the reset frequency F4. By narrowing the band of the reset frequency F4, the range of the overlap between the band of the other backscatter frequency and the band of the reset frequency F4 can be narrowed. As a result, the noise of the command having the reset frequency F4 is reduced, and the resetting of the assigned frequency can be stably executed. In a modified example, the band of the reset frequency F4 may be the same as the band of the backscatter frequency F3.

[0072] (Application of the technology disclosed herein; Figure 6) The technology disclosed in this specification can be used, for example, to attach three wireless tags 100 to 300 to different locations on a predetermined moving object and simultaneously measure the accelerations of the different locations on the predetermined moving object. This makes it possible to measure not only the amount of movement of the predetermined moving object, but also the rotation of the predetermined moving object. Here, the predetermined moving object is, for example, a pallet.

[0073] Furthermore, the physical quantity measured by the sensor 160 is not limited to acceleration, and may be other physical quantities such as vibration, current, etc. For example, wireless tags may be attached to multiple locations on a structure, and the sensor may be used to simultaneously measure vibrations at multiple locations. Examples of the structure include buildings, bridges, and other structures, and automobiles and other products.

[0074] (Modification of the first embodiment) The reset frequency determined in S32 of FIG. 3 may be a frequency different from any of the backscatter frequencies assigned to all the wireless tags. For example, it is assumed that the band of the backscatter frequency assigned to the setting target tag overlaps with the band of the backscatter frequency assigned to other wireless tags. In this situation, if the reset frequency is set to a frequency different from any of the backscatter frequencies assigned to each of all the wireless tags, the band of the reset frequency can be separated from the band of the backscatter frequency used by wireless tags other than the setting target tag. Then, the overlapping range of both bands can be made relatively narrow. As a result, the noise of the command having the reset frequency F4 is reduced, and the resetting of the assigned frequency can be stably executed.

[0075] (Correspondence) The wireless tags 100 to 300 are examples of "multiple wireless tags". The setting target tag and the wireless tag 300 in FIG. 4 are examples of "specific wireless tags". The wireless tags 100 and 200 in FIG. 4 are examples of "one or more wireless tags". The tag communication device 10 and the demodulation unit 16 are examples of "tag communication device" and "demodulation unit", respectively. The threshold value of S30 in FIG. 3 is an example of "first value". Communications at T4 and T6 in FIG. 2 and S12 and S14 in FIG. 3 are examples of "allocation communications". The responses of T12A to T12C in FIG. 2 and the response of S20 in FIG. 3 are examples of "signals". The reset frequency of S32 in FIG. 3 is an example of "specific frequency".

[0076] T4 and T6 in Fig. 2 and S12 and S14 in Fig. 3 are examples of processing realized by a "first communication execution unit". T12A to T12C in Fig. 2 and S20 in Fig. 3 are examples of processing realized by a "signal receiving unit". S36 and S38 in Fig. 3 are examples of processing realized by a "second communication execution unit".

[0077] (Second Example) (Processing of tag communication device 10; FIG. 3) This embodiment is similar to the first embodiment except that the determination method in S30 in FIG. 3 is different. In this embodiment, a predetermined test command is periodically transmitted to each of all wireless tags while streaming is being performed. The predetermined test command may be any modulated wave, for example, an inventory command. In S30 of this embodiment, the control unit 30 monitors whether or not a response to the test command is received from any of all wireless tags. For example, receiving a response to the test command from a specific wireless tag among all wireless tags means that there is a high possibility that the power supply to the specific wireless tag has been cut off and streaming has stopped. When receiving a response to the test command from a specific wireless tag, the control unit 30 determines that the streaming response of the specific wireless tag has been cut off, and executes the processes of S32 to S42. In this embodiment, it is possible to determine that the streaming response to the specific wireless tag has been cut off by utilizing the reception of the response to the test command. The test command in this embodiment is an example of a "specific command".

[0078] (Third Example) (Processing of tag communication device 10; FIG. 3) This embodiment is similar to the first embodiment, except that the judgment method in S30 in FIG. 3 is different. In S30 in this embodiment, the control unit 30 judges whether the RSSI of the streaming response from each of all wireless tags is below a predetermined value. RSSI indicates the strength of the radio wave. When the RSSI is below the predetermined value, it means that there is a high possibility that the signal communication with the wireless tag will be interrupted. When the RSSI of the response from a specific wireless tag among all wireless tags is below the predetermined value, the control unit 30 judges that the streaming response from the specific wireless tag has been interrupted, and executes the processes of S32 to S42. Using the RSSI, it is possible to judge that the streaming response from the specific wireless tag has been interrupted. The predetermined value and RSSI in this embodiment are examples of the "second value" and the "radio wave strength", respectively.

[0079] (Fourth Example) In the first embodiment, when reception of a streaming response from a specific wireless tag is interrupted, an inventory is executed again, and streaming with the specific wireless tag is resumed. Streaming abnormalities are not limited to reception of a streaming response being interrupted. For example, depending on the environment (e.g., location, surrounding conditions) in which the specific wireless tag is placed, the frequency of the streaming response from the specific wireless tag may deviate from the backscatter frequency assigned to the specific wireless tag. The fourth embodiment aims to deal with the deviation in the backscatter frequency.

[0080] (Processing of tag communication device 10; FIG. 7) The process in Fig. 7 is similar to the process in Fig. 3, except that the process executed when YES is determined in S30 is different. When the demodulation success rate for a specific wireless tag is below a predetermined threshold (YES in S30), the CPU 32 proceeds to S100. In S100, the CPU 32 determines a reset frequency to be used for writing in S106, which will be described later. The reset frequency is, for example, the same frequency as the backscatter frequency assigned to the specific wireless tag.

[0081] In S102, the CPU 32 measures the radio wave strength of the streaming response from a specific wireless tag. The radio wave strength is, for example, reception power or RSSI. Here, the unit of reception power is, for example, dBm.

[0082] In S104, the CPU 32 determines an adjustment value to be written to the frequency set value 140 of a specific wireless tag in S106, which will be described later. In an experiment, it was found that a correlation exists between the assigned frequency and the frequency set value 140 when the radio wave intensity of the wireless tag indicates a certain value. For example, a positive correlation as shown in FIG. 7 is obtained for each of the radio wave intensities P1 to P4. Note that the correlation is not limited to the linear relationship shown in FIG. 7, and may be a nonlinear relationship. In this embodiment, the tag communication device 10 stores a map 50 indicating the above correlation.

[0083] For example, an assigned frequency Ft is determined in S10, and a default setting value corresponding to the assigned frequency Ft is written in S14. When an abnormality occurs in streaming, the frequency of the streaming response deviates from the assigned frequency Ft, and the radio wave intensity of the streaming response also deviates from a normal value.

[0084] For example, when the radio wave strength measured in S102 is P3, which is different from the normal value, the CPU 32 uses the map 50 of the radio wave strength P3 in S104 to determine an adjustment value X1 corresponding to the assigned frequency Ft. Also, when the radio wave strength measured in S102 is P2, which is different from the normal value, the CPU 32 uses the map 50 of the radio wave strength P2 in S104 to determine an adjustment value X2, which is different from the adjustment value X1.

[0085] In S106 following S104, the CPU 32 transmits to the specific wireless tag a write command for writing the adjustment value determined in S104 to the frequency setting value 140. As a result, the adjustment value is written to the frequency setting value 140 of the specific wireless tag instead of the default setting value. When S106 ends, the CPU 32 returns to monitoring S20, S30, and S50.

[0086] According to the configuration of this embodiment, the tag communication device 10 can use the reset frequency to avoid interference with wireless tags other than the specific wireless tag and rewrite the frequency setting value 140. By rewriting the frequency setting value 140, it is possible to eliminate the deviation of the backscatter frequency.

[0087] (Correspondence) The default setting value written in S14 and the adjustment value written in S106 in Fig. 7 are examples of a "first setting value" and a "second setting value", respectively. Map 50 is an example of a "map".

[0088] (Fifth Example) When the environment in which a specific wireless tag is placed changes after streaming starts, the radio wave strength of the streaming response from the specific wireless tag also changes. FIG. 8(a) shows an example of the radio wave strength of the streaming response from each wireless tag at the start of streaming. The radio wave strength of two wireless tags 100 and 200 with tag IDs "t01" and "t02" indicates Y1, and the radio wave strength of the wireless tag 300 with tag ID "t03" indicates Y2. Here, Y2 is a value smaller than Y1. Also, the wireless tags 100, 200, and 300 are assigned backscatter frequencies F1, F2, and F3, respectively, and the frequency F1 is adjacent to the frequency F2, and the frequency F2 is adjacent to the frequency F3. In other words, no other backscatter frequency is assigned between adjacent frequencies (e.g., F1 and F2). As shown in (a) of Fig. 8, if there is no change in the environment in which each wireless tag is placed, the peak of the streaming response of each wireless tag will not be hidden by the tail of the band (spectrum width) of the streaming response of other wireless tags. In the situation of (a) of Fig. 8, the tag communication device 10 can identify the streaming response of each wireless tag.

[0089] However, for example, when the environment in which the wireless tag 200 is placed changes, as shown in FIG. 8(b), the radio wave strength of the wireless tag 200 changes from Y2 to Y3, which is greater than Y2. In this case, the radio wave strength of the band of the streaming response from the wireless tag 200 also increases. As a result, the peak of the streaming response from the wireless tag 300 may be hidden in the tail of the band of the streaming response from the wireless tag 200. In the situation of FIG. 8(b), there is a possibility that the streaming response from the wireless tag 300 cannot be identified. The present embodiment aims to deal with the situation shown in FIG. 8(b).

[0090] (Processing of tag communication device 10; FIG. 9) The process of Fig. 9 is the same as the process of Fig. 3, except that the process executed when the determination in S30 is YES is different. When the demodulation success rate for a specific wireless tag is below a predetermined threshold (YES in S30), the CPU 32 proceeds to S112.

[0091] In S112, the CPU 32 measures the radio wave intensity of the streaming response from each of all wireless tags communicating by streaming.

[0092] In S114, the CPU 32 uses all the radio wave intensities measured in S112 to determine a radio tag (hereinafter, referred to as a "change target tag") whose backscatter frequency should be changed from among all the radio tags communicating by streaming. Specifically, for two adjacent backscatter frequencies, the CPU 32 compares the radio wave intensity of a response having one backscatter frequency with the radio wave intensity of a response having the other backscatter frequency. If, as a result of comparing the two, the radio wave intensity of one is greater than the radio wave intensity of the other by a predetermined value or more, the CPU 32 determines the radio tag to which the backscatter frequency having one radio wave intensity is assigned as the change target tag. For example, in the case shown in FIG. 8(b), it is determined that the radio wave intensity Y3 of the radio tag 200 is greater than the radio wave intensity Y2 of the radio tag 300 by a predetermined value or more. In this case, the CPU 32 determines the radio tag 200 as the change target tag.

[0093] In S116, the CPU 32 executes a frequency change process for the change target tag determined in S114. Specifically, the CPU 32 changes the backscatter frequency of the change target tag so that the backscatter frequency of the change target tag is not adjacent to the backscatter frequency of the other wireless tags compared with the change target tag in S114. For example, in the case of (b) of Fig. 8, the CPU 32 exchanges the backscatter frequency of the wireless tag 200 with the backscatter frequency of the wireless tag 100. The CPU 32 transmits a first write command to the wireless tag 200 for writing a setting value corresponding to the backscatter frequency F1 to the wireless tag 200, and transmits a second write command to the wireless tag 100 for writing a setting value corresponding to the backscatter frequency F2 to the wireless tag 100. 8(c), the backscatter frequency of the wireless tag 200 is not adjacent to the backscatter frequency of the wireless tag 300, and the peak of the response of the wireless tag 300 is prevented from being hidden in the bottom of the response band of the wireless tag 200. Here, the backscatter frequency F2 is used for transmitting the first write command, and the backscatter frequency F1 is used for the second write command. It is possible to switch the backscatter frequencies of the wireless tags 100 and 200 while avoiding interference with wireless tags other than the wireless tags 100 and 200. When the process of S116 is completed, the CPU 32 returns to monitoring S20, S30, and S50.

[0094] (Modification of the fifth embodiment) The frequency change process is not limited to the process of replacing the backscatter frequency. For example, the backscatter frequency of the tag to be changed may be changed to a new frequency that is not assigned to any wireless tag other than the tag to be changed. In another modification, the backscatter frequency of the other wireless tag compared with the tag to be changed may be changed to a new frequency that is not assigned to any wireless tag other than the other wireless tag. In the above two modifications, the backscatter frequency of the tag to be changed is not adjacent to the backscatter frequency of the other wireless tag compared with the tag to be changed. In the above two modifications, the situation shown in FIG. 8(b) can be dealt with.

[0095] (Correspondence) The frequency F2 and the frequency F1 correspond to the "first backscattering frequency" and the "second backscattering frequency", respectively.

[0096] (Sixth Example) (Configuration of wireless tag 100; Fig. 10) The configuration of the wireless tag 100 of this embodiment will be described with reference to Fig. 10. The wireless tags 200 and 300 of this embodiment also have the same configuration as the wireless tag 100.

[0097] The wireless tag 100 of this embodiment includes a power supply circuit 120. The power supply circuit 120 is a circuit that generates power from radio waves transmitted by the tag communication device 10. A known technology is used for the power supply circuit 120, and a description thereof will be omitted here. Note that the power supply circuit 120 may also be provided in wireless tags other than that of this embodiment.

[0098] Moreover, the modulation unit 114 of this embodiment includes a first RF switch 144 and a second RF switch 150. The first RF switch 144 is a switching circuit that modulates the reflected wave into a response having a backscatter frequency according to the frequency setting value 140. The first RF switch 144 is also included in wireless tags other than that of this embodiment.

[0099] The second RF switch 150 is a switching circuit for adjusting the amplitude of the response. The second RF switch 150 is connected to the first RF switch 144 and selectively connects the path of the first RF switch 144 to one of three terminations 152, 154, and 156. The termination 152 is shorted, and a predetermined load is connected to the terminations 154 and 156. When a signal transmits to the termination 152, the signal is totally reflected. When a signal transmits to the termination 154, the signal is reflected with 1 / 2 the amplitude. When a signal transmits to the termination 156, the signal is reflected with 1 / 4 the amplitude. By adjusting the loads of the terminations 154 and 156, the ratio of the reflected wave to the incident wave incident on the termination is adjusted.

[0100] Furthermore, the memory 134 of this embodiment stores a switching set value 142. The switching set value 142 is a set value indicating one of the terminations 152, 154, and 156. The control unit 130 switches the second RF switch 150 in accordance with the switching set value 142.

[0101] Fig. 11(a) shows an example in which the environment in which the wireless tag 100 is placed has changed since streaming started, causing a change in the radio wave intensity of the wireless tag 100. As shown in Fig. 11(a), the radio wave intensity Y4 of the wireless tag 100 is greater than the radio wave intensity Y5 of the other wireless tags 200 and 300. As a result, the peaks of the streaming responses of the wireless tags 200 and 300 may be hidden in the tail of the band of the streaming response of the wireless tag 100. In the situation of Fig. 11(a), there is a possibility that the streaming responses of the wireless tags 200 and 300 cannot be identified. In this embodiment, it is intended to deal with the situation shown in Fig. 11(a).

[0102] (Processing of tag communication device 10; FIG. 12) The process in Fig. 12 is similar to the process in Fig. 3, except that the process of S120 is added, and the processes of S130 to S136 are executed instead of the processes of S30 to S42. In S120 following S18, the CPU 32 measures the radio wave intensity of the streaming response from each of all wireless tags communicating by streaming. The CPU 32 repeatedly measures the radio wave intensity of all wireless tags until the streaming is stopped in S52.

[0103] The CPU 32 executes monitoring of S130 in addition to S20 and S50. If there is a response having a radio wave intensity equal to or greater than a predetermined value among all responses from all wireless tags (YES in S130), the CPU 32 proceeds to S132. Note that the determination of whether the radio wave intensity is equal to or greater than a predetermined value may be based on a comparison of the radio wave intensity with a preset absolute value, or may be based on a relative comparison of two radio wave intensities corresponding to two wireless tags.

[0104] In S132, the CPU 32 determines a reset frequency to be used for writing in S136, which will be described later. The reset frequency is, for example, the same frequency as the backscatter frequency assigned to the wireless tag (hereinafter, referred to as the "tag to be adjusted") corresponding to the response having a radio wave intensity equal to or higher than a predetermined value.

[0105] In S134, the CPU 32 determines a switching value to be written to the switching setting value 142 of the tag to be adjusted. The CPU 32 classifies the radio wave strength of the tag to be adjusted into three levels, and determines a value indicating one of the ends 152, 154, and 156 as the switching value. For example, when the radio wave strength of the tag to be adjusted is classified as the maximum level, the CPU 32 determines the value indicating the end 156 as the switching value.

[0106] In S136, the CPU 32 transmits to the tag to be adjusted a write command for writing the switching value determined in S134 to the switching setting value 142. As a result, the switching setting value 142 of the tag to be adjusted is set to the switching value determined in S134. When S136 ends, the CPU 32 returns to monitoring S20, S50, and S130.

[0107] 11(a), the wireless tag 100 is the tag to be adjusted. For example, the wireless tag 100 receives a write command for writing a switching value indicating the end 154 to the switching setting value 142. This causes the radio wave intensity of the response from the wireless tag 100 to drop from Y4 to Y6. As a result, the peaks of the streaming responses from the wireless tags 200 and 300 are prevented from being hidden in the tail of the band of the streaming response from the wireless tag 100. Here, the reset frequency is used for the write command in S136, and the switching setting value 142 of the wireless tag 100 can be rewritten while avoiding interference with wireless tags other than the wireless tag 100.

[0108] (Correspondence) The switching set value 142 and the write command in S136 of FIG. 12 are examples of an "adjustment set value" and an "adjustment signal", respectively.

[0109] (Seventh Example) In the sixth embodiment, the switching set value 142 of the wireless tag 100 is changed in accordance with a write signal from the tag communication device 10. In contrast to this, the wireless tag 100 of this embodiment changes the switching set value 142 spontaneously.

[0110] The control unit 130 of this embodiment includes a power determination unit 170. The power determination unit 170 is a circuit that determines the level of radio wave intensity of the radio wave from the tag communication device 10. The power determination unit 170 is composed of, for example, a plurality of comparators. In this embodiment, the power determination unit 170 classifies the radio wave intensity of the radio wave from the tag communication device 10 into three levels, and writes a value indicating one of the terminals 152, 154, and 156 into the switching setting value 142. This allows the amplitude of the reflected wave of the radio wave from the tag communication device 10 (i.e., the streaming response) to be automatically adjusted.

[0111] If the radio wave strength of the radio waves from the tag communication device 10 is excessive, the radio wave strength of the streaming response may be greater than expected. Even in this case, as shown in (a) of FIG. 11, the peaks of the responses of the other wireless tags 200 and 300 may be hidden at the bottom of the band of the response of the wireless tag 100. According to this embodiment, the power determination unit 170 of the wireless tag 100 determines that the radio wave strength of the radio waves from the tag communication device 10 is excessive, and reduces the amplitude of the response below the default amplitude (i.e., the amplitude corresponding to the termination 152). This makes it possible to prevent the peaks of the responses of the wireless tags 200 and 300 from being hidden at the bottom of the band of the response of the wireless tag 100.

[0112] (Correspondence) The wireless tag 100, the memory 134, and the control unit 130 that controls the frequency setting value 140 are examples of a "specific wireless tag," a "memory," and a "storage control unit," respectively. The modulation unit 114 and the power determination unit 170 are examples of a "modulation unit" and a "determination unit," respectively.

[0113] Although specific examples of the technology disclosed in this specification have been described above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples exemplified above.

[0114] (Variation 1) The map 50 may be common to each wireless tag, or may be different for each wireless tag. The map 50 may be stored in the memory 134 of the wireless tag 100, and the tag communication device 10 may read the map 50 from the wireless tag 100.

[0115] (Modification 2) In the sixth and seventh embodiments, the number of paths that can be switched by the second RF switch 150 is not limited to three, and may be, for example, two, four or more. In other words, it is sufficient that the radio wave intensity of the response from the wireless tag 100 can be switched in multiple stages.

[0116] (Modification 3) In the fourth, fifth, and sixth embodiments, the wireless tag 100 receives a write command from the tag communication device 10 while transmitting a streaming response. For example, the wireless tag 100 may sample the write command and demodulate it by the demodulation unit 116 in accordance with the timing when the first RF switch 144 is controlled to the ON state. With this configuration, it is possible to suppress deformation of the demodulated waveform due to the influence of the ON / OFF switching of the first RF switch 144. The above technology is disclosed in detail in, for example, JP 2022-124621 A.

[0117] The technical elements described in this specification or drawings have technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technologies illustrated in this specification or drawings achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful. [Explanation of symbols]

[0118] 10: Tag communication device 12: Antenna section 14: Modulation section 16: Demodulation section 18: Filter section 30: Control section 34: Memory 40: Program 100, 200, 300: Wireless tag 112: Antenna section 114: Modulation section 116: Demodulation section 130: Control section 134: Memory 140: Frequency setting value 160: Sensor F1, F2, F3: Backscatter frequency F4: Reset frequency t1, t2, t3: Time 50: Map 120: Power supply circuit 142: Switching setting value 144: First RF switch 150: Second RF switch 152, 154, 156: Termination 170: Power judgment section X1, X2: Adjustment value P1, P2, P3, P4, Y1, Y2, Y3, Y4, Y5: Radio field strength Ft: Allocated frequency

Claims

1. A tag communication device capable of communicating with a plurality of wireless tags, a first communication execution unit that executes allocation communication with each of the plurality of wireless tags, the allocation communication being communication for assigning different backscatter frequencies to each of the plurality of wireless tags; a signal receiving unit that repeatedly transmits radio waves to each of the plurality of wireless tags after performing the allocation communication with each of the plurality of wireless tags, and receives a signal having the backscatter frequency assigned to the wireless tag from each of the plurality of wireless tags; a second communication execution unit that, when it is determined that an abnormality has occurred in a specific wireless tag among the plurality of wireless tags in the signal communication with the plurality of wireless tags, executes a countermeasure communication with the specific wireless tag to counter the abnormality by using a specific frequency different from any of the backscatter frequencies assigned to one or more wireless tags other than the specific wireless tag among the plurality of wireless tags; A tag communication device comprising:

2. The tag communication device according to claim 1 , wherein the second communication execution unit executes the allocation communication with the specific wireless tag as the countermeasure communication when it is determined that the signal communication with the specific wireless tag has been interrupted.

3. The tag communication device of claim 2, wherein the second communication execution unit, by executing the assigned communication with the specific wireless tag, assigns to the specific wireless tag the backscatter frequency that is the same as the backscatter frequency that was assigned to the specific wireless tag before it was determined that the signal communication with the specific wireless tag was interrupted.

4. The tag communication device further includes: a demodulation unit that demodulates the signals received from each of the plurality of wireless tags; a first determination unit that determines that communication of the signal with the specific wireless tag has been interrupted when a demodulation success rate per unit time of the signal from the specific wireless tag falls below a predetermined first value; The tag communication device according to claim 2 .

5. The tag communication device further includes: a transmitting unit that transmits a specific command different from the radio waves to each of the plurality of radio tags while repeatedly transmitting the radio waves to each of the plurality of radio tags; a second determination unit that determines that the signal communication with the specific wireless tag has been interrupted when a response to the specific command is received from the specific wireless tag while the radio waves are being repeatedly transmitted to each of the plurality of wireless tags; The tag communication device according to claim 2 .

6. The tag communication device further includes: The tag communication device according to claim 2 , further comprising a third judgment unit that judges that communication of the signal with the specific wireless tag has been interrupted when the radio wave strength of the signal from the specific wireless tag falls below a predetermined second value.

7. the allocation communication includes transmitting a command to the specific wireless tag to write a first setting value indicating the backscatter frequency to be allocated to the specific wireless tag to the specific wireless tag; The tag communication device further includes: a determination unit that determines a second setting value to be written to the specific wireless tag in place of the first setting value by using a map corresponding to the radio wave intensity of the signal from the specific wireless tag; the map indicates a correlation between the backscatter frequency to be assigned to the specific wireless tag and a setting value to be written to the specific wireless tag; The tag communication device according to claim 1 , wherein the countermeasure communication includes transmitting, to the specific wireless tag, a command for writing the second setting value to the specific wireless tag, using the specific frequency.

8. In the allocation communication, a first backscatter frequency is allocated to the specific wireless tag, and a second backscatter frequency adjacent to the first backscatter frequency is allocated to other wireless tags among the plurality of wireless tags that are different from the specific wireless tag; the countermeasure communication includes transmitting, when a radio wave intensity of a signal from the specific wireless tag is greater than a radio wave intensity of a signal from the other wireless tag by a predetermined value or more, to the specific wireless tag by using the specific frequency to change a backscatter frequency; 2. The tag communication device according to claim 1, wherein after the countermeasure communication is executed, the backscatter frequency assigned to the specific wireless tag and the backscatter frequency assigned to the other wireless tags are not adjacent to each other.

9. Each of the plurality of wireless tags stores an adjustment setting value for adjusting the radio wave intensity of a signal to the tag communication device, the countermeasure communication includes transmitting an adjustment signal to the specific wireless tag by using the specific frequency when a radio wave intensity of a signal from the specific wireless tag is greater than or equal to a predetermined value a radio wave intensity of signals from other wireless tags other than the specific wireless tag among the plurality of wireless tags; The tag communication device according to claim 1 , wherein the adjustment signal is a signal for changing the adjustment setting value in the specific wireless tag to lower the radio wave intensity of the signal from the specific wireless tag.

10. the specific frequency is a specific backscatter frequency that is the backscatter frequency that was assigned to the specific wireless tag before it was determined that an abnormality occurred in the signal communication with the specific wireless tag, The tag communication device according to claim 1 , wherein the specific frequency band is narrower than the specific backscatter frequency band.

11. A tag communication device described in any one of claims 1 to 9, wherein the specific frequency is a frequency different from any of the backscatter frequencies assigned to each of the multiple wireless tags before it is determined that an abnormality has occurred in the signal communication with the specific wireless tag.

12. A specific wireless tag capable of communicating with a tag communication device, Memory, a storage control unit that executes allocation communication with the tag communication device and stores a setting value indicating a specific backscatter frequency in the memory; a modulation unit that modulates a reflected wave of a radio wave from the tag communication device into a signal having the specific backscatter frequency in accordance with the setting value in the memory after the allocation communication with the tag communication device is executed; a determination unit that determines whether or not the strength of the radio wave from the tag communication device is equal to or greater than a specific value; Equipped with A specific wireless tag in which the modulation unit lowers the radio wave strength of the reflected wave below the default and modulates the reflected wave into the signal when the strength of the radio waves from the tag communication device is determined to be greater than or equal to the specific value.

Images