Tag communication device

Abstract

To provide a technique for promptly executing an allocation of a backscatter frequency to each of a plurality of wireless tags.SOLUTION: A tag communication device comprises: an allocation section which writes a setting value to each of a plurality of wireless tags, thereby allocating a mutually different backscatter frequency to each of the plurality of wireless tags; and a signal reception section which iteratively transmits a radio wave to each of the plurality of wireless tags and receives from each of the plurality of wireless tags a signal having the backscatter frequency allocated to the wireless tag. The allocation section transmits a radio wave to each of the plurality of wireless tags, measures an intensity of a reflection wave with respect to the radio wave and utilizes a map corresponding to the measured intensity regarding each of the plurality of wireless tags to determine a setting value corresponding to an allocation frequency of a backscatter frequency that should be allocated to the wireless tag. The map indicates a correlation between the allocation frequency and the setting value.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 wireless communication system that transmits radio waves to a plurality of wireless tags and receives signals having a backscatter frequency from each of the wireless tags. The wireless communication system assigns different backscatter frequencies to each of the 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] The wireless tag includes an oscillator circuit for generating a signal having a backscatter frequency. The oscillator circuit operates at a desired frequency by changing the setting value of the oscillator circuit. However, even if the setting value of the oscillator circuit is set to a predetermined design value, the frequency at which the oscillator circuit actually operates may deviate from the frequency corresponding to the design value. In this case, the actual backscatter frequency deviates from the backscatter frequency to be assigned to the wireless tag.

[0005] For example, a feedback method is envisaged in which the set value of the oscillator is repeatedly adjusted to bring the actual backscatter frequency closer to the backscatter frequency to be assigned to the wireless tag, but this method requires a relatively long time to adjust the set value.

[0006] The present specification provides a technique for quickly allocating backscatter frequencies to each of a plurality of wireless tags. [Means for solving the problem]

[0007] This specification discloses a tag communication device capable of communicating with a plurality of wireless tags, the tag communication device including: an allocation unit that allocates different backscatter frequencies to each of the plurality of wireless tags by writing a setting value to each of the plurality of wireless tags; and a signal receiving unit that repeatedly transmits radio waves to each of the plurality of wireless tags after the different backscatter frequencies are allocated to each of the plurality of wireless tags, and receives signals having the backscatter frequencies allocated to the wireless tags from each of the plurality of wireless tags, the allocation unit transmits radio waves to each of the plurality of wireless tags, measures the strength of the reflected waves to the radio waves, and determines the setting value corresponding to the allocation frequency, which is the backscatter frequency to be allocated to the wireless tag, for each of the plurality of wireless tags by using a map corresponding to the measured strength, the map indicating the correlation between the allocation frequency and the setting value.

[0008] In experiments, it was found that when the strength of the reflected wave from the wireless tag indicates a certain value, a correlation exists between the assigned frequency and the frequency setting value. According to the above configuration, the tag communication device measures the strength of the reflected wave. Then, the tag communication device can use a map corresponding to the measured strength of the reflected wave to determine the setting value corresponding to the assigned frequency. By using the map, the allocation of the backscatter frequency can be performed quickly.

[0009] The tag communication device may include a memory for storing the map.

[0010] According to the above configuration, the map can be quickly called up from its own memory.

[0011] Each of the plurality of wireless tags may store the map corresponding to that wireless tag, and the allocation unit may read out the map from each of the plurality of wireless tags.

[0012] For example, there are cases where the correlations are different for each of the multiple wireless tags. According to the above configuration, it is sufficient to read out the map from each of the multiple wireless tags, and it is not necessary to store a different map for each of the multiple wireless tags in the tag communication device. For example, even if a new wireless tag is added, it is not necessary to newly store a map corresponding to that wireless tag in the tag communication device 10. It is possible to easily deal with a situation where the correlations are different for each of the multiple wireless tags. [Brief description of the drawings]

[0013] [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] 4 is a flowchart of a process executed by the tag communication device according to the first embodiment. FIG. [Figure 4] FIG. 11 is a diagram showing a setting value map according to the second embodiment. [Diagram 5] FIG. 11 is a flowchart of a process executed by a tag communication device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] (First embodiment) (Configuration of tag communication device 10; Figure 1) The tag communication device 10 is a device capable of communicating with a plurality of wireless tags 100 and 200. Although two wireless tags 100 and 200 are illustrated in Fig. 1, the number of wireless tags is not limited to two and may be three or more. The wireless tag is, for example, a Radio Frequency Identification (RFID) tag.

[0015] The tag communication device 10 includes an antenna unit 12, a modulation unit 14, a demodulation unit 16, 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.

[0016] The modulation unit 14 is a circuit that modulates a UHF band carrier wave and supplies it to the antenna unit 12. The modulation unit 14 can also supply a UHF band carrier wave to the antenna unit 12 without modulating it. In the following, a modulated carrier wave is referred to as a "modulated wave" and an unmodulated carrier wave is referred to as an "unmodulated wave". The demodulation unit 16 is a circuit that demodulates a reflected wave received by the antenna unit 112 and supplies it to the control unit 30. The configurations of the modulation unit 14 and the demodulation unit 16 may be, for example, known configurations, and detailed description thereof will be omitted in this specification.

[0017] The control unit 30 is a circuit that controls 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.

[0018] The control unit 30 is provided in a memory 34. The memory 34 includes a volatile memory and a non-volatile memory. The memory 34 stores a setting value map 50. The setting value map 50 is used to determine the backscatter frequency to be assigned to each wireless tag. The setting value map 50 will be described in detail later.

[0019] (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 200 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] The control unit 130 is connected to the sensor 160. The sensor 160 is, for example, a sensor that measures vibration. The measurement values ​​measured by the sensor 160 are stored in the memory 134.

[0025] Each of the units 112, 114, 116, and 130 of the wireless tag 100 operates using the power of a carrier wave. The wireless tag 100 is a so-called passive tag. The wireless tag 200 has a similar configuration to the wireless tag 100, and stores a tag ID "t02" that identifies the wireless tag 200.

[0026] (Communication between tag communication device 10 and wireless tag 100) With reference to Fig. 2, the 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.

[0027] 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.

[0028] 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.

[0029] 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. The specific value is determined by the process of FIG. 3 described later. 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.

[0030] 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.

[0031] 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.

[0032] Communications from T2 to T12C are also performed with another wireless tag 200. Here, at T6, a backscatter frequency different from that of the wireless tag 100 is assigned to the wireless tag 200. By assigning different backscatter frequencies to the wireless tag 100 and the wireless tag 200, 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 tag 100 and the wireless tag 200. In other words, the measurement value of the wireless tag 100 can be synchronized with the measurement value of the wireless tag 200.

[0033] (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.

[0034] 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 and 200). For example, the assigned frequency to the wireless tag 100 is determined to be 920 MHz+100 kHz, and the assigned frequency to the wireless tag 200 is determined to be 920 MHz+140 kHz.

[0035] 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.

[0036] In S20, the control unit 30 measures the received power of the reflected wave received from each wireless tag in the inventory in S12. The unit of the received power is, for example, dBm.

[0037] In S22, the control unit 30 uses the setting value map 50 to determine the setting value to be written to each of the multiple wireless tags. An example of the setting value map 50 is shown in FIG. 3. The setting value map 50 is generated in advance based on an experiment. In the experiment, it was found that a correlation exists between the assigned frequency and the setting value when the received power of the reflected wave from the wireless tag indicates a certain value. For example, a positive correlation shown in FIG. 3 is obtained for each of the received powers P1 to P4. Note that the correlation is not limited to the linear relationship shown in FIG. 3, and may be a nonlinear relationship.

[0038] For example, when the assigned frequency Ft is assigned to the wireless tag 100 in S10 and the received power measured in the wireless tag 100 in S20 is P4, the control unit 30 uses the correlation of the received power P4 to determine the set value X1 for the wireless tag 100. Also, when the assigned frequency Ft is assigned to the wireless tag 100 in S10 and the received power measured in the wireless tag 100 in S20 is P3, the control unit 30 uses the correlation of the received power P3 to determine the set value X2 for the wireless tag 100. In this embodiment, the correlation corresponding to the wireless tag 100 is the same as the correlation corresponding to the wireless tag 200. The same set value map 50 is used for all of the multiple wireless tags 100 and 200.

[0039] In S24, the control unit 30 transmits a write command to each of the multiple wireless tags. The write command includes the tag ID of the destination wireless tag and the setting value determined in S22. The process of S24 executes the communications of T6 and T8 in Fig. 2, and the control unit 30 writes the setting value to each wireless tag. Note that the process of S24 is repeatedly executed for all wireless tags until the error between the frequency of the reflected wave from the wireless tag and the assigned frequency determined in S10 falls within the allowable range.

[0040] In S26, the control unit 30 measures the actual frequency of the reflected wave received from each of the multiple wireless tags. For example, the control unit 30 transmits a modulated wave with a designated destination to each wireless tag and measures the frequency of the reflected wave of the modulated wave.

[0041] In S28, the control unit 30 judges whether or not the error between the frequency measured in S26 and the assigned frequency determined in S10 is within the allowable range. When the control unit 30 judges that the error is within the allowable range for all of the multiple wireless tags (YES in S28), the control unit 30 proceeds to S32. In S32, the control unit 30 transmits a streaming start command to each wireless tag. This starts streaming, and the measurement value of the sensor 160 is repeatedly received from each wireless tag. The process of S32 executes communications T10 to T12C in FIG. 2. When the process of S32 ends, the control unit 30 ends the process of FIG. 3.

[0042] Furthermore, when the control unit 30 determines that the error is outside the allowable range for at least one of the multiple wireless tags (NO in S28), it proceeds to S30. In S30, the control unit 30 determines whether the number of times the process of S24 has been executed (hereinafter referred to as the "number of writes") has reached a predetermined number. When the control unit 30 determines that the number of writes has reached the predetermined number (NO in S30), it skips the process of S32 and ends the process of Fig. 3. In this case, for example, the control unit 30 notifies the user of an error.

[0043] Furthermore, when the control unit 30 determines that the number of times writing has not reached the predetermined number of times (YES in S30), the process returns to S20. This causes the setting value to be written again. Note that the setting value may be written again to all wireless tags, or may be written again only to wireless tags determined to have an error outside the allowable range.

[0044] (Effects of this embodiment) By changing the setting value of the oscillator circuit, i.e., the frequency setting value 140, the oscillator circuit operates at a desired frequency. However, even if the setting value of the oscillator circuit is set to a predetermined design value, the frequency at which the oscillator circuit actually operates may deviate from the frequency corresponding to the design value. This is because, for example, the environment in which the wireless tag is placed (e.g., temperature, etc.) affects the characteristics of the oscillator circuit. In this case, the actual backscatter frequency deviates from the assigned frequency.

[0045] For example, a feedback method may be used in which the actual backscatter frequency is adjusted to the assigned frequency by repeatedly adjusting the setting value of the oscillator circuit, but this method requires a relatively long time to adjust the setting value.

[0046] In contrast, according to the configuration of this embodiment, the tag communication device 10 can determine the setting value corresponding to the assigned frequency by using the setting value map 50 corresponding to the received power of the measured reflected wave (S22). By using the setting value map 50, the backscatter frequency can be quickly assigned.

[0047] Furthermore, in this embodiment, the setting value map 50 is stored in the memory 34 of the tag communication device 10. This allows the setting value map 50 to be quickly called up from its own memory 34.

[0048] (Correspondence) The wireless tags 100 and 200 are examples of "multiple wireless tags." The tag communication device 10, the memory 34, and the setting value map 50 are examples of a "tag communication device," a "memory," and a "map," respectively. The setting value X1 is an example of a "setting value." The control unit 30 that executes S20 to S24 in Fig. 3 and the control unit 30 that executes S32 are examples of an "assignment unit" and a "signal receiving unit," respectively.

[0049] (Second Example) This embodiment is similar to the first embodiment, except that a setting value map 150 is stored in each wireless tag and the processing of the tag communication device 10 is different.

[0050] (Configuration of wireless tags 100 and 200; FIG. 1) In this embodiment, the wireless tags show different correlations with each other. As shown in Fig. 1, a setting value map 150 corresponding to the wireless tag 100 is stored in the memory 134 of the wireless tag 100. In addition, a setting value map 150 corresponding to the wireless tag 200 is stored in the memory 134 of the wireless tag 200.

[0051] (Setting value map 150; Figure 4) 4, for the received power P1, multiple wireless tags (for example, four wireless tags corresponding to tag IDs "t01" to "t04") show different correlations with each other. For other received powers, for example, the received power P2, multiple wireless tags also show different correlations with each other.

[0052] (Processing of tag communication device 10; FIG. 5) With reference to Fig. 5, the process executed by the control unit 30 of the tag communication device 10 according to the program 40 will be described. S110 and S112 are similar to S10 and S12 in Fig. 3. In S14, the control unit 30 transmits a read command to each wireless tag for reading the setting value map 150 from each wireless tag. The read command is a command specifying a destination, and includes the tag ID acquired in S112. As a result, the control unit 30 receives reflected waves carrying the setting value map 150 from each wireless tag, and reads the setting value map 150 from each wireless tag.

[0053] S120 to S132 are similar to S20 to S32 in FIG. 3, except that in S120, the received power of the reflected wave of the read command in S114 is measured, and in S122, the setting value map 150 read in S114 is used.

[0054] According to the configuration of this embodiment, it is only necessary to read out the setting value map 150 from each of the multiple wireless tags, and it is not necessary to store a different setting value map 150 for each of the multiple wireless tags in the tag communication device 10. For example, even if a new wireless tag is added, it is not necessary to newly store a setting value map 150 corresponding to that wireless tag in the tag communication device 10. It is possible to easily deal with a situation in which the correlations differ among the multiple wireless tags. The setting value map 150 is an example of a "map".

[0055] (Applications of the technology disclosed herein) The technology disclosed in this specification can be used, for example, to attach wireless tags with sensors 160 to multiple locations on a structure and simultaneously measure vibrations at the multiple locations. The structure can be, for example, a building, a bridge, or other structure, or a product such as an automobile. The physical quantity to be measured is not limited to vibration, and can be other physical quantities such as speed and current, and this technology can be used for purposes other than vibration measurement of a structure.

[0056] 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 variations of the specific examples exemplified above. For example, the following modifications may be adopted.

[0057] (Modification 1) Even if the correlations are the same for each of a plurality of wireless tags, the setting value map may be stored in each wireless tag.

[0058] (Modification 2) The "strength of the reflected wave" is not limited to the received power, but may be, for example, a Received Signal Strength Indicator (RSSI).

[0059] 3 in the first embodiment, the control unit 30 may separately transmit a command different from the inventory in S12 and measure the received power of the reflected wave of the command. Also, in S120 in Fig. 3 in the second embodiment, the control unit 30 may separately transmit a command different from the read command in S114 and measure the received power of the reflected wave of the command.

[0060] 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]

[0061] 10: Tag communication device 12: Antenna section 14: Modulation section 16: Demodulation section 30: Control section 34: Memory 40: Program 50: Setting value map 100: Wireless tag 112: Antenna section 114: Modulation section 116: Demodulation section 130: Control section 134: Memory 140: Frequency setting value 150: Setting value map 160: Sensor 200: Wireless tag Ft: Allocated frequency P1~P4: Received power X1, X2: Setting value

Claims

1. A tag communication device capable of communicating with a plurality of wireless tags, an allocation unit that allocates different backscatter frequencies to each of the plurality of wireless tags by writing a setting value to each of the plurality of wireless tags; a signal receiving unit that, after each of the plurality of wireless tags is assigned a different backscatter frequency, repeatedly transmits radio waves to each of the plurality of wireless tags and receives, from each of the plurality of wireless tags, a signal having the backscatter frequency assigned to that wireless tag; Equipped with The allocation unit: transmitting radio waves to each of the plurality of wireless tags and measuring the strength of the reflected waves of the radio waves; determining, for each of the plurality of wireless tags, the setting value corresponding to an assigned frequency, which is the backscatter frequency to be assigned to the wireless tag, using a map corresponding to the measured strength; The map indicates a correlation between the assigned frequency and the setting value. Tag communication device.

2. The tag communication device according to claim 1 , further comprising a memory for storing the map.

3. Each of the plurality of wireless tags stores the map corresponding to the wireless tag; The tag communication device according to claim 1 , wherein the allocation unit reads out the map from each of the plurality of wireless tags.

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