TAG READER AND TAG READING SYSTEM

According to one embodiment, a tag reader comprises a communication interface connectable to an external device, a communication control circuit configured to output a tag interrogation signal at different output levels from an antenna and receive a tag response signal via the antenna, and a processor. The processor is configured to notify the external device, via the communication interface, of an output level of the tag interrogation signal corresponding to a received tag response signal from a wireless tag, a tag identification of the wireless tag included in the received tag response signal, and an indication of a signal strength of the received tag response signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2020-029095, filed on Feb. 25, 2020, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a tag reader and a tag reading system.

BACKGROUND

There is a tag reading system for reading an RFID tag, which can also be referred to as a wireless tag. The RFID tag can be read while at an unspecified position within range of the tag reading system. There is a tag reading system that detects a change in a relative position of an RFID tag (with respect to a tag reader) by detecting a change in a strength of the signal that the tag reader receives from the RFID tag.

The tag reader reads the RFID tag by receiving a response signal from an RFID tag that has been activated by an interrogation radio wave from the tag reader. In such a reading process, some tag readers may adjust the strength of the interrogation radio wave output from the reader. However, if the strength of the signal output by the tag reader (the interrogation wave) is unknown, it can be difficult to detect a change in the relative position of the RFID tag by detecting changes in the strength of the signal received from the RFID tag (the response wave).

DETAILED DESCRIPTION

According to one embodiment, a tag reader comprises a communication interface connectable to an external device, a communication control circuit configured to output a tag interrogation signal at different output levels from an antenna and receive a tag response signal via the antenna, and a processor. The processor is configured to notify the external device, via the communication interface, of an output level of the tag interrogation signal corresponding to a received tag response signal from a wireless tag, a tag identification of the wireless tag included in the received tag response signal, and an indication of a signal strength of the received tag response signal.

Hereinafter, certain example embodiments will be described with reference to the drawings.

First, a configuration of a tag reader10and a tag reading system1incorporating the tag reader10according to an embodiment will be described.FIG. 1is a block diagram schematically illustrating a configuration example of a tag reading system1including a tag reader10according to an embodiment. As shown inFIG. 1, the tag reading system1includes the tag reader10and a host device11. In the tag reading system1, the tag reader10reads RFID tags (wireless tags). The host device11detects a change in the relative position of the RFID tag with respect to the tag reader10based on the continuously performed readings from the tag reader10. In general, when the position of the tag reader10is fixed or substantially so, the change in relative position of the RFID tag can be considered to be caused by movement of the RFID tag.

For example, the tag reading system1is operated as a search system for searching for an article to which an RFID tag has been attached. The tag reading system1may be designed to search within or cover an area such as a warehouse or a retail store. For a tag reading system1operating as the search system, the tag reader10continuously attempts to read RFID tags. The host device11acquires reading results for each RFID tag that has been read from the tag reader10and detects a change in a relative position between the tag reader and the RFID tag based on the acquired reading result. The reading result of the RFID tag also includes information indicating the strength of a reception signal received by the tag reader from the RFID tag. The host device11detects a change in the relative position between the tag reader and the RFID tag based on a change in the strength of the received signal in time series.

In the present embodiment, it is assumed that the tag reader10continuously attempts to read RFID tags attached to articles such as commodities for sale. The host device11detects the change of the relative position between the tag reader and a RFID tag from the reading results from the RFID tag over time. Depending on the particular tag reading system1, the tag reader10may be fixed or moveable. For example, a moveable tag reader10may be a hand-held type device or may be mounted on a moving body. In any event, the host device11detects a change in relative position between the tag reader and the RFID tag based on the reading results for the RFID tag acquired by the tag reader10.

The tag reader10receives a response signal from the RFID tags present within a communication range by wireless communication. The response signal from each RFID tag includes information (tag information) that has been stored in the RFID tag.

The tag reader10transmits a radio wave for requesting a response from the RFID tag. This radio wave (referred to as an interrogation signal) is output at a strength (output value) that can be set for each RFID tag type or the like. The tag reader10receives a response signal from an RFID tag in response to the interrogation signal. That is, the tag reader10receives a response signal including the tag information from any RFID tag activated by the interrogation signal within the communication range of the tag reader10. When multiple RFID tags are within the communication range, the tag reader receives a different response signal (different tag information) from each of the RFID tags.

The tag reader10measures an RSSI value indicating a strength of a response signal received from an RFID tag. The tag reader10supplies the tag information included in the response signal from each RFID tag to the host device11together with the corresponding RSSI value for the tag as the reading result of the RFID tag. The tag reader10may also include, in the reading result for each RFID tag, an output value for the interrogation signal when the response signal was received.

The RFID tag can be attached to an article such as a commodity for sale, or a component being tracked in a warehouse or supply chain. The information stored in the RFID tag (the tag information) can include information for identifying the article (e.g., a tag identification number) or the like. The information stored in the RFID tag is recorded in an internal memory of the RFID tag. The RFID tag is activated by radio waves from the tag reader10. The RFID tag outputs a response signal including the tag information recorded in its memory in response to a read command received from the tag reader10. The RFID tag is powered by the radio waves received from the tag reader10. Therefore, the strength of the response signal output by the RFID tag can be affected by the strength of the interrogation signal transmitted from the tag reader10.

The host device11is an information processing terminal communicably connected to the tag reader10. For example, the host device11is an information processing terminal such as a smartphone or a tablet PC including a display device with a touch panel as a user interface. The host device11may be an information processing device installed at any position as long as it has a communication interface capable of communicating with the tag reader from the position.

In the configuration example illustrated inFIG. 1, the host device11includes a processor12, a memory13, a communication interface (I/F)14, a display device15, an input device16, and the like. The processor12performs overall control processing overall, data processing, and the like. The processor12is, for example, a CPU. The processor12executes a program stored in the memory13to realize various operations and functions. For example, the processor12detects the movement of an RFID tag (or the change in the relative position between the tag reader10and the RFID tag) based on the reading results of the RFID tag acquired from the tag reader10. These processes are realized by the processor12executing an application program installed in the memory13.

The communication I/F14is an interface for communicating with an external device. In the present embodiment, the communication I/F14is an interface for communicating with the tag reader10. The communication I/F14may be an interface for wired communication or an interface for wireless communication. For example, the communication I/F14can be realized by a LAN interface, a universal serial bus (USB) interface, a Bluetooth® interface, a Wi-Fi interface, or the like.

The display device15displays information. For example, the display device15displays detection results concerning the RFID tag (for example, indicates a movement of the RFID tag). The input device16receives operator/user inputs indicating an operation instruction or the like. The display device15and the input device16can be integrated and provided, for example, as a display device with a touch panel.

In the configuration example illustrated inFIG. 1, the tag reader10includes a processor21, ROM22, RAM23, a communication control circuit24, an antenna25, a communication interface (I/F)26, a display device27, and a power supply28.

The processor21provides overall control of the tag reader10. The processor21includes, for example, an arithmetic circuit such as a CPU. The processor21implements control of each unit and various types of data processing by executing a program. The processor21may include an internal memory. The processor21implements various processes by executing a program stored in the ROM22or the internal memory. For example, the processor21interprets commands from the host device11received by the communication I/F26and executes a process corresponding to each received command.

The ROM22is a non-rewritable nonvolatile memory. The ROM22stores a program executed by the processor21and the like. The RAM23is a volatile memory that stores data. For example, the RAM23functions as a working memory or a buffer memory. The RAM23has a buffer memory31for storing the reading result of the RFID tag. The tag reader10may include a rewritable nonvolatile memory such as a hard disk drive (HDD) or a solid-state drive (SSD).

The communication control circuit24and the antenna25can be considered to form an RFID communication interface for reading or communicating with an RFID tag. The communication control circuit24causes the antenna25to transmit a transmission signal (radio wave) supplied from the processor21at a set output value. The antenna25outputs the transmission signal supplied from the communication control circuit24as a radio wave that can be received by the RFID tag.

The communication control circuit24also supplies a signal received by the antenna25to the processor21as reception data. That is, the antenna25receives a response signal from the RFID tags, and the communication control circuit24processes the response signal received by the antenna25and then supplies the response signal to the processor21. For example, the communication control circuit24supplies the tag information included in a reception signal and an RSSI value indicating the strength of the reception signal to the processor21.

The communication I/F26is an interface for communicating with an external device. In the tag reading system1, the communication I/F26is a communication interface for communicating with the host device11. The communication I/F26may be an interface for communication connection with the host device11. The communication I/F26may be an interface for wired communication or an interface for wireless communication. For example, the communication I/F26can be realized by a LAN interface, a universal serial bus (USB) interface, a Bluetooth® interface, a Wi-Fi interface, or the like.

The display device27displays the operation state of the tag reader10. The display device27can be, for example, an LED or the like. The power supply28supplies power for operating the tag reader10. The power supply28supplies power for operation to each unit of the tag reader10. For example, if the tag reader is a hand-held or other mobile type, the power supply28can be realized by a rechargeable battery. If the tag reader10is of a stationary type connectable to a commercial power supply, the power supply28can be a power supply circuit connected to the commercial power supply.

In the configuration example shown inFIG. 1, the communication control circuit24includes a modulation unit41, a transmission-side amplification unit42, a direction coupler43, a reception-side amplification unit44, a demodulation unit45, an output setting unit46, a level detection unit47, and a thermistor48.

The modulation unit41is a modulation circuit (modulator) that modulates a waveform signal (carrier wave) according to input data. The modulation unit41modulates a carrier wave with transmission data as supplied from the processor21. The transmission-side amplification unit42is an amplification circuit (amplifier) that amplifies the input signal received from the modulation unit41. The direction coupler43includes a circuit that supplies the signal output from the transmission-side amplifier42to the antenna25. Thus, the communication control circuit24outputs from the antenna25a carrier wave modulated by transmission data.

The RFID tags receive the radio waves transmitted from the antenna25. The RFID tag receives, for example, a read command included in a signal received from the antenna25. When the RFID tag responds to the read command, the RFID tag outputs data (tag information) stored in the memory of the RFID tag, for example, by backscatter modulation.

The antenna25then receives radio waves output by the RFID tag(s). The direction coupler43includes a circuit that acquires the reception signal received by the antenna25and supplies the acquired reception signal to the reception-side amplification unit44. The reception-side amplification unit44is an amplification circuit (amplifier) that amplifies the input signal. Here, the reception-side amplification unit44amplifies a reception signal received by the antenna25. The demodulation unit45is a demodulation circuit (demodulator) that demodulates the data superimposed on a waveform signal (carrier wave). The demodulator45, in effect, decodes data (tag information) included in the reception signal as amplified and output by the reception-side amplification unit44.

The antenna25may both transmit and receive radio waves to and from the RFID tag. That is, the antenna25may transmit a signal to be supplied to the RFID tag and also receive a radio wave output from the RFID tag. In the present embodiment, the antenna25is positioned to transmit electromagnetic waves toward a particular reading area. The tag reader10is configured to communicate with the RFID tags on items or commodities disposed in this reading area of the antenna25. The antenna25is, for example, a planar antenna. However, the antenna25is not necessarily limited to any specific configuration.

The output setting unit46is a circuit that sets a strength (output value) of a signal to be output from the tag reader10. The output setting unit46performs control so that the strength of a signal output to the amplification unit42matches a set output value. In particular, the amplification unit42amplifies the signal supplied from the modulation unit41so as to have the output value (signal strength) as set by the output setting unit46, and outputs this amplified signal to the directional coupler43. Thus, the antenna25transmits an output signal (radio wave) having an output value as set by the output setting unit46.

The level detection unit47is a signal level detection circuit that detects, measures, or calculates a strength of a signal received by the antenna25. The level detection unit47detects the strength of a signal that is input to the reception-side amplification unit44from the direction coupler43. That is, the level detection unit47is configured to detect an RSSI value indicating the strength of a response signal from the wireless tag as received by the antenna25.

The thermistor48is a measuring instrument that measures temperature. The thermistor48detects, for example, a temperature in the communication control circuit24. The thermistor48provides information indicative of the sensed temperature to processor21. The processor21executes operation control such as communication control according to the temperature as detected by the thermistor48.

FIG. 2is a diagram illustrating a configuration example of a smart shelf system101(referred to below as smart shelf101, for simplicity). The smart shelf101incorporates a tag system of an embodiment. In the configuration example shown inFIG. 2, a tag reader110is a modification of the tag reader10and includes the internal configuration of tag reader10shown inFIG. 1. Host device111is a modification of the host device11and includes, in general, the internal components of host device11shown inFIG. 1.

The smart shelf101is a system for reading an RFID tag T attached to articles A placed at predetermined positions S. Each predetermined position S is, for example, a shelf within range of the tag reader110. The tag reader110is used for reading the RFID tags T. In the smart shelf101, the host device111detects the movement of the RFID tags T (on the articles Abased on the reading result obtained by the tag reader110reading the RFID tags T. Since each RFID tag T is attached to an article A, detected movement of a RFID tag T corresponds to movement of an article A.

The host device111acquires an RSSI value indicating the strength of a signal received from the RFID tag T from the tag reader110and detects the movement of a RFID tag T by a change in the RSSI value. However, the strength of the signal received by the tag reader110from the RFID tag T also changes depending on the strength of the interrogation wave output by the tag reader110. Therefore, the host device111acquires the output value for the interrogation wave from when the tag reader110read the RFID tag T, and thus detects movement of the RFID tag T by changes in the RSSI adjusted by the corresponding output value of the interrogation wave.

FIG. 3is a diagram for explaining a configuration example of an RFID tag search system201according to an embodiment. In the configuration example shown inFIG. 2, a tag reader210is a modification of the tag reader10and includes the internal components of tag reader10shown inFIG. 1. Host device211is a modification of the host device11and includes, in general, the internal components of host device11shown inFIG. 1.

The search system201shown inFIG. 3includes a hand-held tag reader210and a host device211connected to the tag reader210. The tag reader210shown inFIG. 3includes the internal configuration of the tag reader10, depicted inFIG. 1, along with external configurations for a gripping part221to be gripped by an operator and a holding part222for holding the host device211.

In the tag reader210, an operator holds the gripping part221while the host device211is set in (held by) the holding portion222. The holding part222is, for example, one or more clips, clamps, or the like. The host device211includes a display device231with a touch panel corresponding to the display device15and the input device16of host device11in combination. For example, the host device211is implemented by a portable information terminal such as a smartphone or a tablet

The search system201can be used to search for an RFID tag by an operator holding and moving the tag reader210about with the host device211set therein. The search system201reads RFID tags while the operator moves the tag reader210around, and then supplies the reading results to the host device211.

The host device211acquires an RSSI value indicating the strength of a signal received from an RFID tag as a reading result of the RFID tag from the tag reader210. The host device211detects a change in the relative position between the tag reader210and the RFID tag as a change in the RSSI value included in the reading result of the RFID tag. Also, in this case, the strength (RSSI value) of the signal received by the tag reader210from the RFID tag varies with the variation of the strength (output value) of the interrogation wave output from the tag reader210. The host device211thus also acquires the output value of the interrogation wave corresponding to when the tag reader210acquired the response signal from RFID tag. The host device211is thus able to detect the movement the RFID tag(s) by the change in the RSSI value adjusted based on the interrogation wave signal strength (output value). The host device211displays the detection results of an RFID tag on display device231.

Next, a reading result from the RFID tag as stored in the buffer memory31by the tag reader10will be described.FIG. 4is a diagram illustrating an example of reading results stored in the buffer memory31as read by the tag reader10according to an embodiment. The buffer memory31stores an output value (an interrogation signal strength), a tag information (ID), and an RSSI value for each RFID tag that has been detected/read.

In this context, the “output value” is a strength of a radio wave output from the antenna25when the RFID tag was read. The output value is set by the output setting unit46of the communication control circuit24in accordance with an instruction from the processor21. Therefore, the output value can be known for any given reading attempt.

The tag information (ID) is information output by the RFID tags in response to a response request (read command) from the tag reader10. The tag information can include, for example, a header, a commodity code, and a serial number. The header indicates a format of the tag information and a value range for the commodity code in the tag information. The commodity code (EPC data) is information for identifying a commodity (or other article or item). The commodity code is, for example, a stock keeping unit (SKU) code, a Japanese article number (JAN) code, or a European article number (EAN) code. The serial number is an identification number uniquely assigned to each commodity.

In the example shown inFIG. 4, the buffer memory31stores the tag information as read from the RFID tags and an RSSI value for each of the output values of the interrogation wave. In this case, the tag information and the RSSI value are stored in association with each other. The tag information and the RSSI value are read and stored each time the output value (interrogation wave strength) is changed. The processor21outputs the reading results of each of the individual RFID tags stored in the buffer memory31in a time series format or the like to the host device11in response to a request from the host device11.

FIG. 5is a flowchart for explaining an operation example of the tag reader10according to the embodiment. The processor21of the tag reader10starts reading process for an RFID tag in response to a request from the host device11connected through the communication I/F26. When starting the reading of an RFID tag, the processor21sets the output value for the radio wave (interrogation signal) to be output from the antenna25by controlling the output setting unit46to set the output value to an initial value (ACT11).

After setting the output value to the initial value, the processor21starts the RFID tag reading process (ACT12). In the reading process of the RFID tag, the processor21controls the communication control circuit24to transmit an interrogation signal at the set output value from the antenna25at a designated reading interval. RFID tags within the communication range provide a response signal in response to the interrogation signal when received. The response signals from the RFID tags are received by the antenna25and by operations of the communication control circuit24, the information from the responding RFID tags can be read by processor21.

The processor21then determines whether the output signal strength of the interrogation wave is to be changed (ACT13). The processor21changes an output value of an output signal from the antenna25when some predetermined condition is satisfied. For example, the processor21switches the output value in accordance with a change in temperature as detected by the thermistor48. Similarly, the processor21can determine to change the output value after the elapsing of a reading interval time. Likewise, the processor21can determine to change the output value in response to a change request received from the host device11. For example, the processor21can change the output value in response to a request received from the host device11to increase or decrease the output value to be used in the reading operation. In addition, the processor21may determine to change the output value in response to an instruction from the host device11to change the communication range of the tag reader10.

When the output value of the interrogation signal is changed (ACT13, YES), the processor21causes the output setting unit46to change the output value of the signal being output by the antenna25(ACT14).

When the output value is changed, the processor21stores the changed output value in the buffer memory31.

Thus, the buffer memory31can record the reading results of the RFID tags as read using the now changed output value.

The output value may be changed to a certain output value, or the output value may be increased or decreased in a predetermined variation range.

In the reading operation of the RFID tags, a response signal from the RFID tags is received in response to the output signal. That is, as a reading operation of an RFID tag, the processor causes an output signal including a read command to be transmitted from the antenna25at a set output value by using the communication control circuit24. For example, the communication control circuit24generates a modulation signal modulating a carrier wave with the read command using the modulation unit41. The transmission-side amplification unit42amplifies the modulated signal from the modulation unit41to an output value as set by the output setting unit46. The modulated signal amplified to the set output value by the transmission-side amplification unit42is supplied to the antenna25via the direction coupler43. Thus, the antenna25transmits the output signal corresponding to the read command as a radio wave having the set output value.

Any RFID tag existing in the reading area to which the output signal from the antenna25is transmitted is activated by receiving the signal from the antenna25and will recognize the read command. Any RFID tag that has recognized the read command transmits a response signal including the tag information stored in its memory by backscatter modulation, for example.

The antenna25receives a response signal indicating the tag information from each responding RFID tag. The signal received by the antenna25is supplied to the reception-side amplification unit44via the direction coupler43. The response signal amplified by the reception-side amplification unit44is input to the demodulation unit45and then demodulated. The signal as demodulated by the demodulator45is supplied to the processor21as tag information (e.g., a tag ID) that has bene read from the RFID tag.

The response signal received by the antenna25from the RFID tag input to both the reception-side amplification unit44and also the level detection unit47.

The level detection unit47measures the strength of the received signal and supplies an RSSI value indicating the measured strength to the processor21. The processor21acquires tag information (e.g., a tag ID) from the demodulation unit45and the RSSI value of the response signal.

Once the processor21acquires a reading result from the RFID tag (ACT15, YES), the processor21stores tag information and the corresponding RSSI value in the buffer memory31in association with output signal strength used for acquiring the reading result (ACT16). As a result, in the buffer memory31, the reading result of each RFID tag for which the tag information (ID) such as an EPC value (e.g., EPC1, EPC2, . . . ), the RSSI value, and the output value used for reading the RFID tag are recorded for every single tag that has been read.

During the reading process, the processor21determines whether or not the reading result stored in the buffer memory31should be transmitted to the host device11(ACT17). For example, the processor21transmits the reading result of the RFID tag accumulated in the buffer memory31to the host device11in response to a transfer request from the host device11. In some examples, the processor21may transmit the reading results of the RFID tags that have accumulated in the buffer memory31to the host device11at predetermined transmission intervals.

When it is not necessary to transmit the reading result stored in the buffer memory31(ACT17, NO), the processor21proceeds to the process of ACT19.

When the reading result of the RFID tag is output (ACT17, YES), the processor21transmits the reading result of the RFID tags stored in the buffer memory31to the host device11(ACT18). For example, the processor21transmits the tag information (ID), the RSSI value, and the output value to the host device11for every single tag reading of each RFID tag.

For example, when an RFID tag is read repeatedly over time, the processor21transmits the reading results in time series to the host device11.

By reading the RFID tags at a fixed reading interval or the like, the host device11acquires via the communication I/F14a reading result of each RFID tag arranged in time series. A processor12of the host device11is configured to detect the movement of an RFID tag or a change in the relative position of the RFID tag with respect to the tag reader based on the reading results acquired from the tag reader10.

The processor12arranges the reading results acquired from the tag reader10for each separate tag information (ID) and collates time-series reading results for each RFID tag. The processor12detects a movement, a change in position, or the like of a specific RFID tag based on a change between an output value and an RSSI value in the reading results for the RFID tag. Movement or the like of the RFID tag can be detected as a change between an output value and an RSSI value for a reading result of a specific RFID tag. For example, if there is no change in the output value but the RSSI value changes for a specific RFID tag, the processor21can detect that the RFID tag has moved.

During the reading operation of the RFID tag, the processor21determines to stop reading in response to a reading stop request (ACT19). For example, the processor21receives a request to stop reading an RFID tag from the host device11at an arbitrary timing. The processor21determines to stop reading when receiving the reading stop request from the host device11. When it is not determined to stop reading (ACT19, NO), the processor21returns to ACT13and repeatedly executes the above-described process.

When it is determined to stop reading (ACT19, NO), the processor21stops the transmission of the output signal from the antenna25and stops the reading operation of the RFID tag (ACT20). When the reading operation of the RFID tag is stopped, the processor21transmits the reading result of the RFID tag stored in the buffer memory31to the host device11(ACT21) and then ends the reading process.

In the above-described operation example, the tag reader10transmits tag information, the RSSI value, and the output value as the to the host device, but possible examples are not limited this. The tag reading system1may be any system as long as the host device11can recognize that the tag reader10has changed the output value used for tag reading. For example, the tag reader10may separately notify the host device11that the output value has been change whenever the output value is switched, and tag information and the RSSI value may be transmitted to the host device11as the reading result without specifically including the output value in the reading result for each tag reading.

As described above, the tag reading system1includes the tag reader10and the host device11and both these components process the information read from the RFID tag by the tag reader10. The tag reader10has a function of notifying the host device11of an output value of the interrogation wave output from an antenna. The tag reader10detects an RSSI value of a response signal from the RFID tags as received by the antenna in response to an interrogation wave. The tag reader10transmits tag information included in a response signal from the RFID tags and an RSSI value for the response signal to the host device11as a reading result of the RFID tags. The host device11performs the processing associated with detection of the movement of the RFID tags based the reading results from the tag reader10.

Thus, in the tag reading system1, the host device11can determine whether the change in the RSSI value in the response signal from the RFID tag has been caused by a change in the interrogation wave signal strength (output value) or by the movement of the RFID tag. As a result, the tag reading system can prevent erroneous detection of movements of RFIDs tag that might be caused by noticing a change in the RSSI value that has been caused by a change in the output signal from the tag reader10rather than RFID tag movement.

In the above-described embodiment, a program executed by a processor can be stored in advance in the memory in the device. However, a program executed by a processor may also or instead be downloaded to the device from a network or may be installed in the device from a storage medium. The storage medium may be any storage medium such as a CD-ROM that can store a program and can be read by the device. The functions obtained by the installation or download of a software program may be realized in cooperation with an OS (operating system) or the like in the apparatus.