Patent Description:
Some tag readers can vary the strength (power level) of an output signal used for reading a Radio-Frequency Identification (RFID) tag (also referred to as a wireless tag). A tag reader and a host device may constitute a tag reading system, in which the tag reader operates in accordance with a command from the host device. For example, a tag reader sets the output value for the output signal used for reading RFID tags in accordance with a setting value specified by a command from a host device.

In such a tag reading system, in order for the tag reader to perform the reading process of an RFID tag by changing the output value, the host device must supply a command to the tag reader particularly including the setting value to be used every time the output value is to be changed. For this reason, the minimum output value at which the tag reader can read a specific RFID tag has to be determined from a series of reading results obtained with the host device gradually changing the output value by commands over time. This operation requires some time for the tag reader to identify the minimum output value at which the specific RFID tag can be read.

<CIT> relates to an apparatus for communicating with an RFID tag comprising a radio communicating device configured to conduct radio communication with a plurality of individual RFID tags constituting a single tag group and a single representative RFID tag associated so as to represent said tag group; a first information obtainment portion configured to conduct first communication for search of said representative RFID tag corresponding to said individual RFID tag to be searched and to obtain information from said representative RFID tag; a switching determination portion configured to determine if said first communication in information obtainment satisfies a predetermined switching condition; and a second information obtainment portion configured to conduct second communication for search of said individual RFID tag to be searched in a communication mode different from that of said first communication if the determination is satisfied and to obtain information from said individual RFID tag.

According to the present disclosure, it is provided a tag reader, comprising: a communication controller configured to control an output level of an output signal to be output from an antenna for reading a wireless tag; a communication interface configured to communicate with a host device, and a processor configured to specify a minimum output level of the output signal at which the wireless tag can be read and transmit the minimum output level to the host device through the communication interface.

Optionally, in the tag reader according to the present disclosure, the communication controller is further configured to incrementally change the output level of the output signal in repeated reading attempts of the wireless tag.

Optionally, in the tag reader according to the first aspect of the invention, the output level is increased from an initial value for the repeated reading attempts.

Optionally, in the tag reader according to the present disclosure, the communication controller decreases the output value with a predetermined decrease width stored in a memory of the tag reader.

Optionally, in the tag reader according to the present disclosure, the output level is decreased from an initial value for the repeated reading attempts.

Optionally, in the tag reader according to the present disclosure, the increment of the incremental change is a fixed value.

Optionally, in the tag reader according to the present disclosure, the processor transmits the minimum output level to the host device together with tag information read from the wireless tag.

According to the present disclosure, it is provided a tag reader, comprising an antenna; a communication control circuit connected to the antenna and configured to control an output level of an output signal output from an antenna for reading a wireless tag; and a processor connected to the communication control circuit and configured to: execute a plurality of reading attempts of the wireless tag using different output levels; determine a minimum output level for the output signal at which the wireless tag can be read in the plurality of reading attempts; and transmit the minimum output value to a host device along with tag information read from the wireless tag.

Optionally, in the tag reader according to the present disclosure, the output level is decreased in the plurality of reading attempts based on a predetermined decrement.

Optionally, in the tag reader according to the present disclosure, the processor is further configured to: determine whether an output level for a successful reading attempt is smaller than a previously stored output level of a successful reading attempt; and update the stored output value with the smaller output value if the output value is smaller than the stored output value.

Optionally, in the tag reader according to the present disclosure, output level is increased in the plurality of reading attempts based on the predetermined increment.

Optionally, in the tag reader according to the present disclosure, the processor is further configured to determine whether the output level exceeds a specified value.

Optionally, in the tag reader according to the present disclosure, the wireless tag is a radio frequency identification (RFID) tag.

According to the present disclosure, it is provided a tag reading system, comprising: a host device; and a tag reader connected to the host device, the tag reader comprising: an antenna; a communication control circuit connected to the antenna and configured to control an output level of an output signal output from an antenna for reading a wireless tag; and a processor connected to the communication control circuit and configured to: execute a plurality of reading attempts of the wireless tag using different output levels; determine a minimum output level for the output signal at which the wireless tag can be read in the plurality of reading attempts; and transmit the minimum output value to the host device along with tag information read from the wireless tag.

Optionally, in the tag reading system according to the present disclosure, the output level is decreased in the plurality of reading attempts based on a predetermined decrement.

Optionally, in the tag reading system according to the present disclosure, the processor is further configured to: determine whether an output level for a successful reading attempt is smaller than a previously stored output level of a successful reading attempt; and update the stored output value with the smaller output value if the output value is smaller than the stored output value.

Optionally, in the tag reading system according to the present disclosure, output level is increased in the plurality of reading attempts based on the predetermined increment.

Optionally, in the tag reading system according to the present disclosure, the wireless tag is a radio frequency identification (RFID) tag.

Optionally, in the tag reading system according to the present disclosure, the host device includes a display screen and is configured to indicate an estimated position of the wireless tag on the display screen, the estimated position being calculated based on the minimum output level at which the wireless tag has been successfully read.

Optionally, in the tag reading system according to the present disclosure, the tag reader further comprises: a grip part configured to be held by an operator; and a host holding part configured to hold the host device.

According to one or more embodiments, a tag reader includes a communication controller, a communication interface, and a processor. The communication controller controls an output level of an output signal to be output from an antenna for reading an RFID tag. The communication interface communicates with a host device. The processor specifies a minimum output level of the output signal at which the RFID tag can be read and transmits the minimum output level to the host device through the communication interface.

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

<FIG> is a block diagram illustrating an example configuration of a tag reading system <NUM> according to an embodiment. The tag reading system <NUM> according to the present embodiment includes a tag reader <NUM> and a host device <NUM>. The tag reader <NUM> reads an RFID tag (or a wireless tag). The host device <NUM> estimates a position of the RFID tag based on a continuous repetitive reading of the RFID tag by the tag reader <NUM> and identifies an article, an item, or the like to which the read RFID tag is attached.

For example, the tag reading system <NUM> is operated as a search system for searching for an article to which an RFID tag has been attached. Such a search system may cover a predetermined area such as a warehouse or a retail store. In the tag reading system <NUM> operated as such a search system, the tag reader <NUM> continuously attempts to read the RFID tag while the tag reader <NUM> moves in the predetermined area. The host device <NUM> detects a position or the like of the RFID tag based on the reading result of the RFID tag as acquired from the tag reader <NUM>. Along with tag information read from the RFID tag, the tag reader <NUM> of the present embodiment supplies, to the host device <NUM>, a minimum output value (or a minimum signal strength) for an output signal (interrogation wave or the like) at which the RFID tag has been read.

In the present embodiment, the tag reader <NUM> repeatedly reads the RFID tag attached to an article such as a commodity while the tag reader <NUM> moves around. The host device <NUM> executes predetermined processing (for example, search processing) based on the reading results from the RFID tag. In another embodiment, in a tag reading system <NUM>, the tag reader <NUM> can be installed at a fixed position may be utilized to repeatedly read an RFID tag attached to a moving article.

The tag reader <NUM> reads information recorded in an RFID tag. The information from the RFID tag is received in a response signal from an RFID tag within a communication range (that is a reading range) of the tag reader <NUM>. For example, the tag reader may be a hand-held type device that is held by an operator or may be mounted on a moving body.

The tag reader <NUM> transmits an interrogation signal (an output signal) for requesting a response from the RFID tag at a preset intensity (or a preset output value). The tag reader <NUM> receives a response signal from RFID tags receiving the interrogation signal. The tag reader <NUM> receives a response signal indicating tag information from the RFID tag that is present in a communication range and has been activated by the transmitted output signal. When a plurality of RFID tags are in the communication range, the tag reader <NUM> receives response signals indicating tag information from each of the respective RFID tags.

The tag reader <NUM> notifies the host device <NUM> of a minimum output value of an output signal at which each RFID tag can be read (that is, the lowest output value for the interrogation signal for which a response signal from the RFID tag was received). The tag reader <NUM> transmits a reading result including the tag information of the RFID tag and the minimum output value to the host device <NUM>. The tag reader <NUM> may measure a Received Signal Strength Indicator (RSSI) value indicating the strength of a response signal received from the RFID tag. In this case, the tag reader <NUM> may include the RSSI value for each reading of the RFID tag to the host device <NUM> in the reading result of the RFID tag.

The RFID tag is typically attached to an article such as a commodity or a component, and tag information including information that can be used for identifying the article is recorded in an internal memory of the RFID tag. The RFID tag is activated by the radio wave transmitted from the tag reader <NUM>. Upon receiving the interrogation signal, RFID tag outputs a response signal including its recorded tag information in response to a read command (interrogation signal) received from the tag reader <NUM>. The RFID tag can be powered by the radio waves output from the tag reader <NUM>.

The host device <NUM> is an information processing terminal communicably connected to the tag reader <NUM>. For example, the host device <NUM> is 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 device <NUM> may instead be an information processing device installed at a specific position as long as it has a communication interface capable of communicating with the tag reader.

In the present embodiment, the host device <NUM> includes a processor <NUM>, a memory <NUM>, a communication interface (I/F) <NUM>, a display device <NUM>, an input device <NUM>, and the like. The processor <NUM> performs control of each unit, data processing, and the like. The processor <NUM> is, for example, a CPU. The processor <NUM> executes a program stored in the memory <NUM> to perform various operations. For example, the processor <NUM> detects the position of the RFID tag or a change in the relative position between the tag reader <NUM> and the RFID tag based on the reading result of the RFID tag acquired from the tag reader <NUM>. These processes are realized by the processor <NUM> executing a program (or programs), such as an application program, installed in the memory <NUM>.

The communication interface (I/F) <NUM> is an interface for communicating with an external device. In the present embodiment, the communication I/F <NUM> is an interface for communicating with the tag reader <NUM>. The communication I/F <NUM> may correspond to the communication function of the tag reader <NUM>. The communication I/F <NUM> may be an interface for wired communication or an interface for wireless communication. For example, the communication I/F <NUM> is realized by a LAN interface, a universal serial bus (USE) interface, a Bluetooth (registered trademark) interface, a Wi-Fi interface, or the like.

The display device <NUM> is a device that displays information. For example, the display device <NUM> displays a detection result of the RFID tag (for example, movement of the RFID tag). The input device <NUM> is a device for an operator to input an operation instruction or the like. The display device <NUM> and the input device <NUM> are configured by, for example, a display device with a touch panel.

In the present embodiment, the tag reader <NUM> includes a processor <NUM>, a ROM <NUM>, and a RAM <NUM>, a communication controller such as a communication control circuit <NUM>, an antenna <NUM>, a communication interface (I/F) <NUM>, a display device <NUM>, a power supply <NUM>, and a data memory <NUM>.

The processor <NUM> controls each unit. The processor <NUM> includes, for example, an arithmetic circuit such as a CPU. The processor <NUM> implements control of each unit and various types of data processing by executing a program (or programs). The processor <NUM> may include an internal memory. The processor <NUM> implements various processes by executing a program stored in the ROM <NUM> or the internal memory. For example, the processor <NUM> interprets a command from the host device <NUM> received by the communication I/F <NUM> and executes a process corresponding to the command.

The ROM <NUM> is a non-volatile and non-rewritable memory. The ROM <NUM> stores a program (or programs) to be executed by the processor <NUM> and the like. The RAM <NUM> is a volatile memory that temporarily stores data. For example, the RAM <NUM> functions as a working memory or a buffer memory. The RAM <NUM> has a buffer memory for storing the reading result of the RFID tag.

The communication controller or the communication control circuit <NUM> and the antenna <NUM> constitute an RFID interface for reading an RFID tag. The communication control circuit <NUM> includes a control circuit for communicating with the RFID tag via the antenna <NUM>. The communication control circuit <NUM> causes the antenna <NUM> to transmit a transmission signal (or a radio wave) supplied from the processor <NUM> at a preset output value. The antenna <NUM> outputs the transmission signal supplied from the communication control circuit <NUM> as a radio wave that can be received by the RFID tag.

The communication control circuit <NUM> not only outputs a transmission signal to the antenna <NUM> but also supplies a signal received by the antenna <NUM> to the processor <NUM> as reception data. For example, the antenna <NUM> receives a response signal from the RFID tag, and the response signal (reception signal) received by the antenna <NUM> is processed and supplied to the processor <NUM>. For example, the communication control circuit <NUM> supplies to the processor <NUM> tag information included in a reception signal from the RFID tag and an RSSI value indicating the intensity of the reception signal.

The communication I/F <NUM> is an interface for communicating with an external device. In the present embodiment, the communication I/F <NUM> is a communication interface for communicating with the host device <NUM>. The communication I/F <NUM> may be an interface for wired communication or an interface for wireless communication. For example, the communication I/F <NUM> is realized by a LAN interface, a universal serial bus (USE) interface, a Bluetooth (registered trademark) interface, a Wi-Fi interface, or the like.

The display device <NUM> is a display device that displays an operation state of the RFID tag. The display device <NUM> comprises, for example, an LED or the like. The power supply <NUM> supplies power for operating the tag reader <NUM>. The power supply <NUM> supplies power for operation to each unit of the tag reader <NUM>. For example, if the tag reader is a handy type, the power supply <NUM> may comprise a rechargeable battery. If the tag reader is a stationary type connectable to a commercial power supply, the power supply <NUM> may comprise a power supply circuit connected to the commercial power supply.

The data memory <NUM> is a rewritable nonvolatile memory. The data memory <NUM> stores setting values and other information used for various processes. The setting values stored in the data memory <NUM> are, for example, information that can be updated according to an operation mode or the like. The data memory <NUM> may store an application program and the like. The data memory <NUM> may store information such as a processing result to be held even after the power is turned off.

The tag reader <NUM> may include a timer that measures time. For example, the timer measures an elapsed time from when a read operation is stopped (for example, when output of the output signal is halted) to when the next read operation is started (for example, when another output signal is output). The processor <NUM> may use the timer and detect that a pause time or a downtime from when the read operation is stopped to when the next read operation is started has reached a preset read interval.

In the configuration example illustrated in <FIG>, the communication control circuit <NUM> includes a modulation unit <NUM>, a transmission-side amplification unit <NUM>, a direction coupler <NUM>, a reception-side amplification unit <NUM>, a demodulation unit <NUM>, an output setting unit <NUM>, and the like. In general, some or all of the various units of the communication control circuit <NUM> may be implemented as circuits, circuitry, or otherwise.

In the present example, the modulation unit <NUM> is a modulation circuit that modulates a waveform signal with input data. The modulator <NUM> modulates a carrier wave with the transmission data supplied from the processor <NUM>. The transmission-side amplification unit <NUM> includes an amplification circuit that amplifies the input signal. The transmission-side amplification unit <NUM> amplifies the output signal from the modulator <NUM>. The direction coupler <NUM> includes a circuit that supplies the output signal from the transmission-side amplification unit <NUM> to the antenna <NUM>. Thus, the communication control circuit <NUM> outputs a carrier wave that has been modulated with the transmission data from the antenna <NUM>.

The RFID tag receives the radio wave transmitted from the antenna <NUM>. The RFID tag recognizes, for example, a read command included in the signal received from the antenna <NUM>. When the RFID tag recognizes the read command, the RFID tag outputs data, including tag information, stored in the memory of the RFID tag via a return radio wave generated, for example, by backscatter modulation.

The antenna <NUM> receives the radio wave (response signal) output from the RFID tag. The direction coupler <NUM> includes a circuit that acquires the signal received by the antenna <NUM> and supplies the acquired response signal to the reception-side amplification unit <NUM>. In this example, the reception-side amplification unit <NUM> includes an amplification circuit that amplifies an input signal. The reception-side amplification unit <NUM> amplifies the response signal received by the antenna <NUM>. The demodulation unit <NUM> includes a demodulation circuit that demodulates the data superimposed on the waveform signal (or the carrier wave). The demodulation unit <NUM> demodulates data, such as tag information, included in the response signal amplified by the reception-side amplification unit <NUM>.

The antenna <NUM> may transmit and receive the radio wave to and from the RFID tag. The antenna <NUM> may transmit a signal to be supplied to the RFID tag and receive a radio wave output from the RFID tag. In the present embodiment, the antenna <NUM> is arranged to transmit electromagnetic waves toward a reading area. The tag reader <NUM> is configured to communicate with a plurality of RFID tags attached to a plurality of commodities arranged in the reading area via the antenna <NUM>. The antenna <NUM> is, for example, a planar antenna. The antenna <NUM> is not limited to any specific configuration.

The output setting unit <NUM> includes a setting circuit that sets the strength (power level) of a signal to be output from the tag reader <NUM>. The output setting unit <NUM> performs control so that the strength of the signal output from the transmission-side amplification unit <NUM> matches a preset output value. The transmission-side amplification unit <NUM> amplifies the signal supplied from the modulation unit <NUM> so as to have an output value set by the output setting unit <NUM> and outputs the amplified signal to the direction coupler <NUM>. Thus, the antenna <NUM> transmits an output signal having an output value as set by the output setting unit <NUM> and supplied from the amplifying unit <NUM> via the coupler <NUM>.

<FIG> depicts an example configuration of a tag reading system <NUM> operating as a search system 101according to an embodiment. That is search system <NUM> is one example of an application of a tag reading system <NUM>. The search system <NUM> is a system for searching for a specific RFID tag T within in a search area. For example, the specific RFID tag T may be attached to a specific item or commodity. When searching for a specific item or commodity in a warehouse or a store, the search system <NUM> estimates a position of an RFID tag based on a reading results of the RFID tag T obtained by the tag reader <NUM>. The search system <NUM> displays the position of the specific item or commodity as estimated from the reading results of the RFID tag T. Thus, the search system <NUM> can support a search for a particular commodity, as specified by an operator, when the commodity has a known or identifiable RFID tag attached thereto.

The search system <NUM> shown in <FIG> includes a hand-held type tag reader <NUM> and a host device <NUM> communicably connected to the tag reader <NUM>. In the example configuration shown in <FIG>, the tag reader <NUM> is a modification of the tag reader <NUM> depicted in <FIG>, and the host device <NUM> is a modification of the host device <NUM> depicted in <FIG>.

The tag reader <NUM> includes, in addition to the configuration of the tag reader <NUM> shown in <FIG>, a gripping part <NUM>, for gripping by an operator, and a holding part <NUM>, for holding the host device <NUM>. An operator grips the gripping part <NUM> and operates the tag reader <NUM> with the host device <NUM> being held by the holding part <NUM>. For example, until a desired RFID tag T is detected, the operator moves the tag reader <NUM> around to search a search area.

The host device <NUM> has the same or substantially the same configuration as that of the host device <NUM> shown in <FIG> but includes a display device <NUM> with a touch panel as the display device <NUM> and the input device <NUM>. For example, the host device <NUM> may be implemented as a portable information terminal such as a smartphone or a tablet PC. The host device <NUM> notifies the operator of the position of the desired RFID tag T as estimated based on the reading results from the tag reader <NUM>.

The search system <NUM> searches for the RFID tag T while the operator grips the tag reader <NUM> at the gripping part <NUM> and moves the tag reader <NUM> with the host device <NUM> communicably connected to the tag reader <NUM> while held by the holding part <NUM>. In the search system <NUM>, the tag reader <NUM> attempts to read RFID tags at a predetermined reading interval. Tag reader <NUM> can read RFID tags within the communication range R, the position of which can be changed by movement of the tag reader <NUM> by the operator. The tag reader <NUM> supplies the reading results for the RFID tags in the communication range R. The tag reader <NUM> supplies, to the host device <NUM>, this acquired tag information (or tag ID), such as an Electronic Product Code (EPC), an RSSI value of the received signal providing the tag information, and the output value being used by the tag reader <NUM> in the reading attempt corresponding to the received signal as a reading result of each RFID tag in the communication range R.

The host device <NUM> detects the reading result of a desired RFID tag T from the reading results supplied from the tag reader <NUM> for all the RFID tags. The host device <NUM> estimates the position of the RFID tag T based on the reading results for the RFID tag T. For example, the host device <NUM> detects a change in the position of the RFID tag T or the relative position between the tag reader <NUM> and the RFID tag based on the minimum output value or the like included in the reading results of the RFID tag T. The host device <NUM> displays information indicating the position or the like of the RFID tag T as estimated based on the reading results on display device <NUM>.

<FIG> depicts an example display screen for a search result of an RFID tag as displayed by the host device <NUM> according to the present embodiment. In the search system <NUM>, the host device <NUM> estimates a position of a specific RFID tag based on the reading results from the tag reader <NUM>. The host device <NUM> detects the position of the specific RFID tag as a relative position with respect to the tag reader <NUM>. The host device <NUM> displays information indicating the position of the specific RFID tag on the display device <NUM>.

In the example display screen shown in <FIG>, the display device <NUM> displays a read range symbol <NUM> corresponding to a reading range of the tag reader <NUM>. The read range symbol <NUM> is superimposed on a concentric circle symbol <NUM>, which is centered on the position of the tag reader <NUM>. For example, the display device <NUM> displays the read range symbol <NUM> on the concentric circle symbol <NUM> such that its upper side coincides with the front side (that is the read direction) of the tag reader <NUM>. Thus, the facing direction of the tag reader <NUM> and the display orientation direction can be intuitively recognized.

The display device <NUM> displays a mark <NUM> indicating a position of a RFID tag that has been read. The mark <NUM> is superimposed on the read range symbol <NUM> and the concentric circle symbol <NUM>. For example, the host device <NUM> estimates the relative position of the RFID tag based on the RSSI value and the output value included in the reading results for the RFID tag received from the tag reader <NUM>. The display device <NUM> shows an estimated distance from the tag reader <NUM> to the RFID tag by displaying the mark <NUM> on the concentric circle symbol <NUM>. This enables the display device <NUM> to notify the operator of the distance from the tag reader <NUM> at which the RFID tag is present. The position of the RFID tag relative to the facing direction (present orientation) of tag reader <NUM> can also be indicated by placement of the mark <NUM> on the concentric circle symbol <NUM>.

In the example display shown in <FIG>, the display device <NUM> also displays, in display region <NUM>, an item number being searched for and a serial number of the RFID tag, corresponding to the mark <NUM>, in the display region <NUM>. Thus, the operator can easily confirm the RFID tag as the search target. The display device <NUM> may also display a search start button <NUM> and an end button <NUM>. The search start button <NUM> and the end button <NUM> are buttons that the operator can operate on a touch panel, which functions as an input device <NUM> in this context. The search start button <NUM> is a button for the operator to designate start of an RFID tag search. The end button <NUM> is a button for the operator to designate end of RFID tag search. The operator can search for an RFID tag by operating the tag reader <NUM> while viewing the screen as shown in <FIG>.

<FIG> depicts an example reading result of an RFID tag as read by the tag reader <NUM> and stored in the RAM <NUM> thereof (see <FIG>) according to the present embodiment. The processor <NUM> stores the tag information (ID) of each read RFID tag along with the minimum output value at which the RFID tag could be read by the tag reader <NUM>. This information is stored in the RAM <NUM> in association with each other as the reading result of each RFID tag. In the RAM <NUM>, after the tag information and the minimum output value are stored, the stored minimum output value is updated whenever the output value is lowered and the same RFID tag is successfully read again.

The minimum output value is lowest output value (power level) for the interrogation signal output from the antenna <NUM> at which the RFID tag can be successfully read by the tag reader <NUM>. This value generally correlates to distance of the RFID tag from the tag reader <NUM>. The output value is set by the output setting unit <NUM> of the communication control circuit <NUM> (<FIG>) in accordance with a command from the processor <NUM>. Therefore, the processor <NUM> can repeatedly read a specific RFID tag while changing the output value of the output signal. For example, the processor <NUM> can identify the minimum output value by repeatedly executing the reading operation of a specific RFID tag while gradually decreasing the output value until the RFID tag can no longer be successfully read. A similar process can be performed by gradually increasing the output value until the RFID tag can be successfully read.

The tag information is output by the RFID tag in response to a response request (or a read command) from the tag reader <NUM>. The tag information includes, for example, a header, a commodity code, and a serial number. The header is information indicating a format of the tag information and a range of the commodity code in the tag information.

The commodity code, such as an Electronic Commodity Code (EPC) data, specifies a commodity, an article, an item, or the like (hereinafter collectively referred to as a commodity). The commodity code is, for example, a Stock Keeping Unit (SKU) code, a Japanese Article Number (JAN) code, or an European Article Number (EAN) code.

The serial number individually identifies each commodity. For example, two commodities that are recognized as the same commodity in terms of classification by commodity code can be given different serial numbers. That is, the commodities to which the RFID tags are attached can be managed as individual commodities by the respective serial numbers in addition to or instead of the commodity classification (commodity code basis).

<FIG> is a flowchart of an example operation of the tag reader <NUM> according to the present embodiment. The processor <NUM> of the tag reader <NUM> starts continuous reading processing (such as the search processing) of an RFID tag in response to a command from the host device <NUM> connected through the communication I/F <NUM>. In this example operation, the tag reader <NUM> acquires, from the host device <NUM>, information indicating an RFID tag to be searched for (that is, a search target) and an initially specified output setting value for the output value of an output signal for a reading operation.

Upon start of the continuous reading processing, the processor <NUM> sets an output value "a" for an output signal for the reading operation to a value "PWR" as specified by the host device <NUM> for the initial output value setting(ACT11). For example, the processor <NUM> stores a value that indicates the output value a in a register. The processor <NUM> designates the output value a stored in the register to the output setting unit <NUM>. Accordingly, the communication control circuit <NUM> performs control such that the output signal from the antenna <NUM> becomes the specified value PWR.

The processor <NUM> sets a filter based on the information that indicates the particular RFID tag(s) to be searched for (hereinafter referred to as a target RFID tag) as specified by the host device <NUM> (ACT12). The processor <NUM> executes a search for the target RFID tag by setting the filter parameters to exclude RFID tags that are not being searched for. For example, only a particular commodity code and/or serial number may be permitted to pass the filtering process.

Once the filter for specifying the target RFID tag has been set, the processor <NUM> starts reading the RFID tags using the set output value a (ACT13). The processor <NUM> then determines whether the target RFID tag has been read by the output signal of the output value a from the antenna <NUM> (ACT14). The processor <NUM> determines that the target RFID tag has been read if a response signal from the target RFID tag has been received by the antenna <NUM> in response to the output signal of the output value a.

When a response signal including the target tag information has been received, that is, when the target RFID tag has successfully been read (ACT14, YES), the processor <NUM> further determines whether the target RFID tag reading is a duplicate reading, that is, whether the same RFID tag has already been read before (ACT15). For example, when the same tag information is already stored in the RAM <NUM>, the processor <NUM> determines that the just read tag information represent a duplicate reading. Otherwise, the processor <NUM> determines that the just read tag information is not a duplicate reading.

If the current reading is not a duplicate reading (ACT15, NO), the processor <NUM> stores the current output value a, which is the output value of the output signal used for the current reading of the target RFID tag, in RAM <NUM> in association with the tag information included in the response signal received from the target RFID tag (ACT16). Here, the processor <NUM> may store the output value a being held in the register in association with the tag information. After storing the tag information and the output value, the processor <NUM> proceeds to ACT20.

If the current reading is a duplicate reading (ACT15, YES), the processor <NUM> determines whether the current output value a is smaller than the output value corresponding to the previously stored tag information for the same RFID tag (ACT17). The current output value a is the output value of the output signal used to obtain the current reading of the RFID tag and is held in the register. The stored output value is the output value stored in the RAM <NUM> prior to the current reading, in association with the tag information of the same RFID tag. For example, the processor <NUM> finds the stored output value in the RAM <NUM> and determines whether the current output value a is less than the stored output value.

If the current output value a is greater than or equal to the stored output value (ACT17, NO), the processor <NUM> proceeds to ACT20 without updating the stored output value in RAM <NUM>. The stored output value is thus the minimum output value at which the RFID tag has been be read, but can be updated as the output value used in the reading operation is changed and new tag reading results are acquired. However, if the current output value a is greater than or equal to the stored output value, it is not necessary to update the stored output value in the RAM.

If the current output value a is less than the stored output value (ACT17, YES), the processor <NUM> updates the stored output value with the current output value a (ACT18). For example, the processor <NUM> rewrites the stored output value held in the register to the current output value a.

After the stored output value in the RAM <NUM> is updated, the processor <NUM> decreases the output value a to be used for the next reading operation (ACT19). For example, the processor <NUM> reduces the output value a by an increment b set in advance. In this case, for example, the processor <NUM> sets the output value a held by the register to a-b (a=a-b). The increment b may be preset as appropriate. For example, the increment b is stored in the data memory <NUM>. Thus, the processor <NUM> can set the increment b stored in the data memory <NUM>. After decreasing the output value, the processor <NUM> proceeds to ACT20.

When the target RFID tag cannot be read in ACT14 (ACT14, NO), the processor <NUM> increases the output value a of the output signal used for the reading operation (ACT26). For example, the processor <NUM> increases the output value a by a preset increment c. That is, the processor <NUM> increases the output value a by an increment c by setting the output value a held in the register to a+c (a=a+c). The increment c may be set as appropriate. For example, the increment c is stored in the data memory <NUM>. Thus, the processor <NUM> can set the increment c stored in the data memory <NUM>.

The increment b and the increment c may be the same value or different values. Further, the increment b and the increment c need not be constant and may be varied according to various conditions. In a case where increment b and the increment c are variable according to different conditions, the processor <NUM> can change the output value a by an increment b or an increment c set according to the different conditions.

After increasing the output value a, the processor <NUM> determines whether the increased output value a exceeds a specified value MAX, which is a maximum output setting value (ACT27). If the increased output value a does not exceed the specified value MAX (ACT27, NO), the processor <NUM> keeps output value a as it is, and proceeds to ACT20. If the increased output value a exceeds the specified value MAX (ACT27, YES), the processor <NUM> updates the output value a to the specified value MAX (ACT28) and proceeds to ACT20. This way, the processor <NUM> can vary the output value a within a range not exceeding the specified value MAX provided by the host device <NUM> or the like.

In ACT20, the processor <NUM> determines whether to transmit the reading result of the RFID tag stored in RAM <NUM> to the host device <NUM> (ACT20). For example, the processor <NUM> determines to output the reading result stored in the RAM <NUM> in response to a reading result transmission request from the host device <NUM>.

If there is a request for the reading result of the RFID tag from the host device <NUM> (ACT20, YES), the processor <NUM> transmits the reading result including the tag information stored in RAM <NUM> and the stored output value (which corresponds to presently determined minimum output value) to the host device <NUM> (ACT21). This way, the processor <NUM> can notify the host device <NUM> of the minimum output value together with the read tag information.

During the continuous reading processing, the processor <NUM> can receive an output setting command, that is a command to request the change or setting of the output value, from the host device <NUM> (ACT22). When the output value setting command is received (ACT22, YES), the processor <NUM> changes the output value a held in the register to an output setting value specified (requested) by the command (ACT23). For example, if the output setting command designates the specified value PWRa, the processor <NUM> rewrites the output value a held in the register to PWRa. Accordingly, each time the processor <NUM> receives an output setting command from the host device <NUM>, the processor <NUM> changes the output value a to an output setting value specified by the command.

The processor <NUM> determines whether to end the continuous reading processing (the search processing in the present embodiment) (ACT24). For example, the processor <NUM> determines that the continuous reading processing is to be ended when a command requesting the end of the continuous reading processing is received from the host device <NUM>.

In a case where the continuous reading processing is not to be ended, that is, where the reading operation is to be executed again (ACT24, NO), the processor <NUM> returns to ACT13. When the continuous reading processing is to be ended by the request from the host device <NUM> or otherwise (ACT24, YES), the processor <NUM> stops the continuous reading operation and transmits the data read from the RFID tag (ACT25).

In the continuous reading processing according to the present embodiment, the tag reader <NUM> identifies the minimum output value for the output signal at which the target RFID tag can be read, and transmits this identified minimum output value to the host device <NUM>. The tag reader <NUM> repeatedly executes a reading operation while gradually changing the output value of the output signal. When the tag reader <NUM> reads the target RFID tag, the tag reader <NUM> stores the output value of the output signal with which the current reading of the RFID tag has been obtained in memory, such as the RAM <NUM>, in association with the tag information of the target RFID tag as read. In a case where there is a duplicate reading of the target RFID tag already stored in the memory, if the current output value is less than the previously-stored output value, the tag reader <NUM> updates the stored output value to the current output value. The tag reader <NUM> updates the host device <NUM> of the minimum output value at which the specific RFID tag can read.

Thus, the tag reader <NUM> according to the present embodiment can specify the minimum output value from the result of reading the RFID tag by changing the output value without a command or a request to change the output value from the host device <NUM>. In this case, the tag reader <NUM> can perform the process of specifying the minimum output value from the result of reading the RFID tag without waiting for a command from the host device <NUM> and can specify the minimum output value at high speed. In addition, the tag reader <NUM> can provide the host device <NUM> with information indicating the minimum output value at which the RFID tag can be read. Therefore, it is possible to reduce the processing load on the host device <NUM>.

<FIG> is a flowchart of an example operation of the host device <NUM> according to the present embodiment. In a standby state, the processor <NUM> of the host device <NUM> waits for an instruction to start continuous reading processing (ACT31). For example, the processor <NUM> of the host device <NUM> starts the continuous reading processing in response to an instruction or a request from an operator. In one instance, when an operator presses or selects the search start button <NUM> shown on the display device <NUM> of the host device <NUM> (<FIG>), the processor <NUM> starts the continuous reading processing to search for a target RFID tag.

When the continuous reading processing is started, the processor <NUM> determines a specified value PWR as an output setting value for an output value a to be used for the reading operation by the tag reader <NUM> (ACT32). In one instance, the specified value PWR can be based on a designated value from the operator. In another instance, the specified value PWR may be a default preset value.

The processor <NUM> sets the search information for the target RFID tag (search target) (ACT33). For example, when the operator wants to search for a particular commodity or commodity type, then a commodity code (such as an EPC) recorded in an RFID tag attached to the designated commodity or commodity type can be set by the processor <NUM> as a search criterion for the target RFID tag to be read.

Once the specified value PWR and the target RFID tag search criteria are set, the processor <NUM> requests the tag reader <NUM> to perform a continuous reading operation to search for the target RFID tag using the specified value PWR as an initial setting (ACT34). For example, the processor <NUM> transmits, to the tag reader <NUM>, a continuous read command in which the specified value PWR for the output value a and information indicating the target RFID tag are designated.

After requesting the tag reader <NUM> to perform the continuous reading operation, if a reading result of the target RFID tag is needed (ACT35, YES), the processor <NUM> requests the tag reader <NUM> to transmit the reading result of the target RFID tag (ACT36). For example, the processor <NUM> requests the reading result by sending a command for requesting the reading result to the tag reader <NUM>.

The processor <NUM> acquires the reading result of the target RFID tag transmitted from the tag reader <NUM> in response to the transmission request (ACT37). The reading result of the target RFID tag acquired from the tag reader <NUM> includes the presently determined minimum output value at which the target RFID tag has been read, together with the tag information of the target RFID tag. When the reading result is acquired from the tag reader <NUM>, the processor <NUM> specifies information to be displayed as the reading result (search result) of the target RFID tag based on the acquired reading result and displays the information on the display device <NUM> (<FIG>) or the display device <NUM> (<FIG>). For example, when the information as shown in <FIG> is to be displayed on the display device <NUM>, the processor <NUM> estimates the position of the read RFID tag with reference to the position of the tag reader <NUM> and displays the position on the display device <NUM>.

The processor <NUM> can also request the tag reader <NUM> to change/update the output setting value during the continuous reading operation (ACT39). For example, the processor <NUM> determines whether to designate a new output setting value for the tag reader <NUM> in accordance with a designated value input by the operator of the host device <NUM>, for example. In another instance, when the processor <NUM> acquires the reading result of the RFID tag, the processor <NUM> may request to adjust the output value a based on the acquired reading result values.

If the output setting value is designated (changed) by the host device <NUM> (ACT39, YES), the processor <NUM> sets the output setting value accordingly (ACT40). For example, the processor <NUM> can determine to change the present output value based on the minimum output value included in the reading result acquired from the tag reader <NUM>. In one instance, the processor <NUM> may change the output setting value to the minimum output value or may set the output setting to value to a value calculated by reference to the previously received minimum output value.

Once the new output setting value for the tag reader <NUM> has been set or otherwise determined, the processor <NUM> generates an output value set command for designating the new output setting value as the output value and transmits the generated command to the tag reader <NUM> (ACT41). With this command, the new output setting value is set as the output value a in the tag reader <NUM>.

Eventually, the processor <NUM> receives an instruction to end the continuous reading operation or otherwise determines to end the continuous reading operation (ACT42). For example, the processor <NUM> determines that the continuous reading operation is to be ended when the end button <NUM> shown on the display device <NUM> (<FIG>) is pressed by the operator. When the continuous reading operation is to be ended (ACT42, YES), the processor <NUM> instructs the tag reader <NUM> to end the continuous reading operation (ACT43). For example, the processor <NUM> transmits, to the tag reader <NUM>, an end command for instructing the end of the continuous reading operation. In response to the end command, the tag reader <NUM> ends the continuous reading of the RFID tag.

In the tag reading system <NUM> according to the present embodiment, the tag reader <NUM> identifies a minimum output value for an output signal capable of reading the target RFID tag and notifies the host device <NUM> of the minimum output value. The host device <NUM> acquires the minimum output value from the tag reader <NUM> and requests the tag reader <NUM> to output any setting corresponding to the minimum output value.

In the tag reading system <NUM> according to the present embodiment, the tag reader <NUM> changes the output value a of the output signal for reading the RFID tags. The change is gradual and can be started from an output setting value designated by the host device <NUM>. The tag reader <NUM> identifies the minimum output value of the output signal capable of reading the RFID tag from the results of reading the RFID tag while changing the output value a gradually. The tag reader <NUM> then transmits the determined minimum output value to the host device <NUM> together with the tag information read from the RFID tag.

In the tag reading system <NUM> according to the present embodiment, even if the tag reader <NUM> does not receive an instruction to change the output value a from the host device <NUM>, the tag reader <NUM> can identify the minimum output value at which the RFID tag can actually been read by changing the output value a. As a result, the tag reading system <NUM> can specify at high speed the minimum output value for reading the target RFID tag during a continuous reading process (search process). The tag reading system <NUM> can also increase the speed of the process by the host device <NUM>. Furthermore, since the tag reader <NUM> can automatically identify the minimum output value at which the target RFID tag can be read, the processing program installed in the host device <NUM> can be simplified.

In the present embodiment, the program (or programs) to be executed by the processor <NUM> of the tag reader <NUM> or the processor <NUM> of the host device <NUM> can be stored in advance in a memory, such as the ROM <NUM> of the tag reader <NUM> or the memory <NUM> of the host device <NUM>. In another embodiment, the program (or programs) to be executed by the processor <NUM> or processor <NUM> may be downloaded to the tag reader <NUM> or the host device <NUM> from a network or may be installed in the tag reader <NUM> or the hot device <NUM> from a storage medium. The storage medium may be any storage medium that can store the program and be read by the tag reader <NUM> or the host device <NUM>. The functions obtained by such program installation or download in advance may be realized in cooperation with an operating system (OS) or the like in the tag reader <NUM> or the host device <NUM>.

Claim 1:
A tag reader (<NUM>), comprising:
a communication controller (<NUM>) configured to control an output level of an output signal to be output from an antenna (<NUM>) for reading a wireless tag;
a communication interface (<NUM>) configured to communicate with a host device (<NUM>),
characterized by further comprising
a processor (<NUM>) configured to specify a minimum output level of the output signal at which the wireless tag can be read and transmit the minimum output level to the host device (<NUM>) through the communication interface (<NUM>).