Patent Publication Number: US-2023144063-A1

Title: Wireless tag communication device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-182418, filed on Nov. 9, 2021, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a wireless tag communication device. 
     BACKGROUND 
     In the related art, there is a wireless tag communication device for reading an RFID tag (hereinafter, also referred to as a wireless tag) at an unspecified position. The wireless tag communication device communicates with a specific RFID tag while changing the direction of an antenna by the operation of an operator. The wireless tag communication device notifies the operator of information indicating a position where the specific RFID tag is present, which is estimated based on the communication state with the specific RFID tag. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a block diagram schematically illustrating a configuration example of a control system in a wireless tag reading device according to at least one embodiment; 
         FIG.  2    is an external view illustrating a configuration example of an external appearance in the wireless tag reading device; 
         FIG.  3    is a diagram illustrating a display example of an operation guidance displayed while the wireless tag reading device is in operation in a search mode of an RFID tag; 
         FIG.  4    is a flowchart illustrating a first operation example for the wireless tag reading device; 
         FIG.  5    is a flowchart illustrating a second operation example for the wireless tag reading device; 
         FIG.  6    is a flowchart illustrating a third operation example for the wireless tag reading device; 
         FIG.  7    is a flowchart illustrating a fourth operation example for the wireless tag reading device; 
         FIG.  8    is a flowchart illustrating a first operation example of a process of estimating a tag direction by the wireless tag reading device; and 
         FIG.  9    is a flowchart illustrating a second operation example of the process of estimating a tag direction by the wireless tag reading device. 
     
    
    
     DETAILED DESCRIPTION 
     The wireless tag communication device described above is required to change the direction of the antenna by an operation of the operator in order to estimate a position where the specific RFID tag is present. However, there is a problem in that the operator may not know how to operate the wireless tag communication device in the related art in order to appropriately change the direction of the antenna. 
     In order to solve the above problem, an object is to provide a wireless tag communication device capable of guiding an operator to perform an appropriate operation. 
     In general, according to at least one embodiment, a wireless tag communication device includes a communication control circuit, a sensor, and a processor. The communication control circuit communicates with a wireless tag via an antenna. The sensor detects a variation amount of a direction of the antenna. The processor outputs an alert if the variation amount of the direction of the antenna detected by the sensor is less than a reference value. 
     Hereinafter, embodiments are described with reference to the drawings. 
     First, a configuration of a wireless tag reading device (wireless tag communication device)  10  according to at least one embodiment is described. 
       FIG.  1    is a block diagram schematically illustrating a configuration example of the wireless tag reading device  10  according to the embodiment. 
     The wireless tag reading device  10  according to the embodiment is a wireless tag communication device that communicates with a radio frequency identification (RFID) tag (e.g., wireless tag). The wireless tag reading device  10  reads tag information or the like recorded in the RFID tag by communicating with the RFID tag. The wireless tag reading device  10  estimates information relating to a position such as a direction or a distance where the RFID tag is present from the reading result of the RFID tag. The wireless tag reading device  10  notifies an operator of the information (e.g., direction or distance) relating to the position where the RFID tag is present, which is estimated from the reading result. 
     The RFID tag is a wireless communication device that is operated by radio waves (e.g., output signals) from the wireless tag reading device  10 . The RFID tag includes a processor, a memory, a communication circuit, an antenna, and the like. The RFID tag outputs a response signal including tag information recorded in the memory of the RFID tag in response to a read command from the wireless tag reading device  10 . For example, the RFID tag is attached to goods such as merchandises or components. With respect to the RFID tag attached to the goods, tag information including information for specifying the corresponding goods is recorded in the internal memory. 
     The wireless tag reading device  10  according to the embodiment is operated by the operator. The wireless tag reading device  10  is a device that changes a direction of an antenna  25  used to communicate with the RFID tag by the operation of the operator. For example, the wireless tag reading device  10  is a handy-type device that is held by the operator with the hands and operated. In addition, the wireless tag reading device  10  may be mounted on a moving body with which the operator operates the direction of the antenna. 
     The wireless tag reading device  10  according to the embodiment reads the RFID tag attached to the goods while changing the position and the direction of the antenna by the operation of the operator. The wireless tag reading device  10  reads the tag information recorded in the RFID tag by receiving the response signal from the RFID tag that is present in the reading area. The wireless tag reading device  10  acquires information such as a received signal strength indicator (RSSI) value indicating the intensity of the reception signal received from the RFID tag together with the tag information as the reading result of the RFID tag. 
     For example, the wireless tag reading device  10  operates as a search device for searching for goods to which an RFID tag is attached in a predetermined region such as a warehouse or a store. The wireless tag reading device  10  as the search device continuously reads an RFID tag as a search target while changing the position and the direction of the antenna by the operation of the operator. The wireless tag reading device  10  estimates the position (such as the direction or the distance) where the RFID tag is present based on the reading result of the RFID tag as the search target. In addition, the wireless tag reading device  10  may estimate the change of the relative position to the RFID tag based on the change of the intensity of the reception signal in time series. The wireless tag reading device  10  notifies the operator of the information such as the direction in which the RFID tag is present or the distance to the RFID tag, which is estimated from the reading result. 
     In the configuration example illustrated in  FIG.  1   , the wireless tag reading device  10  includes a processor  21 , a memory  22 , a sensor  23 , a communication control circuit  24 , the antenna  25 , a communication interface (I/F)  26 , an interface  27 , an information terminal  28 , and a power supply  29 . 
     The processor  21  controls each unit. The processor  21  includes, for example, an arithmetic circuit such as a central processing unit (CPU). The processor  21  implements the control of each unit and various data processes by executing programs. In addition, the processor  21  may include an internal memory. 
     The processor  21  performs various processes by executing the programs stored in the memory  22  or the like. For example, the processor  21  interprets a command from a host device  11  received by the communication I/F  26  and performs the process in response to the command. 
     The memory  22  includes various memories. For example, the memory  22  includes a memory such as a read-only memory (ROM), a random access memory (RAM), and a non-volatile memory (NVM). The ROM is a non-volatile memory on which rewriting cannot be performed. The ROM stores a program or the like that is executed by the processor  21 . The RAM is a volatile memory that temporarily stores data. The RAM is operated as a working memory or a buffer memory. The NVM is a non-volatile memory on which rewriting can be performed. The NVM stores information such as a program, control information, setting information, and a reading result. 
     The sensor  23  detects the movement of the corresponding wireless tag reading device  10 . The sensor  23  includes a sensor that detects the change in the direction of the antenna  25  provided in the wireless tag reading device  10 . For example, the sensor  23  is an acceleration sensor, a gyro sensor, a geomagnetic (direction) sensor, or the like. The sensor  23  may be configured to include a plurality of types of sensors. In addition, the sensor  23  may be provided in the information terminal  28 . 
     The communication control circuit  24  and the antenna  25  form an RFID interface that communicates with the RFID tag. 
     The communication control circuit  24  includes a control circuit for communicating with the RFID tag via the antenna  25 . The communication control circuit  24  causes the antenna  25  to transmit a transmission signal (e.g., radio wave) supplied from the processor  21  at a set output value. The antenna  25  outputs the transmission signal supplied from the communication control circuit  24  as the radio wave that the RFID tag can receive. 
     The communication control circuit  24  not only outputs the transmission signal to the antenna  25  but also supplies a signal received by the antenna  25  to the processor  21  as the received data. That is, the communication control circuit  24  receives the response signal from the RFID tag by the antenna  25  and processes and supplies the response signal (e.g., reception signal) received by the antenna  25  to the processor  21 . For example, the communication control circuit  24  supplies the tag information included in the reception signal from the RFID tag and the RSSI value indicating the intensity of the corresponding reception signal to the processor  21 . 
     The communication I/F  26  is an interface for communicating with the external device. The communication I/F  26  is a communication interface for communicating with the host device  11  such as the server. The communication I/F  26  may be an interface for wired communication and may be an interface for wireless communication. 
     The interface  27  is an interface for connecting to the information terminal  28 . The interface  27  may correspond to an interface included in the information terminal  28 . For example, the interface  27  is physically in contact with and is connected to the interface included in the information terminal  28  such as a universal serial bus (USB) interface or a local area network (LAN) interface. In addition, the interface  27  may perform wireless communication connection such as the Bluetooth (registered trademark) interface or a WiFi interface. 
     The information terminal  28  is a device including a display device  114 , an input device  115 , and the like. The information terminal  28  is operated as a user interface as a display device and an input device in the wireless tag reading device  10 . The information terminal  28  may be, for example, a portable information processing device such as a smart phone or a tablet personal computer (PC). 
     In the configuration example illustrated in  FIG.  1   , the information terminal  28  includes a processor  111 , a memory  112 , an interface (I/F)  113 , the display device  114 , the input device  115 , and the like. 
     The processor  111  controls each unit and performs data processing. The processor  111  is, for example, a CPU. The processor  111  implements various operations by performing the program stored in the memory  112 . 
     The interface  113  is an interface (e.g., second communication interface) for communication with the processor  21 . The interface  113  may correspond to the interface  27 . For example, the interface  113  is an interface such as LAN, USB, Bluetooth (registered trademark), or WiFi. 
     The display device  114  is a device that displays information. For example, the display device  114  displays detection result (for example, the position of the RFID tag) or the like of the RFID tag. The input device  115  is a device for the operator to input the operation instruction. The display device  114  and the input device  115  are configured, for example, with a display device with a touch panel. 
     The power supply  29  supplies the power supply electric power for operating the wireless tag reading device  10 . The power supply  29  supplies the electric power for operation to each unit of the wireless tag reading device  10 . In the handy-type wireless tag reading device  10 , the power supply  29  is configured, for example, with a rechargeable battery. 
     Subsequently, the configuration example of the communication control circuit  24  in the wireless tag reading device  10  according to the embodiment is described. 
     As illustrated in  FIG.  1   , the communication control circuit  24  includes a modulation circuit  41 , an amplification circuit  42 , a coupler  43 , an amplification circuit  44 , a demodulation circuit  45 , an output setting circuit  46 , a level detection circuit  47  and the like. By the configuration example illustrated in  FIG.  1   , the communication control circuit  24  processes the signals transmitted to the RFID tag and signals received from the RFID tag via the antenna  25 . 
     The modulation circuit  41  is a circuit that modulates the waveform signal (e.g., carrier wave) with the input data. The modulation circuit  41  modulates the carrier waves with the transmission data given from the processor  21 . The amplification circuit  42  is an amplification circuit on the transmission side that amplifies the input signal. The amplification circuit  42  amplifies the output signal of the modulation circuit  41 . The coupler  43  includes a circuit that supplies the output signal of the amplification circuit  42  to the antenna  25 . According to these configurations, the communication control circuit  24  outputs the carrier waves modulated with the transmission data from the antenna  25 . 
     The RFID tag receives the radio wave as the transmission signal transmitted from the antenna  25 . For example, the RFID tag recognizes the read command included in the transmission signal transmitted from the antenna  25 . If the read command is recognized, the RFID tag outputs the data (e.g., tag information) stored in the memory of the own device, for example, by backscatter modulation as the radio waves. 
     The antenna  25  receives the radio waves as the reception signals output by the RFID tag. The coupler  43  is a circuit that acquires the reception signals received by the antenna  25  and supplies the acquired reception signals to the amplification circuit  44 . The coupler  43  is, for example, a directional coupler or an isolator. The amplification circuit  44  is an amplification circuit on the reception side that amplifies the input signal. The amplification circuit  44  amplifies the reception signal received by the antenna  25 . The demodulation circuit  45  is a circuit that demodulates the data overlapped with the waveform signals (e.g., carrier waves). The demodulation circuit  45  demodulates the data (e.g., tag information) included in the reception signal that is amplified by the amplification circuit  44 . 
     The antenna  25  may transmit and receive the radio waves for the communication with the RFID tag. The antenna  25  may transmit the transmission signals that are supplied to the RFID tag and receive the radio waves output by the RFID tag as the reception signals. According to the present embodiment, the antenna  25  has directivity. The antenna  25  is disposed so as to transmit an electromagnetic wave toward a reading area having a center thereof in the direction in which the directivity is the strongest (a direction a shown in  FIG.  2   ). The wireless tag reading device  10  is configured to communicate with the RFID tags attached to all merchandises arranged in the reading area via the antenna  25 . The antenna  25  is, for example, a planar antenna. However, the antenna  25  is not limited to the specific configuration. 
     The output setting circuit  46  is a circuit that sets the intensity (e.g., output value) of the output signal. The output setting circuit  46  controls the amplification circuit  42  so that the intensity of the output signal has a set output value. The amplification circuit  42  amplifies the signal supplied from the modulation circuit  41  to be the output value set by the output setting circuit  46  and outputs the signal to the coupler  43 . Accordingly, the antenna  25  transmits the output signals (e.g., radio waves) having the output value set by the output setting circuit  46  which is supplied from the amplification circuit  42  via the coupler  43 . 
     The level detection circuit  47  is a circuit that detects (e.g., measures) the intensity of a signal. The level detection circuit  47  detects the intensity of the signal input to the amplification circuit  44 . The reception signal received by the antenna  25  is input to the amplification circuit  44  via the coupler  43 . That is, the level detection circuit  47  detects the information for specifying the RSSI value indicating the intensity of the reception signal (e.g., the response signal from the RFID tag) received by the antenna  25 . 
     Subsequently, the operation example of the wireless tag reading device  10  according to the embodiment is described. 
       FIG.  2    is a diagram illustrating an external appearance configuration example of the wireless tag reading device  10  according to the embodiment. 
     The wireless tag reading device  10  illustrated in  FIG.  2    is a handy-type device that is operated in a state of being gripped by the operator. The wireless tag reading device  10  illustrated in  FIG.  2    operates as a search device that searches, for example, for an RFID tag or for goods to which the RFID tag is attached. 
     In the configuration example illustrated in  FIG.  2   , the wireless tag reading device  10  is configured to be operated in a state in which the information terminal  28  is set to a reader device (e.g., base device)  120 . The reader device  120  is a device including each configuration illustrated in  FIG.  1    excluding the information terminal  28 . The reader device  120  includes a housing to which the antenna  25  is installed. For example, in the reader device  120 , the antenna  25  is provided so that the directivity is the strongest in the direction of the arrow a illustrated in  FIG.  2   . Here, the direction of the arrow a is the front (e.g., forward) direction of the wireless tag reading device  10 . In addition, the front direction of the wireless tag reading device  10  is the direction of the antenna  25 . 
     In addition to the configuration of the control system illustrated in  FIG.  1   , the reader device  120  includes a grip portion  121  and a holding portion  122 . The grip portion  121  is a portion that the operator grips. The holding portion  122  is configured with a tool for holding the information terminal  28 . The holding portion  122  holds the information terminal  28  so that the display screen of the display device  114  faces the operator who grips the grip portion  121 . The wireless tag reading device  10  is operated by the operator who grips the grip portion  121  in a state in which the information terminal  28  is set to the holding portion  122 . 
     The wireless tag reading device  10  is moved by being held by the operator with a hand in a state in which the information terminal  28  is set. The wireless tag reading device  10  continuously reads the RFID tag while being operated by the operator. For example, the operator who grips the grip portion  121  changes the direction of the antenna  25  provided to the reader device  120 . The wireless tag reading device  10  detects the change in the direction of the antenna  25  caused by the operation of the operator with the sensor  23 . The wireless tag reading device  10  reads the RFID tag while detecting the change in the direction of the antenna. 
     The wireless tag reading device  10  stores the reading result obtained by repeatedly reading the specific RFID tag while changing the direction of the antenna  25  in response to the operation of the operator. For example, the wireless tag reading device  10  acquires the reading result obtained by reading the specific RFID tag while changing the direction of the antenna  25 . The wireless tag reading device  10  acquires the information such as the RSSI value indicating the intensity of the signal received from the RFID tag as the reading result, in addition to the tag information acquired from the RFID tag. In addition, the wireless tag reading device  10  also acquires the information or the like indicating the change amount of the direction detected by the sensor  23 , as the reading result. 
     The wireless tag reading device  10  estimates the direction (e.g., tag direction) in which the RFID tag is present from the reading result of the RFID tag. For example, the wireless tag reading device  10  estimates the median value of the ranges of the directions (e.g., the directions of the antenna) in which the specific RFID tag is read, as the tag direction in which the corresponding RFID tag is present. In addition, the wireless tag reading device  10  may estimate the direction (e.g., the direction of the antenna) in which the RSSI value becomes the maximum from the reading result obtained by reading the specific RFID tag as the tag direction in which the corresponding RFID tag is present. 
     The wireless tag reading device  10  detects the change in the direction of the antenna  25  by the sensor  23 . If the change amount of the direction of the antenna  25  that is detected by the sensor  23  is the reference value or less, the wireless tag reading device  10  notifies an alert prompting the operation of changing the direction of the antenna  25 . For example, if the change in the direction of the antenna  25  is the reference value or less, the wireless tag reading device  10  displays the operation guidance of prompting the operation of changing the direction of the antenna  25  on the display device  114 . 
       FIG.  3    is a diagram illustrating the display example of the operation guidance displayed on the display device  114  by the wireless tag reading device  10 . 
     The display example illustrated in  FIG.  3    is an example in which the operation guidance is displayed on the display screen that displays the search result of the RFID tag. 
     In the search mode for searching for the specific RFID tag, the wireless tag reading device  10  displays the display screen for displaying the search result of the RFID tag illustrated in  FIG.  3    on the display device  114 . In the search mode, the wireless tag reading device estimates the position (e.g., the direction and the distance) where the specific RFID tag is present from the reading result of the RFID tag. The wireless tag reading device  10  displays the information indicating the position of the specific RFID tag that is estimated from the reading result of the RFID tag on the display device  114 , as the search result. 
     In the display example illustrated in  FIG.  3   , the display device  114  displays a reading area  202  read by the wireless tag reading device  10  in a concentric circle  201  about the position of the wireless tag reading device  10 , in an overlapping manner. For example, the display device  114  displays the reading area  202  on the concentric circle  201  so that the upper portion becomes the forward direction (e.g., the direction of the arrow a illustrated in  FIG.  2   ) of the wireless tag reading device  10 . The display device  114  displays a mark  203  indicating the position of the RFID tag read in the reading area  202  on the concentric circle  201 . 
     For example, the wireless tag reading device  10  estimates the distance from the wireless tag reading device  10  to the RFID tag based on the RSSI value and the like included in the reading result of the RFID tag. The display device  114  displays the mark  203  at the position corresponding to the estimated direction and distance on the concentric circle  201  about the position of the wireless tag reading device  10 . Accordingly, the display device  114  can notify the operator of the direction and the distance where the RFID tag is present by displaying the mark  203  on the reading area  202 . 
     In addition, in the display example illustrated in  FIG.  3   , the display device  114  displays a display field  211 , a display field  212 , a search start button  231 , and a completion button  232 . 
     The display field  211  displays the product number of the RFID tag as the search target. The display field  212  displays a serial number of the RFID tag as the search target. 
     The search start button  231  and the completion button  232  are buttons that enables the operator to make instruction with the touch panel as the input device  115 . The search start button  231  is a button used by the operator to instruct the search start of the RFID tag. The completion button  232  is a button used by the operator to instruct the completion of the search for the RFID tag. The operator can search for the RFID tag by the operation of the wireless tag reading device  10  while looking at the screen illustrated in  FIG.  3   . 
     Further, in the display example illustrated in  FIG.  3   , the display device  114  displays the operation guidance for prompting the operation of the wireless tag reading device  10  in a display field  241 . For the search for the RFID tag, the wireless tag reading device  10  is required to perform the reading of the RFID tag while changing the direction of the antenna  25 . The wireless tag reading device  10  according to the embodiment notifies the alert prompting the operation of changing the direction of the antenna  25 . The operation guidance displayed in the display field  241  illustrated in  FIG.  3    is an example of the alert prompting the operation of changing the direction of the antenna. 
     For example, if the variation amount of the direction of the antenna  25  (or the base device  120  including the antenna  25 ) is the predetermined threshold value or less, the wireless tag reading device  10  displays the operation guidance for prompting the operation of changing the direction of the antenna  25  on the display device  114 . If the search mode is in operation, the wireless tag reading device  10  displays the display field  241  indicating the operation guidance on the display screen as illustrated in  FIG.  3   . In the example illustrated in  FIG.  3   , the wireless tag reading device  10  displays “Please swing the reader (wireless tag reading device) left and right” in the display field  241 . 
     Subsequently, the operation of the wireless tag reading device  10  according to the embodiment is described. 
       FIG.  4    is a flowchart illustrating a first operation example of the wireless tag reading device  10  according to the embodiment. 
     The processor  21  of the wireless tag reading device  10  is operated in the search mode by the operation of the operator. The processor  21  receives the setting of the RFID tag for which the operator desires to search. After the RFID tag as the search target is set, the processor  21  receives the instruction of the search start by the operator. For example, the processor  21  receives the instruction of the search start by the search start button  231  on the display screen as illustrated in  FIG.  3    which is displayed on the display device  114 . 
     The processor  21  of the wireless tag reading device  10  performs an RFID tag reading process in response to the instruction of the search start by the operator (ACT  11 ). The processor  21  stores the reading result of the RFID tag that is in the reading area (e.g., communication area) by the communication control circuit  24  and the antenna  25  in the memory  22 . 
     As the reading result of each RFID tag, the processor  21  stores, for example, information such as tag information, direction (e.g., reading direction), the output value, and the RSSI value, in the memory  22 . 
     The tag information is information output by the RFID tag in response to the response request (e.g., read command) from the wireless tag reading device  10 . The tag information is configured, for example, with a header, a merchandise code, and a serial number. The header is information indicating a format of the tag information or a range of the merchandise code in the tag information. The merchandise code is information for specifying the merchandise (e.g., goods). The serial number is an identification number attached to each merchandise. 
     The direction (e.g., reading direction) is information indicating the direction (e.g., the direction of the wireless tag reading device  10 ) of the antenna  25  if the RFID tag is read. The processor  21  acquires the information indicating the direction of the antenna  25  that is detected by the sensor  23 . For example, the processor  21  acquires the information indicating the direction of the antenna  25  by detecting the variation amount (e.g., variation angle) of the direction with respect to a direction as a reference, with the sensor  23 . 
     The output value is the intensity of the output signals (e.g., radio waves) output from the antenna  25  if the RFID tag is read. The output value is set according to the instruction from the processor  21  by the output setting circuit  46  of the communication control circuit  24 . The processor  21  specifies the output value set in the communication control circuit  24 . 
     The RSSI value is information indicating the intensity of the reception signal received from each RFID tag. The RSSI value is detected by the level detection circuit  47  from the reception signal of each RFID tag. The processor  21  acquires the RSSI value that is detected by the level detection circuit  47 . 
     If the reading result of each RFID tag in the reading area is acquired, the processor  21  measures (e.g., detects) a swing amount that is the change amount of the direction of the antenna  25  (ACT  12 ). The processor  21  measures (e.g., detects) the swing amount based on the variation amount of the direction detected by the sensor  23 . For example, the processor  21  measures the swing amount by the variation amount (e.g., difference) between the direction if the RFID tag is read and the direction before predetermined time. In addition, the processor  21  may measure a swing amount by the difference (e.g., variation amount) between the direction if the search starts and the direction if the RFID tag is read. In addition, the processor  21  may measure the swing amount by the difference between the direction if the RFID tag is read and the direction if the RFID tag is read right before. 
     After the swing amount is measured, the processor  21  determines whether the RFID tag as the search target has been read (ACT  13 ). If the RFID tag as the search target has not been read (ACT  13 , NO), the processor  21  proceeds to ACT  19  described below. 
     If the RFID tag as the search target is read (ACT  13 , YES), the processor  21  estimates the direction (e.g., tag direction) where the RFID tag as the search target is present (ACT  14 ). The example of the process of estimating the tag direction is described below. However, the processes may be performed with the process of estimating the tag direction of ACT  15  omitted. 
     If the tag direction is estimated, the processor  21  stores the reading result of the RFID tag as the search target including the estimating result of the tag direction in the memory  22  (ACT  15 ). Accordingly, the reading results of the RFID tag as the search target are accumulated in the memory  22 . 
     If the reading result of the RFID tag as the search target is stored, the processor  21  determines whether the communication state with the RFID tag as the search target exceeds the reference level (ACT  16 ). For example, the processor  21  determines whether the RSSI value of the reception signal from the RFID tag as the search target exceeds the reference level, as the communication state. Here, the processor  21  may set the reference level to be compared with the communication state according to the output value set in the communication control circuit  24 . 
     If the communication state exceeds the reference level (ACT  16 , YES), the processor  21  determines whether the output value (e.g., the magnitude of the output signal) of the transmission signal set in the communication control circuit  24  is a minimum value that can be set (ACT  17 ). 
     If the output value of the transmission signal is not the minimum value (ACT  17 , YES), the processor  21  reduces the output value of the output signal set in the communication control circuit  24  (ACT  18 ). 
     Here, the processor  21  stepwisely reduces the output value until the value becomes the minimum value that can be set. If the output value is reduced, the reading area of the RFID tag by the wireless tag reading device  10  is reduced. That is, the processor  21  stepwise limits the reading area where the RFID tag as the search target has been read by stepwise reducing the output value. Accordingly, the wireless tag reading device  10  can limitedly specify the position where the RFID tag as the search target is present. 
     If the output value of the transmission signal is the minimum value (ACT  17 , NO), the processor  21  notifies the detection result of the RFID tag as the search target (ACT  22 ). For example, the processor  21  displays the information indicating the position of the RFID tag as the search target which is estimated from the reading result at the minimum output value on the display device  114 . In addition, the processor  21  may notify the host device  11  of the information indicating the detection result of the RFID tag as the search target by the communication interface  26 . 
     The processor  21  sets the reference value as the threshold value with respect to the swing amount according to the reading condition of the RFID tag, the estimating result of the tag direction, the output value, the estimated distance to the RFID tag, and the like (ACT  19 ). 
     For example, if the RFID tag as the search target is not read (ACT  13 , NO), the processor  21  sets the predetermined reference value with respect to the swing amount for reading the wide area (ACT  19 ). 
     In addition, if the tag direction is estimated, the processor  21  sets the reference value of the swing amount based on the estimated tag direction. For example, if the communication state is the reference level or less (ACT  16 , NO), or the output value of the transmission signal is reduced, the processor  21  sets the reference value of the swing amount based on the estimated tag direction. 
     Further, the processor  21  may set the reference value with respect to the swing amount according to various conditions. As a specific example, the processor  21  may set the reference value according to the output value of the transmission signal set in the communication control circuit  24 . For example, the processor  21  reduces the reference value with respect to swing amount as the output value of the transmission signal is reduced. In addition, the processor  21  may set the reference value according to the distance to the RFID tag estimated from the RSSI value or the like. For example, the processor  21  reduces the reference value as the distance to the RFID tag is closer. 
     After the reference value with respect to the swing amount is set, the processor  21  determines whether the measured swing amount is less than the set reference value (ACT  20 ). If the swing amount is equal to or more than the reference value (ACT  20 , NO), the processor  21  returns to ACT  11  and performs the processes described above again. 
     If the swing amount is less than the reference value (ACT  20 , YES), the processor  21  outputs the alert for prompting the operator to perform the operation of increasing the swing amount (ACT  21 ). For example, the processor  21  displays the operation guidance as illustrated in the display field  241  of  FIG.  3    on the display device  114  as the alert. In addition, as the alert, a sound such as an alarm or voice guidance may be output from a speaker or the like included in the information terminal  28 . The alert may prompt the operator to perform the operation of changing the direction of the antenna  25  as significantly as the reference value or more. 
     As described above, if the swing amount indicating the change amount of the direction of the antenna is the reference value or less, the wireless tag reading device notifies the alert prompting the operation of changing the direction of the antenna. Accordingly, the operator who operates the wireless tag reading device can appropriately perform the operation of changing the direction of the antenna for an efficient search for the RFID tag. 
     In addition, the wireless tag reading device sets the reference value with respect to the swing amount indicating the change amount of the direction of the antenna according to the condition. If the swing amount is less than the reference value set according to the condition, the wireless tag reading device notifies the operator of the alert prompting the operation of changing the direction of the antenna. Accordingly, the wireless tag reading device can notify the operator of the alert efficiently enabling the search for the RFID tag as the search target according to the condition. 
     Subsequently, a second operation example of the wireless tag reading device  10  according to the embodiment is described. 
       FIG.  5    is a flowchart illustrating the second operation example of the wireless tag reading device  10  according to the embodiment. 
     The second operation example is different from the first operation example described above in that the swing amount is measured after the RFID tag as the search target is read. Each process of ACTS  11  to  22  illustrated in  FIG.  5    may be the same as each process of ACTS  11  to  22  illustrated in  FIG.  4    described as the first operation example, and thus detailed description is omitted. 
     The processor  21  of the wireless tag reading device  10  performs the RFID tag reading process in response to the instruction of the search start by the operator (ACT  11 ). If the reading result of each RFID tag in the reading area is acquired, the processor  21  determines whether the RFID tag as the search target has been read (ACT  13 ). If the RFID tag as the search target has not been read (ACT  13 , NO), the processor  21  returns to ACT  11  and reads the RFID tag, again. 
     If the RFID tag as the search target is read (ACT  13 , YES), the processor  21  estimates the direction (tag direction) where the RFID tag as the search target is present (ACT  14 ). If the tag direction is estimated, the processor  21  stores the reading result of the RFID tag as the search target including the estimating result of the tag direction in the memory  22  (ACT  15 ). 
     After the reading result of the RFID tag as the search target is stored, the processor  21  determines whether the communication state with the RFID tag as the search target exceeds the reference level (ACT  16 ). If the communication state exceeds the reference level (ACT  16 , YES), the processor  21  determines whether the output value of the transmission signal set in the communication control circuit  24  is the minimum value that can be set (ACT  17 ). 
     If the output value is the minimum value (ACT  17 , NO), the processor  21  notifies the detection result of the RFID tag as the search target (ACT  22 ). 
     If the output value is not the minimum value (ACT  17 , YES), the processor  21  reduces the output value of the transmission signal set in the communication control circuit  24  (ACT  18 ). 
     If the output value is reduced, or the communication state is the reference level or less (ACT  16 , NO), the processor  21  measures (e.g., detects) the swing amount that is the change amount of the direction of the antenna  25  (ACT  31 ). In the same manner as in ACT  12  described above, the processor  21  measures (e.g., detects) the swing amount based on the variation amount of the direction (e.g., reading direction) detected by the sensor  23 . However, in the second operation example, the processor  21  measures the swing amount with respect to the estimated tag direction. 
     After the swing amount is measured, the processor  21  sets the reference value as the threshold value with respect to the swing amount (ACT  19 ). In the second operation example, the processor  21  sets the reference value with respect to the estimated tag direction. In addition, the processor  21  sets the reference value according to the output value of the transmission signal set in the communication control circuit  24 . Further, the processor  21  may set the reference value in consideration of the estimated distance to the RFID tag as the search target. 
     As the reference value with respect to the swing amount is set, the processor  21  determines whether the measured swing amount is less than the set reference value (ACT  20 ). In the second operation example, the reference value with respect to the tag direction is set. Therefore, the processor  21  determines whether the swing amount with respect to the tag direction is equal to or more than the reference value. 
     If the swing amount is less than the reference value (ACT  20 , YES), the processor  21  outputs the alert for prompting the operation of increasing the swing amount with respect to the tag direction (ACT  21 ). 
     If the swing amount is equal to or more than the reference value (ACT  20 , NO), the processor  21  returns to ACT  11  and performs the process described above again. 
     According to the second operation example as above, the wireless tag reading device estimates the tag direction where the RFID tag as the search target is present if the RFID tag as the search target can be read. The wireless tag reading device measures the swing amount indicating the change amount of the direction of the antenna with respect to the tag direction. The wireless tag reading device outputs the alert of prompting the increase of the swing amount with respect to the tag direction if the swing amount is less than the reference value with respect to the tag direction. 
     Accordingly, according to the second operation example, it is possible to prompt the operator to perform the operation of causing the swing amount with respect to the tag direction of the RFID tag as the search target to be equal to or more than the reference value. As a result, the wireless tag reading device can efficiently search for the RFID tag as the search target by the operation by the operator in response to the alert. 
     Subsequently, a third operation example of the wireless tag reading device  10  according to the embodiment is described. 
       FIG.  6    is a flowchart illustrating the third operation example of the wireless tag reading device  10  according to the embodiment. 
     The third operation example is different from the first operation example described above in that the reading of the RFID tag starts if the swing amount is equal to or more than the reference value. Each process of ACTS  11  to  22  illustrated in  FIG.  6    may be the same as each process of ACTS  11  to  22  illustrated in  FIG.  4    as the first operation example, and thus detailed description thereof is omitted. 
     In the third operation example, the processor  21  of the wireless tag reading device  10  measures the swing amount indicating the variation amount of the direction of the antenna after the RFID tag as the search target is set (ACT  41 ). If the swing amount is measured, the processor  21  determines whether the measured swing amount is equal to or more than the reference value (the reference value of the search start) for starting the search (ACT  42 ). 
     If the swing amount is less than the reference value for the search start (ACT  42 , NO), the processor  21  outputs the alert for prompting the operation of increasing the variation amount of the direction of the antenna (ACT  43 ). For example, the processor  21  displays the operation guidance for prompting the operation of shaking the reader device  120  left and right on the display device  114 . 
     If the swing amount is the reference value for the search start or more (ACT  42 , YES), the processor  21  starts the RFID tag reading process and performs the operation of ACTS  11  to  22  described in the first operation example. 
     Subsequently, a fourth operation example of the wireless tag reading device  10  according to the embodiment is described. 
       FIG.  7    is a flowchart illustrating the fourth operation example of the wireless tag reading device  10  according to the embodiment. 
     The fourth operation example is different from the second operation example described above in that the reading of the RFID tag is started if the swing amount is the reference value for the search start or more. Each process of ACTS  11  to  22  illustrated in  FIG.  6    may be the same as each process of ACTS  11  to  22  in  FIG.  5    described in the first and second operation examples and thus the detailed description thereof is omitted. 
     In the fourth operation example, the processor  21  of the wireless tag reading device  10  measures the swing amount indicating the variation amount of the direction of the antenna after the RFID tag as the search target is set (ACT  41 ). If the swing amount is measured, the processor  21  determines whether the measured swing amount is equal to or more than the reference value (the reference value of the search start) for starting the search (ACT  42 ). 
     If the swing amount is less than the reference value for the search start (ACT  42 , NO), the processor  21  outputs the alert of prompting the operation of increasing the variation amount of the direction of the antenna (ACT  43 ). For example, the processor  21  displays the operation guidance of prompting the operation of shaking the reader device  120  left and right on the display device  114 . 
     If the swing amount is the reference value for the search start or more (ACT  42 , YES), the processor  21  starts the RFID tag reading process and performs the operations of ACTS  11  to  22  and  31  described in the second operation example. 
     According to the third and fourth operation examples as above, the wireless tag reading device starts to read the RFID tag after the confirmation of the swing amount that is equal to or more than the predetermined reference value. If the swing amount is less than the reference value for the search start, the wireless tag reading device outputs the alert for prompting the operation of increasing the swing amount indicating the change amount of the direction of the antenna. 
     Accordingly, the wireless tag reading device can output the alert for prompting the increase of the swing amount, while the swing amount is small. In addition, the wireless tag reading device can start to read the RFID tag after the swing amount becomes equal to or more than the predetermined reference value. As a result, the wireless tag reading device can prompt the operation of definitely causing the swing amount to be equal to or more than the reference value, if the search of the RFID tag is started. 
     Subsequently, the process of estimating the tag direction where the RFID tag as the search target is present by the wireless tag reading device  10  according to the embodiment is described. 
       FIG.  8    is a flowchart illustrating a first operation example of a process of estimating the tag direction by the wireless tag reading device  10  according to the embodiment. 
     The processor  21  of the wireless tag reading device  10  reads the reading result of the RFID tag as the search target stored in the memory  22  (ACT  81 ). Information indicating the direction if the corresponding RFID tag is read is included in the reading result of the RFID tag stored in the memory  22 . The direction if the RFID tag as the search target is read is detected by the sensor  23 . 
     The processor  21  specifies all the directions if the RFID tag as the search target is read (ACT  82 ). The processor  21  calculates ranges of all the directions where the RFID tag as the search target is read (ACT  83 ). The processor  21  estimates the center of the ranges of the directions as the tag direction (ACT  84 ). 
       FIG.  9    is a flowchart illustrating the second operation example of the process of estimating the tag direction by the wireless tag reading device  10  according to the embodiment. 
     The processor  21  of the wireless tag reading device  10  reads the reading result of the RFID tag as the search target stored in the memory  22  (ACT  91 ). The RSSI value indicating the intensity of the reception signal if the corresponding RFID tag is read is included in the reading result of the RFID tag stored in the memory  22 . The information indicating the direction if the corresponding RFID tag is read and the RSSI value indicating the intensity of the reception signal are included in the reading result of the RFID tag stored in the memory  22 . 
     The processor  21  specifies the reading result in which the RSSI value is maximum from the reading results of the RFID tag as the search target (ACT  92 ). The processor  21  estimates the direction if the RSSI value is the maximum as the tag direction based on the reading result in which the RSSI value is the maximum (ACT  84 ). 
     As above, the wireless tag reading device according to the embodiment includes the communication interface, the sensor, and the processor. The communication interface communicates with the RFID tag via the antenna. The sensor detects the swing amount indicating the variation amount of the direction of the antenna. The processor causes the device such as the display device to output the alert for prompting the increase of the swing amount if the swing amount detected by the sensor is less than the predetermined reference value. Accordingly, the wireless tag reading device according to the embodiment can prompt the operation of causing the variation amount of the direction of the antenna to be the variation amount equal to or more than the reference value. 
     Further, in the wireless tag reading device according to the embodiment, the processor estimates the tag direction where the RFID tag read by the communication interface is present. The processor measures the swing amount with respect to the tag direction estimated if the tag information of the RFID tag as the search target is read. The processor outputs the alert if the swing amount with respect to the tag direction is less than the reference value. Accordingly, the wireless tag reading device according to the embodiment can prompt the operation so that the variation amount of the direction of the antenna with respect to the direction where the tag is estimated to be present is equal to or more than the reference value. 
     In addition, in the wireless tag reading device according to the embodiment, the processor sets the reference value with respect to the swing amount according to the output value of the transmission signal transmitted to the RFID tag. Accordingly, the wireless tag reading device can prompt the operation with the proper swing amount according to the output value of the transmission signal. 
     In addition, in the wireless tag reading device according to the embodiment, the processor estimates the distance to the RFID tag as the search target. The processor can set the reference value with respect to the swing amount according to the distance to the RFID tag. Accordingly, the wireless tag reading device can prompt the operation with the proper swing amount according to the estimated distance to the RFID tag as the search target. 
     In addition, according to the embodiment described above, a case where the program executed by the processor is stored in advance in the memory in the device is described. However, the program executed by the processor may be downloaded from the network to the device or may be installed from the storage medium to the device. As the storage medium, a storage medium that can store programs such as CD-ROM and that can be read by the device may be used. In addition, functions obtained by installation or download in advance may be implemented in cooperation with an operating system (OS) or the like inside the device. 
     In addition, according to the embodiment described above, the operation of causing the processor  21  to perform a search process is described. However, the processor  111  of the information terminal  28  may transmit the command to the processor  21  so that the processor  111  may be the main body of the operation to perform the search process. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.