Wireless tag reading apparatus

A wireless tag reading apparatus includes an antenna, an actuator, a phase detector, and a processor. The actuator is configured to move the antenna along a predetermined effective detection region. The processor is configured to calculate a first phase difference based on a phase of a response wave signal received by the antenna at a first plurality of antenna positions, and a second phase difference based on the phase of the response wave signal received by the antenna at a second plurality of antenna positions. The processor is configured to calculate first and second incident angles of the response wave signal for the antenna at the first and second plurality of antenna positions, respectively, based on the first and second phase differences, respectively. The processor is configured to determine whether or not the wireless tag is in the predetermined effective detection region based on the first and second incident angles.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2018-187454, filed on Oct. 2, 2018, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a wireless tag reading apparatus.

BACKGROUND

A conventional reading apparatus reads information from a wireless tag, such as an RFID (Radio Frequency Identification) tag, that has been attached to an item or article.

In such a reading apparatus, a metal container is used to accommodate the tagged at. A wireless tag reader and an antenna are arranged for reading information from the RFID tag in the container through wireless communication. The reading apparatus includes an antenna drive section, and can change the position of the antenna using the antenna drive section.

The electromagnetic waves radiated from the antenna do not leak to the outside of the metal container of the reading apparatus. With this arrangement, the reading apparatus can at one time read information from several RFID tags attached to different articles stored within the apparatus. On the other hand, the reading apparatus cannot read information from an RFID tag outside of the apparatus.

DETAILED DESCRIPTION

According to an embodiment, a wireless tag reading apparatus includes an antenna, an actuator, a phase detector, and a processor. The antenna is configured to receive a response wave signal from a wireless tag. The actuator is configured to move the antenna in a direction along a predetermined effective detection region. The phase detector is configured to detect a phase of the response wave signal received by the antenna. The processor is configured to calculate a first phase difference based on the phase of the response wave signal received by the antenna at a first plurality of antenna positions that are proximate to each other, and a second phase difference based on the phase of the response wave signal received by the antenna at a second plurality of antenna positions that are proximate to each other. The processor is configured to calculate a first incident angle of the response wave signal for the antenna at the first plurality of antenna positions based on the first phase difference, and a second incident angle of the response wave signal for the antenna at the second plurality of antenna positions based on the second phase difference. The processor is configured to determine whether the wireless tag is in the predetermined effective detection region based on the first incident angle and the second incident angle, and register tag information represented by the response wave signal upon determining that the wireless tag is in the predetermined effective detection region.

Hereinafter, example embodiments are described with reference to the accompanying drawings.

A configuration of a wireless tag reading apparatus1is described.

FIG. 1is a diagram schematically illustrating the wireless tag reading apparatus1. For example, the wireless tag reading apparatus1is used for performing registration of an article P. In this context, the registration processing may be associated as retail sales registration, inventory tracking, or an inspection service. For example, the wireless tag reading apparatus1is installed in a retail store or a warehouse.

The wireless tag reading apparatus1is arranged on a table2. One or more articles P to which RFID tags T are attached can be placed on the table2. The table2includes a horizontal upper surface21and a lower surface22opposite to the upper surface21. An article P may be placed on a shelf or the like, or may be stacked on the upper surface21of the table2. The RFID tag T includes an antenna and a microchip (packaged integrated circuit), including a storage section capable of storing information, on a resin base. The RFID tag T is an example of a wireless tag.

The wireless tag reading apparatus1reads information from an RFID tag T attached to an article P placed on the upper surface21of the table2. The wireless tag reading apparatus1reads identification information such as a tag ID unique to the RFID tag T and other information recorded in the RFID tag T.

The wireless tag reading apparatus1determines whether or not the RFID tag T is in a predetermined area A above the upper surface21of the table2as described below. The predetermined area A is indicated by a dot-and-dash line. The predetermined area A is a three-dimensional virtual region above the upper surface21of the placing table2. In general, the size and shape of the predetermined area A is not limited in any particular manner. The predetermined area A is set as a region from which the wireless tag reading apparatus1is intended to read information from the RFID tags T for purposes of registration. Any RFID tag T present in the predetermined area A is considered to be a tag for which it desired to be read/registered. Those RFID tags T outside of the predetermined area A are not presently targets for reading/registration.

If an RFID tag T is in the predetermined area A, the wireless tag reading apparatus1reads and registers the information recorded in the RFID tag T. In this way, the wireless tag reading apparatus1can register the article P to which the RFID tag T is attached. On the other hand, if an RFID tag T is outside of the predetermined area A, the wireless tag reading apparatus1ignores/discards any information read from such an RFID tag T. In this way, the wireless tag reading apparatus1does not register any article P outside the predetermined area A.

FIG. 2is a block diagram illustrating the wireless tag reading apparatus1.

The wireless tag reading apparatus1includes an antenna11, a wireless tag communication unit12, a pedestal13, a support member14, a drive unit15and a processing unit16.

The antenna11is positioned on the lower surface22side of the table2. The antenna11radiates electromagnetic waves from the lower surface22side of the table2towards the upper surface21side. The antenna11can be an antenna which radiates circular polarization, such as a patch antenna or a sequential array, but the functioning and shape of the antenna are not limited.

The antenna11receives a response wave (may be referred to as a response wave signal) from the RFID tag T as explained further below. In this example, the RFID tag T is activated by receiving power supplied by the electromagnetic waves radiated from the antenna11. The RFID tag T in turn radiates a response wave. In this way, the antenna11receives the response wave from the RFID tags T. The response wave provides information, such as identification information, previously recorded in the RFID tag T. The information be a tag ID or other information.

The antenna11is positioned on the lower surface22side of the table2, but it is not limited thereto. The antenna11may be positioned on the upper surface21side of the table2so as to radiate electromagnetic waves in the horizontal direction. The wireless tag reading apparatus1is not limited to including only one antenna11, and may include two or more antennas.

The wireless tag communication unit12is electrically connected to the antenna11. The wireless tag communication unit12radiates electromagnetic waves through the antenna11to communicate with the RFID tag T. The wireless tag communication unit12communicates with the RFID tag T via the antenna11to receive the response wave received by the antenna11. The wireless tag communication unit12demodulates the information transmitted through the response wave to obtain information including the identification information recorded in the RFID tag T such as the tag ID and other information. In this way, the wireless tag communication unit12reads the information recorded in the RFID tag T from the RFID tag T. The wireless tag communication unit12sends the information recorded in the RFID tag T to the processing unit16. For example, the wireless tag communication unit12is a reader/writer.

The wireless tag communication unit12includes a phase detector121. The phase detector121detects a phase of the response wave received by the antenna11. The phase detector121sends the information indicating the phase of the response wave to the processing unit16. The information indicating the phase of the response wave is also referred to as phase information. For example, the phase detector121sends the phase information to the processing unit16in association with the information recorded in the RFID tag T. The phase detector121may be an analog circuit or a digital circuit. Instead of this, the phase detector121may obtain the phase of the response wave through calculation from signal information obtained by a detector in the wireless tag communication unit12. The configuration of the phase detector121is not limited. The phase detector121may be referred to as a phase detection section.

The pedestal13is fixed to the antenna11. The pedestal13is movable horizontally with the antenna11is fixed thereon.

The support member14fixes the pedestal13. The support member14is movable horizontally in a state in which the pedestal13is fixed thereon.

The drive unit15is mechanically connected to the support member14. The drive unit15moves the support member14under the control of the processing unit16. The drive unit15may be referred to as an actuator. The drive unit15moves the support member14such that the antenna11moves within a range facing the predetermined area A in the vertical direction. For example, the drive unit15moves the support member14such that the position of the antenna11moves within a range facing a virtual surface of the predetermined area A on the upper surface21of the table2. In this way, the drive unit15can change the position of the antenna11.

The drive unit15obtains information indicating the position of the antenna11that moves as the support member14moves. The information indicating the position of the antenna11is also referred to as position information of the antenna11. For example, the position information of the antenna11indicates coordinates on the basis of any position; however, it is not limited thereto. The drive unit15sends the position information of the antenna11to the processing unit16. For example, the drive unit15is a motor or the like. The drive unit15may be electrically operated device or a manually operated device, and a drive type thereof is not limited. The drive unit15is an example of a drive section.

The processing unit16is electrically connected to the wireless tag communication unit12and the drive unit15. The processing unit16controls operations of the wireless tag reading apparatus1and processes various kinds of information. The processing unit16is an example of a processing section.

The processing unit16includes a CPU (Central Processing Unit)161, a ROM (Read Only Memory)162, a RAM (Random Access Memory)163and a storage device164.

The CPU161controls the operations of the wireless tag reading apparatus1and processes various kinds of information by executing programs stored in advance in the ROM162or the storage device164. The CPU161is an example of a processor. The CPU161is also an example of the processing section.

The CPU161executes the processing described below.

The CPU161outputs a movement instruction based on a predetermined movement path of the antenna11to the drive unit15to control the drive unit15. The CPU161changes the position of the antenna11by controlling the drive unit15. For example, the CPU161changes the position of the antenna11by repeatedly moving and stopping the antenna11.

The CPU161controls the wireless tag communication unit12to acquire the phase information and the information recorded in the RFID tag T from the wireless tag communication unit12. Here, for example, the CPU161radiates electromagnetic waves through the antenna11at the stop position of the antenna11. If the wireless tag communication unit12detects the phase of the response wave received by the antenna11, the CPU161acquires the phase information and the information recorded in the RFID tag T from the wireless tag communication unit12. The CPU161stores the phase information and the information recorded in the RFID tag T in the storage device164.

The CPU161specifies the position at which the antenna11receives the response wave. Here, for example, by acquiring the phase information from the wireless tag communication unit12, the CPU161determines that the antenna11receives the response wave. The CPU161acquires the position information of the antenna11from the drive unit15in response to the acquisition of the phase information. The CPU161acquires the position information of the antenna11from the drive unit15as information indicating the position at which the antenna11receives the response wave. The position at which the antenna11receives the response wave is also referred to as a reception position. The information indicating the reception position is also referred to as reception position information. The CPU161stores the reception position information in the storage device164in association with the phase information and the information recorded in the RFID tag T.

The CPU161determines whether or not the RFID tag T is in the predetermined area A by executing a position estimation processing for the RFID tag T described below. The CPU161determines whether the information recorded in the RFID tag T is required to be registered according to a determination result indicating whether or not the RFID tag T is in the predetermined area A. If the RFID tag T is in the predetermined area A, the CPU161registers the information recorded in the RFID tag T and read from the RFID tag T. On the other hand, if the RFID tag T is outside of the predetermined area A, the CPU161discards the information recorded in the RFID tag T and read from the RFID tag T.

The ROM162stores various programs and data.

The RAM163temporarily stores various programs, and stores data necessary for executing application programs, execution results, and the like.

The storage device164stores various programs and data. For example, the storage device164is an HDD (Hard Disk Drive), an SSD (Solid State Drive), or the like.

The storage device164stores the reception position information. The storage device164stores the phase information for each of the reception positions. The storage device164stores the information recorded in the RFID tag T for each of the reception positions. The phase information and the information recorded in the RFID tag T are associated with the reception position information.

Next, an example of changing the position of the antenna11by the CPU161is described.

FIG. 3is a diagram illustrating positions of the antenna11.

The CPU161moves the support member14through the drive unit15such that the antenna11moves in the range facing the predetermined area A in the vertical direction. Positions31to34indicate the reception positions. The positions31to34may also indicate positions within the predetermined area A facing the reception positions in the vertical direction. The positions31and32correspond to a first end of the predetermined area A in the horizontal direction. The first end includes an outer edge in the horizontal direction of the predetermined area A. The position31is closer to the outer edge of the predetermined area A in the horizontal direction than the position32.

The positions33and34correspond to a second end different from the first end in the horizontal direction of the predetermined area A. The second end includes an outer edge in the horizontal direction of the predetermined area A. For example, the second end includes an outer edge facing the outer edge included in the first end of the predetermined area A, and is arranged at a position facing the first end. The position34is closer to the outer edge of the predetermined area A in the horizontal direction than the position33.

The storage device164stores the reception position information, the phase information and the information recorded in the RFID tag T in an associated manner for each of the positions31to34. Here, for convenience of description, four reception positions aligned in one direction are shown, but the reception positions are not limited to those. The reception position may be a position other than the positions corresponding to the ends of the predetermined area A in the horizontal direction.

FIG. 4is a diagram illustrating a virtual antenna at the reception position.

The antenna11receives the response wave at the positions31to34shown inFIG. 4. Changing the position of the antenna11by the CPU161is equivalent to that the wireless tag reading apparatus1includes virtual antennas41to44at the positions31to34, respectively.

The CPU161assigns the phase information associated with each of the two or more reception positions to each of the plurality of groups. For example, the CPU161refers to the reception position information and the phase information associated with the reception position information stored in the storage device164. The CPU161sets the phase information associated with each of two or more adjacent reception positions as a group to form a plurality of groups.

In the example shown inFIG. 4, the CPU161assigns the phase information associated with the position31and the phase information associated with the position32to a first group51. In this way, the CPU161assigns the phase information associated with each of the two or more reception positions corresponding to the first end in the horizontal direction of the predetermined area A to the first group51. The CPU161may assign the phase information associated with each of any two or more reception positions other than the positions corresponding to the end to the first group51. The CPU161may assign the phase information associated with each of three or more reception positions to the first group51.

In the example shown inFIG. 4, the CPU161assigns the phase information associated with the position33and the phase information associated with the position34to a second group52. In this way, the CPU161assigns the phase information associated with each of two or more reception positions corresponding to the second end in the horizontal direction of the predetermined area A to the second group52. The CPU161may assign the phase information associated with each of any two or more reception positions other than the positions corresponding to the end to the second group52. The CPU161may assign the phase information associated with each of three or more reception positions to the second group52.

Next, an example of estimating an arrival direction of the response wave to each group by the CPU161is described.

The CPU161estimates the arrival direction of the response wave to each group based on the phase difference of the response wave among the plurality of virtual antennas as explained further below.

FIG. 5is a diagram illustrating the phase difference of the response wave in each group shown inFIG. 4.

The first group51is described next.

The phase information of the response wave received by the virtual antenna41at the position31and the phase information of the response wave received by the virtual antenna42at the position32are assigned to the first group51. The virtual antenna41is located at a position different from the virtual antenna42. The response wave arrives at the virtual antenna42first and then arrives at the virtual antenna41. Therefore, a difference occurs between the phase of the response wave received by the virtual antenna41and the phase of the response wave received by the virtual antenna42. The CPU161uses the phase of the response wave received by the virtual antenna42as a reference. The CPU161obtains the phase of the response wave received by the virtual antenna41as a phase delayed by φ1from the phase of the response wave received by the virtual antenna42.

φ1is a first phase difference of the response wave in the first group51. Here, if the phase of the response wave received by the virtual antenna41is delayed with respect to the phase of the response wave received by the virtual antenna42, the first phase difference φ1is a positive value. On the other hand, if the phase of the response wave received by the virtual antenna41is ahead of the phase of the response wave received by the virtual antenna42, the first phase difference φ1is a negative value.

The CPU161calculates the first phase difference φ1based on the phase information assigned to the first group51. The CPU161calculates the first phase difference φ1based on the phase information associated with the reception position of the virtual antenna41and the phase information associated with the reception position of the virtual antenna42.

The first phase difference φ1has the following relationship with an arrival angle θ1(may be referred to as an incident angle). The arrival angle θ1is an example of the arrival direction of the response wave.

Where, λ is a wavelength in the wireless system to be used, and d1is a distance from the position31of the virtual antenna41to the position32of the virtual antenna42.

The arrival angle θ1is an acute angle formed by the vertical direction and the arrival direction of the response wave in the first group51. The CPU161estimates a first slop of the arrival direction of the response wave with respect to the vertical direction based on the arrival angle θ1. The first slope is a slope of the arrival direction of the response wave with respect to the vertical direction in the first group51.

As described above, if the phase of the response wave received by the virtual antenna41is delayed with respect to the phase of the response wave received by the virtual antenna42, the first phase difference φ1 is a positive value. When the first phase difference φ1is a positive value, the arrival angle θ1is a positive value as can be calculated from Equation (1). When the arrival angle θ1is a positive value, the CPU161estimates the first slope as a slope towards the inside of the predetermined area A with respect to the vertical direction.

As described above, if the phase of the response wave received by the virtual antenna41is ahead of the phase of the response wave received by the virtual antenna42, the first phase difference φ1is a negative value. When the first phase difference φ1is a negative value, the arrival angle θ1is a negative value as can be calculated from Equation (1). When the arrival angle θ1is a negative value, the CPU161estimates the first slope as a slope towards the outside of the predetermined area A with respect to the vertical direction.

Thus, the CPU161estimates the first arrival direction of the response wave to the first group51based on the first phase difference φ1. Typically, the CPU161estimates the first arrival direction by calculating the arrival angle θ1using Equation (1).

The second group52is described.

The phase information of the response wave received by the virtual antenna43at the position33and the phase information of the response wave received by the virtual antenna44at the position34are assigned to the second group52. The virtual antenna43is located at a position different from the virtual antenna44. The response wave arrives at the virtual antenna43first and then arrives at the virtual antenna44. Therefore, a difference occurs between the phase of the response wave received by the virtual antenna43and the phase of the response wave received by the virtual antenna44. The CPU161uses the phase of the response wave received by the virtual antenna44as a reference. The CPU161obtains the phase of the response wave received by the virtual antenna43as a phase ahead of the phase of the response wave received by the virtual antenna44by φ2.

φ2is a second phase difference of the response wave in the second group52. Here, if the phase of the response wave received by the virtual antenna43is delayed with respect to the phase of the response wave received by the virtual antenna44, the second phase difference φ2is a positive value. On the other hand, if the phase of the response wave received by the virtual antenna43is ahead of the phase of the response wave received by the virtual antenna44, the second phase difference φ2is a negative value.

The CPU161calculates the second phase difference φ2based on the phase information assigned to the second group52. The CPU161calculates the second phase difference φ2based on the phase information associated with the reception position of the virtual antenna43and the phase information associated with the reception position of the virtual antenna44.

The second phase difference φ2has the following relationship with an arrival angle θ2(may be referred to as an incident angle). The arrival angle θ2is an example of the arrival direction of the response wave.

Where, λ is a wavelength in the wireless system, and d2is a distance from the position33of the virtual antenna43to the position34of the virtual antenna44.

The arrival angle θ2is an acute angle formed by the vertical direction and the arrival direction of the response wave in the second group52. The CPU161estimates a second slop of the arrival direction of the response wave with respect to the vertical direction based on the arrival angle θ2. The second slope is a slope of the arrival direction of the response wave with respect to the vertical direction in the second group52.

As described above, if the phase of the response wave received by the virtual antenna43is delayed with respect to the phase of the response wave received by the virtual antenna44, the second phase difference φ2is a positive value. When the second phase difference φ2is a positive value, the arrival angle θ2is a positive value as can be calculated from Equation (2). When the arrival angle θ2is a positive value, the CPU161estimates the second slope as a slope towards the outside of the predetermined area A with respect to the vertical direction.

As described above, if the phase of the response wave received by the virtual antenna43is ahead of the phase of the response wave received by the virtual antenna44, the second phase difference φ2is a negative value. When the second phase difference φ2is a negative value, the arrival angle θ2is a negative value as can be calculated from Equation (2). When the arrival angle θ2is a negative value, the CPU161estimates the second slope as a slope towards the inside of the predetermined area A with respect to the vertical direction.

Thus, the CPU161estimates the second arrival direction of the response wave to the second group52based on the second phase difference φ2. Typically, the CPU161estimates the second arrival direction by calculating the arrival angle θ2using Equation (2).

Next, an example of determining whether or not the RFID tag T is in the predetermined area A by the CPU161is described.

The CPU161determines whether or not the RFID tag T is in the predetermined area A based on the first arrival direction and the second arrival direction, as explained further below.

First, a first position estimation processing by the CPU161is described.

FIG. 6is a diagram illustrating position estimation for the RFID tag T according to the first position estimation processing.

The CPU161extracts estimation results in any two groups from estimation results relating to the arrival direction of the response wave in a plurality of groups. Here, it is assumed that the CPU161extracts the estimation result relating to the first arrival direction in the first group51corresponding to the above-described first end. The estimation result relating to the first arrival direction contains information relating to the arrival angle θ1. Similarly, it is assumed that the CPU161extracts the estimation result relating to the second arrival direction in the second group52corresponding to the above-described second end. The estimation result relating to the second arrival direction contains information relating to the arrival angle θ2.FIG. 6shows an example in which the arrival angle θ1is a positive value and the arrival angle θ2is a negative value.

The value H is a distance from the upper surface21of the table2to the RFID tag T in the vertical direction. D is a distance from the first group51to the second group52in the horizontal direction. D may be the shortest distance between a virtual antenna involved in the first group51and a virtual antenna involved in the second group52. D may be a distance from the virtual antenna42involved in the first group51to the virtual antenna44involved in the second group52.

The value of H can be expressed as follows using D, the arrival angle θ1and the arrival angle θ2.

Where, X1is a distance from a position where the first group51is projected on the upper surface21in the vertical direction to a position where the RFID tag T is projected on the upper surface. For example, X1may be a distance from a position where the virtual antenna42involved in the first group51is projected on the upper surface21to a position where the RFID tag T is projected on the upper surface21.

X1can be expressed as follows using H and the arrival angle θ1.
X1=Htan θ1Equation (4)

In this context, X2is a distance from a position where the second group52is projected on the upper surface21in to a position where the RFID tag T is projected on the upper surface21. For example, X2may be a distance from a position where the virtual antenna44involved in the second group52is projected on the upper surface21to a position where the RFID tag T is projected on the upper surface21.

The value of X2can be expressed as follows using H and the arrival angle θ2.
X2=−Htan θ2Equation (5)

The CPU161estimates the position of the RFID tag T in the vertical direction based on the first arrival direction and the second arrival direction. Here, the CPU161estimates the position of the RFID tag T in the vertical direction by calculating H using Equation (3).

The CPU161determines whether or not the RFID tag T is in the predetermined area A based on the position of the RFID tag T in the vertical direction. Here, the CPU161determines whether or not H is less than a threshold value in the vertical direction. The threshold value in the vertical direction is a distance from the upper surface21to a boundary of the predetermined area A in the vertical direction. If H is less than the threshold value in the vertical direction, the CPU161determines that the RFID tag T is in the predetermined area A along the vertical direction. If H is equal to or larger than the threshold value in the vertical direction, the CPU161determines that the RFID tag T is outside of the predetermined area A in the vertical direction.

Thus, the CPU161can estimate the position of the RFID tag T in the vertical direction according to the first position estimation processing. The CPU161can determine whether or not the RFID tag T is in the predetermined area A along the vertical direction.

The CPU161estimates the position of the RFID tag T in the horizontal direction based on the first arrival direction and the second arrival direction. Here, the CPU161estimates the position of the RFID tag T in the horizontal direction by calculating X1and X2using Equation (4) and Equation (5).

The CPU161determines whether or not the RFID tag T is in the predetermined area A based on the position of the RFID tag T in the horizontal direction. Here, for example, the CPU161determines whether or not the sum of X1and X2is less than the threshold value in the horizontal direction. The threshold value in the horizontal direction is a distance between the opposite boundaries of the predetermined area A in the horizontal direction. If the sum of X1and X2is less than the threshold value in the horizontal direction, the CPU161determines that the RFID tag T is in the predetermined area A in the horizontal direction. If the sum of X1and X2is equal to or larger than the threshold value in the horizontal direction, the CPU161determines that the RFID tag T is outside of the predetermined area A in the horizontal direction.

Thus, the CPU161can estimate the position of the RFID tag T in the horizontal direction according to the first position estimation processing. The CPU161can determine whether or not the RFID tag T is in the predetermined area A in an estimated direction.

Next, a second position estimation processing by the CPU161is described.

FIG. 7is a diagram illustrating an example of position estimation for the RFID tag T according to the second position estimation processing.

The CPU161extracts the estimation result relating to the first arrival direction in the first group51corresponding to the first end described above from the estimation results relating to the arrival direction of the response wave in the plurality of groups. The estimation result relating to the first arrival direction includes information relating to the arrival angle θ1and the first slope. Similarly, the CPU161extracts the estimation result relating to the second arrival direction in the second group52corresponding to the second end described above. The estimation result relating to the second arrival direction includes information relating to the arrival angle θ2and the second slope.

The CPU161determines whether or not the RFID tag T is in the predetermined area A based on the first slope and the second slope. For example, the CPU161determines whether or not the RFID tag T is in the predetermined area A based on the combination of signs of the arrival angle θ1and the arrival angle θ2. The combination of the signs of the arrival angle θ1and the arrival angle θ2corresponds to a combination of whether the first slope is the slope towards the inside of the predetermined area A and whether the second slope is the slope towards the inside of the predetermined area A.

If the arrival angle θ1and the arrival angle θ2have different signs, the CPU161determines that the RFID tag T is in the predetermined area A along the horizontal direction. If the arrival angle θ1and the arrival angle θ2have different signs, the first slope is the slope towards the inside of the predetermined area A, and the second slope is the slope towards the inside of the predetermined area A.

If the arrival angle θ1and the arrival angle θ2have the same sign, the CPU161determines that the RFID tag T is outside of the predetermined area A in the horizontal direction. If the arrival angle θ1and the arrival angle θ2have the same sign, the first slope is the slope towards the outside of the predetermined area A and the second slope is the slope towards the inside of the predetermined area A. Or, if the arrival angle θ1and the arrival angle θ2have the same sign, the first slope is the slope towards the inside of the predetermined area A, and the second slope is the slope towards the outside of the predetermined area A.

Thus, the CPU161can estimate the position of the RFID tag T in the horizontal direction according to the second position estimation processing. The CPU161can determine whether or not the RFID tag T is in the predetermined area A along the horizontal direction.

A processing of reading the RFID tag T by the CPU161is described.

FIG. 8is a flowchart depicting an example of the processing of reading the RFID tag T using the first position estimation processing by the CPU161.

The CPU161determines whether to start reading the RFID tag T (Act101). If the CPU161determines not to start reading the RFID tag T (No in Act101), the CPU161stands by until an instruction to start reading the RFID tag T is input.

If the CPU161determines to start reading the RFID tag T (Yes in Act101), the CPU161controls each section to start reading the RFID tag T.

The CPU161acquires the phase information from the wireless tag communication unit12(Act102). In Act102, the CPU161stores the phase information and the information recorded in the RFID tag T in the storage device164.

The CPU161acquires the reception position information from the drive unit15(Act103). In Act103, the CPU161stores the reception position information in the storage device164in association with the phase information and the information recorded in the RFID tag T.

The CPU161outputs a movement instruction to the drive unit15to move the position of the antenna11(Act104). The CPU161determines whether or not the movement of the position of the antenna11is terminated (Act105). If it is determined that the movement of the position of the antenna11is not terminated (No in Act105), the CPU161executes the processing in Act102again.

If it is determined that the movement of the position of the antenna11is terminated (Yes in Act105), the phase information is assigned to each of the plurality of groups (Act106).

The CPU161calculates the phase difference in each group based on the phase information assigned to each group (Act107). In Act107, for example, the CPU161calculates the first phase difference φ1in the first group51. The CPU161calculates the second phase difference φ2in the second group52.

The CPU161estimates the arrival direction of the response wave to each group based on the phase difference in each group (Act108). In Act108, for example, the CPU161estimates the first arrival direction of the response wave to the first group51based on the first phase difference φ1. The CPU161estimates the second arrival direction of the response wave to the second group52based on the second phase difference φ2.

The CPU161estimates the position of the RFID tag T according to the above-mentioned first position estimation processing based on the arrival direction of the response wave to the two or more groups (Act109). In Act109, for example, the CPU161estimates the position of the RFID tag T in the vertical direction according to the above-described first position estimation processing. In place of or in addition to that, the CPU161estimates the position of the RFID tag T in the horizontal direction according to the above-described first position estimation processing.

The CPU161determines whether or not a parameter relating to the position of the RFID tag T, such as H or the sum of X1and X2, is less than a threshold value (Act110). In Act110, for example, the CPU161compares H associated with the position of the RFID tag T in the vertical direction with the threshold value in the vertical direction. In place of or in addition to that, the CPU161compares the sum of X1and X2associated with the position of the RFID tag T in the horizontal direction with the threshold value in the horizontal direction.

If the parameter relating to the position of the RFID tag T is less than the threshold value (Yes in Act110), the CPU161determines that the RFID tag T is in the predetermined area A (Act111). In Act111, for example, if H is less than the threshold value in the vertical direction, the CPU161determines that the RFID tag T is in the predetermined area A along the vertical direction. If the sum of X1and X2is less than the threshold value in the horizontal direction, the CPU161determines that the RFID tag T is in the predetermined area A along the horizontal direction. If H is less than the threshold value in the vertical direction and the sum of X1and X2is less than the threshold value in the horizontal direction, the CPU161determines that the RFID tag T is in the predetermined area A.

The CPU161determines whether to terminate the reading of the RFID tag T (Act112). If the CPU161determines to terminate the reading of the RFID tag T (Yes in Act112), the CPU161terminates the reading processing. If the CPU161determines not to terminate the reading of the RFID tag T (No in Act112), the CPU161executes the processing in Act102again.

If the parameter relating to the position of the RFID tag T is not less than the threshold value (No in Act110), the CPU161executes the processing in Act112. For example, if H is equal to or larger than the threshold value in the vertical direction, the CPU161determines that the RFID tag T is outside of the predetermined area A in the vertical direction. If the sum of X1and X2is equal to or larger than the threshold value in the horizontal direction, the CPU161determines that the RFID tag T is outside of the predetermined area A in the horizontal direction.

FIG. 9is a flowchart depicting a processing of reading the RFID tag T using the second position estimation processing by the CPU161.

Since Act201to Act208, Act210, and Act211are the same as Act101to Act108, Act111, and Act112described above, the description thereof is omitted.

The processing in Act209is described.

The CPU161determines whether or not the arrival angles to respective group have different signs (Act209). In Act209, for example, the CPU161determines whether or not the arrival angle θ1and the arrival angle θ2have different signs.

If the arrival angle θ1and the arrival angle θ2have different signs (Yes in Act209), the CPU161determines that the RFID tag T is in the predetermined area A along the horizontal direction (Act210). If the arrival angle θ1and the arrival angle θ2have the same sign (No in Act209), the CPU161executes the processing in Act211. If the arrival angle θ1and the arrival angle θ2have the same sign, the CPU161determines that the RFID tag T is outside of the predetermined area A in the horizontal direction.

According to an embodiment, the wireless tag reading apparatus1determines whether or not the RFID tag T is in the predetermined area A based on the first arrival direction and the second arrival direction of the response wave.

The wireless tag reading apparatus1radiates electromagnetic waves through the antenna11to communicate with the RFID tag T. The wireless tag reading apparatus1sets the power to be supplied from the wireless tag communication unit12to the antenna11as strongly as possible to minimize the number of RFID tags T to be missed. This is because it is unclear where the RFID tag T that the wireless tag reading apparatus1intends to read is positioned. Therefore, even when the wireless tag reading apparatus1can communicate with a tag that is not required to be registered, the wireless tag reading apparatus1reads the information of the tag that is not required to be registered.

Whether the RFID tag T is in the predetermined area A can be determined by the wireless tag reading apparatus1based on the first arrival direction and the second arrival direction of the response wave, without using a dedicated container. Therefore, the wireless tag reading apparatus1can determine whether or not the read information is the information of a desired tag required to be registered depending on whether the RFID tag T is in the predetermined area A.

According to the embodiment, the wireless tag reading apparatus1can estimate the position of the RFID tag T in the vertical direction based on the first arrival direction and the second arrival direction. The wireless tag reading apparatus1can determine whether or not the RFID tag T is in the predetermined area A based on the position of the RFID tag T in the vertical direction.

In this way, the wireless tag reading apparatus1can determine whether or not the RFID tag T is in the predetermined area A in the vertical direction without using a dedicated container.

According to the embodiment, the wireless tag reading apparatus1can estimate the position of the RFID tag T in the horizontal direction based on the first arrival direction and the second arrival direction. The wireless tag reading apparatus1can determine whether or not the RFID tag T is in the predetermined area A based on the position of the RFID tag T in the horizontal direction.

In this way, the wireless tag reading apparatus1can determine whether or not the RFID tag T is in the predetermined area A along the horizontal direction without using a dedicated container.

According to the embodiment, the wireless tag reading apparatus1can determine whether or not the RFID tag T is in the predetermined area A based on the first slope and the second slope.

In this way, the wireless tag reading apparatus1can determine whether or not the RFID tag T is in the predetermined area A in the horizontal direction without using a dedicated container.

According to the embodiment, the wireless tag reading apparatus1can determine whether or not the RFID tag T is in the predetermined area A based on the combination of the first slope and the second slope.

In this way, the wireless tag reading apparatus1can more accurately determine whether or not the RFID tag T is in the predetermined area A along the horizontal direction without using a dedicated container or electromagnetic shielding around the predetermined area A.