JP2011237941A - Wireless tag communication device and wireless tag searching method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency of article recognition work by promptly detecting a wireless tag having particular ID information from among plural wireless tags.SOLUTION: A wireless tag reading device 1 comprises a receiving unit 13B, a storing unit 12, a reception state detecting unit 151, and a reception state notification unit 155. The receiving unit 13B receives a radio wave of a wireless tag via an antenna 4 having maximal directivity in a particular direction. The storage unit 12 stores information on a target wireless tag specified as a reading target. The reception state detecting unit 151 detects a radio wave reception state of the target wireless tag at the receiving unit 13B. The reception state notification unit 155 notifies a detection result of the radio wave reception state.

Description

  Embodiments described herein relate generally to a wireless tag communication device having a function of searching for a wireless tag having specific information from a plurality of wireless tags, and a wireless tag searching method using this device.

  In recent years, an automatic recognition system that recognizes an article by attaching a wireless tag including an IC chip and an antenna to the article has attracted attention. The wireless tag stores unique ID information in a memory in the IC chip. The automatic recognition system recognizes a wireless tag, and thus an article to which the tag is attached, by reading ID information from the wireless tag in a non-contact manner using a wireless tag communication device.

  The wireless tag communication device includes an antenna, and collectively reads ID information of a plurality of wireless tags existing in a communication area of radio waves radiated from the antenna. In such a wireless tag communication device, a portable device having a function of searching for a wireless tag having specific ID information from a plurality of wireless tags is already known.

JP 2009-98951 A

  However, a conventional RFID tag communication apparatus having a RFID tag search function reads not only a RFID tag having specific ID information but also ID information of all RFID tags in the communication area. For this reason, it takes time to detect a wireless tag having specific ID information, and the efficiency of the article recognition work is poor.

  Therefore, there is a demand for a wireless tag communication device that can quickly detect a wireless tag having specific ID information from a plurality of wireless tags and can improve the efficiency of the article recognition work.

  According to one embodiment, the wireless tag reader includes a receiving unit, a storage unit, a reception state detection unit, and a reception state notification unit. The receiving unit receives radio waves from the wireless tag via an antenna having maximum directivity in a specific direction. The storage unit stores information related to the target wireless tag designated as the reading target. The reception state detection unit detects the radio wave reception state of the target wireless tag at the reception unit. The reception state notification unit notifies the detection result of the radio wave reception state.

1 is an external view of a wireless tag communication device according to an embodiment. The schematic diagram of the antenna connected to the radio | wireless tag communication apparatus. The block diagram which shows the principal part structure of the radio | wireless tag communication apparatus. The block diagram which shows the structure of the radio | wireless part mounted in the radio | wireless tag communication apparatus. The flowchart which shows the process sequence which the control part of a wireless tag communication apparatus performs in 1st Embodiment. 4 is a timing chart illustrating an example of a communication protocol between a wireless tag communication device and a wireless tag. The timing chart which shows the other example of the communication protocol of a wireless tag communication apparatus and a wireless tag. Explanatory drawing of the method of searching for a desired wireless tag using a wireless tag communication apparatus. The flowchart which shows the process sequence which the control part of a wireless tag communication apparatus performs in 2nd Embodiment. The flowchart which shows the process sequence which the control part of a wireless tag communication apparatus performs in 3rd Embodiment. The block diagram which shows the principal part structure of the wireless tag communication apparatus in 4th Embodiment. The flowchart which shows the process sequence which the control part of a wireless tag communication apparatus performs in 4th Embodiment. The flowchart which shows the process sequence which the control part of a wireless tag communication apparatus performs in 5th Embodiment. 9 is a flowchart showing a processing procedure executed by a control unit of a wireless tag communication device in a sixth embodiment.

Hereinafter, embodiments of a wireless tag communication device and a wireless tag searching method using the device will be described with reference to the drawings.
This embodiment is a case where the present invention is applied to a portable wireless tag communication device for searching for a desired wireless tag from a passive wireless tag group having no battery.

(First embodiment)
FIG. 1 is an external view of the wireless tag communication device 1. In the device 1, a display 2 as a display unit and a keyboard 3 as an input unit are arranged on the front of a portable housing 1A. Further, in this device 1, a planar patch antenna 4 is connected to a housing 1A with an antenna cable 5.

  The antenna 4 has a grip 4B attached to a plate-shaped antenna unit 4A. The operator searches for the wireless tag by holding the grip 4B and directing the antenna surface 4C of the antenna unit 4A in an arbitrary direction.

  As shown in FIG. 2, the antenna unit 4A has a plate-like dielectric 6 fixed therein, a radiator 7 is attached to the antenna surface side of the dielectric 6, and a ground plate 8 is placed on the opposite back side. Is installed. And it has directivity with the maximum gain in the substantially vertical direction from the center of the antenna surface 4C.

  FIG. 3 is a block diagram showing a main configuration of the wireless tag communication device 1. The wireless tag communication device 1 includes a power supply unit 11, a storage unit 12, a wireless unit 13, a communication interface 14, and a control unit 15. The power supply unit 11 includes a battery and a control circuit for charging and discharging the battery.

  The storage unit 12 has a ROM (Read Only Memory) area and a RAM (Random Access Memory) area. In the ROM area, programs and setting data used by the control unit 15 are stored in advance. In the RAM area, variable data is temporarily written by the action of the control unit 15.

  The communication interface 14 manages data communication with a host device connected via a communication line. The communication line may be wired or wireless.

  A control unit 15 mainly composed of a CPU (Central Processing Unit) controls the display 2, the keyboard 3, the storage unit 12, the wireless unit 13 and the communication interface 14 to control the entire RFID tag communication apparatus 1. In particular, the control unit 15 includes a reception state detection unit 151, a transmission output control unit 152, a switching determination unit 153, an instruction reception unit 154, and a reception state notification unit 155 in order to realize a wireless tag search function. Details of the components 151 to 155 will be described later.

  FIG. 4 is a block diagram illustrating a specific configuration of the wireless unit 13. The wireless unit 13 includes a transmitting unit 13A for transmitting data to the wireless tag, a receiving unit 13B for receiving data of the wireless tag, and a directional coupler 13C including a circulator or the like. The antenna 4 is connected to the directional coupler 13C via a low-pass filter 13D.

  The transmission unit 13A includes an encoding unit 21, a PLL (phase locked loop) unit 22, an amplitude modulator 23, a bandpass filter 24, and a power amplifier 25.

  The encoding unit 21 encodes the transmission signal output from the control unit 15. The PLL unit 22 supplies a local carrier signal to the amplitude modulator 23. The amplitude modulator 23 amplitude-modulates the local carrier signal from the PLL unit 22 with the transmission signal encoded by the encoding unit 2. The bandpass filter 24 removes unnecessary components from the transmission signal amplitude-modulated by the amplitude modulator 23. The power amplifier 25 amplifies the transmission signal that has passed through the bandpass filter 24 with an amplification factor according to the transmission output setting signal S from the control unit 15. The transmission output P is varied by amplifying the transmission signal. The transmission signal amplified by the power amplifier 25 is supplied to the directional coupler 13C.

  The directional coupler 13C supplies the transmission signal from the transmission unit 13A to the antenna 4 via the low-pass filter 13D. The transmission signal supplied to the antenna 4 is radiated as a radio wave from the antenna 4.

  The passive wireless tag that receives this radio wave is activated. The activated wireless tag wirelessly transmits information stored in the memory of the IC chip to the wireless tag communication device 1 by performing backscatter modulation on the unmodulated signal. Radio waves from the radio tag are received by the antenna 4.

  When the antenna 4 receives the radio wave from the radio tag, the received signal is supplied from the antenna 4 to the directional coupler 13C via the low pass filter 13D. The directional coupler 13C supplies the reception signal of the antenna 4, that is, the signal from the wireless tag to the reception unit 13B.

  The reception unit 13B includes an I signal generation unit 31, a Q signal generation unit 32, an I signal processing unit 33, a Q signal processing unit 34, and a reception signal level detection unit 35.

  The I signal generation unit 31 includes a mixer 41, a low pass filter 42, and a binarization circuit 43. The Q signal generation unit 32 includes a mixer 51, a low-pass filter 52, a binarization circuit 53, and a 90-degree phase shifter 54.

  The receiving unit 13B inputs the received signal from the directional coupler 30 to the first mixer 41 and the second mixer 51, respectively. Further, the receiving unit 13B inputs the local carrier signal from the PLL unit 22 to the first mixer 41 and the 90-degree phase shifter 54. The 90-degree phase shifter 54 shifts the phase of the local carrier signal by 90 degrees and supplies it to the second mixer 51.

  The first mixer 41 mixes the received signal and the local carrier signal, and generates an I signal having a component in phase with the local carrier signal. The I signal is supplied to the binarization circuit 43 through the low pass filter 42. The low-pass filter 42 removes an unnecessary high-frequency component from the I signal and extracts an encoded data component. The binarization circuit 43 binarizes the signal that has passed through the low-pass filter 42.

  The second mixer 51 mixes the received signal and the local carrier signal whose phase is shifted by 90 degrees to generate a Q signal that is orthogonal to the local carrier signal. The Q signal is supplied to the binarization circuit 53 via the low pass filter 52. The low-pass filter 52 removes an unnecessary high-frequency component from the Q signal and extracts an encoded data component. The binarization circuit 53 binarizes the signal that has passed through the low-pass filter 52.

  The I signal processing unit 33 includes an I signal synchronous clock generation unit 61, an I signal preamble detection unit 62, an I signal decoding unit 63, and an I signal error detection unit 64. The Q signal processing unit 34 includes a Q signal synchronous clock generation unit 71, a Q signal preamble detection unit 72, a Q signal decoding unit 73, and a Q signal error detection unit 74.

  The reception unit 13B supplies the I signal binarized by the binarization circuit 43 of the I signal generation unit 31 to each unit 61 to 64 of the I signal processing unit 33. In addition, the Q signal binarized by the binarization circuit 53 of the Q signal generation unit 32 is supplied to each unit 71 to 74 of the Q signal processing unit 34. Here, the operations of the I signal processing unit 33 and the Q signal processing unit 34 are common. Therefore, the I signal processing unit 33 will be described below, and the description of the Q signal processing unit 34 will be omitted.

  The synchronous clock generation unit 61 always generates a clock signal synchronized with the binarized signal from the binarization circuit 43, and generates the generated clock signal as a control unit 15, a preamble detection unit 62, a decoding unit 63, and an error detection unit. 64.

  The preamble detector 62 detects the preamble added to the head of the I signal based on the clock signal from the synchronous clock generator 61. When the preamble is detected, the preamble detection unit 62 outputs a detection signal to the control unit 15. When receiving the preamble detection signal, the control unit 15 supplies a decoding start command signal to the decoding unit 63.

  The decoding unit 63 samples the binarized signal from the binarization circuit 43 in synchronization with the clock signal from the synchronous clock generation unit 61. When the decoding start command is received from the control unit 15, the sampled binary signal is decoded. The decrypted data is supplied to the control unit 15.

  The control unit 15 supplies the decoded data to the error detection unit 64. The error detection unit 64 detects the presence or absence of an error from the check code of the decoded data. Then, data indicating the detection result is supplied to the control unit 15. The control unit 15 is configured to determine that data has been correctly received when there is no error in at least one of the I signal and the Q signal.

  The reception signal level detection unit 35 detects the amplitude of the I signal that has passed through the low-pass filter 42 and the amplitude of the Q signal that has passed through the low-pass filter 52. Then, the control unit 15 is notified of the larger amplitude value as the received signal level.

  FIG. 5 is a flowchart showing a processing procedure of the control unit 15 for realizing the RFID tag search function of the RFID tag communication apparatus 1. This procedure is controlled by a wireless tag search program stored in the storage unit 12.

  For example, when a search start key on the keyboard 3 is operated, the RFID tag search program is activated. First, the control unit 15 waits for input of ID information of a wireless tag designated as a reading target (ST1). The ID information input at this time may be all or a part of the ID.

  When the ID information is input via the keyboard 3 (YES in ST1), the control unit 15 stores the ID information in the storage unit 12 as designation information of the reading target tag (ST2).

  Next, the control unit 15 outputs a control signal S for setting the transmission output P of the transmission unit 13A to the maximum value Pmax to the power amplifier 25 (ST3). Then, wireless communication with the wireless tag is started with this transmission output P, and a tag to be read is searched (ST4).

  6 and 7 are timing charts showing an example of a wireless communication protocol between the wireless tag communication device 1 and the two wireless tags T1 and T2. This example conforms to the ISO18000-6typeC protocol. In this case, the number of slots per round is “2”.

  6 and 7, the symbols [S], [Q], [R], [A], [ID], and [Qr] all indicate communication data. Each communication data includes an error detection code such as a CRC (Cyclic Redundancy Check) code, and an error can be detected on the receiving side. On the receiving side, the symbol “◯” means successful reception. The symbol “x” means reception failure.

  One wireless tag T1 is a reading target tag, and the other wireless tag T2 is a non-reading target tag. First, the wireless tag communication device 1 wirelessly transmits an unmodulated carrier signal as a radio wave from the antenna 4. Each of the wireless tags T1 and T2 receives this radio wave and is activated.

  Next, the wireless tag communication device 1 wirelessly transmits a SELECT command [S] for instructing a tag to be read. The SELECT command [S] includes ID information of the wireless tag T1 designated as the tag to be read.

  Upon receiving the SELECT command [S], each of the wireless tags T1 and T2 confirms whether or not its own ID information is included in the command [S]. If included, the wireless tag recognizes that the wireless tag communication device 1 has designated itself. If not included, the wireless tag recognizes that it is not specified. In this example, the wireless tag T1 recognizes that it has been designated.

  Next, the wireless tag communication device 1 transmits a Query command [Q] for instructing the start of reading in the first round. The Query command [Q] includes a parameter (Q value = 1) that sets the number of slots per round to “2”. When the wireless tag T1 other than the wireless tag T2 that recognizes that it is not designated receives the Query command [Q], it generates a random number. Based on this random number, the wireless tag T1 determines which slot of the two slots in one round responds. Similarly, the wireless tag T1 generates response data [R] using random numbers. Since the response data [R] is generated by a random number, the response data [R] has a different value for each wireless tag.

  In the example of FIG. 6, the wireless tag T1 transmits response data [R] in the first slot. The wireless tag T2 that recognizes that it is not designated does not perform communication even when it receives the Query command [Q].

  When the response data [R] from the wireless tag T1 is received, the wireless tag communication device 1 transmits an Ack command [A] instructing that the response data [R] is normally received. The Ack command [A] includes the response data [R] received from the wireless tag T1.

  The wireless tag T1 that has transmitted the response data [R] waits for an Ack command [A]. When the Ack command [A] is received, it is confirmed whether or not the response data [R] transmitted by itself is included. When the response data [R] is included, it is recognized that the Ack command [A] is addressed to itself.

  If the Ack command [A] addressed to itself is received, the wireless tag T1 transmits the ID information [ID] stored in its own memory.

  When receiving the ID information [ID] from the wireless tag T1, the wireless tag communication device 1 determines whether or not the ID information [ID] matches the ID information stored as the designation information of the tag to be read. If they match, the reception count N is counted. The reception count N is reset to “0” in the initial state before the start of communication.

  Next, the wireless tag communication device 1 transmits a Query-rep command [Qr] for instructing slot switching. However, the wireless tag T1 that has already transmitted the response data [R] does not respond even if it receives the Query-rep command [Qr]. The same applies to the wireless tag T2 that is not designated by itself.

  When a predetermined time t1 has elapsed from the start of transmission of the previous SELECT command [S], the RFID tag communication apparatus 1 transmits the SELECT command [S] again, and subsequently, the second round Query command [Q] and Query- A rep command [Qr] is transmitted. The operations of the wireless tags T1 and T2 in this case are the same as in the first round.

  In the example of FIG. 6, the wireless tag T1 designated as the reading target transmits response data [R] and ID information [ID] in the second slot.

  After that, every time the predetermined time t1 elapses, the RFID tag communication apparatus 1 transmits the SELECT command [S], the Query command [Q], and the Query-rep command [Qr], and the RFID tag T1. ID information [ID] is received. Each time the ID information [ID] is received, the number N of receptions is counted.

  By the way, the example of FIG. 7 is a case where the RFID tag T2 that is not designated as the reading target receives the radio wave of the RFID tag communication apparatus 1 after the end of the second round SELECT command [S]. In this case, since the Query command [Q] is received without receiving the SELECT command [S], the wireless tag T2 responds to the Query command [Q]. And own ID information [ID] is transmitted.

  However, the ID information [ID] from the wireless tag T2 does not match the ID information stored as the designation information of the reading target tag. For this reason, the wireless tag communication device 1 does not count the number of receptions N. When the wireless tag communication device 1 receives the ID information [ID] from the wireless tag T1 in the second slot of the second round, the wireless tag communication device 1 counts the number of receptions N.

Returning to FIG.
The control unit 15 that has started the search for the reading target tag counts the number of times of reception N every time the ID information stored in the storage unit 12 as the reading target tag designation information is received from the wireless tag (ST5: reception state detection unit) 151). And it is judged whether the frequency | count N of reception exceeded the 1st threshold value L1 (ST6). The first threshold value L1 is set to a value that can determine that the wireless communication state with the reading target tag is good, for example, “10”.

  When the number N of receptions does not exceed the first threshold L1 (NO in ST6), the control unit 15 continues the wireless communication protocol.

  If the number N of receptions exceeds the first threshold value L1 (YES in ST6), the control unit 15 causes the display 2 to display a message indicating that the wireless communication state with the reading target tag is good (ST7). : Reception state notification unit 155).

  Next, control unit 15 determines whether or not a change in transmission output has been instructed (ST8: switching determination unit 153). The transmission output change instruction is performed, for example, by operating an output change key of the keyboard 3. That is, the control unit 15 receives an input of an output change key (instruction receiving unit 154). When the output change key is not input (NO in ST8), the control unit 15 continues the wireless communication protocol.

  When the output change key is input (YES in ST8), control unit 15 causes display 2 to display a message indicating that the transmission output decreases (ST9). Further, the control signal S for switching the transmission output P of the transmission unit 13A to the transmission output [P-1] one step lower than the current step is output to the power amplifier 25 (ST10: transmission output control unit 152). Then, with this transmission output [P-1], wireless communication with the wireless tag is resumed to search for a tag to be read (ST11).

  At this time, the control unit 15 once initializes the reception count N to “0”. Then, every time the ID information stored as the designation information of the reading target tag is received, the number N of times of reception is counted (ST12: reception state detection unit 151). And it is judged whether the frequency | count N of reception is less than the 2nd threshold value L2 (ST13). The second threshold value L2 is set to a value sufficiently smaller than the first threshold value L1, for example, “2”. If the number of receptions is less than this value L2, the wireless communication state with the tag to be read is poor.

  When the number of receptions N is equal to or greater than the second second threshold L2 (NO in ST13), the control unit 15 performs control for switching the transmission output P to a transmission output [P-2] that is one step lower. The signal S is output to the power amplifier 25 (ST10: transmission output control unit 152). Then, wireless communication with the wireless tag is resumed with this transmission output [P-2], and a tag to be read is searched (ST11).

  Also at this time, the control unit 15 once initializes the number of receptions N to “0”. Then, every time the ID information stored as the designation information of the reading target tag is received, the number N of times of reception is counted (ST12: reception state detection unit 151).

  Even when the number of rounds set in advance from the restart of transmission, for example, at the stage when the communication of the tenth round is finished, if the number of receptions N is below the second second threshold L2 (YES in ST13), the control unit 15 A message notifying the end of transmission output change is displayed on the display 2 (ST14). Further, a message for instructing the operator to move the search position so as to approach the wireless tag side is also displayed (ST15).

  Thereafter, the control unit 15 determines whether or not the search end is instructed (ST16). The search end instruction is given by, for example, operating the end key of the keyboard 3. That is, the control unit 15 receives an input of an end key. When the end key is not input (NO in ST16), the control unit 15 returns to the process in step ST4. That is, the search at the current transmission output P is resumed. Thereafter, the processes of steps ST4 to ST16 are repeated. When the end key is input (YES in ST16), the wireless tag search program ends.

Next, a specific example of searching for a wireless tag T1 to be read from a plurality of wireless tags using the wireless tag communication device 1 of the present embodiment will be described.
FIG. 8 is a schematic diagram used for explaining the specific example. As shown in FIG. 8, there is only one read target tag T1 in the approximate center of many non-read target tags T2. The operator searches from the front side (the lower side of the page) holding the antenna 4.

  First, the worker stands at a position K1 farthest from the location of the wireless tags T1 and T2. Then, after inputting the ID information of the reading target tag T1, the search start key is operated to direct the antenna surface 4C of the antenna 4 forward. Then, the radio wave having the maximum transmission output Pmax is transmitted from the antenna 4.

  The radio wave communication area at this time is indicated by reference numeral P1 in FIG. The read target tag T1 exists in the communication area P1. Therefore, the number N of receptions exceeds the first threshold value L1 in a relatively short time.

  When the number N of receptions exceeds the first threshold value L1, a message indicating that the wireless communication state with the reading target tag T1 is good is displayed on the display 2. Therefore, the operator recognizes that the reading target tag T1 exists in the direction in which the antenna surface 4C faces.

  Upon confirming this message, the operator operates the output change key. If it does so, the transmission output of an electromagnetic wave will be reduced in steps. At this time, a message indicating that the transmission output is reduced is displayed on the display 2. Therefore, the worker knows that the transmission output is decreasing.

  When the radio wave transmission output decreases to the communication area indicated by the symbol P2, the communication with the reading target tag T1 becomes unstable. Then, the number N of receptions within a predetermined time is less than the second threshold value L2. When the number of receptions N is less than the second threshold value L2, a message notifying the end of changing the transmission output is displayed on the display 2. A message instructing to move closer to the wireless tag side is also displayed.

  Therefore, the worker moves while holding the antenna 4 in the direction in which the antenna surface 4C faces, that is, the direction in which the reading target tag T1 is supposed to be present. At this time, since the transmission output of the radio wave does not change, the size of the communication area P2 does not change. Therefore, when the worker moves from position K1 to position K2, a message indicating that the number of receptions N exceeds the first threshold value L1 and the wireless communication state with the reading target tag T1 is good is displayed on the display 2. Is done.

  From this message, the operator recognizes that the reading target tag T1 is moving in the direction in which it exists. Therefore, the worker stays at the position K2 and operates the output change key again. Then, the radio wave transmission output is further reduced in stages. Then, when the radio wave transmission output is reduced to the communication area indicated by the symbol P3, the number N of receptions within a predetermined time becomes smaller than the second threshold value L2. When the number of receptions N is less than the second threshold value L2, a message notifying the end of transmission output change and a message instructing to move closer to the wireless tag side are displayed on the display 2.

  When these messages are confirmed, the worker further moves in the same direction while holding the antenna 4. At this time, since the radio wave transmission output does not change, the size of the communication area P3 does not change. Therefore, when the worker moves from position K2 to position K3, a message indicating that the number of receptions N exceeds the first threshold value L1 and the wireless communication state with the reading target tag T1 is good is displayed on the display 2. Is done.

  Thereafter, by repeating the same operation, even if the reading target tag T1 is mixed in the wireless tag group, the operator can quickly approach the direction in which the reading target tag T1 exists. As a result, the reading target tag T1 can be detected in a short time. In this case, as shown in FIG. 8, even if another wireless tag T2 is interposed between the reading target tag T1 and the antenna 4, these tags T2 do not become an obstacle to search.

(Second Embodiment)
Next, a second embodiment in which the reception state detection unit 151 has another aspect will be described with reference to FIG. FIG. 9 is a flowchart showing a processing procedure of the control unit 15, and steps common to FIG. 5 showing the processing procedure of the first embodiment are denoted by the same reference numerals.

  That is, in the second embodiment, the control unit 15 that has started the search for the reading target tag receives the reception success rate X every time the ID information stored in the storage unit 12 as the reading target tag designation information is received from the wireless tag. (ST21, ST23: reception state detection unit 151).

  The reception success rate X is calculated by dividing the number of receptions N by the number of rounds from the start of search. For example, if the ID information of the reading target tag T1 is received eight times during the first to tenth rounds, the reception success rate X is 80%.

  The control unit 15 monitors whether the reception success rate X has exceeded the first threshold value L1 before changing the transmission output (ST22). The first threshold value L1 is set to a value that can determine that the wireless communication state with the reading target tag T1 is good, for example, 50%.

  If the reception success rate X exceeds the first threshold value L1 (YES in ST22), the control unit 15 causes the display 2 to display a message indicating that the wireless communication state with the reading target tag is good ( ST7: Reception state notifying unit 155).

  Further, after changing the transmission output, the control unit 15 monitors whether or not the reception success rate X is below the second threshold value L2 (ST24). The second threshold value L2 is a value sufficiently smaller than the first threshold value L1, for example, 20%.

  When reception success rate X falls below second threshold L2 (YES in ST24), control unit 15 causes display 2 to display a message notifying that transmission output has been changed (ST14). Further, a message for instructing the operator to move the search position so as to approach the wireless tag side is also displayed (ST15).

  Also in the second embodiment having such a configuration, it is possible to search for the reading target tag T1 by the same method as in the first embodiment.

  In the second embodiment, since the operator changes the direction of the antenna surface 4C and the reading target tag T1 is not included in the communication area, the reception success rate X becomes smaller than the first threshold value L1. . As a result, a message indicating that the reception state is good is not notified. Therefore, the operator can surely recognize the direction in which the reception success rate X exceeds the first threshold value L1, that is, the direction in which the reading target tag T1 exists.

(Third embodiment)
Next, a third embodiment in which the reception state detection unit 151 is further modified will be described with reference to FIG. FIG. 10 is a flowchart showing a processing procedure of the control unit 15, and steps common to FIG. 5 showing the processing procedure of the first embodiment are denoted by the same reference numerals.

  That is, in the third embodiment, the control unit 15 that has started searching for a reading target tag detects the received signal strength Y every time it receives ID information of the reading target tag (ST31, ST33: reception state detection unit). 151).

  The received signal strength Y is detected by the received signal level detector 35. The control unit 15 samples the received signal level value at predetermined intervals while receiving ID information from the wireless tag. Then, an average value within the reception period is calculated and detected as reception signal strength Y. Instead of the average value, an integral value or a peak value may be detected as the received signal strength Y.

  The control unit 15 monitors whether or not the received signal strength Y exceeds the first threshold value L1 before changing the transmission output (ST32). If received signal strength Y exceeds first threshold value L1 (YES in ST32), control unit 15 causes display 2 to display a message indicating that the wireless communication state with the reading target tag is good ( ST7: Reception state notifying unit 155).

  Further, after changing the transmission output, control unit 15 monitors whether received signal strength Y has fallen below second threshold value L2 (ST34). When received signal strength Y falls below second threshold L2 (YES in ST34), control unit 15 causes display 2 to display a message notifying the end of transmission output change (ST14). Further, a message for instructing the operator to move the search position so as to approach the wireless tag side is also displayed (ST15).

  Also in the third embodiment having such a configuration, the same operational effects as those of the second embodiment can be obtained.

(Fourth embodiment)
Next, a fourth embodiment in which the switching determination unit 153 has another aspect will be described with reference to FIGS. 11 and 12. FIG. 11 is a block diagram illustrating a configuration of a main part of the wireless tag communication device 1, and the same reference numerals are given to the same portions as those in FIG. FIG. 12 is a flowchart showing a processing procedure of the control unit 15, and steps common to FIG. 9 showing the procedure of the second embodiment are denoted by the same reference numerals.

  That is, in the fourth embodiment, the control unit 15 constitutes a maximum detection unit 156 instead of the instruction reception unit 154. The maximum detection unit 156 detects the maximum value of the detection result of the radio wave reception state by the reception state detection unit 151. In addition, the control unit 15 constitutes a threshold value variable unit 157.

  In the fourth embodiment, the reception state detection unit 151 detects the reception success rate X. Therefore, the maximum detection unit 156 detects the maximum value of the reception success rate X. For example, if the reception success rate X becomes 90% or more close to the upper limit of the detection range, the control unit 15 detects that the reception success rate X is a maximum value.

  As shown in FIG. 12, the control unit 15 that has displayed on the display 2 a message that the reception success rate X exceeds the first threshold value L1 and the wireless communication state with the reading target tag is good. It is determined whether the reception success rate X is a maximum (ST41: switching determination unit 153). When the reception success rate X is not maximal (NO in ST41), the control unit 15 continues the wireless communication protocol.

  If reception success rate X is maximal (YES in ST41), control unit 15 causes display 2 to display a message indicating that reception success rate X is maximal (ST42). Then, an elapsed time after detecting that the reception success rate X is maximum is obtained (ST43). When the preset time has not elapsed (NO in ST43), control unit 15 continues the wireless communication protocol.

  When a predetermined time elapses after the reception success rate X becomes maximum (YES in ST43), the control unit 15 sets the second threshold value L2 in accordance with the maximum value (ST44: threshold value variable unit). 157). For example, the control unit 15 sets 20% of the maximum value as the second threshold value L2.

  When the second threshold L2 is set, a message indicating that the transmission output is reduced is displayed on the display 2 (ST9), and the process proceeds to step ST10 and subsequent steps. At this time, the second threshold value L2 used in the process of step ST24 is a value set in the process of step ST44.

  In the fourth embodiment, when it is determined that the communication state with the reading target tag T1 is good (YES in ST43), the radio wave transmission output is automatically reduced. Therefore, the key operation for instructing the change of the transmission output becomes unnecessary, and the workability is improved.

(Fifth embodiment)
Next, a fifth embodiment in which the switching determination unit 153 is further modified will be described with reference to FIG. FIG. 13 is a flowchart showing a processing procedure of the control unit 15, and steps common to FIG. 9 showing the processing procedure of the second embodiment are denoted by the same reference numerals.

  That is, in the fifth embodiment, after a message indicating that the wireless communication state with the reading target tag T1 is good is displayed on the display 2 (ST7), the control unit 15 determines that the reception success rate X is the first. The elapsed time in the state exceeding the threshold value L1 is obtained (ST51). When the preset time has not elapsed (NO in ST51), control unit 15 continues the wireless communication protocol.

  When the reception success rate X exceeds the first threshold value L1 continues for a predetermined time (YES in ST51), the control unit 15 causes the display 2 to display a message indicating that the transmission output decreases (ST9). The process proceeds to step ST10 and subsequent steps.

  Also in the fifth embodiment having such a configuration, the key operation for instructing the change of the transmission output becomes unnecessary, and the workability is improved.

(Sixth embodiment)
Next, a sixth embodiment in which the switching determination unit 153 is further modified will be described with reference to FIG. FIG. 14 is a flowchart showing the processing procedure of the control unit 15, and steps common to FIG. 13 showing the processing procedure of the fifth embodiment are denoted by the same reference numerals.

  That is, in the sixth embodiment, when the transmission output P is set, the control unit 15 determines the first threshold value L1 according to the transmission output P (ST61). In the process of step ST22, the first threshold value L1 determined in step ST61 is used.

  For example, the wireless tag communication device 1 stores a threshold value table in which the larger value is set as the value of the corresponding transmission output P becomes smaller in the storage unit 12. And the control part 15 searches the said threshold value table with the present transmission output P, and determines a corresponding value as the 1st threshold value L1.

  In FIG. 8, the operator searching for the reading target tag T1 first stands at the position K1, subsequently moves to the position K2, and further moves to the position K3. Thus, every time the worker approaches the reading target tag T1, the transmission output P of the radio wave radiated from the antenna 4 becomes small.

  According to the sixth embodiment, every time the radio wave transmission output P decreases, the first threshold value L1 increases. That is, the criterion for determining that the wireless communication state with the reading target tag T1 is good is high. Therefore, the direction in which the reading target tag T1 exists can be searched for more reliably.

  The present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage.

  For example, in the above-described embodiment, the RFID tag communication device 1 in which the housing 1A and the antenna unit 4A of the RFID tag communication device 1 are separated and connected by the antenna cable 5 is shown. However, the structure of the wireless tag communication device 1 is not limited to this. For example, the housing 1A and the antenna 4 may be integrated. The antenna 4 is not limited to a planar patch antenna. Any antenna that can communicate with a wireless tag can be used.

  In the embodiment, a message is displayed on the display 2 to notify the worker of various states. However, the notification function is not limited to this. For example, a voice synthesizer may be provided to notify the state by voice. Also, a buzzer may be provided to notify various states with different buzzer sounds.

  In the communication protocol of the embodiment, as shown in FIGS. 6 and 7, the SELECT command [S] including the ID information of the read target tag T1 is transmitted at the head of each round. For example, SELECT is performed every five rounds. The command [S] may be transmitted. In this case, there is a possibility that the ID information of the tag T2 other than the read target tag T1 may be received, but since the frequency is very low, there is no problem in practice.

  Further, by configuring the wireless tag communication device 1 so as not to accept ID information from wireless tags other than the reading target tag, it is possible to omit the function of wirelessly transmitting information specifying the reading target tag. . Further, the information specifying the reading target tag does not need to be all the ID information of the tag, and may be a part of the ID information.

  In the fourth to sixth embodiments, the reception success rate X of the second embodiment is used as the reception state detection unit 151. However, the usable reception state detection unit 151 is not limited to this. For example, it may be determined whether the reception state is good based on the number of receptions used in the first embodiment and the reception signal strength used in the third embodiment.

  In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, the constituent elements over different embodiments may be combined.

  DESCRIPTION OF SYMBOLS 1 ... RFID tag communication apparatus, 2 ... Display, 3 ... Keyboard, 4 ... Antenna, 11 ... Power supply part, 12 ... Memory | storage part, 13 ... Radio | wireless part, 13A ... Transmission part, 13B ... Reception part, 14 ... Communication interface, DESCRIPTION OF SYMBOLS 15 ... Control part 151 ... Reception state detection part 152 ... Transmission output control part 153 ... Switching determination part 154 ... Instruction reception part 155 ... Reception state notification part 156 ... Maximum detection part 157 ... Variable threshold value Department.

Claims (15)

A receiver that receives radio waves from the wireless tag via an antenna having maximum directivity in a specific direction;
A storage unit for storing information related to a target wireless tag designated as a reading target;
A reception state detection unit that detects a radio wave reception state of the target wireless tag in the reception unit;
A reception state notification unit for notifying the detection result of the radio wave reception state;
A wireless tag communication device comprising:   The wireless tag communication device according to claim 1, wherein the reception state detection unit detects the number of radio wave receptions of the target wireless tag within a predetermined time.   The wireless tag communication device according to claim 1, wherein the reception state detection unit detects a radio wave reception success rate of the target wireless tag within a predetermined time.   The wireless tag communication device according to claim 1, wherein the reception state detection unit detects a received signal intensity when the radio wave of the target wireless tag is received. A transmitter that wirelessly transmits information specifying the target wireless tag from the antenna;
The wireless tag communication device according to claim 1, further comprising:   The wireless tag communication device according to claim 5, wherein the transmission unit periodically wirelessly transmits information specifying the target wireless tag.   7. The wireless tag communication apparatus according to claim 5, wherein the information specifying the target wireless tag is a SELECT command. A switching determination unit that determines whether or not a predetermined transmission output switching condition is satisfied when a detection result of the radio wave reception state by the reception state detection unit is equal to or greater than a first threshold;
If it is determined by the switching determination unit that the transmission output switching condition is satisfied, the transmission output of the transmission unit is set to a second threshold value whose detection result of the radio wave reception state is smaller than the first threshold value. A transmission output control unit that reduces until
The wireless tag reader according to claim 5, further comprising: An instruction receiving unit that receives a transmission output change instruction of the transmitting unit;
The switching determination unit satisfies the transmission output switching condition when a reception output change instruction is received by the instruction reception unit when a detection result of the radio wave reception state by the reception state detection unit is equal to or greater than a first threshold. 9. The wireless tag communication device according to claim 8, wherein the determination is performed. A maximum detection unit for detecting a maximum value of the detection result of the radio wave reception state by the reception state detection unit;
The switching determination unit determines that the transmission output switching condition is satisfied when the reception state detection result has a maximum value greater than the first threshold value for a predetermined time or more. Wireless tag communication device. A threshold variable unit configured to vary the second threshold according to the maximum value detected by the maximum detection unit;
The wireless tag communication device according to claim 10, further comprising:   The switching determination unit determines that the transmission output switching condition is satisfied when a detection result of the radio wave reception state by the reception state detection unit is equal to or greater than a first threshold value for a predetermined time or more. 9. The wireless tag communication device according to 8.   The wireless tag communication device according to any one of claims 8 to 12, wherein the switching determination unit sets the first threshold value to a larger value as the transmission output decreases. A wireless tag searching method for a wireless tag communication device comprising an antenna having a maximum directivity in a specific direction,
Storing information on a target wireless tag designated as a reading target in a storage unit;
Detecting a radio wave reception state of the target radio tag at a receiving unit that receives radio waves of the radio tag via an antenna, and notifying a detection result of the radio wave reception state;
A method for searching for a wireless tag, comprising: In the transmission unit, wirelessly transmitting information specifying the target wireless tag from the antenna;
Determining whether a predetermined transmission output switching condition is satisfied when a detection result of the radio wave reception state is equal to or greater than a first threshold;
If it is determined that the transmission output switching condition is satisfied, the transmission output of the transmission unit is lowered until the detection result of the radio wave reception state becomes a second threshold value smaller than the first threshold value. thing,
The wireless tag searching method according to claim 14, further comprising:

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