Patent Application
20130021142
The present disclosure relates to an RFID system including an RFID tag that includes an antenna and an IC chip and a reader/writer communicating with the RFID tag for reading/writing information from and in a memory of the IC chip, and the RFID tag used in the RFID system.
In a site to which the RFID system is introduced, sometimes a range where communication can be conducted with the RFID tag (hereinafter simply referred to as a “tag”) attached to an article is restricted, or sometimes it is necessary to recognize a movement direction of the tag (article).
Conventionally a proposal, in which an antenna unit of the reader/writer is constructed by an array antenna to detect the movement direction of the tag or to adjust a directive characteristic of an emitted radio wave, is made in order to meet the demand (for example, see Patent Documents 1 and 2).
A method for changing the directive characteristic of the radio wave emitted from the antenna unit is well known as a general method for adjusting the range where the communication can be conducted with the RFID tag. However, the method is hardly adopted due to a restriction of Radio Act.
In the case that the array antenna is introduced to the reader/writer, sometimes each antenna constituting the array antenna conducts communication with the RFID tag to perform a calculation using signals received by the antennas. In such pieces of processing, a load of the calculation is increased in the reader/writer, and speed enhancement of the read/write processing is hardly achieved.
In view of the above problems, an object of the present disclosure is to easily implement the adjustment of the communicable range or the communication following the movement of the tag.
An RFID tag according to the present disclosure includes the function of setting (generating) a plurality of communication ranges expanding in relatively different directions when viewed from a surface (e.g., package surface) to face the reader/writer, and a function of returning, through a communication range in which a command from the reader/writer has been received, response information corresponding to the command to the reader/writer. On the other hand, the reader/writer selects at least one of the plurality of communication ranges, activates communication through the selected communication range and deactivates communication through a non-selected communication range, among (for) communications with the RFID tag.
According to the RFID system including the RFID tag and the reader/writer, the communication can be conducted in order to perform the read/write processing through the communication range, which can receive the radio wave from the reader/writer and selected by the reader/writer, in the plurality of communication ranges set by the RFID tag.
In the reader/writer, the range where the communication can be conducted with the tag can be changed by selecting the communication ranges. In the case that the communication is conducted with a moving tag, the communication following the movement of the tag can be conducted by properly switching the selection of the communication ranges while the reception of response information from the tag through the currently-selected communication range is checked. Only when the plurality of communication ranges are simultaneously selected to be able to conduct communication through both the communication ranges, the communication range can be restricted by activating the communication. When the communication can be conducted through at least one of the plurality of communication ranges, the communication can be conducted in a wide range by activating the communication.
In an RFID system of a first embodiment of the present disclosure, a plurality of antennas are adjusted to emit radio waves in directions different from each other, and an IC chip including a control circuit for operating these antennas independently from each other are provided. The reader/writer transmits a command including identification information of a communication range selected by the reader/writer. The control circuit of the IC chip executes the command from the reader/writer on condition that the command is received through an antenna matching the identification information in the command, and returns response information from the antenna that received the command.
According to the above configuration, the RFID tag has a possibility of receiving the command from the reader/writer through at least the two communication ranges. However, because the RFID tag reacts to the command only when receiving the command through the communication range selected by the reader/writer, there is no risk of performing the false processing by the command received through the communication range that is not selected. Therefore, accuracy of the read/write processing can be ensured.
An RFID tag according to a second embodiment is adapted (configured) to select any one of the plurality of communication ranges and activate only the selected communication range.
The reader/writer transmits, when switching of communication range selection becomes necessary, a command instructing the switching of the communication range to the RFID tag.
According to the above configuration, the RFID tag can receive the radio wave from the reader/writer, and the communication can be started when the selections of the communication ranges of the RFID tag and the reader/writer are matched with each other. Then, even if the necessity to switch the communication range selection is generated (realized), the communication range selection on the tag side can be switched by the command from the reader/writer similarly to the reader/writer, so that communication can be continued with no trouble.
An RFID tag according to a third embodiment is also adapted to select any one of the plurality of communication ranges and activate only the selected communication range.
The reader/writer of the third embodiment transmits a command including identification information of a communication range selected by the reader/writer. Further, the RFID tag, when receiving the command including the identification information of the selected communication range from the reader/writer, executes the command and returns response information corresponding to the command to the reader/writer, and when receiving a command including identification information of a communication range other than the selected communication range from the reader/writer, the RFID tag does not return the response information but switches selection to the communication range corresponding to the identification information included in the received command.
According to the above configuration, the RFID tag executes the command and returns the response information to the reader/writer, only when the communication range selected by the RFID tag is matched with the communication range selected by the reader/writer, and only when the command can be received from the reader/writer through the communication range. In the case, that the RFID tag selects the communication range that is not matched with the identification information in the command, the RFID tag does not respond to the command, but switches the selection to the communication range corresponding to the identification information in the received command. Therefore, the RFID tag can execute the command and return the response information by retransmitting the command from the reader/writer.
The communication can be conducted using only the communication range selected by the reader/writer through the processing, so that the read/write processing performed by the false communication can be prevented.
The RFID tag according to a fourth to a sixth embodiments is provided with a plurality of antennas having radio wave emission directions adjusted such that communication ranges are distributed along one width direction of a surface to face the reader/writer, and an IC chip including a control circuit operating these antennas independently from each other.
The RFID tag having the configuration can be attached to the moving article such that the direction in which the communication ranges are distributed corresponds to the movement direction. Therefore, in the fourth embodiment, the control circuit of the IC chip, receiving a command for detection from the reader/writer through at least one antenna, transmits response information including identification information of the communication range corresponding to the antenna, through the antenna that received the command. Further, the reader/writer transmits the command for detection with all of the plurality of communication ranges being in the selected state, and determines direction of movement of the tag based on the identification information included in the response information corresponding to the command.
According to the fourth embodiment, the reader/writer continuously transmits the detection command until receiving at least the initial response information, whereby the reader/writer can recognize the communication range corresponding to the antenna that initially receives the detection command from the reader/writer according to the movement of the tag. Therefore, the determination of the movement direction of the RFID tag can correctly be made based on the recognition result.
The reader/writer of the fifth embodiment selects at least two communication ranges arranged along the direction in which the communication ranges are distributed, and when, through at least one of the selected communication ranges, response information including identification information of the communication range is received corresponding to the transmitted command, activates the response information. Further, the control circuit of the IC chip, receiving a command from the reader/writer through at least one of the antennas corresponding to the communication ranges selected by the reader/writer, executes the command, and transmits response information including identification information of the corresponding communication range, through the antenna that received the command.
The reader/writer of the sixth embodiment selects at least two communication ranges arranged adjacently to each other along the direction in which the communication ranges are distributed, and when, from each of the selected communication ranges, response information including identification information of the range is received corresponding to the transmitted command and contents of these pieces of response information match, activates these pieces of response information. Further, when a command from the reader/writer is received from all antennas corresponding to the communication ranges selected by the reader/writer, the control circuit of the IC chip executes the command, and transmits, through all the antennas that received the command, response information including identification information of the communication range corresponding to each of the antennas.
The fifth embodiment can be adopted when the range where the communication can be conducted with the tag is widely set. On the other hand, the sixth embodiment can be adopted in the case that the range where the communication can be conducted with the tag is reduced rather than the case that the one communication range is selected.
According to the present disclosure, by selecting the communication range that is used to perform the read/write processing from the plurality of communication ranges on the RFID tag side, the position or the width of the communicable range can be adjusted, or the range can be changed while following the movement of the RFID tag. The processing of the reader/writer does not become complicated, so that the communication can stably be conducted even if the RFID tag moves at high speed or even if the number of communication times is set a large value.
The controller 21 of the reader/writer 2 receives a command from the upper-level device 3, and transfers the command to the RFID tag 1 from the antenna unit 20. Response information, which is received by the antenna unit 20 from the RFID tag 1 that executes the command, is output from the antenna unit 20 to the controller 21, and further output from the controller 21 to the upper-level device 3.
In each embodiment, the RFID tag 1 is designed such that two communication ranges A and B expanding in different directions are generated. In each of
As used herein, the communication ranges A and B are a range in which a radio wave can be transmitted to the antenna unit 20. The communication ranges A and B are distributed along a horizontal width direction of the package 10 by setting a directive characteristic of the radio wave emitted from the tag 1. The tags 1 of the embodiments in
Configurations of the RFID tags 1 of the embodiments will be described below with reference to
In the RFID tag 1 illustrated in
The processors 13A and 13B are arranged along the horizontal width direction of the package 10 while the antennas 11A and 11B are oriented toward the front surface 10a of the package 10. Each of the IC chips 12A and 12B of the processors 13A and 13B includes a control circuit, which includes a CPU and a nonvolatile memory, and a transmitting/receiving circuit. Dispositions of the processors 13A and 13B and the antennas 11A and 11B are not limited to the embodiments, but the processors 13A and 13B and the antennas 11A and 11B may be disposed in various ways while a direction of the radio wave emitted from each of the antennas 11A and 11B varies.
The antennas 11A and 11B emit the radio waves toward different directions. In
In the first embodiment, at least one of the antennas 11A and 11B receives the radio wave from the antenna unit 20 of the reader/writer 2, and therefore the RFID tag 1 is started to be able to conduct communication with the antenna unit 20 through the antenna that receives the radio wave. At this point, as described later, the controller 21 of the reader/writer 2 selects one of the communication ranges A and B, and only the communication conducted through the selected communication range is activated. The same communication control is applied to the tags 1 of the following embodiments.
An RFID tag 1 of a second embodiment illustrated in
Similarly to the first embodiment of
In an RFID tag 1 of a third embodiment illustrated in
In the third embodiment, the direction of the radio wave emitted from the antenna 11A is diagonally changed toward the upper right by the reflector 15, and the direction of the radio wave emitted from the antenna 11B is diagonally changed toward the upper left by the reflector 15. As a result, the same communication ranges A and B as the first and second embodiments are set.
The shape of the reflector 15 is not limited to the triangular prism. For example, two reflectors each of which is supported while a surface of a metallic plate is inclined may be introduced.
In the RFID tags 1 illustrated in
An RFID tag 1 of a fourth embodiment of
In an RFID tag 1 of the fifth embodiment of
In the tag 1 having the above configuration, a signal having a predetermined frequency transmitted from the IC chip 12 is distributed to the antennas 11A and 11B through the distributor. The variable phase shifter 17 changes a phase of the signal distributed to the antenna 11A, whereby the radio waves having phases different from each other are transmitted from the antennas 11A and 11B. A range where a composite wave of the radio waves is emitted becomes the communication range.
The direction in which the composite wave is emitted varies according to an amount of phase shift between the antennas 11A and 11B. Therefore, in the fifth embodiment, the variable phase shifter 17 is set while an adjustment amount of the phase is switched in two ways. The composite wave of the radio waves is diagonally emitted in the upper right direction to set the communication range A when one of the adjustment amounts is set, and the composite wave of the radio waves is diagonally emitted in the upper left direction to set the communication range B when the other adjustment amount is set. Further, one of the two adjustment amounts of the phase is selected as an initial state, and the initial state is properly switched to the other adjustment amount, which allows the communication ranges A and B to be switched.
In an RFID tag 1 of a sixth embodiment of
In an RFID tag 1 of a seventh embodiment of
In the embodiment, the direction of the reflector 15′ is changed by the direction switch 18′, which allows the emission direction of the radio wave to be switched. Specifically, in the case that the reflector 15′ is located in a posture illustrated by a solid line on the right of the antenna 11, the radio wave from the antenna 11 is diagonally emitted toward the upper left direction, thereby setting the communication range B. In the case that the reflector 15′ is located in a posture illustrated by a broken line on the left of the antenna 11, the radio wave from the antenna 11 is diagonally emitted toward the upper right direction, thereby setting the communication range A.
As described above, in the embodiments of
In the fifth embodiment of
The RFID tag 1 of each embodiment can be used while attached to the article conveyed along a predetermined direction such that the direction in which the communication ranges A and B are arranged corresponds to a conveying direction of the article.
In the RFID system in which the RFID tag 1 of each embodiment is used, each of the communication ranges A and B is managed by specific identification information. The identification information on each of the communication ranges A and B is registered as common information in the controller 21 of the reader/writer 2 and a memory of the IC chip 12 of each tag 1.
The identification information is not limited to one that directly indicates each of the communication ranges A and B. For example, in the case that the two antennas 11A and 11B are provided in the tag 1, an identification code that is used when the IC chip 12 controls the antennas 11A and 11B may be used as the identification information on each of the communication ranges A and B.
Similarly to the conventional art, the controller 21 of the reader/writer 2 transmits the command in order to detect the tag 1 that enters the communication range of the antenna unit 20, and conducts communication with the tag 1 that responds to the command. However, in the embodiments, one of the communication ranges A and B is selected, and the communication is conducted only through the selected communication range. The selection of the communication range is properly switched through a sequence of pieces of communication processing.
In
In the example of
Assuming that the tag 1 of each of the embodiments illustrated in
In the embodiments, the controller 21 of the reader/writer 2 is initially set to the state in which the communication range A is selected. Based on the initial setting, the controller 21 transmits a detection command including the identification information on the communication range A (Step S1). The detection command is repeatedly transmitted until the response from the RFID tag 1 is acquired.
When the tag 1 moves to a position in which the antenna 11A can receives the detection command, the circuit of the IC chip 12 is started (in
When the controller 21 of the reader/writer 2 receives the response information, the detection processing in Step S1 is ended and actual communication processing is started.
In this case, the controller 21 continuously transmits the command including the identification information on the communication range A in order to receive the response information from the tag 1 (Steps S2 to S4). When receiving the command through the antenna 11A, the control circuit of the IC chip 12 of the tag 1 checks that the identification information in the command is matched with the antenna 11A, and performs processing (for reading and writing information from and in the memory) according to the command. Further, the control circuit generates the response information indicating processing result, and transmits the processing result from the antenna 11A. Therefore, an affirmative determination is made in Step S3 of
Similarly the transmission of the command and the reception of the response information are repeated. At this point, an upper limit is set to the number of communication times that are performed while the communication range A is selected. When the number of communication times reaches the upper limit, the controller 21 determines that the selection of the communication range A is ended. Therefore, the affirmative determination is made in Step S4, and the flow goes to Step S5.
Although not clearly illustrated in
In Step S5, the communication range A is switched to the communication range B, and the command including the identification information on the communication range B is transmitted.
At this point, although the tag 1 possibly receives the command from the antenna 11A, the control circuit of the IC chip 12 does not react to the command including the identification information that does not correspond to the antenna receiving the command. However, in the case that the antennas 11A and 11B simultaneously receive the command, the control circuit of the IC chip 12 executes the command, and transmits the response information indicating the processing result from the antenna 11B. When the controller 21 of the reader/writer 2 receives the response information, the affirmative determination is made in Step S6.
In Step S5, the command can be retransmitted several times. Therefore, even if the antenna 11B does not receive the command that is transmitted immediately after the selections of the communication ranges are switched, when the antenna 11B receives the retransmitted command with the movement of the tag 1, the command can be executed and return the response information.
When receiving the response information from the tag 1, the controller 21 of the reader/writer 2 transmits the next command. The transmission of the command including the identification information on the communication range B and the reception of the response information are repeated until the transmission and reception of the necessary information are ended (a loop of Steps S5 to S7), and the processing is ended.
In the case that the response information is not acquired even if the command repeatedly retransmitted until the number of retransmission times reaches a permissible value in Step S5, the negative determination is made in Step S6, and error processing (Step S8) is performed.
After the communication range A that is initially generated by the radio wave of the antenna unit 20 is selected to start the communication, the communication processing is continued by switching the selection to the communication range B that is subsequently generated according to the movement of the tag 1, so that the range where the communication can be conducted on a movement path of the tag 1 can be expanded compared with the use of the tag in which only one communication range is generated. Accordingly, the communication can be conducted with no problem in the case that the tag 1 (article 30) moves at high speed, or in the case that the number of communication times is increased.
However, in the embodiments of
In the embodiments of
In the case that the communication processing of
The description will briefly be made because the basic flow of the procedure of
At the time the selection of the communication range A is ended, the controller 21 transmits the command to switch the selection to the communication range B as the final command including the identification information on the communication range A (Step S15). The RFID tag 1 that receives the command switches the state to the state in which the communication range B is selected, and returns the response information. When the controller 21 of the reader/writer 2 receives the response information, the affirmative determination is made in Step S16.
Then the controller 21 conducts communication with the tag 1 using the command including the identification information on the communication range B (Steps S17 and S18).
In the case that the response information cannot be received from the tag 1 with respect to the transmission of the command at each stage (in the case that a negative determination is made in any one of Steps S13, S16, and S18), the error processing (Step S20) is performed.
In the example of
In the case that the RFID tag 1 of any embodiment is used, when the RFID tag 1 moves to become the state in which the detection command is received through the communication range B, the RFID tag 1 initially reacts to the command to return the response information.
The controller 21 of the reader/writer 2 starts the actual communication in response to the response information, and the controller 21 switches the selection to the communication range A at the starting time of the actual communication and transmits the command including the identification information on the communication range A (Step S22).
In the case that the RFID tags 1 of the embodiments of
The transmission of the command including the identification information on the communication range A and the reception of the response information are repeated until the communication is conducted necessary times, and then the processing is ended (Steps S22 to S24). In Step S22 of the example of
In the case that the RFID tags 1 of the embodiments of
In the case that the tags 1 of the embodiments of
In the communication processing illustrated in
In the example of
When the communication proceeds smoothly to end all the pieces of communication, the controller 21 switches the selection of the communication range from the communication range B to the communication range A (Step S35). Therefore, the controller 21 becomes the state in which the detection command including the identification information on the communication range A can be transmitted again in order to detect the subsequent tag 1.
In the case that the communication processing is performed using the RFID tags 1 of the embodiments of
In the case that the conventional tag having only one communication range is used, the range where the communication can actually be conducted is narrowed by the communication for the tag detecting processing. On the other hand, according to the communication processing illustrated in
In the pieces of communication processing illustrated in
In the above examples, the reader/writer 2 selects one of the communication ranges A and B, and transmits the command including the identification information on the currently-selected communication range, thereby restricting the communication range that can be used to transmit the response information by the RFID tag 1. In the case that the RFID tag 1 (embodiments of
In examples of FIGS. 15(1) and 15(2), the controller 21 of the reader/writer 2 transmits the command that does not include the identification information on the communication range or the command that includes both the pieces of identification information on the communication ranges A and B. The command indicates that both the communication ranges A and B are selected.
In the example of FIG. 15(1), only when receiving the command of the reader/writer 2 from both the communication ranges A and B, the RFID tag 1 executes the command and returns the response information through the communication ranges A and B. At this point, the RFID 1 includes the identification information on the corresponding range in the response information transmitted to each of the communication ranges A and B.
When receiving the response information after the command is transmitted, the controller 21 of the reader/writer 2 distinguishes the communication ranges used to transmit the response information from each other based on the identification information in the response information. The controller 21 receives the pieces of response information from both the antennas 11A and 11B, and deals with the received response information as the activated one on the condition that contents except the pieces of identification information in the pieces of response information are matched with each other. When the response information is received from one of the communication ranges A and B, a determination that the communication is false is made to perform the error processing.
According to the processing, because the range where the communication ranges A and B overlap each other becomes the actual communication range, the communication can be conducted only when the good positional relationship holds between the tag 1 and the antenna unit 20, so that stability of the communication can be enhanced.
In the example of FIG. 15(2), the RFID tag 1 executes the command when receiving the command from the reader/writer 2 through at least one of the antennas 11A and 11B. From the antenna through which the command is received, the RFID tag 1 returns the response information including the identification information on the communication range corresponding to the antenna. When receiving the response information including the identification information on at least one of the currently-selected communication ranges A and B, the controller 21 of the reader/writer 2 determines that the communication is successful, and activates the response information.
According to the processing, the communication can be conducted for the purpose of the read/write processing in the whole range covering the communication ranges A and B.
For example, as illustrated in FIG. 16(1), in the case that the tag 1 moves in the conveyance path 40 along the direction of the arrow F (from the right toward the left in FIG. 16(1)), because the antenna 11A initially receives the detection command, the tag 1 transmits the response information including the identification information on the communication range A. On the other hand, as illustrated in FIG. 16(2), in the case that the tag 1 moves along the direction of an arrow H (from the left toward the right in FIG. 16(2)), because the antenna 11B initially receives the detection command, the tag 1 returns the response information including the identification information on the communication range B from the antenna 11B.
Therefore, the controller 21 of the reader/writer 2 determines that the tag 1 moves along the direction F in the case that the initially-received response information includes the identification information on the communication range A, and the controller 21 determines that the tag 1 moves along the direction H in the case that the received response information includes the identification information on the communication range B. The determination result is transmitted to the upper-level device 3, and the determination result can be utilized in controlling an operation of another device (such as a robot that picks up the article 30).
Further, after the determination, the controller 21 of the reader/writer 2 puts the tag 1 into the state in which only the communication range of the identification information included in the response information with respect to the detection command is selected, and the controller 21 can conduct communication with the tag 1 for the purpose of the read/write processing. The controller 21 can also continue the communication with the tag 1 while switching the selection to the other communication range.
After receiving the response information, the controller 21 of the reader/writer 2 continues the transmission to the detection command to check a change of the identification information included in the response information every time, which allows a movement speed to be determined along with the movement direction of the tag.
In the above embodiments, in the case that the radio wave propagates in the wide range from the antenna unit 20, possibly both the antennas 11A and 11B of the tag 1 receives the detection command to respond immediately after the transmission of the detection command is started. Even in such cases, the movement direction of the tag 1 can be determined based on magnitude of a voltage of the received signal and the identification information.
In other words, the determination that the tag 1 moves along the direction F is made in the case that the signal including the identification information on the communication range A is larger than the signal including the identification information on the communication range B, and the determination that the tag 1 moves along the direction H is made in the case that the signal including the identification information on the communication range B is larger than the signal including the identification information on the communication range A.
The embodiments are described about the configuration and the communication processing of the RFID tag 1 in the passive RFID system. The embodiments can also be applied to semi-passive or active RFID systems.
RFID tag, 2 reader/writer, 10 package, 10a front surface of package, 11 (11A, 11B) antenna, 12 (12A, 12B) IC chip, 15,15′ reflector, 16 switch mechanism, 17 variable phase shifter, 18,18′ direction switch, 20 antenna unit, 21 controller
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-207033 | Sep 2010 | JP | national |
This is a continuation application of PCT/JP11/056,433 filed Mar. 17, 2011, designating the United States of America, the disclosure of which, including the specification, drawings, and claims, is incorporated by reference in its entirety. The disclosure of Japanese Patent Application No. 2010-207033 filed Sep. 15, 2010, including the specification, drawings, and claims are expressly incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2011/056433 | Mar 2011 | US |
| Child | 13358817 | US |
