JP4803132B2 - Non-contact communication device and non-contact communication method - Google Patents

Description

  The present invention belongs to a technology that performs non-contact communication with an RFID (Radio Frequency Identification) tag having a built-in semiconductor memory, and in particular, controls a plurality of antennas arranged such that different ranges are communication areas. The present invention relates to an apparatus and a method for communicating with an RFID tag.

  An antenna that communicates with an RFID tag that does not have an internal power supply (hereinafter sometimes simply referred to as a “tag”) electromagnetically couples the tag with a carrier wave of a predetermined frequency, and generates power necessary for communication with the tag. Under this state, a predetermined command signal is placed on the carrier wave and transmitted to the tag. When the RFID tag responds to a command from the antenna, the state of the carrier wave is changed by the response signal. Therefore, on the antenna side, the contents of the command can be demodulated by processing the carrier wave within a predetermined period after the command transmission (see Patent Document 1).

Japanese Patent No. 3874007

  Furthermore, in order to solve problems such as limiting the tags to be communicated, recognizing the position of the tags, and stably communicating with moving tags, this type of antenna is used. It has been proposed to communicate with one tag.

  For example, in Patent Document 2 below, two antennas are arranged so that their wireless communication zones intersect, and the moving tag (wireless card) exceeds the threshold for both the command signal (activation code) from each antenna. It is described that a response is made when received at a level to prevent interference. In Patent Document 3, a plurality of reception-only antennas are arranged in the communication area of the interrogator, and response signals from the moving body with respect to the signals from the interrogator are received by the respective reception-only antennas, and the response demodulated by the interrogator It is described that the position of the moving body is specified based on the reception area of the antenna that has received the signal that matches the signal.

JP 7-95119 A Japanese Patent Laid-Open No. 8-190441

  When communication with one RFID tag is performed using a plurality of antennas, processing is generally performed according to the flow shown in FIG.

  In FIG. 9, the “first antenna” and the “second antenna” are arranged so that parts of the communication area overlap each other, and communication with the tag is performed in the order of the first antenna and the second antenna. . In any antenna communication, first, power is generated in the tag by a carrier wave from the antenna (hereinafter, this state is referred to as “tag activation”), and a command is transmitted from the antenna under this state. Furthermore, the period from the command transmission until a predetermined time elapses is set to a period during which a response from the tag can be received (hereinafter, this state is referred to as “response reception”), and the received signal of the antenna in the meantime is processed. (The range indicated by the hatched pattern during the response reception period is the period during which the response signal is actually received.) Thereafter, processing for recognizing the response content from the tag is performed using the received signal of each antenna.

  However, in the method in which processing by each antenna is performed serially as described above, it is necessary to switch the antenna that communicates with the tag and repeat command transmission and response reception, so that communication time is inevitably increased. Moreover, even when no tag is present in the antenna communication area, command transmission and response reception by each antenna is repeated, resulting in an increase in wasted time. Further, when communication is performed while moving the tag, the movement speed cannot be followed and communication may fail.

  The present invention pays attention to these problems, and greatly reduces the communication time when a plurality of antennas are used, and enables efficient communication processing with the RFID tag by simple signal processing. And

A non-contact communication apparatus for solving the above problems controls a plurality of antennas arranged along a moving path of an RFID tag so that a part of the communication area overlaps a part of another communication area. The first control means for performing non-contact communication with the RFID tag, and controlling so that all the carrier waves between the antennas emitting the carrier waves are in a synchronized state, and any one of the plurality of antennas. or one in the process of transmitting a command to the RFID tag, as the first antenna corresponding to a communication area where RFID tag enters the first run multiple times while switching the antennas to transmit a command in the order of arrangement of the antenna In addition, for the transmission of a command from the antenna corresponding to each communication area other than the communication area where the RFID tag enters last, the antenna that transmitted the command A second control means for setting ready to receive a response signal from the RFID tag by a carrier wave yet an antenna that does not send a command for that next came off of the synchronization and, each time the above command is transmitted And signal processing means for decoding a response signal from the RFID tag in response to the command by processing a received signal after the command transmission of each antenna set in a receivable state.

Further, the second control means is configured so that two antennas set in a receivable state receive response signals from the RFID tag in response to transmission of commands from each antenna excluding the antenna corresponding to the communication area where the RFID tag enters last. Is received based on the result of the decoding process for each received signal, and if it is determined that only the antenna that transmitted the command has received the response signal, the next command is also transmitted to the antenna and received. When it is determined that the two antennas set to the enabled state have received the response signal, the next command is transmitted to the antenna that has not yet transmitted the command.

  In this way, a response signal for one command is simultaneously received by a plurality of antennas whose overlapping portions are set in the communication area, so that a command is transmitted and a response signal is individually received for each antenna. Communication time can be greatly reduced. Further, in the antenna set so as to receive the response signal, the carrier waves are all in a synchronized state, so that it is possible to prevent interference between the antennas between the antennas. Therefore, a highly reliable received signal can be obtained from any antenna, and the accuracy of decoding of the response signal can be ensured.

  According to the above configuration, when a plurality of cycles of communication is performed for one tag, even if the tag to be communicated moves, a command can always be transmitted from an antenna that can communicate with the tag, and communication is hindered. Can be done without.

In a preferred aspect of the apparatus configured as described above , the second control means causes the antenna other than the antenna that transmits the command to be in a dormant state, and the command is transmitted to an antenna that should be able to receive a response signal from the RFID tag. In response to this, a state is set in which a carrier wave is transmitted.

This invention controls a plurality of antennas arranged along the movement path of the RFID tag so that a part of the communication area overlaps with a part of the other communication area, thereby performing non-contact communication with the RFID tag. Applies to how to do. In this way, each RFID tag communication target, the processing for transmitting a command to the RFID tag to any one of the plurality of antennas, as the first antenna corresponding to a communication area where RFID tag enters the first, Execute multiple times while switching the antenna to send the command in the order of the antenna arrangement. In addition, in response to the transmission of a command from each antenna other than the antenna corresponding to the communication area in which the RFID tag enters last, the antenna that has transmitted the command and the antenna that has not transmitted the command next to the antenna are transmitted between these antennas. By continuously sending a synchronized carrier wave, it is possible to receive a response signal from the RFID tag for the command, and when only the antenna that transmitted the command of the two antennas receives the response signal, The command is also transmitted from the antenna, and when both antennas receive the response signal, the next command is transmitted from the antenna that has not yet transmitted the command.

Further, each time a command is transmitted, the response signal from the RFID tag to the command is decoded by processing the received signal of the antenna set in the receivable state.

In the above non-contact communication apparatus and non-contact communication method, a command is transmitted only from any one of a plurality of antennas, and a response signal from the RFID tag in response to the command is transmitted to the antenna that has transmitted the command and the communication area of the antenna. Can be received simultaneously with overlapping antennas, the time required for communication can be greatly reduced. Also, when receiving the response signal from the tag, all the carrier waves of the antenna that can be received are in a synchronized state, so that there is no interference between the antennas, Even when processing is performed simultaneously, accurate decoding processing can be performed. Further, since a command can be transmitted from an antenna that can always communicate with a moving RFID tag, communication of a plurality of cycles can be performed without any trouble.

FIG. 1 shows a configuration example of an RFID system.
This RFID system communicates with a plurality of RFID tags 5 that do not have an internal power supply in order, and executes processing such as reading data written in the internal memory of the tag 5 or rewriting to new data. The two antennas 1A and 1B having the above performance, the controller 2 that controls the operation of these antennas 1A and 1B, and the host device 3 such as a personal computer are included.

Each tag 5 moves in order along the direction of arrow D _A or D _{B in} the figure.
The antennas 1A and 1B are arranged such that the communication areas 4A and 4B are aligned along the moving direction of the tag 5 and partially overlap. Hereinafter, when individually referring to the antennas 1A and 1B, the antenna 1A is referred to as a “first antenna 1A” and the antenna 1B is referred to as a “second antenna 1B”. Further, a range not included in the communication area 4B of the second antenna 1B in the communication area 4A of the first antenna 1A is referred to as an area r1, and included in the communication area 4A of the first antenna in the communication area 4B of the second antenna 1B. The range where there is no area is called area r2, and the area where both communication areas 4A and 4B overlap is called area r3.

  The controller 2 is generally called a “reader / writer”, and supplies a high-frequency carrier signal to the antennas 1A and 1B to generate a carrier wave necessary for communication with the tag 5. When a command signal is received from the host device 3, the carrier signal modulated by this command signal is supplied to the antennas 1A and 1B. Further, a signal component (reception signal) superimposed on the carrier wave after command transmission is extracted, and a response signal from the tag 5 to the command is decoded from this reception signal. Since this response signal is obtained by processing the response data generated by the control unit of the tag based on the communication rules, the controller 2 restores the original response data from the communication signal to the host device 3. Send.

  Carrier waves are always transmitted from the antennas 1A and 1B. Each tag 5 is activated by being electromagnetically coupled to the antenna (1A or 1B) corresponding to the area by the carrier wave in the first communication area (area 4A or 4B), and is ready to receive a command.

  In the RFID system described above, by using the two antennas 1A and 1B, the range in which communication is effective is limited or the range in which communication is possible is expanded. Furthermore, a device has been devised for ensuring the accuracy of communication while greatly reducing the time required for communication when two antennas are used.

  Hereinafter, various communication methods will be specifically described with reference to FIGS. In these examples, only one type of command is transmitted to each tag 5 in order to simplify the description.

  FIG. 2 shows operations of the antennas 1A and 1B and the tag 5 when the tag 5 to be communicated is stopped in any of the areas r1, r2, and r3 to perform communication. In this case, communication when the tag 5 returns a response from the area to be stopped is validated. Hereinafter, this communication is referred to as “region-limited communication”.

  This type of communication is applied, for example, when communication is performed while sequentially loading a plurality of tags 5 arranged at predetermined intervals into the communication area 4A or 4B. In this case, in order to enable communication even if the moving path of the tag 5 is away from the antenna installation position to some extent, it is necessary to set a wider antenna communication area. However, when the communication area is widened, the tag 5 that is not a communication object also enters the communication area and reacts to the command, which may cause an error in the processing result.

In the area-limited communication, not only the response signal from the tag 5 to the command is received, but also the position of the tag 5 at the time of the response is recognized, and whether or not the response signal received by that position is treated as valid Is determined. The position of the tag 5 is recognized by whether or not the first antenna 1A and the second antenna 1B have received the response signal from the tag 5.
Further, in this embodiment, a command is transmitted only from the antenna that activates the tag 5, and a response signal from the tag 5 to this command is received by both the antennas 1A and 1B, thereby reducing the time required for communication. I'm crazy.

In the example of FIG. 2, three operations of “tag activation”, “command transmission”, and “response reception” are shown as operations on the antenna side, but no signal component is placed in “tag activation” and “response reception”. A carrier wave is transmitted, and in “command transmission”, a carrier wave carrying a signal component of a predetermined command signal is transmitted. The controller 2 transmits a command while managing the time for starting the tag 5 and the time required for receiving the response signal, and receives the received signals input from the antennas 1A and 1B within a predetermined time after the command is transmitted. To process. Also in the examples of FIGS. 3 and 4 below, the processes of “tag activation”, “command transmission”, and “response reception” are executed by the same control.
In FIGS. 2 and 3, among the “response reception” periods of the antennas 1 </ b> A and 1 </ b> B, the period during which the response signal from the tag 5 can actually be received is indicated by the hatched pattern.

  In the example of FIGS. 2 (1) and 2 (2), a command is received from the first antenna 1A, and a response signal from the tag 5 to this command is received by both antennas 1A and 1B. In this case, if the tag 5 is stopped in the communication area 4A, it is activated by a carrier wave from the first antenna 1A, receives a command from the first antenna 1A, performs processing according to the command, and responds. Send a signal.

When the tag 5 is located in the region r1 in FIG. 1, the first antenna 1A can receive the response signal from the tag 5, as shown in FIG. The response signal cannot be received by the two antennas 1B.
On the other hand, when the tag 5 is located in the region r3 of FIG. 1, the response signal can be received by both the first and second antennas 1A and 1B as shown in FIG. 2 (2). .

  In the example of FIG. 2 (3), a command is transmitted from the second antenna 1B contrary to the above examples. Here, when the tag 5 is located in the region r2, the second antenna 1B can receive the response signal from the tag 5, but the first antenna 1A cannot receive the response signal. . Further, when the tag 5 is located in the region r3, both the first and second antennas 1A and 1B respond to the command from the second antenna 1B as in the example of FIG. 2 (2). A response signal can be received.

  Therefore, when the communication when the tag 5 is located in the region r1 or the region r2 is validated, the command is transmitted from the antenna including the region in the communication region, and the response signal from the tag 5 is transmitted to the antenna. Only when it can be received, “communication success” is assumed. On the other hand, when the communication when the tag is located in the region r3 is validated, the command is transmitted from either one of the antennas, and the response signal from the tag 5 is received by both the antennas 1A and 1B. “Communication success”.

Note that the number of antennas used for the communication is not limited to two, and three or more antennas may be used. In this case, it is possible to perform processing such as validating communication only in the overlapping range of all antenna communication areas, or specifying the position of the tag finely by combining the antennas that have received the response signal.
Further, the above-described position recognition processing of the tag 5 can also be applied to the case where communication is performed while moving the tag 5 as shown in FIG.

  In the example of FIG. 3, communication in a range including the communication areas 4A and 4B of the first and second antennas 1A and 1B is made effective (that is, the tag 5 is connected to at least one of the antennas 1A and 1B). I think it would be good if we could communicate). Hereinafter, this communication is referred to as “region expansion communication”.

  The area enlargement type communication is useful when communication is performed while the tag 5 is moved. If communication is performed with one antenna when the tag 5 is not stopped, even if a command can be transmitted to the tag 5, the tag 5 may leave the communication area in the middle of receiving a response signal. In the example of FIG. 3, after the tag 5 leaves the communication area of one antenna, the response signal is continuously received by another antenna.

3 (1) shows an example of operation when the tag 5 is moved along the direction of arrow D _A, an example of operation when FIG. 3 (2) of the tag 5 is moved along the direction of arrow D _B Show. As shown in these examples, even in the area expansion type communication, basically, as in the area limited type communication, a command is transmitted from the antenna that activates the tag 5, and a response signal from the tag 5 to the command is transmitted. Are received simultaneously by each antenna.

  However, when the tag 5 moves, the antenna that can receive the response signal changes depending on its position. In order to clarify the relationship between this change and the position of the tag 5, FIGS. 3 (1) and 2 (2) show the region including the tag 5 along with the operations of the antennas 1 A and 1 B and the tag 5.

If the tag 5 is moved along the direction of arrow D _A, as shown in FIG. 3 (1), the tag 5 is started enters the region r1 in communication area 4A of the antenna 1A, from the antenna 1A Starts a response after receiving a command. In the example of FIG. 3A, since the tag 5 is still in the region r1 at the start of the response, only the antenna 1A receives the response signal. Thereafter, when the tag 5 moves from the region r1 to the region r3, both the antennas 1A and 1B are in a state of receiving a response signal. Further, when the tag 5 moves from the region r3 to the region r2, the antenna 1A cannot receive the response signal, but the antenna 1B can continue to receive the response signal.

If the tag 5 is moved along the direction of arrow D _B, as shown in FIG. 3 (2), the tag 5 is started enters the region r2 in communication area 4B of the antenna 1B, from the antenna 1B Starts a response after receiving a command. In the example of FIG. 3B, since the tag 5 is still in the region r2 at the start of the response, only the antenna 1B receives the response signal. Thereafter, when the tag 5 moves from the region r2 to the region r3, both the antennas 1B and 1A receive the response signal. After a while, when the tag 5 moves from the region r3 to the region r1, the antenna 1B cannot receive the response signal, but the antenna 1A continues to receive the response signal.

  As described above, in the communication process of the area expansion method of this embodiment, after transmitting a command from the antenna that activates the tag 5, the antennas 1A and 1B simultaneously receive the tag. Even if the region where 5 is located is changed, a response signal can be received by at least one of the antennas 1A and 1B.

  However, if the antenna that receives the response signal is switched while the response from the tag 5 is performed, neither of the antennas 1A and 1B can receive the entire response signal alone. In this embodiment, therefore, the logical sum operation of both signals is performed on the received signals of the antennas 1A and 1B during the response reception period, and the entire content of the response signal is decoded using the calculation result. Yes. In this way, it is possible to decode a complete response signal as long as the switching of the antenna that receives the response signal occurs at any time as long as the switching is within the response reception period. Therefore, communication with the moving tag 5 can be performed without hindrance.

FIG. 4 shows another example of area enlargement type communication.
In the examples of FIGS. 2 and 3 described above, commands are transmitted in a batch from the antenna 1A or 1B. However, in the example of FIG. 4, the commands are transmitted in consideration of the possibility of communication failure due to noise. It is divided into a plurality of packets and each packet is transmitted in order.

  If communication fails due to noise, it is necessary to repeat the same communication. If the command capacity is large, processing time may be lost due to failed communication or re-communication, and the tag 5 may not be able to handle the movement. is there. For this reason, in the example of FIG. 4, the command is divided and transmitted so that the processing time loss at the time of communication failure is reduced. Furthermore, the processing time required for communication can be shortened by performing the same processing as in the examples of FIGS. However, since the communication is performed while moving the tag 5, if the antenna for transmitting the command is fixed, the command may not reach the tag 5 during the communication, and the command is transmitted according to the change in the position of the tag 5. It is necessary to switch the antenna.

  In the example of FIG. 4, in consideration of the above points, if the response signal from the tag 5 to the command is received only by the antenna that transmitted the command, the next command is also received from the same antenna as the previous time. When both antennas 1A and 1B are ready to receive a response signal, the antenna that transmits the next command is switched. In FIG. 4, an area including the tag at the time of response is shown in a box indicating the response processing on the tag side.

4 (1) shows an example of operation when the tag 5 is moved along the direction of arrow D _A. In this case, in the initial state, a command is transmitted from the first antenna 1A that activates the tag 5, and then the antennas 1A and 1B are simultaneously in a response reception state. As indicated by the hatched portion in the figure, while the tag 5 is in the region r1, only the first antenna 1A actually receives the response signal. While this reception state continues, the antenna that transmits the command is maintained as the first antenna 1A.

  When the tag 5 moves to the region r3 after a predetermined time, the response signal from the tag 5 is received by both the antennas 1A and 1B. In such a reception state, subsequent commands are transmitted from the second antenna 1B. Therefore, even if the tag 5 subsequently moves from the region r3 to the region r2 and communication with the antenna 1A becomes impossible, all commands can be delivered to the tag 5, and responses from the tag 5 to each command are possible. Signals can be received without any problem.

4 (2), the tag 5 is the operation example of the case of moving along the direction of arrow D _B. In this case, contrary to the example of FIG. 4 (1), a command is initially transmitted from the second antenna 1B, and only the second antenna 1B receives a response signal from the tag 5. When both antennas 1A and 1B receive a response signal from the tag 5, the antenna that transmits subsequent commands is switched to the first antenna 1A.

  Even after the antenna for transmitting the command is switched, the antennas 1A and 1B both receive the response, but the antenna that cannot communicate with the tag 5 (in the case of FIG. 4 (1), the first antenna 1A and FIG. 4). In the case of (2), the necessity of processing the received signal of the second antenna 1B) is eliminated. For this reason, in FIG. 4, the response reception period of the antenna that is unable to communicate with the tag 5 is indicated by a dotted frame.

Also, in the communication process of FIGS. 3 and 4, the number of antennas to be used is not limited to two, and three or more antennas may be used. In this case, the antennas 1A and 1B are arranged in order along the moving direction of the tag, and are arranged so as to overlap between adjacent communication areas. In the case of using three or more antennas for the processing of FIG. 4, for the hourly command, the antenna that transmitted the command and the adjacent antenna (limited to those arranged on the tag moving direction side). May be processed, and other antennas may be removed from the processing target. Also in this case, when the response signal from the tag can be received from both antennas to be processed, the antenna for transmitting the next command is switched.

FIG. 5 is a block diagram of the RFID system showing the configuration of the controller 2 in detail.
The controller 2 of this embodiment is provided with transmitters 22A and 22B and receivers 23A and 23B for each of the antennas 1A and 1B in addition to the control unit 21 using a microcomputer (in FIG. 5, the first antenna 1A side). Transmitter / receivers 22A and 23A are referred to as "first transmitter 22A" and "first receiver 23A", and transmitter / receivers 22B and 23B on the second antenna 1B side are referred to as "second transmitter 22B" and "second receiver 23B". To do.) Further, the controller 2 is provided with a setting unit 24 for various setting operations and a display unit 25 for displaying setting contents by the setting unit 24.

  The control unit 21 outputs a carrier signal having a predetermined frequency based on a high frequency pulse from an oscillation circuit (not shown). The carrier signal transmission line is divided into two and input to the first and second transmitters 22A and 22B, respectively. The control unit 21 also outputs a clock signal for sampling the received signal (hereinafter referred to as “received clock signal”), and the transmission line of the received clock signal is also divided into two parts. The data is input to the receivers 23A and 23B.

In addition, a transmission line for command signals is provided for each transmission unit between the control unit 21 and each transmission unit 22A, 22B. When transmitting a command, the command is supplied only to the transmission unit corresponding to the communication area in which the tag 5 first enters based on the moving direction of the tag 5.
Further, a transmission line for received signals is provided for each receiving unit between each receiving unit 23A, 23B and the control unit 21.

  Each transmitter 22A, 22B and each receiver 23A, 23B are connected to antenna coils (not shown) in the corresponding antennas 1A, 1B, respectively. Each of the transmission units 22A and 22B includes a modulation circuit, an impedance matching circuit, and the like. These circuits generate a signal obtained by amplitude-modulating the carrier signal from the control unit 21 using a command signal. Output to the antennas 1A and 1B.

The command signal is a pulse signal representing the specific content of the command, and the high level state and the low level state are switched according to the content of the command at the command transmission timing. However, since the time when the command is not transmitted is at a low level, only the carrier signal is transmitted from the transmission units 22A and 22B.
In this embodiment, since the same carrier signal is given to each of the transmitters 22A and 22B, a carrier wave synchronized with the same carrier signal is also transmitted from the antennas 1A and 1B. Therefore, even if the communication areas 4A and 4B of the antennas 1A and 1B overlap as shown in FIG.

  Each receiving unit 23A, 23B includes a detection circuit and a filter circuit (not shown), and these circuits detect a signal component excluding a carrier signal component from signals transmitted from an antenna coil as a received signal. To do. Further, each of the receiving units 23A and 23B includes a sampling circuit that samples the received signal at regular intervals, a comparison circuit that binarizes the sampled signal, and the like. When the response signal from the tag 5 is included in the received signal, the response signal can be decoded by processing of each circuit of the receiving units 23A and 23B.

  The control unit 21 determines whether or not the response signal from the tag 5 is included in the signal based on the change pattern of the reception signal input from each of the reception units 23A and 23B. If a response signal is included, the response data is restored from the signal and transmitted to the host device 3.

The reception signal sampling in each of the reception units 23A and 23B is executed based on the reception clock signal from the control unit 21. When the area expansion type communication shown in FIG. 3 is performed, the control unit 21 obtains the logical sum of the input signals every time the binary reception signals are received from the reception units 23A and 23B. The logical sum of signals received by the units at the same timing can be obtained with high accuracy.
However, this OR operation is not limited to the method performed by the control unit 21, and each received signal may be input to the OR circuit outside the control unit 21, and the output from the OR circuit may be input to the control unit 21.

In addition, in the configuration of FIG. 5, the transmission units 22A and 22B and the reception units 23A and 23B can be provided in the antennas 1A and 1B.
In the above example, the two antennas 1A and 1B are connected to the controller 2, but instead, the controller 2 may function as one antenna. In this case, the controller 2 performs control so that any one of the communication processes of FIGS. 2 to 4 is performed while supplying the carrier signal generated by the own device to the internal antenna coil and the external antenna. .

  In the configuration of FIG. 5, even when only one of the first and second antennas 1A and 1B only needs to transmit a carrier wave (when the tag 5 is activated or a command is transmitted), both antennas 1A and 1A, Although the carrier wave is output at the timing synchronized with 1B, instead of this, the carrier wave may be transmitted only to the antenna that transmits the command during the response reception period.

FIG. 6 shows a flow of processing executed by the controller 2 when the area-limited communication shown in FIG. 2 is performed. In this example, assuming that the tag 5 is carried along the direction of arrow D _A of FIG. 1, showing the flow of processing required for the communication with one tag 5.

  First, in ST101, which is the first step, a command from the host device 3 is received. When the reception is completed, the system waits until the time necessary for starting the tag 5 elapses (ST102), and then proceeds to ST103 to transmit a command to the first antenna 1A.

  When the command transmission is completed, in ST104, reception of received signals from the antennas 1A and 1B and response data restoration processing are started. When this process is executed until a preset reception period elapses, ST105 becomes “YES”. Hereinafter, the success or failure of communication and the location of the tag are determined based on whether or not each antenna 1A, 1B has received a response signal from the tag 5 (specifically, whether or not response data has been restored from each received signal). To do.

  In this example, the antenna 1A that transmitted the command receives the response signal as an essential requirement for successful communication. If the response data cannot be restored from the received signal of the antenna 1A, ST106 becomes “NO”, the process proceeds to ST107, and it is determined that the communication has failed. Such a determination is made when a command is transmitted before the tag 5 enters the communication area 4A of the antenna 1A.

  On the other hand, when the response data can be restored from the received signal of the first antenna 1A, but the response data cannot be restored from the received signal of the second antenna 1B, ST106 is “YES” and ST108 is “ The process proceeds to ST109, where it is determined that the tag 5 is in the region r1.

  If the same response data can be restored from the received signals of both the first antenna 1A and the second antenna 1B, ST106 and 108 are “YES”, the process proceeds to ST110, and it is determined that the tag 5 is in the region r3. .

  As described above, after making a determination based on the reception state of each antenna 1A, 1B, the process proceeds to ST111, and the above determination result is transmitted to the upper device 3 together with the restored response data. However, if it is determined that the communication has failed, only the determination result is transmitted.

  Note that, when a command is transmitted from the second antenna 1B, the control for the antennas 1A and 1B is reversed, but the processing flow is the same as in FIG. In this case, it is an essential requirement for successful communication that the response data can be restored from the received signal of the antenna 1B, and it is determined that the tag 5 is located in either the region r2 or the region r3.

  In the example of FIG. 6, the location of the tag 5 to be communicated is determined, and the determination result is transmitted to the upper device 3 together with the restored response data (whether the communication is valid depends on the upper device 3 Or, the user who uses this will make a decision.) However, the processing content is not limited to this. For example, if only the communication within the region r3 is valid, the response data is transmitted to the host device 3 only when the response data can be restored from the received signals of both the antennas 1A and 1B, and in other cases May transmit information indicating that the communication has failed.

FIG. 7 shows the flow of control when the area expansion type communication shown in FIG. 3 is performed. Also in this example, the tag 5 is carried along the direction of arrow D _A, first antenna 1A is assumed to be set as an antenna for transmitting a command.

  Also in this process, as in the example of FIG. 6, after receiving a command from the higher-level device 3, the command is transmitted after the elapse of time necessary for starting the tag 5 (ST 201 to 203).

  When the transmission of the command is completed, the process proceeds to ST204, and processing for the received signals of the antennas 1A and 1B is started. Here, while receiving the received signals after sampling and binarization processing from the receiving units 23A and 23B, the logical OR operation of the input signal is performed every hour, and the response data is restored from the result of the logical OR operation.

  Thereafter, when the reception period elapses, ST205 becomes “YES”. Here, when the response data can be restored from the result of the logical sum operation, ST206 becomes “YES”, the process proceeds to ST207, and the restored response data is transmitted to the host device 3. On the other hand, if the response data could not be restored, ST206 becomes “NO”, the process proceeds to ST208, and information indicating that the communication has failed is transmitted to the host device 3.

FIG. 8 shows the flow of control when performing the type of communication in which the command shown in FIG. 4 is divided and transmitted. In this example, the tag 5 is carried along the direction of arrow D _A, first antenna 1A is assumed to be initially set as an antenna for transmitting a command.

In this example, it is assumed that the data capacity to be included in one command is determined in advance. The transmission capacity is set in the controller 2 by default, but can be appropriately changed by the user using the setting unit 24.
In this example, it is assumed that the moving speed of the tag 5 is controlled so that the number of tags 5 included in the range specified by the regions r1, r2, and r3 is always one.

  When a command from the host device 3 is received in ST301, which is the first step, in the next ST302, the command is divided into N (N ≧ 2) based on the transmission capacity.

  In the next ST303, an initial value 1 is set in a counter n for counting the number of communication times, waits for the time required for activation of the tag 5 to elapse, and a command (the first one specified by the value of n Command) is transmitted from the first antenna 1A (ST304, 305). When the command transmission is completed, in ST306, reception of received signals from antennas 1A and 1B and response data restoration processing are started (this processing is the same as ST104 in FIG. 6).

  After this, when the reception period elapses, ST307 becomes “YES”. When the first antenna 1A receives the response signal from the tag 5, ST308 also becomes “YES” and the process proceeds to ST309 to temporarily store the data restored from the received signal. Further, the process proceeds from ST310 to ST311, and the value of n is updated to one larger value.

  If the tag 5 at the time of the previous communication is in the region r1, the response data cannot be restored from the received signal of the second antenna 1B, so ST312 becomes “NO” and the process returns to ST304. Therefore, the command (second command) specified by the updated n is also transmitted from the first antenna 1A.

  Hereinafter, every hour command is transmitted from the first antenna 1A until similar response data can be restored from the received signals of the first and second antennas 1A and 1B. In this case, if the command fails to reach the tag 5 due to the occurrence of noise or the communication fails because the response signal from the tag 5 does not reach the first antenna 1A, ST308 becomes “NO”. Return to ST304 without communicating the value of n. Therefore, when communication fails, the same command as the previous one is retransmitted.

When the same response data is received from the reception signals of the first and second antennas 1A and 1B at a predetermined time, ST312 becomes “YES”, and the processing after ST313 is executed.
Also in this case, the n-th command is transmitted from the second antenna 1B after waiting for the time required for starting the tag 5 to elapse. When this command transmission is completed, in ST315, reception of the reception signal of second antenna 1B and response data restoration processing are started.

  After this, when the reception period elapses, ST316 becomes “YES”, and when the second antenna receives a response signal, ST317 becomes “YES”. If these determinations are “YES”, the process proceeds to ST318, and the restored response data is stored.

  Similarly, while sequentially updating the value of n until it reaches N, the command specified by the hourly n is transmitted from the second antenna 1B, and the received signal from the second antenna 1B for that signal is processed. During this time, if the second antenna 1B cannot receive the response signal from the tag 5 due to the influence of noise or the like, the process returns from ST317 to ST313 without updating the value of n. Retransmitted.

  When the value of n finally becomes N, the process proceeds to ST321, where N response data saved by the process of ST309 or ST318 are read and integrated into one data. Furthermore, in ST322, the integrated response data is transmitted to the higher-level device 3 as a final result.

  In the above processing, after the antenna that transmits the command is switched from the first antenna 1A to the second antenna 1B, the received signal of the first antenna 1A is not processed. Even in this case, the signals of both antennas 1A and 1B may be processed. In this case, following the example of FIG. 6, if it is determined in which area the tag is included each time communication is performed, the moving speed of the tag is recognized or the arrangement of the antennas 1A and 1B is adjusted based on the determination result. be able to.

  Further, FIG. 8 shows an example of processing when one command is divided and transmitted in order. However, when a plurality of commands having different contents are transmitted to one tag 5 in order, the same as in FIG. Can be executed.

It is explanatory drawing which shows the structural example of a RFID system. It is explanatory drawing which shows the example of the communication process of an area | region limitation system. It is explanatory drawing which shows the example of the communication process of an area expansion system. It is explanatory drawing which shows the example which communicates several times with the same tag by communication of an area | region expansion system. It is the block diagram which showed the structure of the controller in detail among RFID systems. It is a flowchart which shows the flow of control in the case of performing communication of FIG. It is a flowchart which shows the flow of control in the case of performing communication of FIG. It is a flowchart which shows the flow of control in the case of performing communication of FIG. It is explanatory drawing which shows the example of the conventional communication process using a some antenna.

Explanation of symbols

1A, 1B Antenna 2 Controller 4A, 4B Communication area 21 Control unit

Claims (3)

A device that performs non-contact communication with an RFID tag by controlling a plurality of antennas arranged along the movement path of the RFID tag such that a part of the communication area overlaps a part of another communication area. And
First control means for controlling each of the carriers between the antennas emitting the carriers to be in a synchronized state;
Transmitted every RFID tag communication target, the processing for transmitting a command to the RFID tag to any one of the plurality of antennas, as the first antenna corresponding to a communication area where the RFID tag enters the first command A plurality of times while switching the antennas to be arranged in the order of the arrangement of the antennas, and for transmission of commands from antennas corresponding to each communication area other than the communication area where the RFID tag enters last, Second control means for setting an antenna that has not yet transmitted the adjacent command to a state in which a response signal from the RFID tag can be received by the synchronized carrier wave ;
Signal processing means for decoding a response signal from the RFID tag in response to the command by processing a reception signal of the antenna set in the receivable state each time the command is transmitted ;
In response to the transmission of a command from each antenna except the antenna corresponding to the communication area in which the RFID tag enters last, the second control means responds from the RFID tag to the two antennas that are set in a receivable state. Whether or not a signal has been received is determined based on the result of the decoding process for each received signal. If only the antenna that transmitted the command determines that the response signal has been received, the next command is also transmitted to the antenna. When it is determined that both of the two antennas set in the reception enabled state have received the response signal, the next command is transmitted to the antenna that has not yet transmitted the command of the two antennas. Non-contact communication device characterized by. The second control means puts the antenna other than the antenna that transmits the command into a dormant state and sets the antenna that should be able to receive the response signal from the RFID tag to the carrier wave in response to the command being transmitted. The non-contact communication device according to claim 1 or 2, wherein the non-contact communication device is set to a state of sending . This is a method of performing non-contact communication with an RFID tag by controlling a plurality of antennas arranged along the movement path of the RFID tag so that a part of the communication area overlaps with a part of the other communication area. And
Transmitted every RFID tag communication target, the processing for transmitting a command to the RFID tag to any one of the plurality of antennas, as the first antenna corresponding to a communication area where the RFID tag enters the first command Execute multiple times while switching the antenna to be switched in the order of the antenna array
In response to the transmission of a command from each antenna other than the antenna corresponding to the communication area where the RFID tag enters last, the antenna that has transmitted the command and the antenna that has not transmitted the command next to the antenna are transmitted between these antennas. When the response signal from the RFID tag with respect to the command is received by continuously transmitting the synchronized carrier wave, and only the antenna that transmitted the command of the two antennas receives the response signal When the next command is also transmitted from the antenna and both antennas receive the response signal, the next command is transmitted from the antenna that has not yet transmitted the command of the two antennas,
Noncontact communication method comprising for each of the command is sent, the result to process the received signal of the antenna set to the receivable state, for decoding the response signal from the RFID tag to the command, it .

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