JP2004164220A - Data carrier, reader/writer device, and data carrier system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To cause data constituting the ID of a tag to be transmitted at a time from a plurality of tags existing within a service area and to ensure that a reader/writer device recognizes the plurality of data transmitted at a time from the plurality of tags. <P>SOLUTION: A plurality of bit data which constitutes a characteristic ID are divided into predetermined bits and transmitted. The frequencies of signals responding to the reader/writer device are individually set according to the data contents of the predetermined bits. When a command signal is sent from the reader/writer device, the response signals are sent at a time at the frequencies individually set according to the data contents of the predetermined bits, thus ensuring that within one response period, the reader/writer device is able to recognize the ID transmitted from at least one of the tags. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a data carrier, a reader / writer device, and a data carrier system, and is particularly suitable for performing a multi-read sequence for sequentially reading IDs of a plurality of tags existing in a predetermined service area. .
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a data carrier system used in an environment where a plurality of tags (data carriers) often exist simultaneously in a service area, a multi-read sequence is performed by various methods to call the plurality of tags. I have.
[0003]
For example, in Patent Document 1, a unique ID assigned to each data carrier is sequentially read by a multi-read sequence, and the IDs of the data carriers are read one by one in one sequence. In such a data carrier system, a unit time in a communication operation performed between a reader / writer device and a plurality of tags is expressed as 1 etu (elementary time unit).
[0004]
An example of a conventional multi-read sequence in a data carrier system will be described below.
(First conventional example)
First, the reader / writer device issues a multi-read command signal to a plurality of tags. On the other hand, after a predetermined set time (first set time) elapses, each tag has the least significant one-digit / two-digit data in the bit data constituting the ID assigned to each tag. A reply is returned to the reader / writer device in the designated time slot.
[0005]
When returning a reply to the reader / writer device, two types of time slots are used in the case of one digit, and four types of time slots are used in the case of two digits. In any case, in order to determine the signal level within a specific time slot and determine the reception result, it is important that the two / four types of time slots do not overlap each other. For this reason, a guard time is set between each time slot, or the length of the time slot is set so that the period during which each time slot exists alone is sufficiently long.
[0006]
For this reason, when each tag responds to the command signal sent from the reader / writer device, it is necessary to allow a time margin in consideration of “time variation + variation in response time in the receiving system”. is there. Therefore, conventionally, the standard of the time slot is set to be about 3 etu at the highest speed.
[0007]
On the other hand, in the reader / writer device, an operation of detecting a reply signal from the tag for each time slot is continuously performed until all time slots are completed. When a signal from each tag is detected by the reader / writer device, data corresponding to the detected time slot is designated, and a carry signal for instructing to return the next digit is transmitted to the corresponding tag. To send to.
[0008]
In this case, even if a signal is detected in a plurality of time slots, it is specified to return a reply of the next digit only for any one type of tag. Note that any data may be selected from the detected signals, but in general, priorities are assigned in the order of time slots. However, a random ID may be selected, and management giving priority to a specific ID code is also possible. If the signal from the tag is not detected by the reader / writer device, the carry signal is not sent to the tag, and the current multi-read sequence ends.
[0009]
Next, the operation of each tag will be described. In each tag, the hit tag returns a reply in a time slot corresponding to the data of the next digit after a predetermined set time (second set time = first set time) has elapsed. Also, the tag that has not been hit exits from the multi-read sequence and waits for the next command signal.
[0010]
On the other hand, even if the tag returns a reply signal but the reader / writer device cannot detect a signal in all time slots, the reader / writer device does not return a carry signal. . As described above, the reader / writer device ends the current multi-read sequence. As a result, the tag also exits the multi-read sequence and waits for the next command signal.
[0011]
As a result of repeating such a multi-read sequence, the tag that has returned all digits of the ID code had the reader / writer device read all the ID digits. Stop responding. Therefore, the number of tags responding to the next multi-read command signal is reduced by one.
[0012]
By repeating this communication procedure, the ID of one tag can be read in one multi-read sequence. Therefore, by repeating this multi-read sequence many times, all IDs can be sequentially read even if a large number of tags exist in the service area. Therefore, since the control in each tag can be performed simply by repeating the routine operation, there is an advantage that the manufacturing cost of the tag can be reduced.
[0013]
[Patent Document 1]
JP-A-8-36623
[0014]
[Problems to be solved by the invention]
As described above, in the method of the multi-read sequence in the conventional data carrier system, each tag returns a reply to the reader / writer device in a plurality of time slots. For this reason, the reader / writer device needs to determine the presence or absence of a received signal during a specific time slot. Therefore, as described above, each time slot is set so that replies from a plurality of tags do not completely overlap. Had to be set.
[0015]
Further, each tag operates in synchronization with a command signal sent from the reader / writer device, but there is a problem that there is a response shift between the tags. Further, there is a problem that the time required for the reader / writer device to determine the presence / absence of a signal from the tag also varies depending on the signal level.
[0016]
That is, since the signal from the tag closest to the reader / writer device is strongly transmitted to the reader / writer device, the time from when each tag starts returning a reply to when the reader / writer device determines that there is a signal is earlier, Conversely, there is a problem in that the time for determining that there is no signal after answering is delayed becomes longer.
[0017]
On the other hand, the response of a tag located at a position close to the limit of the service area of the reader / writer device (a position far from the reader / writer device) is delayed because the signal transmitted to the reader / writer device is weak. However, the time required for the reader / writer device to determine that there is a signal is slow, and conversely, the time required for the reader / writer device to determine if there is no signal after the reply is stopped becomes short.
[0018]
For this reason, it is necessary to insert a guard time between time slots or to extend each time slot in order to prevent the replies of the respective tags from overlapping. Therefore, the conventional method has a problem in that the multi-read sequence takes a long time.
[0019]
The present invention has been made in view of the above-described problems, and allows data constituting a tag ID to be transmitted simultaneously from a plurality of tags existing in a service area, and simultaneously transmits data from the plurality of tags. An object of the present invention is to make it possible for a reader / writer device to reliably recognize a plurality of transmitted data.
[0020]
[Means for Solving the Problems]
The data carrier of the present invention is a data carrier to which a unique ID composed of a plurality of bit data is assigned, and which transmits the unique ID in response to a command signal sent from a reader / writer device. A plurality of bit data are transmitted by being divided for each predetermined bit, and the frequency of a signal responding to the reader / writer device is individually set according to the data content of the predetermined bit. When a command signal is transmitted from the / writer device, response signals at frequencies individually set in accordance with the data content of the predetermined bits are simultaneously transmitted.
Another feature of the present invention is that a plurality of bit data constituting the unique ID is divided into two bits and individually set according to the four types of data contents represented by the two bits. A response is made to the reader / writer device using any of the four types of response signals at the four frequencies.
[0021]
A reader / writer device according to the present invention is a reader / writer device configured to sequentially read IDs transmitted from the data carriers described above to perform a multi-read sequence, and transmit the IDs from the plurality of data carriers. Detecting the presence or absence of a signal for each frequency of the response signal to be transmitted, and recognizing at least one of the response signals within one response period with respect to the response signals transmitted simultaneously from the plurality of data carriers. It is characterized by.
[0022]
A data carrier system according to the present invention uses the data carrier described above and the reader / writer device described above.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of a data carrier, a reader / writer device, and a data carrier system of the present invention will be described with reference to the drawings.
(First Embodiment)
According to the present embodiment, in the multi-read sequence, replies are made simultaneously at different subcarrier frequencies according to the bit data constituting the ID number of each tag.
[0024]
FIG. 1 is a block diagram illustrating a configuration example of a tag according to the first embodiment.
When the tag (data carrier) 100 of the present embodiment receives the multi-read command signal sent from the reader / writer device by the antenna 101, the band-pass filter 102 cuts off unnecessary band signals, and the amplifier 103 And supplies it to the control circuit 104.
[0025]
The control circuit 104 reads one bit out of the bit data constituting the ID stored in the ID storage circuit 105 according to the input multi-read command signal, and derives it to the pattern generation circuit 106. The pattern generation circuit 106 generates a sub-carrier of a predetermined frequency according to the content of the bit data read from the ID storage circuit 105.
[0026]
The pattern generation circuit 106 according to the present embodiment has a first subcarrier generation circuit 106a and a second subcarrier generation circuit 106b, and generates a first subcarrier signal for a carrier frequency S of 125 kHz. A subcarrier signal of either S1 or the second subcarrier signal S2 is generated.
[0027]
The first subcarrier signal S1 is generated by modulating a carrier at a signal period of 41.667 KHz obtained by dividing the carrier frequency S25 KHz by 3 and is 83.333 KHz.
[0028]
The second subcarrier signal S2 is generated by modulating a carrier at a signal period of 25 KHz obtained by dividing the carrier frequency S (125 KHz) by 5 and is 100 KHz.
[0029]
The subcarrier signal S1 or S2 generated as described above is supplied from the pattern generation circuit 106 to the output amplifier 107, amplified to a predetermined level, and transmitted to the reader / writer device via the antenna 101.
[0030]
Next, a configuration example of the reader / writer device according to the present embodiment will be described with reference to FIG.
In FIG. 2, 201 to 20n indicate tags existing in the service area. 210 is a reader / writer device main body, 211 is an antenna, 212a is a first bandpass filter, 213a is a first amplifier, 214a is a first detection circuit, 212b is a second bandpass filter, 213b Denotes a second amplifier, and 214b denotes a second detection circuit. 215 is a controller, and 216 is an output amplifier.
[0031]
With such a configuration, when a command signal is transmitted from the reader / writer device from the antenna 211, the sub-carrier signal individually set according to the content of the data constituting the ID from each of the tags 201 to 20n. Are sent all at once.
[0032]
The subcarrier signals transmitted simultaneously from the tags 201 to 20n are input to the amplifiers 213a and 213b and then amplified after unnecessary frequency bands are removed by the band-pass filters 212a and 212b. The sub-carrier signals are detected by the circuits 214a and 214b, and the detection result of the detected sub-carrier signals (or the determination result of the presence or absence of the sub-carrier signals) is input to the controller 215.
[0033]
The controller 215 includes a computer system including a CPU, a RAM, a ROM, and the like. The controller 215 transmits a command signal for performing a multi-read sequence to each of the tags 201 to 20n, and transmits an ID transmitted from each of the tags 201 to 20n. Or the like, based on the subcarrier signal individually set in accordance with the data content constituting the ID, the ID bit transmitted from at least one of the tags is recognized.
The command signal output from the controller 215 is amplified by the output amplifier 216 and transmitted to each of the tags 201 to 20n via the antenna 211.
[0034]
Next, the operation of the data carrier system including the tag and the reader / writer device configured as described above will be specifically described.
When a multi-read command signal is issued from the reader / writer device, the tag returns a reply signal for a predetermined time after a set time. The signal to be returned is a continuous wave for a fixed time at the subcarrier frequency S, or a phase modulated wave whose phase is changed at random every set period within the fixed time.
[0035]
As described above, the reason for applying the phase modulation randomly is that if a plurality of tags 201 to 20n return a reply at the same frequency at the same time, they may cancel each other's signals at a low probability. In such a case, the purpose is to avoid the inconvenience that the signal cannot be detected by the reader / writer device.
[0036]
In the present embodiment, since the phase reply is randomly applied to the reply signal of the tag as described above, even if the signals may cancel each other, the phase changes randomly, so that the This is because the probability that the signals cancel each other is further reduced, so that the probability of detecting the signal can be increased.
[0037]
The reply subcarrier frequency is determined by the data of the first digit of the tag ID. For example, for "0", 100 KHz is set as the first subcarrier signal S1, and for "1", 83.333 KHz is set as the second subcarrier signal S2.
[0038]
Therefore, if the ID of a certain tag is "11100100", the least significant bit is "0", so that a reply is returned for a certain period of time at the second subcarrier frequency S2 of 100 KHz.
[0039]
At this time, the reader / writer device detects both subcarrier signals because both subcarrier signals may be returned from the tag. That is, the first sub-carrier signal S1 (signal having a frequency of 100 KHz) is detected by the first band-pass filter 212a, the first amplifier 213a, and the first detection circuit 214a, and the second band-pass filter 212b, The second amplifier 213b and the second detection circuit 214b detect the second subcarrier signal S2 (a signal having a frequency of 83.333 KHz) to determine the presence or absence of a signal from the tag.
[0040]
When a subcarrier signal from the tag is detected, the detected data is specified, that is, a carry signal is sent to the tag that has received the reply so that the reply is returned by the next digit ID data. At this time, if both subcarrier signals S1 and S2 are detected, one of the data is designated, that is, by transmitting the ID data of the next digit to the tag which receives the reply with priority. Send a carry signal to reply.
[0041]
The method of selecting a tag that returns a change in priority may be determined in accordance with the priority order according to data. For example, if both “0” and “1” are detected, “0” is prioritized. You may leave. In addition, a reply may be returned at random. Alternatively, priority may be given to a signal having a higher signal level from the tag, or the data pattern of the ID to be read with priority may be set.
[0042]
In the tag that has been hit in the multi-read according to the present embodiment, that is, among the tags that have responded in response to a command from the reader / writer device, the data returned from the reader / writer device has been confirmed, and carry is instructed. The tag that has received the signal returns a reply in the same manner with the data of the next digit in the bit data constituting the ID.
[0043]
On the other hand, among the tags that did not hit, that is, the tags that received a command from the reader / writer device and returned data that differed from the data returned from the reader / writer device, and instructed carry-over. The tag that has received the signal to perform the operation exits the multi-read sequence and waits for the next command.
[0044]
Even if the multi-read command signal is sent from the reader / writer device, if the reply signal to the multi-read command signal is not transmitted from the tag, the reader / writer device performs the multi-read sequence without outputting a signal for instructing data confirmation and carry. finish.
[0045]
Even if the tag responds at this time, if the signal indicating that the returned data has been confirmed and the signal indicating the carry do not come from the reader / writer device, the tag also exits the multi-read sequence. Wait for the next command.
[0046]
In this example, since the ID of the tag is “11100100”, the lowest order of the ID of the tag is “0” in response to the multi-read command signal from the reader / writer device. A reply was returned for a certain time at the subcarrier frequency of 100 KHz which is S1.
[0047]
As a result of the tag returning the first subcarrier signal S1, the reader / writer device detects a 100KHz subcarrier signal. In this case, the reader / writer device detects that a signal of data “0” has been detected and sends a carry signal to each of the tags 201 to 20n.
[0048]
Each of the tags 201 to 20n receives the reply data transmitted by the reader / writer device and transmits a carry signal from the reader / writer device. A reply signal is returned during. In this case, since the second digit from the bottom of the bit data forming the ID is “0”, a reply is returned at the subcarrier frequency of 100 KHz which is the first subcarrier signal.
[0049]
Hereinafter, the tag and the reader / writer device communicate in the same manner. When the digit data for returning the bit data constituting the ID is "1", the reply is returned at the subcarrier frequency of 83.333 KHz, which is the second subcarrier signal.
[0050]
Thus, the multi-read sequence proceeds, and the ID of one tag is read out to the reader / writer device by one multi-read sequence. The tag from which all digits of the bit data constituting the ID have been read in the multi-read sequence is stored in an internal memory (not shown) so that the tag does not participate in the subsequent multi-read sequence. I do.
[0051]
Therefore, while the multi-read sequence is repeatedly performed, the IDs of the tags existing in the service area of the reader / writer device are all read out by the reader / writer device. In this case, there is no replying tag, and the multi-read sequence ends.
[0052]
The feature of the present embodiment is that after receiving a multi-read command signal or a carry signal, the tags that respond are all responding at once. Therefore, it is possible to read out the multi-read sequence faster than in the conventional example in which the response timing is changed according to the data of each digit of the bit data constituting the ID.
[0053]
Moreover, it is possible to prevent the reading speed from being changed by the contents of the ID. Also, in the control operation in the tag, after receiving a multi-read command signal or a carry signal from the reader / writer device, if a response is returned, the carrier frequency S is determined by the ID data of the corresponding digit at a predetermined timing if a response is returned. Since it is sufficient to repeat a simple operation of returning a reply by load modulation with different frequency-divided signals created from the above, the cost of the tag can be reduced.
[0054]
Since the reader / writer device requires a receiving circuit for detecting a plurality of subcarrier signals, the cost of the reader / writer device is slightly higher. However, when using a large number of tags, the cost of the tag is lower. Since the cost is more important than the cost of the reader / writer device, the cost reduction effect can be obtained as a whole.
[0055]
The first subcarrier signal S1 or the second subcarrier signal S2 generated by the pattern generation circuit 106 is amplified by the output amplifier 107 and transmitted to the reader / writer device via the antenna 101.
[0056]
In the present embodiment, the time required for one multi-read sequence is returned one digit at a time. Therefore, if the ID has 16 digits,
Command issue time: Netu,
First setting period: 2 etu,
Response period: 2 etu,
Second setting period: 2 etu,
Issue carry signal by specifying data: 2 etu,
Then,
Netu + 8 etu × 16 = Netu + 128 etu
It becomes.
[0057]
As described above, since the operation sequence of the tag 100 of the present embodiment is simple, a logic circuit built in the control circuit 104 can be easily configured, and the manufacturing cost of the tag 100 can be reduced in the case of an integrated circuit. it can. This provides an advantage that the overall cost can be reduced in a data carrier system having a large number of tags 100.
[0058]
(Second embodiment)
Next, a second embodiment of the present invention will be described.
Also in the present embodiment, in the multi-read sequence, replies are simultaneously made at different subcarrier frequencies by the bit data constituting the ID number of each tag.
[0059]
FIG. 3 shows a configuration example of the tag. When the tag 300 of the present embodiment receives the multi-read command signal sent from the reader / writer device by the antenna 301, the band-pass filter 302 cuts off unnecessary band signals, and the amplifier 303 amplifies the signal to a predetermined level. And supplies it to the control circuit 304.
[0060]
The control circuit 304 reads out two bits from the bit data constituting the ID stored in the ID storage circuit 305 in accordance with the input multi-read command signal, and derives it to the pattern generation circuit 306. The pattern generation circuit 306 generates a subcarrier of a predetermined frequency according to the content of the bit data read from the ID storage circuit 305.
[0061]
The pattern generation circuit 306 of this embodiment includes a first subcarrier generation circuit 306a, a second subcarrier generation circuit 306b, a third subcarrier generation circuit 306c, and a fourth subcarrier generation circuit 306d. , And four subcarrier frequencies S1 to S4 are set for a carrier frequency S of 125 KHz.
[0062]
The first subcarrier frequency S1 is 62.5 KHz, which is generated by modulating the carry signal S with a signal period of 62.5 KHz obtained by dividing 125 KHz by 2 by the first subcarrier generation circuit 306a.
The second subcarrier frequency S2 is 83.333 KHz, which is generated by modulating the carry signal S by a second subcarrier generation circuit 306b at a signal period of 41.667 KHz obtained by dividing 125 KHz by 3.
The third subcarrier frequency S3 is 93.75 KHz, which is generated by modulating the carry signal S with a signal period of 31.25 KHz obtained by dividing 125 KHz by 4 by the third subcarrier generation circuit 306c.
The fourth subcarrier frequency S4 is 100 KHz, which is generated by modulating the carry signal S by a fourth subcarrier generation circuit 306d at a signal period of 25 KHz obtained by dividing 125 KHz by 5.
[0063]
When the carrier signal S is modulated at a signal cycle of 31.25 KHz obtained by dividing the carrier frequency S (125 KHz) by 4 as a subcarrier and a subcarrier of 93.75 KHz is output, a subcarrier of 62.5 KHz which is minute is obtained. Carrier components may also appear. This is because the waveform of 31.25 KHz obtained by dividing the frequency of 125 KHz of the carry signal S by 4 is basically a square wave, and is a waveform having many odd-order harmonic components but no even-order harmonic components. However, in reality, there are jitters and the like, and even-order harmonics are present, albeit a little. This is not a problem
[0064]
In this case, because the subcarrier of 93.75 KHz is much stronger, the subcarrier of this frequency can be preferentially detected. Therefore, when receiving a reply from the tag and sending a carry signal, if giving priority to sending a reply at 93.75 KHz over sending a reply at 62.5 KHz, 62 This is because when detecting a signal of .5 KHz, since the ID has already been returned, there is no tag that returns at 93.75 KHz at the same time.
[0065]
The subcarrier signals S1 to S4 generated as described above are supplied from the pattern generation circuit 306 to the output amplifier 307, amplified to a predetermined level, and transmitted to the reader / writer device via the antenna 301.
[0066]
Next, a schematic configuration of the reader / writer device of the present embodiment will be described with reference to FIG.
In FIG. 4, reference numerals 401 to 40n indicate tags. Reference numeral 410 denotes a main body of the reader / writer device, 411 denotes an antenna, 412a denotes a first bandpass filter, 413a denotes a first amplifier, and 414a denotes a first detection circuit. 412b is a second bandpass filter, 413b is a second amplifier, and 414b is a second detection circuit.
[0067]
412c is a third bandpass filter, 413c is a third amplifier, and 414c is a third detection circuit. 412d is a fourth bandpass filter, 413d is a fourth amplifier, 414d is a fourth detection circuit, 415 is a controller, and 416 is an output amplifier.
[0068]
With such a configuration, when a command signal is transmitted from the reader / writer device from the antenna 411, the tags 401 to 40n correspondingly transmit the subcarriers individually set according to the contents of the bit data constituting the ID. The signals are transmitted all at once.
[0069]
Each subcarrier signal transmitted simultaneously from each of the tags 401 to 40n is received by the antenna 411 and supplied to the first band-pass filter 412a to the fourth band 412d. Then, after unnecessary frequency bands are removed by the first to fourth bandpass filters 412a to 412d, the signals are input to the first to fourth amplifiers 413a to 413d and amplified.
[0070]
Next, the signals are detected by the first to fourth detection circuits 414a to 414d, and the first to fourth subcarrier signals S1 to S4 are detected and input to the controller 415.
[0071]
The controller 415 is configured by a computer system including a CPU, a RAM, a ROM, and the like, transmits a command signal for performing a multi-read sequence to each of the tags 401 to 40n, and transmits an ID transmitted from each of the tags 401 to 40n. The bit data of the ID transmitted from at least one of the tags is recognized based on the subcarrier signal individually set in accordance with the content of the bit data constituting.
[0072]
The command signal output from the controller 415 is amplified by the output amplifier 416 and transmitted to the tags 401 to 40n via the antenna 411.
[0073]
Next, the operation of the data carrier system including the tag and the reader / writer device configured as described above will be specifically described.
First, a multi-read command signal is issued from the reader / writer device. When the multi-read command signal is issued, the tags 401 to 40n return a reply subcarrier signal for a fixed time after a set time.
[0074]
The subcarrier signal returned from the tags 401 to 40n to the reader / writer device is a continuous wave having a constant frequency in time, or a phase modulated wave in which the phase is randomly changed within a fixed time for each set period.
[0075]
The reply subcarrier frequency is determined by the first two digits of the bit data constituting the tag ID. For example,
100 kHz for "00",
93.75 KHz for "01",
83.333 KHz for "10",
62.5KHz for "11"
And
[0076]
Therefore, if the ID of a certain tag is "11100100", since the two least significant digits are "00", a reply is returned at a subcarrier frequency of 100 KHz for a certain period of time.
[0077]
At this time, the reader / writer device detects four types of subcarrier signals S1 to S4 to which signals from the tags 401 to 40n may return, and determines the presence or absence of the signal. When a subcarrier signal is detected, the reply is returned by designating the detected bit data, that is, transmitting the next two-digit ID data to the tag that has received the reply. A carry signal for
[0078]
At this time, if a subcarrier signal transmitted from a plurality of tags is detected, any one of the data is specified. That is, a carry signal for returning a reply by transmitting the next two-digit ID data to a tag that receives a reply is transmitted.
[0079]
A method of selecting a tag to which a reply is returned may be determined in a priority order according to bit data constituting the ID, or may be random. Alternatively, priority may be given to a signal having a higher signal level from the tag, or a data pattern of an ID to be read with priority may be set.
[0080]
Among the tags that responded in response to the command from the reader / writer device, the tag that confirmed the data returned from the reader / writer device and that received the signal instructing the carry carry the bit data of the ID. The reply is returned by transmitting the next two-digit data.
[0081]
Then, it was confirmed that, among the tags that responded by receiving the command from the reader / writer device and transmitting the next two-digit data, data different from the returned data was transmitted from the reader / writer device. The tag exits the multi-read sequence and waits for the next command.
[0082]
On the other hand, if the signal from the tag is not detected by the reader / writer device after transmitting the multi-read command signal from the reader / writer device, the reader / writer device does not output a signal for instructing data confirmation and carry. , The multi-read sequence ends.
[0083]
At this time, even if the tag responds, if the signal indicating that the returned data has been confirmed and carry is not received from the reader / writer device, the tag also exits the multi-read sequence and waits for the next command. Become.
[0084]
In this example, since the ID of the tag is “11100100”, the lowest two digits of the ID of the tag transmitted upon receiving the multi-read command signal from the reader / writer device are “00”. Therefore, a reply is returned from the tag at a subcarrier frequency of 100 KHz for a certain period of time.
[0085]
Upon detecting the subcarrier signal of 100 KHz, the reader / writer device transmits the detection of the signal of data “00” and the carry signal to the tag.
The tag, when the data transmitted as a reply is confirmed by the reader / writer device and receives a carry signal indicating that, waits for a predetermined set time, and then returns a reply signal within a predetermined time. .
[0086]
The reply signal to be returned next is returned at the subcarrier frequency of 93.75 KHz since the fourth and third digits from the bottom of the bit data constituting the ID are “01”. Hereinafter, communication is similarly performed between the tag and the reader / writer device. As described above, the multi-read sequence proceeds by two digits, and the ID of one tag is read in one multi-read sequence.
[0087]
The tag from which all digits of the ID have been read in the multi-read sequence is stored in an internal memory (not shown) so as not to participate in the subsequent multi-read sequence. Therefore, while the above-described multi-read sequence is repeatedly performed, all the IDs of the tags existing in the service area of the reader / writer device are read out, and there is no replying tag at the end, so the multi-read sequence ends. You can finish safely.
[0088]
As described above, also in the present embodiment, when receiving a response after receiving a multi-read command signal or a carry signal, all the tags return a response all at once. Therefore, it is possible to read out the multi-read sequence earlier than in the conventional example in which the response timing is changed according to each two-digit data of the bit data constituting the ID. Moreover, it is possible to prevent the reading speed from being changed by the contents of the ID.
[0089]
In addition, the control operation in the tag is also a condition for returning a response after receiving a multi-read command signal or a carry signal from the reader / writer device. A simple operation of returning a reply by load modulation with different frequency-divided signals generated from the carrier frequency S according to the data may be repeated. Therefore, the cost of the tag can be reduced.
[0090]
Note that the reader / writer device requires a receiving circuit for detecting a plurality of subcarrier signals, so the cost is high in this respect. However, when a large number of tags are used, the cost of the tag is reduced by the reader / writer. Since it is more important than the cost of the device, the effect of cost reduction can be obtained for the entire data carrier system.
[0091]
The time required for one multi-read sequence in the present embodiment is a case where two digits are returned, and when the number of digits of the bit data constituting the ID is 16,
Command issue time: Netu,
First setting period: 2 etu,
Response period: 2 etu,
Second setting period: 2 etu,
Issue carry signal by specifying data: 3 etu
It is. Therefore,
Netu + 9 etu × 8 = Netu + 72 etu
It becomes.
[0092]
(Third embodiment)
Next, a third embodiment of the present invention will be described.
In the present embodiment, in the multi-read sequence, the carrier signal S is directly modulated at a predetermined frequency determined by the bit data constituting the ID number of each tag, and the responses are simultaneously made.
[0093]
FIG. 5 shows a configuration example of a tag 500 according to the present embodiment.
When the tag 500 according to the present embodiment receives the multi-read command signal sent from the reader / writer device by the antenna 501, the band-pass filter 502 cuts an unnecessary band signal, and then the amplifier 503 amplifies the signal to a predetermined level. And supplies it to the control circuit 504.
[0094]
The control circuit 504 reads out two bits of the bit data constituting the ID stored in the ID storage circuit 505 in accordance with the input multi-read command signal, and derives it to the pattern generation circuit 506. The pattern generation circuit 506 generates subcarriers of a predetermined frequency according to the contents of the bit data read from the ID storage circuit 505.
[0095]
The pattern generation circuit 506 of this embodiment includes a first modulation circuit 506a, a second modulation circuit 506b, a third modulation circuit 506c, and a fourth modulation circuit 506d. With respect to the frequency S, the carrier frequency S is modulated by four frequencies f1 to f4.
[0096]
More specifically, four modulation frequencies are set for a carrier frequency signal S of 125 KHz. That is,
5 KHz is set as the first modulation frequency, 6.578947 KHz is set as the second modulation frequency, 8.333333 KHz is set as the third modulation frequency, and 10.4166 KHz is set as the fourth modulation frequency.
[0097]
The first modulation frequency 5 KHz is a frequency obtained by dividing the carrier frequency S = 125 KHz by 25.
The second modulation frequency 6.578947 KHz is a frequency obtained by dividing the carrier frequency S = 125 KHz by 19.
The third modulation frequency 8.333333 KHz is a frequency obtained by dividing the carrier frequency S = 125 KHz by 15.
10.4166 KHz is a frequency obtained by dividing the carrier frequency S = 125 KHz by 12.
[0098]
As described above, the reason for dividing the carrier frequency S is that it is desired to use a square wave as a modulation signal. This is because it is desired to use the carrier frequency signal S as it is divided and extracted by the logic circuit. Therefore, in the present embodiment, since there are many odd-order harmonics, signals close to odd multiples are not used in the combination of the four frequencies.
[0099]
In addition, when the reader / writer device separates and detects a received signal by a filter, the larger the frequency ratio, the lower the cost of the filter and the more stable the characteristics. It is. Further, since the frequency is low, the active filter having a high Q can be stably and inexpensively configured. Note that lowering the frequency is advantageous in S / N because the receiving band may be narrower, but the reading speed becomes slower, so that it is determined by the balance.
[0100]
Next, a schematic configuration of the reader / writer device of the present embodiment will be described with reference to FIG.
In FIG. 6, reference numerals 601 to 60n denote tags. In addition, 610 is a reader / writer device main body, 611 is an antenna, 612 is a band pass filter, 613 is an amplifier, 614 is a detection circuit, and 615 is a controller.
[0101]
Reference numeral 621 denotes a first frequency detection circuit that detects the first modulation signal f1. Reference numeral 622 denotes a second frequency detection circuit that detects the second modulation signal f2. Reference numeral 623 denotes a third frequency detection circuit that detects the third modulation signal f3. Reference numeral 624 denotes a fourth frequency detection circuit, which detects the fourth modulation signal f4.
[0102]
Next, the operation of the data carrier system according to the present embodiment based on the above configuration will be described.
When a multi-read command signal is issued from the reader / writer device, each of the tags 601 to 60n modulates a carrier at a predetermined frequency for a predetermined time after a predetermined time, and returns a reply signal.
[0103]
In the present embodiment, by lowering the modulation frequency, the phase difference between the signals of the same data is reduced so that the signals transmitted from the tags 601 to 60n do not cancel each other.
[0104]
The modulation frequency of the reply from each of the tags 601 to 60n is determined by the first two digits of the bit data constituting the ID of each tag. For example, for bit data
5 kHz for "00",
6.578947 ... KHz for "01",
8.333333 ... KHz for "10",
10.4166 ... KHz for "11"
Allocated as.
[0105]
For example, if the bit data forming the ID of a certain tag is "11100100", the two least significant digits are "00", so that the tag returns a reply at a frequency of 5 KHz for a certain period of time. .
[0106]
At this time, the controller 615 of the reader / writer device detects signals of four kinds of frequencies from which a signal from the tag may be returned by the first frequency detection circuit 621 to the fourth frequency detection circuit 624, and Is determined.
[0107]
If the signal transmitted from the tag is detected by the controller 615, the reader / writer device specifies the detected data, that is, the next two digits of the tag to which the reader / writer device has received a reply. A carry signal for returning a reply by transmitting the ID data is sent.
[0108]
At this time, when the reader / writer device detects a plurality of frequency signals, the response is performed by designating any one of the data, that is, transmitting the next two-digit ID data to the tag that receives the response. Send a carry signal to return.
[0109]
A method of selecting a tag to specify a reply may be determined in a priority order according to data, or may be specified at random. Alternatively, the one with the higher signal level from the tag may be preferentially designated. Alternatively, the data pattern of the ID to be read with priority may be preferentially designated.
[0110]
Among the tags that responded in response to the command from the reader / writer device, the tag that received the signal indicating that the returned data was confirmed and carry from the reader / writer device was the next in the bit data constituting the ID. The two-digit data is sent and a reply is returned.
[0111]
Among the tags that have returned a response in response to a command from the reader / writer device, the tag transmitted from the reader / writer device that has confirmed data different from the returned data is excluded from the multi-read sequence and the next command is returned. I will wait.
[0112]
Also, even if the multi-read command signal is sent from the reader / writer device, if the signal from the tag is not detected by the reader / writer device, the reader / writer device does not output a signal for instructing data confirmation and carry, without outputting the signal. End the multi-read sequence.
[0113]
At this time, even if the tag responds, even if the tag confirms the returned data and the signal indicating the carry does not come from the reader / writer device, the process exits the multi-read sequence and waits for the next command. Become.
[0114]
In this example, since the tag ID is "11100100", when the multi-read command signal is received from the reader / writer device, the two least significant digits of the tag ID are "00". Therefore, a response was returned after transmitting a frequency of 5 KHz for a certain period of time.
[0115]
As a result, the reader / writer device detects the signal of 5 KHz transmitted from the tag, so that the signal of data "00" is detected and the carry signal is transmitted to the tag.
[0116]
Among the tags that have transmitted the data "00" signal, the data of the reply to the multi-read command signal transmitted from the reader / writer device is confirmed by the reader / writer device, and the carry transmitted from the reader / writer device. The tag that has received the signal transmits the next two-digit bit data within a predetermined time after waiting a set time, and returns a reply signal. In this case, the next two digits from the second digit from the bottom are “01”, so that a reply is returned at the frequency of 6.578947 KHz assigned to the data of “01”. Hereinafter, communication with the reader / writer device is similarly performed.
[0117]
In this manner, the multi-read sequence proceeds by two digits, and the ID of one tag is read in one multi-read sequence. The tag from which all the IDs have been read in the multi-read sequence is stored in an internally provided memory so that it does not participate in the subsequent multi-read sequence.
[0118]
Therefore, while the multi-read sequence is repeated a plurality of times, all the IDs of the tags existing in the service area of the reader / writer device are read. In such a state, there is no tag to reply to, and the multi-read sequence ends.
[0119]
In the present embodiment, after receiving a multi-read command signal or a carry signal, the replying tags return all at once. Therefore, it is possible to read out the multi-read sequence faster than in the conventional example in which the response timing is changed according to each two-digit data constituting the ID. Moreover, there is an advantage that the reading speed does not change depending on the contents of the ID.
[0120]
Also, since the control operation in the tag is a condition for returning a response after receiving a multi-read command signal or a carry signal from the reader / writer device, the ID data of the corresponding digit is set at a predetermined timing. A simple operation of returning a reply by load modulation with different frequency-divided signals created from the carrier frequency S may be repeated. Therefore, an advantage that the cost of the tag can be reduced can be obtained.
[0121]
Since the reader / writer device needs to detect a plurality of frequency signals, the receiving circuit needs a filter and a detection circuit corresponding to each frequency. Therefore, the cost is high in the reader / writer device, but in the case of a data carrier system using a large number of tags, the cost of the tag is more important than the cost of the reader / writer device, so that the cost of the entire system is also low. A great effect can be obtained.
[0122]
Next, in the present embodiment, a second calculation example of the time required for one multi-read sequence will be described. In this calculation example, two digits are returned at a time, and the number of digits of the ID is sixteen.
Command issue time: Netu,
First setting period: 2 etu,
Response period: 8 etu,
Second setting period: 2 etu,
Issue carry signal by specifying data: 3 etu,
It is. Therefore
Netu + 15 etu × 8 = Netu + 120 etu
It becomes.
[0123]
【The invention's effect】
As described above, according to the present invention, since the reading time does not change depending on the contents of the ID of the data carrier, the processing time can be determined by the number of tags. In addition, since it is almost impossible that all the tags constituting the multi-read sequence exist in the service area at the same time, the read time of the multi-read sequence can be shortened.
[0124]
According to another feature of the present invention, a carry signal is sent to a tag of data to be prioritized from data recognized by a reply from the data carrier, so that an ID to be read out quickly is prioritized. Can be recognized.
Further, according to another feature of the present invention, the operation sequence of the data carrier is simplified, so that the configuration of the logic circuit built in the data carrier chip can be simplified. This makes it possible to reduce the cost of the data carrier when integrating the data carrier into an integrated circuit, and it is possible to greatly reduce the overall cost of a normal data carrier system having a large number of data carriers.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an embodiment of the present invention and illustrating a configuration example of a tag according to a first embodiment;
FIG. 2 is a block diagram illustrating a configuration example of a reader / writer device according to the first embodiment.
FIG. 3 is a block diagram illustrating a configuration example of a tag according to a second embodiment.
FIG. 4 is a block diagram illustrating a configuration example of a tag according to a second embodiment.
FIG. 5 is a block diagram illustrating a configuration example of a tag according to a third embodiment.
FIG. 6 is a block diagram illustrating a configuration example of a tag according to a third embodiment.
[Explanation of symbols]
100 tags
101 antenna
102 Band Pass Filter
103 amplifier
104 control circuit
105 ID storage circuit
106 pattern generation circuit
106a First subcarrier generation circuit
106b Second subcarrier generation circuit
201-20n tag
210 Reader / Writer Main Unit
211 antenna
212a first bandpass filter
212b Second bandpass filter
213a First amplifier
213b Second amplifier
214a first detection circuit
214b second detection circuit
215 Controller
216 output amplifier

Claims (4)

A data carrier to which a unique ID composed of a plurality of bit data is assigned, and which transmits the unique ID in response to a command signal sent from a reader / writer device,
The plurality of bit data is divided and transmitted for each predetermined bit, and the frequency of a signal responding to the reader / writer device is individually set according to the data content of the predetermined bit. A data carrier, characterized in that when a command signal is transmitted from a reader / writer device, response signals at frequencies set individually according to the data content of the predetermined bits are simultaneously transmitted. The plurality of bit data constituting the unique ID is divided into two bits, and any one of four types of response signals with four frequencies individually set according to the four types of data contents represented by the two bits 2. The data carrier according to claim 1, wherein the data carrier responds to the reader / writer device by using the data. 3. A reader / writer device configured to sequentially read IDs transmitted from the data carrier according to claim 1 or 2 and perform a multi-read sequence,
The presence or absence of a signal is detected for each frequency of the response signal transmitted from each of the plurality of data carriers, and at least one of the response signals transmitted simultaneously from the plurality of data carriers is subjected to one response period. A reader / writer device characterized in that the reader / writer is recognized inside. A data carrier system using the data carrier according to claim 1 or 2 and the reader / writer device according to claim 3.

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