JP3983615B2 - BPSK signal recognition method and non-contact IC card terminal using the recognition method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention recognizes each IC chip at the time of data communication realized between a plurality of IC chips and a read / write terminal using a signal phase-modulated by a BPSK (Binary Phase Shift Keying) method. The present invention relates to a contactless IC card terminal device using the method for recognizing and the recognition method thereof.
[0002]
[Prior art]
It has been conventionally performed to read information of an embedded article or a person carrying the IC chip by embedding an IC chip in various objects and performing contactless communication. In particular, the IC chip is embedded in a card and already put into practical use as a commuter pass. In such IC card field, ISO / IEC-14443 defines a communication method using BPSK modulation as a method for communicating data to a read / write terminal (hereinafter referred to as a reader / writer device) in a non-contact manner. ing. An IC card referred to as a combination type that can be read / written by reading the IC card into a reader / writer device by bringing the IC card into contact with the terminal and wirelessly performing the writing / reading without contact. However, BPSK modulation is used for the non-contact communication.
[0003]
The BPSK modulation is to modulate the carrier wave transmitted from the reader / writer device depending on whether or not the IC card applies a load of the subcarrier wave. Data is demodulated by detecting the point of phase change. In the ISO / IEC-14443, a carrier wave with a frequency of 13.56 MHz is load-modulated with a subcarrier wave with a frequency of 847 kHz.
[0004]
In the IC card system configured as described above, for example, a system in which one card is used for personal authentication and another card is used for starting an application in the card is sent from the reader / writer device. There may be a plurality of IC cards 1 within the reach of electromagnetic waves. In that case, there is a risk of collision of signals when the plurality of IC cards are activated and start exchanging signals such as initial responses. For this reason, the ISO / IEC-14443, which is an international standard for IC cards, has standardized the initial response and collision prevention procedures as ISO / IEC-14443-3.
[0005]
According to the standard, the reader / writer device normally transmits a data string for initial response when checking whether an IC card is present in the operating magnetic field of the reader / writer device. When receiving the data string, the IC card existing in the operating magnetic field transmits a response data string to the reader / writer device. As a result, the reader / writer device recognizes that the IC card is in the operating magnetic field, and activates the IC card or puts it in the HALT state.
[0006]
The activation means that the IC card is ready to receive a command data string for normal processing. The HALT state is a state in which any command data string is received and does not respond unless the IC card is placed in a standby state and a command for canceling the HALT state is received. Once activated or in the HALT state, the IC card does not transmit a response data string even if an initial response data string is received again.
[0007]
When a plurality of IC cards are present in the operating magnetic field of the reader / writer device, when an initial response data string is received, the response data strings are simultaneously returned from each IC card. If the response data is returned at the same time, a collision occurs and the reader / writer device cannot recognize the response data of each IC card. Therefore, the following time slot method and slot marker command method are defined as means for preventing collision of response data strings transmitted from a plurality of IC cards.
[0008]
The time slot method has the following mechanism. The IC card that has received the initial response data string generates a random number within the range of the designated number of slots, and returns the response data string after a certain period determined according to the random number. Therefore, unless the generated random numbers match among a plurality of IC cards, the response data strings are returned at the same time, and there is no collision, and each IC card can be recognized. Then, as long as no collision occurs, each IC card is sequentially activated or brought into the HALT state. If a collision occurs, the process of transmitting the initial response data string again and returning the response data string after a fixed period determined by the newly generated random number is repeated until no collision occurs.
[0009]
On the other hand, the slot marker command method has the following mechanism. The IC card that has received the initial response data string generates a random number within the range of the designated number of slots, as in the time slot method. Thereafter, it receives a slot marker command, waits until the numerical value specified by the slot marker command matches the random number generated in the IC card, and returns the response data string at the matching timing. Thereafter, similarly, the IC card that has returned the response data string is activated or is in the HALT state, a slot marker command that specifies another numerical value is transmitted, and the next IC card is activated or is in the HALT state. Repeat sequentially.
[0010]
By adopting these procedures, as long as the random numbers generated in multiple IC cards do not match, the response data string is returned at the same time, and it is possible to recognize individual IC cards without colliding. it can. If a collision occurs, the initial response data string is transmitted again, and this procedure is repeated until no collision occurs.
[0011]
FIG. 4 is a flowchart showing a conventional procedure of initial response processing for recognizing a plurality of IC cards existing in an operating magnetic field in a reader / writer device adopting the time slot method or the slot marker command method as described above. It is. First, in step S1, the reader / writer device transmits a data string for initial response. If there is an IC card in the operating magnetic field of the reader / writer device at that time, a response data string from the IC card is received in step S2. The response data string transmission procedure is performed by the time slot method or the slot marker command method described above. If there is no IC card in the operating magnetic field of the reader / writer device, the response data string is not received, and the process returns to step S1 to retransmit the initial response data string.
[0012]
Upon receiving the response data string, the reader / writer device determines whether or not there is a collision in step S3. If a collision occurs, the reader / writer device returns to step S1 again and transmits the data string for the initial response. On the other hand, if a collision does not occur, in step S4, a command data string that activates necessary ones of individually identified IC cards and sends unnecessary ones to the HALT state is transmitted. To do.
[0013]
When the recognition of each IC card is completed in this way, in step S5, a command data string that causes each IC card to perform a desired operation is transmitted. By performing the collision prevention process in this way, even when a plurality of IC cards exist within the operating magnetic field of the reader / writer device, collision is avoided, each IC card is recognized, and a desired signal is obtained. Are being exchanged.
[0014]
[Problems to be solved by the invention]
However, a collision can be determined when there is a subtle time difference between the response data strings from each IC card. If subcarriers are sent as response data strings at the same time, the collision is not determined, and A relatively low energy subcarrier is masked by a high energy subcarrier, and there is a problem in that only the response data string by the largest energy subcarrier is recognized. That is, in the conventional recognition method described above, even if a plurality of IC cards exist in the operating magnetic field of the reader / writer device, some of the cards may not be recognized. This point will be described in detail below. The energy difference occurs when the distance between the reader / writer device and each IC card is different, for example.
[0015]
5A and 5B are waveform diagrams for explaining phase modulation in the BPSK system. FIG. 5A shows a carrier wave, and FIG. 5B shows a subcarrier wave. With respect to the 13.56 MHz carrier wave, load modulation is started with a subcarrier wave of 847 kHz from time t0. Accordingly, the period of the subcarrier wave is 16 times the period of the carrier wave, and if the half period is 1 bit, the interval of 1 bit is 8 periods.
[0016]
For example, in the case of constant speed communication that communicates at 106 kbps, one data has a phase difference of 180 ° from “1010101010101010” as shown in FIG. 6A, and “01010101010101101” as shown in FIG. 6B. It is expressed by two kinds of data strings. Whether one data is 0 or 1 is determined by whether the phase change point in FIG. 6 is high or low.
[0017]
Here, when two IC cards A and B are considered, and response data sequences having mutually different energies are returned at the same time (equal in phase), the combined waves received by the reader / writer device are The cases of FIGS. 7 and 8 can be considered. 7 and 8 show the carrier wave modulated by the IC card A and the IC card B and the subcarrier wave which is the modulated wave, and the combined wave by them and the low-pass filter 11 passing it. The component of the obtained subcarrier wave is shown.
[0018]
FIG. 7 shows a case where the data values are equal to each other, that is, the phases of the subcarrier waves are equal to each other, and the subcarrier wave components obtained from the combined wave are amplified. That is, the component of the subcarrier wave is a response data string having a larger level difference and a larger energy.
[0019]
On the other hand, FIG. 8 shows a case where the data values are different from each other, that is, the phases of the subcarrier waves are different from each other, and the component of the subcarrier wave obtained from the combined wave has a relatively large energy. The component of the subcarrier wave of the IC card A is attenuated to form a response data string with smaller energy.
[0020]
In this way, when response data strings are returned from a plurality of IC cards at exactly the same timing in the BPSK method, relatively small energy subcarriers are masked by large energy subcarriers as described above. Thus, it can be understood that only the response data string by the subcarrier having the largest energy is recognized.
[0021]
It is an object of the present invention to perform response signals from a plurality of IC chips when reading / writing using a signal modulated in phase by the BPSK method between the plurality of IC chips and a data read / write terminal. BPSK signal recognition method capable of accurately recognizing a signal, and a non-contact IC card terminal device using the recognition method.
[0022]
[Means for Solving the Problems]
According to the BPSK signal recognition method of the present invention, when reading / writing is performed between a plurality of IC chips and a data read / write terminal using a signal modulated in phase by the BPSK method, the read / write is performed. In the method for recognizing a BPSK signal implemented on the / write terminal side, a step of transmitting an initial response signal from the read / write terminal, and a step of receiving a response signal transmitted from an IC chip that has received the initial response signal; , Detecting whether or not response signals from the plurality of IC chips collide, and when detecting that the response signals do not collide, recognize and recognize the IC chip of the received response signals And a step of transmitting a signal prohibiting response to the IC chip.
[0023]
According to the above configuration, when reading / writing is performed between a plurality of IC chips such as a non-contact type IC card and the reading / writing terminal using a signal modulated in phase by the BPSK method. In the signal recognition method, it is possible to determine that there is a collision when the response signals from the plurality of IC chips are shifted in timing with respect to the initial response signal. The initial response signal is transmitted again, and in response to this, each IC chip returns a response signal in a different time slot so that the read / write terminal sequentially recognizes each IC chip. Can do.
[0024]
On the other hand, when the timings of response signals from a plurality of IC chips coincide with each other with respect to the initial response signal, in this BPSK system signal, a signal having a small energy is masked by a signal having a large energy. Therefore, the collision is not determined. Therefore, first, a signal for preventing the response of the IC chip of the received response signal having a large energy, such as activation or a HALT state, is transmitted, and after the response signal having the large energy is not returned, the above-described response is again performed. The processing from transmission of the initial response signal to reception and recognition of the response signal is repeated until no response signal is detected.
[0025]
As a result, even if a plurality of IC chips are present in the operating magnetic field of the read / write terminal, all the IC chips are recognized sequentially and the desired data is read from the desired IC chip, or Desired data can be written to a desired IC chip.
[0026]
Further, the terminal device of the non-contact type IC card according to the present invention is characterized by using the above recognition method.
[0027]
According to the above configuration, the non-contact IC card includes an antenna coil in which an IC chip that is read / written using the BPSK signal is embedded in the card, and the IC chip is embedded in the outer periphery of the card. Therefore, the present invention can be preferably implemented.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to FIGS.
[0029]
FIG. 2 is a block diagram showing a configuration example of the non-contact type IC card 1 in which the present invention is implemented and the reader / writer device 2 thereof. An antenna coil 3 is embedded in the outer peripheral portion of the IC card 1. When the 13.56 MHz carrier wave from the reader / writer device 2 is applied to the antenna coil 3, an electromotive force is generated. This electromotive force is supplied as a power source to the IC chip module 5 through the capacitor 4, and the IC card 1 is automatically activated, and thereafter, exchange of signals such as an initial response is started. The IC chip module 5 writes / reads data as necessary, and performs load modulation of the carrier wave from the antenna coil 3 with the subcarrier wave of 847 kHz corresponding to the data to be transmitted.
[0030]
In the reader / writer device 2, the transmission circuit 7 generates the carrier wave from the antenna coil 8 in response to a signal from the control circuit 6. The signal received by the antenna coil 8 is demodulated by the receiving circuit 9, and the demodulated data is taken into the control circuit 8 and transferred to the host device or the like via the communication port 10 as necessary. The
[0031]
FIG. 3 is a block diagram showing a configuration example of the receiving circuit 9. The reception circuit 9 is generally configured to include a low-pass filter 11, an amplifier 12, a comparator 13, a demodulation circuit 14, and series resistors 15 and 16 that generate a reference voltage.
[0032]
The received signal is applied to a low-pass filter 11 where the 13.56 MHz carrier wave component is removed, and the 847 kHz subcarrier wave component serving as information is extracted. The subcarrier wave component is amplified by the amplifier 12 and input to one input of the comparator 13. The other input of the comparator 13 is supplied with a reference voltage generated by dividing the power supply voltage by the series resistors 15 and 16, and the comparator 13 has the subcarrier wave component having a potential higher than the reference voltage. The digital data is obtained by determining “1” if the value is high and “0” if the value is low. In this way, a data string that repeats “0” and “1” is obtained. This data string is input to the demodulation circuit 14, and data is demodulated from the presence or absence of 180 ° phase modulation.
[0033]
FIG. 1 is a flowchart of an initial response process for recognizing a plurality of IC cards according to an embodiment of the present invention. This initial response process is performed in a reader / writer device adopting the above-described time slot method or slot marker command method.
[0034]
First, in step S11, the reader / writer device transmits a data string for initial response. If there is an IC card in the operating magnetic field of the reader / writer device at that time, a response data string from the IC card is received in step S12. The response data string transmission procedure is performed by the time slot method or the slot marker command method described above. If there is no IC card in the operating magnetic field of the reader / writer device, the response data string is not received, and the process returns to step S11 to retransmit the initial response data string.
[0035]
When the response data string is received, the reader / writer device determines whether or not there is a collision in step S13. If a collision occurs, the reader / writer device returns to step S11 again and transmits a data string for initial response. On the other hand, if a collision does not occur, in step S14, a command data string in which necessary ones are activated among the individually identified IC cards and unnecessary ones are sent to the HALT state is transmitted. To do.
[0036]
Thus, when one kind of recognition is completed as in steps S1 to S4 in FIG. 4, it should be noted that in the present invention, in steps S15 and S16, as in steps S11 and S12, the initial response is returned. It is to determine whether to send a data string and receive a response data string. If the response data string is received, the process returns to step S13 to determine whether or not there is a collision. If no collision occurs, the necessary one of the newly identified IC cards is identified in step S14. Is activated, and a command data string for setting unnecessary ones to the HALT state is transmitted.
[0037]
If no response data string is received in step S16, it is determined that there is no unrecognized IC card in the operating magnetic field of the reader / writer device, and the recognition process is terminated. In step S17, step S5 is performed. Similarly to the above, a command data string for causing each IC card to perform a desired operation is transmitted. Such initial response processing is completed in about several milliseconds even when a plurality of IC cards are recognized.
[0038]
In this way, by repeating the recognition as long as the response data string is received, together with the collision prevention processing by the time slot method or the slot marker command method, the energy for carrying the response data string differs due to the difference in distance or the like. However, it is possible to reliably recognize a plurality of IC cards present in the operating magnetic field of the reader / writer device. Therefore, practicality can be increased by adding a simple procedure as in the present application.
[0039]
【The invention's effect】
As described above, the BPSK signal recognition method of the present invention uses the signal modulated in phase by the BPSK method between a plurality of IC chips such as a non-contact type IC card and the read / write terminal. In the signal recognition method realized when performing read / write, the IC chip of the response signal having a large energy received previously is not responded to the initial response signal such as activation or HALT state. After transmitting a signal to be transmitted and preventing a response signal having a large energy from being returned, the process of receiving and recognizing the response signal from the transmission of the initial response signal is repeated again until no response signal is detected.
[0040]
Therefore, even when a plurality of IC chips are present in the operating magnetic field of the read / write terminal, all the IC chips are sequentially recognized and the desired data is read from the desired IC chip, or Desired data can be written to a desired IC chip.
[0041]
In addition, as described above, the noncontact IC card terminal device of the present invention uses the recognition method.
[0042]
Therefore, the present invention is particularly suitable.
[Brief description of the drawings]
FIG. 1 is a flowchart of an initial response process for recognizing a plurality of IC cards according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration example of a non-contact type IC card and its reader / writer device in which the present invention is implemented.
3 is a block diagram illustrating an example of a configuration of a receiving circuit in the reader / writer device illustrated in FIG. 2;
FIG. 4 is a flowchart of a prior art initial response process for recognizing a plurality of IC cards.
FIG. 5 is a waveform diagram for explaining phase modulation in the BPSK system.
FIG. 6 is a waveform diagram showing data in the case of constant speed communication in the BPSK system.
FIG. 7 is a waveform diagram showing carrier waves and subcarrier waves when response data strings are returned from two IC cards at exactly the same time.
FIG. 8 is a waveform diagram showing carrier waves and subcarrier waves when response data strings are returned from two IC cards at exactly the same time.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 IC card 2 Reader / writer apparatus 3, 8 Antenna coil 5 IC chip module 6 Control circuit 7 Transmission circuit 9 Reception circuit 10 Communication port 11 Low pass filter 12 Amplifier 13 Comparator 14 Demodulation circuits 15 and 16 Series resistance

Claims (2)

A BPSK signal implemented on the read / write terminal side when the read / write is performed using a signal modulated in phase by the BPSK method between a plurality of IC chips and the data read / write terminal. In the recognition method of
Transmitting an initial response signal from the read / write terminal;
Receiving a response signal transmitted from the IC chip that has received the initial response signal;
Detecting whether or not response signals from the plurality of IC chips collide;
When it is detected that the response signals do not collide, a step of recognizing the IC chip of the received response signal and transmitting a signal for inhibiting the response to the recognized IC chip is repeated. Recognition method. A noncontact IC card terminal device using the recognition method according to claim 1.

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