JP2004056205A - Method of recognizing bpsk signal, and terminal for contactless ic card employing the recognition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a demodulation circuit for a BPSK (binary phase shift keying) signal realized as a contactless IC card reader/writer that can accurately recognize response signals from a plurality of IC cards. <P>SOLUTION: The operation of the IC card reader/writer includes: step S11 for transmitting a data stream for initial response; step S13 for judging the occurrence of a collision when a response data stream is received in step S12, and returning to the step S11 again on the occurrence of a collision; step S14 for activating required IC cards among the IC cards that are individually recognized in this step when no collision takes place and transmitting a command data stream to bring a HALT state to the IC cards that are not required; and steps S15, S16 for transmitting the data stream for initial response similarly to the case with the steps S11, S12 again, and discriminating whether the response data stream is to be received. Thus, this method can reliably recognize the plurality of IC cards even when the energy for transporting the response data stream differs due to the difference of distance or the like. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD 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. And a terminal device of a non-contact type IC card using the recognition method.
[0002]
[Prior art]
2. Description of the Related Art It has been conventionally performed to embed an IC chip in various objects and perform communication in a non-contact manner, thereby reading information of an embedded object and a person who carries the IC chip. Particularly, the IC chip is embedded in a card and has already been put to practical use as a commuter pass or the like. In the field of such an IC card, a communication method using BPSK modulation is defined in ISO / IEC-14443 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. It should be noted that an IC card referred to as a combination type that can take in an IC card into a reader / writer device and perform writing / reading by contacting terminals, and can perform writing / reading wirelessly without contact. Also, BPSK modulation is used for the non-contact communication.
[0003]
The BPSK modulation modulates a carrier wave transmitted from a reader / writer device by whether or not an IC card applies a load of a subcarrier wave, and the reader / writer device modulates the carrier wave from the modulated carrier wave. Data is demodulated by detecting a point of phase change. In the ISO / IEC-14443, load modulation is performed on a carrier wave having a frequency of 13.56 MHz with a subcarrier wave having a frequency of 847 kHz.
[0004]
In an IC card system configured as described above, for example, a system is used in which one card is used for personal authentication and another card is used for starting an application in the card, and is sent from a reader / writer device. There may be a case where a plurality of IC cards 1 exist within the reach of the electromagnetic wave. In such a case, when the plurality of IC cards are activated and exchange of signals such as an initial response is started, there is a risk that signal collision occurs. For this reason, the procedure for initial response and collision prevention is standardized as ISO / IEC-14443-3 in ISO / IEC-14443, which is an international standard for IC cards.
[0005]
According to the standard, when confirming whether or not an IC card exists in the operating magnetic field of the reader / writer device, the reader / writer device transmits a data string for an initial response. When the IC card present in the operating magnetic field receives the data sequence, it transmits a response data sequence to the reader / writer device. As a result, the reader / writer recognizes that the IC card exists in the operating magnetic field, and activates or sets the IC card to the HALT state.
[0006]
The activation means that the IC card can receive a command data string for normal processing. Further, the HALT state is a state in which the IC card is put into a standby state and no response is received even if any command data string is received unless a command for canceling the HALT state is received. Once activated or in the HALT state, the IC card does not transmit the response data sequence even if the data sequence for the initial response is received again.
[0007]
When a plurality of IC cards are present in the operating magnetic field of the reader / writer device, when a data string for an initial response is received, the response data strings are returned from each IC card all at once. Here, 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 collision prevention means for 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 data sequence for the initial response generates a random number within the specified number of slots, and returns the response data sequence after a certain period determined according to the random number. Therefore, as long as the generated random numbers do not match among a plurality of IC cards, the response data strings are returned at the same time, and there is no collision and individual IC cards can be recognized. Then, while no collision occurs, each IC card is sequentially activated or set to the HALT state. If a collision occurs, the process of transmitting the data sequence for the initial response again and returning the response data sequence after a certain period determined by the newly generated random number is repeated until the collision does not occur.
[0009]
On the other hand, the slot marker command method has the following mechanism. The IC card that has received the data sequence for the initial response generates a random number within the specified number of slots, as in the time slot method. After that, it receives a slot marker command, waits until the numeric value specified by the slot marker command matches the random number generated in the IC card, and returns a response data string at the matching timing. Thereafter, similarly, the process of activating or setting the IC card that has returned the response data string to the HALT state, transmitting a slot marker command specifying another numerical value, and activating or setting the next IC card to the HALT state is performed. Repeat sequentially.
[0010]
By adopting these procedures, unless the random numbers generated in a plurality of IC cards match, the response data string is returned at the same time, without collision, and individual IC cards can be recognized. it can. If a collision occurs, the data string for the initial response is transmitted again, and this procedure is repeated until the collision does not occur.
[0011]
FIG. 4 is a flowchart showing a conventional procedure of an initial response process 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 transmits a data string for an initial response. If the IC card is present in the operating magnetic field of the reader / writer device at that time, a response data string is received from the IC card in step S2. The transmission procedure of the response data sequence is performed by the above-described time slot method or slot marker command method. If there is no IC card in the operating magnetic field of the reader / writer device, the response data sequence is not received, and the process returns to step S1 to retransmit the data sequence for the initial response.
[0012]
Upon receiving the response data sequence, the reader / writer determines in step S3 whether or not there is a collision. If a collision occurs, the reader / writer returns to step S1 again and transmits a data sequence for an initial response. On the other hand, if no collision occurs, in step S4, of the individually identified IC cards, a necessary one is activated, and an unnecessary one is transmitted to a HALT state command data string. I do.
[0013]
When the recognition of each IC card is completed in this way, in step S5, a command data string for causing each IC card to perform a desired operation is transmitted. By executing the collision prevention processing in this manner, even when a plurality of IC cards exist in the operating magnetic field of the reader / writer device, collision is avoided, individual IC cards are recognized, and a desired signal is recognized. Exchanges are taking place.
[0014]
[Problems to be solved by the invention]
However, a collision can be determined when there is a slight time difference in the response data sequence from each IC card, and when subcarriers are sent as a response data sequence at exactly the same time, a collision is not determined, and There is a problem that a subcarrier having a relatively small energy is masked by a subcarrier having a large energy, and only a response data sequence based on the subcarrier having the largest energy 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, there is a possibility that some of the cards cannot be recognized. This will be described in detail below. The energy difference occurs when, for example, the distance between the reader / writer device and each IC card is different.
[0015]
FIGS. 5A and 5B are waveform diagrams for explaining the phase modulation in the BPSK method. 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 from time t0 with a 847 kHz subcarrier wave. Therefore, 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 1 × speed communication at 106 kbps, one data is 180 ° out of phase with “10101010101101010” as shown in FIG. 6A, and is “01010101010101101” as shown in FIG. 6B. Are represented by two types 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, two IC cards A and B are considered, and when response data strings having mutually different energies are returned at exactly the same time (equal in phase) from each other, a combined wave received by the reader / writer device is generated. The case of FIG. 7 and FIG. 8 can be considered.
FIGS. 7 and 8 show a carrier wave and a subcarrier wave as a modulated wave which are load-modulated by the IC card A and the IC card B. The components of the obtained subcarrier wave are shown.
[0018]
FIG. 7 shows a case where the values of the data are equal to each other, that is, the phases of the subcarrier waves are equal to each other. The components of the subcarrier wave obtained from the composite wave are amplified. That is, the component of the subcarrier wave has a larger difference in height, and is a response data string having a large 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. The component of the subcarrier wave obtained from the composite 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 having lower 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, the subcarriers having relatively small energy are masked by the subcarriers having large energy as described above. As a result, it is understood that only the response data sequence using the subcarrier having the largest energy is recognized.
[0021]
SUMMARY OF THE INVENTION It is an object of the present invention to read / write signals between a plurality of IC chips and a terminal for reading / writing the data by using signals phase-modulated by the BPSK method. And a terminal device of a non-contact type IC card using the BPSK signal recognition method capable of accurately recognizing the BPSK signal.
[0022]
[Means for Solving the Problems]
The method of recognizing a BPSK signal according to the present invention includes the steps of: performing a read / write operation between a plurality of IC chips and a data read / write terminal using a signal modulated in phase by the BPSK method; A method for recognizing a BPSK signal performed on a side of a read / write terminal, the method comprising: transmitting an initial response signal from the read / write terminal; and receiving a response signal transmitted from an IC chip having received the initial response signal. Detecting whether or not the response signals from the plurality of IC chips have collided; and, if detecting that the response signals have not collided, recognizing and recognizing the IC chip of the received response signal. And transmitting a signal prohibiting a response to the IC chip.
[0023]
According to the above configuration, when the read / write is performed between a plurality of IC chips such as a non-contact type IC card and the read / write terminal using a signal modulated in phase by the BPSK method. In the signal recognition method to be performed, when the response signals from the plurality of IC chips are different from each other in timing with respect to the initial response signal, it is possible to determine that the collision occurs, and the read / write terminal performs The read / write terminal sequentially recognizes each IC chip by transmitting the initial response signal again, and in response to this, each IC chip returns a response signal in a mutually different time slot. Can be.
[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, a signal having a small energy is masked by a signal having a large energy in this BPSK signal. 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 is activated or the HALT state is not transmitted, and the response signal having the large energy is not returned. The process from transmission of the initial response signal to reception and recognition of the response signal is repeated until no response signal is detected.
[0025]
Thereby, even if a plurality of IC chips exist in the operating magnetic field of the read / write terminal, all the IC chips are sequentially and accurately recognized, and desired data is read from desired IC chips, or Desired data can be written to a desired IC chip.
[0026]
Further, a non-contact type IC card terminal device according to the present invention uses the above-described recognition method.
[0027]
According to the above configuration, the contactless IC card has an antenna coil in which an IC chip to be read / written by using the BPSK signal is embedded in the card and the IC chip is embedded in the outer peripheral portion of the card. Therefore, the present invention can be suitably implemented.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
One embodiment of the present invention will be described below with reference to FIGS.
[0029]
FIG. 2 is a block diagram showing one configuration example of a non-contact type IC card 1 in which the present invention is implemented and a reader / writer device 2 thereof. An antenna coil 3 is embedded in the outer peripheral portion of the IC card 1, and 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 power to the IC chip module 5 via the capacitor 4, and the IC card 1 automatically becomes active, and thereafter starts to exchange signals such as an initial response. The IC chip module 5 writes / reads data as required, and load modulates the carrier wave with the 847 kHz subcarrier wave from the antenna coil 3 in accordance with 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 a receiving circuit 9, and the demodulated data is taken into the control circuit 8 and transferred to a host device or the like via a communication port 10 as necessary. You.
[0031]
FIG. 3 is a block diagram showing an example of the configuration of the receiving circuit 9. The receiving circuit 9 includes a low-pass filter 11, an amplifier 12, a comparator 13, a demodulation circuit 14, and series resistors 15 and 16 for generating a reference voltage.
[0032]
The received signal is supplied 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. A reference voltage generated by dividing the power supply voltage by the series resistors 15 and 16 is applied to the other input of the comparator 13, and the comparator 13 determines that the subcarrier wave component has a higher potential than the reference voltage. Is determined to be “1” if the value is high and “0” if the value is low, thereby obtaining digital data.
Thus, a data string in which "0" and "1" are repeated is obtained. This data sequence is input to the demodulation circuit 14, and the data is demodulated based on the presence or absence of the 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 that employs the above-described time slot method or slot marker command method.
[0034]
First, in step S11, the reader / writer transmits a data string for an initial response. If an IC card is present in the operating magnetic field of the reader / writer device at that time, a response data string is received from the IC card in step S12.
The transmission procedure of this response data sequence is performed by the above-described time slot method or slot marker command method. If there is no IC card in the operating magnetic field of the reader / writer device, the response data sequence is not received, and the process returns to step S11 to retransmit the data sequence for the initial response.
[0035]
Upon receiving the response data string, the reader / writer determines in step S13 whether or not there is a collision. If a collision occurs, the reader / writer returns to step S11 again and transmits a data string for an initial response. On the other hand, if no collision occurs, in step S14, among the individually identified IC cards, a necessary one is activated, and an unnecessary one is sent to the HALT state. I do.
[0036]
When one type of recognition is completed in the same manner as in steps S1 to S4 in FIG. 4, it should be noted that, in the present invention, in steps S15 and S16, the initial response It is to determine whether to transmit a data sequence and receive a response data sequence. If the response data string has been received, the process returns to step S13 to determine whether or not a collision has occurred. If no collision has occurred, the process returns to step S14, where necessary ones of the newly identified IC cards are used. Is activated, and unnecessary ones are sent to the HALT state.
[0037]
If the response data string is not received in step S16, it is determined that there is no IC card that has not yet been recognized in the operating magnetic field of the reader / writer device, and the recognition process is terminated. In the same manner as described above, a command data string for causing each IC card to perform a desired operation is transmitted. Such an initial response process ends in about several msec even if 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 is different due to a difference in distance or the like. Also, it is possible to reliably recognize a plurality of IC cards present in the operating magnetic field of the reader / writer device. Therefore, the practicality can be increased by adding a simple procedure as in the present application.
[0039]
【The invention's effect】
As described above, the method of recognizing a BPSK signal according to the present invention uses the signal BPSK-modulated between a plurality of IC chips such as a non-contact type IC card and a read / write terminal thereof. In a signal recognition method realized at the time of reading / writing, in response to an initial response signal, an IC chip of a previously received response signal having a large energy is not activated or responded as in a HALT state. After the transmission of the initial response signal, the process of receiving and recognizing the response signal from the transmission of the initial response signal is repeated until the response signal is no longer detected.
[0040]
Therefore, even if a plurality of IC chips are present in the operating magnetic field of the read / write terminal, all the IC chips are sequentially and accurately recognized, and desired data is read from desired IC chips, or Desired data can be written to a desired IC chip.
[0041]
Further, the terminal device of the non-contact type IC card of the present invention uses the above-described recognition method as described above.
[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 illustrating a configuration example of a non-contact type IC card in which the present invention is implemented and a reader / writer device thereof.
FIG. 3 is a block diagram illustrating a configuration example of a receiving circuit in the reader / writer device illustrated in FIG. 2;
FIG. 4 is a flowchart of a conventional initial response process for recognizing a plurality of IC cards.
FIG. 5 is a waveform diagram for explaining phase modulation in the BPSK method.
FIG. 6 is a waveform diagram showing data in the case of 1 × speed communication in the BPSK method.
FIG. 7 is a waveform diagram showing a carrier wave and a subcarrier wave when response data strings are returned from two IC cards at exactly the same time.
FIG. 8 is a waveform diagram showing a carrier wave and a subcarrier wave when a response data string is returned from two IC cards at exactly the same time.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 IC card 2 Reader / writer device 3, 8 Antenna coil 5 IC chip module 6 Control circuit 7 Transmission circuit 9 Receiving circuit 10 Communication port 11 Low-pass filter 12 Amplifier 13 Comparator 14 Demodulation circuit 15, 16 Series resistance

Claims (2)

A BPSK signal that is executed on the read / write terminal side when the read / write is performed between a plurality of IC chips and a data read / write terminal using a signal that is phase-modulated by the BPSK method. In the recognition method of
Issuing 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 the response signals from the plurality of IC chips collide;
A step of recognizing an IC chip of the received response signal and transmitting a signal prohibiting a response to the recognized IC chip when the response signal is detected as not colliding. Recognition method. A non-contact type IC card terminal device using the recognition method according to claim 1.

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