JPH11328342A - Noncontact ic card - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stable reference signal for a data storage body which is supplied with electric power or has data accessed by an electromagnetic induction coupling system without requiring any electric contact. SOLUTION: The noncontact IC card has a phase-locked loop(PLL) inside is so constituted as to use a binarizing process signal as a reference signal when waiting for or receiving receive data from a reader writer and a signal held by a PLL part 95 as a reference signal when sending an answer back from the noncontact IC card. Consequently, a low-cost, stable communication can be made even when answer data are sent back even over a long communication distance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data storage unit for receiving power supply or performing data access without an electrical contact by an electromagnetic inductive coupling system. More specifically, the present invention relates to a storage body such as a non-contact IC card which communicates with a data reading device such as a reader / writer.

[0002]

2. Description of the Related Art In recent years, non-contact ICs in which necessary circuits for thinning are integrated in an IC chip and built in, and transmit and receive data without using a power supply or electrical contacts by using electromagnetic induction coupling or the like. Data carriers such as cards are being developed.
This non-contact IC card does not have to be brought into contact with the main unit every time it is used, and since it does not have any contacts, it has the convenience of being free from dirt and corrosion and can be designed more freely. So personal ID
It is a product that can be expected to have a very large market in various fields such as the financial field as cards and the like.

A conventional non-contact IC card is disclosed in, for example,
Japanese Patent Application Laid-Open No. 99698/1996 and Japanese Patent Application Laid-Open No. H4-241082 are known.

FIG. 2 shows the structure of a conventional non-contact IC card. The non-contact IC card has coils 70 and 80 for electromagnetic induction coupling with a transmission / reception coil of a reader / writer (not shown), a receiving unit 92 for receiving a signal carried at the frequency f1, and rewriting of an EEPROM or the like. A control circuit 90 provided with a possible non-volatile memory 91;
A transmitting unit 93 that returns response data on a carrier wave of frequency f1
And a rectifier 81 and a regulator 82, which are a power supply unit 94 for obtaining operating power of the control circuit 90 and the like from an induced electromotive force induced in the receiving coil 80 by electromagnetic induction coupling, and binarize a signal induced in the coil 80. And a comparator 84 for processing.

In order to restore the command from the reader / writer received by the transmission / reception coil 70, the receiving section 92 converts the electromagnetically converted signal from the electromagnetically converted signal through the differential input buffer 61 to the band-pass filter 62 centering on the frequency f1. A band component is extracted and amplified by an amplifier 63 to generate a reception signal. Further, the receiving section 92 has a demodulation circuit 64 that performs demodulation processing such as the PSK method, obtains demodulated data from the received signal, and performs decoding processing of the demodulated data based on the NRZ code and the like by the decoding circuit 65 and decodes the data. The demodulated data is transmitted to the control circuit 90.

The control circuit 90 analyzes the command sent from the reader / writer, reads out the data from the specified address of the specified memory 91 if the content of the command is a memory read, and sends the data to the transmitting unit 93 as response data. Output. If the content of the instruction is a memory write, the data is written to the specified address of the designated memory 91, and a response of the completion of the write is transmitted as response data to the transmitting unit 9.
Output to 3.

The transmitting section 93 encodes the instruction by an encoding circuit 74 based on an NRZ code or the like to transmit the instruction using the mutual induction action of the coils.
3, the carrier wave of frequency f1 is subjected to digital modulation such as the PSK method using the encoded data, and response data is transmitted from the coil 70 via the amplifier 72 and the bridge drive circuit 71.

A power supply 94 of the non-contact IC card receives a signal received by the rectifier 81 for receiving and rectifying the alternating current induced in the receiving coil 80, a regulator 82 for stabilizing the rectified voltage Vcc, and a signal received by the receiving coil 80. Comparator 8 for performing electromagnetic conversion, binarizing and reproducing as a reference signal
4 and 4. Here, the battery 83 does not necessarily need to be built in the non-contact IC card, but is indispensable to supply power required for communication in order to increase the communication distance between the reader / writer and the non-contact IC card.

[0009]

However, in the conventional non-contact IC card, a battery is used for power supply to secure the transmission power. However, when the communication distance is further increased, the electromagnetic inductive coupling becomes weaker. The reduced signal level becomes susceptible to noise and the like. Specifically, if the communication distance is increased, the carrier f1 of the data returned inside the non-contact IC card interferes with f2 which is the basis of the reference signal for the circuit operation, and the reference signal cannot be reproduced stably.
As a result, normal communication cannot be performed. In order to prevent this, a method of incorporating a resonator for obtaining a stable reference signal into the non-contact IC card is conceivable, but this method has a problem that the cost is increased. In particular, an oscillator such as a crystal cannot be built in a thin non-contact IC card such as a card.

The present invention solves such a conventional problem. The present invention can be used for a thin card without increasing the cost, can eliminate the influence of noise, and can increase the communication distance. Non-contact IC that can supply stable power to the internal circuit of the non-contact IC card
The purpose is to provide the card.

[0011]

In order to achieve the above object, according to the present invention, a non-contact IC card is provided with a phase synchronization system (PL).
L: phase-locked loop). The reception data from the reader / writer is received or received by electromagnetic inductive coupling at the time of reception or reception, and the signal obtained by the electromagnetic conversion is held in the PLL unit when a response is returned from the non-contact IC card as a reference signal. In this case, the reference signal is used as the reference signal.

Thus, stable communication can be performed at low cost even when returning response data when the communication distance becomes long.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG.
1 shows a non-contact IC card according to the present invention, which performs communication based on an electromagnetic induction coupling system using mutual induction of coils,
In a contactless IC card receiving power supply, in addition to reproducing and using a power supply waveform supplied from a reader / writer as a reference signal for processing data, a reference signal is generated by an internal circuit for a predetermined period even if this signal is interrupted. This means that stable communication can be performed even when response data is returned when the communication distance becomes long.

The non-contact IC card has coils 70 and 80 for electromagnetic induction coupling with a transmission / reception coil of a reader / writer, a receiving unit 92 for receiving a signal carried at the frequency f1, and a rewritable EEPROM or the like. A non-volatile memory 91 attached thereto, a transmission unit 93 for returning response data as a carrier wave of frequency f1, and an operation of the control circuit 90 and the like from the induced electromotive force induced in the receiving coil 80 by electromagnetic induction coupling. A rectifier 81, a regulator 82, and a comparator 84 for binarizing a signal induced in the coil 80, a PLL unit 95 for supplying a stable reference signal, and a switch unit 89 are provided. Consists of

In order to restore the command from the reader / writer received by the transmission / reception coil 70, the receiving section 92 converts the electromagnetically converted signal from the electromagnetically converted signal through the differential input buffer 61 to the band-pass filter 62 centering on the frequency f1. A band component is extracted and amplified by an amplifier 63 to generate a reception signal. Further, the receiving section has a demodulation circuit 64 for performing demodulation processing such as the PSK method, obtains demodulated data from the received signal, performs decoding processing of the demodulated data based on the NRZ code or the like, and outputs the decoded demodulated data to the control circuit. 90.

The control circuit 90 analyzes the command sent from the reader / writer, reads out the data from the specified address of the specified memory 91 if the content of the command is a memory read, and sends the data as response data to the transmitting unit 93. Output. If the content of the instruction is a memory write, the data is written to the specified address of the designated memory 91, and a response of the completion of the write is transmitted as response data to the transmitting unit 9.
Output to 3.

The transmitting section 93 encodes the instruction based on the NRZ code or the like by the encoding circuit 74 and encodes the instruction on the carrier wave of the frequency f1 by the modulation circuit 73 in order to transmit the instruction using the mutual induction action of the coils. The digital data is subjected to digital modulation such as the PSK method using the converted data, and response data is transmitted from the coil 70 via the amplifier 72 and the bridge drive circuit 71. Here, the control circuit 90 may be configured by a dedicated wired logic circuit.

The power supply 94 of the non-contact IC card receives the rectifier 81 for receiving and rectifying the alternating current induced in the receiving coil 80, the regulator 82 for stabilizing the voltage Vcc of the rectified current, and the receiving coil 80. A comparator 84 converts the signal into an electromagnetic signal, binarizes the signal, and reproduces the signal as a reference signal. The binarized signal is P
The error voltage is detected by the phase comparator 85 of the LL unit 95 and converted into a DC voltage by the loop filter 86, and the voltage control oscillator 88
The signal oscillated in the above is fed back to the 85 phase comparator. A capacitor 87 holds the input voltage of the voltage controlled oscillator 88. Reference numeral 89 denotes a switch circuit for selecting a reference signal.

In the above description, the voltage controlled oscillator 88
Has been described as an example in which the voltage is input to and held by the capacitor 87. However, the present invention can be similarly implemented by applying a voltage using a D / A converter.

Next, a specific operation of the present invention will be described. When receiving or waiting for reception, the non-contact IC card electromagnetically converts a signal received by the receiving coil 80 and binarizes the signal to use as a reference signal of the control circuit. Since a non-contact IC card has only a function of responding to a request signal sent from a reader / writer, it does not transmit data by itself. Therefore, the reference signal is usually used by reproducing a signal transmitted from the reader / writer. At this time, the binarized reference signal is input to the phase comparator 85 of the PLL unit 95, rectifies the error voltage by the loop filter 86, locks the oscillation frequency of the voltage controlled oscillator 88 by the rectified voltage, The output of the loop filter 86 is a capacitor 87
Is charged.

The non-contact IC card analyzes the command sent from the reader / writer, reads out the data from the specified address of the specified memory if the content of the command is a memory read, and uses the data as response data as a response data. Output to Also, if the instruction content is a memory write,
The data is written to the specified address of the designated memory, and the response of the completion of writing is transmitted as response data to the transmitting unit 93.
Output to At this time, the control circuit 90 sets the reference signal to PL.
The output is switched to the output from the L unit 95. Further, the output of the loop filter is cut off so that the PLL loop does not follow an interference wave such as noise.

[0022]

As described above, according to the first aspect of the present invention, by providing the PLL unit, it is possible to secure stable communication even when returning response data when the distance to the reader / writer is long. it can. According to the experiment of the inventor of the present application, the distance at which stable communication was possible was 40 cm in the conventional non-contact IC card, whereas the stable communication distance was in the non-contact IC card of the present invention. It became 100 centimeters.

According to the third aspect of the present invention, the output of the loop filter is shut off when the response data is returned.
An adverse effect when the response data is received by the PLL unit 95 as noise can be completely blocked.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a contactless IC card of the present invention.

FIG. 2 is a configuration diagram of a conventional non-contact IC card.

[Explanation of symbols]

 89 switch means 90 control circuit 91 memory 92 receiving section 93 transmitting section 94 power supply section 95 PLL section

Claims (3)

[Claims] A receiving unit that receives an input signal from a reader / writer based on an electromagnetic induction coupling method using mutual induction of coils; a control circuit that receives data signals from the receiving unit and performs predetermined control; A PLL unit, comprising: a transmission unit that receives a data signal from the control circuit and transmits an output signal to the reader / writer; and a power supply unit that receives an input signal from the reader / writer and generates power, and generates a reference signal for a predetermined period. A non-contact IC card characterized by comprising: 2. The non-contact IC card according to claim 1, wherein signals obtained by a plurality of different means are appropriately switched and used as a reference signal. 3. The non-contact IC card according to claim 1, wherein a feedback loop for controlling oscillation is cut off during a period when the reference signal is being generated in the PLL unit, thereby preventing external interference. A non-contact IC card, which excludes and maintains a frequency for a certain period.