JPH09282429A - Noncontact type data carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a noncontact type data carrier which can efficiently secure a power supply distance from a reader writer and a communication distance and to obtain a stable demodulated signal and is reducible in size. SOLUTION: The noncontact type data carrier 10 is equipped with an oscillation circuit 17 which oscillates a pulse signal of specific frequency higher than a power supply signal, a counter circuit 16 which counts a pulse signal in one cycle of a received signal from the reader writer 50, and a comparing circuit 18 which compares one-cycle length of the receive signal obtained according to the count result of the counter circuit 16 with the previously set one-cycle length of the power supply signal and judges that the received signal is a modulated signal when the length is different from that of the power supply signal. When the received signal is the modulated signal, the received signal is demodulated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data carrier for recording (storing) data in an internal memory, which is represented by an IC card such as an ID card, a commuter pass, and a prepaid card. The present invention also relates to a non-contact type data carrier capable of reading and writing data by transmitting and receiving a data signal in a non-contact manner with a reader / writer or the like having a resonance circuit.

[0002]

2. Description of the Related Art A non-contact type data carrier system is a reader / writer which is a reading and rewriting device for reading and rewriting data according to external data communication, and data which is read or rewritten by the reader / writer. And a non-contact type data carrier having an internal memory which is a storage device for storing the data.

The reader / writer includes an oscillator circuit, a modulator circuit,
A reader / writer circuit having a demodulation circuit and a drive circuit and having a basic function, and a resonance circuit that resonates at a predetermined frequency are provided. On the other hand, the non-contact type data carrier receives a power and, at the same time, transmits and receives data, a resonance circuit that resonates at the same frequency as the resonance circuit of the reader / writer,
It has a memory, a rectifier circuit, a modulation circuit, a demodulation circuit, and a control circuit for controlling the overall operation.

The non-contact type data carrier receives the change in frequency and phase as information by utilizing the fact that electromotive force is generated in the resonance circuit of the reader / writer by the electromagnetic field generated from the resonance circuit of the reader / writer. The electromotive force is used as a driving power source for the internal circuit without using a battery. That is, in the contactless data carrier system,
The communication from the reader / writer to the non-contact type data carrier changes the electromagnetic field emitted from the resonant circuit of the reader / writer, and the change of the electromagnetic field changes the electromotive force generated by electromagnetic induction by the resonant circuit of the data carrier. It is done by detecting as.

The data transmitted from the reader / writer is frequency-modulated or phase-modulated by utilizing the change in the frequency or phase of the electromagnetic field generated in the resonant circuit of the reader / writer. This modulated signal can be detected as a frequency shift in the resonance circuit of the non-contact type data carrier, and demodulates the data through the demodulation circuit. There are several methods for the demodulation circuit. Typical methods are a frequency discrimination method using a multivibrator and a delay circuit, and a PLL (Phase Locked Lo) for phase comparison using a voltage controlled oscillator.
op) method.

[0006]

SUMMARY OF THE INVENTION Including the above example,
In the non-contact type data carrier system, in order to efficiently secure the power supply distance and the communication distance to the reader / writer, in order to efficiently secure the power supply distance and the communication distance, the Q (Quality Factor,
It is desirable to adopt a configuration that does not lower the circuit selectivity). However, if Q is larger than a certain level, it becomes susceptible to free vibration of the resonance circuit, and a frequency-modulated or phase-modulated signal represented as an instantaneous frequency shift can be received by the data carrier with only a slight frequency shift. Will end up.

In the conventional modulation circuit system, when it is attempted to detect the above-mentioned slight frequency shift, delicate adjustment of the time constant, the voltage controlled oscillator, etc. is required, which causes a problem in obtaining a stable demodulated signal. There is.

Further, the non-contact type data carrier is required to be miniaturized due to its applicability, and for example, it is desired to make a complicated circuit a dedicated IC. Although there are several methods for forming a dedicated IC, if a general gate array IC composed of only digital circuits is used, naturally the analog circuit portion cannot be incorporated inside the IC. That is, there is also a problem that the time constant circuit and the like are externally attached, which in turn has an adverse effect on downsizing of the non-contact type data carrier.

An object of the present invention is to provide a non-contact type data carrier which can efficiently secure a power supply distance and a communication distance from a reader / writer and can obtain a stable demodulated signal. .

Another object of the present invention is to provide a non-contact type data carrier which is capable of efficiently supplying electric power from a reader / writer and securing a communication distance, and which can be miniaturized.

[0011]

According to the present invention, a resonance circuit that resonates at a predetermined frequency is provided, and a power supply signal of a predetermined frequency is received by electromagnetic induction from a reader / writer that also has the resonance circuit. In a non-contact type data carrier that is supplied with power, receives and transmits a modulation signal based on data to be communicated with a reader / writer by electromagnetic induction, and reads and rewrites data from and to a memory provided inside An oscillation circuit that oscillates a pulse signal having a predetermined frequency higher than the power supply signal, a counter circuit that counts the pulse signal during one cycle of a reception signal from the reader / writer, and a counting result by the counter circuit 1 cycle length of the received signal obtained based on the In comparison, when the received signal is different from the power supply signal, it is determined that the received signal is the modulated signal, and when the received signal is the modulated signal, demodulation processing is performed on the received signal. A contactless data carrier is obtained which is characterized in that

According to the present invention, there is also provided a reader / circuit which includes a resonance circuit which resonates at a predetermined frequency, and which also includes the resonance circuit.
The power is supplied by receiving a power supply signal of a predetermined frequency from the writer by electromagnetic induction, and a modulation signal based on the data to be communicated with the reader / writer is received and transmitted by electromagnetic induction and provided internally. In a non-contact type data carrier that reads and rewrites data from and to a memory, between an oscillation circuit that oscillates a pulse signal having a predetermined frequency higher than the power supply signal and one cycle of a reception signal from the reader / writer. A counter circuit for counting the pulse signal of, and 1 of the received signal obtained based on the count result by the counter circuit.
A comparison circuit that compares a cycle length with a preset one cycle length of the power supply signal, and determines that the received signal is the modulated signal when different from the power supply signal;
The one cycle length of the received signal obtained based on the count result by the counter circuit is monitored, the optimum value is determined from the difference of the one cycle length from the power supply signal for each modulation signal, and the comparison circuit previously And a set value control circuit that rewrites one cycle length of the set power supply signal, wherein when the received signal is the modulated signal, demodulation processing is performed on the received signal. A data carrier is obtained.

Further, according to the present invention, the one-cycle length of the power supply signal preset by the comparison circuit is stored in a memory that can be stored even when the power is not supplied. A type data carrier is obtained.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A contactless data carrier according to an embodiment of the present invention will be described below.

Power is supplied from the reader / writer to the contactless data carrier as follows. In the reader / writer, an electromagnetic field is generated by passing an alternating current having a predetermined frequency in a resonance circuit that resonates at the predetermined frequency. In the non-contact type data carrier, an electromotive force is generated in a resonance circuit that resonates at the same frequency as the reader / writer by electromagnetic induction by an electromagnetic field generated by the reader / writer. This electromotive force is the supplied power. On the other hand, data transmission from the reader / writer to the contactless data carrier is performed as follows. In the reader / writer, an alternating current obtained by frequency-modulating or phase-modulating data to be communicated is passed through the resonance circuit. In the non-contact type data carrier, the data signal to be communicated, which is modulated from the reader / writer in the resonance circuit, that is, the modulation signal is obtained as a change in electromotive force. Needless to say, the cycle of the frequency modulated signal or the phase modulated signal is different from that of the non-modulated signal.

The contactless data carrier of the present invention is provided with a resonance circuit that resonates at a predetermined frequency, similarly to the conventional example, and a power supply signal of a predetermined frequency is electromagnetically supplied from a reader / writer also provided with the resonance circuit. The power is supplied by receiving by induction, and at the same time, the modulation signal based on the data to be communicated with the reader / writer is received and transmitted by electromagnetic induction, and the data is read from and rewritten to the internal memory. It is a thing.

Further, the non-contact type data carrier counts the pulse signal in one cycle of the oscillation circuit which oscillates the pulse signal having the predetermined frequency higher than the power supply signal and the reception signal from the reader / writer. If the counter circuit is different from the power supply signal by comparing the 1 cycle length of the reception signal obtained based on the counting result of the counter circuit with the preset 1 cycle length of the power supply signal And a comparison circuit that determines that the received signal is a modulated signal. Then, demodulation processing is performed on the received signal only when the received signal is a modulated signal.

As described above, when power is supplied from the reader / writer, the contactless data carrier receives a signal of a predetermined frequency. Therefore, basically, it is expected that the count value obtained by the counter circuit will be a predetermined value. In the comparison circuit, a predetermined value is set in advance as a comparison reference and compared with the count value for one cycle of the received signal. As a result of the comparison, if the count value during one cycle of the received signal becomes larger or smaller than the set value, it can be determined that the received signal is a modulated signal, that is, a signal based on data to be communicated.

Hereinafter, a contactless data carrier according to an embodiment of the present invention will be described in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram showing a contactless data carrier system including a contactless data carrier according to a first embodiment of the present invention.

Referring to FIG. 1, the contactless data carrier system has a reader / writer 50 and a contactless data carrier 10. The reader / writer 50 has a reader / writer circuit 51 including an oscillation circuit, a modulation circuit, and a control circuit (not shown), and a resonance circuit 52 that resonates at a predetermined frequency. The contactless data carrier 10 includes a resonance circuit 12, a power supply circuit 13, a waveform shaping circuit 14, a frequency dividing circuit 15, a counter circuit 16, an oscillation circuit 17, a comparison circuit 18, and a comparison value setting circuit 19.
And a demodulation circuit 20.

In this embodiment, the power supply signal is set to 250.
The frequency is set to KHz, and the phase modulation method is used in which the phase of the 250 KHz signal is changed by 180 ° at the change point of the transmission data. Also,
The resonant frequencies of the resonant circuit of the reader / writer 50 and the resonant circuit 12 of the non-contact type data carrier 10 are each 2
It is set to 50 KHz.

The contactless data carrier 10 operates as follows.

An electromagnetic field is generated from the resonance circuit 52 by the reader / writer circuit 51 in the reader / writer 50, and electric power is supplied and a modulation signal is transmitted to the non-contact type data carrier 10.

In the non-contact type data carrier 10, electromotive force is generated in the resonance circuit 12 by electromagnetic induction by the electromagnetic field generated in the resonance circuit 52 of the reader / writer 50, and the power supply circuit 13 is generated.
It is rectified and converted to a constant voltage by and is supplied as a power source for each circuit (not shown).

When the non-contact type data carrier 10 is in the power supply state, the resonance circuit 12 obtains the same 250 KHz signal as the power supply signal. This signal is made into a rectangular wave by the waveform shaping circuit 14 and divided by 2 by the frequency dividing circuit 15. The half cycle of the signal divided by two is one cycle of the signal received by the resonance circuit 12, and is input to the counter circuit 16 as a signal that determines the operation timing of the counter circuit 16.

The counter circuit 16 counts the pulse signal from the oscillation circuit 17 during one cycle of the received signal.
The count result of the counter circuit 16 is compared with the value of the comparison value setting circuit 19 preset by the comparison circuit 18. In this embodiment, the oscillation frequency of the oscillation circuit 17 is set to 4 MHz, so that the signal of 250 KHz in the power supply state, that is, one cycle of 4 μsec, is 4 MHz of the oscillation circuit 17.
Signal, that is, a pulse signal of 0.25 μsec is counted by the counter circuit 16.

In this embodiment, the reader / writer 50 is also used.
When a modulated signal (a signal based on data to be communicated) whose phase is changed by 180 ° is input to the resonance circuit 52 due to the free vibration of the resonance circuit 52 and the resonance circuit 12 of the non-contact type data carrier 10, the reception side Resonant circuit 12
Then, one cycle, which is a slight frequency shift, is 3.5 μsec.
Appears as a signal of.

Therefore, the count value expected by the counter circuit 16 is 16 when there is no modulation in the power supply state.
Since the expected value is 14 at the time of modulation, the setting value of the comparison value setting circuit 19 is set to 15 in consideration of the error. Then, the signal is input to the demodulation circuit 20 only when a value different from the set value of the comparison value setting circuit 19 is input to the comparison circuit 18 from the counter circuit 16.

In the demodulation circuit 20, according to the signal from the comparison circuit 18 indicating the presence or absence of the modulation, when the modulation is present, the demodulation operation of restoring the original data is performed. In the present embodiment, although not shown, two counter circuits 16 and two comparison circuits 18 are provided based on the count timing of one cycle of the received signal obtained by the frequency dividing circuit 15, and each circuit is provided for each cycle. It is configured such that the count of received signals can be continuously measured by switching between.

[Embodiment 2] In each resonance circuit of a reader / writer and a non-contact type data carrier,
Due to variations in the characteristics of components such as coils and capacitors, and the characteristics of peripheral circuits,
In the actual situation, the resonance frequency and Q often differ for each resonance circuit. As a result, even if the modulated signals are based on the same data, the frequency thereof may fluctuate during use of the contactless data carrier, or may change each time it is used.

Therefore, in the second embodiment of the present invention, the one cycle length of the received signal obtained based on the count result by the counter circuit is monitored, and the one cycle length difference from the power supply signal is monitored for each modulated signal. It has been decided to provide a set value control circuit which judges the optimum value and rewrites one cycle length of the power supply signal which is preset by the comparison circuit. That is, by constantly rewriting the set value set in the comparison circuit to the optimum value, stable reception operation is always realized. The set value rewritten by the set value control circuit is also stored in the memory in the non-contact type data carrier. This makes it possible to start the receiving operation on the basis of the stored setting value at the next operation, and always realizes a stable receiving operation.

FIG. 2 is a block diagram showing a contactless data carrier according to the second embodiment of the present invention. Referring to FIG. 2, contactless data carrier 30 is the same as that of the first embodiment.
Similarly to the above, the resonance circuit 32, the power supply circuit 33, the waveform shaping circuit 34, the frequency dividing circuit 35, the counter circuit 36, the oscillation circuit 37, the comparison circuit 38, and the demodulation circuit 40 are included. .

Further, the contactless data carrier 30 is
CPU 39 as a set value control circuit, and EEPROM 4
And 1.

The contactless data carrier 30 operates as follows.

Similar to the first embodiment, the power supply signal and the phase modulation signal supplied from the reader / writer (not shown) at 250 KHz are received by the resonance circuit 32 as electromagnetic induction electromotive force. The power supply signal of the received signals is supplied by the power supply circuit 33 as a power supply for each circuit, although not shown. The received signal is also subjected to waveform shaping by the waveform shaping circuit 34, divided into two by the frequency dividing circuit 35, and input to the counter circuit 36 as a signal for determining the operation timing of the counter circuit 36. The oscillation circuit 37 oscillates a pulse signal of 4 MHz, and the counter circuit 36 outputs 1
Count during the cycle.

Count result value by the counter circuit 36,
That is, one cycle length of the received signal is input to the CPU 39 as the set value control circuit and the comparison circuit 38. CPU39
Then, the count result value, that is, one cycle length of the received signal is constantly monitored, and the optimum one of the power supply signals to be set in the comparison circuit 38 is determined from the difference in the one cycle length from the power supply signal for each modulation signal. The cycle length is determined and output to the comparison circuit 38.

The comparison circuit 38 outputs the reception signal to the demodulation circuit 40 only when a value different from the set value is input from the counter circuit 36. In the demodulation circuit 40, the comparison circuit 18
When there is modulation, a demodulation operation for returning to the original data is performed in accordance with a signal indicating the presence or absence of modulation.

The optimum set value determined by the CPU 39 is stored and updated in the EEPROM 41, which is an internal memory, so that the non-contact type data carrier 30 is restarted after the use of the non-contact type data carrier 30 is stopped and the power supply is cut off. Even at the time, by reading the set value at the time of the previous operation in the EEPROM 41, quick and stable reception can be performed.

[0040]

The non-contact type data carrier according to the present invention generates an oscillation circuit for oscillating a pulse signal having a predetermined frequency higher than the power supply signal and a pulse signal for one cycle of the reception signal from the reader / writer. If the counter circuit for counting and the one cycle length of the received signal obtained based on the count result by the counter circuit are compared with the preset one cycle length of the power supply signal, and the cycle is different from the power supply signal, Is equipped with a comparison circuit that determines that the received signal is a modulated signal. When the received signal is a modulated signal, demodulation processing is performed on the received signal. Can solve the problem that the Q of the resonance circuit fluctuates and appears as a change in one cycle length of the received modulation signal, and it is possible to secure the power supply distance and communication distance from the reader / writer. Of course it can be performed well, stable demodulated signal is obtained. That is, it is possible to demodulate a slight frequency shift of the modulation signal due to the influence of free vibration of the resonance circuit without delicate adjustment of the time constant or the like without lowering the Q of the resonance circuit of itself and the reader / writer.

Further, since the analog circuit part such as the setting of the time constant is not required, the dedicated gate array IC can be used as a dedicated IC. That is, miniaturization is possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a contactless data carrier system including a contactless data carrier according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a contactless data carrier according to a second embodiment of the present invention.

[Explanation of symbols]

 10, 30 Non-contact type data carrier 12, 32 Resonance circuit 13, 33 Power supply circuit 14, 34 Waveform shaping circuit 15, 35 Dividing circuit 16, 36 Counter circuit 17, 37 Oscillation circuit 18, 38 Comparison circuit 19 Comparison value setting circuit 20, 40 Demodulation circuit 41 EEPROM 39 CPU 50 Reader / writer 51 Reader / writer circuit 52 Resonance circuit

Claims (3)

[Claims] 1. A resonance circuit that resonates at a predetermined frequency is provided, and power is supplied by receiving a power supply signal of a predetermined frequency by electromagnetic induction from a reader / writer that also has the resonance circuit. In a non-contact type data carrier that receives and transmits a modulation signal based on data to be communicated between them by electromagnetic induction and reads and rewrites data from and to a memory provided inside, a predetermined value higher than the power supply signal. An oscillation circuit that oscillates a pulse signal of a frequency, a counter circuit that counts the pulse signal during one cycle of the reception signal from the reader / writer, and a reception signal obtained based on the count result by the counter circuit. The one cycle length is compared with a preset one cycle length of the power supply signal, and is different from the power supply signal. And a comparison circuit that determines that the received signal is the modulated signal, and a demodulation process is performed on the received signal when the received signal is the modulated signal. Data carrier. 2. A resonance circuit that resonates at a predetermined frequency is provided, and power is supplied by receiving a power supply signal of a predetermined frequency by electromagnetic induction from a reader / writer that also has the resonance circuit. In a non-contact type data carrier that receives and transmits a modulation signal based on data to be communicated between them by electromagnetic induction and reads and rewrites data from and to a memory provided inside, a predetermined value higher than the power supply signal. An oscillation circuit that oscillates a pulse signal of a frequency, a counter circuit that counts the pulse signal during one cycle of the reception signal from the reader / writer, and a reception signal obtained based on the count result by the counter circuit. The one cycle length is compared with a preset one cycle length of the power supply signal, and is different from the power supply signal. In such a case, a comparison circuit that determines that the received signal is the modulated signal and one cycle length of the received signal obtained based on the count result by the counter circuit are monitored, and a power supply signal is generated for each modulated signal. And a set value control circuit that rewrites the one cycle length of the power supply signal that is preset by the comparison circuit and determines the optimum value from the difference between the one cycle length and A non-contact type data carrier characterized by performing demodulation processing on the received signal in some cases. 3. The contactless device according to claim 2, wherein one cycle length of the power supply signal preset by the comparison circuit is stored in a memory that can be stored even when the power is not supplied. Type data carrier.