JP3990100B2 - Non-contact information recording medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-contact information recording medium that uses amplitude modulation (AM modulation) with a low degree of modulation and reads / writes information based on electromagnetic coupling, and in particular, can easily perform demodulation of information. In addition, the present invention relates to a non-contact information recording medium capable of setting the withstand voltage of the element low.
[0002]
[Prior art]
A non-contact information recording medium used as an operating power source by generating an electromagnetic induction by generating a crossing magnetic field with radio waves received from an external device (not shown), that is, a power source such as a battery, etc. A non-contact information recording medium for reading / writing information recorded in a non-volatile memory in a non-contact manner has been conventionally devised and used for various purposes.
[0003]
FIG. 5 is a block diagram showing the configuration of a conventional non-contact information recording medium, in which 51 is a transmission / reception antenna for transmitting and receiving radio waves, C1 is a resonance capacitor, 52 is a rectifier circuit comprising a smoothing capacitor C2 and a diode D1, and 53 is A shunt regulator for suppressing the voltage generated by electromagnetic induction to a constant voltage, 54 a demodulation circuit for demodulating input data, and 55 a control for controlling a read / write operation based on the data output from the demodulation circuit 54 Logic, 56 is a non-volatile memory for storing data, 57 is a clock supply circuit for supplying a system clock obtained based on the frequency of a radio wave received from an external device (not shown) to the control logic 55, and 58 is non-volatile This is a modulation circuit that modulates radio waves supplied from an external device based on data read from the memory 56.
[0004]
In a non-contact information recording medium that demodulates and modulates data using amplitude modulation (AM modulation) with a low modulation degree of about 10%, a cross magnetic field obtained from electromagnetic induction generated by an electromagnetic field of a received radio wave is obtained. Rectification is performed by the rectifier circuit 52 to generate a voltage. Thus, operating power is obtained, and the demodulated circuit 54 demodulates the received data based on the power obtained by being suppressed to a predetermined voltage by the shunt regulator 53 as a power supply circuit.
[0005]
That is, the non-contact information recording medium is electromagnetic induction generated inside the non-contact information recording medium in accordance with a change in a communication distance (about 10 cm) between an external device (not shown) for supplying radio waves and the non-contact information recording medium. The power obtained by electromagnetic induction varies greatly. For this reason, for example, a circuit such as the shunt regulator 53 needs to be built in the non-contact information recording medium as a circuit that absorbs voltage fluctuation due to a current change caused by electromagnetic induction. However, the shunt regulator 53 alone makes it difficult to demodulate data because the shunt regulator 53 absorbs power fluctuations caused by electromagnetic induction, that is, voltage fluctuations and suppresses them to a constant voltage. Therefore, conventionally, a resistor R1 is incorporated in series with the shunt regulator 52, and a change in voltage obtained by electromagnetic induction is taken out via the resistor R1 and supplied to the demodulation circuit 54.
[0006]
[Problems to be solved by the invention]
Since the conventional non-contact information recording medium has the above configuration, it depends on the change in the distance between the external device and the non-contact information recording medium, and also on the strength of the radio wave supplied from the external device. Thus, the magnitude of electromagnetic induction generated inside the non-contact information recording medium also varies. For example, when the distance between the external device and the non-contact information recording medium is close, and the current obtained by electromagnetic induction greatly fluctuates, the voltage fluctuation accompanying the fluctuation of the current also increases (see the dotted line in FIG. 3). There is a problem that it is necessary to incorporate a high-breakdown-voltage diode D1 in the rectifier circuit 52, and it is difficult to stably execute data read / write operations.
[0007]
The present invention has been made in order to solve the above-described problems. The electromagnetic induction is performed according to the change in the distance between the external device and the non-contact information recording medium and according to the intensity of the radio wave supplied from the external device. Even if the generated current fluctuates greatly, it is possible to absorb current fluctuation, stably execute data read / write operations, and set the diode withstand voltage of the diode in the rectifier circuit low. An object of the present invention is to provide a non-contact information recording medium.
[0008]
[Means for Solving the Problems]
A non-contact information recording medium according to the present invention receives a radio wave supplied from an external device, rectifies a current obtained by electromagnetic induction generated from the radio wave, and fluctuation of an input current obtained from the rectifier circuit A logarithmic characteristic shunt regulator that generates an input voltage in response to a logarithmic characteristic, and a memory for obtaining a predetermined constant voltage from the input voltage obtained by the logarithmic characteristic shunt regulator and storing data A series regulator supplied to the circuit, a demodulating circuit that compares the input voltage obtained from the logarithmic characteristic shunt regulator with a preset reference voltage and generates data to be output to the memory circuit, and reads from the memory circuit And a modulation circuit that modulates radio waves supplied from an external device according to the data stored in the external Based on the power obtained by radio waves placed al supply, and performs read / write of data to the memory circuit.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described.
[0013]
Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration of a non-contact information recording medium according to Embodiment 1 of the present invention, in which 1 is a transmission / reception antenna that transmits and receives radio waves, C1 is a resonance capacitor, 2 is a smoothing capacitor C2, and a diode D2. A rectifier circuit 3 is a power supply circuit. Reference numeral 31 is a logarithmic characteristic shunt regulator that obtains an input voltage in a logarithmic response to a change in input current obtained by electromagnetic induction caused by received data. Reference numeral 32 denotes a series regulator that absorbs voltage fluctuations caused by electromagnetic induction and supplies a predetermined voltage. The power supply circuit 3 includes a logarithmic characteristic shunt regulator 31 and a series regulator 32. Reference numeral 4 denotes a demodulation circuit that demodulates received data. Reference numeral 41 is a comparator in the demodulation circuit 4, 5 is a control logic, 6 is a non-volatile memory for storing data, 7 is a control logic for a system clock obtained based on the frequency of radio waves transmitted from an external device (not shown). Reference numeral 5 denotes a clock supply circuit to be supplied to 5, and reference numeral 8 denotes a modulation circuit that modulates radio waves supplied from an external device based on data read from the nonvolatile memory 6.
[0014]
2 is a circuit diagram showing the configuration of the logarithmic characteristic shunt regulator 21 and the series regulator 32 in the non-contact information recording medium of Embodiment 1 shown in FIG. 1, wherein (a) is a logarithmic characteristic shunt regulator, and (b). Indicates a series regulator. In FIG. 2A, reference numerals 21, 22, and 23 denote MOSFETs, which are connected in parallel to each other with respect to the input current Iin.
[0015]
FIG. 3 is an explanatory diagram showing current-voltage characteristics of the logarithmic characteristic shunt regulator 31 shown in FIG. The logarithmic characteristic shunt regulator 31 is a shunt regulator having characteristics approximating a logarithmic characteristic with respect to fluctuations in the input current Iin, utilizing the gate voltage VG versus drain current ID characteristic of the MOSFET 21. As shown in FIG. 3, the logarithmic characteristic shunt regulator 31 can always output a constant voltage Vin even when the input power Iin obtained from the received electromagnetic field greatly fluctuates.
[0016]
On the other hand, the series regulator 32 shown in FIG. 2B is for supplying a constant voltage to the control logic 5 and the nonvolatile memory 6. For example, even when the voltage of the node N4 fluctuates with the fluctuation of the distance between the external device (not shown) and the non-contact information recording medium or with the fluctuation of the intensity of the radio wave transmitted from the external device, The voltage at the node N5 maintains a constant value. The voltage of the node N5 in the series regulator 32 is supplied to the control logic 5 and the nonvolatile memory 6 as shown in FIG.
[0017]
By the way, in the conventional non-contact information recording medium shown in FIG. 5, the crossing magnetic field obtained from the electromagnetic induction generated by the electromagnetic field of the received radio wave is rectified by the rectifier circuit 52 to obtain the input current, and the resistance Since the configuration is such that a DC voltage is obtained as an input voltage corresponding to the radio wave input through R1, the input voltage Vin increases in proportion to the increase in the input current obtained by electromagnetic induction, as shown by the dotted line in FIG. .
[0018]
Therefore, compared with the conventional non-contact information recording medium having the configuration shown in FIG. 5, the non-contact information recording medium of the first embodiment having the configuration shown in FIG. Since the input voltage Vin corresponding to the received radio wave can be obtained while suppressing the influence due to fluctuation, the radio wave supplied from the external device according to the change in the distance between the external device and the non-contact information recording medium. Even when the input current Iin generated by electromagnetic induction varies greatly according to the intensity of the signal, the fluctuation of the input current Iin can be absorbed and the data read / write operation can be performed stably. In addition, since the logarithmic characteristic shunt regulator 31 is incorporated, the fluctuation of the input voltage Vin can be absorbed even when the fluctuation of the input current Iin occurs, so that the element breakdown voltage of the diode D2 in the rectifier circuit 2 is set low. Can do.
[0019]
Embodiment 2. FIG.
FIG. 4 is a block diagram showing a configuration of a non-contact information recording medium according to Embodiment 2 of the present invention, in which 31 is a logarithmic characteristic shunt regulator shown in FIGS. 1 and 2A, 41 is a comparator, Reference numeral 42 denotes a DC regeneration circuit (DC clamp circuit). The comparator 41 and the DC regeneration circuit 42 constitute a demodulation circuit 43. The demodulation circuit 43 corresponds to the demodulation circuit 4 shown in FIG. Other constituent elements are the same as those of the non-contact information recording medium of Embodiment 1 shown in FIG. 1, and are not shown here.
[0020]
In the non-contact information recording medium of Embodiment 2 shown in FIG. 4, a logarithmic characteristic shunt regulator accompanies electromagnetic induction of radio waves from an external device (not shown) received via the transmitting / receiving antenna 1, that is, received data. The input voltage Vin is obtained by 31. The input voltage Vin is binarized by reproducing the DC component of the data as a voltage via a DC reproducing circuit 41 (DC clamp circuit) and comparing the obtained voltage with a reference voltage by the comparator 42. Then, the binarized data as a comparison result is output to the control logic 5 (see FIG. 1, not shown in FIG. 4). Therefore, for example, it is possible to demodulate radio waves having DC data such as NRZ codes, and the non-contact information recording medium of the present invention can be applied to a wide range of fields.
[0021]
【The invention's effect】
As described above, the non-contact information recording medium of the present invention is a non-contact information recording medium that performs demodulation / modulation of data using amplitude modulation with a low degree of modulation. Power fluctuations obtained by electromagnetic induction, that is, fluctuations in the current of the input signal are absorbed by a logarithmic characteristic shunt regulator having characteristics approximating to the logarithmic characteristics, so that the input power fluctuations are always constant. The voltage output of the received data can be obtained, and the data write / read operation can be executed stably.
[0022]
In addition, compared with a conventional non-contact information recording medium using a normal shunt regulator and a resistor, the non-contact information recording medium of the present invention receives a received signal while keeping the DC voltage obtained by rectification low. Therefore, there is an effect that the element breakdown voltage of the diode constituting the rectifier circuit can be set low.
[0023]
In addition, since the logarithmic characteristic shunt regulator is configured by using the gate voltage versus drain current characteristic of the MOSFET, a characteristic approximating the logarithmic characteristic can be easily obtained.
[0024]
Further, the DC component of the voltage of the received data is reproduced through a DC reproduction circuit (DC clamp circuit), and the reproduced voltage is binarized by comparing it with a reference voltage by a comparator as a voltage comparator. Therefore, it is possible to demodulate data having a direct current component such as an NRZ code, and there is an effect that a wide range of applications are possible depending on the application.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a non-contact information recording medium according to Embodiment 1 of the present invention.
2 is a circuit diagram showing a configuration of a logarithmic characteristic shunt regulator and a series regulator in the non-contact information recording medium shown in FIG. 1. FIG.
FIG. 3 is an explanatory diagram showing operating characteristics of the logarithmic characteristic shunt regulator shown in FIGS. 1 and 2;
FIG. 4 is a block diagram showing a configuration of a non-contact information recording medium according to Embodiment 2 of the present invention.
FIG. 5 is a block diagram showing a configuration of a conventional non-contact information recording medium.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Transmission / reception antenna, 2 Rectifier circuit, 3 Power supply circuit, 4,43 Demodulation circuit, 5 Control logic, 6 Non-volatile memory, 7 Clock supply circuit, 8 Modulation circuit, 31 Logarithmic characteristic shunt regulator, 32 Series regulator, 41 Comparator, 42 DC regeneration circuit (DC clamp circuit).

Claims (1)

A rectifier circuit that receives a radio wave supplied from an external device and rectifies a current obtained by electromagnetic induction generated from the radio wave;
A logarithmic characteristic shunt regulator that generates an input voltage in response to a logarithmic characteristic in response to a variation in input current obtained from the rectifier circuit;
A series regulator that obtains a predetermined constant voltage from the input voltage obtained by the logarithmic characteristic shunt regulator and supplies it to a memory circuit for storing data;
A demodulation circuit that compares the input voltage obtained from the logarithmic characteristic shunt regulator with a preset reference voltage and generates data to be output to the memory circuit;
A modulation circuit that modulates radio waves supplied from an external device by data read from the memory circuit,
A non-contact information recording medium that reads / writes data to / from the memory circuit based on electric power obtained by radio waves supplied from the external device without incorporating a battery.

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