JP2000082118A - Data writing device and data reader/writer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data writing device or the like which can hold a sufficient communication distance even when a power source of a low voltage such as a battery is used in a non-contact type IC card system. SOLUTION: A transmission circuit of a data writing device has a battery and a transmission side amplifying circuit 32 which is supplied with voltage from this battery and drives a loop antenna. The transmission side amplifying circuit 32 is equipped with a boosting circuit 42 consisting of a frequency division circuit 41 for frequency dividing a modulation signal (CLK) modulating transmission data by using a clock, a voltage shifter 43 for shifting a level of the frequency divided modulation signal in a direct-current manner and a maximum value holding circuit 44 for holding a peak value of the level shifted modulation signal. This transmission side amplifying circuit 32 generates a DC voltage higher than a power source voltage by the boosting circuit and amplifies the modulation signal by using this DC voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data writing device and a data reading / writing device for writing data by supplying an electromagnetic wave to a non-contact recording medium.

[0002]

2. Description of the Related Art In recent years, in fields such as automatic ticket gates, security systems, and electronic money systems, non-contact ICs have been developed.
A contactless card system using a card has been introduced.

This non-contact type card system comprises an IC card as a recording medium and a card reading / writing device for reading and writing data from and to the IC card. In this contactless card system, communication between the IC card and the card reading / writing device is performed using, for example, electromagnetic waves. In such a non-contact type card system, it is not necessary to load or contact an IC card with a card reading / writing device as in a conventional contact type card system, and it is possible to read data easily and quickly. Can write.

In such a non-contact type IC card system, power is supplied to the IC card by electromagnetic waves transmitted from a card reading / writing device.
There is no need to have a power source such as a battery in the card, and low cost I
C card can be provided. However, the card reading / writing device must output electromagnetic waves with a certain strength in order to secure a sufficient communication distance with the IC card.

[0005]

By the way, in the above-mentioned non-contact type card system, a small and portable card reading / writing device is required.

However, when the card reading / writing device is made portable, the transmitting circuit must be driven by a low-voltage power source such as a battery to transmit an electromagnetic wave to the IC card. Therefore, in such a miniaturized portable card reading / writing device, an electromagnetic wave is amplified by a low-voltage power supply such as a battery, so that an electromagnetic wave having a large amplitude cannot be output, and the communication distance is short. There was a problem of becoming.

The present invention has been made in view of such circumstances, and a data writing device capable of maintaining a sufficient communication distance even when a low-voltage power supply such as a battery is used. And a data reading / writing device.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a power supply for supplying a DC voltage, a modulation signal generated by modulating transmission data, and an amplitude of the modulation signal which is converted by the power supply. It is characterized in that it is amplified to a voltage amplitude higher than the voltage value supplied from, and data is transmitted by electromagnetic waves.

In the present invention, the amplitude of the modulation signal is amplified to a voltage amplitude higher than the voltage value supplied from the power supply, and data is transmitted by electromagnetic waves.

According to the present invention, for example, data is transmitted by electromagnetic waves using means having a booster for boosting a voltage supplied from a power supply and an amplifier for amplifying data with the voltage boosted by the booster. .

According to the present invention, for example, the level of a modulated signal is DC-shifted, and the level of the level-shifted signal is high and low, and the level of the level-shifted signal is not shifted. And data is transmitted by electromagnetic waves using a means for generating a signal having a voltage amplitude higher than the voltage value supplied from the power supply.

According to the present invention, for example, a switching section for switching a power supply voltage supplied from the power supply in accordance with a modulation signal, an antenna for emitting an electromagnetic wave in accordance with the switching of the switching section, and a current value flowing through the antenna are provided. A means having a control unit for controlling, by linearly decreasing the current value of the current flowing to the antenna when the switching unit is off, and setting the current value of the current flowing to the antenna to 0 when switching from off to on. The data is transmitted by the electromagnetic wave obtained by this.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of a contactless IC card system to which the present invention is applied.

The non-contact type IC card system 1 includes an IC card 2 serving as a recording medium and a card reading / writing device 3 for reading and writing data from and to the IC card 2.

The IC card 2 is a batteryless IC card having no power supply source such as a battery, and has a rectangular plate shape, for example, in a size that can be put on a palm.
The IC card 2 has a loop antenna 11 for transmitting and receiving electromagnetic waves, a nonvolatile memory 12 for storing data, and a nonvolatile memory 12
A control circuit 13 for controlling writing and reading of data to and from the modem; a modulation and demodulation circuit 14 for demodulating a signal received by the loop antenna 11 or modulating data to be transmitted by the loop antenna 11; And a power supply circuit 15 for conversion.

The loop antenna 11 transmits and receives electromagnetic waves to and from the card reading / writing device 3.

The nonvolatile memory 12 stores data transmitted from the card reading / writing device 3.

The control circuit 13 includes the card reading / writing device 3
The data transmitted from the card reading / writing device 3 is written into the nonvolatile memory 12 in accordance with the control command supplied from the storage device, and the data transmitted to the card reading / writing device 3 is read from the nonvolatile memory 12. .

The modulation / demodulation circuit 14 demodulates a signal received from the card reading / writing device 3 via the loop antenna 11 and also transmits data to be transmitted to the card reading / writing device 3 via the loop antenna 11 to a predetermined value. Is modulated by using the carrier wave.

The power supply circuit 15 includes the card reading / writing device 3
Is converted into stable DC power and supplied to each circuit of the IC card 2.

On the other hand, the card reading / writing device 3 is, for example, a portable portable device that can be carried by a user. The card reader / writer 3 includes a loop antenna 21 for transmitting / receiving electromagnetic waves, a control circuit 22 for controlling data to be transmitted / received, and a transmitting / receiving circuit 23 for modulating / demodulating data and amplifying a signal to be transmitted. , DC power supply 2
4, an input circuit 25, and a display circuit 26.

The loop antenna 21 transmits and receives electromagnetic waves to and from the IC card 2.

The control circuit 22 performs, for example, processing and control of data to be transmitted and received, display control for the display circuit 26, input control for the input circuit 25, and the like according to a built-in program. The control circuit 22 controls the IC card 2
The transmission data to be transmitted to the
The reception data received from the card 2 is obtained from the transmission / reception circuit 23.

As shown in FIG. 2, the transmission / reception circuit 23 is supplied with a clock having a predetermined frequency as a carrier wave, modulates the clock with transmission data from the control circuit 22, and amplifies the modulated signal. And a transmission-side amplifier circuit 32. Further, the transmission / reception circuit 23 includes a demodulation circuit 33 for demodulating a signal received via the loop antenna 21, a filter circuit 34 for filtering the demodulated signal, and a reception-side amplifier for amplifying the filtered signal and outputting received data. And a circuit 35.

In the transmission / reception circuit 23, the transmission data supplied from the control circuit 22 is modulated by the modulation circuit 31 using a predetermined clock, and the modulated signal is amplified by the transmission-side amplifier circuit 32. Then, the amplified signal is transmitted to the loop antenna 21.
Is transmitted by electromagnetic waves through the. Also, the transmission / reception circuit 23
The demodulation circuit 33 demodulates a signal received from the card reading / writing device 3 via the loop antenna 21, filters the demodulated signal by the filter circuit 34, and amplifies the filtered signal by the reception side amplification circuit 35. Are supplied to the control circuit 22 as reception data.

The DC power supply 24 is composed of, for example, a battery and supplies a DC voltage having a predetermined voltage value (VDD volt) to each circuit in the card reading / writing device 3.

In the non-contact type IC card system 1 configured as described above, communication between the IC card 2 and the card reading / writing device 3 is performed using electromagnetic waves, and data is transmitted to the IC card 2. Writing and reading are performed.

Here, each circuit of the transmission / reception circuit 23 includes:
A DC voltage of VDD volts is supplied from the DC power supply 24 to operate. Further, the clock and the transmission data supplied to the transmission / reception circuit 23 are digital signals that take binary values from 0 volt to VDD. For example, it is a binary digital signal having values of 0 volt and VDD volt.

On the other hand, the amplified signal output from the transmission-side amplifier circuit 32 is boosted to a voltage value (H-VDD volt) that is higher than the power supply voltage (VDD volt). For example, the transmission side amplifier circuit 32 is, for example, 0 volts and 2 ×
It becomes a digital signal that takes a binary value of VDD volts.

Next, the amplitude of the modulation signal (CLK) supplied from the modulation circuit 31 is set to HV higher than VDD volt.
The transmission side amplification circuit 32 for amplifying to DD volts will be described in more detail.

The transmitting-side amplifier circuit 32 amplifies the modulation signal (CLK) by, for example, the following first to third amplification methods.

First, the first amplification method will be described.

The first amplification method is a method in which a DC voltage of VDD volts supplied from the DC power supply 24 is boosted, and the modulation signal is amplified by the boosted voltage.

FIG. 3 shows a circuit example of the transmission-side amplifier circuit 32 to which the first amplification method is applied.

In the transmission-side amplifier circuit 32 to which the first amplification method is applied, the amplitude of the modulated signal (C
LK) is divided by the frequency dividing circuit 41 to a frequency of 1 / N.
The boosting circuit 42 boosts the modulation signal divided by the frequency dividing circuit 41 to H-VDD volt higher than VDD volt.
The configuration of the booster circuit 42 may be any configuration such as a charge pump circuit and a switching converter. For example, as shown in FIG. 3, a voltage shifter 43,
The booster circuit 42 may be configured by the maximum value holding circuit 44.

In this case, the voltage shifter 43
As shown in FIG. 3A, a modulation signal having two values of 0 volt and VDD volt is supplied. The voltage shifter 43 shifts the level of the modulation signal in a DC manner.
As shown in FIG. 4B, a signal that takes two values of VDD volt and 2 VDD volt is output. Then, the maximum value holding circuit 44 holds and smoothes the peak value of 2VDD, and outputs a DC voltage of 2VDD volts as shown in FIG. Although the frequency dividing circuit 41 divides the frequency of the modulation signal in order to improve the boosting efficiency, the frequency dividing circuit 41 may divide the frequency of the carrier signal, or may multiply the frequency instead of dividing the frequency. .

In the transmission-side amplifier circuit 32 to which the first amplification method is applied, the modulation signal (CLK) is amplified by the preamplifier 45 in the range of the power supply voltage (VDD).
Then, the voltage (H-VD
D) is supplied to the power amplifier 46 as a power supply voltage, and the modulated signal amplified by the preamplifier circuit 45 is boosted by the booster circuit 42 by the power amplifier 46 to a voltage (HV)
DD).

In the transmission-side amplifier circuit 32 to which the first amplification method is applied, a sufficient signal amplitude can be obtained in the final amplification stage, and the loop antenna 21 is driven by the signal amplitude. 21 can generate an electromagnetic field of sufficient strength.

FIGS. 5 to 8 show specific examples of the circuit configuration of the booster circuit 42. FIG.

The booster circuit 42 shown in FIG.
LK), a first diode 52a having an anode connected to the power supply terminal (VDD), and a second diode connected between the output of the buffer circuit 51 and the cathode of the first diode 52a. A first capacitor 53a, a second diode 52b connected between the cathode of the first diode 52a and the output terminal, and a second capacitor 53b connected between the output terminal and the ground. Thus, a DC voltage (H-VDD) higher than the power supply voltage (VDD) is output from the output terminal.

The booster circuit 42 shown in FIG.
LK) and a power supply terminal (VD
D) a first on / off switch 55a and a second on / off switch 55b connected in series between
And a third on / off switch 55c and a first capacitor 56a connected in series between the terminals of the second on / off switch 55b, and an output terminal between the terminals of the third on / off switch 55c. The fourth ON /
It comprises an off switch 55d and a second capacitor 56b. The first ON / OFF switch 55a and the third ON / OFF switch 55c are connected to the modulation signal (CL
On / off based on K). Also, a second on / off switch 55b and a fourth on / off switch 55d
Is a modulation signal (CL) inverted by the inverter 54.
On / off based on K). Therefore, the first and third on / off switches 55a, 55c and the second and fourth
The on / off switches 55b and 55d have inverted logic. In such a booster circuit 42, a DC voltage (H-VDD) higher than the power supply voltage (VDD) is output from the output terminal.

The booster circuit 42 shown in FIG.
, Capacitor 62, output terminal 63, capacitor 6
A first switch 64 for connecting one end of the capacitor 62 to the input terminal 61 and the ground, and a second switch 65 for connecting the other end of the capacitor 62 to the power supply terminal (VDD) and the output terminal 63 for connection. Are connected in series. In these units 60, the first switch 64 is switched by the modulation signal (CLK). For example, when this modulation signal goes high, one end of the capacitor 62 is connected to the input terminal 61, and when this modulation signal goes low, the capacitor is switched. One end of 62 is connected to the ground. In the unit 60, the second switch 65 is switched by the modulation signal (CLK). For example, when the modulation signal goes high, the other end of the capacitor 62 is connected to the output terminal 63, and when the modulation signal goes low. One end of the capacitor 62 is connected to a power supply terminal. In addition, the booster circuit 42 includes a capacitor 62 having one end connected to the ground, an output terminal 63, and the other end of the capacitor 62 connected to a power supply terminal (VDD) at the input side end of the plurality of units 60 connected in series. ) And a second switch 65 connected to the output terminal 63 by switching. Further, the booster circuit 42 has an input terminal 61 at an output-side end of the plurality of units 60 connected in series.
And an output terminal 63 directly connected to the input terminal 61, and a capacitor 6 connected between the output terminal 63 and the ground.
8 is connected. In such a booster circuit 42, each switch has a modulation signal (CL
K), and outputs a DC voltage (H-VDD) higher than the power supply voltage (VDD) from the output terminal 63 of the output unit 67.

The booster circuit 42 shown in FIG. 8 has a coil 71 whose one end is connected to a power supply terminal (VDD), and an on / off connection connected between a terminal of the coil 71 to which the power supply terminal is not connected and the ground. A switch 72, a diode 73 having an anode connected to a terminal of the coil 71 not connected to the power supply terminal and a cathode connected to the output terminal, a capacitor 74 connected between the output terminal and the ground, And a control unit 75 that controls the on / off switch 72 based on the output voltage. When the on / off switch 72 is switched, the booster circuit 42 switches the DC voltage (H) higher than the power supply voltage (VDD).
-VDD) from the output terminal.

Next, the second amplification method will be described.

In the second amplification method, the modulation signal (CLK)
Is level-shifted in a direct current manner, and the level-shifted voltage is used every half cycle of the modulation signal to amplify the modulation signal.

FIG. 9 shows a block diagram of a transmission side amplifier circuit 32 to which the second amplification system is applied.

The transmission-side amplifier circuit 32 to which the second amplification method is applied is a modulation signal (CL) having an amplitude of not more than VDD volts.
K) a voltage shifter 8 for shifting the voltage by a predetermined voltage
1 and a power amplifier 82 for amplifying the modulation signal by the output of the voltage shifter 81.

As shown in FIG. 10A, a modulation signal having two values of 0 volt and VDD volt is supplied to the voltage shifter 81. The voltage shifter 81 shifts the level of the modulation signal in a DC manner, for example, as shown in FIG.
As shown in (1), a signal having two values of VDD volt and 2 VDD volt is output. Here, the power amplifier 82
As shown in FIG. 10C, the output is set to 0 volt while the voltage shifter 81 is outputting the voltage of VDD volt,
While the voltage shifter 81 is outputting a voltage of 2 VDD volts, it has a switching means for outputting an output amplified based on the voltage of 2 VDD volts. Therefore, in the power amplifier 82, as shown in FIG. 10D, the power supply voltage (VD
D) An output signal having a higher voltage (H-VDD) amplitude can be obtained.

In the transmission-side amplifier circuit 32 to which the second amplification method is applied, a sufficient signal amplitude can be obtained in the final amplification stage, and the loop antenna 21 is driven by the signal amplitude. 21 can generate a sufficient electromagnetic field.

By connecting the above-described configuration of the voltage shifter 81 and the power amplifier 82 in N stages, for example, an output signal N + 1 times the power supply voltage can be obtained.

FIGS. 11 to 12 show the transmission side amplifier circuit 32.
An example of a specific circuit configuration is shown below.

The transmitting-side amplifier circuit 32 shown in FIG. 11 is driven by a power supply voltage (VDD) to invert a modulation signal (CLK) and a first inverter circuit 83a having an anode connected to a power supply terminal (VDD). The first diode 84a, the output of the first inverter circuit 83a and the first diode 8a
4a connected to the cathode of the first capacitor 8a
5a, and a second inverter circuit 83b driven by a voltage from the cathode of the first diode 84a and inverting the modulation signal (CLK). The first diode 84a and the first capacitor 85a form a clamp circuit. The modulation signal buffered by the first inverter circuit 83a is clamped at the power supply voltage (VDD) by the clamp circuit, and the power supply voltage (VD
D) and a signal that takes a binary value between twice the power supply voltage (2VDD). Further, the first inverter 83b outputs an output of 2 to the clamp circuit in accordance with the phase of the modulation signal (CLK).
The output voltage of the clamp circuit is output during the period of the double power supply voltage (2VDD), and the output of the clamp circuit is the power supply voltage (V
During the same period as DD), the ground level is output.

The transmission side amplifier circuit 32 shown in FIG. 12 is driven by a power supply voltage (VDD) to invert a modulation signal (CLK) and a first inverter circuit 83a having an anode connected to a power supply terminal (VDD). The first diode 84a, the output of the first inverter circuit 83 and the first diode 84a.
a capacitor 85 connected between the first capacitor 85
a, a second inverter circuit 83b driven by a voltage from the cathode of the first diode 84a to invert the modulation signal (CLK), a second diode 84b having an anode connected to the power supply terminal (VDD), A second capacitor 85b connected between the output of the second inverter circuit 83b and the cathode of the second diode 84b;
And a third inverter circuit 83c driven by a voltage from the cathode of the diode 84b to invert the modulation signal (CLK). The transmission side amplifier circuit 32 shown in FIG. 12 is a circuit in which the circuit shown in FIG. 11 is connected in two stages. The transmission-side amplifier circuit 32 shown in FIG. 12 outputs a signal having an amplitude of three times the power supply voltage (3VDD).

Next, the third amplification method will be described.

In the third amplification method, the loop antenna 21
Is a method of amplifying a modulation signal by using a back electromotive force generated in the above.

FIG. 13 shows a circuit diagram of a transmission side amplifier circuit 32 to which the third amplification system is applied.

The transmission-side amplifier circuit 32 to which the third amplification system is applied has a switch 91 for switching the connection point at one end of the loop antenna 21 functioning as a coil antenna. This switch 91 has one switching point 91
a is connected to the DC power supply 24 and the other switching point 91b
Are connected to the DC power supply 24 via the current source 92.
Further, the transmission side amplifier circuit 32 includes a switch control signal Scnt for switching the switch 91 and the loop antenna 2.
Current control signal Sc for controlling the current Icoil flowing in 1
The control circuit 93 outputs nt.

Here, when the inductance of the loop antenna 21 is L and the power supply voltage is VDD,
The operation of the transmission side amplifier circuit 32 will be described.

As shown in FIG. 14A, the control circuit 93
Outputs a switch control signal Scnt that is turned on during the time T1 and turned off during the time T2. The switch 91 is
When the switch control signal Scnt is on, it is switched to the terminal 91a, and when it is off, it is switched to the terminal 91b. The current flowing through the loop antenna 21 is shown in FIG.
As shown in (b), when the switch control signal Scnt is in the ON period, it increases at the rate of increase of VDD / L. Also,
When the switch control signal Scnt is in the OFF period, the control circuit 93 controls the current source 92 so that T1 × VDD /
The current flowing through the loop antenna 21 is reduced at a reduction rate of (T2 × L). The current value of the current flowing through the loop antenna 21 is T1 × VDD / L when switching from the terminal 91a to the terminal 91b, and becomes 0 when switching from the terminal 91b to the terminal 91a.

When the voltage and the current are supplied to the loop antenna 21 as described above, as shown in FIG. 14C, when the switch control signal Scnt is on, the voltage VDD is applied to the loop antenna 21 and the switch control signal Scn
When t is off, back electromotive force-VDD × T1 / T2 is generated. Therefore, in the transmission side amplifier circuit 32, an output signal having an amplitude of the voltage (H-VDD) higher than the power supply voltage (VDD) can be obtained, and the loop antenna 21 is driven with a sufficient signal amplitude. Antenna 2
1 can generate a sufficient electromagnetic field.

As shown in FIG. 15A, the ON period and the OFF period of the switch control signal Scnt are set to the same T1 time. Then, as shown in FIG. 15B, the increase rate and the decrease rate of the current flowing through the loop antenna 21 become the same. Therefore, as shown in FIG. 15C, the back electromotive force generated when the switch control signal Scnt is off is −VD
D, and the loop antenna 21 has a period of 2 × T1 ±
A rectangular wave having an amplitude of VDD is applied. This is equivalent to driving the loop antenna 21 with a rectangular wave having twice the amplitude of the power supply voltage.

FIG. 16 shows a specific example of the circuit configuration of the transmission side amplifier circuit 32.

The transmission side amplifier circuit 32 shown in FIG.
T95 and a control circuit 96 for controlling the gate voltage of the FET 95.

The loop antenna 21 has a DC power supply 2 at one end.
4 and the other end is connected to the drain of the FET 95. The source of the FET 95 is grounded.

The control circuit 96 is supplied with a modulation signal (CLK). The control circuit 96 supplies the modulated signal (C
LK), a switch control signal Scnt as shown in FIG. 17A is supplied to the gate of the FET 95, and FIG.
A current as shown in (b) is supplied to the loop antenna 21. That is, while the modulation signal (CLK) is on, a sufficiently high constant voltage value is applied to the gate of the FET 95 so as not to affect the current value determined by the inductance of the loop antenna 21. Subsequently, the modulation signal (CLK)
During the period when the current is flowing through the loop antenna 21 is constant, and the voltage at which the current value becomes 0 at the end of the period during which the modulation signal (CLK) is turned off ends.
Give to the gate. By performing such control, as shown in FIG. 17C, the back electromotive force generated when the switch control signal Scnt is off is −VDD, and the loop antenna 21 has a period of 2 × T1 and ± VDD. A rectangular wave having an amplitude is applied, and the loop antenna 21 can be driven by a rectangular wave having an amplitude twice as large as the power supply voltage.

As described above, in the card reading / writing device 3, the loop antenna 21 can be driven with an output voltage higher than the power supply voltage by applying the first to third amplification methods. Therefore, in the card reading / writing device 3, even when a low-voltage power source such as a battery is used as the DC power source 24, data is read while maintaining a sufficient communication distance with the non-contact type IC card 2. And can write.

[0068]

According to the present invention, the amplitude of the modulation signal is amplified to a voltage amplitude higher than the voltage value supplied from the power supply, and data is transmitted by electromagnetic waves.

Thus, according to the present invention, even when a low-voltage power supply such as a battery is used, a sufficient communication distance with a non-contact recording medium can be maintained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a contactless IC card system to which the present invention is applied.

FIG. 2 is a block diagram of a transmission / reception circuit of a card reading / writing device of the contactless IC card system.

FIG. 3 is a block diagram of a transmission-side amplifier circuit to which the first amplification method of the transmission / reception circuit is applied.

4A and 4B are waveform diagrams of input / output signals of respective components of the transmission side amplifier circuit, FIG. 4A is a waveform diagram of a signal input to a voltage shifter, and FIG. FIG. 7C is a waveform chart of a signal output from the maximum value holding circuit.

FIG. 5 is a circuit diagram showing a specific example of a booster circuit of the transmission-side amplifier circuit to which the first amplification method is applied.

FIG. 6 is a circuit diagram showing a specific example of a booster circuit of the transmission-side amplifier circuit to which the first amplification method is applied.

FIG. 7 is a circuit diagram showing a specific example of a booster circuit of the transmission-side amplifier circuit to which the first amplification method is applied.

FIG. 8 is a circuit diagram illustrating a specific example of a booster circuit of the transmission-side amplifier circuit to which the first amplification method is applied.

FIG. 9 is a block diagram of a transmission-side amplification circuit to which the second amplification method of the transmission / reception circuit is applied.

10A and 10B are waveform diagrams of input / output signals of respective components of the transmission-side amplifier circuit, FIG. 10A is a waveform diagram of a signal input to a power amplifier, and FIG. FIG. 3C is a waveform diagram illustrating an operation state of the power amplifier, and FIG. 3D is a waveform diagram of a signal output from the power amplifier.

FIG. 11 is a circuit diagram showing a specific example of the transmission-side amplifier circuit to which the second amplification method is applied.

FIG. 12 is a circuit diagram showing a specific example of the transmission-side amplifier circuit to which the second amplification method is applied.

FIG. 13 is a circuit diagram of a transmission-side amplification circuit to which the third amplification method of the transmission / reception circuit is applied.

14A and 14B are waveform diagrams of respective signals in the transmission-side amplifier circuit, and FIG. 14A is a waveform diagram of a switch control signal;
(B) is a waveform diagram of a current flowing through the loop antenna, and (c) is a waveform diagram of a voltage generated in the loop antenna.

FIG. 15 is a waveform diagram of each signal in the transmission-side amplifier circuit when the on-time and the off-time of the switch control signal are the same, FIG. 15 (a) is a waveform diagram of the switch control signal, and FIG. () Is a waveform diagram of a current flowing through the loop antenna, and (c) is a waveform diagram of a voltage generated in the loop antenna.

FIG. 16 is a circuit diagram showing a specific example of the transmission-side amplifier circuit to which the second amplification method is applied.

17A and 17B are waveform diagrams of signals in the transmission-side amplifier circuit shown in FIG. 16; FIG. 17A is a waveform diagram of a switch control signal; FIG. 17B is a waveform diagram of a current flowing through a loop antenna; (C) is a waveform diagram of a voltage generated in the loop antenna.

[Explanation of symbols]

1 Non-contact IC card system, 2 IC card, 3
Card reader / writer, 21 loop antenna, 22
Control circuit, 23 transceiver circuit, 24 DC power supply

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[Procedure amendment]

[Submission date] November 19, 1998 (1998.11.
19)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 6

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

According to the present invention, for example, a switching section for switching a power supply voltage supplied from the power supply in accordance with a modulation signal, an antenna for emitting an electromagnetic wave in accordance with the switching of the switching section, and a current value flowing through the antenna are provided. Control means for controlling the control unit, the current value of the current flowing to the antenna when the switching unit is off is linearly reduced, and the current value of the current flowing to the antenna when switching from off to on is changed to the previous value . From off to on
The data is transmitted by an electromagnetic wave obtained by setting the same value as the current value flowing to the antenna at the time of switching .

[Procedure amendment 3]

[Document name to be amended] Drawing

[Correction target item name] Fig. 6

[Correction method] Change

[Correction contents]

FIG. 6

Claims (7)

[Claims] 1. A data writing device for writing data by supplying an electromagnetic wave to a non-contact recording medium, comprising: a data processing means for processing data to be written on the recording medium; A modulating signal is generated by modulating the data processed by the processing means, a transmitting means for amplifying the modulated signal and transmitting data to the recording medium using electromagnetic waves, and a data processing means and the transmitting means A power supply for supplying a DC voltage to the data, wherein the transmitting means amplifies the amplitude of the modulation signal to a voltage amplitude higher than a voltage value supplied from the power supply, and transmits the data. Writing device. 2. The transmission device according to claim 1, wherein the transmission unit includes a booster that boosts a voltage supplied from the power supply, and an amplifier that amplifies data by the voltage boosted by the booster. 2. The data writing device according to claim 1. A boosting section for dividing or multiplying the operation clock or the modulation signal; a level shift section for DC-shifting the divided or multiplied operation clock or the modulation signal; 3. The data writing device according to claim 2, further comprising a peak holding unit that holds a shifted operation clock or a peak value of the modulation signal. 4. The transmitting means shifts the level of the modulated signal in a DC manner, and modulates the level-shifted modulated signal and the non-level-shifted modulated signal when the level-shifted signal is high and low. 2. The data writing device according to claim 1, wherein a signal having a voltage amplitude higher than a voltage value supplied from the power supply is generated by switching between the signal and the signal. 5. The transmitting means shifts the level of a generated signal having a voltage amplitude higher than a voltage value supplied from the power supply in a DC manner, and determines whether the level-shifted signal is at a high level or at a low level. 5. The data writing apparatus according to claim 4, wherein a process of generating a signal by switching between a signal that is level-shifted and a signal that is not level-shifted is performed a plurality of times. 6. A switching unit that switches a power supply voltage supplied from the power supply according to a modulation signal, an antenna that emits an electromagnetic wave according to the switching of the switching unit, and a current that flows through the antenna. A control unit that controls a value of the current flowing through the antenna when the switching unit is turned off. 2. The data writing device according to claim 1, wherein the value is set to 0. 7. A data reading / writing device for reading and writing data by supplying an electromagnetic wave to a non-contact recording medium, wherein the data read from the recording medium and the recording medium are written. Data processing means for processing the data to be processed, and modulating the data processed by the data processing means to generate a modulation signal, amplifying the modulation signal and transmitting the data to the recording medium using electromagnetic waves. Transmitting and receiving means for receiving data transmitted by electromagnetic waves from the recording medium and supplying the data processing means to the data processing means; and a power supply for supplying a DC voltage to the data processing means and the transmitting and receiving means. Transmitting the data by amplifying the amplitude of the modulation signal to a voltage amplitude higher than the voltage value supplied from the power supply. Data read / write device.