JP2002111751A - Digital data modulation device, transmission device, transmission / reception device and methods thereof - Google Patents

Abstract

[PROBLEMS] To realize an ASK modulated wave that can be easily demodulated and can supply power stably. A digital data modulation device (30) for modulating digital data includes a modulation circuit (31) for mirror code modulating the digital data, and a differentiation circuit (32) for differentiating the digital data modulated by the modulation circuit (31). )
And an inverting circuit (33) for inverting the digital data differentiated by the differentiating circuit (32).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital data modulation apparatus and method, a digital data modulation apparatus and method including the digital data modulation apparatus and method, and a transmission apparatus and method for transmitting modulated digital data. And a transmitting / receiving apparatus and method to which a receiving apparatus and method for receiving and demodulating modulated digital data are added.

[0002]

2. Description of the Related Art Introduction of IC cards has been promoted in financial systems, transportation systems, distribution systems and the like.
The IC card has a built-in memory and can record more data than a conventional magnetic card. Furthermore, by attaching a CPU to the IC card, arithmetic functions and
A judgment function can be added. With the above features, the IC card can be used as a highly secure recording medium or a recording medium having an excellent authentication function.

The data of the IC card is stored in a read writer (R
W) Read or written by the device. When this process is performed by attaching a metal terminal to the surface of the IC card and mechanically bringing the terminal into contact with the contact pin of the RW device, the IC card is contact-type IC
It is called a card. This contact type IC card has a problem in that when it is used frequently, the terminals and pins are mechanically worn or damaged.

[0004] On the other hand, an IC card that uses electromagnetic waves without making contact with the RW device is called a non-contact type IC card.
Since the non-contact type IC card has no mechanical contact with the RW device, there is no problem such as mechanical damage.

[0005] These IC cards require power to operate a built-in memory and CPU. Contact type I
The C card obtains power through the terminal, but the non-contact type IC
Since the card cannot get power through the terminal, it has a built-in battery as a power source (battery type)
Utilizes electromagnetic waves transmitted from the RW device (battery-free type). In the case of a battery-operated IC card, its use period is limited by the life of a built-in battery. Therefore, battery-operated IC
Cards have the disadvantage that they are not suitable for long-term use.
On the other hand, a battery-less IC card can obtain electric power any time it receives electromagnetic waves. From the above, it is considered that the non-contact type battery-less IC card will spread in the future.

As described above, the non-contact type battery-less IC card obtains data and power from electromagnetic waves transmitted from the RW device. The electromagnetic wave transmitted from the RW device is a modulated wave obtained by modulating digital data. As a digital data modulation method used by the RW device, ASK (Amplit
ude Shift Keying) method, FSK (Fr
There can be conceived an Eq. (Shift Shift Keying) method and a PSK (Phase Shift Keying) method.

[0007]

SUMMARY OF THE INVENTION The FSK modulation method and the PS
A modulated wave by the K modulation method can supply stable power because the amplitude does not change with time. However, the frequency band of the modulated wave is wide, and is greatly affected by other electronic devices.
Further, there is a problem that the demodulation circuit of the FSK modulation wave or the PSK modulation wave is larger in scale than the demodulation circuit of the ASK modulation wave, and the power consumption in the IC card is large.

On the other hand, the modulated wave by the ASK modulation method does not have such a problem. However, when the degree of modulation is high, a period in which the amplitude of the modulated wave is small exists, and power supply is performed stably. I can't. Therefore, Japanese Patent Laid-Open Publication No. Hei 10-13312 proposes performing communication at a low modulation factor in order to stabilize power supply. However, if the degree of modulation is low, the difference in signal level becomes small, so that demodulation becomes difficult.

The present invention utilizes an ASK modulated wave having a high degree of modulation, and shortens the time during which the amplitude of the modulated wave is small as much as possible. The aim is to realize the waves.

[0010]

According to a first aspect of the present invention, there is provided a digital data modulating apparatus comprising: a modulating means for mirror code modulating digital data; a differentiating means for differentiating the digital data modulated by the modulating means; And inverting means for inverting the differentiated digital data.

According to a second aspect of the present invention, there is provided a digital data transmitting apparatus, comprising: a modulating means for mirror code modulating digital data; a differentiating means for differentiating the digital data modulated by the modulating means; A first digital data modulator comprising an inverting means for inverting, a second digital data modulator for further ASK modulating the digital data modulated by the first digital data modulator, and a second digital data modulator And a transmitting means for transmitting the electromagnetic wave modulated by.

According to a third aspect of the present invention, in the transmitting / receiving apparatus, the transmitting apparatus further includes receiving means for receiving the electromagnetic wave subjected to ASK modulation, and demodulating means for demodulating digital data from the electromagnetic wave received by the receiving means. It is characterized by.

According to a fourth aspect of the present invention, there is provided a digital data modulation method, comprising: a modulation step of mirror code modulating digital data; a differentiation step of differentiating the digital data modulated by the modulation step; and a digital data differentiated by the differentiation step. And an inversion step of inversion.

According to a fifth aspect of the present invention, there is provided a digital data modulation method for modulating digital data, comprising: a modulation step of mirror-modulating the digital data; and a differential step of differentiating the digital data modulated by the modulation step. A first step of inverting the digital data differentiated by the differentiating step.
Digital data modulation method, and digital data modulated by the first digital data modulation method
The method is characterized by comprising a second digital data modulation method for modulating and a transmitting step of transmitting an electromagnetic wave modulated by the second digital data modulation method.

According to a sixth aspect of the present invention, there is provided a transmitting / receiving method.
Is further characterized by including a receiving method for receiving an ASK-modulated electromagnetic wave and a demodulating method for demodulating digital data from the electromagnetic wave received by the receiving method.

[0016]

FIG. 1 shows an example of a non-contact type IC card system including a reader / writer (RW) device 10 and an IC card 20.

The RW device 10 includes an antenna 11, a carrier wave transmitter 12, a modulator 14, a demodulator 15, a communication controller 16,
And a power supply 17. The power supply 17 is a carrier wave transmitting unit 1
2 and the communication control unit 16. Communication control unit 16
Processes the data transmitted from the demodulation unit 15 and the data transmitted to the modulation unit 14, and processes the carrier wave transmission unit 12, the modulation unit 14,
Further, it controls the demodulation unit 15.

The IC card 20 comprises an antenna 21, a rectifier 23, a modulator 24, a demodulator 25, a data processor 26, a memory 27, a voltage detector 28, and a power supply 29.

When transmitting from the RW device 10 to the IC card 20, first, a carrier is generated by the carrier transmitter 12. Next, the generated carrier is ASK-modulated by the transmission data in the modulator 14. Finally, A
The SK modulated wave is transmitted by the antenna 11 as an electromagnetic wave.

The steps of transmission from the RW device 10 to the IC card 20 can be understood from FIG. First, RW
From the two signal levels of the digital data, the signal of the higher signal level (H level) is transmitted from the device 10 to the IC card 20 without modulation. The RW device 10
The presence of the IC card 20 (by changing the state of the electromagnetic wave,
Or by some other function, such as a sensor)
A clock for timing is transmitted to the IC card 20. The IC card 20 generates a synchronous clock using the clock. After that, the RW device 10 transmits the electromagnetic wave ASK-modulated with the transmission data to the IC card 20.

Here, the transmission data means the communication control unit 16
Are modulated data modulated by the digital data modulation device 30 included in. Hereinafter, the modulation method will be described in detail.

FIG. 3 is a block diagram showing the configuration of the digital data modulation device 30. This digital data modulation device 30 includes a mirror code modulation circuit 31, a differentiation circuit 32,
And an inverting circuit 33. The unmodulated digital data 101 is sequentially converted into signals 102, 10
3, 104.

It is assumed that, for example, unmodulated digital data shown in FIG. The unmodulated digital data 101 is first input to the mirror code modulation circuit 31 shown in FIG.

Here, in the mirror code modulation, data "1" to be modulated is represented as a change in the middle of the corresponding modulated data bit, and data "0" to be modulated is represented by the corresponding modulated data bit. This is expressed as a change at a break between the current data bit and the immediately preceding data bit, or maintaining the immediately preceding output state in the corresponding modulated data bit. That is, the data to be modulated is “1”.
In the case of, the output state (H level or L level) immediately before the bit in the middle of the bit corresponding to the “1” in the modulated data changes (change from H level to L level, or (From L level to H level). On the other hand, when the data to be modulated is “0”, conversion is performed by the following two different methods according to the data immediately before the data. First, data “0” to be modulated
When the data immediately before is “1”, the output state (H level or L level) immediately before the bit is maintained in a 1-bit section corresponding to the “0” in the modulated data. Further, when the data immediately before the data “0” to be modulated is “0”, the signal (H) is generated at a break between the bit corresponding to the “0” in the modulated data and the immediately preceding bit.
Level or L level) (change from H level to L level or change from L level to H level). From the above, the mirror code modulation is uniquely determined by the 2-bit data and the output state immediately before.

Further, no more than two bits of the signal that do not change continue in the middle of the mirror-code modulated digital data. By this conversion, the DC component and the low frequency component of the unmodulated digital data are reduced.

FIG. 4B shows an example of the data 102 obtained.
Shown in

Next, the data 102 is input to the differentiating circuit 32 shown in FIG. The differentiating circuit 32 converts all the changing portions of the input digital data (from L level to H level or from H level to L level) into positive pulse signals. The output signal 103 is shown in FIG.

Further, the signal 103 is input to the inverting circuit 33. The finally obtained inverted signal 104 is shown in FIG.
This is indicated by (4).

In the signal of FIG. 4 (4), the time during which the lower signal level (L level) of the two signal levels is maintained is compared with that of the unmodulated data shown in FIG. 4 (1). It is clear that it is shorter.

Further, referring to FIG.
A part of the waveform of the SK-modulated carrier is shown. FIG.
FIG. 4A shows an inverted signal used for ASK modulation.
Same as (4). FIG. 5 (2) is an enlarged view of one section of FIG. 5 (1), and FIG. 5 (3) shows the waveform of the carrier wave ASK-modulated at the portion shown in FIG. 5 (2). .

In the waveform shown in FIG.
The time during which the amplitude is small (the time during which the signal indicates the L level in FIG. 5B) is defined as Tw.

The difference between the amplitude at time Tw and the amplitude at other times differs depending on the modulation factor. The modulation degree is the ratio of the data amplitude to the carrier amplitude (data amplitude / carrier amplitude). Therefore, when the modulation factor is 1, the amplitude difference between the time Tw and the other times is maximized, and the amplitude of the modulated wave at the time Tw becomes zero.

The RW device 10 of the present invention transmits an ASK modulated wave having a high modulation degree obtained by the above method. In the ASK modulated wave, the higher the degree of modulation, the greater the difference between the two signal levels.
Demodulation of the ASK modulated wave is easier. In addition, since the ASK modulated wave having a high modulation degree becomes strong against noise, the IC card 20 can receive more accurate data.

Further, the received ASK modulated wave is half-wave rectified or full-wave rectified and can be used to generate electric power. In the case of an ASK modulated wave having a high modulation factor, there is generally a period in which the amplitude of the modulated wave is small and sufficient power cannot be supplied. However, in the ASK modulation wave according to the present invention, the time Tw in which the amplitude of the modulation wave is small is sufficiently reduced, so that more stable power supply can be realized. The time Tw is variable depending on the characteristics of the differentiating circuit 32 in FIG. 2, and the detection of the ASK modulated wave can be shortened as much as possible.

In addition, when the digital data modulation device 30 of the present invention converts continuous "0" data,
A continuous signal generated at a bit break can be easily obtained. This can be conveniently used as a clock for the IC card 20 to synchronize.

The ASK-modulated electromagnetic wave transmitted from the RW device 10 is transmitted by the antenna 21 of the IC card 20
It is converted into a voltage fluctuation between both ends of the antenna 21 as an electric signal. The voltage across it is provided as input to rectifier 23. The voltage signal rectified by the rectifier 23 is
A demodulation unit 25 for demodulating data, a voltage detection unit 28,
Then, the power is supplied to a power supply unit 29 for power generation.

In the demodulation unit 25, the data transmitted from the RW device 10 is demodulated according to a predetermined method, and the demodulated data is sent to the data processing unit 26. The data processing unit 26 processes the data sent from the demodulation unit 25 according to the content of the received data. Data processing unit 26
Also controls the memory 27 to read and write data to the memory 27.

The power generated by the power supply unit 29 is transmitted to the demodulation unit 2
5. The data is supplied to the data processing unit 26 and the memory 27.

On the other hand, transmission of data from the IC card 20 is performed by the field effect transistor 40 (FET: Field Ef) of the modulation unit 24 controlled by the data processing unit 26.
Fact Transistor).
Here, the field effect transistor 40 (hereinafter, “FET”)
That. The diode 42 is connected to the source terminal of ().

The diode 42 is connected to fix the source potential and to improve the switching characteristics of the transistor by using the bias with the substrate.

Further, the gate terminal of the FET 40 is connected to the data processing unit 26, and by transmitting a control signal from the data processing unit 26, the FET 40 can be switched.

As shown in the transmission / reception step of FIG.
When transmitting data from the IC card 20, the IC card 2
0 indicates that an unmodulated H level signal is always received from the RW device 10, and a constant voltage is applied between the terminals of the antenna 21. When the data to be transmitted is at the L level, the IC card 20
Turns on the FET 40. When the FET 40 is turned on, a current flows between the source and the drain, the load applied to the antenna 21 changes, and the voltage between the terminals of the antenna 21 changes. That is, ASK modulation is substantially performed. The RW device 10 can receive data from the IC card 20 by detecting a change in the state of the electromagnetic wave due to the voltage fluctuation. The RW device 10 determines that the transmission from the IC card 20 has been completed based on the content of the received data.

Further, while the IC card 20 is receiving an unmodulated electromagnetic wave from the RW device 10, stable power is supplied to the IC card 20. On the other hand, when the IC card 20 transmits data, power is not supplied, but R
It is possible to make the transmission time as short as possible for the W device 10 to detect data.

As described above, the IC using the FET 40
When the transmission from the card 20 is performed, the circuit configuration of the IC card 20 can be simplified, and the power consumption of the IC card 20 can be reduced.

The configuration of the modulator 24 of the IC card 20 can be applied to the RW device 10 as shown in FIG.

The types of electromagnetic waves and antennas to be modulated according to the present invention are not limited by the above embodiment. Therefore,
The application of the transmission and transmission / reception system of the present invention is not limited to the IC card system.

[0047]

As described above, by using the digital data modulation device and the digital data modulation method according to the present invention, a modulated wave that can be easily demodulated and that can supply a stable power can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a non-contact type IC card system.

FIG. 2 is a diagram showing a transmission / reception step between a reader / writer (RW) and an IC card.

FIG. 3 is a block diagram illustrating a configuration of a digital data modulation device.

FIG. 4 is a view showing an example of digital data modulated by the digital data modulation device shown in FIG. 3;

FIG. 5 is a diagram showing the inverted signal shown in FIG. 4 and the waveform of a carrier wave ASK-modulated by the inverted signal.

FIG. 6 is a diagram showing a configuration of an RW device employing a modulation unit similar to an IC card.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Lead-writer (RW) apparatus 11 Antenna 12 Carrier wave transmission part 14 Modulation part 15 Demodulation part 16 Communication control part 17 Power supply 20 IC card 21 Antenna 23 Rectification part 24 Modulation part 25 Demodulation part 26 Data processing part 27 Memory 28 Voltage detection part 29 Power supply unit 30 Digital data modulation device 31 Mirror code modulation circuit 32 Differentiation circuit 33 Inversion circuit 40 Field effect transistor (FET) 42 Diode

Claims (6)

[Claims] 1. A digital data modulator for modulating digital data, comprising: a modulator for modulating the digital data with a mirror code; a differentiator for differentiating the digital data modulated by the modulator; A digital data modulator comprising: an inverting means for inverting the differentiated digital data. 2. A digital data modulator for modulating digital data, comprising: a modulator for mirror-code modulating the digital data; a differentiator for differentiating the digital data modulated by the modulator; A first digital data modulator comprising an inverting means for inverting the differentiated digital data; a second digital data modulator for further ASK modulating the digital data modulated by the first digital data modulator; A transmitting unit for transmitting an electromagnetic wave modulated by the second digital data modulating device. 3. The transmitting / receiving apparatus according to claim 1, wherein said transmitting apparatus further includes a receiving unit for receiving an ASK-modulated electromagnetic wave, and a demodulating unit for demodulating digital data from the electromagnetic wave received by said receiving unit. 4. A digital data modulation method for modulating digital data, comprising: a modulation step of mirror code modulating the digital data; a differentiation step of differentiating the digital data modulated by the modulation step; Inverting the differentiated digital data. 5. A digital data modulation method for modulating digital data, comprising: a modulation step of mirror-code modulating the digital data; a differentiation step of differentiating the digital data modulated by the modulation step; A first digital data modulation method comprising an inversion step of inverting the differentiated digital data; a second digital data modulation method for further ASK modulating the digital data modulated by the first digital data modulation method; A transmitting step of transmitting an electromagnetic wave modulated by the second digital data modulation method. 6. A transmitting / receiving method, wherein the transmitting method further includes a receiving step of receiving an electromagnetic wave subjected to ASK modulation, and a demodulating step of demodulating digital data from the electromagnetic wave received by the receiving method.