JP3449621B2 - Reader / writer device for non-contact IC card system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reader / writer device for a contactless IC card system, and more particularly to a reader / writer device for a contactless IC card system with improved power transmission efficiency to the contactless IC card. .

[0002]

2. Description of the Related Art In a non-contact IC card system, a loop antenna is provided in both the non-contact IC card and the reader / writer device. For example, when transmitting power or power and information from the loop antenna device to the non-contact IC card, An AC signal of about several tens of KHz to several tens of MHz is passed through the loop antenna of the reader / writer device to excite electromagnetic waves, and this is detected by the loop antenna of the non-contact IC card placed in close proximity. That is, the loop antenna of the contactless IC card and the reader / writer device functions as an antenna for transmitting electric power and energy of information.

FIG. 3 is a block diagram showing a portion of the above-mentioned non-contact IC card system relating to the coupling of the reader / writer device and the non-contact IC card. The oscillator 31 provided in the reader / writer device 30 is shown in FIG. The oscillation frequency fc is several tens KHz to ten and several MHz as described above. In the case of information transmission, the carrier wave from the oscillator 31 is input to the modulator 32, and this is modulated by the data DATAa. Then, this is amplified by the power amplifier 33 and transmitted from the loop antenna 35 via the matching circuit 34 with the loop antenna 35. In the case of only power transmission, the carrier wave from the oscillator 31 is transmitted without being modulated. In the transmission from the reader / writer device 31 to the non-contact IC card 40, the magnetic flux generated by the loop antenna 35 is generated by the non-contact IC card 40.
This is performed by interlinking with the loop antenna 41 and exciting the induced voltage. In the non-contact IC card 40, the induced voltage of the loop antenna 41 is rectified by the diode bridge 43 and used as a power source for each circuit in the non-contact IC card,
Further, the same induced voltage is guided to a demodulation circuit (not shown) to demodulate data from the reader / writer device. The capacitor 42 is provided in order to improve the transmission efficiency of the carrier wave or the modulated wave from the reader / writer device by the resonance of the parallel resonance circuit including the loop antenna 41 and the capacitor 42.

Next, a reader / card is read from the non-contact IC card 40.
At the time of data transmission to the writer device 30, the reader / writer device transmits an unmodulated carrier wave and only supplies power to the non-contact IC card. In the non-contact IC card, the data DATAb to be transmitted is input to the modulation circuit 44 and the impedance of the modulation circuit 44 is changed. As a result, the load impedance of the loop antenna 41 changes, and this changes the load of the transmission carrier on the reader / writer device side, and the voltage / current at the point A of the reader / writer device 30 becomes the transmission data DATAb of the contactless IC card.
Change according to. This is called load switch modulation, and the modulation circuit 44 is called a load switch type modulation circuit. In the reader / writer device 30, the above-mentioned voltage / current change is demodulated by the demodulation circuit 36, and the non-contact IC
The data DATAb from the card 40 is taken out.

[0005]

FIG. 4 is a diagram showing the input portion of the demodulation circuit 36 shown in FIG. 3 in more detail. As described above, when data is sent from the non-contact IC card 40, the loop antenna 4 of the non-contact IC card 4
1 load 45 (modulation circuit 44, rectification circuit 43, etc. in FIG. 3 are regarded as one load) is data DATA.
b, which changes the output current I of the power amplifier 33. Therefore, in order to detect this change, a resistor 37 is inserted on the ground side of the loop antenna 35, and the voltage drop VS caused by the current I flowing therethrough is input to the demodulation circuit 36. The demodulation circuit 36 detects a change in the input voltage VS and detects DA from the non-contact IC card 40.
Demodulate TAb. However, when the current I from the power amplifier 33 is passed through the resistor 37, power is consumed here.
For this reason, the power amplifier 33 requires extra output power as much as the power consumed by the resistor 37, and there is a problem that the power transmission efficiency decreases.

In Japanese Patent Application No. 9-83757, a capacitor is added in parallel or in series with the loop antenna on the reader / writer device side so as to resonate at or near the carrier frequency to a non-contact IC card. A device having improved power transmission efficiency is provided. FIG. 5 shows in detail the periphery of the demodulation circuit when parallel resonance is used, and the capacitor 39 resonates in parallel with the loop antenna 35. In this case, since the impedance of the parallel resonance circuit has a large value near the resonance point, the matching circuit 34
The output side impedance of is also a large value accordingly, and the voltage V at this high impedance point is taken into the demodulation circuit 36 via the resistor 38 and demodulated. In this configuration, the carrier current causes the series impedance of the resistor 38 and the input impedance in the carrier band of the demodulation circuit 36 to enter the parallel circuit including the loop antenna 35 and the capacitor 39 in parallel, and the contactless IC card Therefore, the Q of the resonance circuit is lowered to detect the data. This immediately reduces the power transfer efficiency to the contactless IC card.

FIG. 6 shows the periphery of the demodulation circuit 36 when the power transmission efficiency is improved by series resonance. In this case, the loop antenna 35 and the capacitor 39 are shown.
To form a series resonance circuit. Since the impedance of the circuit has a small value at the time of series resonance, in this case, the current I from the power amplifier 33 is passed to the resistor 38 ', and the voltage drop VS thereof is detected by the demodulation circuit 36. This is similar to the case of non-resonance in FIG. Therefore, power consumption occurs in the resistor 38 ', and in this case, the resistor 38' enters in series with the series resonance circuit, and Q
Will decrease and the power transmission efficiency will decrease.

In any of the circuits, the demodulation circuit 36 and the power amplifier 33 have a common ground point for detecting a change in voltage / current on the output side of the power amplifier 33. For this purpose, the demodulation circuit 36 and the power amplifier 33
Since at least the ground point is common to the power supplies of the above, there is also a problem that the noise current of the power amplifier 33 influences the demodulation circuit 36 via the power supply circuit, so that so-called wraparound easily occurs. The above-mentioned problems are the same even when the matching circuit 34 is not used in FIGS. Further, the data transmission method from the non-contact IC card is the same even in cases other than the load switch method.

An object of the present invention is not to reduce the power transmission efficiency from the reader / writer device, and to reduce the data transmitted from the non-contact IC card without lowering the power transmission efficiency from the reader / writer device. Another object of the present invention is to provide a reader / writer device capable of demodulating and separating the power source of the demodulating circuit from the power source of a power amplifier.

[0010]

According to the present invention, an output carrier signal is modulated and amplified by a power amplifier, and then supplied to an antenna circuit, and power and data are transmitted to a contactless IC card electromagnetically coupled to the antenna circuit. In addition to non-contact IC
The data transmitted from the card is received by the antenna circuit, and the contact IC is demodulated from the received signal by the demodulation circuit.
A reader / writer device of a contactless IC card system configured to demodulate data from a card, characterized in that the antenna circuit, the power amplifier, and the demodulation circuit are mutually coupled by a matching transformer. A reader / writer device for a non-contact IC card system is disclosed. Further, according to the present invention, electromagnetically coupled to the first antenna circuit in the non-contact IC card, the carrier wave is supplied to the antenna circuit to send power and data to the IC card, and the signal is sent from the antenna circuit. In a reader / writer device of a non-contact IC card system that takes in data from an IC card, a power amplification circuit that amplifies a carrier signal including power and data, a demodulation circuit that demodulates data from the IC card, and the power amplification. A first primary winding that is connected to the output end of the circuit and outputs an output carrier signal. A second primary winding that is connected to the input end of the demodulation circuit and outputs captured data to the demodulation circuit. A transformer including a secondary winding, and a first primary winding and a secondary winding connected to the secondary winding and electromagnetically coupled to the first antenna circuit in the IC card. Sent through The carrier wave signal coming from the first antenna circuit is sent to the first antenna circuit as a carrier wave, and the data sent from the first antenna circuit is received and sent to the demodulation circuit via the secondary winding and the second primary winding. A reader / writer device of a non-contact IC card system including two antenna circuits is disclosed.

Further, according to the present invention, a capacitor is connected in parallel to a winding connected to the demodulation circuit of the transformer, and a resonance frequency of a parallel circuit including the winding and the capacitor is transmitted from the non-contact IC card. There is provided a reader / writer device for a non-contact IC card system, wherein the capacitance of the capacitor is set so as to be in a data frequency band.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 shows an example of a circuit configuration around a demodulation circuit input section of a reader / writer device according to the present invention.
By the matching transformer 1 having 1, 12, 13
The power amplifier 33, the antenna circuit 2, and the demodulation circuit 36 are coupled. As the antenna circuit 2, the parallel resonance type shown in FIG. 5 is used. Here, the turn ratio between the winding 11 and the winding 12 is set to a value that matches the resonance frequency of the antenna circuit 2 between the output of the power amplifier 33 and the antenna circuit 2. This has the same function as the matching circuit 34 shown in the conventional example.

A feature of the present invention is that the matching transformer 1 is also used for coupling with the demodulation circuit.
The winding ratio of the winding 13 and the winding 12 is the data D from the non-contact IC card sent by the load switch method.
It is set so that matching can be achieved in the frequency band of ATAb.
According to this configuration, since a resistor is not used for coupling the demodulation circuit 36 as in the conventional case, power consumption by the coupling resistance and deterioration of Q in the antenna circuit 2 which is a parallel resonance circuit hardly occur. Further, since the ground points G1 and G2 of the winding 11 and the winding 13 can be separated, the power amplifier 3
3 and the power source of the demodulation circuit 36 can be separated, and the operation of the demodulation circuit 36 can be easily prevented from being affected by noise or the like of the power amplifier that handles large power.

FIG. 2 shows a modification of the embodiment shown in FIG. 1, in which a capacitor 3 is connected in parallel to the winding 13 of the matching transformer 1. In the antenna circuit 2 of the reader / writer device, resonance of the carrier frequency is used to improve the power transmission efficiency to the non-contact IC card.
At the data frequency from the non-contact IC card, such resonance does not improve the transmission efficiency. Therefore, the capacitor 3 is connected in parallel to the winding 13, and the winding 13 and the capacitor 3 are connected.
The parallel resonance of is used to increase the data detection sensitivity. As a result, information from the non-contact IC card can be detected more reliably, or data can be transmitted from a non-contact IC card that is farther away.

In FIGS. 1 and 2, the windings 11, 12, 1 are shown.
3 was put in one transformer, but winding 11,
It is also possible to use 12 as the same matching circuit as the conventional one, and connect the antenna circuit and the demodulation circuit with another transformer. Although the parallel resonant circuit is used as the antenna circuit 1 in FIGS. 1 and 2, the present invention is not limited to this. That is, it is clear that the power transmission efficiency to the non-contact IC card can be improved even with the non-resonance type or series resonance type antenna circuit as described in FIG. 4 or FIG. Non-contact I depending on the configuration
The effect of improving the data transmission efficiency from the C card can be obtained. Further, it is clear that the above description is not limited to the load switch system.

[0016]

According to the present invention, the demodulation circuit for the data sent from the non-contact IC card can be constructed without lowering the power transmission efficiency from the reader / writer device.
Furthermore, the reliability of the demodulation circuit can be further improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit configuration example around a demodulation circuit input section of a reader / writer device according to the present invention.

FIG. 2 is a modification of the circuit of FIG.

FIG. 3 is a block diagram showing a configuration example of a conventional non-contact IC card system.

FIG. 4 is a diagram showing details around a demodulation circuit input section in FIG. 3;

FIG. 5 is a diagram showing details of the periphery of a demodulation circuit input unit when the antenna circuit of the reader / writer device is of a parallel resonance type.

FIG. 6 is a diagram showing details of the periphery of a demodulation circuit input portion when the antenna circuit of the reader / writer device is of a series resonance type.

[Explanation of symbols]

1 Matching transformer 2 antenna circuit 3 capacitors 11, 12, 13 windings 33 power amplifier 36 Demodulation circuit

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-10-90405 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G06K 17/00 H03J 3/20 H04B 1 / 59 H04B 5/02

Claims (4)

(57) [Claims] 1. An output carrier signal is modulated and amplified by a power amplifier, and then supplied to an antenna circuit to transmit power and data to a non-contact IC card electromagnetically coupled to the antenna circuit, and from the non-contact IC card. A reader / writer device of a non-contact IC card system configured to receive transmitted data by the antenna circuit and demodulate data from the contact IC card by a demodulation circuit from the received signal. A reader / writer device for a non-contact IC card system, wherein an antenna circuit, the power amplifier, and the demodulation circuit are connected to each other by a matching transformer. 2. A non-contact IC card is electromagnetically coupled to a first antenna circuit to supply a carrier wave to this antenna circuit to send electric power and data to the IC card, which is then sent from this antenna circuit. In a reader / writer device of a non-contact IC card system that takes in data from an IC card, a power amplification circuit that amplifies a carrier signal including power and data, a demodulation circuit that demodulates data from the IC card, and the power amplification. A first primary winding connected to the output end of the circuit to output an output carrier wave signal; and a second output connected to the input end of the demodulation circuit to output captured data to the demodulation circuit.
A transformer including a primary side winding and a secondary side winding, and a first primary side winding connected to the secondary side winding and electromagnetically coupled to a first antenna circuit in the IC card. And a carrier wave signal sent via the secondary winding and the first winding as a carrier wave.
A second antenna circuit for transmitting the data sent from the first antenna circuit to the demodulation circuit via the secondary winding and the second primary winding. Reader / writer device for non-contact IC card system. 3. A capacitor is connected in parallel to a winding connected to the demodulation circuit of the transformer, and a resonance frequency of a parallel circuit including the winding and the capacitor is a frequency band of data transmitted from the non-contact IC card. 2. The capacitance of the capacitor is set as in 1.
Or a reader of the non-contact IC card system according to 2.
Writer device. 4. The antenna circuit according to claim 1, wherein the antenna circuit is either a loop antenna only, a parallel circuit of a loop antenna and a capacitor, or a series circuit of a loop antenna and a capacitor. A reader / writer device of the contactless IC card system described.