JP2003288548A - Contactless ic card reader/writer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reproduce a transmit data signal of an IC card 2 always correctly. <P>SOLUTION: The contactless IC card reader/writer obtains a receive data signal corresponding to the transmit data signal through the stages of: writing information to the IC card 2 through an antenna 3 without contacting and receiving a signal outputted as a radio wave from the IC card; rectifying the received signal by a rectifying circuit 6; detecting its envelope by a detection circuit 7; amplifying the detection signal by an amplifier 8a; and binarizing the amplified detection signal outputted from the amplifier. The amplifier 8a comprises an amplifier circuit 15 which includes a 1st transistor T<SB>r1</SB>applied with the detection signal at its base terminal and amplifies the detection signal and a 2nd transistor T<SB>r2</SB>for temperature compensation of the same type with the 1st transistor which is interposed between the base terminal of the 1st transistor T<SB>r1</SB>and the ground and has its collector terminal connected to the base terminal. <P>COPYRIGHT: (C)2004,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact IC card reader / writer which reads and writes various information (data) on a mounted IC card in a non-contact manner. Involved
In particular, the present invention relates to a non-contact IC card reader / writer for obtaining a transmission data signal of an IC card from a signal received by an antenna. 2. Description of the Related Art A non-contact IC card reader / writer for reading and writing various information (data) on a mounted IC card in a non-contact manner is configured as shown in FIG. 5, for example. . That is, the non-contact IC card reader / writer comprises a control unit 1 comprising a computer for controlling the operation of the whole non-contact IC card reader / writer.
The IC attached to this non-contact IC card reader / writer
A writing unit 4 for writing various information (data) and transmitting a read command to the C card 2 via the antenna 3;
The reading unit 5 reads various information (data) from the card 2 via the antenna 3. The antenna 3
Is an antenna shared for transmission and reception. That is, transmission and reception are performed in different time zones based on the control of the control unit 1. [0004] In such a non-contact IC card reader / writer, first, a case where the control unit 1 writes various information (data) to the IC card 2 will be described. Control unit 1
Writes digital data to be written to the IC card 2 in the writing unit 4
Send to The writing section 4 converts the input digital data into a serial write data signal, and further superimposes the write data signal on the carrier signal to form a write signal, and outputs the write signal via the antenna 3. When the IC card 2 receives a write signal via its own antenna, the IC card 2 demodulates the received write signal into an original write data signal and converts the data of the write data signal into an internal storage element. Write to. Next, a case where the control unit 1 of the non-contact IC card reader / writer reads various information (data) stored in the IC card 2 will be described. The control unit 1 sends an instruction to read the stored information (data) to the IC card 2 via the writing unit 4 and the antenna 3. Then, the IC card 2 reads the designated information (data) from the storage element in the IC card 2 to create a transmission data signal a including the plurality of pulse waveforms 11 shown in FIG. 6, and transmits the high-frequency carrier signal to the transmission data signal a. The signal is amplitude-modulated by the data signal a and emitted as a transmission signal b via its own antenna. [0007] The antenna 3 of the non-contact IC card reader / writer side receives the transmission signal b output as a radio wave and sends it to the rectifier circuit 6 of the reading unit 5 as a reception signal c. The rectification circuit 6 rectifies the input received signal c by half-wave and sends it to the next detection circuit 7 as a rectified signal d. The detection circuit 7
The input rectified signal d is subjected to envelope detection and sent to the next amplifier 8 as a detected signal e. The amplifier 8 amplifies the detection signal e input from the detection circuit 7 and outputs it as a new detection signal f. As described above, since the received signal c is amplitude-modulated by the transmission data signal a including the plurality of pulse waveforms 11, the rectified signal d of the received signal c is detected by envelope detection and further amplified. As shown in FIG. 6, the signal f includes a plurality of waveforms 12 corresponding to the respective pulse waveforms 10 of the transmission data signal a. The amplified detection signal f output from the amplifier 8 is applied to one input terminal of a comparison circuit 9. The threshold voltage Th is applied to the other input terminal of the comparison circuit 9. The comparison circuit 9 compares the signal level of the detection signal f applied to one input terminal with the signal level of the threshold voltage Th applied to the other input terminal, and compares the comparison result. 6 is output as a binarized reception data signal g. The threshold voltage Th is equal to the amplitude of the amplified detection signal f.
Is set at a level substantially at the intermediate position of each of the waveforms 12, the binarized reception data signal g includes, as shown, the position of each pulse waveform 11 of the transmission data signal a of the IC card 2. The pulse waveform 13 exists at the corresponding position. The received data signal g including the plurality of pulse waveforms 13 output from the comparison circuit 9 is input to a decoder 10. The decoder 10 converts the input received data signal g, which is a pulse pattern signal, into read data and sends it to the control unit 1. Therefore, the control unit 1 can read information (data) stored in the IC card 2. [0012] However, the non-contact IC card reader / writer shown in FIG. 5 has the following problems to be solved. The amplifier 8 incorporated in the receiving section 5 generally has a simple circuit configuration including one transistor and a plurality of resistors. That is, as illustrated, the detection signal e which is output from the detection circuit 7 is applied to the base terminal of an npn transistor Tr through an input resistor R _1. A bias voltage obtained by dividing a DC control voltage Vcc by a pair of resistors R2 and R3 is applied to a base terminal of the transistor Tr. Further, the collector terminal of the transistor Tr is connected to a voltage source of direct current control voltage Vcc via a collector resistor R _4, the emitter terminal of the transistor Tr is grounded through the emitter resistor R _5. Then, the amplified detection signal f is taken out from the collector terminal and sent to the next comparison circuit 9. The signal level of the detection signal f output from the amplifier 8 having such a simple circuit configuration largely fluctuates according to the temperature (ambient temperature) of the environment in which the non-contact IC card reader / writer is installed. I do. FIG. 7A shows the signal level of the amplified detection signal f when the ambient temperature is, for example, about 25 ° C., which is about room temperature. FIG.
The signal level of the amplified detection signal f when the temperature rises to 0 ° C. is shown. The signal level (amplitude value) of the transmission signal b wirelessly output from the IC card 2 is originally very low. Therefore, the signal level of the reception signal c obtained by receiving the transmission signal b by the antenna 3 and the signal level of the detection signal e obtained by subjecting the reception signal c to half-wave rectification and envelope detection are also low. Therefore, the signal level included in the detection signal e input to the amplifier 8 is also low. As described above, when the detection signal e, which is a weak signal, is greatly amplified by the amplifier 8, the signal level of the amplified detection signal f becomes
It fluctuates greatly with changes in ambient temperature. Each waveform 1 contained in the amplified detection signal f
2 is smaller than the signal level, so for example,
As shown in FIG. 7A, under the condition that the ambient temperature is 25 ° C.,
Even if the threshold voltage Th is set at a substantially central position of each waveform 12, as shown in FIG.
When the temperature rises to ° C., the signal level of the amplified detection signal f greatly decreases, and the threshold voltage Th greatly deviates from substantially the center position of each waveform 12. As described above, when the threshold voltage Th is equal to the waveform 1
If the detection signal f is greatly deviated from the center position of the detection signal 2 by the threshold voltage Th, the reception data signal binarized by the comparison circuit 9 is obtained. Since g does not include the pulse waveform 13 corresponding to each waveform 12 at all, the transmission data signal a of the IC card 2 cannot be accurately reproduced. As a result, the control unit 1 cannot accurately read the information (data) stored in the IC card 2. The present invention has been made in view of such circumstances, and even if the ambient temperature changes, I
It is an object of the present invention to provide a non-contact IC card reader / writer device capable of reproducing a received data signal accurately corresponding to a transmitted data signal of a C card and thereby reading information stored in the IC card with high accuracy. SUMMARY OF THE INVENTION The present invention provides a
Information was written to the C card via an antenna in a non-contact manner, and radio waves were output from the attached IC card.
A signal obtained by superimposing a transmission data signal on a carrier wave is received via an antenna, and the received signal is rectified by a rectifier circuit,
The rectified signal output from the rectifier circuit is subjected to envelope detection by a detector circuit, the detected signal output from the detector circuit is amplified by an amplifier, and the amplified detected signal output from the amplifier is binarized. The present invention is applied to a non-contact IC card reader / writer for obtaining a reception data signal corresponding to a transmission data signal. In order to solve the above problem, in the non-contact IC card reader / writer device of the present invention, the amplifier includes a first transistor having a base terminal to which a detection signal output from the detection circuit is applied. An amplifier circuit for amplifying the detection signal, a second transistor for temperature compensation of the same type as the first transistor, which is interposed between the base terminal of the first transistor and the ground and has a collector terminal connected to the base terminal; And a transistor. In the non-contact IC card reader / writer configured as described above, even if the ambient temperature changes, a transmission data signal accurately corresponding to the transmission data signal of the IC card can be obtained from the amplified detection signal. Explain why. Generally, in an amplifier circuit including a single transistor into which a signal to be amplified is input to a base terminal, when the ambient temperature changes, the amplification factor α changes. Level (DC component)
And the waveform (AC component) included in the detection signal fluctuates.
Further, when the ambient temperature changes, not only the amplification factor α changes, but also the bias point of the input signal with respect to the amplification characteristics of the transistor changes. Due to the change of the bias point, the signal level (DC component) of the entire output detection signal changes. That is, the signal level of the detection signal applied to the base terminal of the transistor changes. For example, when the ambient temperature increases, the signal level (DC component) of the output of the amplifier decreases. Therefore, in the present invention, a second transistor for temperature compensation of the same type as the first transistor is connected between the base terminal of the first transistor and the ground, and the collector terminal is connected to the base terminal. It is inserted. In the second transistor having the base terminal connected to the collector terminal, the characteristics of the second transistor are similar to the characteristics of a diode. Therefore, the collector-emitter resistance of the second transistor decreases as the temperature rises. As a result, the potential of the base terminal with respect to the ground decreases, the base current of the first transistor decreases, and the signal level of the amplifier output (DC component)
Counteract the decline in Therefore, even if the ambient temperature changes, the signal level of the detection signal output from the amplifier hardly changes. Therefore, the amplified detection signal is converted into a binary signal using a predetermined threshold value, for example. Thus, a transmission data signal that exactly corresponds to the transmission data signal of the IC card can be obtained. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a non-contact IC card reader / writer according to the embodiment. The same portions as those of the conventional non-contact IC card reader / writer device shown in FIG. 5 are denoted by the same reference numerals, and detailed description of overlapping portions will be omitted. In the non-contact IC card reader / writer device of this embodiment, a predetermined positive (+) bias voltage V _B is applied to the detection signal e output from the detection circuit 7 to output the detection signal. e signal level (DC component)
And the detection signal e ₁ having only the positive (+) side component
Is provided. Furthermore, in the positive (+) side component only within the amplification circuit 8a for amplifying a detection signal e ₁ having the output from the detection circuit 7, the signal having only positive (+) side component bias circuit 14 converted detection signal e ₁ is applied to the base terminal of the first transistor Tr1 of the npn type via an input resistor R _8. [0031] The base terminal of the first transistors Tr1, bias voltage is applied through a bias resistor R ₆ from a voltage source for outputting a DC control voltage Vcc. Further, the collector terminal of the first transistor Tr1 is connected to a voltage source for outputting a DC control voltage Vcc via a collector resistor R _4, the emitter terminal of the first transistor Tr1 is grounded via an emitter resistor R ₅ I have. And the first
Detection signal f ₁ which is amplified from the collector terminal of the transistor Tr1 is taken out of, are sent to the next comparison circuit 9. [0032] Therefore, the first transistors Tr1, resistors _{R 8, R 6, R 4} , R 5 constitute an amplifier circuit 15 for amplifying a detection signal e ₁ input. In the amplifier circuit 15, the collector terminal of the second transistor Tr2 for temperature compensation is connected to the base terminal of the first transistor Tr1. The second transistor Tr2 for temperature compensation is a first transistor T2.
This is an npn-type transistor having the same type and the same specifications as r1. The base terminal of the second transistor Tr2 is connected to the collector terminal. Moreover, it is grounded emitter terminal of the second transistor Tr2 through a resistor R _7. The other structure is almost the same as the conventional non-contact IC card reader / writer shown in FIG. Next, the operation of the non-contact IC card reader / writer of the embodiment configured as described above will be described. The operation of the control unit 1 of the non-contact IC card reader / writer device to write various information (data) to the IC card 2 is the same as that of the conventional non-contact IC card shown in FIG.
Since this is the same as the writing operation in the C card reader / writer device, the description is omitted. Next, a case where the control unit 1 of the non-contact IC card reader / writer reads various information (data) stored in the IC card 2 will be described. The control unit 1 controls the IC card 2 via the writing unit 4 and the antenna 3
A command to read the stored information (data) is transmitted. Then, the IC card 2 reads the designated information (data) from the storage element in the IC card 2 and creates a transmission data signal a including the plurality of pulse waveforms 11 shown in FIG. The signal is amplitude-modulated by the data signal a and emitted as a transmission signal b via its own antenna. The antenna 3 of the non-contact IC card reader / writer side receives the transmission signal b output as a radio wave and sends it as a reception signal c to the rectification circuit 6 composed of the diode 6a connected to the illustrated polarity of the reading unit 5. Send out. Rectifier circuit 6
Performs half-wave rectification on the input received signal c as shown in FIG. 2 and sends it to the next detection circuit 7 as a rectified signal d having only a negative (-) component. The detection circuit 7 performs envelope detection on the input rectified signal d and outputs the detected signal as a detection signal e having only a negative (-) side component. Detection signal e output from the detection circuit 7, in the bias circuit 17, a positive (+) direction bias voltage V _B is applied to and converted into the detection signal e ₁ having only positive (+) side component . As described above, since the reception signal c is amplitude-modulated with the transmission data signal a including the plurality of pulse waveforms 11, when the rectified signal d of the reception signal c is envelope-detected, this detection signal e Are a plurality of waveforms 12 corresponding to each pulse waveform 11 of the transmission data signal a, as shown in FIG.
Is included. Therefore, the detection signal e ₁ having only the positive (+) component to which the bias voltage V _B is applied also includes a plurality of waveforms 12 corresponding to the respective pulse waveforms 11. The detection signal e ₁ is input to the amplifier 8a. Amplifier 8a amplifies the detection signal e ₁ which is input and output as a new detection signal f _1. The amplified detection signal f ₁ output from the amplifier 8a is applied to one input terminal of the comparison circuit 9.
The threshold voltage Th is applied to the other input terminal of the comparison circuit 9. Comparator circuit 9, conducted a comparison between the signal level of the threshold voltage Th, which is applied to one of the signal level and the other input terminal of the detection signal f ₁ which is applied to the input terminal, the comparison result and outputs it as reception data signal g ₁ binarized shown in FIG. The threshold voltage Th is equal to the amplified detection signal f _1.
Is set at a level substantially at the intermediate position of each of the waveforms 12, the binarized reception data signal g ₁ includes the position of each pulse waveform 11 of the transmission data signal a of the IC card 2 as shown in FIG. There is a pulse waveform 13 at a position corresponding to. The received data signal g ₁ including the plurality of pulse waveforms 13 output from the comparison circuit 9 is input to the decoder 10. The decoder 10 converts the received data signal g _1, which is the input pulse pattern signal, into read data and sends it to the control unit 1. Therefore, control unit 1 can read information (data) stored in IC card 2. Next, in the non-contact IC card reader / writer configured as described above, the control unit 1 accurately reads information (data) stored in the IC card 2 even if the ambient temperature fluctuates. The reason why the information can be output will be described with reference to FIGS. In the amplifier 8a incorporated in the reading section 5, as described above, when the collector terminal is connected to the base terminal of the second transistor Tr2 as shown in FIG. Transistor Tr2
The characteristics between the collector terminal and the emitter terminal in FIG. FIG. 4 shows a voltage V between the collector terminal (base terminal) and the emitter terminal when the collector terminal of the second transistor Tr2 is connected to the base terminal.
FIG. 4 is a diagram showing a relationship between _BE and a current I (collector current) flowing between a collector and an emitter. As the ambient temperature increases, the current I flows more easily. That is, the resistance between the collector terminal and the emitter terminal of the second transistor Tr2 decreases. In FIG. 4, in addition to the characteristic of the second transistor Tr2, the characteristic of the current I flowing between both terminals with respect to the applied voltage V of the general diode 16 is shown by a solid line. As described above, the amplifier circuit 15 including the first transistor Tr1 and the second transistor Tr2 for temperature compensation are used.
When the ambient temperature rises in the amplifier 8a in which is incorporated, the amplification factor of the first transistor Tr1 rises. As a result, the input detection signal e ₁ of the signal level (DC component) is decreased. However, when the ambient temperature increases, the resistance between the collector terminal and the emitter terminal of the second transistor Tr2 decreases, and the potential of the base terminal of the first transistor Tr1 with respect to the ground decreases. 1 of the base current of the transistor Tr1 is reduced to cancel the decrease of the signal level of the detection signal f ₁ output from the amplifier 8a (DC component). Therefore, even if the ambient temperature changes, the bias point for the amplification characteristic of the first transistor Tr1 in the amplifier circuit 15 hardly changes.
Detection signal f ₁ of the signal level of the amplified output from the amplifier 8a (DC component) hardly changes. As a result, the signal level at the intermediate position of the waveform 12 included in the amplified detection signal f ₁ and the threshold voltage Th
The signal level of the received data signal g ₁ binarized by the comparison circuit 9 always accurately corresponds to the transmitted data signal a of the IC card 2. Yotsute, control unit 1 read data decoded by the decoder 10 of the received data signal g ₁ is input IC card 2
Can be accurately read out. The present invention is not limited to the above embodiment. In the device of the embodiment, npn-type transistors are used as the first and second transistors Tr1 and Tr2, but pnp-type transistors can also be used. In this case, the second transistor Tr2
, It is necessary to connect the emitter terminal to the base terminal. As described above, the non-contact I of the present invention
In a C card reader / writer device, a second transistor for temperature compensation is incorporated in an amplifier when a signal received by an antenna is rectified, detected, and amplified. Therefore, even if the ambient temperature fluctuates, it is possible to reproduce a received data signal that exactly corresponds to the transmitted data signal of the IC card, and to read the information stored in the IC card with high accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a schematic configuration of a non-contact IC card reader / writer according to an embodiment of the present invention. FIG. 2 is an overall view of the non-contact IC card reader / writer of the embodiment. FIG. 3 is a detailed circuit diagram of a main part of an amplifier incorporated in the non-contact IC card reader / writer device of the embodiment. FIG. 4 shows a connection between a collector terminal and a base terminal incorporated in the amplifier. FIG. 5 is a block diagram showing a schematic configuration of a conventional non-contact IC card reader / writer device. FIG. 6 is a block diagram showing a schematic configuration of a conventional non-contact IC card reader / writer device. FIG. 7 is a time chart illustrating the problems of the conventional non-contact IC card reader / writer device. DESCRIPTION OF SYMBOLS 1 ... Control part 2 ... IC card 3 ... Antenna 4 ... Writing part 5 ... Reading part 6 ... Rectifier circuit 7 ... Detection circuit 8a ... Amplifier 9 ... Comparison circuit 10 ... Decoder 11, 13 ... Pulse waveform 14 ... Bias circuit 15 ... Amplifier circuit

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Chiharu Arai             Henri 5-10-27 Minamiazabu, Minato-ku, Tokyo             Tsu Co., Ltd. F term (reference) 2C005 MA24 NA08 TA22 TA40                 5B058 CA15 CA23 KA02 KA24 KA40                 5J090 AA01 CA02 CN01 FA08 FN06                       FN12 HA02 HA19 HA25 KA00                       KA12 KA17 KA51 KA55 MA21                       SA00 TA02 TA06                 5J500 AA01 AC02 AF08 AH02 AH19                       AH25 AK00 AK12 AK17 AK51                       AK55 AM21 AS00 AT02 AT06                       NC01 NF06 NF12

Claims (1)

Claims 1. An information is written to an attached IC card (2) in a non-contact manner via an antenna (3), and a radio wave output from the attached IC card is provided. A signal obtained by superimposing a transmission data signal on a carrier wave is received via the antenna, the received signal is rectified by a rectifier circuit (6), and the rectified signal output from the rectifier circuit is enveloped by a detector circuit (7). Line detection, the detection signal output from the detection circuit is amplified by an amplifier (8a), the amplified detection signal output from the amplifier is binarized, and a reception data signal corresponding to the transmission data signal is converted to a binary signal. In the obtained non-contact IC card reader / writer device, the amplifier (8a) converts the detection signal including the first transistor (Tr1) having a base terminal to which a detection signal output from the detection circuit is applied. Width amplifying circuit (15), said base terminal of the first transistor and interposed between ground and the collector terminal connected to a base terminal, said first
A non-contact IC card reader / writer, comprising: a second transistor (Tr2) for compensating temperature;