JPH11288447A - Reader/writer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency of radio information communication through electromagnetic connection of loop antennas by a carrier wave with a mobile information communication body such as an IC card. SOLUTION: A transmitting circuit constituted of a local transmitting part 1, a modulating part 2, or an amplifier PA1 transmits a carrier wave through a transformer T1 consisting of a first connection coil P1 provided at a loop antenna L1 and a second connection coil P2 linked by electromagnetic connection with the coil P1 from the loop antenna L1. Also, a detecting part 3 constituting a receiving circuit is connected through a pickup transformer T2 constituted of a first detection coil Q1 interposed between the transmitting circuit and the second connection coil P2 and a second detection coil Q2 connected with the coil Q1 by electromagnetic induction with the antenna L1, and this detecting part 3 detects information included in the carrier wave from a mobile information communication body. Also, a grounding conductor connected with the amplifier PA1 is separated from a grounding conductor connected with the receiving circuit, and those grounding conductors are grounded in parallel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reader / writer which wirelessly communicates information with a mobile information communication body such as an IC card using a loop antenna, and more particularly, to information communication with a mobile information communication body. To a reader / writer that efficiently performs

[0002]

2. Description of the Related Art For example, an IC card formed by embedding a microcomputer chip and a memory chip on a card substrate having a size similar to that of a credit card or the like has been put to practical use in various fields such as finance, distribution, transportation, and medicine. Is planned. In an IC card system using such an IC card, for example, power is transmitted from a reader / writer to the IC card, and information such as control codes and data is communicated between the reader / writer and the IC card.
In power transmission and information communication between a reader / writer and an IC card, in addition to a contact method in which terminals are brought into contact with each other, a non-contact method in which electromagnetic coupling is used.

FIG. 3 shows an example of the configuration of a reader / writer 11 and an IC card 21 provided in an IC card system employing a non-contact method. The reader / writer 11 has, for example, an information processing device (not shown). Is connected. This I
In the C card system, the reader / writer 11 transmits power to the IC card 21 in a non-contact manner, and transmits information received from the information processing device via the interface to the IC card 21.
The reader / writer 11 wirelessly transmits information to the card 21 and wirelessly transmits information to the IC card 21, and transmits the received information to the information processing apparatus via the interface. In the information processing apparatus, for example, processing of data such as finance, distribution, traffic, and medical care received from the reader / writer 11 is performed.

In the IC card system shown in FIG. 1, for example, power transmission and information communication are performed in a state where the loop antenna L3 of the IC card 21 is held over the loop antenna L2 of the reader / writer 11 or the like. The power transmission and the like are performed by electromagnetically coupling the loop antennas L2 and L3 of the two 11 and 21 with the carrier transmitted from the reader / writer 11. In transmitting information from the IC card 21, a communication method using a load switch described later is employed.

Referring to FIG. 3, the reader / writers 11 and I
The operation of the processing performed by the C card 21 will be specifically described. For example, in the reader / writer 11, the carrier transmitted from the local transmission section 12 is transmitted through the modulation section 13 to the amplifier PA 2.
The power is transmitted to the IC card 21 by wirelessly transmitting the amplified carrier from the loop antenna L2 via the impedance conversion transformer T3. In this case, in the loop antenna L2 of the reader / writer 11, a magnetic flux is generated by supplying a carrier wave as a high-frequency current through, for example, the impedance conversion transformer T3.

The reader / writer 11 modulates the carrier wave wirelessly transmitted as described above by the modulator 13 in accordance with the information to be transmitted.
Is transmitted to the user. Here, as a modulation method, for example, an amplitude shift keying (ASK) method or a phase shift keying (PSK) method is used. Note that a resonance capacitor C3 is connected to the loop antenna L2 of the reader / writer 11, and the impedance conversion transformer T3 includes a first coupling coil P3 provided in the loop antenna L2 and an amplifier. A second coupling coil P4 is provided between the output terminal of PA2 and a ground voltage (for example, 0 V).

On the other hand, in the IC card 21, the electric power induced in its own loop antenna L3 by the magnetic flux generated from the loop antenna L2 of the reader / writer 11 is converted into a rectified voltage or a constant voltage via the rectifier diode D or the constant voltage regulator Reg. The power of the constant voltage thus obtained is
And so on. Thus, in the IC card 21, various processing operations are performed using the electric power supplied from the reader / writer 11 in a non-contact manner. The loop antenna L3 of the IC card 21 has a capacitor C for resonance.
4 are connected.

Further, the IC card 21 detects the voltage waveform of the carrier wave induced in its own loop antenna L3 by the detection unit 25 via the rectifier diode D, and transmits the voltage from the reader / writer 11 included in the carrier wave. The detected information is detected, and the detected information is transmitted to, for example, the control unit 26 and stored in a memory.

[0009] In the IC card 21, the carrier wave transmitted from the reader / writer 11, as described above, causes both of the two.
In a state where the loop antennas L2 and L3 of the first and the second 21 are electromagnetically coupled, for example, by controlling the load applied to both ends of the coil constituting the own loop antenna L3 by the control unit 26, the reader / writer 21 is controlled. Wirelessly transmitting information.

As an example, load switches 22 and 23 such as FETs are connected to both ends of a coil constituting a loop antenna L3 of the IC card 21 via capacitors C5 and C6, respectively. By opening and closing the load switches 22 and 23 according to the information to be transmitted by the control unit 26,
Variations due to load are caused in a carrier wave, and the carrier wave is modulated according to information to be transmitted. Note that I
As the load connected to the loop antenna L3 of the C card 21, a resistor can be used instead of the capacitors C5 and C6 described above.

In transmitting information from the IC card 21 due to the above-described load fluctuation, for example, the control unit 26 controls a circuit load applied to an output terminal of the constant voltage regulator Reg of the IC card 21 on the control unit 26 side. It can also be done by In this case, for example, IC card 2
A load switch 24 such as an FET is connected to the output terminal of the constant voltage regulator Reg on the control unit 26 side via a resistor R2.
By opening and closing the load switch 24 by 6, the above-described carrier is modulated and the information is wirelessly transmitted to the reader / writer 11.

In the IC card 21 shown in FIG. 3, for convenience of explanation, the load switches 22 and 23 for controlling the load connected to the loop antenna L3 and the load for controlling the load connected to the constant voltage regulator Reg are controlled. Although the configuration example including both the load switch 24 and the
The card 21 can transmit information to the reader / writer 11 if any of the load switches is provided.

On the other hand, in the reader / writer 11, when the load is applied to the carrier by the IC card 21 as described above, the impedance of the impedance conversion transformer T3 is changed due to the load change. In the reader / writer 11, for example, the amplitude of the voltage waveform of the carrier at the output terminal of the amplifier PA2 is detected by the detecting unit 14 using such a change in impedance, and transmitted from the IC card 21 based on the change in the amplitude. The received information is processed.

That is, the detecting unit 14 of the reader / writer 11
Then, the voltage waveform of the carrier at the output terminal of the amplifier PA2 is detected by the detector 16 via the resistor R1 and the buffer 15, and the amplitude of the detected voltage waveform of the carrier is compared with the comparator 17
By comparing with a threshold value set in advance by
Reproduction of information from the card 21 is performed.

Here, the voltage value (detection value) of the carrier detected by the detection unit 14 of the reader / writer 11 will be described in more detail. For example, the impedance of the second coupling coil P4 constituting the impedance conversion transformer T3 of the reader / writer 11 when the load fluctuation is not generated in the carrier by the IC card 21 is set to "
Z1 ", the output impedance of the amplifier PA2 is" Z2 ", and the voltage value of the carrier output from the amplifier PA2 is" V3 "when the output impedance of the amplifier PA2 is considered to be zero. Under these conditions, the first detection value V detected by the detection unit 14
4 is given by equation 1. In FIG. 3, for convenience of explanation, the output impedance of the amplifier PA2 is shown as a resistance connected to the output terminal of the amplifier PA2.

[0016]

(Equation 1)

When the output impedance is assumed to be zero, the voltage value V3 output from the amplifier PA2 is
Is assumed to be constant, for example, when the load fluctuation is caused in the carrier by the IC card 21, the reader / writer 11
Of the second coupling coil P4 is "Z1 +
y ”, the detector 14 under these conditions.
The second detection value V4y detected by the following equation is expressed by Expression 2. The change amount y of the impedance of the second coupling coil P4 is, for example, 1 of the impedance Z1 before the change.
%.

[0018]

(Equation 2)

The detector 14 can more reliably detect information from the IC card 21 as the difference V4c between the second detection value V4y and the first detection value V4 increases. Here, the difference V4c between the two detection values is represented by, for example, the absolute value of the difference between the two detection values as shown in Expression 3, and the difference V4c
Reference numeral 4c denotes a component of a voltage change generated in the detected value of the carrier wave due to the load fluctuation of the IC card 21.

[0020]

(Equation 3)

According to the above equations (1) to (3), when the output impedance Z2 of the amplifier PA2 is substantially equal to the impedance Z1 of the second coupling coil P4, the first detection value V4 and the second detection value The difference V4c from V4y is maximized. Further, the second coupling coil P is supplied from the amplifier PA2.
4 as well, when impedances Z1 and Z2 of both PA2 and P4 are substantially equal, impedance matching is achieved and loss due to mismatching is reduced.

On the other hand, according to the above equations (1) to (3), the amplifier P
When the output impedance Z2 of A2 is zero or very large (for example, when it can be regarded as infinity), the first detection value V4 and the second detection value V4y
V4c is always zero, and the detection unit 14
Information from the card 21 cannot be detected.

Therefore, the detection unit 1 as described above is used.
In the method of detecting information at step 4, when the output impedance of the amplifier PA2 is reduced to be close to zero, impedance matching cannot be achieved between the amplifier PA2 and the second coupling coil P4. As described above, the information from the IC card 21 cannot be detected. However, in general, the amplifier PA2 whose output impedance is closer to zero realizes an ideal operation in terms of the stability of amplification degree and the like. As described above, the demand for the output impedance of the amplifier PA2 conflicts. Therefore, information communication with the IC card 21 cannot be efficiently performed by the method of detecting information by the detection unit 14 as described above.

FIG. 4 shows how each processing unit of the reader / writer 11 shown in FIG. 3 is grounded. That is, in the reader / writer 11, a local oscillator 12, a modulator 13, and an amplifier P which constitute a transmission circuit for transmitting a carrier wave.
A2, the detector 16 and the comparator 17 forming a receiving circuit for detecting information from the IC card 21 are the same ground line G.
3 and the ground line G3 is grounded.

However, a large current flows in the transmission circuit of the reader / writer 11, and particularly a very large current flows in the amplifier PA2. Therefore, in the above-described grounding method, for example, the influence of noise from the amplifier PA2 is reduced. Line G
There is a problem that the signal is transmitted to the receiving circuit through the third circuit 3 and causes interference by noise in the receiving circuit. For this reason, in the detection unit 16 and the like of the reader / writer 11, many bit errors occur in the information received from the IC card 21, and information communication with the IC card 21 cannot be performed efficiently.

FIG. 5 shows another example of the configuration of the reader / writer. As shown in FIG. 5, a current detecting resistor R3 for detecting the current output from the amplifier PA2 is connected to the second coupling coil P4.
A configuration for detecting information from the IC card 21 included in the carrier by examining the voltage waveform of the carrier applied to the current detection resistor R3 by using the detector 32 or the like is provided. ing. In the configuration of the reader / writer shown in FIG. 3, the resistor R4 and the buffer 3 constituting a receiving circuit for detecting information from the IC card 21 are provided.
1, processing units other than the detector 32 and the comparator 33 are denoted by the same reference numerals as those in FIG.
FIG. 3 also shows a loop antenna L3 and the like constituting the IC card 21 together with the configuration of the reader / writer.

Also in the configuration of the reader / writer shown in FIG. 5, information communication is performed by utilizing the fact that the impedance of the impedance conversion transformer T3 of the reader / writer changes due to the above-described load fluctuation by the IC card 21. However, in this configuration, unlike the configuration shown in FIG. 3, it is possible to detect information from the IC card 21 even if the output impedance of the amplifier PA2 is reduced.

However, in the configuration of the reader / writer shown in FIG. 5, for example, a low noise amplifier (LN
A) It is necessary to increase the resistance value of the current detection resistor R3 in order to increase the voltage value of the carrier wave detected without providing the current detection resistor R3.
There is a problem that the power consumed by the heat generation in No. 3 increases. For example, if such power consumption increases, the power supplied to the loop antenna L2 may decrease, and information communication with the IC card 21 cannot be performed efficiently.

In the configuration of the reader / writer shown in FIG. 5, as in the case of the reader / writer shown in FIG. 3, since the transmission circuit and the reception circuit are grounded by the same ground line, the amplifier There has been a problem that noise from the PA2 affects the receiving circuit due to interference.

[0030]

SUMMARY OF THE INVENTION As described above,
In the conventional reader / writer, any of the configurations shown in FIGS. 3 and 5 has a drawback that information communication with the IC card cannot be performed efficiently. A configuration in which information can be efficiently detected from a carrier by a receiving circuit has not been realized.

The present invention has been made in order to solve such a conventional problem.
A reader / writer capable of efficiently communicating information when wirelessly communicating information with the mobile information communication body by electromagnetically coupling the loop antenna of the mobile information communication body such as a card with a carrier wave by a carrier wave. The purpose is to provide. More specifically, for example, FIG.
A reader / writer that can reduce the output impedance of the amplifier PA2 shown in FIG. 3 even if the configuration for information detection by the current detection resistor R3 shown in FIG.
This realizes a reader / writer in which noise from the amplifier PA2 does not affect the receiving circuit.

[0032]

In order to achieve the above object, in a reader / writer according to the present invention, a carrier wave is transmitted to a mobile information communication body using a first loop antenna by the following configuration, By electromagnetically coupling the first loop antenna and the second loop antenna provided on the mobile information communication body by a carrier wave, information is wirelessly communicated with the mobile information communication body.

That is, in the reader / writer, the first loop antenna is provided with the first coupling coil, and the second coupling coil is coupled to the first coupling coil by electromagnetic induction. And the transmission circuit is
Are coupled to the first loop antenna via the coupling coil and the first coupling coil to transmit a carrier. In the reader / writer, a first detection coil is interposed between the transmission circuit and the second coupling coil, and the second detection coil is coupled to the first detection coil by electromagnetic induction. Is provided, and the receiving circuit is
And the first detection coil and the first detection coil are coupled to the first loop antenna to detect information transmitted from the mobile information communication unit and included in the carrier.

As described above, in the reader / writer, the transmission circuit and the reception circuit, and the second coupling coil and the reception circuit are non-contactly coupled by the first detection coil and the second detection coil. The circuit detects information from the mobile information communication body by demodulating, for example, a voltage induced in the second detection coil due to a change in current of a carrier flowing through the first detection coil. .

Therefore, in the reader / writer of the present invention, if the output impedance of the amplifier constituting the transmission circuit is reduced as shown in FIG. 3 of the conventional example, information from the mobile information communication body cannot be received. Such an inconvenience does not occur, and information can be efficiently communicated with the mobile information communication body by reducing the output impedance of such an amplifier. In the reader / writer of the present invention,
For example, since it is not necessary to provide a current detection resistor as shown in FIG. 5 of the conventional example, there is no problem that a large amount of power is consumed by the current detection resistor, and information can be efficiently exchanged with the mobile information communication body. Can communicate.

In the reader / writer of the present invention, for example, by increasing the number of turns of the second detection coil as compared with the number of turns of the first detection coil described above, the reader / writer can further communicate with the mobile information communication body. Can improve the efficiency of information communication.

Further, in the reader / writer according to the present invention, a carrier is transmitted to the mobile information communication body using the first loop antenna, and the second loop provided on the first loop antenna and the mobile information communication body is provided. The circuit was grounded as follows when wirelessly communicating information with a mobile information communication body by electromagnetically coupling the antenna with a carrier. That is, a ground line connected to an amplifier constituting a transmission circuit for transmitting a carrier wave coupled to the first loop antenna, and transmitted from a mobile information communication body contained in the carrier wave coupled to the first loop antenna. A ground line connected to a receiving circuit for detecting information was provided separately, and these ground lines were grounded in parallel.

Therefore, in the reader / writer, for example, even when a large current flows through the amplifier constituting the transmission circuit, noise from the amplifier affects the reception circuit via the ground line due to interference. Since this does not occur, it is possible to prevent an error from occurring in the information received from the mobile information communication body, and thereby it is possible to efficiently communicate information with the mobile information communication body.

Here, the mobile information communication body referred to in the present invention includes not only the above-mentioned IC card but also a name plate attached to a person, a tag attached to a product or article, or a livestock. Such as an identification plate, a delivery destination plate attached to a parcel of home delivery, a delivery destination plate attached to a container, and the like. In addition, the mobile information communication body to which the present invention can be applied is not limited to the above-described mobile information communication body, and the present invention provides that the own loop antenna and the loop antenna of the reader / writer are electromagnetically coupled by a carrier wave. Thus, the present invention can be widely applied to various mobile information communication bodies that wirelessly communicate information with a reader / writer.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment according to the present invention will be described with reference to the drawings. In this example, the mobile information communication body is an IC
A case where a card is used will be described, and a case where information is wirelessly communicated with an IC card by the reader / writer according to the present invention will be described. The configuration of the IC card of the present embodiment for performing information communication with the reader / writer of the present embodiment described below is, for example, the same as that of the IC card 21 shown in FIG. Between the reader / writer of the present embodiment and the IC card of this embodiment, for example, in a state where the loop antenna of the IC card is held over the loop antenna of the reader / writer and the like, the two loop antennas are electromagnetically coupled by a carrier wave to perform information communication. Is performed.

Further, in the IC card of this embodiment, similarly to the case of the IC card 21 shown in FIG. 3, for example, various operations are executed using the power extracted from the carrier wave received from the reader / writer, and By controlling a load switch connected to a loop antenna or the like, a carrier wave is modulated and information is wirelessly transmitted to a reader / writer. As described above, since the configuration and operation of the IC card of this embodiment are the same as those shown in FIG. 3, the description of the configuration and operation is omitted in this embodiment.

Further, for example, an information processing device (not shown) is connected to the reader / writer of this embodiment via an interface. In this embodiment, the reader / writer is controlled by this information processing device to perform various processing operations. Will be Here, for example, the information processing apparatus has a function of transmitting information to be transmitted wirelessly to an IC card to a reader / writer,
A function of receiving information wirelessly received from the C card from the reader / writer, a function of processing data such as finance, distribution, transportation, and medical care received from the reader / writer in this manner are provided.

Hereinafter, the configuration and operation of the reader / writer of this embodiment will be described with reference to FIGS. FIG. 1 shows a configuration example of a reader / writer according to the present invention. The reader / writer includes a loop antenna L1 to which a resonance capacitor C1 is connected, and an impedance conversion transformer T1 for coupling a circuit by electromagnetic induction. , A local oscillator 1 for transmitting a carrier, a modulator 2 for modulating a carrier, an amplifier PA1 for amplifying the carrier, a pickup transformer T2 for coupling a circuit by electromagnetic induction, and an I included in the carrier.
A detection unit 3 for detecting information from the C card.

The loop antenna L1 is composed of, for example, a coil wound in a rectangular shape or the like. It has a function of generating a voltage.

The impedance conversion transformer T1 includes a first coupling coil P1 interposed between a resonance capacitor C1 connected to one end of a coil constituting the loop antenna L1 and the other end of the coil, and a first coupling coil P1. 1 coupling coil P1
And a second coupling coil P2 coupled by electromagnetic induction. One end of the second coupling coil P2 is connected to a ground voltage (for example, 0 V), while the second coupling coil P2 Is connected to a first detection coil Q1 described later.

The local transmission unit 1 has a function of transmitting a carrier wave, and outputs the carrier wave to the modulation unit 2 in this example.
The modulator 2 has a function of modulating a carrier. In this example, the modulator 2 modulates a carrier input from the local oscillator 1 according to information to be transmitted, and outputs the modulated carrier to the amplifier PA1. Note that, as described above, the information to be transmitted is input from, for example, an external information processing device to the modulation unit 2, and is input from the local transmission unit 1 when the information is not received from the information processing device. The carrier is output to the amplifier PA1 without being modulated. As a method of modulating a carrier, an amplitude shift keying (ASK) method or a phase shift keying (P
Various methods such as the (SK) method may be used.

The amplifier PA1 has a function of amplifying a carrier, and in this example, amplifies the carrier inputted from the modulation section 2 and sends the amplified carrier to a first detection coil Q1, for example, a high-frequency current. Output as This allows
The carrier output from the amplifier PA1 is output to the second coupling coil P2 via the first detection coil Q1.
In FIG. 1, for convenience of explanation, the output impedance of the amplifier PA1 is shown as a resistance connected to the output terminal of the amplifier PA1.

In this example, a transmission circuit is constituted by the above-described local oscillation section 1, modulation section 2 and amplifier PA1, and the transmission circuit is composed of the second coupling coil P2 and the first coupling coil as described above. It is coupled to the loop antenna L1 via P1. With such a configuration, the transmitting circuit transmits a carrier as a magnetic flux from the loop antenna L1, and transmits information to the IC card by modulating the carrier.

The configuration of the pickup transformer T2 and the circuit on the receiving side provided in the reader / writer of this embodiment will be described. The pickup transformer T2 includes a first detection coil (primary coil) Q1 interposed between the output terminal of the amplifier PA1 and the second coupling coil P2 constituting the transmission circuit, and a first detection coil Q1. It comprises a detection coil Q1 and a second detection coil (secondary coil) Q2 coupled by electromagnetic induction, and one end of the second detection coil Q2 is connected to a ground voltage (for example, 0 V). On the other hand, the other end of the second detection coil Q2 is connected in parallel with a later-described matching capacitor C2 and a buffer 4.

In such a pickup transformer T2,
For example, when an induced electromotive voltage is generated in the second detection coil Q2 due to a change in the current flowing in the first detection coil Q1, the change in the carrier wave flowing in the first detection coil Q1 is changed to the second. Can be picked up as a voltage by the detecting coil Q2. In the present example, as a preferred embodiment, the first detection coil Q1 is 1
While the second detection coil Q2 is composed of a coil having a sufficiently large number of turns (N turns) as compared with 1, the second detection coil Q2 has a load impedance of the second detection coil Q2. Is increased, the voltage taken out by the second detection coil Q2 is increased.

When the pickup transformer T2 is configured with such a number of turns of the coil, the impedance of the second detection coil Q2 is much larger than that of the first detection coil Q1, so that The effect of the impedance of the second detection coil Q2 on the first detection coil Q1 can be made substantially zero. For example, when it can be considered that the second detection coil Q2 side is open (OPEN), the inductance of the first detection coil Q1 side should be reduced to a negligible level. it can.

Further, in the configuration of the present embodiment, the number of turns of the first detection coil Q1 is suppressed to one turn which is the minimum number of turns, and the inductance of the first detection coil Q1 is suppressed to a small value. Therefore, the effect of the first detection coil Q1 on the loop antenna L2, the amplifier PA1, and the like can be made substantially zero.

The detecting unit 3 includes a matching capacitor C2 having a function of matching circuits, a buffer 4 having a function of temporarily storing a voltage value, and a detector 5 having a function of detecting a voltage waveform. And a comparator 6 having a function of comparing a voltage value of the detected voltage waveform with, for example, a preset threshold value. Matching capacitor C2
Is provided between the second detection coil Q2 and the ground voltage (for example, 0 V) to match the impedance of the circuit.

The input end of the buffer 4 is connected to the above-described second detection coil Q2. In this embodiment, the input of the buffer 4 is induced in the second detection coil by a change in the carrier wave constantly flowing through the first detection coil Q1. The stored voltage value is temporarily stored, and the stored voltage value is output to the detector 5. For example, a low noise amplifier (LNA) or the like may be provided between the second detection coil Q2 and the detector 5 instead of the buffer 4.

In this example, the detector 5 detects a voltage waveform from the voltage value input from the buffer 4 and outputs the detected voltage waveform to the comparator 6. The comparator 6 is a detector 5 in this example.
Then, the voltage value of the voltage waveform input from is compared with the above-described threshold value, and the information transmitted from the IC card is reproduced based on the comparison result.

With such a configuration, the detecting unit 3 detects the change in the carrier current flowing through the first detecting coil Q1 in the second detecting coil Q1.
The information is wirelessly transmitted from the IC card by detecting the information contained in the carrier wave from the IC card by inputting it as a voltage through the detection coil Q2. Further, the detection unit 3 of the present example transmits the information received in this manner to an external information processing device. In the present example, the capacitor C2, the buffer 4, the detector 5, the comparator 6
Thus, a receiving circuit that is coupled to the loop antenna L1 via the second detection coil Q2 and the first detection coil Q1 and detects information transmitted from the IC card included in the carrier wave is configured.

Here, the above-mentioned pickup transformer T
The voltage value input to the detection unit 3 via the control unit 2 will be described in more detail. In a reader / writer, for example, I
When the load switch is opened and closed by the C card and the load is changed on the carrier wave, whereby information is wirelessly transmitted from the IC card, the impedance of the impedance conversion transformer T1 is changed due to the load change. . In the reader / writer, the current of the carrier flowing through the first detection coil Q1 constituting the pickup transformer T2 changes due to such a change in impedance.

For example, the impedance of the second coupling coil P2 constituting the impedance conversion transformer T1 of the reader / writer when the load fluctuation is not generated in the carrier by the IC card is set to "ZL", and the output of the amplifier PA1 is set. Assuming that the impedance is “Z0” and the voltage value of the carrier output from the amplifier PA1 is “V1” when the output impedance of the amplifier PA1 is considered to be zero, the first detection coil The first current value i flowing through Q1 is expressed by Equation 4.

[0059]

(Equation 4)

When the output impedance is assumed to be zero, voltage value V1 output from amplifier PA1
Is constant, the impedance of the second coupling coil P2 of the reader / writer becomes "ZL" due to the load fluctuation generated in the carrier wave by the IC card of the communication partner.
+ X ", the second current value ix flowing through the first detection coil Q1 under such conditions is expressed by Equation 5.

[0061]

(Equation 5)

For example, when the value of the current flowing through the first detection coil Q1 changes from the first current value i to the second current value ix, the second detection coil Q2 outputs the current value i , Ix, a voltage value V2 corresponding to the difference ic is induced,
Such a voltage value is input to the detection unit 3. Here, when the difference ic between the two current values i and ix is represented by, for example, the absolute value of the difference between the two current values, the difference ic is expressed by Expression 6. Note that the difference ic indicates a component of a current change generated in the carrier wave due to a load change of the IC card.

[0063]

(Equation 6)

As shown in the above formulas (4) to (6), the difference ic between the two current values i and ix becomes maximum when the output impedance Z0 of the amplifier PA1 is zero. Even when the output impedance of the PA 1 is set to almost zero, the information transmitted from the IC card can be detected by the detection unit 3.

As described above, in the reader / writer of this example,
A carrier wave is transmitted to the IC card using its own loop antenna L1, and information is wirelessly transmitted to and from the IC card by electromagnetically coupling the own loop antenna L1 and the loop antenna provided on the IC card by the carrier wave. When communicating, the communication of the information can be performed efficiently. Specifically, as described above, in the reader / writer of this example, for example, the output impedance of the amplifier PA1 forming the transmission circuit is small, and the impedance conversion transformer T1
Even when impedance matching with the carrier is not achieved, information transmitted from the IC card included in the carrier can be detected with sufficient sensitivity.

Further, in the reader / writer of this embodiment, the impedance of the second detection coil Q2 side is larger than that of the first detection coil Q1 constituting the pickup transformer T2. Information from the IC card included in the carrier can be detected with sufficient sensitivity without affecting the output power or the power supplied to the own loop antenna L1. Also,
In the reader / writer of this example, for example, since the current detection resistor as shown in FIG. 5 is not provided, a large amount of power is not consumed by such a current detection resistor.

Next, with reference to FIG. 2, a description will be given of a configuration example in which each processing unit of the reader / writer of the present embodiment shown in FIG. 1 is grounded. As shown in the figure, in the reader / writer of this example,
Local oscillator 1, modulator 2, and amplifier P that constitute a transmission circuit
A1 is connected to a first ground line G1 connected to a detector 5 and a comparator 6 forming a receiving circuit.
Are provided separately, and these ground lines G1, G
2 are grounded in parallel. In this example, these ground lines G1 and G2 are grounded at one point at the power output supplied to the reader / writer.

As described above, in the reader / writer of the present embodiment, the ground line connected to the transmission circuit and the ground line connected to the reception circuit are separated and these ground lines are grounded in parallel. Noise generated from the transmission circuit does not affect the reception circuit, and in particular, noise generated from the amplifier PA1 through which a large current flows can be prevented from affecting the reception circuit. Thereby, in the receiving circuit, for example, the signal-to-noise ratio (S / N ratio) related to the input and output of the detector 5 can be increased, and the bit error rate generated in the information received from the IC card can be reduced. it can. As described above, in the reader / writer of this example, I
Information can be efficiently wirelessly communicated with the C card.

Here, in the reader / writer shown in the above embodiment, by providing the pickup transformer T2 between the amplifier PA1 and the second coupling coil P2, the receiving circuit can be connected to the loop antenna via the pickup transformer T2. Means for coupling the receiving circuit to the loop antenna as described above, for example, means for coupling using electromagnetic induction between the first detection coil and the second detection coil Then, any means may be used.

The configuration of the pickup transformer is not limited to the above, and other configurations of the reader / writer are not necessarily limited to those described in the above embodiments.
Various configurations may be used. As an example, in the above embodiment, an external information processing apparatus connected to the reader / writer has a configuration including a function of controlling the reader / writer and a function of processing various types of information. A configuration integrated with a control function, an information processing function, and the like of the processing device may be used.

In the above-described embodiment, the case where information is wirelessly communicated between the IC card and the reader / writer is shown as an example of the mobile information communication body. ICs are not necessarily ICs
Not limited to a card, various mobile information communication bodies may be used. Also, as the configuration of the mobile information communication body, any configuration may be used as long as both loop antennas are electromagnetically coupled with a reader / writer by a carrier wave to wirelessly communicate information. In the case where, for example, a battery or a battery is built in the mobile information communication body, a circuit for extracting power from the carrier transmitted by the reader / writer may not be provided in the mobile information communication body.

[0072]

As described above, according to the reader / writer according to the present invention, the IC is implemented by using the first loop antenna.
Transmitting a carrier wave to a mobile information communication body such as a card,
When the first loop antenna and the second loop antenna provided in the mobile information communication body are electromagnetically coupled by a carrier wave, the first loop antenna is used for wireless communication of information with the mobile information communication body. The transmitting circuit is coupled to the first loop antenna via the second coupling coil coupled to the first coupling coil provided by electromagnetic induction, and the transmission circuit is coupled between the transmission circuit and the second coupling coil. Since the receiving circuit is coupled to the first loop antenna via the second detection coil coupled to the first detection coil mounted by electromagnetic induction, for example, the output impedance of the amplifier constituting the transmission circuit is reduced. Even if the size is reduced, information transmitted from the mobile information communication body can be received by the receiving circuit, etc. It is possible to streamline communications.

According to the reader / writer of the present invention, a carrier wave is transmitted to the mobile information communication body using the first loop antenna, and the second loop antenna provided on the first loop antenna and the mobile information communication body is provided. By electromagnetically coupling the loop antenna with a carrier, when wirelessly communicating information with a mobile information communication body, a ground line connected to an amplifier constituting a transmission circuit and a ground line connected to a reception circuit are connected. Since the ground lines are separated and grounded in parallel, it is possible to prevent noise generated from, for example, an amplifier of the transmission circuit from affecting the reception circuit, thereby providing a communication between the mobile information communication body. Information communication can be made more efficient.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of a reader / writer according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration example in which a transmission circuit and a reception circuit of a reader / writer are grounded.

FIG. 3 is a diagram showing a configuration example of an IC card system according to a conventional example.

FIG. 4 is a diagram showing a configuration in which a transmission circuit and a reception circuit of a conventional reader / writer are grounded.

FIG. 5 is a diagram illustrating another configuration example of a conventional reader / writer.

[Explanation of symbols]

1. Local oscillator, 2. Modulator, 3. Detector,
4 buffer, 5 detector, 6 comparator
L1 loop antenna, C1, C2 capacitor
P1, P2 ... coupling coil, T1 ... impedance conversion transformer, Q1, Q2 ... detection coil, T2
..Pickup transformers, G1, G2..Grounding wires,

Continued on the front page (72) Inventor Keisuke Igarashi 3-14-20 Higashinakano Nakano-ku Tokyo

Claims (2)

[Claims] A carrier is transmitted to a mobile information communication body using a first loop antenna, and the first loop antenna and a second loop antenna provided in the mobile information communication body are electromagnetically coupled by the carrier. Thereby, in the reader / writer that wirelessly communicates information with the mobile information communication body, the first coupling coil provided in the first loop antenna, and the first coupling coil coupled to the first coupling coil by electromagnetic induction. 1 through the second coupling coil, the second coupling coil and the first coupling coil.
A transmitting circuit coupled to the loop antenna for transmitting a carrier wave; and a first circuit interposed between the transmitting circuit and the second coupling coil.
, A second detection coil coupled to the first detection coil by electromagnetic induction, and a first detection coil via the second detection coil and the first detection coil.
And a receiving circuit coupled to the loop antenna for detecting information transmitted from the mobile information communication body included in the carrier. 2. A carrier wave is transmitted to a mobile information communication body using a first loop antenna, and the first loop antenna and a second loop antenna provided in the mobile information communication body are electromagnetically coupled by the carrier wave. Accordingly, in a reader / writer that wirelessly communicates information with a mobile information communication body, a transmission circuit coupled to a first loop antenna to transmit a carrier, and a transmission circuit coupled to the first loop antenna and included in a carrier A receiving circuit for detecting information transmitted from the mobile information communication body, and a ground line connected to an amplifier constituting the transmitting circuit and a ground line connected to the receiving circuit. A reader / writer characterized by being grounded in parallel.