JP2007329589A - Communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication apparatus capable of executing contactless data communication with a communication object more surely than before. <P>SOLUTION: The communication apparatus 3 is provided with: a signal source SG for generating an AC signal; an antenna 6 for emitting the AC signal supplied from the signal source SG to the communication object 2 to transmit power to the communication object 2 in a non-contact manner; a phase difference detection means 13 for detecting a phase difference between a phase of the AC signal outputted from the signal source SG and a phase of the AC signal flowing through the antenna 6; and a power control means 15 for reducing power received by the communication object 2 on the basis of the phase difference detected by the phase difference detection means 13. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a communication apparatus, and is suitable for application to, for example, a reader / writer that performs data communication with a non-contact IC (Integrated Circuit) card.

  In recent years, contactless IC card systems using contactless IC cards have become widespread in various fields such as station ticket gates, security systems, and electronic money systems (see, for example, Patent Document 1).

  Such a non-contact IC card system includes a reader / writer that performs non-contact power transmission and signal communication, and a non-contact type IC card 33 that incorporates an IC chip, an antenna, and the like. Each reader / writer and IC card is provided with an antenna formed of a coil wound in a square shape, etc., and includes power transmission and information by electromagnetic coupling between the reader / writer antenna and the IC card antenna. Communication of the signal is performed.

  That is, the reader / writer generates an alternating magnetic field from the antenna by flowing an AC signal to its own antenna, and induces a current in the antenna of the IC card located in the vicinity by the alternating magnetic field. To transmit power and signals.

  The IC card does not have a power source inside, and is activated and operated using the power received from the reader / writer, and performs various processes such as transmission of a response signal to the reader / writer. Signal transmission from the IC card to the reader / writer is performed, for example, using a carrier wave that carries transmission power from the reader / writer.

The signal transmitted from the IC card to the reader / writer is received via the antenna of the reader / writer as in the case of power transmission and signal transmission from the reader / writer to the IC card. In general, a reader / writer has a communicable area in which power transmission and signal communication can be performed with an IC card, and the power transmission and signal communication between the reader / writer and the IC card described above are This is performed in a state where an IC card exists in the communicable area of the reader / writer. In general, the tuning frequency of both the reader / writer antenna and the IC card antenna is set to be the same (for example, 13.56 [MHz]).
JP 2005-318385 A

  In the non-contact IC card system described above, the power received by the IC card varies depending on the distance between the reader / writer antenna and the IC card antenna. For this reason, when the reader / writer and the IC card are separated from each other, the power received by the IC card decreases, and the IC card cannot operate normally. On the other hand, when the reader / writer is close to the IC card, excessive power is supplied to the IC card, the temperature of the IC chip built in the IC card rises, or in the worst case, the IC chip is damaged. Therefore, there is a problem that data communication between the reader / writer and the IC card cannot be normally performed.

  The present invention has been made in consideration of the above points, and proposes a communication apparatus that can perform non-contact data communication more reliably than in the past.

In order to solve such a problem, in the communication device of the present invention, an AC signal is generated in a communication device that transmits power to a communication target in a contactless manner and performs data communication with the communication target in a contactless manner. A signal source, an antenna that radiates an AC signal supplied from the signal source and transmits power to a communication target in a contactless manner, a phase of the AC signal output from the signal source, and a phase of the AC signal flowing through the antenna The communication apparatus is provided with a phase difference detection unit that detects a phase difference between the communication device and a power control unit that reduces power received by the communication target based on the phase difference detected by the phase difference detection unit.

  The power control unit detects that the distance between the communication device and the communication target is close based on the increase in the phase difference detected by the phase difference detection unit, and reduces the voltage of the AC signal output from the signal source. As a result, the power received by the communication target is reduced.

  In addition, the power control unit detects that the distance between the communication device and the communication target is close based on the increase in the phase difference detected by the phase difference detection unit, and changes the resonance frequency of the antenna. Reduced received power.

  In this way, the communication device detects that the communication device and the communication target are close based on the increase in the phase difference between the AC signal supplied from the signal source and the AC signal flowing through the antenna, and reduces the voltage of the AC signal. By changing the resonance frequency of the antenna or the antenna, it is possible to reduce the power received by the communication object that is approached, and always perform reliable non-contact data communication regardless of the distance between the communication apparatus and the communication object.

  According to the present invention, the proximity of the communication device and the communication target is detected based on the increase in the phase difference between the AC signal supplied from the signal source and the AC signal flowing through the antenna, and the voltage of the AC signal is reduced. By changing the resonant frequency of the antenna, the power received by the close communication target is reduced, realizing a communication device that can always perform reliable non-contact data communication regardless of the distance between the communication device and the communication target can do.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

(1) Configuration of Non-contact IC Card System In FIG. 1, reference numeral 1 denotes a non-contact IC card system as a whole, which includes a non-contact type IC card 2 and a reader / writer 3 that reads and writes data from / to the IC card 2. It is configured. The reader / writer 3 as a communication device acquires data to be written to the IC card 2 from an external device (not shown), and transmits data read from the IC card 2 to the external device.

  In practice, the reader / writer 3 sends a transmission unit 7 for transmitting data to the IC card 2 via the antenna 6, and an antenna 6 from the IC card 2 to the control unit 5 that performs overall control. And a receiving unit 8 for receiving data via the connection. On the other hand, the IC card 2 is configured such that a transmission / reception unit 12 for transmitting / receiving data to / from the reader / writer 3 via the antenna 11 is connected to the control unit 10.

  Then, the reader / writer 3 transmits, to the control unit 5 that controls the entire system, a transmission unit 7 for transmitting data to the IC card 2 via the antenna 6, and the IC card 2 via the antenna 6. A receiving unit 8 for receiving data is connected. On the other hand, the IC card 2 is configured such that a transmission / reception unit 12 for transmitting / receiving data to / from the reader / writer 3 via the antenna 11 is connected to the control unit 10.

  Then, the reader / writer 3 generates an alternating magnetic field by passing an AC signal through the antenna 6 and induces a current in the antenna 11 of the IC card 2 to transmit electric power and signals to the IC card 2.

(2) Control of transmission power according to the present invention FIG. 2 shows an equivalent circuit of a transmission / reception system in the IC card 2 and the reader / writer 3, and the reader / writer 3 has a predetermined frequency by a signal source SG provided in the transmission section 7 (FIG. 1). And an alternating magnetic field corresponding to the alternating current flowing through the antenna 6 is radiated from the antenna 6 to the space by resonating it with a resonance circuit comprising the resistor R1, the capacitor C1, and the antenna 6 as a coil. To do.

  On the other hand, the IC card 2 resonates the voltage induced in the antenna 11 by the alternating magnetic field radiated from the reader / writer 3 by a resonance circuit including the resistor R2, the capacitor C2, and the antenna 11 as a coil, and the alternating current flowing through the antenna 11 To operate the control unit 10 (FIG. 1).

  Here, when the tuning frequencies of the IC card 2 and the reader / writer 3 are both 13.56 [MHz], the current I flowing through the antenna 6 of the reader / writer 3 is given by the following equation. However, Qr = w · C1 · R1, Qc = w · C2 · R2, and w = 2π × 13.56 [MHz].

  From equation (1), it can be seen that the phase of the current flowing through the antenna 6 of the reader / writer 3 depends on the coupling coefficient k (that is, the distance between the reader / writer 3 and the IC card 2). Therefore, the distance between the reader / writer 3 and the IC card 2 can be determined based on the phase of the current. Therefore, in the configuration shown in FIG. 2, the phase difference between the current (or voltage) flowing through the antenna 6 of the reader / writer 3 and the signal source SG is detected, and the power source voltage of the signal source SG is based on the value obtained by integrating the phase difference. If the reader / writer 3 and the IC card 2 are approached, the power output from the reader / writer 3 is reduced so that the power received by the IC card 2 becomes excessive. Can be prevented.

  That is, as illustrated in FIG. 3, the transmission unit 7 of the reader / writer 3 determines, for example, an Ex-OR ((Exclusive-OR: exclusive logic) voltage phase difference between the AC signal output from the signal source SG and the signal flowing through the antenna 6. The phase difference is detected by a phase difference detector 13 composed of a circuit, and the phase difference is integrated by a low-pass filter 14 and supplied to the voltage controller 15 as a phase difference detection signal.

  Based on the value of the phase difference detection signal, the voltage control unit 15 as the power control means, when the phase difference between the voltage of the AC signal output from the signal source SG and the signal flowing through the antenna 6 exceeds a predetermined threshold, the reader / writer 3 In order to prevent the power received by the IC card 2 from being excessively close to the IC card 2, the voltage of the AC signal output from the signal source SG is reduced.

  As a result, the reader / writer 3 reduces the power transmitted from the antenna 6 when the IC card 2 approaches excessively, and limits the power received by the adjacent IC card 2.

(3) Operation and Effect In the above configuration, the transmission unit 7 of the reader / writer 3 detects the phase difference between the AC signal output from the signal source SG and the voltage of the signal flowing through the antenna 6 by the phase difference detection unit 13, and the reader Based on the phase difference that changes according to the distance between the writer 3 and the IC card 2, when the IC card 2 approaches, the voltage of the AC signal output from the signal source SG is reduced.

  As a result, the reader / writer 3 reduces the power transmitted from the antenna 6 when the IC card 2 is excessively approached, and prevents excessive power from being received by the approached IC card 2. 2 damage can be prevented.

  In addition to this, the reader / writer 3 reduces the transmission power when the IC card 2 is excessively approached as described above. Therefore, the reader / writer 3 has an appropriate interval between the assumed standard reader / writer 3 and the IC card 2. The power transmitted from the antenna 6 can be set so that the power can be received by the IC card 2, and thus the IC card 2 can be operated properly even if the distance from the IC card 2 changes variously. Communication can be performed.

  According to the above configuration, by adjusting the transmission power according to the interval with the IC card 2, it is possible to always operate the IC card 2 appropriately and perform data communication.

(4) Other Embodiments In the above-described embodiment, the case where the present invention is applied to the reader / writer 3 as a communication device that performs non-contact data communication with the IC card 2 has been described. However, the present invention can be applied to various other communication devices such as a mobile phone and a PDA (Personal Digital Assistance) that perform non-contact data communication with the IC card 2.

Further, in the above-described embodiment, when the value of C1 is variable in the equivalent circuit shown in FIG. 2, C1 in a state where impedance matching between R1 and R2 is taken is w ² = 1 / (C2 · L2 ) = 2π · 13.56 [MHz], it is given by the following equation. However, −1 <k <1.

When the distance between the reader / writer 3 and the IC card 2 is long and k = 0, C1 = 1 / (L1 · w ² ) from the equation (2), and the resonance frequency of C1 and L1 is 13.56 [MHz]. In this case, power can be transmitted efficiently. However, when the distance between the reader / writer 3 and the IC card 2 is short, the impedance matching cannot be achieved if the value of C1 is set so that the resonance frequency is 13.56 [MHz], so that the IC card 2 receives it. There is a problem that the power is reduced.

  In order to cope with this, in a state where excessive power transmission to the IC card 2 is not a problem, the signal source SG outputs as the distance between the reader / writer 3 and the IC card 2 increases based on the detected phase difference. Control for increasing the voltage of the AC signal may be performed.

  In the embodiment described above, the AC signal output from the signal source SG when the IC card 2 approaches based on the phase difference between the voltage of the AC signal output from the signal source SG and the signal flowing through the antenna 6. The power received by the approaching IC card 2 is lowered by lowering the voltage. However, the present invention is not limited to this, and the resonance frequency of the reader / writer 3 is changed when the IC card 2 approaches. By doing so, the power received by the approaching IC card 2 may be reduced.

  That is, as shown in FIG. 4 in which the same reference numerals are assigned to the corresponding parts in FIG. 3, the transmitter 7 of the reader / writer 3 determines the phase difference between the AC signal output from the signal source SG and the voltage of the signal flowing through the antenna 6, for example. The phase difference is detected by a phase difference detection unit 13 formed of an Ex-OR (Exclusive-OR) circuit, and the phase difference is further integrated by a low-pass filter 14 and supplied to the capacitance control unit 17 as a phase difference detection signal.

  When the phase difference between the AC signal output from the signal source SG and the voltage of the signal flowing through the antenna 6 exceeds a predetermined threshold based on the value of the phase difference detection signal, the capacity control unit 17 as the power control means reads the reader / writer 3. In order to prevent the power received by the IC card 2 from being excessively close to the IC card 2 and changing the capacitance of the variable capacitor C1, the resonance frequency of C1 and L1 is changed. As a result, the power received by the IC card 2 is reduced.

  The present invention can be applied to a reader / writer that performs data communication with a non-contact IC card.

It is a block diagram which shows the structure of a non-contact IC card system. It is a basic diagram which shows the equivalent circuit of an IC card and a reader / writer. It is a block diagram which shows the structure of the transmission part by this invention. It is a block diagram which shows the structure of the transmission part by other embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Non-contact IC card system, 2 ... IC card, 3 ... Reader / writer, 4 ... Signal processing part, 5 ... Control part, 6 ... Antenna, 7 ... Transmission part, 8 ... Reception part DESCRIPTION OF SYMBOLS 10 ... Control part, 11 ... Antenna, 12 ... Transmission / reception part, 13 ... Phase difference detection part, 14 ... Low pass filter, 15 ... Voltage control part

Claims (3)

A communication device that transmits power to a communication target in a contactless manner and performs data communication with the communication target in a contactless manner.
A signal source for generating an AC signal;
An antenna that radiates the AC signal supplied from the signal source and transmits power to the communication target in a contactless manner;
Phase difference detection means for detecting a phase difference between the phase of the AC signal output from the signal source and the phase of the AC signal flowing through the antenna;
A communication apparatus comprising: power control means for reducing power received by the communication target based on the phase difference detected by the phase difference detection means. The power control unit detects that the distance between the communication device and a communication target is close based on the increase in the phase difference detected by the phase difference detection unit, and outputs the AC signal output from the signal source. The communication apparatus according to claim 1, wherein power received by the communication target is reduced by lowering a voltage. The power control means detects that the distance between the communication device and the communication target is close based on the increase in the phase difference detected by the phase difference detection means, and changes the resonance frequency of the antenna. The communication apparatus according to claim 1, wherein power received by the communication target is reduced.

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