JP2004297779A - Radio communications ic and radio communication information storage medium using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication IC and radio communication information storage medium using the same in which operational stability can be secured by reducing a data receiving error from the radio communication IC for transmitting data to the side of an external device. <P>SOLUTION: A radio communication IC 1 is provided for receiving a radio wave signal of a predetermined carrier frequency from the external device side via an antenna 6 to receive power supply and for exchanging information with the external device side. The relevant radio communication IC 1 is equipped with a capacitor 5 for accumulating power, a diode D<SB>1</SB>that is provided between one terminal of the antenna 6 and the capacitor 5 for supplying a charging current of the radio wave signal to the capacitor 5 in accordance with a half cycle of the received radio wave signal, and a load modulation circuit 8. The load modulation circuit 8 is then driven by receiving power supply from the capacitor 5 in the remaining half cycle relative to the half cycle of the radio wave signal for supplying the charging current to the capacitor 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wireless communication IC and a wireless communication information storage medium, and more particularly, to an IC card reader / writer (hereinafter referred to as a reader / writer) or an IC tag for performing data communication with an information medium such as an IC card in a non-contact state. In a product confirmation management device that manages inventory management etc. of products attached, devices or systems represented by electronic commerce that use information media such as electronic keys, etc., by electromagnetic induction with external devices via coils The present invention relates to an improved technique for ensuring the stability of operation of a wireless communication IC in a wireless communication IC that receives power supply through coupling and transmits and receives data to and from an external device.

  2. Description of the Related Art Conventionally, there has been known a system that opens and closes a door using a card as a key when entering and leaving a building such as a company or an apartment or a room. Similarly, as such a system, there is a gate management system mainly based on an automatic ticket gate and the like.

  These are provided with a terminal having a reader / writer function adjacent to a door as an entrance or at a ticket gate. Then, the information such as the password and the authentication code stored in the terminal and the host computer connected to the terminal and the information such as the period of use are collated with the information such as the password and the authentication code recorded on the card. Is valid or invalid. In this way, the validity of the card user is confirmed, the unlocking means is operated or the gate is prohibited, the key is opened, the entry is permitted, or the card is passed through the ticket gate.

  In recent years, non-contact type IC cards have been put to practical use. A non-contact type IC card transmits and receives information to and from a reader / writer by electromagnetic induction or electromagnetic coupling. Conventionally, a non-contact type IC card itself has a built-in battery. However, recently, a non-contact type IC card in which IC driving power is reduced, power is supplied by radio waves, and transmission / reception is implemented. (Patent Documents 1 and 2).

  Furthermore, recently, using an electroforming technique or the like, an IC chip having a width of tens of micrometers and a coil formed on an IC chip of several mm square through an insulating layer is attached to an IC card or a product. It is used as an IC tag. This type of IC chip is one of non-contact type information media, and a wireless communication IC (or IC tag, other IC type non-contact information medium, hereinafter, including these) is referred to as a wireless communication IC in this specification and claims. Communication IC).

  Such a data transmission / reception system using a wireless communication IC includes a contact type (a distance to a non-contact type IC card or an IC tag of about 0 to 2 mm) or a close type (a distance of about 2 mm to 10 cm). The wireless communication IC in this data transfer system transmits and receives data in close or close proximity to a reader / writer (external device). Normally, data communication is performed between the wireless communication IC and the reader / writer using the ASK (Amplitude Shift Keying) or FSK (Frequency Shift Keying) modulation method. When power is supplied to the wireless communication IC, first, an unmodulated radio wave of a frequency having a constant amplitude is transmitted from the external device to the wireless communication IC for a certain period. The wireless communication IC operates with the power and responds to the reader / writer. At this time, the wireless communication IC may perform data transmission for a response to the reader / writer by using a load modulation method.

FIG. 3 shows a circuit of a wireless communication IC employing a load modulation method. In FIG. 3, reference numeral 10 denotes a wireless communication IC. The wireless communication IC 10, the logic circuit 3 having a control circuit 3a and a memory 3b, etc., the load modulation circuit 4, a diode D _1, and is a capacitor 5 as a power source is built. The wireless communication IC 10 is connected to a wireless communication IC antenna coil 6 (hereinafter, antenna coil 6). The coil ON chip 2 is formed by the wireless communication IC 10 and the antenna coil 6. The wireless communication IC 10 couples with an external device antenna coil 7 (hereinafter referred to as an antenna coil 7) provided on an external device side such as a reader / writer via an antenna coil 6 by electromagnetic induction to transmit and receive data. Do.

The load modulation circuit 4 transmits data by changing the shunt impedance of both terminals 6a and 6b of the antenna coil 6. Terminal 6a Therefore, the series circuit 4a that P channel MOS transistor Tr and a resistor R ₁ is connected in this order between the 6b are provided.

  Then, an ON / OFF signal corresponding to the transmission data, that is, a modulation signal (MOD) is applied to the gate terminal of the transistor Tr from the output terminal 3c of the logic circuit 3. The transistor Tr turns on / off according to the modulation signal (MOD). When the transistor Tr is switched from the ON state to the OFF state, the impedance decreases from the high impedance in the ON state to about several hundred Ω in the OFF state. In this way, the carrier radio signal is subjected to modulation with an amplitude change of several% to several tens%, and modulation is performed.

As a result, the modulated signal has a waveform as shown in FIG. Note that this waveform is an example in which the carrier frequency is a 13.56 MHz signal standardized as a proximity type, and the modulation frequency of the load modulation is 26.48 kbps.
JP-A-8-330840 Japanese Patent Application No. 2000-172793

In this case, the capacitor 5 for power storage, the load current of the modulated state is half-wave rectified by the inserted diode D ₁ between the terminal 6a and the capacitor 5, the voltage V _DD in the rectified current Will be charged as a power source. Here, since the modulation waveform is superimposed on the charge signal waveform as shown in FIG. 4, a ripple is added to the power supply voltage V _DD . Accordingly, the power supply voltage V _DD becomes unstable.

The external device receiving such a load modulation signal receives the load-modulated signal by electromagnetic induction, so that the amplitude of the signal fluctuates by several% to several tens% according to the modulation in the wireless communication IC 10. , Only a few percent variation in amplitude can be detected. Therefore, when the power supply voltage V _DD of the capacitor 5 becomes unstable, the external device cannot accurately receive data from the wireless communication IC 10 and a problem that a data reception error easily occurs occurs.

  SUMMARY OF THE INVENTION An object of the present invention is to solve such a problem of the related art, reduce a data reception error from a wireless communication IC to an external device, and secure operation stability of the wireless communication IC. An object of the present invention is to provide a wireless communication IC and a wireless communication information storage medium using the same.

  The wireless communication IC and the wireless communication information storage medium using the same according to the present invention are characterized in that a radio signal of a predetermined carrier frequency is received from an external device through an antenna to receive power supply, and the wireless communication IC and the external device are connected. In a wireless communication IC that transmits and receives information, a charging current for a radio signal is supplied to a capacitor according to a half cycle of a received radio signal provided between one end of an antenna and the capacitor in a capacitor for storing power. A diode and a load modulation circuit are provided, and the load modulation circuit is driven by receiving power supply from the capacitor in the remaining half cycle of the radio signal.

  In a wireless communication IC and a wireless communication information storage medium using the same according to the present invention, a driving circuit connected to one end of an antenna to which a diode for rectifying a received radio signal is connected and operated by receiving power supply from a capacitor is provided. The driving circuit is operated when a radio signal of another half cycle different from the charging operation is received via one end of the antenna.

  As a result, load modulation can be performed on the carrier radio signal in the remaining half cycle that is different from the half cycle of the capacitor charging operation. It is no longer affected by modulation. As a result, even when load modulation occurs, the voltage of the power supply capacitor is stabilized, and data reception errors from a wireless communication IC that exchanges data with an external device can be reduced.

  According to the present invention, a driving circuit is provided which is connected to one end of an antenna to which a diode for rectifying a received radio signal is connected and operates by receiving power supply from a capacitor, and operates in another half cycle different from the charging operation. The driving circuit is operated when a radio signal is received via one end of the antenna.

  As a result, load modulation can be performed on the carrier radio signal in the remaining half cycle that is different from the half cycle of the capacitor charging operation. It is no longer affected by modulation. As a result, even when load modulation occurs, the voltage of the power supply capacitor is stabilized, and data reception errors from a wireless communication IC that exchanges data with an external device can be reduced.

  Further, since load modulation is performed using a half-cycle radio signal that is different from the charging operation and is not used in the related art, it is possible to efficiently use the power supply.

  FIG. 1 is a circuit diagram of an embodiment to which the wireless communication IC of the present invention is applied, and FIG. 2 is an explanatory diagram of the power supply timing. Note that the same components as those in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.

  1, reference numeral 1 denotes a wireless communication IC, which has a load modulation circuit 8 instead of the load modulation circuit 4 of FIG.

The load modulation circuit 8, a resistor R ₁ and transistor Tr and this order between the two terminals 6a and terminal 6b of the antenna coil 6 has a series circuit 8a that are connected in series in the reverse order of the wiring and 3 further, P-channel transistor Tra and the diode D ₂ between the cathode and the terminal 6a of the diode D _1, resistors R ₂ is series-connected drive circuits 8b are provided in this order.

Drive circuit 8b is operated by the power from the capacitor 5, a connection point N of the diode D ₂ and resistor R ₂ is connected to the gate of the transistor Tr, a gate of the transistor Tra is connected to the output terminal 3c of the logic circuit 3 I have. The resistor R _2, has become a bias resistor of the transistor Tr, the transistor Tr in the terminal voltage determined by the resistor R ₂ is turned ON.

Next, power supply in the circuit of the wireless communication IC according to the present invention will be described with reference to FIGS. Here, when a signal having a sine wave waveform as a 13.56 MHz carrier radio signal is supplied to the terminals 6a and 6b from the external device side via the antenna coil 7, this signal is supplied as shown in FIG. the capacitor 5 in half-wave of the positive electrode side (positive half cycle) is charged is rectified by the diode D _1. Then, as indicated by hatching in FIG. 2 (b), in the half-wave of the negative electrode side (negative half cycle), the terminal 6a side becomes negative, since the terminal 6b side is positive, the diode D ₁ is in OFF, A circuit corresponding to the negative half cycle is formed at this time via the antenna coil 6, and the drive circuit 8b operates by receiving the voltage of the capacitor 5, and drives the transistor Tr.

As a result, as shown in FIG. 2B, the load modulation is performed on the negative half cycle side, and the positive half cycle is allocated to the charging cycle of the capacitor 5. As a result, the waveform of the positive half cycle becomes a waveform of a constant amplitude, and power supply and load modulation are separated into different positive and negative cycles. As a result, the power supply voltage V _DD of the capacitor 5 is not affected by the load modulation, and the charging and the load modulation are performed alternately in a half cycle, so that the load modulation is performed at a stable voltage and the external device side Errors in received data are reduced.

  By the way, in the present embodiment, the description mainly focuses on data transmission from the wireless communication IC 1. Such data transmission is mainly performed in an IC tag or the like, but in a non-contact type IC card or the like having a built-in wireless communication IC 1, data is transmitted after receiving a command such as a transmission request, and data is exchanged with each other. Take the form. Since data reception from the external device side of the wireless communication IC 1 in such a case is not directly related to the present invention, it is omitted in the present embodiment shown in FIG.

  As described above, in the present embodiment, the positive half cycle is assigned to the capacitor charging side, and the negative half cycle is assigned to the load modulation side. However, the reverse is also possible. In this case, the logic circuit 3 and the load modulation circuit 8 operate using the power of the capacitor 5 as a negative power supply. Accordingly, the transistor can be changed from a P-channel transistor to an N-channel transistor. Further, each of these transistors may use a bipolar transistor.

  Also in the present embodiment, if the logic at the output terminal 3c of the logic circuit 3 is set to negative logic, the operation is reversed. For example, P-channel transistors may be N-channel transistors and these may be connected downstream of the series resistor. They can be arranged, and a similar operation is possible. Therefore, the transistor of this embodiment is not limited to the P-channel.

  The present invention is not limited to the communication distance, and can be applied to a circuit that transmits data from the wireless communication IC 1 to the external device side in a close contact type or a close proximity type.

  Furthermore, the carrier frequency of the present embodiment is an example, and for example, 4.91 MHz, which is a close-contact standardized frequency, may be employed.

  Note that the wireless communication IC 1 of the present invention can be built in a medium such as an electronic key in a security system in addition to a non-contact type IC card or IC tag, and the antenna coil of the wireless communication IC 1 is stacked on a chip. However, the shape is not limited to a coil-on-chip type or a type in which an external antenna is connected to a terminal of the wireless communication IC 1.

FIG. 1 is a circuit diagram of an embodiment to which a wireless communication IC according to the present invention is applied. FIG. 4 is an explanatory diagram of power supply timing in the wireless communication IC of the present invention. FIG. 2 is an explanatory diagram of a conventional circuit of a load modulation type wireless communication IC. FIG. 3 is an explanatory diagram of a modulation waveform of a load modulation method of a contact type wireless communication IC.

Explanation of reference numerals

1, 10: Wireless communication IC, 2: Coil ON chip IC,
3 ... logic circuit, 3a ... control circuit, 3b ... memory,
3c: output terminal, 4, 8: load modulation circuit,
5: condenser, 6: antenna coil for wireless communication IC,
7: antenna coil for external device, 6a, 6b: terminal,
8a: series circuit, 8b: drive circuit,
Tr, Tra ... P-channel MOS transistor,
Resistors R ₁ , R ₂ ... resistors, D ₁ , D ₂ ... diodes.

Claims (5)

In a wireless communication IC that receives a radio signal of a predetermined carrier frequency from an external device via an antenna and receives power supply, and transmits and receives information to and from the external device,
A capacitor for storing power,
A diode provided between one end of the antenna and the capacitor, for supplying a charging current of the radio signal to the capacitor in accordance with a half cycle of the received radio signal,
A load modulation circuit,
A wireless communication IC wherein the load modulation circuit is driven by receiving power supply from the capacitor in the remaining half cycle of the radio signal. In a wireless communication IC that receives a radio signal of a predetermined carrier frequency from an external device via an antenna and receives power supply, and transmits and receives information to and from the external device,
A capacitor for storing power,
A diode that is provided between one end of the antenna and the capacitor and supplies a charging current of the radio signal to the capacitor according to a half cycle of the received radio signal;
A load modulation circuit,
A series circuit of a first transistor and a first resistor, wherein the load modulation circuit is provided in parallel with the antenna; and a capacitor connected to one end of the antenna for a half cycle of the radio signal and the other half cycle And a driving circuit for turning on / off the first transistor by receiving power supply from the wireless communication IC.   In order to modulate the carrier signal by several percent to several tens percent, a resistance value of the first resistor and an ON resistance of the first transistor are selected, and the radio signal is received in close contact with the external device. Item 3. The wireless communication IC according to Item 2.   The first transistor is a P-channel transistor, the first resistance is several hundred Ω, and the driving circuit is a P-channel transistor connected between a cathode side of the diode and one end of the antenna. A series circuit including a second transistor including a transistor, a second diode, and a second resistor, wherein a connection point between the second diode and the second resistor is connected to a gate of the first transistor. The wireless communication IC according to claim 3, wherein: In a wireless communication information storage medium that receives a radio signal of a predetermined carrier frequency from an external device, receives power supply, and exchanges information with the external device,
An antenna for receiving a radio signal of a predetermined carrier frequency from the external device;
A capacitor for storing power,
A diode provided between one end of the antenna and a capacitor, for supplying a charging current of the radio signal to the capacitor according to a half cycle of the received radio signal;
A load modulation circuit,
A wireless communication information storage medium, wherein the load modulation circuit is driven by receiving power supply from the capacitor in the remaining half cycle of the half cycle of the radio signal.

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