JP4797991B2 - COMMUNICATION DEVICE, NON-CONTACT IC CARD WITH THE SAME, AND INFORMATION DEVICE - Google Patents

Description

  The present invention relates to a communication device that can be mounted on a non-contact type IC card, a non-contact type IC card on which the communication device is mounted, and an information device such as a mobile phone.

  The development and development of contactless IC cards are remarkable, and IC card functions and the like have been incorporated into portable devices from the card size. Non-contact type IC cards are disclosed in Patent Documents 1 and 2, for example.

  FIG. 1 is a diagram showing a configuration of a front end circuit 10 of a general non-contact type IC card R / W (reader / writer) device.

As shown in FIG. 1, the main part of the front-end circuit 10 of the non-contact type IC card R / W device includes a reception system circuit 11, a transmission system circuit 12, a series resonance capacitor 13, an R / W antenna 14, and the like. It consists of The resistor 15 is an internal resistance of the (antenna) coil 16.
In FIG. 1, C1 indicates the capacitance of the capacitor 13, R1 indicates the resistance value of the resistor 15, and L1 indicates the inductance of the coil 16.

The operation of the front end circuit 10 of the R / W device of FIG. 1 will be described.
At the time of data transmission, a modulated wave signal is output from the transmission system circuit 12, a current flows through the capacitor 13 connected in series with the antenna 14 and the coil 16 forming the antenna 14, and a magnetic field is radiated from the antenna 14.
On the other hand, a fixed carrier signal is output from the transmission system circuit 12 at the time of reception, but by performing load modulation on the card side, the carrier signal received by the reception system circuit 11 receives the signal subjected to load modulation. And demodulated data can be extracted.
In transmission / reception of data, a resonance circuit is formed by the capacitor 13 and the coil 16. At this time, the impedance viewed from the transmission system circuit 12 becomes small (a large amount of current flows), and the transmission magnetic field from the antenna 14 becomes the largest.
That is, the front-end circuit 10 at the time of transmission / reception has a circuit configuration in which the coil 16 and the capacitor 13 are connected in series. Further, it is basically ideal that the carrier frequency of the signal to be used is set to coincide with the resonance frequency of the coil 16 and the capacitor 13 and that the impedance is the lowest at the resonance frequency.

The coil 16 constituting the loop antenna is represented by a resistor 15 including the loss, and forms a series resonance circuit with the capacitor 13.
The resonance frequency f0 is expressed as follows.

[Equation 1]
f0 = 1 / (2π * √ (L1 * C1)) (1)

  The impedance Z of the antenna circuit at this time is as follows. When the resistance value R1 of the resistor 15 is small, a current can be efficiently passed through the antenna, and the generated magnetic field is maximized.

[Equation 2]
Z = R1 + jωL1 + 1 / (jωC1)
= R1 (2)

Next, a front end circuit used for a non-contact type IC card will be described.
FIG. 2 is a diagram showing a configuration of a main part of a front end circuit used for a non-contact type IC card.

As shown in FIG. 2, the main part of the front-end circuit 20 used in the non-contact type IC card includes a transmission / reception system circuit 21, a capacitor 22, a card antenna 23, a resistor 24, and the like.
In FIG. 2, C2 represents the capacitance of the capacitor 22, R2 represents the resistance value of the resistor 24, and L2 represents the inductance of the coil 25.

In the circuit of FIG. 2, as a card function, a resistor 24 and a coil 25 are connected in series, and a capacitor 22 is connected in parallel at both ends, and is set to resonate at a frequency to be used.
It is basically ideal that the impedance of the combined circuit of the capacitor 22 connected in parallel with the card antenna 23 is the highest during resonance.
The parallel resonance frequency f0 is expressed by the following equation.

[Equation 3]
f0 = 1 / (2π * √ (L2 * C2)) (3)

The impedance Z of the antenna circuit at this time is expressed by the following equation.

[Equation 4]
Z = 1 / (1 / (R2 + jωL2) + (jωC2)) (4)

  And the impedance Z represented by the case where R2 is small (Formula 4) is as follows, and the received voltage becomes maximum at the peak of the impedance.

[Equation 5]
Z ≒ ∞
JP 2002-334310 A JP 2004-355212 A

As described above, the optimal number of circuit configurations for the R / W (reader / writer) device and the optimal circuit configuration for the card are different, so each is suitable for satisfying both functions with a single front-end circuit. It is necessary to prepare the antenna and front end circuit separately.
This has a high degree of design difficulty because there are many front-end parts and circuits, and there are interferences due to multiple antennas, and countermeasures are required. Further, when one antenna is used, the characteristics are biased to either the R / W function or the card function, and it is difficult to satisfy both characteristics.
In recent years, not only a card function but also an R / W function has been required, but satisfying both functions at the same time has problems in characteristics, cost, etc., and is not easy.

  The present invention provides a communication device that can share one antenna and that can sufficiently exhibit the characteristics of the function and card function as a reader / writer, a non-contact type IC card having the same, and an information device There is to do.

  A communication apparatus according to a first aspect of the present invention includes a first transmission circuit having first and second output terminals and outputting a carrier from the first and second output terminals in a first mode, and a node And an inductor having one end connected to the node and the other end connected to the second output terminal of the first transmission circuit, and between the node and the first output terminal of the first transmission circuit. An antenna circuit including at least one capacitor connected to the second circuit, a second transmission circuit connected to the node of the antenna circuit and outputting transmission data in the second mode, and the node of the antenna circuit At least one receiving circuit connected to receive data received by the antenna circuit, and in the first mode, the antenna circuit is a series resonant circuit including the inductor and a capacitor. Formed, above the second mode, having a circuit switching portion which forms a parallel resonant circuit including the inductor and the capacitor of the antenna circuit.

  The non-contact type IC card according to the second aspect of the present invention has first and second output terminals, and outputs first carrier data from the first and second output terminals in the reader / writer mode. A circuit; a node; an inductor having one end connected to the node; the other end connected to a second output terminal of the first transmission circuit; and a first output of the node and the first transmission circuit. An antenna circuit including at least one capacitor connected to the terminal; a second transmission circuit connected to the node of the antenna circuit and load-modulating transmission data in card mode; and the antenna circuit At least one receiving circuit connected to the node and performing reception processing on data received by the antenna circuit, and in the reader / writer mode according to a mode control signal, The antenna circuit is formed as a series resonant circuit including the inductor and capacitor, and in the card mode, the antenna circuit is formed as a parallel resonant circuit including the inductor and capacitor, a memory switching unit, and the transmission data are selected. And a control unit that supplies the first transmission circuit or the second transmission circuit, performs predetermined processing on the reception data of the reception circuit, and controls access to the memory.

  A third aspect of the present invention is an information device having a communication function with a communication network, and includes a communication device having a reader / writer function and a card function, and the communication device includes first and second output terminals. A first transmission circuit for outputting a carrier from the first and second output terminals in the first mode, a node, one end of which is connected to the node, and the other end of the first transmission circuit. An antenna circuit including an inductor connected to a second output terminal; and at least one capacitor connected between the node and the first output terminal of the first transmission circuit; and A second transmission circuit connected to the node and outputting transmission data in the second mode; and at least one for receiving data received by the antenna circuit connected to the node of the antenna circuit. In the first mode, the antenna circuit is formed as a series resonant circuit including the inductor and a capacitor, and in the second mode, the antenna circuit is formed as a parallel resonant circuit including the inductor and the capacitor. A switching unit.

  According to the present invention, it is not necessary to separate the antenna for the reader / writer (R / W) and the card, and only one antenna is sufficient. As a result, problems due to interference between the R / W antenna and the card antenna are eliminated. Since the number of antennas is reduced, the number of peripheral parts and circuits is reduced, the design is facilitated, and costs can be reduced. Furthermore, a high-performance front-end circuit can be obtained with a simple configuration at low parts cost and design cost.

FIG. 1 is a diagram showing a configuration of a front end circuit of a general non-contact type IC card R / W (reader / writer) device. FIG. 2 is a diagram showing a configuration of a main part of a front end circuit used for a non-contact type IC card. FIG. 3 is a diagram illustrating a configuration example of a communication system to which a mobile phone as a portable information device according to an embodiment of the present invention is applied. FIG. 4 is a block diagram illustrating a basic configuration example of the mobile phone according to the present embodiment. FIG. 5 is a diagram showing a first configuration example of a communication device incorporating a non-contact type IC card function and a reader / writer function mounted on a mobile phone according to an embodiment of the present invention. FIG. 6 is a diagram showing a second configuration example of a communication device incorporating a non-contact type IC card function and a reader / writer function mounted on the mobile phone according to the embodiment of the present invention. It is a figure which shows a structure. FIG. 7 is a diagram showing a second configuration example of a communication device with a built-in non-contact type IC card function and a reader / writer function mounted on the mobile phone according to the embodiment of the present invention. FIG. FIG. 8 is a diagram showing a third configuration example of a communication device incorporating a non-contact type IC card function and a reader / writer function mounted on the mobile phone according to the embodiment of the present invention. FIG. 9 is a diagram showing a fourth configuration example of a communication device incorporating a non-contact type IC card function and a reader / writer function mounted on a mobile phone according to an embodiment of the present invention. FIG. 10 is a diagram illustrating a simulation result of the communication apparatus illustrated in FIG. FIG. 11 is a diagram illustrating a simulation result of the communication device illustrated in FIG. 9. FIG. 12 is a diagram showing a fifth configuration example of a communication device incorporating a non-contact type IC card function and a reader / writer function mounted on a mobile phone according to an embodiment of the present invention. FIG. 13 is a diagram illustrating a sixth configuration example of a communication device that incorporates a non-contact type IC card function and a reader / writer function that are mounted on a mobile phone according to an embodiment of the present invention. FIG. 14 is a diagram showing a seventh configuration example of a communication apparatus incorporating a non-contact type IC card function and a reader / writer function mounted on a mobile phone according to an embodiment of the present invention. FIG. 15 is a diagram illustrating a configuration example of a non-contact type IC card on which the communication device of FIG. 5 is mounted. FIG. 16 is a diagram illustrating a configuration example of a non-contact type IC card on which the communication device of FIGS. 6 and 7 is mounted. FIG. 17 is a diagram illustrating a configuration example of a non-contact type IC card on which the communication device of FIG. 8 is mounted. 18 is a diagram illustrating a configuration example of a non-contact type IC card on which the communication device of FIG. 9 is mounted. FIG. 19 is a diagram illustrating a configuration example of a non-contact type IC card on which the communication device of FIG. 12 is mounted. FIG. 20 is a diagram illustrating a configuration example of a non-contact type IC card on which the communication device of FIG. 13 is mounted. FIG. 21 is a diagram illustrating a configuration example of a non-contact type IC card on which the communication device of FIG. 14 is mounted.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Communication system, 110 ... Mobile phone, 115 ... Memory part, 116 ... Communication apparatus, 117 ... Control part, 120 ... Non-contact type IC card, 130 ... Base Station, 140 ... Communication network, 150 ... Server, 200, 200A to 200F ... Communication device, 210, 210A-210F ... Antenna circuit, 211 ... Antenna coil, 212, 212-1, 212-2, 213 ... capacitor, 214 ... switch, 215 ... high resistance, ND210, ND211 ... node, A, B ... terminal, 220, 220A ... transmission system circuit (first) 1 transmission circuit), 221, 221 A, first output terminal, 222, 222 A, second output terminal, 223, first transmission buffer, 224, second transmission buffer, 25 ... switch, 226 ... inverter, 227 ... input terminal, 230 ... reply circuit (second transmission circuit), 240 ... reception system circuit, 250 ... switch, 260 ... Carrier generator, 270 ... switch, 280, 280A, 280B ... circuit switching unit, 300, 300A to 300F ... non-contact IC card, 310 ... CPU (control unit), 320 ... ·memory.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 3 is a diagram illustrating a configuration example of a communication system to which a mobile phone as a portable information device according to an embodiment of the present invention is applied.

  A communication system 100 shown in FIG. 3 includes a mobile phone 110, an external non-contact type IC card 120, a base station 130, a communication network 140, and a server 150.

The cellular phone 110 according to the present embodiment incorporates, for example, a non-contact IC card function and a reader / writer function, and the installed reader / writer (R / W) function is a response from an external non-contact IC card 120. When (signal) is received, wireless communication is performed with the non-contact type IC card 120 to establish a connection.
When the connection with the non-contact type IC card 120 is established, the mobile phone 110 is connected to the server 150 from the base station 130 via the communication network 140 by wireless communication according to a predetermined communication method. The communication between 120 and the server 150 is relayed.
If the mutual authentication is successful, the reader / writer function installed in the mobile phone 110 reads the information stored in the non-contact type IC card 120 in accordance with an instruction from the server 150, or the non-contact type IC card 120. A process for writing new information in

  FIG. 4 is a block diagram illustrating a basic configuration example of the mobile phone according to the present embodiment.

  As shown in FIG. 4, the mobile phone 110 includes a wireless communication unit 111 that performs wireless communication processing with the server 150 via a communication network 140, a display unit 112 including a liquid crystal display device (LCD), a numeric keypad, and the like. An operation unit 113 including operation keys, a voice processing unit 114 having a microphone and a speaker for voice input processing or voice output processing, a memory unit 115 for storing programs, message data, address data, IC card data, etc. To realize the overall function control of the communication device 116 forming the front-end circuit unit for realizing the contact IC card function and the reader / writer function, and the mobile phone 110, and the non-contact IC card function and the reader / writer function. Mode control, predetermined processing for transmission data TD, reception data RD and corresponding A control unit (CPU) 117 for accessing the memory unit 115.

The wireless communication unit 111, the display unit 112, the operation unit 113, the voice processing unit 114, the memory unit 115, and the control unit 117 constitute a telephone unit as a normal mobile phone.
The communication device 116, the memory unit 115, and the control unit 117 constitute a card function unit that implements a non-contact type IC card function and a reader / writer function.
In addition, it is possible to configure the mode designation, switching, and the like under the control of the control unit 117 in accordance with the operation of the operation unit 114.
At this time, the control unit 117 outputs a mode control signal MD (Mode) and transmission data TD to the communication device 116, receives the reception data RD, and performs storage processing in the memory unit 115. The memory unit 115 includes a nonvolatile memory such as a flash memory.
The control unit 117 may be configured to be provided separately for the telephone unit, the card, and the card function unit.
In the following description, the reader / writer mode corresponds to the first mode, and the card mode corresponds to the second mode.

FIG. 5 is a diagram showing a configuration example of a communication device incorporating a non-contact type IC card function and a reader / writer function mounted on the mobile phone according to the embodiment of the present invention.
In FIG. 5, the communication device 116 of FIG.

  5 includes an antenna circuit 210, a transmission system circuit 220 mainly serving as a first transmission circuit for a reader / writer function, a reply (card) circuit 230 serving as a second transmission circuit for a card function, and a reception system. The circuit 240 includes a switch (SW10) 250, a carrier generator 260 that generates a carrier having a frequency of 13.56 MHz, and a switch 270.

The antenna circuit 210 includes a node ND210, an antenna coil (inductor) 211, and a capacitor 212. In FIG. 5, Ca indicates the capacitance of the capacitor 212, and L <b> 11 indicates the inductance of the coil 211.
One end of the antenna coil 211 is connected to the node ND210, the first electrode (one end) of the capacitor 212 is connected to the node ND210, and the second electrode (the other end) is connected to the first output terminal 221 of the transmission system circuit 220. ing. The other end of the antenna coil 211 is connected to the second output terminal 222 of the transmission system circuit 220.

  The transmission system circuit 220 includes a first output terminal 221, a second output terminal 222, a first transmission buffer 223, a second transmission buffer 224, a switch (SW11) 225, an inverter (INV) 226, and an input terminal 227. Have

The first transmission buffer 223 includes a CMOS buffer including a p-channel MOS (PMOS) transistor PT221 and an n-channel MOS (NMOS) transistor NT221.
The source of the PMOS transistor PT221 is connected to the power supply potential Vdd, the drain is connected to the drain of the NMOS transistor NT221, and the source of the NMOS transistor NT221 is connected to the reference potential (ground potential) GND.
The gates of the PMOS transistor PT221 and the NMOS transistor NT221 are connected to each other, the input node ND221 is formed by the connection point, and the output node ND222 is formed by the connection point between the drains of the PMOS transistor PT221 and the NMOS transistor NT221. The node ND222 is connected to the first output terminal 221.

The second transmission buffer 224 is configured by a CMOS buffer including a PMOS transistor PT222 and an NMOS transistor NT222.
The source of the PMOS transistor PT222 is connected to the power supply potential Vdd, the drain is connected to the drain of the NMOS transistor NT222, and the source of the NMOS transistor NT222 is connected to the reference potential (ground potential) GND.
The gates of the PMOS transistor PT222 and the NMOS transistor NT222 are connected to each other, the input node ND223 is formed by the connection point, and the output node ND224 is formed from the connection point between the drains of the PMOS transistor PT222 and the NMOS transistor NT222. Node ND 224 is connected to second output terminal 222.

The switch 225 has a fixed contact a connected to the input node ND221 of the transmission buffer 223, an operation contact b connected to the output terminal of the inverter 226, and an operation contact c connected to the input terminal 227 of the transmission system circuit 220.
The switch 225 is switched between a card mode and a reader / writer (R / W) mode by a mode control signal MD (Mode) from a control unit (CPU or the like) 117.
The fixed contact a and the operating contact c are connected in the card mode, and the fixed contact a and the operating contact b are connected in the reader / writer mode.

  An input terminal of the inverter 226, an input node ND223 of the second transmission buffer 224, and an operation contact c of the switch 225 are connected to the input terminal 227.

The input terminal 227 is connected to the fixed contact a of the switch 270.
Specifically, in the switch 270, the fixed contact a is connected to the input terminal 227 of the transmission system circuit 220, the operation contact b is connected to the output terminal of the carrier generator 260, and the operation contact c is connected to the power supply potential Vdd. ing.
The switch 270 is switched between a card mode and a reader / writer (R / W) mode by a mode control signal MD (Mode) from a control unit (CPU or the like) 117.
The fixed contact a and the operating contact c are connected in the card mode, and the fixed contact a and the operating contact b are connected in the reader / writer mode.

In the transmission system circuit 220 having such a configuration, in the card mode, the input terminal 227 is connected to the power supply potential Vdd via the switch 270 and is fixed at the high (Hi) level. The NMOS transistors NT221 and NT222 of the second transmission buffers 223 and 224 are held in the on state, and the PMOS transistors PT221 and PT222 are held in the off state.
As a result, the first and second output terminals 221 and 222 of the transmission system circuit 220 connected to the antenna circuit 210 are connected to the ground potential.
Therefore, the antenna circuit 210 equivalently forms a parallel resonant circuit.

In the reader / writer mode, the carrier having a frequency of 13.56 MHz generated by the carrier generator 260 is supplied at the Hi level or the Low (Lo) level via the switch 270 and the input terminal 227.
When the carrier is at the Hi level, the PMOS transistor PT221 is held in the on state and the NMOS transistor NT221 is held in the off state in the first transmission buffer 223 by the carrier via the inverter 226. In the second transmission buffer 224, the PMOS transistor PT222 is held in the off state, and the NMOS transistor NT222 is held in the on state.
As a result, the first output terminal 221 is connected to the power supply potential Vdd, and the second output terminal 222 is connected to the ground potential GND. Therefore, the antenna circuit 210 forms a series resonance circuit.
When the carrier is at the Lo level, the PMOS transistor PT221 is held in the OFF state and the NMOS transistor NT221 is held in the ON state in the first transmission buffer 223 by the carrier via the inverter 226. In the second transmission buffer 224, the PMOS transistor PT222 is held in the on state, and the NMOS transistor NT222 is held in the off state.
As a result, the first output terminal 221 is connected to the ground potential GND, and the second output terminal 222 is connected to the power supply potential Vdd. Therefore, the antenna circuit 210 forms a series resonance circuit.

  In this case, the carriers by the transmission buffers 223 and 224 of the transmission system circuit 220 are transferred from the control unit 117 and ASK-modulated by the transmission data TD supplied via the switch 250, and the first and second output terminals 221. , 223 to the antenna circuit 210.

  As described above, in the communication apparatus 200 of FIG. 5, the first and second transmission buffers 223 and 224 of the transmission system circuit 220 form a resonance circuit of the antenna circuit 210 as a parallel resonance circuit or a series resonance circuit. It has 280 functions.

5 is configured to ground the capacitor 212 of the antenna circuit 210 using the NMOS switches NT221 and NT222 of the transmission buffers 223 and 224 used in the reader / writer mode.
That is, since the terminals A and B in the figure of the antenna circuit 210 are connected to the transmission buffers 223 and 224 of the transmission system circuit 220 inside the LSI, the transmission buffers 223 and 224 are turned on (ON) in the reader / writer mode. If the resistance is ignored, the transmission buffers 223 and 224 alternately output 0 V and the power supply voltage Vdd of the IC to the antenna circuit 210.
Further, as described above, in the card mode, the NMOS transistors NT221 and NT222 are turned on to be grounded to the ground potential GND.
Therefore, in both the reader / writer (R / W) mode and the card mode, the terminal voltage of the IC always falls within the range of 0 to Vdd, which has a great feature that the switch can be built in a low withstand voltage process. .

  In the card mode, the reply circuit 230 performs load modulation on the reply data read from the memory unit 115 in the control unit 117 and applies it to the node ND210 of the antenna circuit 210.

The reception system circuit 240 is also used as a reception circuit when the card function is used (card mode) and a reception circuit when the reader / writer function is used (reader / writer mode).
The reception system circuit 240 demodulates information received during the card function and the reader / writer function, and outputs received data RD to the control unit 117.

In the switch 250, the fixed contact a is connected to the transmission data TD supply line of the control unit 117 such as a CPU, the operation contact c is connected to the input of the reply (card) circuit 230, and the operation contact b is connected to the transmission system circuit 220. The input terminal 227 is connected.
The switch 250 is switched between a card mode and a reader / writer (R / W) mode by a mode control signal MD (Mode) from the control unit 117.
In the card mode using the card function, the switch 250 is switched from the fixed contact a to the connection of the one operation contact c by the mode control signal MD, and the transmission data (reply data) TD is sent to the reply (card) circuit 230. The input signal is subjected to load modulation by the reply (card) circuit 230 and applied to the antenna circuit 210.
On the other hand, in the reader / writer mode using the reader / writer function, the switch 250 switches the fixed contact a to connection with the other operation contact b by the mode control signal MD, and the transmission data TD is supplied to the transmission system circuit 220. The
Transmission data (TinA) is transmitted from the antenna circuit 210 via the transmission system circuit 220.

As described above, in this embodiment, the antenna coil 211 and the capacitor 212 forming the antenna circuit 210 are used in both the card mode and the reader / writer mode.
In general, the resonant circuit dedicated to the card function and the resonant circuit dedicated to the reader / writer function are configured by two. In this embodiment, the antenna coil 211 and the capacitor are switched by switching the resonant circuit by the circuit switching unit 280. In 212, a parallel resonance circuit for the card function and a series resonance circuit for the reader / writer function are realized.

FIG. 5 shows a case where the transmission buffer of the transmission system circuit 220 is used when operating as a reader / writer (R / W) device, and is an example in which two transmission buffers (Buff) are controlled in phase. In this case, the parallel resonance circuit is realized by turning on the NMOS side of the CMOS buffer.
Hereinafter, the operation of the communication apparatus 200 will be described focusing on the operation of the transmission system circuit 220.

In the card mode, the fixed contact a of the switch 225 of the transmission system circuit 220 is connected to the operation contact c by the mode control signal MD. At this time, the switch 250 of the communication device 200 is connected to the fixed contact a and the operation contact c by the mode control signal MD.
At this time, the input terminal 227 of the transmission system circuit 220 is connected to the power supply potential Vdd via the switch 270. That is, the input terminal 227 is fixed to the Hi (high) level, and this Hi level signal is supplied from the terminal c of the switch 225 to the gate of the NMOS transistor NT211 of the first transmission buffer 223 via the terminal a. The NMOS transistor NT221 is turned on. At this time, since the gate potential of the PMOS transistor PT221 constituting the CMOS buffer is high, the PMOS transistor PT221 is turned off.
On the other hand, the Hi level signal is supplied to the gate of the NMOS transistor NT222 of the second transmission buffer 224, and is turned on. Since the gate of the PMOS transistor PT222 constituting the CMOS inverter is at a high level, it is turned off.
As a result, since the NMOS transistor NT221 of the transmission buffer 223 is ON, the second electrode side terminal A of the capacitor 212 is equivalently grounded although there is an ON resistance.
Further, since the NMOS transistor NT222 of the transmission buffer 224 is also turned on at the other terminal of the antenna coil 211, an ON resistance exists but is grounded equivalently.
Therefore, the second electrode side terminal A of the capacitor 212 and the terminal B on the other side of the antenna coil 211 are connected in an alternating manner, and as a result, a parallel resonance circuit is formed.

When a parallel resonance circuit is formed by the capacitor 212 and the antenna coil 211, an external signal is extracted by the resonance circuit and supplied to the reception system circuit 240. On the other hand, the carrier on which the signal (load-modulated signal) processed by the reply (card) circuit 230 is superimposed resonates in the above-described parallel resonance circuit and is transmitted to the outside through the antenna coil 211 of the antenna circuit 210. .
As described above, in the card mode, the terminals A and B of the antenna circuit 210 are grounded by the NMOS transistors NT221 and NT222 of the transmission buffers 223 and 224 of the transmission system circuit 220 to form a parallel resonance circuit. Radio waves are received with high impedance.

  Next, the operation in the reader / writer (R / W) mode will be described.

In the reader / writer mode, the fixed contact a of the switch 225 of the transmission system circuit 220 is connected to the operation contact b by the mode control signal MD. At this time, the switch 250 of the communication device 200 is connected to the fixed contact a and the operation contact b by the mode control signal MD. As a result, transmission data TD is supplied to the transmission system circuit 220 to perform ASK modulation transferred from the control unit 117.
The switch 270 is connected to the fixed contact a and the operating contact b by the mode control signal MD. Therefore, the carrier generated by the carrier generator 260 is input to the input terminal 227 of the transmission system circuit 220.

Assume that a Hi (high) level carrier is supplied to the input terminal 227 of the transmission system circuit 220. This Hi level carrier is input to the inverter 226, the output thereof becomes Lo (low) level, and is supplied to the gate of the PMOS transistor PT221 of the transmission buffer 223, and the PMOS transistor PT221 is turned on. On the other hand, since the gate of the NMOS transistor NT221 of the transmission buffer 223 is at the Lo level, it is turned off.
Further, since the gate of the NMOS transistor NT222 of the transmission buffer 224 is at the Hi level, the NMOS transistor NT222 is turned on and the PMOS transistor PT222 is turned off.
As a result, the capacitor 212 and the antenna coil 211 constituting the series resonance circuit from the power source via the source and drain of the PMOS transistor PT221 of the transmission buffer 223, and the drain and source of the NMOS transistor NT222 of the transmission buffer 224, GND and the high frequency Current flows. At this time, a radio wave induced by a Hi-level high-frequency current (signal) flowing through the antenna coil 211 is radiated, and an ASK-modulated signal is transmitted to an external non-contact IC card or the like.

Next, it is assumed that a Lo (low) level carrier is supplied to the input terminal 227. The Lo level carrier is input to the inverter 226, the output thereof becomes Hi (high) level, and when it is supplied to the gate of the PMOS transistor PT221 of the transmission buffer 223, the PMOS transistor PT221 is turned off. On the other hand, the gate of the NMOS transistor NT221 of the transmission buffer 223 is in the ON state because it is at the Hi level.
Further, since the gate of the NMOS transistor NT222 of the transmission buffer 224 is at the Lo level, the NMOS transistor NT222 is turned off and the PMOS transistor PT222 is turned on.
As a result, a high-frequency current flows from the power source via the source-drain of the PMOS transistor PT222 of the transmission buffer 224 to the antenna coil 211, the capacitor 212, and further to the drain-source, GND of the NMOS transistor NT221 of the transmission buffer 223. At this time, the radio wave induced by the Lo level high-frequency current (signal) flowing through the antenna coil 211 is radiated, and the ASK-modulated signal is transmitted to an external non-contact type IC card or the like.

In the reception operation, the capacitor 212 and the antenna coil 211 are connected in series to the output terminals 221 and 222 of the transmission system circuit 220, and a signal is extracted by causing the radio wave to resonate in series with the capacitor 212 and the antenna coil 21. 240.
Thus, in the reader / writer (R / W) mode, the MOS transistors of the CMOS inverter circuit forming the transmission buffers 223 and 224 are switched by the carrier, and the configuration of the resonance circuit is set to a series resonance circuit.

  6 and 7 are diagrams showing a second configuration example of a communication device incorporating a non-contact type IC card function and a reader / writer function mounted on the mobile phone according to the embodiment of the present invention. Shows the configuration in the reader / writer mode, and FIG. 7 shows the configuration in the card mode.

6 and 7 basically differs from communication apparatus 200 in FIG. 5 in that circuit switching unit 280A is provided with switch 281 between terminals A and B of antenna circuit 210A, and the switch is mode-controlled. The configuration is such that the signal MD is turned ON and OFF.
In addition, the transmission system circuit 220A has output terminals 221A and 222A of normal phase and reverse phase.
Also in this case, the IC terminal voltage always falls within the range of 0 to Vdd in both the reader / writer (R / W) mode and the card mode, and the switch can be built in a low withstand voltage process. have.

In the reader / writer (R / W) mode, the switch 250 and 270 are connected to the fixed contact a and the fixed contact b by the mode control signal MD to input transmission data and a carrier to the transmission system circuit 220A, and The switch 281 of the circuit switching unit 280A is set to OFF so that the antenna circuit 210A becomes a series resonance circuit.
By using the antenna circuit 210A as a series resonance circuit, the impedance becomes zero at the frequency of the carrier used for transmission and reception, for example, 13.56 MHz, the current flowing through the antenna coil 211 is maximized, and the reception and transmission distance is extended. Read / write efficiency is improved.

  Examples of the above-described switch 281 for switching the resonance circuit include a transistor such as a MOSFET, a MEMS (Micro Electro Mechanical Systems), a mechanical switch, and the like.

When receiving an external card (read mode), for example, a load modulation signal from an external non-contact card is induced in the antenna coil 211, and the induced signal is supplied to the reception system circuit 240 to perform data demodulation and data Saving is performed.
On the other hand, at the time of transmission (write mode), the carrier is modulated with recording data in the modulation circuit, and the modulated carrier is supplied to the capacitor 212 of the antenna circuit 210 and the series resonant circuit of the antenna coil 211 via the transmission system circuit 220A. Is done. Then, the carrier is radiated through the antenna coil 211 and output to an external non-contact type IC card or the like.
At this time, the capacitor 212 and the antenna coil 211 constituting the antenna circuit 210 are in a series resonance state at the use frequency, and the impedance thereof is zero, and the current flowing through the antenna coil 211 becomes maximum. As a result, transmission efficiency increases and the reach of radio waves increases.

In the card mode, the output terminals 221A and 222A of the transmission system circuit 220A of the normal phase and the reverse phase are set to HiZ (high impedance) and set so as not to affect the antenna circuit 210A. Note that the output terminals 221A and 222A of the transmission system circuit 220A can be configured to be set to the same phase of LoZ (low impedance).
That is, in the card mode, a mode control signal MD is supplied from the control unit 117, the switch 281 of the circuit switching unit 280A is turned ON, and the output terminals 221A and 222A of the normal phase and the reverse phase of the output of the transmission system circuit 220A Is shorted.
As a result, in the antenna circuit 210A, the capacitor 212 and the antenna coil 212 constitute a parallel resonance circuit. In parallel with this, the switch 250 is switched to the connection between the fixed terminal a and the operation contact c, and transmission data (reply data) TD is supplied to the reply (card) circuit 220.

In such a configuration, for example, a signal transmitted from an external reader / writer device resonates in the parallel resonance circuit of the antenna coil 211 and the capacitor 212, and the extracted signal is input to the reception system circuit 240. At this time, since the output terminals 221A and 222A of the transmission system circuit 220A are short-circuited, no signal is output from the transmission system circuit 220A or the operation of the transmission system circuit 220A is stopped.
In the reception system circuit 240, the transmission signal (information) of the reader / writer device is extracted from the received magnetic field by the demodulation circuit, decoded and output to the control unit 117 such as a CPU.
In the control unit 117, the decoded data is processed, data is stored in or read from the memory unit 115, or data read from the memory unit 115 is encoded.
The transmission data is subjected to load modulation by the reply circuit 230 on the carrier signal from the reader / writer device.

  Thus, in this example, when used as a card, as shown in FIG. 7, the switch 281 of the circuit switching unit 280A is turned ON, and the antenna coil 211 and the capacitor 212 are connected in parallel, and at the same time. The front end is made to have a relatively high impedance so that the card function can be satisfied even at a longer distance.

  The reception system circuit 240 can be configured separately from a reception system circuit dedicated to the card mode and a dedicated reception system circuit in the reader / writer mode.

  FIG. 8 is a diagram showing a third configuration example of a communication device incorporating a non-contact type IC card function and a reader / writer function mounted on the mobile phone according to the embodiment of the present invention.

  The communication device 200B of FIG. 8 is different from the communication device 200A of FIGS. 6 and 7 in that the circuit switching unit 280B is replaced with a terminal A and a terminal instead of arranging the switch 281 between the terminal A and the terminal B of the antenna circuit 210B. Switches 282 and 283 are provided for selectively connecting each of B to the ground potential by the mode control signal MD.

In such a configuration, in the reader / writer mode, each circuit operates with the switches 282 and 283 of the circuit switching unit 280B set to OFF (open) by the mode control signal MD. At this time, a series resonant circuit is formed in the antenna circuit 210B.
At the time of transmission, transmission data and a carrier are input to the transmission system circuit 220A. The carrier is ASK-modulated with transmission data by the transmission system circuit 220A (modulation circuit), and this modulated signal carrier undergoes series resonance with the capacitor 212 and the antenna coil 211 of the antenna circuit 210B and is sent out through the antenna coil 211. .
On the other hand, at the time of reception, the transmission system circuit 220A outputs a certain carrier, and a signal subjected to load modulation from an external non-contact type IC card is supplied to the reception system circuit 240.
Subsequent basic operations are the same as those shown in FIGS. 6 and 7, and a detailed description thereof will be omitted.
In this way, when functioning as a reader / writer device, the switches 282 and 283 connected to the resonance circuit of the antenna circuit 210B are switched, and in this case, the series resonance circuit is configured by opening them.

Next, the operation of the communication device 200B when operating in the card mode will be described.
In the card mode, the switches 282 and 283 of the circuit switching unit 280B are set to ON by the mode control signal MD, and the positive phase output (terminal) 221A of the transmission system circuit 220A is connected to the ground potential GND and in parallel with this. Thus, the reverse phase output (terminal) 222A is also connected to the ground potential GND.
As a result, one end A and B of the capacitor 212 and the antenna coil 211 of the antenna circuit 210B are grounded, and a parallel resonant circuit is equivalently formed.
Then, a node ND210, which is a common connection point between the capacitor 212 and the antenna coil 211, is connected to the reception system circuit 240 for card reception, and is set to operate as a card function.

When a signal is supplied from an external reader / writer device or the like, a signal is induced in the antenna coil 211, a resonance frequency signal is extracted by the parallel resonance circuit of the capacitor 212 and the antenna coil 211, and the signal is input to the reception system circuit 240. Entered. Subsequent operations are the same as described above, and are omitted here.
On the other hand, at the time of reply, the switch 250 is switched to the connection between the fixed contact a and the operation contact c by the mode control signal MD, the transmission data is supplied to the reply circuit 230, and load modulation is applied to the carrier from the reader / writer device. Done.
As described above, when functioning as a card device, the switches 282 and 283 connected to the resonance circuit of the circuit switching unit 280B are switched, and in this case, they are short-circuited to form a parallel resonance circuit.

Although the description so far is for the case where the ON resistance of the switch is 0Ω, it actually has a certain ON resistance. Therefore, when the ON resistance of the switch is large, the switch enters in series with the antenna coil and reduces the reception efficiency in the card mode. This is equivalent to the case where the resistance of R1 in FIG. 1 is large.
Therefore, it is possible to use a combination of the capacitor 213 in parallel with the antenna coil 211 and the capacitor 212 in series as described below.

  FIG. 9 is a diagram showing a fourth configuration example of a communication device incorporating a non-contact type IC card function and a reader / writer function mounted on a mobile phone according to an embodiment of the present invention.

  The communication device 200C of FIG. 9 is different from the communication device 200A of FIGS. 6 and 7 in that a capacitor 213 having a capacitance Cb is connected in parallel to the antenna coil 211 in the antenna circuit 210C.

In the antenna circuit 210A of the communication apparatus 200A shown in FIGS. 6 and 7, the capacitor 213 connected in parallel to the antenna coil 211 is not provided.
In the communication device 200C of FIG. 9, by adjusting the capacitance Cb of the capacitor 213 and the capacitance Ca of the capacitor 212, the card function and the reader / writer function are satisfied even if there is an ON resistance in series with the antenna coil 211 at the resonance frequency. Like to do.

Except for the antenna circuit 210C, it is the same as FIG. 6 and FIG.
The positive phase output terminal 221A of the transmission system circuit 210A is connected to one terminal A of the capacitor 212, and the negative phase terminal 222A is connected to the other terminal B of the antenna coil 211 and one terminal (first electrode) of the capacitor 213. Is done. The other terminal (second electrode) of the capacitor 213 is connected to the node ND210. Here, the receiving system circuit 240 may be either a reader / writer or a card. It will be described as a system circuit.
The switch 281 of the circuit switching unit 280A is connected between the positive phase output terminal 221A and the reverse phase terminal 222A of the transmission system circuit 220A, the switch 271 is turned ON / OFF according to the reader / writer mode and the card mode, and the antenna circuit 210C is parallel It is configured to be set to either a resonance circuit or a series resonance circuit.

In the reader / writer mode, the switch 281 is set to OFF by the mode control signal MD, and a series resonance circuit is formed in the antenna circuit 210C.
The carrier flows through the transmission system circuit 220A to the capacitor 212 and the antenna coil 211 of the antenna circuit 210C and further to the capacitor 213, and is transmitted as a radio wave from the antenna coil 211 to perform a reading operation.
On the other hand, the signal input from the antenna coil 211 is extracted by the antenna coil 211, the capacitor 213, and the capacitor 212 constituting the series resonance circuit, and the extracted signal is supplied to the reception system circuit 240 to perform the receiving operation. .
In the card mode, the switch 281 is set to the ON state, and a parallel resonance circuit is formed by the capacitor 212, the capacitor 213, and the antenna coil 211. Data is exchanged with the receiving system circuit 240 of the card using this parallel resonant circuit. Since this operation is the same as the operation described in FIG. 6, FIG. 7, FIG. 8, etc., detailed description is omitted.

  Next, the input impedance of the antenna circuit 210C including the antenna coil 211 in the card mode and the reader / writer mode will be described.

  FIG. 10 and FIG. 11 below show the impedance characteristics in the card mode and the reader / writer mode, and each value changes under the condition that the added value of the capacitors 212 and 213 and (Ca + Cb) are constant. The impedance was calculated.

First, in the card mode, the switch 281 is set to ON, and a parallel resonant circuit is formed.
FIG. 10 shows a relative value as a result of simulation of the impedance of the circuit assuming that the switch 281 has an ON resistance. The horizontal axis of FIG. 10 shows the capacitance value when the capacitances Ca and Cb of the capacitors 212 and 213 are changed, and the vertical axis shows the impedance Z on an arbitrary scale.

In FIG. 10, when the capacitance Cb of the capacitor 213 is decreased and the capacitance Ca of the capacitor 212 is increased, the impedance Z is generally decreased, which is not suitable for the card mode.
On the contrary, if the capacitance Ca of the capacitor 212 is decreased and the capacitance Cb of the capacitor 213 is increased, the impedance Z increases, which is suitable for the card mode. However, if the ON resistance of the switch is large, the impedance decreases. Reception efficiency is reduced. When the ON resistance is large, it can be seen that the values of the capacitors Ca and Cb are large and affect the impedance.

Next, changes in impedance in the reader / writer mode will be described.
At this time, the switch 281 is set to the OFF state, and the impedance is adjusted by adjusting the capacitance Ca of the capacitor 212 and the capacitance Cb of the capacitor 213.
A simulation was performed with respect to the impedance Z of the series resonance circuit for data in which the capacitances Ca and Cb of the capacitors 212 and 213 shown in FIG. 9 were adjusted to change the ON resistance. The relative values of the simulation results are shown in FIG.
In FIG. 11, the horizontal axis indicates values when the capacitances Ca and Cb of the capacitors 212 and 213 are changed, and the vertical axis indicates an arbitrary scale and the value of the impedance Z of the series resonance circuit.

As a result of the simulation, in the series resonance circuit, when the capacitance Cb of the capacitor 213 is small and the capacitance Ca of the capacitor 212 is large, the impedance Z is small and suitable for the reader / writer mode, but when the ON resistance of the switch 281 increases, the impedance increases. This increases the transmission efficiency of the reader / writer.
As the capacitance Cb of the capacitor 213 increases and the capacitance Ca of the capacitor 212 decreases, the impedance increases. When the capacitance Cb exceeds a certain range, the impedance Z increases rapidly, which is not suitable for a reader / writer.
From this result, it is necessary to select a range in which the impedance Z of the series resonant circuit of FIG. 11 is small and the impedance Z of the parallel resonant circuit of FIG. 10 is large. It is necessary to select the optimum Ca and Cb values while looking at the performance of the writer.

That is, the simulation results of FIG. 10 and FIG. 11 described above show the impedance characteristics of the card mode and the reader / writer mode. In the card mode, the larger the capacitance Cb of the capacitor 213 is, the less affected by the ON resistance. On the other hand, the impedance is high, but in the reader / writer mode, the smaller the capacitance Cb of the capacitor 213, the smaller the impedance, which is advantageous.
Therefore, it is necessary to set the optimal capacitances Ca and Cb of the capacitors 212 and 213 in order to satisfy both functions. If the ON resistance is reduced, the capacitor 213 can be deleted in the card mode.

  FIG. 12 is a diagram showing a fifth configuration example of a communication device incorporating a non-contact type IC card function and a reader / writer function mounted on a mobile phone according to an embodiment of the present invention.

The communication device 200D of FIG. 12 is different from the communication device 200C of FIG. 9 in that two capacitors 212-1 and 212-2 are connected in series instead of connecting one capacitor 212 between the node ND210 and the terminal A. The switch 214 that is turned ON / OFF by the mode control signal MD is connected between the connection node ND211 between the capacitors 212-1 and 212-2 and the terminal A, and the node ND211 is connected to the high resistance 215. And connected to the power supply potential Vdd.
With this configuration, the communication device 200C of FIG. 9 has a high tuning frequency even when the card function is used. Therefore, the communication device 200D switches the tuning frequency between the card mode and the reader / writer function. Thus, the characteristics in the card mode and the reader / writer mode are made equal.
In the communication device 200D of FIG. 12, in the card mode, the capacitor 212-2 of the series capacitors 212-1 and 212-2 is bypassed by the switch 214 so as not to contribute to tuning.

The operation will be briefly described.
In the card mode, the switch 214 and the switch 281 of the circuit switching unit 280A are set to ON by the mode control signal MD.
Therefore, in the antenna circuit 210D, a parallel resonant circuit is formed by the antenna coil 211 and the capacitors 212-1 and 213. Only the capacitor 212-1 of the series capacitors 212-1 and 212-2 contributes to the tuning.

In the reader / writer mode, the switch 214 and the switch 281 of the circuit switching unit 280A are set to OFF by the mode control signal MD.
In this case, it is the series capacitance Ct of the capacitor 212-1 having the capacitance Ct1 and the capacitor 212-2 having the capacitance Ct2. A series resonance circuit is formed by the antenna coil 211 and the capacitors 212-1, 212-2, and 213.
In this case, since the node ND211 is biased by the high resistance 215, the potential Vrpd becomes Vdd.
Then, the potential Vrpd of the node ND211 is lower than the potential Vrx of the node ND210 by the divided voltage of the capacitors 212-1 and 212-2.
The potential of the node ND210 and the values of the capacitors Ct1 and Ct2 of the capacitors 212-1 and 212-2 are selected so that the divided voltage falls within the allowable voltage range.

  According to the communication device 200D of FIG. 12, the tuning frequency is switched between the card mode and the reader / writer function, and a portable information device having a communication device with good characteristics in the card mode and the reader / writer mode is configured. It becomes possible to do.

  FIG. 13 is a diagram illustrating a sixth configuration example of a communication device that incorporates a non-contact type IC card function and a reader / writer function that are mounted on a mobile phone according to an embodiment of the present invention.

The communication device 200E in FIG. 13 is different from the communication device 200A in FIGS. 6 and 7 in that instead of connecting one capacitor 212 between the node ND210 and the terminal A, the terminal A and the transmission system circuit 220A are connected. This is because another capacitor 212-2 is further connected between the output terminal 221A of the first capacitor Cb.
The communication device 200E of this example is configured such that the tuning frequency in the reader / writer mode is higher than the card mode, similarly to the communication device 200D of FIG.

  In the reader / writer mode, the switch 281 is set to OFF by the mode control signal MD. As a result, the two capacitors 212-1 and 212-2 are connected in series, and the total capacity Ctotal is given by the following equation and becomes smaller.

[Equation 6]
Ctotal = 1 / ((1 / Ca) + (1 / Cb)) (6)

  Accordingly, the resonance frequency fo in the reader / writer mode increases as follows.

[Equation 7]
fo = 1 / (2π√ (L * Ctotal)) (7)

  In the card mode, since the switch 281 is set to ON by the mode control signal MD, the resonance frequency is determined by the capacitance Ca of the capacitor 212-1 and the inductance L11 of the antenna coil 211.

  According to the communication device 200E of FIG. 13, the tuning frequency is switched between the card mode and the reader / writer function, and a portable information device having a communication device with good characteristics in the card mode and the reader / writer mode is configured. It becomes possible to do.

  FIG. 14 is a diagram showing a seventh configuration example of a communication apparatus incorporating a non-contact type IC card function and a reader / writer function mounted on a mobile phone according to an embodiment of the present invention.

The communication device 200F of FIG. 14 differs from the communication device 200E of FIG. 13 in that, instead of connecting one capacitor 212 between the node ND210 and the terminal A, between the terminal A and the operating contact of the switch 281. This is because another capacitor 212-3 of the capacitance Cc is further connected.
Unlike the communication device 200E of FIG. 13, the communication device 200F of this example is configured such that the tuning frequency in the reader / writer mode is lower than the card mode.

  At the time of the reader / writer, the switch 281 is set to OFF by the mode control signal MD, so that the resonance frequency is determined by the capacitance Ca of the capacitor 212-1 and the inductance L11 of the antenna coil 211.

  In the card mode, the switch 281 is set to ON by the mode control signal MD. As a result, the two capacitors 212-1 and 212-3 are connected in series, and the total capacity Ctotal is given by the following equation and becomes smaller.

[Equation 8]
Ctotal = 1 / ((1 / Ca) + (1 / Cc)) (8)

  Accordingly, the resonance frequency fo in the reader / writer mode increases as follows.

[Equation 9]
fo = 1 / (2π√ (L * Ctotal)) (9)

  According to the communication device 200F of FIG. 14, the tuning frequency is switched between the card mode and the reader / writer function, and a portable information device having a communication device with good characteristics in the card mode and the reader / writer mode is configured. It becomes possible to do.

As described above, the communication device incorporating the card function and the reader / writer function does not need to have a separate antenna for the reader / writer and the card, and only one is required. As a result, problems due to interference between the reader / writer W antenna and the card antenna are also eliminated.
Further, since the number of antennas is reduced, the number of peripheral parts and circuits is reduced, the design is facilitated, and the cost can be reduced.
Furthermore, a high-performance front-end circuit can be obtained with a simple configuration at low parts cost and design cost.
In addition, the switch in this embodiment can be realized by a normal CMOS process, and can be mounted on a small and portable device.

In the above description, the case where the communication apparatus according to the present embodiment is mounted on an information device such as a mobile phone has been described as an example. However, not only the information device but also FIGS. 6 (FIG. 7), FIG. 8, FIG. 9, FIG. 12, FIG. 13, and FIG. 14, it is also possible to constitute a non-contact type IC card provided with the communication device.
The contactless IC cards 300 and 300A to 300F shown in FIGS. 15 to 21 are configured in the communication devices shown in FIGS. 5, 6 (FIG. 7), FIG. 8, FIG. 9, FIG. Further, the CPU 310 and the memory 320 are provided.
In this case, a battery or the like is incorporated as a power source in order to realize a reader / writer function. Alternatively, it is possible to employ a configuration in which power induced by the antenna circuit is smoothed and used as drive power.

According to the present invention, a resonance circuit corresponding to a mode can be formed with one antenna, peripheral components and circuits can be reduced, design can be facilitated, cost can be reduced, and high performance can be achieved with a simple configuration. Therefore, the present invention can be applied to information devices such as mobile phones and non-contact type IC cards.

Claims (24)

A first transmission circuit having first and second output terminals and outputting a carrier from the first and second output terminals in the first mode;
A node, an inductor having one end connected to the node and the other end connected to a second output terminal of the first transmission circuit, and the node and a first output terminal of the first transmission circuit. An antenna circuit including at least one capacitor connected therebetween;
A second transmission circuit connected to the node of the antenna circuit and outputting transmission data in the second mode;
At least one receiving circuit connected to the node of the antenna circuit and performing a receiving process on data received by the antenna circuit;
A circuit switching unit for forming the antenna circuit as a series resonant circuit including the inductor and a capacitor in the first mode, and forming the antenna circuit as a parallel resonant circuit including the inductor and a capacitor in the second mode;
A communication device. The first transmission circuit includes:
A first transmission buffer that connects the first output terminal to a power supply potential or a reference potential in the first mode, and connects the first output terminal to a reference potential in the second mode;
A second transmission buffer that connects the second output terminal to a reference potential or a power supply potential during the first mode, and connects the second output terminal to a reference potential during the second mode;
The communication device according to claim 1, wherein the circuit switching unit is formed by sharing the first transmission buffer and the second transmission buffer. The circuit switching unit is connected between the first output terminal and the second output terminal of the first transmission circuit, and is held in the off state during the first mode and is held in the on state during the second mode. The communication device according to claim 1, further comprising a switch. The communication apparatus according to claim 3, wherein the antenna circuit further includes a capacitor connected in parallel to the inductor and connected to the node and the other end of the inductor. The antenna circuit is
The capacitor connected to the node;
Depending on the state of the switch, it is included in either the resonance circuit of the series resonance circuit formed in the first mode or the parallel resonance circuit formed in the second mode, and is connected in series with the capacitor. Including other capacitors,
The communication apparatus according to claim 3. The antenna circuit is
The capacitor connected to the node;
Depending on the state of the switch, it is included in either the resonance circuit of the series resonance circuit formed in the first mode or the parallel resonance circuit formed in the second mode, and is connected in series with the capacitor. Including other capacitors,
The communication device according to claim 4, wherein a connection node of the two capacitors connected in series is connected to a power supply potential via a load element. The communication device according to claim 4, wherein the capacitance of each capacitor is set such that the impedance of the parallel resonant circuit in the second mode is set to be larger than the impedance of the series resonant circuit in the first mode. The circuit switching unit is
A first switch connected between a first output terminal of the first transmission circuit and a reference potential, held in an off state in the first mode, and held in an on state in the second mode;
A second switch connected between the second output terminal of the first transmission circuit and a reference potential, held in the off state during the first mode, and held in the on state during the second mode;
The communication device according to claim 1. A first transmission circuit having first and second output terminals and outputting a carrier from the first and second output terminals in the reader / writer mode;
A node, an inductor having one end connected to the node and the other end connected to a second output terminal of the first transmission circuit, and the node and a first output terminal of the first transmission circuit. An antenna circuit including at least one capacitor connected therebetween;
A second transmission circuit connected to the node of the antenna circuit and load-modulating transmission data in card mode;
At least one receiving circuit connected to the node of the antenna circuit and performing a receiving process on data received by the antenna circuit;
In response to a mode control signal, the antenna circuit is formed as a series resonant circuit including the inductor and a capacitor in the reader / writer mode, and the antenna circuit is formed as a parallel resonant circuit including the inductor and a capacitor in the card mode. A circuit switching unit;
Memory,
A control unit that selectively supplies the transmission data to the first transmission circuit or the second transmission circuit, performs predetermined processing on the reception data of the reception circuit, and controls access to the memory;
Non-contact type IC card having The first transmission circuit includes:
A first transmission buffer that connects the first output terminal to a power supply potential or a reference potential in the reader / writer mode, and connects the first output terminal to a reference potential in the card mode;
A second transmission buffer that connects the second output terminal to a reference potential or a power supply potential during the reader / writer mode, and connects the second output terminal to a reference potential during the card mode;
The non-contact type IC card according to claim 9, wherein the circuit switching unit is formed by sharing the first transmission buffer and the second transmission buffer. The circuit switching unit is connected between the first output terminal and the second output terminal of the first transmission circuit, and is held in the off state in the reader / writer mode and held in the on state in the card mode. The non-contact type IC card according to claim 9, further comprising a switch. The contactless IC card according to claim 11, wherein the antenna circuit further includes a capacitor connected to the node and the other end of the inductor in parallel with the inductor. The antenna circuit is
The capacitor connected to the node;
Depending on the state of the switch, the other included in the resonance circuit of the series resonance circuit formed in the reader / writer mode or the parallel resonance circuit formed in the card mode and connected in series with the capacitor Including a capacitor,
The non-contact type IC card according to claim 12. The antenna circuit is
The capacitor connected to the node;
Depending on the state of the switch, the other included in the resonance circuit of the series resonance circuit formed in the reader / writer mode or the parallel resonance circuit formed in the card mode and connected in series with the capacitor A capacitor,
The contactless IC card according to claim 12, wherein a connection node of the two capacitors connected in series is connected to a power supply potential via a load element. The non-contact type IC card according to claim 12, wherein the capacitance of each capacitor is set such that the impedance of the parallel resonance circuit in the card mode is set to be larger than the impedance of the series resonance circuit in the reader / writer mode. The circuit switching unit is
A first switch connected between a first output terminal of the first transmission circuit and a reference potential, held in an off state in the reader / writer mode, and held in an on state in the card mode;
A second switch connected between a second output terminal of the first transmission circuit and a reference potential, held in an off state in the reader / writer mode, and held in an on state in the card mode. Item 10. A non-contact type IC card according to Item 9. An information device having a communication function with a communication network,
A communication device having a reader / writer function and a card function;
The communication device is
A first transmission circuit having first and second output terminals and outputting a carrier from the first and second output terminals in the first mode;
A node, an inductor having one end connected to the node and the other end connected to a second output terminal of the first transmission circuit, and the node and a first output terminal of the first transmission circuit. An antenna circuit including at least one capacitor connected therebetween;
A second transmission circuit connected to the node of the antenna circuit and outputting transmission data in the second mode;
At least one receiving circuit connected to the node of the antenna circuit and performing a receiving process on data received by the antenna circuit;
A circuit switching unit for forming the antenna circuit as a series resonant circuit including the inductor and a capacitor in the first mode, and forming the antenna circuit as a parallel resonant circuit including the inductor and a capacitor in the second mode;
Information equipment with. The first transmission circuit includes:
Connect the first output terminal to the first mode to the power supply potential or a reference potential, said the second mode and the first transmission buffer to be connected to a reference potential the first output terminal,
A second transmission buffer for connecting the second output terminal to a reference potential or a power supply potential during the first mode and for connecting the second output terminal to a reference potential during the second mode;
The information device according to claim 17, wherein the circuit switching unit is formed by sharing the first transmission buffer and the second transmission buffer. The circuit switching unit is connected between the first output terminal and the second output terminal of the first transmission circuit, and is held in the off state during the first mode and is held in the on state during the second mode. The information device according to claim 17, further comprising a switch. The information device according to claim 19, wherein the antenna circuit further includes a capacitor connected to the node and the other end of the inductor in parallel with the inductor. The antenna circuit is
The capacitor connected to the node;
Depending on the state of the switch, it is included in either the resonance circuit of the series resonance circuit formed in the first mode or the parallel resonance circuit formed in the second mode, and is connected in series with the capacitor. Including other capacitors,
The information device according to claim 20. The antenna circuit is
The capacitor connected to the node;
Depending on the state of the switch, it is included in either the resonance circuit of the series resonance circuit formed in the first mode or the parallel resonance circuit formed in the second mode, and is connected in series with the capacitor. Including other capacitors,
The information device according to claim 20, wherein a connection node of the two capacitors connected in series is connected to a power supply potential via a load element. 21. The information device according to claim 20, wherein a capacitance of each capacitor is set so that an impedance of the parallel resonance circuit in the card mode is set to be larger than an impedance of the series resonance circuit in the first mode. The circuit switching unit is
A first switch connected between a first output terminal of the first transmission circuit and a reference potential, held in an off state in the first mode, and held in an on state in the second mode;
A second switch connected between the second output terminal of the first transmission circuit and a reference potential, held in the off state during the first mode, and held in the on state during the second mode. The information device according to claim 17.

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