JP2008147912A - Communication system, information equipment, and communicating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication system and information equipment capable of preventing a null phenomenon that originally occurs in a particular distance and consequently achieving stable and highly reliable IC card communication, and a communicating method. <P>SOLUTION: The communication system comprises: an antenna circuit 119 including a resonance circuit; a load element 13 connected to the antenna circuit; a plurality of load elements 114 and 115 for modulation control connected to the antenna circuit 119; and control parts 116, 117 and 118 for changing the number of load elements for modulation control connected to the antenna circuit 119 in a load modulation section during load modulation on and during load modulation off to optimize a load modulation point. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a communication device capable of communicating with a non-contact type IC card, information equipment such as a personal computer and a mobile phone, and a communication method.

  The development of IC card technology in recent years is remarkable, and it has been used conveniently in various fields such as railway tickets, purchase of goods, and entry / exit management.

  Many of these systems do not have a battery on the IC card side, and operate the IC card by non-contact power feeding by electromagnetic waves sent from a reader / writer (hereinafter referred to as R / W) side ( For example, see Patent Documents 1, 2, and 3).

The application system requires bidirectional data transmission from the R / W to the IC card (downstream) and from the IC card to the R / W (upstream) direction.
And about the down direction, the objective is achieved by carrying out amplitude displacement keying (ASK: Amplitude sift keying) modulation of the carrier sent out from R / W.

On the other hand, in the upward direction, the IC card does not have a power source and does not have a function of transmitting a carrier from itself.
For this reason, the IC card receives the carrier transmitted from the R / W by the load resistance connected to the tuning circuit of the inductor L and the capacitor C, and the load resistance corresponding to “1” / “0” of the transmission data. The data transmission function is realized by a so-called “load modulation method” in which the value of the signal is changed.

On the R / W side, it is detected as a voltage change of the antenna coil that occurs in response to a change in the value of the load resistance on the IC card side, and uplink data is reproduced.
Japanese Patent No. 3488166 JP 2004-356765 A JP 2005-136944 A

The “load modulation method” has the advantage that data transmission in the upstream direction can be realized with a simple configuration even from an IC card without a battery, but on the other hand, it is a method of switching the load of the L / C coupling circuit. Therefore, in principle, load modulation is not performed at a specific distance, a so-called “null phenomenon” occurs, and inconvenience occurs that communication in the upstream direction cannot be performed.
The null phenomenon will be described below with reference to the drawings.

  FIG. 1 shows a principle configuration example of an IC card and an R / W.

The IC card 1 includes an antenna coil 11, a capacitor 12 connected in parallel to the antenna coil 11, a load resistor 13 having a resistance value R1 connected in parallel to the antenna coil 11 and the capacitor 12, and a load modulation resistor 14 having a resistance value R2. And a switch (SW) 15 connected in series to the load modulation resistor 14.
As shown in FIG. 1, the R / W 2 includes an antenna coil 21, a capacitor 22, a capacitor (matching circuit) 23, a carrier signal source (OSC) 24, and an ASK demodulator connected in parallel to the antenna coil 21. Including a receiving circuit 25.

  The OSC 24 on the R / W 2 side is a carrier signal source having an oscillation frequency fc of 13.56 MHz, for example, and drives a parallel resonance circuit of the antenna coil 21 and the capacitor 22 via the matching circuit 23.

The antenna coil 11 on the IC card 1 side and the antenna coil 21 on the R / W2 side are electromagnetically coupled with a coupling coefficient k.
The coupling coefficient k is a value depending on the distance between the IC card 1 and R / W2, and k = 0 when the distance = ∞.

On the IC card 1 side, a carrier sent from the R / W 2 is extracted by a parallel resonance circuit including an antenna coil 11 and a capacitor 12 and terminated by load resistors 13 and 14.
The switch 15 provided in the IC card 1 is a load modulation changeover switch, and performs an “ON” / “OFF” operation according to “1” / “0” of the input of the load modulation signal LMS. Do.
That is, when the switch 15 is “ON”, the load resistance becomes the resistances 13 and 14, and when it is “OFF”, the load resistance changes only to the load resistance 13, so that the load impedance on the IC card 1 side viewed from the R / W2 side is The change is detected as a change in the voltage V1 across the antenna coil 21.
However, the relationship between the change in the load resistance and the change in the voltage V1 across the antenna coil 11 is not uniform, and greatly depends on the value of the distance ∝ coupling coefficient k.

In other words, in the load modulation method shown in FIG. 1, the magnetic field output from the R / W2 antenna 21 passes through the antenna 11 on the IC card 1 side, thereby generating a voltage at the antenna end. When a load resistor 13 is connected to the antenna end (the resistor 13 is a load on the entire card side), a current flows through the antenna end, and an inverted magnetic field in the direction opposite to the magnetic field from the antenna 21 of R / W2 is generated.
Normally, since the entire load resistance 13 on the IC card 1 side is as large as several kΩ, a large reversal magnetic field does not occur. However, when a signal from the IC card 1 is returned (load modulation), the load modulation control resistor 14 is turned on. It is observed that the magnetic field output from the R / W2 side is changed by / OFF (the load on the card side is variable). This change is detected by the reception circuit 25 on the R / W2 side and the reply from the card is recognized.

Next, the null point will be described with reference to FIG.
In FIG. 2, the horizontal axis indicates the distance between the IC card 1 and the R / W 2, and the vertical axis indicates the communication result between the R / W 2 and the IC card 1.

In the example of FIG. 2, the case where a normal reply is sent from the IC card 1 to the transmission signal from the R / W 2 is communication OK. For example, when communication is performed 100 times, the time of 100 communication OK is 100. %.
Currently, since there are many types of non-contact IC cards and R / W, a communication NG point (null point) as shown by B in FIG. 2 occurs depending on the combination.

  FIG. 3 is a diagram showing a received waveform on the R / W side at the null point.

  For example, when the switch (SW) 15 in the IC card 1 is controlled to ON, OFF, ON, OFF during load modulation, the waveform of A is small when ON (section A in FIG. 2), but the waveform of C Is smaller when it is OFF (section C in FIG. 2). Therefore, when changing from A to C, there is a point where the received voltage on the R / W2 side does not change even when load modulation such as B is performed. This point varies depending on the load resistance 13 (resistance value R1) and the load variation control adjustment resistor 14 (resistance value R2).

FIG. 4 is a diagram showing the R / W received voltage V1 (FIG. 1) when the load resistance on the IC card side is varied.
In FIG. 4, the horizontal axis represents the resistance value of the load resistance, and the vertical axis represents the received voltage V1.

  As shown in FIG. 4, since the characteristic curve when the resistance is varied is concave, the antenna end voltage on the R / W2 side is changed even if the resistance value is changed at two points indicated by P1 and P2 in FIG. Indicates that it will not change.

FIG. 5 shows a case where the load resistance value is optimally set so that there is no point where the antenna end voltage on the R / W2 side does not change during load modulation (SW: ON) and no modulation (SW: OFF). ing.
However, in this case, since the resistance value R1 of the load resistor 13 is reduced even when there is no modulation, the communication characteristics are adversely affected.
Hereinafter, the adverse effect on the communication characteristics will be described.

  FIG. 6 is a diagram illustrating a configuration example including the receiving circuit of the IC card 1.

  When the resistance value R1 of the load resistor 13 is decreased, the end voltage of the antenna 11 is decreased, so that the voltage V2 input to the receiving circuit 16 is also decreased, and the communication distance at a long distance is deteriorated.

  FIG. 7 is a diagram for explaining the influence on R / W.

In recent years, portable devices having a card function and an R / W function have been put into practical use.
Therefore, when the load resistance 27 (resistance value R1) is reduced, the current from the transmission signal Vrw of R / W2A flows to the resistor 27 in addition to the end of the antenna 21, and as a result, the current flowing to the antenna 21 decreases. However, the magnetic field radiated from the antenna 21 is also reduced, affecting the R / W2A communication characteristics.

As described above, the proposed method has a disadvantage that a null point is generated by the combination of the IC card and the R / W.
Further, even if the load resistance and the load modulation control resistance are changed to optimum values, the card reception characteristics and R / W characteristics are adversely affected.

  An object of the present invention is to provide a communication device, an information device, and a communication method that can prevent a null phenomenon originally occurring at a specific distance, and as a result, can realize stable and highly reliable IC card communication. .

  A first aspect of the present invention is a communication device having a load modulation type data transmission function, which includes an antenna circuit including a resonance circuit, a load element connected to the antenna circuit, and the antenna circuit. A plurality of modulation control load elements and a control unit that optimizes a load modulation point by changing the number of load elements for modulation control connected to the antenna circuit when load modulation is on and when load modulation is off in the load modulation section And have.

  Preferably, the control unit includes a first modulation control load element and a second modulation control load element, and the control unit connects or disconnects the first modulation control load element to the antenna circuit. A first switch for selecting whether to contribute to switching load modulation and whether to connect or disconnect the first modulation control load element to the antenna circuit for switching load modulation And a control circuit for controlling on / off of the first switch and the second switch.

  Preferably, the control unit controls the first switch and the second switch to be in an off state so that the load element is connected to the antenna circuit in the non-modulation period, and in the load modulation period. When the load modulation is on, the load element, the first modulation control load element, and the second modulation control load element are connected to the antenna circuit so as to contribute to load modulation. 2 in the load modulation section, the load element and the second modulation control load element are connected to the antenna circuit and contribute to the load modulation when the load modulation is off. The switch is turned off and the second switch is turned on.

  Preferably, in the non-modulation section, the control unit is configured to connect the load element, the first modulation control load element, and the second modulation control load element to the antenna circuit. The first switch and the second switch are controlled to be in an on state, and the load element is connected to the antenna circuit and contributes to the load modulation when the load modulation is on in the load modulation period. 2 in the load modulation section, and when the load modulation is off, the load element and the first modulation control load element are connected to the antenna circuit and contribute to the load modulation. The switch is turned off and the second switch is turned on.

  A second aspect of the present invention is an information device having an information processing function, including a communication device having a reader / writer function unit and a card function unit, and the communication device includes an antenna circuit including a resonance circuit and the reader circuit. The card function unit is shared by the writer function unit and the card function unit. The card function unit includes a load element connected to the antenna circuit, a plurality of modulation control load elements connected to the antenna circuit, and a load modulation section. A control unit that optimizes a load modulation point by changing the number of load elements for modulation control connected to the antenna circuit when modulation is on and when load modulation is off.

  According to a third aspect of the present invention, there is provided a load modulation communication method using a load element connected to an antenna circuit and a plurality of modulation control load elements connected to the antenna circuit. The load modulation point is optimized by changing the number of load elements for modulation control connected to the antenna circuit when load modulation is on and when load modulation is off.

According to the present invention, in order to avoid the null point, the number of load elements for modulation control connected to the antenna circuit when the load modulation is on and when the load modulation is off is changed by the control unit in the load modulation section.
In this way, the load modulation point is optimized by making it possible to adjust the impedance during the load modulation period and during no modulation.

  According to the present invention, it is possible to prevent a null phenomenon that originally occurs at a specific distance, and as a result, it is possible to realize stable and highly reliable IC card communication.

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

  FIG. 8 is a diagram showing a configuration example of a communication system to which a non-contact type IC card and a mobile phone as a portable information device according to an embodiment of the present invention are applied.

  A communication system 100 shown in FIG. 8 includes a contactless IC card 110 as a communication device, a mobile phone 120, a base station 130, a communication network 140, and a server 150.

  The IC card 110 according to the present embodiment receives a carrier sent from an R / W (reader / writer) function unit mounted with a mobile phone 120 by a load resistance connected to a tuning circuit of an inductor L and a capacitor C, and sends data. The data transmission function is realized by a so-called “load modulation method” in which the value of the load resistance is changed corresponding to “1” / “0”.

  FIG. 9 is a circuit diagram showing a configuration example of the IC card according to the present embodiment.

The IC card 110 is connected to one end side of an antenna coil 111, a capacitor 112 connected in parallel to the antenna coil 111, load resistors 113, 114, 115 connected in parallel to the antenna coil 111 and the capacitor 112, and the load resistor 114. The first switch (SW1) 116, the second switch (SW2) 117 connected to one end of the load resistor 115, and the control circuit 118 are included.
An antenna circuit 119 which is a parallel resonance circuit is configured by the antenna coil 111 and the capacitor 112. The resistor 114 constitutes a first modulation control load element, and the resistor 115 constitutes a second modulation control load element.
The resistance value of the load resistor 113 is set to R1, the resistance value of the load resistor 114 is set to R2, and the resistance value of the load resistor 115 is set to R3.
Each resistance value is set so as to satisfy the relationship of R2 <R3 <R1.

The antenna coil 111 of the IC card 110 is electromagnetically coupled with the antenna coil 211 in the communication device 200 (126) of the mobile phone 120 with a coupling coefficient k.
The coupling coefficient k is a value that depends on the distance between the IC card 110 and the communication device 200 (R / W) side of the mobile phone 120, and k = 0 when the distance = ∞.

On the IC card 110 side, a carrier sent from the communication device 200 (R / W) is extracted by a parallel resonance circuit including an antenna coil 111 and a capacitor 112, and terminated with load resistors 113, 114, and 115.
Switches 116 and 117 provided on the IC card 110 are load modulation changeover switches.

The control circuit 118 performs control so that the switches 116 and 117 are turned off in the non-modulation period. In this case, the load resistance is only 113, and the resistance value is R1.
The control circuit 118 controls the switch (SW2) 117 to be turned on during the load modulation period, and according to “1” / “0” of the input of the load modulation signal LMS during the period when the switch 117 is on. The “ON” / “OFF” operation of the switch (SW1) 116 is controlled.
That is, when the switch 116 is off and the switch 117 is on, the load resistances 113 and 115 are obtained, and the overall load resistance value is the parallel resistance value of the resistance value R1 of the load resistance 113 and the resistance value R3 of the load resistance 115. Become.
When the switches 116 and 117 are on, the load resistances are 113, 114, and 115, and the overall load resistance values thereof are the resistance value R1 of the load resistance 113, the resistance value R2 of the load resistance 114, and the resistance of the load resistance 115. A parallel resistance value with the value R3 is obtained.

  Thus, in the IC card 110 of this embodiment, in order to avoid the occurrence of a null state when the distance from the R / W side is varied, a plurality of switches (SW1) 116 and switches (SW2) are used. ) 117 and configured to control the load resistance when the load modulation is “ON” and the load resistance when the load modulation is “OFF”, respectively.

That is, in the upward direction communication of the proximity IC card (from the IC card to the R / W direction), the so-called load for performing data communication by changing the voltage at the R / W antenna coil end by switching the load resistance value in the card. Although modulation is employed, there is a distance (null point) where load modulation is theoretically not applied.
In this embodiment, in order to avoid the influence of the null phenomenon, a plurality of switches (SW1) 116 and a switch (SW2) 117 are provided, and the load resistance and load modulation “OFF” (OFF) at the time of load modulation “ON” are provided. ) ”Is configured to control the load resistance at each time to improve communication quality.

When the switch (SW1) 116 and the switch (SW2) 117 are “ON”, the load resistance becomes the resistance 113, 114, 115. When only the switch 117 is “ON”, the load resistance becomes the resistance 113, 115. When both the switches 116 and 117 are “OFF”, the load resistance changes only to the resistor 113, so that the load impedance on the IC card 110 side as viewed from the R / W side changes, and the change is the antenna coil 211. It is detected as a change in the voltage V1 at both ends.
However, the relationship between the change in the load resistance and the change in the voltage V1 across the antenna coil 211 is not uniform, and greatly depends on the value of the distance ∝ coupling coefficient k.

  FIG. 10 is a diagram illustrating a format example of packet data applied to proximity IC card communication.

  This packet 300 has a prefix code area (Preamble) 310 containing at least 48 bits of logical 0 data, a 2-byte synchronization code area (SYNC) 320, and an 8-bit length in which the length of the payload is set. An area (Length) 330, a payload area (Payload) 340 including n byte areas, and a cyclic redundancy check area (CRC) 350 are formed.

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

  FIG. 11 is a block diagram illustrating a basic configuration example of the mobile phone according to the present embodiment.

  As shown in FIG. 11, the cellular phone 120 includes a wireless communication unit 121 that performs wireless communication processing with the server 150 via the communication network 140, a display unit 122 that includes a liquid crystal display device (LCD), a numeric keypad, and the like. An operation unit 123 including operation keys, a voice processing unit 124 having a microphone and a speaker for performing voice input processing or voice output processing, a memory unit 125 for storing programs, message data, address data, IC card data, and the like, R Mode control, transmission data TD, and reception for realizing the overall function control, R / W function, and card function of the communication device 126 forming the front end circuit unit for realizing the / W function and the mobile phone 120 A control unit (CPU) 1 that performs predetermined processing on the data RD and accesses the memory unit 125 according to the predetermined processing. With a 7.

The wireless communication unit 121, the display unit 122, the operation unit 123, the voice processing unit 124, the memory unit 125, and the control unit 127 constitute a telephone unit as a normal mobile phone.
The communication device 126, the memory unit 125, and the control unit 127 constitute a card function unit that realizes an R / W function and an IC card function.
Further, it is possible to configure the mode designation, switching, and the like under the control of the control unit 127 in accordance with the operation of the operation unit 124.
At this time, the control unit 127 outputs, for example, a control signal and transmission data TD to the communication device 126, receives the reception data RD, and performs storage processing or the like in the memory unit 125. The memory unit 125 includes a nonvolatile memory such as a flash memory.
Note that the control unit 127 can be configured to be provided separately for the telephone unit and the card function unit.

FIG. 12 is a diagram illustrating a configuration example of a communication device having a built-in R / W function and a card function mounted on the mobile phone according to the embodiment of the present invention.
In FIG. 12, the communication device 126 of FIG.

  As shown in FIG. 12, the communication apparatus 200 includes an antenna circuit (antenna front end) 210, a transmission system circuit 220 including a carrier signal source (OSC) that generates a carrier having an oscillation frequency fc of 13.56 MHz, an ASK demodulation, and the like. And a receiving circuit 230 including a detector, a load modulation block 240, a resistor 250, and diodes 260 and 270. These components realize part of the R / W function and the card function.

  As shown in FIG. 12, the antenna circuit 210 includes an antenna coil 211, a capacitor 212 connected in parallel to the antenna coil 211, a capacitor 213 (matching circuit), and a switch (SW3) 214.

A node ND211 is formed by connecting one end of the antenna coil 211, the first electrode of the capacitor 211, and the first electrode of the capacitor 213.
A node ND212 is formed by the connection point between the second electrode of the capacitor 213 and the operating contact of the switch 214, and the other end of the antenna coil 211, the second electrode of the capacitor 212, and the fixed contact a of the switch 214 are connected to form a node ND213. Is formed.
The node ND211 is connected to the input of the receiving circuit 230 via the diode 260 and the resistor 250, and is connected to the load modulation block (return circuit) 240 via the diode 270. Further, the node ND212 is connected to the first output terminal 221 having the positive phase of the transmission system circuit 220, and the node ND213 is connected to the second output terminal 222 having the opposite phase.
The diodes 260 and 270 are connected as rectifier elements so that a negative voltage is not input.

When the antenna circuit 210 is in the R / W (reader / writer) mode, the switch 214 is controlled to be in an off state by, for example, the control unit 127 to form a series resonance circuit.
In the card circuit mode, the antenna circuit 210 is controlled to be turned on by the control unit 127 to form a parallel resonance circuit.

  The transmission system circuit 220 has a first output terminal 221 having a normal phase and a second output terminal 222 having a reverse phase, and ASK-modulates a carrier by a transmission buffer (not shown) by transmission data TD transferred from the control unit 117. Output from the first and second output terminals 221 and 223 to the antenna circuit 210.

The receiving circuit 230 is also used as a receiving circuit when the card function is used (card mode) and as a receiving circuit when the reader / writer function is used (reader / writer mode).
The receiving circuit 230 demodulates the information received during the card function and the reader / writer function, and outputs received data RD to the control unit 127.

  In the card mode, the load modulation block (reply circuit) 240 performs load modulation on the reply data read from the memory unit 125 in the control unit 127 and applies it to the node ND211 of the antenna circuit 210.

The load modulation block 240 includes, for example, load resistors 241 and 242 connected in parallel to the node ND211 via a diode 270, a switch (SW1) 243 connected to one end side of the load resistor 241, and one end of the load resistor 242. And a switch (SW2) 244 connected to the side. The resistance value of the load resistor 241 is set to R2, and the resistance value of the load resistor 243 is set to R3.
In the load modulation block 240, the control unit 127 performs control so that the switch (SW2) 244 is turned on in the load modulation period, and “1” of the input of the load modulation signal LMS during the period when the switch 244 is on. According to “/“ 0 ”, the“ ON ”/“ OFF ”operation of the switch (SW1) 243 is controlled.
That is, the load modulation block 240 is partially omitted, but has the same configuration and function for load modulation as the IC card 110 described with reference to FIG. Therefore, the details are omitted here.

  As described above, in the communication apparatus 200 of the present embodiment, in order to avoid the occurrence of a null state when the distance to the R / W side is varied, a plurality of switches (SW1) 243 and switches (SW2 ) 244 is provided to control the load resistance at the time of load modulation “ON” and the load resistance at the time of load modulation “OFF”, respectively.

In the reader / writer (R / W) mode, the switch 214 of the antenna circuit 210 is controlled to be turned off by the mode control signal, so that the antenna circuit 210 becomes a series resonance circuit.
By making the antenna circuit 210 a series resonant 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 switch 214 for switching the resonance circuit described above 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 receiving circuit 230 for data demodulation and data storage. Etc. are 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 213 of the antenna circuit 210 and the series resonance circuit of the antenna coil 211 via the transmission system circuit 220. 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 213 and the antenna coil 211 constituting the antenna circuit 210 are in a series resonance state at the operating frequency, the impedance thereof is zero, and the current flowing through the antenna coil 211 is maximized. As a result, transmission efficiency increases and the reach of radio waves increases.

In the card mode, the output terminals 221 and 222 of the normal phase and the reverse phase of the transmission system circuit 220 are set to HiZ (high impedance) and set so as not to affect the antenna circuit 210. Note that the output terminals 221 and 222 of the transmission system circuit 220 may be configured to be set to LoZ (low impedance) in phase.
That is, in the card mode, a mode control signal is supplied from the control unit 127, the switch 214 of the antenna circuit 210 is turned on, and the output terminals 221 and 222 between the normal phase and the reverse phase of the output of the transmission system circuit 220 are connected. Is short-circuited.
As a result, in the antenna circuit 210, the capacitor 213 and the antenna coil 211 constitute a parallel resonance circuit. In parallel with this, transmission data (reply data) TD is supplied to the load modulation block (reply circuit) 240.

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 213, and the extracted signal is input to the reception circuit 230. At this time, since the output terminals 221 and 222 of the transmission system circuit 220 are short-circuited, no signal is output from the transmission system circuit 220 or the operation of the transmission system circuit 220 is stopped.
In the receiving circuit 230, the transmission signal (information) of the reader / writer device is extracted from the magnetic field received by the demodulation circuit, and is decoded and output to the control unit 127 such as a CPU.
In the control unit 127, the decoded data is processed, data is stored in or read from the memory unit 125, or data read from the memory unit 125 is encoded.
The transmission data is subjected to load modulation in a load modulation block (reply circuit) 240 on the carrier signal from the reader / writer device.

  As described above, in this example, when used as a card, the switch 214 is turned ON, the antenna coil 211 and the capacitor 213 are connected in parallel, and at the same time, the front end is made to have a relatively high impedance. The card function can be satisfied even at a long distance.

  The receiving circuit 230 can be configured separately from a receiving system circuit dedicated to the card mode and a receiving system circuit dedicated to the reader / writer mode.

  Next, null generation avoidance control in the communication device 200 of the IC card 110 or the mobile phone 120 according to the present embodiment will be described in further detail with reference to FIGS. 13 and 14 by taking the IC card 110 as an example.

FIG. 13 is a diagram showing the received voltage V1 on the R / W side when the load resistance of the IC card of this embodiment is varied.
In FIG. 13, the horizontal axis represents the resistance value of the load resistance, and the vertical axis represents the received voltage V1.
FIG. 14 is a diagram showing the relationship between the switch control timing and the R / W reception waveform of the IC card of this embodiment in comparison with the normal configuration.

The load modulation ON point P3 and the negative modulation OFF point P2 are optimally set as shown in FIG. 13, but the point P2 is controlled using the switch (SW2) 117.
By turning on the switch (SW2) 117 with the switch (SW1) 116 turned off, the entire load resistance becomes a parallel resistance value of the resistance value R1 of the resistor 113 and the resistance value R3 of the resistor 115. In addition, when the switch (SW1) 116 is turned on in this state, the entire load resistance value is the parallel resistance value R1 // R2 / of the resistance value R1, the resistance value R2 of the resistance 114, and the resistance value R3 of the resistance 115. It becomes / R3 and moves to point P3.
The relationship of resistance values here is R2 <R3.

  At the time of card reception, which is a section in which load modulation is not performed, the switch 116 (SW1) and the switch 117 (SW2) are turned off, so that the entire load resistance value becomes the resistance value R1 of the resistor 113 and becomes the point P1.

Next, the relationship between the switch timing and the received waveform on the R / W side will be described.
Since load modulation is performed from the card after receiving a signal from the R / W, there is a non-modulation section before and after the load modulation section.
When the load resistance is not optimized in the normal configuration (in the case of FIG. 4), it indicates that the waveform at the antenna end on the R / W side does not change even when the switch SW is turned ON / OFF during the load modulation period. ing.
Next, when the load resistance is optimized in the normal configuration (in the case of FIG. 5), since the load resistance in the non-modulated state (SW is OFF) is reduced, the waveform in the non-modulated section is also small. It has become.
In the present embodiment in which a plurality of switches (SW1) 116 and switches (SW2) 117 are provided, by using the switch (SW2) 117 that is turned on only in the load modulation section, the signal in the non-modulation section is not degraded, and the load The modulation section indicates that optimum load modulation is performed.

In the above-described embodiment, an example in which a plurality of resistors for load modulation control are connected in parallel has been described. However, as shown in FIG. 15, resistors for load modulation control may be connected in series.
In this case, the switch (SW1) 116 is connected between both ends of the resistor 114, and the switch (SW2) 117 is connected between both ends of the resistor 115.

  In the IC card 110A of FIG. 15, it is possible to change the load state at three places by controlling as shown below.

Normal (unmodulated) resistance = R1 + R2 + R3,
Load modulation section (OFF) resistance = R1 + R2,
Load modulation section (ON) resistance = R1

That is, in the normal state, both the switch (SW1) 116 and the switch (SW2) 117 are OFF, and the load resistance value at that time is the resistance value R1 of the resistor 113, the resistance value R2 of the resistor 114, and the resistance value of the resistor 115. It becomes the series resistance value of R3.
When the load modulation is OFF, the switch (SW2) 117 is turned ON and the resistor 115 is bypassed, and the load resistance value at that time is a series resistance value of the resistance value R1 of the resistor 113 and the resistance value R2 of the resistor 114. .
When the load modulation is ON, the switch (SW2) 117 and the switch (SW1) 116 are turned ON and the resistors 114 and 115 are bypassed, and the load resistance value at that time is the resistance value R1 of the resistor 113.

  Also in this case, as described above, nulls that occur when the distance is varied can be avoided.

As described above, in the upward direction communication (from IC card to R / W direction) of proximity IC card, data communication is performed by changing the voltage at the antenna coil end of R / W by switching the load resistance value in the card. Although so-called load modulation is performed, there is a distance (null point) where load modulation is theoretically not applied.
In this embodiment, in order to avoid the influence of the null phenomenon, a plurality of switches (SW1) 116 and a switch (SW2) 117 are provided, and the load resistance and load modulation “OFF” (OFF) at the time of load modulation “ON” are provided. ) ”Is configured to control the load resistance at each time to improve communication quality.

As described above, according to the present embodiment, nulls generated when the distance is varied can be avoided, and stable and highly reliable communication is possible.
Since a control circuit, a switch, and the like can be built in the LSI, the mounting area can be reduced, and the component cost can be kept low.
Moreover, it is realizable with a simple structure which adds resistance and a switch.
In addition, there is an advantage that adjustment is easy because there is no influence on the reception system and the R / W side, and complicated adjustment is unnecessary when there are many combinations facing each other.

In the above-described example, a resistor is used for load modulation. However, the same can be applied to capacitive load modulation using a capacitance as a load, and the same effect as in the case of load resistance can be obtained. .
Moreover, although this embodiment demonstrated the case where load resistance was connected in parallel and series with respect to the antenna, it does not specifically limit regarding the connection position.

  In this embodiment, a mobile phone has been described as an example of information equipment. However, the present invention can be applied to other mobile terminals (PDA, etc.), personal computers, and the like.

2 shows an example of the basic configuration of an IC card and an R / W. It is a figure for demonstrating regarding a null point. It is a figure which shows the reception waveform by the side of R / W in a null point. It is a figure which shows the reception voltage V1 (FIG. 1) of R / W at the time of making load resistance by the side of IC card variable. It is a figure which shows the case where a load resistance value is set optimally so that the point which the antenna terminal voltage by the side of R / W2 may not generate | occur | produce at the time of load modulation (SW: ON) and no modulation (SW: OFF). It is a figure which shows the structural example containing the receiving circuit of a general IC card. It is a figure for demonstrating the influence in R / W. It is a figure which shows the structural example of the communication system with which the non-contact type IC card which concerns on embodiment of this invention, and the mobile telephone as a portable information device are applied. It is a circuit diagram which shows the structural example of the IC card which concerns on this embodiment. It is a figure which shows the example of a format of the packet data applied to proximity IC card communication. It is a block diagram which shows the basic structural example of the mobile telephone which concerns on this embodiment. It is a figure which shows the example of 1 structure of the communication apparatus incorporating the R / W function and card function which are mounted in the mobile telephone which concerns on embodiment of this invention. It is a figure which shows the reception voltage V1 by the side of R / W at the time of making load resistance of the IC card of this embodiment variable. It is a figure which shows the relationship between the switch control timing of the IC card of this embodiment, and a R / W reception waveform compared with a normal structure. It is a circuit diagram which shows the other structural example of the IC card which concerns on this embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Communication system, 110 ... IC card, 111 ... Antenna coil, 112 ... Capacitor, 113, 114, 115 ... Load resistance, 116 (SW1) ... Switch, 117 (SW2) ) ... switch, 118 ... control circuit, 119 ... antenna circuit, 120 ... mobile phone, 125 ... memory unit, 126 ... communication device, 127 ... control unit, 130. ..Base station, 140 ... communication network, 150 ... server, 200 ... communication device, 210 ... antenna circuit, 211 ... antenna coil, 212, 213 ... capacitor, 214 ... Switch, 220 ... Transmission system circuit, 230 ... Reception circuit, 240 ... Load modulation block (reply circuit), 241,242 ... Resistance, 243,244 ... Pitch.

Claims (9)

A communication device having a load modulation type data transmission function,
An antenna circuit including a resonant circuit;
A load element connected to the antenna circuit;
A plurality of modulation control load elements connected to the antenna circuit;
A control unit that optimizes a load modulation point by changing the number of load elements for modulation control connected to the antenna circuit when load modulation is on and when load modulation is off in a load modulation section; A first modulation control load element and a second modulation control load element,
The control unit
A first switch for selecting whether to contribute to load modulation by switching connection or non-connection of the first modulation control load element to the antenna circuit;
A second switch for selecting whether to contribute to load modulation by switching connection or non-connection of the first modulation control load element to the antenna circuit;
The communication apparatus according to claim 1, further comprising: a control circuit that controls on and off of the first switch and the second switch. The control unit
In the non-modulation period, the first switch and the second switch are controlled to be in an off state so that the load element is connected to the antenna circuit.
In the load modulation section, when the load modulation is on, the load element, the first modulation control load element, and the second modulation control load element are connected to the antenna circuit and contribute to the load modulation. Controlling the switch and the second switch to an on state;
In the load modulation section, when the load modulation is off, the load element and the second modulation control load element are connected to the antenna circuit and the first switch is turned off so as to contribute to load modulation. The communication device according to claim 2, wherein the switch is controlled to be in an on state. The control unit
In the non-modulation period, the first switch and the second switch so that the load element, the first modulation control load element, and the second modulation control load element are connected to the antenna circuit. Control to ON state,
In the load modulation section, when the load modulation is on, the load element is connected to the antenna circuit and the first switch and the second switch are controlled to be off so as to contribute to load modulation,
In the load modulation section, when the load modulation is off, the load element and the first modulation control load element are connected to the antenna circuit and the first switch is turned off so as to contribute to load modulation. The communication device according to claim 2, wherein the switch is controlled to be in an on state. An information device having an information processing function,
Including a communication device having a reader / writer function unit and a card function unit,
The communication device is
The antenna circuit including the resonance circuit is shared by the reader / writer function unit and the card function unit,
The card function section
A load element connected to the antenna circuit;
A plurality of modulation control load elements connected to the antenna circuit;
A control unit that optimizes a load modulation point by changing the number of load elements for modulation control connected to the antenna circuit when load modulation is on and when load modulation is off in a load modulation section; A first modulation control load element and a second modulation control load element,
The control unit
A first switch for selecting whether to contribute to load modulation by switching connection or non-connection of the first modulation control load element to the antenna circuit;
A second switch for selecting whether to contribute to load modulation by switching connection or non-connection of the first modulation control load element to the antenna circuit;
The information apparatus according to claim 5, further comprising: a control circuit that controls on and off of the first switch and the second switch. The control unit
In the non-modulation period, the first switch and the second switch are controlled to be in an off state so that the load element is connected to the antenna circuit.
In the load modulation section, when the load modulation is on, the load element, the first modulation control load element, and the second modulation control load element are connected to the antenna circuit and contribute to the load modulation. Controlling the switch and the second switch to an on state;
In the load modulation section, when the load modulation is off, the load element and the second modulation control load element are connected to the antenna circuit and the first switch is turned off so as to contribute to load modulation. The information device according to claim 6, wherein the switch is controlled to be in an on state. The control unit
In the non-modulation period, the first switch and the second switch so that the load element, the first modulation control load element, and the second modulation control load element are connected to the antenna circuit. Control to ON state,
In the load modulation section, when the load modulation is on, the load element is connected to the antenna circuit and the first switch and the second switch are controlled to be off so as to contribute to load modulation,
In the load modulation section, when the load modulation is off, the load element and the first modulation control load element are connected to the antenna circuit and the first switch is turned off so as to contribute to load modulation. The information device according to claim 6, wherein the switch is controlled to be in an on state. A load modulation communication method using a load element connected to an antenna circuit and a plurality of modulation control load elements connected to the antenna circuit,
A communication method for optimizing a load modulation point by changing the number of load elements for modulation control connected to the antenna circuit when load modulation is on and when load modulation is off in a load modulation section.

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