Noncontact communication medium and noncontact communication system

• US 6,952,167 B2
• Filed: 06/11/2001
• Issued: 10/04/2005
• Est. Priority Date: 08/15/2000
• Status: Expired due to Fees

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Wakabayashi, Naoyuki
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): PHAM, LAM P
• Application Number:
  US10/344,375
• Publication Number:
  US 20030178483A1
• Time in Patent Office: 1,576 Days
• Field of Search: 3403101-3104, 340571-572, 340/572.5, 340/825.54, 340/825.49, 235/439, 235/449, 235/451, 235/491, 235/492
• US Class Current: 340/572.5
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• CPC Class Codes: G06K 19/0715 the arrangement including means to regulate power transfer to the integrated circuit
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 19/0775 arrangements for connecting the integrated circuit to the antenna
• CPC Class Codes: G06K 19/07796 arrangements on the record carrier to allow stacking of a plurality of similar record carriers, e.g. to avoid interference between the non-contact communication of the plurality of record carriers

Abstract

An output of a resonant circuit 60 which electromagnetically couples with an external communications apparatus is rectified and taken out, and a resultant output voltage V is monitored by a switch control circuit 61. After the output voltage V has risen to or beyond a threshold Vth1, a switch element SW is turned on and off, and a state of the switch element SW in which the output voltage V becomes higher is determined. While holding the switch element SW in the state thus determined, a power supply switch element PSW is turned on when the output voltage V has further risen. As a result, even when a plurality of noncontact IC cards 6 overlaid with one another are brought close to the communications apparatus, the individual noncontact IC cards 6 can carry out data communication.

Claims

1. A noncontact communications medium comprising:

a resonant circuit including;

an antenna coil which generates an induced electromotive force by receiving electromagnetic waves carrying information as a result of changes in the amount of electric power and thereby transmits and receives signals;

two capacitors parallel-connected to the antenna coil;

a main circuit which processes a received signal obtained by demodulating an output of said resonant circuit and outputs a modulated transmitting signal to said resonant circuit;

a switch section which switches first one of said two capacitors between a connected state and a disconnected state; and

a switch control section which controls switching operation of said switch section according to the amount of an output voltage occurring in said resonant circuit and according to a specific change in said output voltage, wherein said switch control section controls the switching operation of said switch section according to a change in a rising edge of said output voltage when the output voltage occurring in said resonant circuit is equal to or higher than a specific value.

2. A noncontact communications medium comprising:

a resonant circuit including;

an antenna coil which generates an induced electromotive force by receiving electromagnetic waves carrying information as a result of changes in the amount of electric power and thereby transmits and receives signals; and

two capacitors parallel-connected to the antenna coil;

a main circuit which processes a received signal obtained by demodulating an output of said resonant circuit and outputs a modulated transmitting signal to said resonant circuit;

a switch section which switches first one of said two capacitors between a connected state and a disconnected state; and

a switch control section which controls switching operation of said switch section according to the amount of an output voltage occurring in said resonant circuit and according to a specific change in said output voltage, wherein said switch control section controls the switching operation of said switch section according to a change in a falling edge of said output voltage when the output voltage occurring in said resonant circuit is equal to or higher than a specific value.

3. A noncontact communications medium comprising:

a resonant circuit including;

an antenna coil which generates art induced electromotive force by receiving electromagnetic waves carrying information as a result of changes in the amount of electric power and thereby transmits and receives signals;

two capacitors parallel-connected to the antenna coil;

a main circuit which processes a received signal obtained by demodulating an output of said resonant circuit and outputs a modulated transmitting signal to said resonant circuit;

a switch section which switches first one of said two capacitors between a connected state and a disconnected state; and

a switch control section which controls switching operation of said switch

section according to the amount of an output voltage occurring in said resonant

circuit and according to a specific change in said output voltage, wherein the capacitance of the second capacitor is such that, when the noncontact communications medium is overlaid with another one with said first capacitor in the disconnected state in each noncontact communications medium, the frequency of said electromagnetic waves and the resonant frequency of the two noncontact communications media approximately march each ocher.

4. A noncontact communications medium comprising:

a resonant circuit including;

an antenna coil which generates an induced electromotive force by receiving electromagnetic waves carrying information as a result of changes in the amount of electric power and thereby transmits and receives signals; and

two capacitors parallel-connected to the antenna coil;

a main circuit which processes a received signal obtained by demodulating an output of said resonant circuit and outputs a modulated transmitting signal to said resonant circuit;

a switch section which switches first one of said two capacitors between a connected state and a disconnected state; and

a switch control section which controls switching operation of said switch section according to the amount of an output voltage occurring in said resonant circuit and according to a specific change in said output voltage;

wherein the capacitance of the second capacitor is such that, when the noncontact communications medium is overlaid with another one with said first capacitor in the disconnected state in each noncontact communications medium, the frequency of said electromagnetic waves and the resonant frequency of the two noncontact communications media approximately match each other; and

wherein the capacitances of said two capacitors are such that, when said first capacitor is in the connected state, the frequency of said electromagnetic waves and the resonant frequency of said resonant circuit approximately march each other.

5. A noncontact communications medium comprising:

a resonant circuit including;

an antenna coil which generates an induced electromotive force by receiving electromagnetic waves carrying information as a result of changes in the amount of electric power and thereby transmits and receives signals; and

two capacitors parallel-connected to the antenna coil;

a main circuit which processes a received signal obtained by demodulating an output of said resonant circuit and outputs a modulated transmitting signal to said resonant circuit;

a switch section which switches first one of said two capacitors between a connected state and a disconnected state; and

a switch control section which controls switching operation of said switch section according to the amount of an output voltage occurring in said resonant circuit and according to a specific change in said output voltage;

wherein the capacitance of the second capacitor is such that, when the noncontact communications medium is overlaid with another one with said first capacitor in the disconnected state in each noncontact communications medium, the resonant frequency of the two noncontact communications media becomes higher than the frequency of said electromagnetic waves.

6. A noncontact communications medium comprising:

a resonant circuit including;

an antenna coil which generates an induced electromotive force by receiving electromagnetic waves carrying information as a result of changes in the amount of electric power and thereby transmits and receives signals;

two capacitors parallel-connected to the antenna coil;

a main circuit which processes a received signal obtained by demodulating an output of said resonant circuit and outputs a modulated transmitting signal to said resonant circuit;

a switch section which switches first one of said two capacitors between a connected state and a disconnected state;

a switch control section which controls switching operation of said switch section according to the amount of an output voltage occurring in said resonant circuit and according to a specific change in said output voltage;

wherein the capacitance of the second capacitor is such that, when the noncontact communications medium is overlaid with another one with said first capacitor in the disconnected state in each noncontact communications medium, the resonant frequency of the two noncontact communications media becomes higher than the frequency of said electromagnetic waves; and

wherein the capacitances of said two capacitors are such that, when said first capacitor is in the connected state, the frequency of said electromagnetic waves and the resonant frequency of said resonant circuit approximately match each other.

7. A noncontact communications system comprising:

a noncontact communications medium which comprises;

a resonant circuit including;

an antenna coil which generates an induced electromotive force by receiving electromagnetic waves carrying information as a result of changes in the amount of electric power and thereby transmits and receives signals; and

two capacitors parallel-connected to the antenna coil;

a main circuit which processes a received signal obtained by demodulating an output of said resonant circuit and outputs a modulated transmitting signal to said resonant circuit;

a switch section which switches first one of said two capacitors between a connected state and a disconnected state; and

a switch control section which controls switching operation of said switch section according to the amount of an output voltage occurring in said resonant circuit and according to a specific change in said output voltage;

wherein said switch control section controls the switching operation of said switch section according to a change in a rising edge or in a falling edge of said output voltage when the output voltage occurring in said resonant circuit is equal to or higher than a specific value; and

a communications apparatus which communicates with said noncontact communications medium by radio.

8. A noncontact communications medium comprising:

a resonant circuit including;

an antenna coil which generates an induced electromotive force by receiving electromagnetic waves carrying information as a result of changes in the amount of electric power and thereby transmits and receives signals; and

two capacitors parallel-connected to the antenna coil;

a main circuit which processes a received signal obtained by demodulating an output of said resonant circuit and outputs a modulated transmitting signal to said resonant circuit;

a switch section which switches first one of said two capacitors between a connected state and a disconnected state;

an end-of-polling command transmission detecting means which detects an end of transmission of a polling command occurring at a communicating station with which said noncontact communications medium communicates; and

a switch control section which begins control operation for switching said switch section at the timing of detecting the end of transmission of the polling command if said end-of-polling command transmission detecting means detects the end of transmission of the polling command occurring at the communicating station when an output voltage occurring in said resonant circuit is equal to or higher than a specific value.

9. The noncontact communications medium as recited in claim 8, wherein said switch control section judges when performing the control operation for switching said switch section whether the output voltage occurring in said resonant circuit becomes higher when said first capacitor is set in the connected state or in the disconnected state, and holds said switch section in the state in which said output voltage becomes higher.

10. The noncontact communications medium as recited in claim 9, wherein said switch control section causes said main circuit to operate after holding said switch section in the state in which said output voltage becomes higher.

11. The noncontact communications medium as recited in claim 9, wherein said switch control section begins to supply an operating power source to said main circuit after the amount of said output voltage has reached a level sufficient for operating said main circuit with said switch section held in the state in which said output voltage becomes higher.