Radio Tag and Radio Tag Communication Distance Modification Method

• US 20070229278A1
• Filed: 06/10/2005
• Published: 10/04/2007
• Est. Priority Date: 06/10/2004
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Niimi, Hiroaki, Tagiri, Satoshi, Usuki, Izumi, Nagata, Minehisa, Kuhara, Shunsuke, Kemi, Shinya
• Granted Patent: US 7,834,743 B2
• Time in Patent Office: Days
• US Class Current: 340/572.700
• 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 19/073 Special arrangements for circuits, e.g. for protecting identification code in memory protection against unauthorised use of computer memory G06F12/14
• CPC Class Codes: G06K 19/07345 by activating or deactivating at least a part of the circuit on the record carrier, e.g. ON/OFF switches
• CPC Class Codes: G06K 19/07756 the connection being non-galvanic, e.g. capacitive
• CPC Class Codes: G06K 19/07767 the first and second communication means being two different antennas types, e.g. dipole and coil type, or two antennas of the same kind but operating at different frequencies

Abstract

It is possible to prevent an unauthorized read-out from both active tags and passive tags. Antenna emission is turned on and off by using a switch, or attenuated by using a resistor. A part of the antenna may be chipped. With these configurations, it is possible to lower the emission level of the antenna thus preventing an unauthorized read-out of important information from a remote reader.

Claims

1. An RFID tag that stores data, comprising:

a first antenna for transmitting radio waves,

transmission means for generating a transmission signal by modulating the data, and providing the transmission signal to the first antenna; and

emission control means for controlling an output power of the first antenna in order to transmit the transmission signal, the emission control means being connected to the first antenna and the transmission means.

2. The RFID tag according to claim 1, wherein the emission control means has:

attenuation means for attenuating the output power of the first antenna; and

attenuation control means for controlling attenuation of the output power by the attenuation means.

3. The RFID tag according to claim 2, wherein the attenuation means includes a plurality of resistors, and

the attenuation control means connects the transmission means and the first antenna via at least one of the plurality of resistors.

4. The RFID tag according to claim 2, wherein the attenuation means includes a variable resistor connected between the transmission means and the first antenna, and

the attenuation control means adjusts a resistance value of the variable resistor.

5. The RFID tag according to claim 1, wherein the emission control means has connection control means for disconnecting a connection between the first antenna and the transmission means.

6. The RFID tag according to claim 5, wherein the connection control means includes switching means for switching the connection between the transmission means and the first antenna ON and OFF.

7. The RFID tag according to claim 5, further comprising a second antenna for transmitting radio waves at an output power different from the output power of the first antenna, the second antenna being connected to the transmission means via the emission control means.

8. The RFID tag according to claim 1 further comprising determination means for determining a value of the output power of the first antenna,

wherein the emission control means controls the output power of the first antenna based on the value determined by the determination means.

9. The RFID tag according to claim 8 further comprising storage means for storing values of output power of the first antenna,

wherein the determination means determines the output power based on the values stored in the storage means.

10. The RFID tag according to claim 8 further comprising authentication means for authenticating an external device to which the radio waves from the first antenna are transmitted,

wherein the determination means determines the value of the output power according to an authentication result determined by the authentication means.

11. The RFID tag according to claim 8 wherein the determination means determines the value of the output power according to an attribute of the data.

12. The RFID tag according to claim 8 wherein the first antenna further receives radio waves,

the RFID tag further comprising receiving means for obtaining received data by demodulating the radio waves received by the first antenna, and

wherein the determination means determines the value of the output power based on the received data.

13. The RFID tag according to claim 8 further comprising setting-receiving means for receiving settings of the values of the output power from the external device;

wherein the determination means determines the value of the output power based on the received settings of the values.

14. The RFID tag according to claim 6, further comprising a second antenna for transmitting radio waves at an output power different from the output power of the first antenna, the second antenna being connected to the transmission means via the emission control means.