RFID tag

Abstract

An RFID tag includes an external power input unit, first antenna unit, first power supply unit, memory unit, and control unit. The external power input unit inputs external power. The first antenna unit receives power from a communication device. The first power supply unit extracts power from the radio wave received by the first antenna unit. The control unit operates upon receiving power from the first power supply unit and controls permission and inhibition of access from the communication device to the memory unit in accordance with presence/absence of input of power from the external power input unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the schematic arrangement of an RFID tag according to the first embodiment of the present invention;

FIG. 2 is a block diagram showing the arrangement of the control unit of the RFID tag according to the first embodiment;

FIG. 3 is a flowchart for explaining the access inhibition/permission function of the control unit of the RFID tag according to the first embodiment;

FIG. 4 is a view for explaining the operation of the RFID tag in a case wherein an RFID reader/writer is located at a long distance from the RFID tag;

FIG. 5 is a view for explaining the operation of the RFID tag in a case wherein the RFID reader/writer is located at a short distance from the RFID tag;

FIG. 6 is a block diagram showing the second embodiment as a modification of the first embodiment;

FIG. 7 is a view showing how an RFID tag according to the second embodiment is used;

FIG. 8 is a block diagram showing the schematic arrangement of an RFID tag according to the third embodiment of the present invention;

FIG. 9 is a block diagram showing the arrangement of the control unit of the RFID tag according to the third embodiment;

FIG. 10 is a flowchart for explaining the access inhibition/permission function of the control unit of the RFID tag according to the third embodiment;

FIG. 11 is a view for explaining the operation of the RFID tag in a case wherein an RFID reader/writer is located at a long distance from the RFID tag;

FIG. 12 is a view for explaining the operation of the RFID tag in a case wherein the RFID reader/writer is located at a short distance from the RFID tag;

FIG. 13 is a block diagram showing the fourth embodiment as a modification of the third embodiment;

FIG. 14 is a block diagram showing the schematic arrangement of an RFID tag according to the fifth embodiment of the present invention;

FIG. 15 is a view showing the relationship between the respective addresses in a data memory unit and the flag values in a flag memory unit in an RFID tag according to the fifth embodiment;

FIG. 16 is a block diagram showing the arrangement of the control unit of the RFID tag according to the fifth embodiment;

FIG. 17 is a flowchart for explaining the access inhibition/permission function of the control unit of the RFID according to the fifth embodiment;

FIG. 18 is a view for explaining the operation of the RFID tag in a case wherein an RFID reader/writer is located at a long distance from the RFID tag;

FIG. 19 is a view for explaining the operation of the RFID tag in a case wherein the RFID reader/writer is located at a short distance from the RFID tag;

FIG. 20 is a block diagram showing the sixth embodiment as a modification of the fifth embodiment;

FIG. 21 is a block diagram showing the schematic arrangement of an RFID tag according to the seventh embodiment of the present invention;

FIG. 22 is a block diagram showing the arrangement of a control unit for the RFID tag according to the seventh embodiment;

FIG. 23 is a flowchart for explaining the access inhibition/permission function of the control unit according to the seventh embodiment;

FIG. 24 is a view for explaining the operation of an RFID tag in a case wherein an RFID reader/writer is located at a long distance from the RFID tag;

FIG. 25 is a view for explaining the operation of the RFID tag in a case wherein the RFID reader/writer is located at a short distance from the RFID tag;

FIG. 26 is a block diagram showing the eighth embodiment as a modification of the seventh embodiment;

FIG. 27 is a view showing how an RFID tag according to the eighth embodiment is used;

FIG. 28 is a block diagram showing the schematic arrangement of an RFID tag according to the ninth embodiment of the present invention; and

FIG. 29 is a view showing how the RFID tag according to the ninth embodiment is used.

Claims

1. An RFID tag characterized by comprising: an external power input unit which inputs external power;a first antenna unit which receives power from a communication device;a first power supply unit which extracts power from the radio wave received by said first antenna unit;

2. A tag according to claim 1, wherein said external power input unit inputs external power from a short distance shorter than a radio wave communicable distance of said first antenna unit.

3. A tag according to claim 1, wherein said external power input unit comprisesa second antenna unit which has radio wave reception sensitivity lower than that of said first antenna unit, anda second power supply unit which extracts power from the radio wave received by the second antenna unit.

4. A tag according to claim 3, wherein said control unit comprisesan access inhibition unit which inhibits access from the communication device to said memory unit through said first antenna unit if no power is received from the second power supply unit, andan access permission unit which permits access from the communication device to said memory unit through said first antenna unit if power is received from the second power supply unit.

5. A tag according to claim 3, wherein said memory unit comprises a protected memory unit which stores data needing protection, and an unprotected memory unit which stores data needing no protection, and said control unit comprises an access inhibition unit which inhibits access from the communication device to the protected memory unit if no power is received from the second power supply unit, and an access permission unit which permits access from the communication device to the protected memory unit through said first antenna unit if power is received from the second power supply unit.

6. A tag according to claim 3, wherein said memory unit comprises a data memory unit which stores data, and a flag memory unit which stores a flag value indicating whether data stored at the addresses in the data memory unit need protection, andsaid control unit comprises an access inhibition unit which inhibits access from the communication device to a data storage area in the data memory unit which is in protected state by a flag value in the flag memory unit through said first antenna unit if no power is received from the second power supply unit, and an access permission unit which permits access from the communication device to a data storage area in the data memory unit which is in protected state by a flag value in the flag memory unit through said first antenna unit if power is received from the second power supply unit.

7. A tag according to claim 3, wherein said memory unit comprises a data memory unit which stores data, and a flag memory unit which stores a flag value indicating whether data stored at the addresses in the data memory unit need protection, andsaid control unit comprises an access inhibition unit which inhibits access from the communication device to the flag memory unit through said first antenna unit if no power is received from the second power supply unit, and an access permission unit which permits access from the communication device to the flag memory unit through said antenna unit if power is received from the second power supply unit.

8. A tag according to claim 3, wherein said memory unit comprises a protected memory unit which stores data needing protection, and an unprotected memory unit which stores data needing no protection, andsaid control unit comprises an access inhibition unit which inhibits access from the communication device to the protected memory unit through said first antenna unit if no power is received from the second power supply unit, and an access permission unit which permits access from the communication device to the protected memory unit through the second antenna unit if power is received from the second power supply unit.

9. A tag according to claim 3, wherein said memory unit comprises a data memory unit which stores data, and a flag memory unit which stores a flag value indicating whether data stored at the addresses in the data memory unit need protection, andsaid control unit comprises an access inhibition unit which inhibits access from the communication device to a data storage area in the data memory unit which is in protected state by a flag value in the flag memory unit through said first antenna unit if no power is received from the second power supply unit, and an access permission unit which permits access from the communication device to a data storage area in the data memory unit which is in protected state by a flag value in the flag memory unit through the second antenna unit.

10. A tag according to claim 3, wherein said first antenna unit and the second antenna unit use different frequency bands for communication.

11. A tag according to claim 10, wherein the second antenna unit receives a radio wave from a radio wave source different from the communication device.

12. A tag according to claim 1, wherein the external power input unit comprises a connection terminal to an external power supply.

13. A tag according to claim 12, wherein said control unit comprisesan access inhibition unit which inhibits access from the communication device to said memory unit through said first antenna unit if the external power supply does not connect to the connection terminal, andan access permission unit which permits access from the communication device to said memory unit through said first antenna unit if the external power supply connects to the connection terminal.

14. A tag according to claim 12, wherein said memory unit comprises a protected memory unit which stores data needing protection, and an unprotected memory unit which stores data needing no protection, andsaid control unit comprises an access inhibition unit which inhibits access from the communication device to the protected memory unit through said first antenna unit if the external power supply does not connect to the connection terminal, and an access permission unit which permits access from the communication device to the protected memory unit through said first antenna unit if the external power supply connects to the connection terminal.

15. A tag according to claim 12, wherein said memory unit comprises a data memory unit which stores data, and a flag memory unit which stores a flag value indicating whether data stored at the addresses in the data memory unit need protection, andsaid control unit comprises an access inhibition unit which inhibits access from the communication device to a data storage area in the data memory unit which is in protected state by a flag value in the flag memory unit through said first antenna unit if the external power supply does not connect to the connection terminal, and an access permission unit which permits access from the communication device to a data storage area in the data memory unit which is in protected state by a flag value in the flag memory unit through said first antenna unit if the external power supply connects to the connection terminal.

16. A tag according to claim 12, wherein said memory unit comprises a data memory unit which stores data, and a flag memory unit which stores a flag value indicating whether data stored at the addresses in the data memory unit need protection, andsaid control unit comprises an access inhibition unit which inhibits access from the communication device to the flag memory unit through said first antenna unit if the external power supply does not connect to the connection terminal, and an access permission unit which permits access from the communication device to the flag memory unit through said first antenna unit if the external power supply connects to the connection terminal.