System and method for killing a RFID tag

• US 7,474,211 B2
• Filed: 02/22/2005
• Issued: 01/06/2009
• Est. Priority Date: 02/22/2005
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Kramer, Bradley Allen
• Primary Examiner(s): Nguyen; Phung
• Application Number:
  US11/062,724
• Publication Number:
  US 20060187046A1
• Time in Patent Office: 1,414 Days
• Field of Search: 3405721-5728, 340/568.1, 340/10.1, 342/42
• US Class Current: 340/572.1
• 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 19/07345 by activating or deactivating at least a part of the circuit on the record carrier, e.g. ON/OFF switches

Abstract

System and method for disabling a RFID tag. A preferred embodiment comprises attenuating a signal received at an antenna of the RFID tag based upon a status of the RFID tag and responding to an instruction in the received signal if the attenuated signal is detectable. The attenuation of the received signal requires that the received signal have a signal strength greater than a specified threshold in order for the instruction in the received signal to be detectable. This means that for a given signal transmit power, the RFID tag must be within a certain distance from a RFID reader attempting to retrieve information from the RFID tag. By setting the attenuation amount at a sufficiently high level, the method ensures that the RFID reader must be substantially adjacent to the RFID tag, preventing the unintended retrieval of unique identification information by RFID readers remotely located from the RFID tag.

Claims

1. A method for using a radio-frequency identification (RFID) tag, the method comprising:

attenuating a signal received at an antenna of the RFID tag in receiver circuitry of the RFID tag based upon a status of the RFID tag; and

responding to an instruction in the received signal if the attenuated signal is detectable.

2. The method of claim 1, wherein the attenuating is performed on an analog signal, wherein an attenuator attenuates the analog signal by a specified amount, and wherein the specified amount is a non-zero amount if the status is disabled.

3. The method of claim 2, wherein the attenuation by the specified amount ensures that only received signals transmitted at a power level from a transmitter less than a specified distance away from the antenna of the RFID tag is detectable.

4. The method of claim 1, wherein the attenuation is performed on a digital signal, and the method further comprising digitizing the signal received signal prior to the attenuating.

5. The method of claim 4, wherein the attenuating comprises shifting the digitized received signal by a specified number of bits, and wherein the specified number of bits is non-zero if the status is disabled.

6. The method of claim 1, wherein the attenuating is substantially equal to zero if the status is not disabled.

7. The method of claim 6, wherein a memory location stores a value indicating the status of the RFID tag.

8. A method for using a disabled radio-frequency identification (RFID) tag, the method comprising:

providing an RFID tag disabled by attenuating a received signal;

measuring a signal strength of a the received signal in receiver circuitry of the RFID tag;

responding to an instruction in the received signal if the signal strength exceeds a specified threshold; and

responding to the instruction if the signal strength does not exceed the specified threshold but the instruction meets a specified criterion.

9. The method of claim 8, wherein the specified criteria is a class of instructions that do not require the RFID tag to provide unique identifying information.

10. The method of claim 9, wherein the specified criterion further does not require the RFID tag to modify internally stored values.

11. The method of claim 8 further comprising classifying the received signal based on the signal strength.

12. The method of claim 11, wherein the specified criterion differs based upon the classification of the received signal.

13. A radio-frequency identification (RFID) tag comprising:

a radio frequency (RF) unit coupled to an antenna, the RF unit is configured to perform analog signal processing on a signal provided by the antenna, the RF unit comprising

a RF circuitry unit configured to amplify, detect and filter the signal;

a signal processor coupled to the RF circuitry unit, the signal processor is configured to manipulate the signal;

a processor coupled to the RF unit, the processor is configured to respond to instructions carried in the signal; and

a memory coupled to the processor, the memory to store data and instructions wherein the operation of the signal processor is controlled by a value stored in a memory location the value stored in the memory location indicates if the RFID tag is disabled, and wherein if the RFID tag is not disabled, then the signal processor does not attenuate the received signal.

14. The RFID tag of claim 13 further comprising a rectifier coupled to the antenna, the rectifier is configured to derive power for the RFID tag from the signal provided by the antenna.

15. The RFID tag of claim 13, wherein the signal processor is an analog signal attenuator.

16. The RFID tag of claim 13, wherein the signal processor operates on a digital representation of the signal, and wherein the digitized signal is shifted by a specified number of bits.

17. The RED tag of claim 16, wherein the RF unit further comprises an analog-to-digital converter (ADC) coupled in between the RF circuitry unit and the signal processor, the ADC is configured to provide a digital representation of an analog signal.

18. The RFID tag of claim 13, wherein the signal processor is a signal strength meter that is configured to provide a measure of the signal strength of the signal.

19. The RFID tag of claim 18, wherein the processor makes use of the measure of the signal strength to determine if it will respond to instructions carried in the signal.