METHOD AND APPARATUS FOR VERIFYING RFID TAGS

• US 20020167397A1
• Filed: 07/08/1999
• Published: 11/14/2002
• Est. Priority Date: 07/08/1999
• Status: Active Grant

• Current Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Original Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Inventors: HELTON, PATRICK L., EROGLU, KURSAT, WIKLOF, CHRISTOPHER A.
• Granted Patent: US 6,784,789 B2
• Time in Patent Office: Days
• US Class Current: 340/10.6
• 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 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/0095 Testing the sensing arrangement, e.g. testing if a magnetic card reader, bar code reader, RFID interrogator or smart card reader functions properly testing of electrical circuits G01R31/28
• CPC Class Codes: G06K 7/10465 the interrogation device being capable of self-diagnosis, e.g. in addition to or as part of the actual interrogation process testing of electrical circuits in general G01R31/28

Abstract

An RFID tag verifier includes an RF interrogator that transmits a first and second interrogation signal each having a first operational characteristic that differs from the other by a known amount. The RF interrogator receives a first and second return signal corresponding to the respective interrogation signals. A processor determines a response of the RFID tag as defined by a second operational characteristic of the first and second return signals. The verifier can determine the signal strength of the return signal for varying strengths of the interrogation signal. Typically, a flat response is desired Additionally, or alternatively, the verifier can determine the response in terms of signal strength of the response signals for interrogation signals having different frequencies. In some applications frequency selectivity may be desirable. Additionally, or alternatively, the verifier can determine the response in terms of frequency for interrogation signals having varying strengths. A machine-readable symbol verifier can be coupled to, or formed as part of, the RFID verifier. A printer can be coupled to, or formed as part of, the RFID tag verifier.

Claims

1. An apparatus to verify RFID tags, comprising:

an RF transmitter configured to transmit at least a first RF interrogation signal of a first power level at a first time and a second RF interrogation signal of a second power level, different from the first power level, at a second time;

an RF receiver configured to receive a first RF return signal returned from an RFID tag in response to the first RF interrogation signal and a second RF return signal returned from the RFID tag in response to the second RF interrogation signal; and

a processor coupled to the RF receiver and configured to determine a response of the RFID tag as defined by at least the first RF return signal and the second RF return signal.

2. The apparatus of claim 1 wherein the processor includes a comparator to compare an operational characteristic of the first and the second return signals.

3. The apparatus of claim 1 wherein the processor is further configured to compare the determined response of the RFID tag to a predefined response.

4. The apparatus of claim 1 wherein the processor is further configured to compare the determined response of the RFID tag to a predefined response and to produce an output signal corresponding to a status of the RFID tag based on the comparison.

5. The apparatus of claim 1 wherein the processor compares a power level of the first RF return signal to a power level of the second RF return signal to determine the response of the RFID tag.

6. The apparatus of claim 1 wherein the processor compares a signal-to-noise ratio of the first RF return signal to a signal-to-noise ratio of the second RF return signal to determine the response of the RFID tag.

7. An apparatus to verify RFID tags, comprising:

an RF transmitter configured to transmit at least a first RF interrogation signal of a first frequency at a first time and a second RF interrogation signal of a frequency, different from the first frequency, at a second time;

an RF receiver configured to receive a first RF return signal returned from an RFID tag in response to the first RF interrogation signal and a second RF return signal returned from the RFID tag in response to the second RF interrogation signal; and

a processor coupled to the RF receiver and configured to determine a response of the RFID tag as defined by at least the first RF return signal and the second RF return signal.

8. The apparatus of claim 7 wherein the processor includes a comparator to compare an operational characteristic of the first and the second return signals.

9. The apparatus of claim 7 wherein the processor is further configured to compare the determined response of the RFID tag to a predefined response.

10. An apparatus to verify RFID tags, comprising:

a first antenna configured to transmit a first RF interrogation signal at a first time;

a second antenna spaced from the first antenna and configured to transmit a second RF interrogation signal at a second time;

an RF receiver configured to receive a first RF return signal returned from an RFID tag in response to the first RF interrogation signal and a second RF return signal returned from the RFID tag in response to the second RF interrogation signal; and

a processor coupled to the RF receiver and configured to determine a response of the RFID tag as defined by the first RF return signal and the second RF return signal.

11. The apparatus of claim 10 wherein the processor includes a comparator to compare an operational characteristic of the first and the second return signals.

12. The apparatus of claim 10 wherein the processor is further configured to compare the determined response of the RFID tag to a predefined response.

14. The apparatus of claim 13 wherein the processor includes a comparator to compare an operational characteristic of the first return signal as received at the first and the second antennas.

15. The apparatus of claim 13 wherein the processor is further configured to compare the determined response of the RFID tag to a predefined response.

17. The apparatus of claim 16 wherein the processor includes a comparator to compare an operational characteristic of the first and the second return signals.

18. The apparatus of claim 16 wherein the processor is configured to compare the operational response of the RFID tag to a predetermined response.

19. The apparatus of claim 16 wherein the first operational characteristic is signal strength and the second operational characteristic is signal strength.

20. The apparatus of claim 16 wherein the first operational characteristic is signal strength and the second operational characteristic is frequency.

21. The apparatus of claim 16 wherein the first operational characteristic is frequency and the second operational characteristic is signal strength.

22. The apparatus of claim 16 wherein the RF interrogator includes an RF transmitter and an RF receiver.

23. The apparatus of claim 16 wherein the RF interrogator includes an RF transceiver.

24. The apparatus of claim 16, further comprising:

a machine-readable symbol verifier positioned to verify a machine-readable symbol on the RFID tag.

25. The apparatus of claim 16, further comprising:

a machine-readable symbol imager positioned to image a machine-readable symbol on the RFID tag and coupled to the processor to supply the image data thereto, the processor being configured to verify the image data.

26. The apparatus of claim 16, further comprising:

a machine-readable symbol imager positioned to image a machine-readable symbol on the RFID tag and coupled to the processor to supply the image data thereto, the processor configured to verify the image data and to provide a grade based on the verification of the image data and the comparison of the response of the RFID tag to the predetermined response.

27. The apparatus of claim 16 wherein the processor is further configured to compare the determined operational response of the RFID tag to a predefined response and to produce a binary output signal corresponding to a status of the RFID tag based on the comparison.

28. The apparatus of claim 16 wherein the processor is further configured to compare the determined operational response of the RFID tag to a predefined response and to produce an output signal corresponding to a status of the RFID tag based on the comparison.

29. The apparatus of claim 16, further comp rising:

a printer couplable to the processor to print information corresponding to the operational response of the RFID tag.

30. The apparatus of claim 16, further comprising:

a printer positionable to write on the RFID tag and couplable to the processor to print information corresponding to the operational response of the RFID tag.

31. The apparatus of claim 16, further comprising:

a print head coupled to the processor to print information corresponding to the operational response of the RFID tag.

13. An apparatus to verify RFID tags, comprising:

an RF transmitter configured to transmit at least a first RF interrogation signal of a first power level at a first time;

a first antenna configured to receive a first RF response signal returned from an RFID tag in response to the first interrogation signal;

a second antenna spaced from the first antenna and configured to receive the first RF response signal returned from the RFID tag in response to the first interrogation signal; and

a processor coupled to the first and the second antennas and configured to determine a response of the RFID tag as defined by the first RF return signal as received at the first antenna and the first RF return signal as received at the second antenna.

16. An apparatus to verify RFID tags, comprising:

an RF interrogator configured to selectively transmit a first interrogation signal at a first time and a second interrogation signal at a second time, the first interrogation signal having a first operational characteristic that differs from a corresponding first operational characteristic of the second interrogation signal, and to receive a first return signal returned from an RFID tag in response to the first interrogation signal and a second return signal returned from the RFID tag in response to the second interrogation signal; and

a processor coupled to the RF interrogator and configured to determine an operational response of the RFID tag in the form of at least a second operational characteristic of the first and the second return signals.

32. A method to verify RFID tags, comprising:

selectively transmitting a first interrogation signal having a first operational characteristic;

selectively transmitting a second interrogation signal having a first operational characteristic that differs from the corresponding first operational characteristic of the first interrogation signal by a defined amount;

receiving a first return signal returned from an RFID tag in response to the first interrogation signal, the first return signal having a second operational characteristic;

receiving a second return signal returned from the RFID tag in response to the second interrogation signal, the second return signal having a second operational characteristic corresponding to the second operational characteristic of the first return signal; and

determining a response of the RFID tag corresponding to the second operational characteristic of at least the first and the second return signals.

33. The method of claim 32 wherein determining a response of the RFID tag includes comparing the second operational characteristics of the first and the second return signals.

34. The method of claim 32, further comprising

comparing the response of the RFID tag to a predetermined response.

35. The method of claim 32 wherein selectively transmitting a first interrogation signal having a first operational characteristic includes producing the first interrogation signal of a first signal strength, and wherein selectively transmitting a second interrogation signal having a first operational characteristic includes producing the second interrogation signal of a second signal strength that differs from the first signal strength.

36. The method of claim 32 wherein selectively transmitting a first interrogation signal having a first operational characteristic includes producing the first interrogation signal having a first frequency, and wherein selectively transmitting a second interrogation signal having a first operational characteristic includes producing the second interrogation signal having a second frequency that differs from the first frequency.

37. The method of claim 32 wherein receiving a first return signal having a second operational characteristic includes detecting the first return signal of a first signal strength, and wherein receiving a second return signal having a second operational characteristic includes detecting the second return signal of a second signal strength that differs from the first signal strength.

38. The method of claim 32 wherein receiving a first return signal having a second operational characteristic includes detecting the first return signal of a first frequency, and wherein receiving a second return signal having a second operational characteristic includes detecting the second return signal of a second frequency that differs from the first frequency.

39. The method of claim 32 wherein determining a response of the RFID tag corresponding to the second operational characteristic of at least the first and the second return signals includes determining a slope of a function including at least a first point corresponding to the first operational characteristic of first interrogation signal and the second operational characteristic of the first return signal, and a second point corresponding to the first operational characteristic of the second interrogation signal and the second operational characteristic of the second return signal.

40. A computer readable medium whose contents cause a first processor based system to:

transmit a first interrogation signal having a first operational characteristic;

transmit a second interrogation signal having a first operational characteristic that differs from the corresponding first operational characteristic of the first interrogation signal by a defined amount;

receive a first return signal returned from an RFID tag in response to the first interrogation signal, the first return signal having a second operational characteristic;

receive a second return signal returned from the RFID tag in response to the second interrogation signal, the second return signal having a second operational characteristic corresponding to the second operational characteristic of the first return signal; and

determine a response of the RFID tag corresponding to the second operational characteristic of at least the first and the second return signals.

41. The computer readable medium of claim 40 whose contents cause the first processor system to compare the second operational characteristics of the first and the second return signals when determining the response of the RFID tag.

42. The computer readable medium of claim 40 whose contents further cause the first processor system to:

compare the response of the RFID tag to a predetermined response.

43. A method to verify RFID tags, comprising:

transmitting at least two interrogation signals;

receiving a response from an RFID tag to each of the interrogation signals; and

comparing a change in the responses relative to a change in the interrogation signals.

44. The method of claim 43, further comprising:

accepting or rejecting the RFID tag based on the comparison.

45. The method of claim 43, further comprising:

printing on the RFID tag based on the comparison.

46. The method of claim 43, further comprising:

sorting the RFID tag based on the comparison.