System and method for detecting EAS/RFID tags using step listen

• US 7,148,804 B2
• Filed: 01/26/2005
• Issued: 12/12/2006
• Est. Priority Date: 11/08/2004
• Status: Expired due to Fees

• Current Assignee: CHECKPOINT SYSTEMS, INC. (CCL Industries Incorporated)
• Original Assignee: CHECKPOINT SYSTEMS, INC. (CCL Industries Incorporated)
• Inventors: Shah, Nimesh, Salesky, Ronald, Paranzino, John
• Primary Examiner(s): TRIEU, VAN THANH
• Application Number:
  US11/043,501
• Publication Number:
  US 20060097874A1
• Time in Patent Office: 685 Days
• Field of Search: 340/572.1, 340/572.2, 340/572.4, 340/572.7, 340/568.1, 340/10.1, 340/10.3, 340/10.4, 340/10.41, 340/10.51, 340/10.52, 342/429, 342/445, 455/108
• US Class Current: 340/572.4
• CPC Class Codes: G08B 13/2417 having a radio frequency identification chip
• CPC Class Codes: G08B 13/2448 Tag with at least dual detection means, e.g. combined inductive and ferromagnetic tags, dual frequencies within a single technology, tampering detection or signalling means on the tag
• CPC Class Codes: G08B 13/2471 Antenna signal processing by receiver or emitter

Abstract

A system and method for the real-time concurrent detection of 13.56 MHz RFID and 8.2 MHz EAS identification tags using a single stimulus signal.

Claims

1. A system for detecting a first signal from an electronic article surveillance (EAS) resonant circuit tag that is tuned to a frequency in an EAS frequency band and a second signal from a radio frequency identification (RFID) tag that is tuned to a frequency in an RFID frequency band, said system comprising:

a transmitter for emitting said transmit signal, said transmit signal comprising a carrier signal of a frequency in said RFID frequency band and that is amplitude modulated for sending commands to the RFID tag, said transmit signal comprising modulation edges that cause said EAS tag to emit said first signal when said transmit signal impinges on said EAS resonant circuit tag;

a first receiver, tuned to a frequency in said EAS frequency band, for receiving said first signal, said first signal comprising the natural response of said EAS resonant circuit; and

a second receiver, tuned to a frequency in said RFID frequency band, for receiving said second signal.

2. The system of claim 1 wherein said transmitter and said second receiver comprise an RFID reader.

3. The system of claim 2 wherein said transmitter and said second receiver share a second antenna for transmitting said transmit signal and for receiving said second signal.

4. The system of claim 3 wherein said first receiver comprises a first antenna different from said second antenna.

5. The system of claim 4 wherein said first antenna comprises a plurality of loops.

6. The system of claim 5 wherein said plurality of loops comprises five loops.

7. The system of claim 4 wherein said transmitter, said first receiver and said second receiver are contained within a single housing.

8. The system of claim 7 wherein said single housing is contained within one pedestal of a pair of pedestals at the entrance of a business.

9. The system of claim 4 wherein said transmitter, said first receiver and said second receiver are contained within one pedestal of a pair of pedestals at the entrance of a business.

10. The system of claim 3 wherein said EAS frequency band comprises the range of frequencies 7.4 MHz to 8.7 MHz.

11. The system of claim 10 wherein said frequency in said EAS frequency band is approximately 8.2 MHz.

12. The system of claim 3 wherein said frequency in said RFID frequency band is 13.56 MHz.

13. The system of claim 2 wherein said first receiver also uses said second antenna for receiving said first signal.

14. The system of claim 13 wherein said common antenna comprises a Q of approximately 6.4.

15. The system of claim 14 wherein said common antenna comprises a differential L-type network.

16. The system of claim 15 wherein said common antenna further comprises a balun for converting the differential impedance into a single-ended load.

17. The system of claim 14 wherein said antenna comprises a switched Q circuit.

18. The system of claim 13 wherein said first receiver comprises a receiver path and wherein said receiver path comprises at least one active filter to filter out said transmit signal.

19. The system of claim 13 wherein said first receiver comprises a receiver path and wherein said receiver path comprises series resonant circuits to filter out said transmit signal.

20. The system of claim 1 wherein said transmitter is configured for a modulation index of approximately 10%.

21. The system of claim 1 wherein the output power of said transmitter is 3.75 watts.

22. The system of claim 1 wherein said modulation edge comprises a falling modulation edge.

23. The system of claim 22 wherein said transmit signal further comprises a first unmodulated component, said falling modulation edge component, a modulated component, a rising modulation edge component and a second unmodulated component.

24. The system of claim 23 wherein said transmit signal comprises a frequency of 13.56 MHz.

25. The system of claim 24 wherein said falling modulation edge comprises a sharp decrease in the amplitude between said first unmodulated component and said modulated component.

26. The system of claim 24 wherein said rising modulation edge comprises a sharp increase in the amplitude between said modulated component and said second unmodulated component.

27. The system of claim 24 wherein said transmitter is configured for a modulation index of approximately 10%.

28. A method for concurrently detecting a first signal from an electronic article surveillance (EAS) resonant circuit tag that is tuned to a frequency in an EAS frequency band and a second signal from a radio frequency identification (RFID) tag that is tuned to a frequency in an RFID frequency band, said method comprising the steps of:

(a) amplitude modulating a carrier signal having a frequency in said RFID frequency band to form said transmit signal, said transmit signal comprising modulation edges;

(b) emitting said transmit signal to impinge on said EAS resonant circuit tag and on said RFID tag;

(c) emitting said first signal by said EAS resonant circuit tag in response to said modulation edges of said transmit signal, said first signal comprising the natural response of said resonant circuit in said EAS resonant circuit tag;

(d) emitting said second signal by said RFID tag in response to said transmit signal; and

(e) detecting said first and second signals.

29. The method of claim 28 wherein said step of detecting said first and second signals comprises using respective antennae to receive said first and second signals.

30. The method of claim 29 wherein said step of detecting said first and second signals comprises actively filtering said received first signal by said respective antenna.

31. The method of claim 30 wherein said step of detecting said first and second signals comprises switching Q resistors in said respective antenna.

32. The method of claim 28 wherein said EAS frequency band comprises the range of frequencies 7.4 MHz to 8.7 MHz.

33. The method of claim 32 wherein said frequency in said EAS frequency band is approximately 8.2 MHz.

34. The method of claim 28 wherein said frequency in said RFID frequency band is 13.56 MHz.

35. The method of claim 28 wherein said step of amplitude modulating said carrier signal comprises implementing a modulation index of approximately 10%.

36. The method of claim 28 wherein said step of emitting said transmit signal comprises emitting said transmit signal with an output power of approximately 3.75 watts.

37. The method of claim 28 wherein said step of amplitude modulating a carrier signal comprises

providing a continuous carrier signal that is unmodulated;

amplitude modulating said continuous carrier signal to form an amplitude modulated carrier signal and wherein a sharp decrease in amplitude is generated when said amplitude modulation begins and forming one of said modulation edges; and

deactivating said amplitude modulation to generate said unmodulated carrier signal and wherein another modulation edge is formed when said deactivation occurs.

38. The method of claim 37 wherein said step of deactivating said amplitude modulation further comprises creating a sharp increase in amplitude to form said another modulation edge.

39. The method of claim 37 wherein said continuous carrier signal comprises a 13.56 MHz signal.

40. The method of claim 39 wherein said amplitude modulation comprises a modulation index of approximately 10%.

41. A method for concurrently detecting a first signal from an electronic article surveillance (EAS) resonant circuit tag that is tuned to a frequency in an EAS frequency band and a second signal from a radio frequency identification (RFID) tag that is tuned to a frequency in an RFID frequency band, said method comprising the steps of:

(a) generating a transmit signal having the following characteristics;

a first oscillating signal component having a first amplitude, a second oscillating signal component having a second amplitude less than said first amplitude and wherein there is a sharp decrease between said first amplitude and said second amplitude and a third oscillating signal component having said first amplitude and wherein there is a sharp increase between said second amplitude and said first amplitude of said third oscillating signal;

(b) emitting said transmit signal to impinge on said EAS resonant circuit tag and on said RFID tag;

(c) emitting said first signal by said EAS resonant circuit tag in response to said sharp decrease of said transmit signal, said first signal comprising the natural response of said resonant circuit in said EAS resonant circuit tag;

(d) emitting said second signal by said RFID tag in response to said transmit signal; and

(e) detecting said first and second signals.

42. The method of claim 41 wherein said first oscillating signal, said second oscillating signal and said third oscillating signal comprise a frequency of 13.56 MHz.

43. The system of claim 42 wherein said transmitter is configured for a modulation index of approximately 10%.