RF tagging system and RF tags and method

• US 5,381,137 A
• Filed: 10/26/1992
• Issued: 01/10/1995
• Est. Priority Date: 10/26/1992
• Status: Expired due to Term

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Ghaem, Sanjar, Lauro, George L., Istvan, Rudyard L.
• Primary Examiner(s): SWANN III, GLEN R
• Application Number:
  US07/966,653
• Time in Patent Office: 806 Days
• Field of Search: 340/572, 29/847, 29/846, 336/200
• US Class Current: 340/572.5
• CPC Class Codes: G08B 13/2414 using inductive tags
• CPC Class Codes: G08B 13/2417 having a radio frequency identification chip
• CPC Class Codes: G08B 13/2462 Asset location systems combined with EAS inventory, tracking, logistic G06Q10/00; entrance control systems G07C9/00
• CPC Class Codes: G08B 13/2482 EAS methods, e.g. description of flow chart of the detection procedure
• CPC Class Codes: G08B 13/2485 Simultaneous detection of multiple EAS tags
• CPC Class Codes: Y10T 29/49155 Manufacturing circuit on or in base
• CPC Class Codes: Y10T 29/49156 with selective destruction of conductive paths

Abstract

RF tagging system (10) has a plurality of resonant circuits (13) on a tag (12). When the tag (12) enters a detection zone (14), the system determines the resonant frequency of each of the resonant circuits (13) and produces a corresponding code. Preferably, resonant frequency detection is implemented by simultaneously radiating signals at each possible resonant frequencies for the tag circuits (13). The system is useful for coding any articles such as baggage or production inventory. Preferably, the radiated signals are phase shifted during the detection process, and signals received by receiver antennas, besides transmitter signals, may be monitored to improve the reliability of detecting the resonant circuits (13). Also, a preferred step adjustment configuration for capacitive metalizations (106, 110) of the resonant circuits is described. For radiating signals into the detection zone (14), focused beam antennas (201) may be used such that each resonant circuit location on the tag can be separately monitored. Also, an apparatus (300) for producing customized resonant circuit tags in accordance with a specified input code is described.

Claims

1. RF tagging system comprising:

a tag having thereon a plurality of passive resonant circuits, each of said passive resonant circuits resonant at a different resonant frequency selected from a predetermined plurality of known resonant frequencies;

means for detecting said plurality of passive resonant circuits on said tag, when said tag is in a detection zone, and then providing a corresponding code signal, out of plurality of possible code signals, indicative of which of said resonant frequencies for said passive resonant circuits were detected in said detection zone;

wherein said detection means comprises means for producing a plurality of different oscillator signals, one at each of said plurality of known resonant frequencies, means for simultaneously radiating each of said different frequency oscillator signals in said detection zone, and means for providing said one code signal by measuring signals indicative of absorption of radiated energy at each one of said known resonant frequencies in said detection zone by said passive resonant circuits on said tag, said absorption occurring during said simultaneous radiation of each of said different frequency oscillator signals.

2. RF tagging system according to claim 1 wherein said code signal providing means measures said measured signals during said simultaneous radiation of each of said different frequency oscillator signals.

3. RF tagging system according to claim 2 wherein said measured signals indicative of absorption of radiated energy are provided by measuring magnitudes of said different frequency oscillator signals which are radiated.

4. RF tagging system according to claim 3 wherein said detection means includes means for comparing said measured signals provided by measuring said radiated signal magnitudes when said tag is in said detection zone to signals indicative of the magnitudes of said radiated signals when said tag is outside said detection zone.

6. RF tagging system according to claim 4 wherein said detection means includes receiver antenna means for detecting radiant energy at any of said known resonant frequencies in said detection zone and separate transmitter antennas for radiating said different frequency oscillator signals in said detection zone, and wherein said code signal providing means includes means for measuring signals received at said receiver antennas indicative of energy in said detection zone at any of said known resonant frequencies when said tag is inside said detection zone.

7. RF tagging system according to claim 6 wherein said code signal providing means includes means for also measuring signals received at said receiver antennas when said tag is outside said detection zone and comparing these signals to said signals received by said receiver antenna means when said tag is in said inside said detection zone.

8. RF tagging system according to claim 2 wherein said code signal providing means includes means for measuring both voltage and current of each of said different frequency oscillator signals to be radiated so as to measure energy of said radiated signals, and wherein said measured energy of said different frequency radiated oscillator signals is measured when said tag is inside and outside said detection zone, said code signal providing means including means for comparing said measured voltage and current signals when said tag is inside said detection zone with said measured voltage and current signals measured when said tag is outside of said detection zone to indicate the presence of resonant circuits on said tag at any of said predetermined plurality of known frequencies.

9. RF tagging system according to claim 2 wherein said detection means includes receiver antenna means for detecting radiant energy at any of said known resonant frequencies in said detection zone and separate transmitter antennas for radiating said different frequency oscillator signals in said detection zone, and wherein said code signal providing means includes means for measuring signals received at said receiver antennas indicative of energy in said detection zone at any of said known resonant frequencies when said tag is inside said detection zone and during said simultaneous radiation of said oscillator signals.

10. RF tagging system according to claim 9 wherein said code signal providing means includes means for also measuring signals received at said receiver antennas when said tag is outside said detection zone and comparing these signals to said signals received by said receiver antenna means when said tag is in said inside said detection zone.

11. RF tagging system according to claim 1 wherein said detection means includes sensor means, for detecting when objects having any number of said resonant circuits, including zero, are provided inside said detection zone and when no such objects are provided inside said detection zone.

12. RF tagging system according to claim 11 wherein said sensor means comprises an IR presence detection sensor.

13. RF tagging system according to claim 1 wherein said detection means includes means for sensing an object having any number of said resonant circuits, including zero, approaching said detection zone.

14. RF tagging system according to claim 13 wherein said code signal providing means includes means for storing a no load reference value of said measured signals in response to determining the approach of an object to said detection zone by said object approaching sensing means and utilizing said stored signals for comparison with said measured signals measured in response to detecting positioning of said object in said detection zone.

16. RF tagging system according to claim 1 wherein said code signal providing means includes means for measuring both voltage and current of each of said different frequency oscillator signals to be radiated so as to measure energy of said radiated signals, and wherein said measured energy of said different frequency radiated oscillator signals is measured when said tag is inside and outside said detection zone, said code signal providing means including means for comparing said measured voltage and current signals when said tag is inside said detection zone with said measured voltage and current signals measured when said tag is outside of said detection zone to indicate the presence of resonant circuits on said tag at any of said predetermined plurality of known frequencies.

5. RF tagging system according to 4 wherein said measured signals are measured when said tag is in said detection zone and said radiated signals are provided with a first phase shift, and said measured signals are also provided when said tag is in said detection zone and said radiated signals are provided with a second and different phase shift, detection of whether one of said resonant circuits in said detection zone is resonant at one of said plurality of known resonant frequencies being dependent on absorption of radiant energy which occurs when said signals are radiated with any of said first and second phase shifts.

15. RF tagging system according to 1 wherein said measured signals are measured when said tag is in said detection zone and said radiated signals are provided with a first phase shift, and said measured signals are also provided when said tag is in said detection zone and said radiated signals are provided with a second and different phase shift, detection of whether one of said resonant circuits in said detection zone is resonant at one of said plurality of known resonant frequencies being dependent on absorption of radiant energy which occurs when said signals are radiated with any of said first and second phase shifts.

17. RF tagging system comprising:

a tag having thereon a plurality of passive resonant circuits, each of said passive resonant circuits resonant at a different resonant frequency selected from a predetermined plurality of known resonant frequencies;

means for detecting said plurality of passive resonant circuits on said tag, when said tag is in a detection zone, and then providing a corresponding code signal, out of a plurality of possible code signals, indicative of which of said resonant frequencies for said passive resonant circuits were detected in said detection zone;

wherein said detection means comprises means for producing a plurality of different oscillator signals, one at each of said plurality of known resonant frequencies, means for radiating each of said different frequency oscillator signals in said detection zone, and means for providing said one code signal by measuring signals indicative of absorption of radiated energy at each one of said known resonant frequencies in said detection zone by said passive resonant circuits on said tag, said absorption occurring during said radiation of each of said different frequency oscillator signals,

wherein said measured signals are provided when said tag is in said detection zone and said radiated signals are provided with a first phase shift, and said measured signals are also provided when said tag is in said detection zone and said radiated signals are provided with a second and different phase shift, detection of whether one of said resonant circuits in said detection zone is resonant at one of said plurality of known resonant frequencies being dependent on absorption of radiant energy which occurs when said signals are radiated with any of said first and second phase shifts.

18. RF tagging system comprising:

a tag having thereon a plurality of passive resonant circuits, each of said passive resonant circuits resonant at a different resonant frequency selected from a predetermined plurality of known resonant frequencies;

means for detecting said plurality of passive resonant circuits on said tag, when said tag is in a detection zone, and then providing a corresponding code signal, out of a plurality of possible code signals, indicative of which of said resonant frequencies for said passive resonant circuits were detected in said detection zone;

wherein said detection means comprises means for producing a plurality of different oscillator signals, one at each one of said plurality of known resonant frequencies, means for radiating each of said different frequency oscillator signals in said detection zone, and means for providing said one code signal by measuring signals indicative of absorption of radiated energy at each one of said known resonant frequencies in said detection zone by said passive resonant circuits on said tag, said absorption occurring during said radiation of each of said different frequency oscillator signals,

wherein said measured signals are provided when said tag is in said detection zone and said radiated signals are provided with a first polarization, and said measured signals are also provided when said tag is in said detection zone and said radiated signals are provided with a second and different polarization, detection of whether one of said resonant circuits in said detection zone is resonant at one of said plurality of known resonant frequencies being dependent on absorption of radiant energy which occurs when said signals are radiated with any of said first and second polarizations.

19. RF tagging system comprising:

a tag having thereon a plurality of passive resonant circuits, each of said passive resonant circuits resonant at a different resonant frequency selected from a predetermined plurality of known resonant frequencies;

means for detecting said plurality of passive resonant circuits on said tag, when said tag is in a detection zone, and then providing a corresponding code signal, out of plurality of possible code signals, indicative of which of said resonant frequencies for said passive resonant circuits were detected in said detection zone;

wherein said detection means comprises means for producing a plurality of different oscillator signals, one at each of said plurality of known resonant frequencies, means for radiating each of said different frequency oscillator signals in said detection zone, and means for providing said one code signal by measuring signals indicative of absorption of radiated energy at each one of said known resonant frequencies in said detection zone by said passive resonant circuits on said tag, said absorption occurring during said radiation of each of said different frequency oscillator signals,

wherein said measured signals are provided when said tag is in said detection zone and said radiated signals are provided with a first phase shift and a first polarization, and said measured signals are also provided when said tag is in said detection zone and said radiated signals are provided with a second and different phase shift and a second and different polarization, detection of whether one of said resonant circuits in said detection zone is resonant at one of said plurality of known resonant frequencies being dependent on absorption of radiant energy which occurs when said signals are radiated with any of said first and second phase shifts and polarizations.

20. RF tagging system comprising:

a tag having thereon a plurality of passive resonant circuits, each of said passive resonant circuits resonant at a different resonant frequency selected from a predetermined plurality of resonant frequencies;

means for detecting said plurality of passive resonant circuits on said tag, when said tag is in a detection zone, and then providing a corresponding code signal, out of a plurality of possible code signals, indicative of which of said resonant frequencies for said passive resonant circuits were detected in said detection zone;

wherein said detection means comprises means for producing a plurality of different oscillator signals, one at each of said plurality of known resonant frequencies, means for radiating each of said different frequency oscillator signals in said detection zone, and means for providing said one code signal by measuring signals indicative of absorption of radiated energy at each one of said known resonant frequencies in said detection zone by said passive resonant circuits on said tag, said absorption occurring during said radiation of each of said different frequency oscillator signals,

wherein said code signal providing means includes means for measuring both voltage and current of each of said different frequency oscillator signals so as to measure energy and wherein said measured energy of said different frequency oscillator signals is measured when said tag is inside and outside said detection zone, said code signal providing means including means for comparing said measured voltage and current signals when said tag is inside said detection zone with said measured voltage and current signals measured when said tag is outside of said detection zone to indicate the presence of resonant circuits on said tag at any of said predetermined plurality of known frequencies.

21. RF tagging system comprising:

a tag having thereon a plurality of passive resonant circuits, each of said circuits resonant at a resonant frequency selected from a predetermined plurality of known resonant frequencies; and

means for detecting said plurality of passive resonant circuits on said tag, when said tag is in a detection zone, and then providing a corresponding code signal, out of a plurality of possible code signals, indicative of which of said resonant frequencies for said passive resonant circuits were detected as being in said detection zone;

wherein each of said plurality of resonant circuits on said tag comprises a first metalization area determining an inductance and a second metalization area determining a capacitance for said resonant circuit, said second metalization area defining a capacitor plate having a plurality of planar capacitive metalization projections each connected to one another by a thin conductor runner, whereby step adjustment of the resonant frequency of the resonant circuit is readily achieved by removing one or more of said conductor runners either during initial manufacture or subsequently.

22. RF tagging system according to claim 21 wherein said plurality of capacitive metalization projections all are disposed about and extend generally inward toward a central location with said runners disposed away from and outward with respect to said central location.

23. RF tag comprising:

a tag base having thereon a plurality of passive resonant circuits, each of said circuits resonant at a resonant frequency selected from a predetermined plurality of known resonant frequencies;

wherein each of said plurality of resonant circuits on said tag base comprises a first metalization area determining an inductance and a second metalization area determining a capacitance for said resonant circuit, said second metalization area defining a capacitor plate having a plurality of planar capacitive metalization projections each connected to one another by a thin conductor runner, whereby step adjustment of the resonant frequency of the resonant circuit is readily achieved by removing one or more of said conductor runners either during initial manufacture or subsequently.

24. RF tag according to claim 23 wherein said plurality of capacitive metalization projections all are disposed about and extend generally inward toward a central location with said runners disposed away from and outward with respect to said central location.

25. RF tag comprising:

a tag base having thereon a plurality of passive resonant circuits, each of said circuits resonant at a resonant frequency selected from a predetermined plurality of known resonant frequencies;

wherein each of said plurality of resonant circuits on said tag base comprises a first metalization area, having a boundary, determining an inductance, an insulating layer provide on and covering at least a portion of said first metalization area, and a second metalization area provided on said insulating layer and determining a capacitance for said resonant circuit due to overlap with said first metalization area, said second metalization area defining a capacitor plate having a plurality of planar capacitive metalization projections on said insulating layer and positioned above and horizontally overlapping said first metalization area, each of said capacitive metalization projections connected to one another by a thin conductor runner, said runners positioned beyond the boundary of said first metalization area and not overlapping said first metalization area, whereby step adjustment of the resonant frequency of the resonant circuit is readily achieved by removing one or more of said conductor runners either during initial manufacture or subsequently.

26. RF tag according to claim 25 wherein said plurality of capacitive metalization projections all are disposed about and extend generally inward toward a central location with said runners disposed away from and outward with respect to said central location.

27. RF tagging system comprising:

a tag having thereon a plurality of passive resonant circuits, each of said circuits resonant at a frequency selected from a predetermined plurality of known resonant frequencies, each of said resonant circuits provided at a different location on a planar surface of said tag;

means for detecting said plurality of passive resonant circuits on said tag when said tag is in a detection zone, and then providing a corresponding code signal out of a plurality of possible code signals indicative of which of said resonant frequencies for said passive resonant circuits were detected as being in said detection zone;

wherein said detection means includes at least one antenna for radiating each of said plurality of known resonant frequencies, said antenna constructed to provide a narrow focused radiation beam in said detection zone having a focus area of a size X on said tag planar surface, and wherein each of said resonant circuits provided on said tag planar surface has an area of no more than X, and wherein only one of said resonant circuits is provided in the focus area X at any one time.

28. RF tagging system according to claim 27 which includes a plurality of said focused beam antennas each of which is fixed in position with respect to others of said focused beam antennas and each of which radiates each of said predetermined plurality of known resonant frequencies, said plurality of focused beam antennas forming an antenna array.

29. RF tagging system according to claim 28 wherein for each of said resonant circuits on said tag a different one of said focused beam antennas is provided.

30. RF tagging system comprising:

a tag having thereon a plurality of passive resonant circuits, each of said passive resonant circuits resonant at a resonant frequency selected from a predetermined plurality of known resonant frequencies;

means for detecting said plurality of passive resonant circuits on said tag, when said tag is in a detection zone, and then providing a corresponding code signal, out of a plurality of possible code signals, indicative of which of said resonant frequencies for said passive resonant circuits were detected in said detection zone;

wherein said detection means comprises means for producing a plurality of different oscillator signals at each one of said plurality of known resonant frequencies, means for radiating each of said different frequency oscillator signals in said detection zone, and means for providing said one code signal by measuring signals indicative of absorption of radiated energy at each one of said known resonant frequencies in said detection zone by said passive resonant circuits on said tag, said absorption occurring during said radiation of each of said different frequency oscillator signals,

wherein said detection means includes means for sensing an object having any number of said resonant circuits, including zero, approaching said detection zone, and wherein said code signal providing means includes means for storing a no load reference value of said measured signals in response to determining the approach of an object to said detection zone by said object approaching sensing means and utilizing said stored signals for comparison with said measured signals measured in response to detecting positioning of said object in said detection zone.

31. RF tag comprising:

a tag base having thereon a plurality of passive resonant circuits, each of said circuits resonant at a resonant frequency selected from a predetermined plurality of known resonant frequencies;

wherein each of said plurality of resonant circuits on said tag base comprises at least a first metalization area determining at least one of an inductance and capacitance for each of said resonant circuits, said first metalization area formed of printed conductive ink provided on said base.

32. RF tag according to claim 31 wherein each of said plurality of resonant circuits also includes a printed nonconductive ink deposited on said first metalization area and a printed second metalization area, formed of conductive ink, deposited on said nonconductive ink, said first and second metalization areas determining said inductance and capacitance for said resonant circuit.

33. RF tag according to claim 32 wherein said nonconductive ink is provided in a pattern with a hole therein, and a conductive feedthrough between said first and second metalization areas is provided in said hole.

34. A method for providing an RF tag comprising the steps of;

providing a tag base which will have thereon a plurality of passive resonant circuits, each of said circuits resonant at a resonant frequency selected from a predetermined plurality of known resonant frequencies; and

printing with conductive ink on said base at least a first metalization area for each of said plurality of resonant circuits to be provided on said tag base, said first metalization area determining at least one of an inductance and capacitance for each of said resonant circuits.

35. A method according to claim 34 which includes the step of printing a nonconductive ink on said first metalization area and printing a second metalization area, formed of conductive ink, on said nonconductive ink, said first and second metalization areas determining said inductance and capacitance for each of said resonant circuits.

36. A method according to claim 35 wherein said step of printing said nonconductive ink comprises printing said nonconductive ink in a pattern with a hole therein and wherein said method includes the step of providing a conductive feedthrough between said first and second metalization areas through said hole in said nonconductive ink pattern.

37. RF tagging system comprising:

a tag having thereon a plurality of passive resonant circuits, each of said passive resonant circuits resonant at a different resonant frequency selected from a predetermined plurality of known resonant frequencies;

means for detecting said plurality of passive resonant circuits on said tag, when said tag is in a detection zone, and then providing a corresponding code signal, out of plurality of possible code signals, indicative of which of said resonant frequencies for said passive resonant circuits were detected in said detection zone;

wherein said detection means comprises means for simultaneously radiating RF energy at least each of said predetermined plurality of known resonant frequencies in said detection zone, and means for providing said one code signal by measuring signals indicative of absorption of said radiated energy at each one of said known resonant frequencies in said detection zone by said passive resonant circuits on said tag.

38. RF tagging system comprising:

a tag having thereon a plurality of passive resonant circuits, each of said passive resonant circuits resonant at a different resonant frequency selected from a predetermined plurality of known resonant frequencies;

means for detecting said plurality of passive resonant circuits on said tag, when said tag is in a detection zone, and then providing a corresponding code signal, out of a plurality of possible code signals, indicative of which of said resonant frequencies for said passive resonant circuits were detected in said detection zone;

wherein said detection means comprises means for radiating RF energy at at least each of said predetermined plurality of known resonant frequencies in said detection zone, and means for providing said one code signal by measuring signals indicative of absorption of said radiated energy at each one of said known resonant frequencies in said detection zone by said passive resonant circuits on said tag,

wherein said measured signals are provided when said tag is in said detection zone and said radiated energy is provided with a first phase shift, and said measured signals are also provided when said tag is in said detection zone and said radiated energy is provided with a second and different phase shift, detection of whether one of said resonant circuits in said detection zone is resonant at one of said plurality of known resonant frequencies being dependent on absorption of radiant energy which occurs when said RF energy is radiated with any of said first and second phase shifts.

39. RF tagging system comprising:

a tag having thereon a plurality of passive resonant circuits, each of said passive resonant circuits resonant at a different resonant frequency selected from a predetermined plurality of known resonant frequencies;

means for detecting said plurality of passive resonant circuits on said tag, when said tag is in a detection zone, and then providing a corresponding code signal, out of a plurality of possible code signals, indicative of which of said resonant frequencies for said passive resonant circuits were detected in said detection zone;

wherein said detection means comprises means for radiating RF energy at at least each of said predetermined plurality of known resonant frequencies in said detection zone, and means for providing said one code signal by measuring signals indicative of absorption of said radiated energy at each one of said known resonant frequencies in said detection zone by said passive resonant circuits on said tag,

wherein said measured signals are provided when said tag is in said detection zone and said radiated energy is provided with a first polarization, and said measured signals are also provided when said tag is in said detection zone and said radiated energy is provided with a second and different polarization, detection of whether one of said resonant circuits in said detection zone is resonant at one of said plurality of known resonant frequencies being dependent on absorption of radiant energy which occurs when said RF energy is radiated with any of said first and second polarizations.

40. RF tagging system comprising:

a tag having thereon a plurality of passive resonant circuits, each of said passive resonant circuits resonant at a different resonant frequency selected from a predetermined plurality of known resonant frequencies;

means for detecting said plurality of passive resonant circuits on said tag, when said tag is in a detection zone, and then providing a corresponding code signal, out of a plurality of possible code signals, indicative of which of said resonant frequencies for said passive resonant circuits were detected in said detection zone;

wherein said detection means comprises means for radiating RF energy at at least each of said predetermined plurality of known resonant frequencies in said detection zone, and means for providing said one code signal by measuring signals indicative of absorption of radiated energy at each one of said known resonant frequencies in said detection zone by said passive resonant circuits on said tag,

wherein said code signal providing means includes means for measuring both voltage and current at each of said predetermined plurality of known resonant frequencies and wherein said measured voltage and current signals are measured when said tag is inside and outside said detection zone, said code signal providing means including means for comparing said measured voltage and current signals when said tag is inside said detection zone with said measured voltage and current signals measured when said tag is outside of said detection zone to indicate the presence of resonant circuits on said tag at any of said predetermined plurality of known frequencies.

41. RF tagging system comprising:

a tag having thereon a plurality of passive resonant circuits, each of said passive resonant circuits resonant at a resonant frequency selected from a predetermined plurality of known resonant frequencies;

means for detecting said plurality of passive resonant circuits on said tag, when said tag is in a detection zone, and then providing a corresponding code signal, out of plurality of possible code signals, indicative of which of said resonant frequencies for said passive resonant circuits were detected in said detection zone;

wherein said detection means comprises means for radiating RF energy at at least each of said predetermined plurality of known resonant frequencies in said detection zone, and means for providing said one code signal by measuring signals indicative of absorption of radiated energy at each one of said known resonant frequencies in said detection zone by said passive resonant circuits on said tag,

wherein said detection means includes means for sensing an object having any number of said resonant circuits, including zero, approaching said detection zone, and wherein said code signal providing means includes means for storing a no load reference value of said measured signals in response to determining the approach of an object to said detection zone by said object approaching sensing means and utilizing said stored signals for comparison with said measured signals measured in response to detecting positioning of said object in said detection zone.