COMBINATION FULL-DUPLEX AND HALF-DUPLEX ELECTRONIC IDENTIFICATION TAG

• US 20100052869A1
• Filed: 09/04/2009
• Published: 03/04/2010
• Est. Priority Date: 09/04/2008
• Status: Active Grant

• Current Assignee: MSD International GmbH (Merck & Co., Inc.)
• Original Assignee: Allflex USA Incorporated (Merck & Co., Inc.)
• Inventors: Stewart, Robert
• Granted Patent: US 8,581,705 B2
• Time in Patent Office: Days
• US Class Current: 340/10.520
• CPC Class Codes: G06K 19/0709 the source being an interrogation field
• CPC Class Codes: G06K 19/0712 the arrangement being capable of triggering distinct operating modes or functions dependent on the strength of an energy or interrogation field in the proximity of the record carrier active means for hindering electromagnetic reading or writing G06K19/07336
• 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 19/0726 the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier

Abstract

Transponders are disclosed that are configurable to operate in an HDX mode and/or an FDX-B mode and that use a switchable load impedance across the transponders'"'"' resonant antenna circuit to induce amplitude and/or frequency modulation. An RF level detection circuit determines when the instantaneous activation signal strength is sufficient to support monoplex, multiplex, and diplex operation. A non-volatile memory stores identification data coded in HDX and FDX-B formats. One embodiment of the invention includes an inductive antenna including two terminals connected to tag circuitry, where the inductive antenna forms a resonant antenna circuit tuned to resonate at the frequency of the activation signal. In addition, the tag circuitry includes a non-volatile memory, the tag circuitry and the resonant antenna circuitry are configurable as an oscillator, the tag circuitry is configured to be powered by electric current induced in the resonant antenna circuit by the activation signal, the tag circuitry includes at least one switchable load impedance connected across the antenna resonant circuit, the tag circuitry is configurable to amplitude modulate the activation signal appearing at the resonant antenna circuit terminals using a switchable load impedance, and the tag circuitry is configurable to frequency shift key modulate the oscillator signal appearing at the resonant antenna circuit terminals using a switchable load impedance.

Claims

1. An identification tag, configured to respond to interrogation cycles that include intervals in which an activation signal is present, and intervals in which the activation signal is absent, the tag comprising:

an inductive antenna including two terminals connected to tag circuitry, where the inductive antenna forms a resonant antenna circuit tuned to resonate at the frequency of the activation signal;

wherein the tag circuitry includes a non-volatile memory;

wherein the tag circuitry and the resonant antenna circuitry are configurable as an oscillator;

wherein the tag circuitry is configured to be powered by electric current induced in the resonant antenna circuit by the activation signal;

wherein the tag circuitry includes at least one switchable load impedance connected across the antenna resonant circuit;

wherein the tag circuitry is configurable to amplitude modulate the activation signal appearing at the resonant antenna circuit terminals using a switchable load impedance; and

wherein the tag circuitry is configurable to frequency shift key modulate the oscillator signal appearing at the resonant antenna circuit terminals using a switchable load impedance.

2. The identification tag of claim 1, wherein:

the non-volatile memory contains full-duplex identification data; and

the tag circuitry is configured so that the tag circuitry amplitude modulates the activation signal with a sequence indicative of the full-duplex identification data.

3. The identification tag of claim 2, wherein the tag circuitry is configured so that the tag circuitry is inhibited from transmitting a frequency shift keyed signal during an interval in which the activation signal is absent.

4. The identification tag of claim 2, further comprising:

a charge capacitor connected to the tag circuitry; and

the tag circuitry is configured to store electrical current induced in the inductive antenna by the activation signal on the charge capacitor.

5. The identification tag of claim 4, wherein the tag circuitry is configured to utilize charge stored on the charge capacitor to power the tag circuitry.

6. The identification tag of claim 5, wherein the tag circuitry is configured to increase the modulation index of at least a portion of the amplitude modulated activation signal when the tag circuitry is powered by charge stored on the charge capacitor during the amplitude modulation.

7. The identification tag of claim 4, wherein:

the non-volatile memory includes half-duplex identification data; and

the tag circuitry is configured so that the tag circuitry utilizes charge stored on the charge capacitor to transmit a frequency shift keyed signal indicative of the half-duplex identification data during an interval in which the activation signal is

absent.

8. The identification tag of claim 7, wherein the tag circuitry is configured so that the tag circuitry amplitude modulates the activation signal with a sequence indicative of the full-duplex identification data and transmits a frequency shift keyed signal indicative of the half-duplex identification data during alternating repetitions of the interrogation cycle.

9. The identification tag of claim 8, wherein the tag circuitry includes an RF threshold detector that configures the tag circuitry to amplitude modulate the activation signal with a sequence indicative of the full-duplex identification data and transmit a frequency shift keyed signal indicative of the half-duplex identification data during alternating repetitions of the interrogation cycle in response to the activation signal inducing a potential difference across the terminals of the inductive antenna exceeding a predetermined threshold.

10. The identification tag of claim 8, wherein the tag circuitry is configured to utilize charge stored on the charge capacitor to increase the modulation index of at least a portion of the amplitude modulated activation signal when the tag circuitry is powered by charge stored on the charge capacitor during the amplitude modulation.

11. The identification tag of claim 10, wherein the RF threshold detector configures the tag circuitry to store charge on the charge capacitor to increase the amplitude of at least a portion of the amplitude modulated activation signal in response to the activation signal inducing a potential difference across the terminals of the inductive antenna exceeding a predetermined threshold.

12. The identification tag of claim 8, wherein the tag circuitry is configured so that the tag circuitry amplitude modulates the activation signal with a sequence indicative of the full-duplex identification data and transmits a frequency shift keyed signal indicative of the half-duplex identification data during each repetition of the interrogation cycle.

13. The identification tag of claim 12, wherein the tag circuitry includes an RF threshold detector that configures the tag circuitry to amplitude modulate the activation signal with a sequence indicative of the full-duplex identification data and transmit a frequency shift keyed signal indicative of the half-duplex identification data during each repetition of the interrogation cycle in response to the activation signal inducing a potential difference across the terminals of the inductive antenna exceeding a predetermined threshold.

14. The identification tag of claim 12, wherein the tag circuitry is configured to utilize charge stored on the charge capacitor to increase the modulation index of at least a portion of the amplitude modulated activation signal when the tag circuitry is powered by charge stored on the charge capacitor during the amplitude modulation.

15. The identification tag of claim 14, wherein the tag circuitry includes an RF threshold detector that configures the tag circuitry to store charge on the charge capacitor to increase the modulation index of at least a portion of the amplitude modulated activation signal in response to the activation signal inducing a potential difference across the terminals of the inductive antenna exceeding a predetermined threshold.

16. The identification tag of claim 1, wherein:

the non-volatile memory also includes half-duplex identification data; and

the tag circuitry is configured so that the tag circuitry utilizes charge stored on the charge capacitor to transmit a frequency shift keyed signal indicative of the half-duplex identification data during an interval in which the activation signal is absent.

17. The identification tag of claim 16, wherein the tag circuitry is configured so that the tag circuitry is inhibited from amplitude modulating the activation signal during an interval in which the activation signal is present.

18. A combined full-duplex and half-duplex identification tag, configured to respond to interrogation cycles that include intervals in which an activation signal is present, and intervals in which the activation signal is absent, the tag comprising:

an inductive antenna including two terminals connected to tag circuitry, where the tag circuitry is configured to combine with the inductive antenna to form a resonant antenna circuit tuned to resonate at the frequency of the activation signal; and

a charge capacitor connected to the tag circuitry;

wherein the tag circuitry includes a non-volatile memory containing full-duplex identification data and half-duplex identification data;

wherein the tag circuitry includes an RF threshold detector configured to determine the magnitude of the potential difference induced across the terminals of the inductive antenna by the activation signal;

wherein the tag circuitry is configured to be powered by electric current induced in the inductive antenna by the activation signal;

wherein the tag circuitry includes at least one switchable load impedance connected across the antenna resonant circuit;

wherein the tag circuitry and the resonant antenna circuitry are configurable as an oscillator;

wherein the tag circuitry is configured so that the tag circuitry amplitude modulates the activation signal using a switchable load impedance with a sequence indicative of the full-duplex identification data when the RF threshold detector detects that the amplitude of the potential difference induced across the terminals of the inductive antenna is below a full-duplex mode threshold;

wherein the tag circuitry is configured so that the tag circuitry amplitude modulates the activation signal with a sequence indicative of the full-duplex identification data using the switchable load impedance and frequency shift key modulates an oscillator signal appearing at the resonant antenna circuit terminals with a sequence indicative of the half-duplex identification data using a switchable load impedance during alternating repetitions of the interrogation cycle when the RF threshold detector detects that the amplitude of the potential difference induced across the terminals of the inductive antenna is at least above the full-duplex mode threshold and is below an multiplex mode threshold; and

wherein the tag circuitry is configured so that the tag circuitry amplitude modulates the activation signal with a sequence indicative of the full-duplex identification data using the switchable load impedance and frequency shift key modulates an oscillator signal appearing at the resonant antenna circuit terminals with a sequence indicative of the half-duplex identification data using a switchable load impedance during each repetition of the interrogation cycle when the RF threshold detector detects that the amplitude of the potential difference induced across the terminals of the inductive antenna is at least above the multiplex mode threshold.

19. The identification tag of claim 18, wherein

the tag circuitry is configured to store at least some of the electric current induced in the inductive antenna by the activation signal;

the tag circuitry is configured to utilize charge stored on the charge capacitor to increase the modulation index of at least a portion of the amplitude modulated activation signal when the RF threshold detector detects that the amplitude of the potential difference induced across the terminals of the inductive antenna is above the full-duplex mode threshold and is below a full-duplex enhanced mode threshold;

the tag circuitry is configured to utilize charge stored on the charge capacitor to increase the modulation index of at least a portion of the amplitude modulated activation signal when the RF threshold detector detects that the amplitude of the potential difference induced across the terminals of the inductive antenna is above the multiple mode threshold and is below the multiplex enhanced mode threshold; and

the tag circuitry is configured to utilize charge stored on the charge capacitor to increase the modulation index of at least a portion of the amplitude modulated activation signal when the RF threshold detector detects that the amplitude of the potential difference induced across the terminals of the inductive antenna is above a diplex mode threshold.

21. The identification tag of claim 19, wherein

the tag circuitry is configured to utilize charge stored on the charge capacitor to increase the modulation index of at least a portion of the amplitude modulated activation signal when the RF threshold detector detects that the amplitude of the potential difference induced across the terminals of the inductive antenna is above the multiple mode threshold and is below the multiplex enhanced mode threshold;

and

the tag circuitry is configured to utilize charge stored on the charge capacitor to increase the modulation index of at least a portion of the amplitude modulated activation signal when RF threshold detector detects that the amplitude of the potential difference induced across the terminals of the inductive antenna above a diplex mode threshold.

20. A combined full-duplex and half-duplex identification tag, configured to respond interrogation cycles that include intervals in which an activation signal is present, and intervals in which an activation signal is absent, the tag comprising:

an inductive antenna including two terminals connected to tag circuitry, where the tag circuitry is configured to combine with the inductive antenna to form a resonant antenna circuit tuned to resonate at the frequency of the activation signal; and

a charge capacitor connected to the tag circuitry;

wherein the tag circuitry includes at least one switchable load impedance connected across the antenna resonant circuit;

wherein the tag circuitry includes a non-volatile memory containing full-duplex identification data and half-duplex identification data;

wherein the tag circuitry is configured to receive power from electric current induced in the inductive antenna by the periodic activation signal;

wherein the tag circuitry is configured to store electrical current induced in the inductive antenna by the activation signal on the charge capacitor;

wherein the tag circuitry includes at least one switchable load impedance connected across the antenna resonant circuit;

wherein the tag circuitry and the resonant antenna circuitry are configurable as an oscillator;

wherein the tag circuitry is configured so that the tag circuitry frequency shift key modulates an oscillator signal appearing at the resonant antenna circuit terminals with a sequence indicative of the half-duplex identification data using a switchable load impedance when the RF threshold detector detects that the amplitude of the potential difference induced across the terminals of the inductive antenna is below an half-duplex mode threshold;

wherein the tag circuitry is configured so that the tag circuitry amplitude modulates the activation signal with a sequence indicative of the full-duplex identification data using the switchable load impedance and frequency shift key modulates an oscillator signal appearing at the resonant antenna circuit terminals with a sequence indicative of the half-duplex identification data using a switchable load impedance during alternating repetitions of the interrogation cycle when the RF threshold detector detects that the amplitude of the potential difference induced across the terminals of the inductive antenna is at least above the half-duplex mode threshold and is below an multiplex mode threshold; and

wherein the tag circuitry is configured so that the tag circuitry amplitude modulates the activation signal with a sequence indicative of the full-duplex identification data using the switchable load impedance and frequency shift key modulates an oscillator signal appearing at the resonant antenna circuit terminals with a sequence indicative of the half-duplex identification data using a switchable load impedance during each repetition of the interrogation cycle when the RF threshold detector detects that the amplitude of the potential difference induced across the terminals of the inductive antenna is at least above the multiplex mode threshold.

22. An integrated circuit for use in radio frequency identification tags, comprising:

two antenna terminals connected to tag circuitry, where the terminals are configured to connect to an inductive antenna;

wherein the tag circuitry comprises;

a non-volatile memory;

a resonant capacitor connected across the antenna terminals;

at least one modulation impedance connected in parallel to the resonant capacitor and a transistor configured to that control current flow through the modulation impedance; and

a ringing oscillator configured to generate a potential difference across the antenna terminals in response to receipt of a trigger pulse; and

a configuration memory, where the configuration memory stores information concerning circuits within the tag circuitry that are active based upon the potential difference across the antenna terminals.

23. A method of communicating an identification code, comprising:

using a tag reader to separately encode the identification code as full-duplex identification data, and half-duplex identification data and to write the full-duplex identification data, and the half-duplex identification data to a radio frequency identification (RFID) tag, where the radio frequency identification tag has a resonant antenna circuit and is configured to respond to receipt of an interrogation cycle including an activation signal by amplitude modulating the activation signal with a sequence indicative of the full-duplex identification data using a switchable load impedance across the RFID tag resonant antenna circuit and transmitting a frequency shift keyed signal indicative of the half-duplex identification data using the switchable load impedance when the activation signal is absent;

activating the RFID tag reader by repeating the interrogation cycle;

detecting the full-duplex identification data and the half-duplex identification data transmitted by the RFID tag using the tag reader; and

decoding the identification code using the full-duplex identification data and the half-duplex identification data using the tag reader.

24. The method of claim 23, where the tag is configured to respond to repeated receipt of an activation signal by amplitude modulating the activation signal with a sequence indicative of the full-duplex identification data during a first interrogation cycle and transmitting a frequency shift keyed signal indicative of the half-duplex identification data during pauses in a second interrogation cycle.

25. The method of claim 23, where the tag is configured to respond to repeated receipt of an interrogation signal by amplitude modulating the activation signal with a sequence indicative of the full-duplex identification data during a portion of each interrogation cycle in which an activation signal is present and transmitting a frequency shift keyed signal indicative of the half-duplex identification data during a portion of each interrogation cycle in which the activation signal is absent.