Combination full-duplex and half-duplex electronic identification tag
View Patent ↗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.
1. 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 a 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.
2. The identification tag of claim 1 , 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.
3. 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.
4. The identification tag of claim 2 , 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.
5. The identification tag of claim 1 , wherein the full-duplex identification data and the half-duplex identification data are identical.