RFID tag and driving method thereof
First Claim
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1. An RFID tag comprising:
- an antenna circuit for receiving an AC signal;
a first circuit for generating DC voltage for driving a logic circuit from the AC signal;
a second circuit for detecting an envelope from the AC signal;
a third circuit for detecting a potential difference between the DC voltage and reference voltage, wherein the third circuit is configured to output a potential corresponding to the potential difference;
a fourth circuit configured to change an impedance of the antenna circuit in accordance with the potential; and
a fifth circuit controlled by the envelope for selecting whether or not the potential output from the third circuit is input to the fourth circuit.
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Abstract
The wireless tag includes a circuit which receives an AC signal from the outside and detects an envelope, a detection circuit which detects the level of electric power supplied from the outside and outputs a potential corresponding to the detected electric power, a protection circuit which changes an impedance of a circuit receiving the electric power in accordance with the electric power output from the detection circuit, a selection circuit portion which selects whether the electric power output from the detection circuit is input to the protection circuit.
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Citations
8 Claims
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1. An RFID tag comprising:
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an antenna circuit for receiving an AC signal; a first circuit for generating DC voltage for driving a logic circuit from the AC signal; a second circuit for detecting an envelope from the AC signal; a third circuit for detecting a potential difference between the DC voltage and reference voltage, wherein the third circuit is configured to output a potential corresponding to the potential difference; a fourth circuit configured to change an impedance of the antenna circuit in accordance with the potential; and a fifth circuit controlled by the envelope for selecting whether or not the potential output from the third circuit is input to the fourth circuit. - View Dependent Claims (2, 3)
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4. An RFID tag comprising:
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an antenna circuit for receiving an AC signal; a first circuit for generating DC voltage for driving a logic circuit from the AC signal; a second circuit for detecting an envelope from the AC signal; a third circuit for shaping the envelope and outputting a pulse signal; a fourth circuit for detecting a potential difference between the DC voltage and reference voltage, wherein the fourth circuit is configured to output a potential corresponding to the potential difference; a fifth circuit configured to change an impedance of the antenna circuit in accordance with the potential; and a sixth circuit controlled by the pulse signal for selecting whether or not the potential output from the fourth circuit is input to the fifth circuit. - View Dependent Claims (5, 6)
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7. A driving method of an RFID tag comprising:
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receiving an AC signal by an antenna circuit; generating DC voltage from the AC signal for driving a logic circuit; detecting an envelope from the AC signal; detecting a potential difference between the DC voltage and reference voltage; outputting a potential corresponding to the potential difference; and changing an impedance of the antenna circuit by the potential difference controlled by the envelope.
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8. A driving method of an RFID tag comprising:
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receiving an AC signal by an antenna circuit; generating DC voltage from the AC signal for driving a logic circuit; detecting an envelope from the AC signal; shaping the envelope and generating a pulse signal; detecting a potential difference between the DC voltage and reference voltage; outputting a potential corresponding to the potential difference; and changing an impedance of the antenna circuit by the potential difference controlled by the pulse signal.
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Specification