Minimum voltage radio frequency indentification
First Claim
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1. A method of operating a radio frequency identification (RFID) tag having a tank circuit for receiving and transmitting signals, the RFID tag further having a memory, comprising:
- transmitting a power signal to the RFID tag, thereby inducing a voltage in the tank circuit;
detecting a first power supply voltage level, the first power supply voltage level being one in which at least one transistor in the RFID tag just begins to switch;
in response to detection of the first power supply voltage level, modulating a Q factor of the tank circuit in a manner which represents data stored in the RFID tag to effectively transmit the data;
detecting a second power supply voltage level greater than the first power supply voltage level; and
in response to detection of the second power supply voltage level, enabling write operations to a first portion of the memory.
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Abstract
A radio frequency identification device (RFID) which permits various read and write operations at various voltage levels. Certain read operations are permitted as soon as the voltage level in the RFID is sufficient for the circuitry to switch. Errors during such operations are accounted for by retry attempts. Security related operations require higher voltage levels which ensure higher reliability in such operations.
90 Citations
20 Claims
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1. A method of operating a radio frequency identification (RFID) tag having a tank circuit for receiving and transmitting signals, the RFID tag further having a memory, comprising:
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transmitting a power signal to the RFID tag, thereby inducing a voltage in the tank circuit; detecting a first power supply voltage level, the first power supply voltage level being one in which at least one transistor in the RFID tag just begins to switch; in response to detection of the first power supply voltage level, modulating a Q factor of the tank circuit in a manner which represents data stored in the RFID tag to effectively transmit the data; detecting a second power supply voltage level greater than the first power supply voltage level; and in response to detection of the second power supply voltage level, enabling write operations to a first portion of the memory. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of operating a radio frequency identification (RFID) tag, the method comprising:
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receiving a power signal on a radio frequency carrier transmitted to the RFID tag; producing a supply voltage from the received power signal; detecting when the supply voltage reaches a first voltage level, the first voltage level being one in which at least one transistor in the RFID tag just begins to switch; enabling a first memory-read operation in response to detection of the first voltage level; transmitting the data read; detecting when the supply voltage reaches a second voltage level greater than the first voltage level and enabling a memory-write operation in response thereto; and detecting when the supply voltage reaches a third voltage level greater than the second voltage level and in response thereto enabling a second memory-read operation to read a password stored in the RFID tag. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A radio frequency identification (RFID) tag comprising:
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first enabling means for providing a first enable signal; second enabling means for providing a second enable signal; a tank circuit including a load; means for modulating the load to vary the Q factor of the tank circuit; and a memory array having means for reading data contained therein and means for writing data thereinto; the means for reading being coupled to the means for modulating to vary the Q factor of the tank circuit in response to data read from the memory array; the means for reading being coupled to and enabled by the first enabling means; the means for writing being coupled to and enabled by the second enabling means. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification