Method, system, and apparatus for remote timing calibration of a RFID tag population
First Claim
1. A method of calibrating an oscillator frequency with an input signal in a radio frequency identification (RFID) tag device, comprising the steps of:
- (a) receiving a calibration waveform cycle on the input signal;
(b) incrementing a count word after each cycle of a clock signal that occurs during a length of the received calibration waveform cycle; and
(c) adjusting the oscillator frequency based upon the count word after completion of step (b).
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Accused Products
Abstract
A method, system, and apparatus for a timing subsystem in a radio frequency identification tag device are described. The timing subsystem provides a system oscillator or clock for the tag. The timing subsystem also provides frequencies used by an RF interface of the tag to generate backscatter modulated symbols. The timing subsystem also provides for oscillator calibration. The tag receives one or more oscillator calibration waveforms transmitted by a reader. The timing subsystem in the tag uses the oscillator calibration waveforms to successively adjust the frequency of the tag oscillator to a frequency desired by the reader. Hence, the reader may increase or decrease the oscillator frequency in the tag depending on the particular application. Furthermore, the reader may adjust the oscillator frequency for all tags in a population of tags using a single transmission of the one or more oscillator calibration waveforms.
65 Citations
26 Claims
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1. A method of calibrating an oscillator frequency with an input signal in a radio frequency identification (RFID) tag device, comprising the steps of:
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(a) receiving a calibration waveform cycle on the input signal;
(b) incrementing a count word after each cycle of a clock signal that occurs during a length of the received calibration waveform cycle; and
(c) adjusting the oscillator frequency based upon the count word after completion of step (b). - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of calibrating an oscillator frequency with an input signal in a radio frequency identification (RFID) tag device, comprising the steps of:
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(a) receiving a calibration waveform cycle on the input signal;
(b) incrementing a count word after each cycle of the oscillator frequency that occurs during a length of the received calibration waveform; and
(c) adjusting the oscillator frequency based upon the count word after completion of step (a). - View Dependent Claims (9, 10)
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11. A system for calibrating an oscillator frequency with an input signal in a radio frequency identification (RFID) tag device, comprising:
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an adjustable oscillator that receives a control word and generates an oscillator frequency that is based on the control word;
a counter that receives the oscillator frequency and the input signal, wherein said counter increments a count word each cycle of the oscillator frequency, wherein said counter is cleared after each of a plurality of calibration waveform cycles is received on the input signal; and
a state machine that receives at least one bit of the count word, and modifies a different bit of the control word after said each of the plurality of calibration waveform cycles is received, according to the received at least one bit of the count word, if the received at least one bit of the count word is equal to a first logical value. - View Dependent Claims (12, 13, 14, 15, 16, 18, 20, 21, 22, 23, 25, 26)
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17. A method of sending calibration signals to a radio frequency identification (RFID) tag device from a reader of a reader network to adjust an oscillator frequency of the tag device, comprising the steps of:
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(a) transmitting a of calibration waveform cycle;
(b) transmitting a separation waveform cycle; and
(c) repeating steps (a) and (b) a plurality of times.
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19. A system for controlling an oscillator frequency in a radio frequency identification (RFID) tag device, comprising:
a resistor-capacitor (RC) oscillator that outputs an oscillator frequency, wherein said RC oscillator includes a frequency adjustment bank;
wherein said frequency adjustment bank includes a non-switchable element, and at least one switchable element;
wherein said frequency adjustment bank receives a control word, wherein each said at least one switchable element receives a corresponding bit of said control word;
wherein each of said at least one switchable element is activated by said corresponding bit of said control word if said corresponding bit is equal to a first state, wherein a combination of said non-switchable element and any activated switchable elements of said at least one switchable element affects said oscillator frequency.
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24. A system for generating a plurality of frequencies for use in a radio frequency identification (RFID) tag device, comprising:
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an oscillator that generates an oscillator frequency, and outputs the oscillator frequency on an oscillator signal; and
at least one frequency divider that receives the oscillator signal, wherein each of said at least one divider generates a divided version of said oscillator frequency.
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Specification