RFID READER SYSTEMS WITH DIGITAL RATE CONVERSION
First Claim
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1. A method for an RFID reader system using digital rate conversion for timing recovery, the method comprising:
- receiving a tag response signal waveform;
obtaining sample values of the tag response signal waveform at sample time points;
reconstructing signal values at target time points from the sample values by computing a desired time variant fractional delay;
outputting the reconstructed signal values; and
further processing the output signal values.
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Abstract
Fractional delay based digital rate conversion is employed for timing recovery from RFID tag responses at an RFID reader. Signal received from the tag is asynchronously sampled and interpolated. A desired time variant fractional delay coefficient is computed based on the interpolation and time offset is adjusted such that an output sample matches a target point. A data matched filter is optionally integrated with the fractional delay based digital rate converter, which includes a digital phase lock loop.
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Citations
53 Claims
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1. A method for an RFID reader system using digital rate conversion for timing recovery, the method comprising:
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receiving a tag response signal waveform; obtaining sample values of the tag response signal waveform at sample time points; reconstructing signal values at target time points from the sample values by computing a desired time variant fractional delay; outputting the reconstructed signal values; and further processing the output signal values. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. An RFID reader system arranged to use digital rate conversion for timing recovery, comprising:
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a receiver circuit configured to receive a tag response signal; a signal processing circuit configured to; receive a tag response signal waveform; obtain sample values of the tag response signal waveform at sample time points; reconstruct signal values at target time points from the sample values by computing a desired time variant fractional delay; and output the reconstructed signal values. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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36. A circuit for a Radio Frequency Identification (RFID) reader system, comprising:
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a digital rate converter circuit arranged to; obtain sample values of a tag response signal waveform at sample time points; reconstruct signal values at target time points from the sample values by computing a desired time variant fractional delay; and output the reconstructed signal values; a phase detector coupled to the digital rate converter, the phase detector receiving an input signal that is also an output signal from the offset sample points; a loop filter coupled to the phase detector; a numerically controlled oscillator coupled to the loop filter and to the digital rate converter; and a matched filter coupled to fee digital rate converter. - View Dependent Claims (37, 38, 39, 40, 41, 42, 43, 49)
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44. An RFID reader system arranged to use digital rate conversion for timing recovery, comprising:
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means for receiving a tag response signal waveform; means for obtaining sample values of the tag response signal waveform at sample time points; means for reconstructing signal values at target time points from the sample values by computing a desired time variant fractional delay; means for outputting the reconstructed signal values; and means for further processing the output signal values. - View Dependent Claims (45, 46, 47)
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48. A computer readable storage medium for an RFID reader system with instructions stored thereon for performing digital rate conversion for timing recovery, the instructions comprising:
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receiving a tag response signal waveform; obtaining sample values of the tag response signal waveform at sample time points; reconstructing signal values at target time points from the sample values by computing a desired time variant fractional delay; outputting the reconstructed signal values; and further processing the output signal values. - View Dependent Claims (50, 51, 52, 53)
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Specification