RFID READER SYSTEMS DETECTING PILOT TONE
First Claim
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1. A method for a Radio Frequency Identification (RFID) reader system, comprising:
- Receiving from an RFID tag a backscattered signal;
estimating a frequency of a pilot tone in the backscattered signal;
recovering a timing of symbols in the backscattered signal using the estimated frequency; and
demodulating the backscattered signal based on the symbol timing to recover data.
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Abstract
RFID tags are commanded to generate a pilot tone in their backscatter. When the backscattered pilot tone is received in the reader, the pilot tone is used to estimate the tag period/frequency. Then, the estimate is used to seed and lock a symbol timing recovery loop, which provides a detected signal to one or more correlators for detecting the tag preamble. A delayed version of the received tag signal is compared against a baseline signal threshold established from the received signal to detect the pilot tone.
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Citations
42 Claims
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1. A method for a Radio Frequency Identification (RFID) reader system, comprising:
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Receiving from an RFID tag a backscattered signal;
estimating a frequency of a pilot tone in the backscattered signal;
recovering a timing of symbols in the backscattered signal using the estimated frequency; and
demodulating the backscattered signal based on the symbol timing to recover data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A Radio Frequency Identification (RFID) reader system component operable to receive a backscattered RFID tag signal that includes a pilot tone, the component comprising:
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a frequency estimator operable to estimate a frequency of the pilot tone and to generate from it a frequency estimation signal;
a buffer/delay operable to generate a delayed version of the backscattered signal;
a symbol timing recovery loop controlled according to the frequency estimation signal, the symbol timing recovery loop operable to output, responsive to the delayed version of the backscattered signal, a TS signal that has recovered a timing of symbols in the backscattered signal; and
a decoder for decoding the TS signal to recover data. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36)
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37. A Radio Frequency Identification (RFID) reader system component operable to receive a backscattered RFID tag signal that includes a pilot tone, the component comprising:
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means for receiving from an RFID tag a backscattered signal;
means for detecting a pilot tone from the backscattered signal;
means for estimating a frequency of the pilot tone in the backscattered signal;
means for recovering a timing of symbols in the backscattered signal using the estimated frequency; and
means for demodulating the backscattered signal based on the symbol timing to recover data. - View Dependent Claims (38, 39, 40, 41, 42)
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Specification