RFID tags calibrating backscattering period also for noninteger divide ratios
First Claim
1. A circuit for a radio frequency identification (RFID) tag, comprising:
 a demodulator that is arranged to demodulate a waveform of a wirelessly received wave;
a processing block that includes;
a counter configured to determine an Lnumber from a duration of a calibration feature of the waveform, anda combining circuit configured to combine a first nonzero version of the Lnumber with a second nonzero version of the Lnumber so as to derive a BPnumber such that the derived BPnumber substantially equals the Lnumber divided by a preset noninteger divide ratio; and
a modulator that is arranged to modulate a second wave with encoded symbols that have a periodicity determined from the BPnumber.
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Abstract
An RFID tag that receives a calibration instruction from a reader can determine the basic backscatter period of the symbols to be backscattered. According to some embodiments, when the instruction includes a calibration feature that is to be divided by a divide ratio, the tag measures the duration of the feature in terms of numbers of internal pulses, resulting in a binary Lnumber. Then at least two versions of the Lnumber (PR1number, PR2number) are combined, so as to yield the effective result of the division alternately, even when the divide ratio is a noninteger. The backscatter period can then be determined from the BPnumber and the period of the internal pulses.
20 Citations
78 Claims

1. A circuit for a radio frequency identification (RFID) tag, comprising:

a demodulator that is arranged to demodulate a waveform of a wirelessly received wave; a processing block that includes; a counter configured to determine an Lnumber from a duration of a calibration feature of the waveform, and a combining circuit configured to combine a first nonzero version of the Lnumber with a second nonzero version of the Lnumber so as to derive a BPnumber such that the derived BPnumber substantially equals the Lnumber divided by a preset noninteger divide ratio; and a modulator that is arranged to modulate a second wave with encoded symbols that have a periodicity determined from the BPnumber.  View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)


29. A radio frequency identification (RFID) tag, comprising:

an antenna arranged to receive a wireless wave; a demodulator arranged to demodulate a waveform of the wirelessly received wave; a processing block that includes; a counter configured to determine an Lnumber from a duration of a calibration feature of the waveform, and a combining circuit configured to combine a first nonzero version of the Lnumber with a second nonzero version of the Lnumber so as to derive a BPnumber such that the derived BPnumber substantially equals the Lnumber divided by a preset noninteger divide ratio; and a modulator that is arranged to backscatter via the antenna a wave with modulation that encodes symbols that have a periodicity determined from the BPnumber.  View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37)


38. A circuit for a radio frequency identification (RFID) tag that is responsive to an RFID reader, the RFID tag comprising:

a means for demodulating a waveform from a first wireless wave received from the reader; a means for determining an Lnumber from a duration of a calibration feature of the waveform; a means for deriving a BPnumber by combining a first nonzero version of the Lnumber with a second nonzero version of the Lnumber such that the derived BPnumber substantially equals the Lnumber divided by a preset noninteger divide ratio; and a means for modulating a second wave that is to be received by the reader by encoding symbols with a periodicity determined from the BPnumber.  View Dependent Claims (39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52)


53. A method for an RFID tag, comprising:

receiving a first wireless wave having a waveform; determining an Lnumber from a duration of a calibration feature of the waveform; deriving a BPnumber by combining a first nonzero version of the Lnumber with a second nonzero version of the Lnumber such that the derived BPnumber substantially equals the Lnumber divided by a preset noninteger divide ratio; and modulating a second wave that encodes symbols with a periodicity determined from the BPnumber.  View Dependent Claims (54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78)

1 Specification