RFID tag, interrogator and system with improved symbol encoding and decoding
First Claim
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1. In a radio frequency identification system wherein at least one RFID tag generates an uplink message represented by an uplink signal transmitted by backscatter modulation of a radio frequency signal, the uplink signal comprising a sequence of symbols, an Interrogator comprising:
- a transmitter that transmits the radio frequency signal; and
a receiver that receives, demodulates, and decodes the backscatter-modulated radio frequency signal transmitted by the at least RFID tag in order to recover the uplink message therein, said receiver including symbol decoding means that operates in one of a first mode of operation and a second mode of operation to decode the sequence of symbols of the uplink signal;
wherein, in said first mode of operation, the symbol decoder generates a first set of reference waveforms that are derived by multiplying first-type bi-phase baseband waveforms by a square wave, wherein the first-type bi-phase baseband waveforms each have a phase inversion at least on every symbol boundary and each have a first symbol rate SR1, and wherein the square wave has a rate M*SR1, where M is selected from a number of different integer values, andwherein, in said second mode of operation, the symbol decoder generates a second set of reference waveforms that comprise second-type bi-phase baseband waveforms each having a phase inversion at least on every symbol boundary and each having a second symbol rate SR2, wherein said second symbol rate is different from said first symbol rate SR1.
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Abstract
An improved RFID Tag, Interrogator, and system wherein at least one tag modulates a radio frequency signal by modulated backscatter operations.
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Citations
36 Claims
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1. In a radio frequency identification system wherein at least one RFID tag generates an uplink message represented by an uplink signal transmitted by backscatter modulation of a radio frequency signal, the uplink signal comprising a sequence of symbols, an Interrogator comprising:
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a transmitter that transmits the radio frequency signal; and a receiver that receives, demodulates, and decodes the backscatter-modulated radio frequency signal transmitted by the at least RFID tag in order to recover the uplink message therein, said receiver including symbol decoding means that operates in one of a first mode of operation and a second mode of operation to decode the sequence of symbols of the uplink signal; wherein, in said first mode of operation, the symbol decoder generates a first set of reference waveforms that are derived by multiplying first-type bi-phase baseband waveforms by a square wave, wherein the first-type bi-phase baseband waveforms each have a phase inversion at least on every symbol boundary and each have a first symbol rate SR1, and wherein the square wave has a rate M*SR1, where M is selected from a number of different integer values, and wherein, in said second mode of operation, the symbol decoder generates a second set of reference waveforms that comprise second-type bi-phase baseband waveforms each having a phase inversion at least on every symbol boundary and each having a second symbol rate SR2, wherein said second symbol rate is different from said first symbol rate SR1. - 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. In a radio frequency identification system wherein at least one tag modulates a radio frequency signal by modulated backscatter operations, wherein the modulated radio frequency signal transmitted by the at least one tag encodes an uplink message that is represented by a sequence of symbols, a method for receiving the modulated radio frequency signal comprising:
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receiving the modulated radio frequency signal at an antenna; amplifying components of the received modulated radio frequency signal; demodulating the amplified components of received modulated radio frequency signal; decoding a given symbol by selectively operating in one of a first operational mode and a second operation mode, wherein, in said first mode of operation, the decoding generates a first set of reference waveforms that are derived by multiplying first-type bi-phase baseband waveforms by a square wave, wherein the first-type bi-phase baseband waveforms each have a phase inversion at least on every symbol boundary and each have a first symbol rate SR1, and wherein the square wave has a rate M*SR1, where M is selected from a number of different integer values, and wherein, in said second mode of operation, the decoding generates a second set of reference waveforms that comprise second-type bi-phase baseband waveforms each having a phase inversion at least on every symbol boundary and each having a second symbol rate SR2, wherein said second symbol rate is different from said first symbol rate SR1. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36)
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Specification