Patent ID: 8120465

Claim:
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 SR 1 , and wherein the square wave has a rate M*SR 1 , 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 SR 2 , wherein said second symbol rate is different from said first symbol rate SR 1 .