Patent ID: 8344855

Claim:
A radio frequency identification (RFID) interrogator for determining a bandwidth of a backscattering signal to be backscattered by an RFID tag, the RFID interrogator sensing a predetermined frequency band to determine whether the predetermined frequency band is occupied and determining a sensing result, and the RFID interrogator controlling the bandwidth of the backscattering signal in response to the sensing result, wherein the RFID interrogator controls the bandwidth of the backscattering signal by changing at least one bandwidth factor of the backscattering signal, wherein the bandwidth factor comprises at least one of a backscattering link frequency (BLF) and a Miller subcarrier index, wherein when the RFID interrogator determines that the predetermined frequency band is not occupied, the RFID interrogator senses a backscattering signal candidate band based on a predetermined value of the BLF and a predetermined value of the Miller subcarrier index, and wherein when the RFID interrogator determines that the backscattering signal candidate band is occupied based on the sensing result, the RFID interrogator changes the value of the BLF until the backscattering signal candidate band is not occupied, wherein when the RFID interrogator determines that the predetermined frequency band is occupied, the RFID interrogator senses the backscattering signal candidate band based on the predetermined value of the BLF and the predetermined value of the Miller subcarrier index, and wherein when the RFID interrogator determines that the backscattering signal candidate band is occupied based on the sensing result, the RFID interrogator increases or decreases at least one between the value of the BLF and the value of the Miller subcarrier index until the backscattering signal candidate band is not occupied, and wherein the RFID interrogator corrects one of the value of the BLF and the value of the Miller subcarrier index and changes the other one of the value of the BLF and the value of the Miller subcarrier index and senses a backscattering signal candidate band based on the changed value to determine whether it has been occupied, and wherein when all backscattering signal candidate bands corresponding to all available changed values have been occupied, the RFID interrogator adjusts the fixed value.