Patent ID: 7671720

Claim:
An apparatus comprising: a transmitter to transmit a continuous wave (CW) signal to supply radio frequency (RF) energy to power radio frequency identification (RFID) tags, wherein the CW signal is modulated from time to time with an information signal to interrogate the RFID tags in such a wave so as to avoid having to provide separate transmitters to transmit an unmodulated energy frequency and a different modulated signal frequency; a first coupler to output a sampled signal from the CW signal generated by the transmitter; a phase shifter connected to the first coupler to shift the phase of the sampled signal and output a phase shifted signal such that the phase shifted signal is opposite in phase to an unwanted distortion of a received signal; an amplitude adjuster to adjust the phase shifted signal such that the phase shifted signal is opposite in phase and equal in amplitude to the unwanted distortion of the received signal; a summer connected to the amplitude adjuster to add the shifted and adjusted signal to the received signal to generate a summed signal to cancel the unwanted distortion from the received signal and to transmit the summed signal to a signal receiver; and a circuit to adjust the amplitude adjuster and the phase shifter based on a voltage from an RF detector detecting remaining unwanted distortion reflecting the effectiveness of a distortion cancellation in the summed signal.