An interference canceller for a RFID reader senses a signal related to the interference signal in the receive path of the reader. The canceller outputs an adjustment signal that depends on the sensed signal, which is coupled into the receive path before a downconverter in the receive path. The canceller can use a signal derived from the transmit path in generating the adjustment signal. The canceller adjusts the amplitude or phase (or both) of the derived signal to form the adjustment signal so that it cancels a carrier feed-through interference signal when injected into the receive path. The canceller can include a vector modulator to adjust the amplitude and/or phase of the derived signal; or alternatively, the canceller can include a variable attenuator and a variable phase shifter to adjust the amplitude and/or phase of the derived signal. The loop can be continuous or non-continuous.