Patent ID: 7787837

Claim:
An RFID receiver comprising: a nulling path circuit configured to create a phase shifted, amplitude controlled nulling signal, the nulling path circuit comprising: a phase shifter configured to control the phase of a nulling signal, and a variable gain amplifier coupled with the phase shifter, the variable amplifier configured to control the amplitude of the nulling signal; an RF coupler coupled to the phase shifter and the variable gain amplifier, the RF coupler configured to combine the nulling signal and a receive signal, the receive signal comprising an undesired signal, in such a manner so as to provide at least partial cancellation of the undesired signal; an RF detector coupled to the RF coupler, the RF detector configured to detect whether there is sufficient cancellation of the undesired signal and provide feedback; a processor coupled to the phase shifter, the variable gain amplifier, and the detector, the processor configured to control the phase shifter and the variable gain amplifier based on the feedback provided; and an RF power divider coupled to a transmit frequency synthesizer, the phase shifter, and the variable gain amplifier, the RF power divider configured to split a transmit signal into a main path signal and the nulling signal.