A Reconfigurable Carrier Leakage Canceler for UHF RFID Reader Front-Ends

This paper presents a new reconfigurable carrier leakage canceler for UHF RFID readers, using a directional coupler and an impedance tuning circuit to improve the sensitivity of the receiver. The impedance tuning circuit, which consists of electrically tunable passive components, can be adaptively tuned to have an optimum reflection coefficient for carrier leakage cancellation. In order to secure the good carrier leakage cancellation performance over the wide operating frequency band, PIN and varactor diodes are used as a variable resistor and a capacitor, respectively, for the impedance tuning circuit. The implemented reconfigurable carrier leakage canceler exhibits more than 65 dB of carrier leakage cancellation over a wide frequency band of 100 MHz, from 860 to 960 MHz when the control voltages of the PIN and varactor diodes are adjusted. As a result, a 15 dB improvement of receiver sensitivity, and 30% improvement of the recognition range have been achieved, respectively, using commercial RFID tags.