An Active Leakage Canceller Adopting Switched-Capacitor Digital Power Amplifier for UHF-RFID Transceiver

A low-noise active leakage canceller (ALC) for radio frequency identification (RFID) transceiver is reported. The proposed ALC suppresses the strong transmitter (TX) leakage at the receiver (RX) input through continuous leakage tracking by employing an I/Q harmonic rejection switched-capacitor digital power amplifier (I/Q HR SC DPA). Compared to the analog feedback loop-based ALC, the proposed ALC minimizes the noise figure (NF) degradation in the RX and eliminates the large-size passive components in the analog low pass filter, which leads to high RX sensitivity and small chip area. Implemented in a 55-nm CMOS, the proposed ALC suppresses -10 dBm TX leakage down to -47.2 dBm while degrading the RX NF by 0.4 dB at the offset frequency of 640 kHz.