In this paper, a CMOS fully integrated transmitter (TX) leakage canceller with a loss compensating amplifier for ultra-high-frequency (UHF) mobile RFID readers and WCDMA duplexer is presented, respectively. The proposed TX leakage canceller consists of an autotransformer, a compensating amplifier, a tuning capacitor, and a tuning resistor. The proposed structure for UHF RFID has a minimum TX to RX rejection of 55 dB and a RX insertion loss of 2.6 dB. The fully integrated TX leakage canceller with the LNA achieves meausred gain of 16.4 dB and meausred noise figure of 6.2 dB. The notch frequency can be digitally tuned from 866 MHz to 961 MHz with the tuning capacitor. The proposed structure as a duplexer for WCDMA has over 55 dB rejection characteristic between the TX and the RX and a 2.5 dB of the RX insertion loss at 1.9 GHz. The notch frequency can be controlled from 1.6 GHz to 2.3 GHz using the digitally controlled 4-bit tuning capacitor. The wideband LNA with the TX leakage canceller achieves simulated gain of 17.4 dB and measured noise figure of 6.2 dB at 1.9 GHz.
