A TX leakage canceller based on an autotransformer with loss compensating amplifier

This paper describes a tunable integrated transmitter leakage canceller based on an autotransformer for ultra-high-frequency (UHF) mobile RFID readers. The proposed TX leakage canceller consists of an autotransformer, a tuning capacitor, a tuning resistor, and a compensating amplifier. The proposed structure has over 55 dB isolation characteristic between a transmitter and a receiver and a 2.5 dB of the RX insertion loss at 900 MHz. A notch frequency of the fully integrated TX leakage canceller can be digitally tuned from 825 MHz to 985 MHz with the tuning capacitor.