On-Chip Self-Interference Canceller with Variable Inductor Based Electrical Balance Network for Full Duplex Systems

An on-chip broadband self-interference canceller based on the electrical balance of hybrid transformers is proposed in this work. A variable inductor based on-chip balanced impedance network is utilized to match the actual antenna impedance varying with frequency. In order to achieve broadband electrical balance, an auxiliary quadrature digital transmitter is used to compensate variations of the antenna impedance with frequency. The proposed technique is demonstrated in a standard 130 nm CMOS 1P8M process and the chip occupies 4.84mm2. The simulation results show that the demonstration achieves isolation of more than 60 dB over a 25 MHz bandwidth with 23 dBm transmitter output power at 2 GHz.