CMOS Nonmagnetic Circulator and Band-Selection Balun-Low Noise Amplifier with RF Self-Interference Cancellation for Advanced In-Band Full-Duplex Transceiver

In this paper, a CMOS nonmagnetic circulator and band-selection balun-low noise amplifier (LNA) with RF time-domain self-interference cancellation (SIC) are presented to realize an advanced in-band full-duplex (IBFD) transceiver. The capacitor (C)-inductor (L)-C nonmagnetic circulator based on an N-path filter and time-domain RF SIC with multi delay tap are employed to achieve low receiver (RX) and transmitter (TX) insertion losses and high SIC. Because the circulator does not possess out-of-band (OB) blocker rejection capability, the band-selection N-path balun-LNA is proposed to replace the functionality of the OB blocker rejection of the conventional SAW filters. Simulated in a 65 nm CMOS process, the circulator and balun-LNA with RF canceller achieved a noise figure of 6.6 dB, voltage gain of 17 dB, and SIC of 58 dB. It has an active die area of 1.61 mm², and consumed 14 mA for a nominal supply voltage of 1 V.