Modeling and Optimization of Peaking Inductors for X-Band Circulator in Standard 0.18 μm CMOS

Circulator plays a crucial role in the operation of full-duplex radio systems. The major challenge in achieving full-duplex architecture is to isolate the transmitter (TX) channel from the receiver (RX) one. In this paper, an active circulator based on three bridged-T networks which consist of several peaking inductors exploiting a standard 0.18 μm CMOS technology is designed. It is capable of boosting the isolation between the TX and RX channels over a wide frequency range. As part of the proposed circulator design, a tuning platform is devised to explore the impact of various design variables of the peaking inductors on radio frequency benchmarks. It regulates the isolation and insertion loss of the proposed circulator through the assessment of scattering parameters. The simulation results indicate that between the TX and RX channels, a maximum isolation of 43.38 dB at 9.6 GHz is achieved while maintaining at least 30.08 dB of isolation over the whole X-band. The proposed circulator exhibits promising characteristics as a potential choice for duplexers where substantial isolation and wide bandwidth are paramount.