A 200 GHz Quasi-Circulator with a Widely Tunable Termination for >30 dB Isolation and 8.3 dB SNR Degradation in a 22nm FD SOI Process

This paper presents a quasi-circulator design optimized for sub-THz applications, operating at 200 GHz and fabricated using 22-nm FD SOI technology. The proposed design features a coupled Coplanar Waveguide (CPWG) and novel tunable terminations, achieving a wide impedance tuning range to address antenna mismatches up to -15 dB. Measurement results demonstrate a TX-to-RX isolation of >30 dB at 200 GHz with over a 7.2-GHz bandwidth and insertion losses of 5 dB and 3.2 dB for TX-to-ANT and ANT-to-RX paths, respectively. This compact, low-power design achieves minimal IL at 200 GHz, offering a robust solution for high-frequency systems.