A W-Band Active Quasi-Circulator With Low Loss, Low NF, and Low Power

In this letter, a novel W-band quasi-circulator (QC) characterized by low insertion loss (IL), low noise figure (NF), and low power is proposed. The proposed QC is designed using two couplers, three connecting transmission lines (TLs), and a common-emitter amplifier. The QC utilizes the gain of the amplifier while concurrently mitigating its output noise through the inherent isolation provided by the coupler, overcoming the fundamental 3-dB IL of passive QCs and high NF associated with traditional active QCs. To validate the design, a QC was constructed and manufactured using a 0.13- $\mu $ m SiGe BiCMOS technology. The prototype demonstrated a transmitter-antenna (TX-ANT) IL of 1.09 dB, an antenna-receiver (ANT-RX) IL of 1.68 dB, an ANT-RX NF of 2.9 dB, and a TX-RX isolation of 28.5 dB at 94 GHz, while consuming a low power of 9.7 mW.