Novel Active Quasi-Circulator With Phase Compensation Technique

A novel active quasi-circulator using phase compensation technique for wideband isolation is proposed. It is formed by configuring three transistors with a complimenting phase shifter for equalization. It provides wideband frequency operation with sufficient return loss and isolation between ports without the need for passive filters. This compensation technique minimizes the circulator's size compared with conventional ferrite circulators and is compatible with monolithic microwave integrated circuit technology. Experimental results show that the proposed quasi-circulator has insertion losses around 0 dB, return losses better than 10 dB at each ports and minimum isolation around 15 dB from 0.8 to 2.2 GHz. Good agreement is obtained between simulation and experimental results.