A Design of Filtering Quasi-Circulator Using Time-Modulated Resonators

This paper presents a novel design of magnetless quasi-circulator using time-modulated resonators. By appropriately selecting modulation parameters of time-modulated resonators, signal transmission can occur from port 1 to port 2 and from port 2 to port 3, while blocking signal transmission in reverse directions and between port 1 and port 3. The proposed quasi-circulator also offers filtering response with a tunable passband frequency. Analytical design equations have been derived for deep understanding of non-reciprocity. To experimentally validate the concept, a prototype of quasi-circulator is designed and fabricated. Experimental results show filtering characteristics with forward transmission loss of 6.68 dB and isolation higher than 45 dB in reverse direction. The passband frequency is tuned from 1.65 GHz to 3.95 GHz by adjusting bias voltage of varactor diodes.