Design of a non-magnetic non-reciprocal phase shifter based on spatiotemporal modulation

This paper presents a non-magnetic non-reciprocal phase shifter based on spatiotemporal modulation (STM). By coupling three STM resonators and phase shifting structure into a ring topology, the transmission characteristics with tunable non-reciprocal phase shift can be obtained while keeping good port matching. As a proof of concept, a non-magnetic nonreciprocal phase shifter at 1 GHz is designed. In the passband of 0.98-1.05 GHz, the tunable phase difference (∠S
21
-∠S
12
) of 45° between signals flowing in opposite directions is realized. When the phase difference is 22.5°, a continuous tunable phase shift (∠ S
21
&∠S
12
) of 30° is realized with minimum insertion loss of 2.4 dB and return loss of better than 15 dB.