Wideband Nonmagnetic Circulator Based on Spatiotemporally Modulated Resonators Designed With Coupled Microstrip Lines

ABSTRACT A wideband spatiotemporally modulated nonmagnetic circulator composed of three time‐varying resonators in Y‐topology is presented in this paper. The triple resonators are designed with coupled microstrip lines and connected to a central node. By applying a time‐modulated signal with a 120° progressive phase shift to the resonators, the angular momentum bias is applied to the structure, thereby achieving the circulator response. To enhance the bandwidth, a step impedance resonator is added to the end of each coupled microstrip line resonator, and therefore achieves broad isolation band for the circulator. As validation, a wideband nonmagnetic circulator with a center frequency of 1.0 GHz was designed, fabricated and measured. The measurement results agree well with the simulations, which the 20‐dB isolation bandwidth is 53 MHz, while the maximum in‐band isolation can achieve 34 dB, and the insertion loss is 1.9 dB.