Magnetless microstrip circulators based on differential spatiotemporal modulation of resonators

Abstract

This article presents a magnetless differential microstrip circulator for high frequency operation. The differential design is obtained by pairing two single‐ended (SE) circulators, each based on three resonators connected in a wye topology with spatiotemporal modulation (STM). What is more, the STM biases of the two SE circulators are kept a fixed 180° phase difference. The resonance of the circuit is realized by varactor‐loaded microstrip line sections rather than conventional series of inductor and varactor. The design method of the proposed microstrip circulator has been presented by analyzing its equivalent circuit, which indicates the microstrip line sections cannot be simply equivalent to inductors with the conventional method. The analysis of the time‐varying circuit is verified by the simulated results of both the microstrip circulator and its equivalent circuit. A magnetless microstrip circulator was designed, fabricated and measured at center frequency of 1.99 GHz, showing maximum isolation (IX) of more than 50 dB, minimum insertion loss of 4.8 dB, and 1.4% 20 dB IX bandwidth.

Non-Magnetic Circulator Using Spatio-Temporal Modulation of Mixed Static and Time-Modulated Resonators

“…시공간 변조(STM: spatio-temporal modulation)는 자성 물질을 사용하지 않고 비가역성(non-reciprocity)을 얻을 수 있는 효과적인 접근법 중 하나이다. STM은 점진적인 위상 편이 신호(progressive phase shift signal)로 공진기를 변조시킴으로 변조 특성을 얻을 수 있는데 서큘레이터, 비가역 여파기, 비가역 전력 분배기와 같은 비자성체 비 가역 회로를 설계하는 데 널리 사용되었다 [3]∼ [6] . 참고문 헌 [7] 및 참고문헌 [8]…”