Magnet-Free Circulators Based on Linear Time-Varying Circuits

In this paper, magnet-free circulators based on spatiotemporal modulation of three-port resonant junctions are demonstrated. Optimal single-ended implementations based on series or parallel LC tanks connected in a wye or a delta topology, respectively, are developed. Also differential implementations based on combining two single-ended circuits in either a voltage-or a current-mode architecture, resulting in pseudo-linear time-invariant devices with enhanced performance, are presented. Moreover, CMOS integrated and MEMS implementations, suitable for low-cost and large-scale production, are presented. Also, broadband implementations based on combining a narrowband junction with conventional bandpass filters are developed. The proposed circuits are all validated with theoretical, simulated and measured results, with unprecedented performance nearly in all metrics in comparison to the current state of the art.