Magnet-Free Nonreciprocal Phase-Shifter Based on Time Modulation

Abstract: Recently, nonreciprocal phase shifters have attracted a surge of interest thanks to the advent of nonreciprocal electromagnetic systems, such as nonreciprocal metasurfaces, nonreciprocal-beam antennas, and invisibility cloaks. To overcome the limitations associated with conventional technologies for realizing nonreciprocal phase shifters and gyrators, here we propose a low-noise, lightweight, low-profile, and linear magnetless nonreciprocal phase shifter formed by two temporal loops. The proposed temporal apparatus operates based on the generation of time-harmonic signals and destructive and constructive interferences for the undesired and desired time harmonics, respectively, at different locations of the structure. An external time-harmonic modulation signal injects an effective electronic angular momentum to the system to control the phase and frequency of the two loops. Such a temporal nonreciprocal phase shifter offers low insertion loss, and a large return loss (input matching) of greater than 28.1 dB. Additionally, this nonreciprocal phase shifter possesses a reconfigurable architecture and can be directly embedded in integrated circuit (IC) technology to create high power handling and linear IC-based nonreciprocal phase shifters.