Electrically Discretized Sub-terahertz Phase Shifter Based on Novel Independent Phase Delay Meta-atoms

Abstract

Considering the state of art in terahertz on-chip devices, the conventional microwave phase shifters with multi-layer structures confront the disadvantages of narrow bandwidth, large attenuation, and bulky size, leading to impossible transplant in THz range. In this paper, a broadband terahertz phase shifter based on novel independent phase delay meta-atoms is proposed for electrically discretized phase coding. By integrating a P-I-N diode into a metal grounded half-wavelength scaled resonator, with a bias excitation through two vias connecting with the ground, the phase shifter works under on and off states to achieve a broadband 180° phase shift with the center frequency higher than 0.1 THz. By elaborately engineering the resonant patch size, the reflective efficiency has been maximized to reach over 90%, and the phase change ranges from 0 to 2π. We have analyzed the mechanism and found that it offers large differences of the current flow path between the two different states, so that large phase change occurs in an expanded working bandwidth. The proposed structure provides a phase shift of 180° ± 20° from 76.5 GHz to 124.5 GHz with a relative bandwidth approaching 50%. Compared with the conventional phase shifter based on multi-layered phase shifting structure, the coplanar design has the advantages of broad band, low switching ratio and high reflection efficiency, omitting the intermediate layer with coupling holes, making the structure simpler and easier for the fabrication process. Moreover, the independent 1-bit phase modulation paves a path to terahertz digital beam synthesis with multifarious potentials such as beam scanning, tunable focusing, polarization splitting, and RCS reduction, etc..