Linearity and Continuity Enhanced Phase Shifter Based on Geometric-Phase Metasurface

In this article, a geometric-phase (GP) metasurface-inspired phase shifter with linear and continual phase response has been introduced. The output phase can be adjusted by only rotating the GP metasurface. Physically distinct from the traditional phase-shifting techniques relying on the dynamical phase (DP), the phase variation based on the manipulation of the GP is independent of the signal transmission time, leading to desirably stable performances in the working band. To elaborate on the idea, a phased shifter model has been implemented in a circular waveguide by loading a GP metasurface and two polarization converters. Theoretical analysis, including the generation of GP and transmission-line networks, is carried out in detail. In addition, the limitation of this approach is also explored, in order to deliver a general design guideline for practical applications. To further demonstrate our scenario, a proof-of-concept prototype is fabricated and tested. The numerical and experimental results are in good agreement and both validate the effectiveness on the phase linearity and stability in the design frequency band. In conclusion, the proposed frequency-independent phase shifter is very promising for the emerging phased array systems with stable and reliable performance in a wideband.