Single-layer transmissive metasurface for generating OAM vortex wave with homogeneous radiation based on the principle of Fabry-Perot cavity

摘要

In this paper, a single-layer transmissive metasurface (TMS) is designed to generate orbital angular momentum (OAM) vortex waves with homogeneous radiation at microwave frequencies (e.g., 10 GHz). A single-layer TMS with the thickness of 3 mm (0.1 lambda(0)) is designed by well connecting the phase shift range of two elemental TMS structures. Specifically, two TMS structures-meandering patch-double meandering rings and meandering patch-single meandering ring with the unit-cell size of 7.5 mm (0.25 lambda(0))-are used together to achieve high transmission efficiency (0.8) and a large phase coverage range (360 degrees). In order to address issues such as uneven circumferential radiation and posterior lobe radiation and further enhance the efficiency of the TMS, the modified principle of Fabry-Perot cavity (FPc) suited for realizing the TMS to generate OAM vortex waves is proposed, analyzed closely, and applied. Specifically, an improved rectangular microstrip antenna is employed as a feeding source and a double square ring array is used to construct the backplane. A prototype of the proposed TMS with a FPc is designed, simulated, manufactured, and measured. The simulated and experimental results agree well, which demonstrate the feasibility of the presented design methodology. Published under license by AIP Publishing.