Dual-frequency broadband metasurface for independently generating multiple vortex beams based on spin decoupling

A dual-frequency broadband metasurface capable of generating four circularly polarized vortex beams with independently control of the topological charge and deflection direction is proposed. The broadband unit based top and bottom layer of the designed metasurface generate the vortex beams in the Ku band (10-20 GHz) and the Ka band (26-30 GHz), respectively. A custom-designed frequency selection surface is inserted to minimize the mutual interference. The far-field measurement experimental results confirm that the designed metasurface generates four vortex beams with the deflection directions of θL = -40°, θR = 20° and θL = -40°, θR = 30°across the broad bandwidth in the Ku and Ka band, respectively.