Fig. 1. (a) Scheme of the unit used in the design, (b) top view of the unit.

Fig. 2. The radius a corresponding to the phase shift and transmission amplitude at 32 GHz.

Fig. 3. Panels (a) and (b) are the planes of focused and focused vortex metamaterial, panels (c) and (d) are the three-dimensional (3D) view of metamaterial arrays.

Fig. 4. (a)–(c) Focused electric field distribution of the y–z plane at 30, 32, and 34 GHz. (d)–(f) Focused electric field distribution of the x–y plane at 30, 32, and 34 GHz. (g)–(i) Focused far-field pattern of the metamaterial at 30 GHz, 32 GHz, and 34 GHz.

Fig. 5. (a)–(c) Simulation gains at 30 GHz, 32 GHz, and 34 GHz.

Fig. 6. (a) Incident initial phase; (b) spiral phase; (c) total phase; (d)–(f) Focused vortex electric field distribution at 30, 32 and 34 GHz; (g)–(i) Simulation results of focused vortex phase at 30 GHz, 32 GHz, and 34 GHz.