Fig. 1. Conceptual illustration of the RGWEM for near-field and far-field radiation control with binary-amplitude round CELC meta-atoms and the FPGA-based control circuit. This compact platform can support functions including dynamic focusing lens, dynamic holography display, 3D multiplexing holography by manipulating near-field radiation, 2D beam scanning, and frequency scanning by manipulating far-field radiation.

Fig. 2. Structure and properties of the meta-atom. (a) 3D view, (b) side view, (c) top and bottom views of the radiating meta-atom. Simulated (d) electric field distributions and (e) E-plane radiation patterns of the meta-atom under “ON” and “OFF” states when the rotating angle α=0°. (f) Simulated radiation efficiencies of the round CELC and rectangle CELC elements. (g) Simulated amplitude and phase responses of the two-state meta-atom. The diagrams of the round CELC (blue solid line) and rectangle CELC (red dotted line) elements are displayed. Both are loaded with the same PIN diode (black) and are designed to resonate at the same frequency. a=1.9  mm, b=1.68  mm, px=2.4  mm, py=3.5  mm, r1=0.15  mm, s1=0.55  mm, r2=1.4  mm, w2=0.3  mm, W=7  mm.

Fig. 3. 2D RGWEM prototype layout. (a) Top and (b) back views. Each SIW channel is marked by green Arabic numerals, and green circles on the back view represent the solder mask.

Fig. 4. (a) Far-field experiment setup in the microwave anechoic chamber and top view of the fabricated RGWEM prototype. An enlarged image of a through-wall sub-miniature push-on (SMP) connector is shown in the lower right corner. (b) Measured reflection coefficients of channel 4 under the azimuth angle varying from −60° to 60°, and the elevation angle varying from −30° to 30°. The reflection coefficients of other channels are almost the same.

Fig. 5. Simulated and measured normalized far-field patterns with corresponding 1-bit amplitude coding patterns at 26 GHz. (a) E-plane (xoz plane) and (d) H-plane (yoz plane) patterns of the broadside beam. (b), (e) The beam directed at (±30°, 0°), and (c), (f) the beam directed at (±30°, −90°). Measured normalized far-field patterns for (g) the broadside beam and (h) the beam directed at (−30°, 0°), and (i) measured realized gains of these two beams, with frequencies varying from 25 to 28 GHz.

Fig. 6. Measured far-field 2D beam scanning results. Normalized radiation patterns of the RGWEM scanning from −60° to 60° in (a) azimuth and −30° to 30° in (b) elevation. (c), (f) Steering accuracy, (d), (g) realized gain and radiation efficiency, (e), (h) 3 dB beamwidth and sidelobe level of the directional beam at different scanning angles in azimuth and elevation, respectively.

Fig. 7. Diagram of the near-field experiment setup. The measuring system consists of five parts: waveguide probe, RGWEM under test, vector network analyzer (VNA), scanning controller, and personal computer (PC).

Fig. 8. Flowchart of the modified G-S algorithm. The forward propagation and backward projection operation based on the dipole radiation pattern establishes an iterative process between the hologram plane and the imaging plane to get the binary hologram mask.

Fig. 9. (a) Calculated, (b) simulated, and (c) measured results of dynamic focusing and six-point-flower pattern focused at different planes at 26.5 GHz. (d) Measured results of the single-point focus with Z0=58  mm from 25 to 28 GHz.

Fig. 10. Calculated, simulated, and measured results of holographic images of (a1)–(a3) symbol heart, (b1)–(b3) letter S, (c1)–(c3) letter E, and (d1)–(d3) letter U.

Fig. 11. Simulated and measured Co values and imaging efficiencies of (a), (b) different focus numbers and (c), (d) different holographic images. Calculated (orange dash line), simulated (green dash line), and measured (red dash line) results of holographic images scanning at (e) Z0=40  mm and (f) Z0=80  mm.

Fig. 12. Schematic diagram of radiation from the hologram plane to the imaging plane.

Fig. 13. The binary hologram mask of one focus and the corresponding calculated radiating patterns. (a), (c) The binary hologram mask and the calculated radiating pattern of the GWE metasurface. (b), (d) The binary hologram mask and the calculated radiating pattern of the FSW metasurface.

Fig. 14. (a) Transmission isolation and (b) electric field distribution of the BL compared with the ML.

Fig. 15. 1-bit encode sequences calculated by the modified G–S algorithm based on the radiation pattern of a dipole. One-point focus at (a) Z0=35  mm, (b) 58 mm, (c) 92 mm. (d) Two-point focus, (e) four-point focus, (f) six-point-flower pattern, (h) symbol music, (i) symbol heart, (j) letter S, (k) letter E, and (l) letter U at Z0=58  mm. (g) 3D multiplexing holography.