Fig. 1. Designed coding phase gradient metasurface unit. (a) Main view; (b) top view

Fig. 2. Reflection amplitude and reflection phase for co-polarization of encoded phase gradient metasurface under normal incidence of the x-polarized and y-polarized waves. (a) Reflection amplitude; (b) reflection phase

Fig. 3. Reflection amplitude and reflection phase for co-polarization of encoded phase gradient metasurface under normal incidence of RCP waves with different rotation angle α values. (a) Reflection amplitude; (b) reflection phase

Fig. 4. Coding element of 1 bit. (a) Coding element "0"; (b) coding element "1"; (c) reflection phase of coding element "0" and coding element "1" at 1.2 THz

Fig. 5. Flowchart of genetic algorithm

Fig. 6. Design of arrangement. (a) Convergence characteristics of genetic algorithm; (b) schematic diagram of arrangement M1

Fig. 7. Schematic diagram of coding phase gradient metasurface. (a) Coding element "0"; (b) arrangement M1; (c) coding element "1"

Fig. 8. Far-field scattering of coding phase gradient metasurface under vertical incidence of different polarized waves at 1.2 THz. (a) RCP wave; (b) LCP wave; (c) x-polarized wave; (d) y-polarized wave

Fig. 9. Far-field scattering corresponding to coding phase gradient metasurface at different THz frequencies, under normally incident x-polarized wave(left) and y-polarized wave(right). (a) 1.0 THz; (b) 1.2 THz; (c) 1.4 THz; (d) 1.6 THz

Fig. 10. Simulated RCS reduction of designed metasurface compared to the metal plate of the same size under normal incidence of the x-polarized and y-polarized waves. (a) Coding phase gradient metasurface; (b) coding phase gradient metasurface and ordinary coding metasurface without gradient

Fig. 11. RCS reduction value of coding phase gradient metasurface under different incident angles. (a) x-polarized wave; (b) y-polarized wave