Fig. 1. Conceptual illustration of the proposed PCM, which can realize tunable functions for four polarization states and in six channels. The inset describes the mechanism that the spin-decoupled programmable meta-atom achieves 1-bit digital phase modulation in six channels. YX channel denotes the conversion from x-polarized incident waves to y-polarized reflected waves, and other channels can be interpreted similarly.

Fig. 2. (a) The schematic diagram of the spin-decoupled programmable meta-atom, where p=10  mm, d1=4  mm, d2=1  mm, w1=0.7  mm, w2=0.6  mm, α=145°, β=72°, γ=65°, r=3.5  mm, m=0.5  mm, and n=0.6  mm. (b) The equivalent circuits of the PIN diode under ON and OFF states. (c), (d) Simulated surface current distributions of the spin-decoupled programmable meta-atom under orthogonal CP incidence. Simulated co-polarized reflection (e), (f) amplitudes and (g), (h) phases of the spin-decoupled programmable meta-atom with four different PIN diode states under orthogonal CP incidence.

Fig. 3. Simulated co-polarized and cross-polarized reflection (a), (b) amplitudes and (c), (d) phases of the spin-decoupled programmable meta-atom with four different PIN diode states under x-polarized and y-polarized incidence.

Fig. 4. Phase distributions of the PCM in six channels in (a)–(f) Scheme A and (g)–(l) Scheme B.

Fig. 5. Simulated bistatic RCS curves (top panels) and 3D far-field scattering patterns (bottom panels) of Scheme A in (a) LL channel, (b) RR channel, (c) XX channel, (d) YY channel, (e) YX channel, and (f) XY channel at 10 GHz.

Fig. 6. Simulated normalized scattering field distributions of Scheme A in (a) LL channel, (b) RR channel, (c) XX channel, (d) YY channel, (e) YX channel, and (f) XY channel from 9.0 to 10.5 GHz. The theoretical results and experimental results are represented by red lines and white circles, respectively.

Fig. 7. Simulated bistatic RCS curves (top panels), phase profiles of the scattering beams (middle panels), and 3D far-field scattering patterns (bottom panels) of Scheme B in (a) LL channel, (b) RR channel, (c) XX channel, (d) YY channel, (e) YX channel, and (f) XY channel at 10 GHz.

Fig. 8. (a) Fabricated prototype of the proposed PCM. (b) Far-field experimental setup. The measured normalized far-field scattering patterns in (c) LL channel, (d) RR channel, (e) XX channel, (f) YY channel, (g) YX channel, and (h) XY channel at 10 GHz.