Fig. 1. Ultra-wideband RIS unit. (a) Main view; (b) top view; (c) reflection amplitude curves; (d) side view; (e) back view; (f) reflection phase curves

Fig. 2. Comparison of reflection amplitude and phase difference simulation results of the proposed unit under oblique incidence (15°, 30°, 45°). (a) (c) Reflection amplitude; (b) (d) phase difference

Fig. 3. Normalized far-field scattering patterns in the u‒v plane at different operating frequencies and coding configurations. (a) Dual beams at (20°, 0°) and (30°, 90°); (b) dual beams at (15°, 0°) and (20°, 90°); (c) single beam at (45°, 0°); (d) triple beams at (45°, 0°), (20°, 0°), and (50°, 180°); (e) RCS reduction scenario 1 (RCS1); (f) RCS reduction scenario 2 (RCS2)

Fig. 4. Far-field simulation results of ultra-wideband RIS. (a) RCS1 and (b) RCS2 at 13 GHz; (c) beams at (45°, 0°) and (45°, 180°) at 12 GHz; (d) beams at (45°,0°), (20°,0°), and (50°,180°) at 12 GHz; (e) beams at (30°, 0°) and (0°, 90°) at 12 GHz; (f) beams at (50°, 180°) and (40°, 270°) at 12 GHz

Fig. 5. Experiment results of RIS. (a) Prototype of ultra-wideband RIS; (b) measured amplitude response; (c) measured phase response; (d) RCS reduction curves with random coding and load voltages

Fig. 6. Far-field test results of the ultra-wideband RIS. (a) Far-field test results of single-beam scanning at 8 GHz, including (15°,0°), (30°,0°), (45°,0°), and (60°,0°). Far-field test results of independent dual-beam control at 12 GHz with beam radiation directions of (b) (30°,0°), (60°,180°); (c) (45°,0°), (40°,180°); (d) (30°,0°), (30°,90°); (e) (40°,180°), (50°,270°); (f) (45°,0°), (20°,0°), and (50°,180°)

Table 1. Structural parameters of proposed unit

Table 2. Wideband performance comparison of ultra-wideband RIS units