Transmission coefficients for the simulated at different angles. When the incident angle is normal (0°), the resonant frequency is 5.8 GHz and conversion efficiency is 96.5%; when the incident angle is 15°, the resonant frequency shifts to 5.91 GHz and conversion efficiency is 82.3%, and when the incident angle is 30°, the resonant frequency shifts to 6.06 GHz and conversion efficiency is 71.2%.