Ultra-wideband absorber for electromagnetic waves under large incident angle based on spoof surface plasmon polaritons

In this work, we proposed an ultra-wideband absorber using the dispersion characteristics of spoof surface plasmon polaritons (SSPP). The electromagnetic waves propagating on the SSPP structure have extremely slow group velocity and are confined in the sub-wavelength regions near the asymptotic frequency of the SSPP, and that electromagnetic energy can be absorbed by the high-lossy substrate and lumped resistors. The metallic strips of the SSPP structure are vertically bended and loaded with lumped resistors, and their lengths are linearly varied. This absorber performs excellent absorption ability, including ultra-wideband absorption, almost polarization insensitive performance, and high absorptivity under large incident angles for both transverse magnetic and transverse electronic waves. Based on the simulation analysis, an absorber sample was fabricated and measured, and the simulated and measured results are consistent with each other, validating the design method.