Design of Non-resonant High-transmission Metasurfaces with Ultra-wide Bandwidth and Flexible Operating Frequencies in Microwave Region

High-transmission metasurfaces enabling near-perfect transmission with ultra-wide bandwidth are desirable in numerous novel applications. In this study, we utilize the recently-proposed scheme to numerically and experimentally illustrate an antireflection coating design, which uses a simple application of subwavelength metallic meta-atoms to a multi-section Chebyshev transformer. A high-transmission relative bandwidth (approximately 100%) can be sustained with ultrathin dielectric substrates and flexible working-frequency bands. Such ultrathin devices and frequency tuning capability stem from the interplay of the magnitude and phases of electromagnetic waves between the interfaces, while the ultra-wide bandwidth is primarily enabled by a carefully designed Chebyshev transformer. In addition, the mechanisms of the broadband metasurface design are explored that a non-resonance or weak resonance of the metasurface shall be implemented. The proposed ultra-wideband high-efficiency metasurfaces designed for impedance-mismatched systems provide promising potential for non-destructive testing applications in the microwave region.