Invisible electromagnetic Huygens’ metasurface operational in wide frequency band and its experimental validation

Wideband operation ability becomes an obstacle for many metamaterial applications since they are generally based on effective material (medium) hypothesis, which is intrinsically functional on single frequency or narrowband. Effective biological camouflage strategies involve concealment under sunlight with multiple frequency (color) components, for example, shark could fuse itself into sea water environment for better invisibility and hunting effectiveness. A wideband 3D metasurface ground cloak in Gigahertz frequency order is proposed and realized in experiment with hemispherical profile. A complex unit structure to broaden the operational frequency range for phase preserved electromagnetic metasurface based on difference of elevation is also proposed. Comparison between wideband and its contrast narrowband metasurface clearly indicates the scattering improvement effect that demonstrates the proposed metasurface’s significance. Both instantaneous electric field scanning and reflection cross-section shrinking quantitatively give strong evidence of the wideband operational functions. Comparison between simulation and experiment validated each other. These results indicate the proposed metasurface conceals itself into a background inside a wide frequency spectrum 7.0-9.5 GHz. This structure has great application value for object security under wave package illumination and in landscape fusion. This mechanism also demonstrates the possibility to change other effective material properties in wide frequency band.