Highly symmetric planar metamaterial absorbers based on annular and circular patches

We present the simple designs of metamaterial absorbers which are composed of a periodic array of copper annular (or circular) patches, FR4 substrate, and copper film. With appropriate geometrical parameters, these metamaterials can provide the electric and magnetic resonances overlapping in the given frequency range, and the experiments demonstrate the absorptivities of 97.6% and 96.7% with only a single layer of the metamaterial absorber. The surface currents and field distributions of these metamaterials are discussed to look straight into the resonance mechanism. Furthermore, our numerical simulations confirm that these metamaterial absorbers could be operated at wide angles of incidence. The simple and highly symmetric structures of the metamaterial absorbers proposed would greatly accelerate the practical applications in optics and electromagnetics.