Microwave absorber based on permeability-near-zero metamaterial made of Swiss roll structures

In this paper, we propose a metamaterial with Swiss roll structure inclusions comprising helically wound metal/dielectric sheets to construct a slab electromagnetic (EM) wave absorber with a thickness of only 1/80 of the working wavelength. The Swiss roll structure, when analyzed under the effective medium theory, exhibits a permeability-near-zero (or mu-near-zero, MNZ) property as the real part of the permeability vanishes to zero, while the imaginary part stays relatively large at a certain frequency band. This property can be utilized to design a microwave metamaterial absorber at deep sub-wavelength thickness. The proposed absorber demonstrates near-perfect absorption at the frequency around 1.3 GHz with incidence angles up to +/- 45 degrees. A topology of orthogonal arranged Swiss roll structures are introduced to form the polarization insensitive metamaterial absorber. Prototypes have been fabricated and measured either in a TEM cell or in a microwave anechoic chamber to validate the absorption performance as well as the design principle. The proposed design could be easily scaled to work at other frequencies as a MNZ metamaterial or ultrathin EM absorber.