Multiband frequency selective surface with open matryoshka elements

In this work, we present a multiband FSS with open matryoshka elements obtained by the insertion of a gap in the matryoshka ring. Taking into account the unit cell dimensions, very low resonant frequencies, up to Wx / λ₀ ≈. 0.065, and multiband behavior are observed, which are regarded as considerable advantages. The influence of the polarization is investigated and an approximate expression for the first resonance of the open matryoshka FSS is proposed. The frequency response for double rings, matryoshka and open matryoshka FSS are discussed. Three FSS, 2, 3 and 4 rings, were designed and fabricated using a low cost fiberglass substrate FR-4. The FSS were numerically and experimentally characterized, from 1.0 GHz to 18.0 GHz, considering both polarizations, x and y. Experimental results, when compared to numerical ones, present a very good agreement. Potential applications and the shown characteristics instigate other research groups to investigate the open matryoshka geometry.