3-D broadband subwavelength absorber based on split-ring resonators

Split-ring resonator (SRR) has a narrow absorption response to the incident waves. To broaden the absorption bandwidth, we designed a 3-D structure to place the SRRs of different sizes vertically as a pyramids so that they can resonance in different frequency. Further, we strengthen the absorption effect by loading resistors in the SRRs. The influences of the SRRs' size and coupling effects between SRRs are discussed. So designed low-frequency absorber features broadband absorption, lower profile and small size. The −10dB bandwidth cover frequency range of 1.8–3.7GHz at relative bandwidth 69%. At the highest working frequency of the absorption bandwidth, the electric thickness is less than 0.3 and side length of the unit cell less than 0.25.