Nearly octave bandwidth microwave absorber with resistance loaded metamaterial

In this paper, we report a metamaterial absorber with nearly octave bandwidth in the microwave frequency. We employ resistance loaded resonance unit cells to reduce the quality factor of the resonance in the metamaterial and expand the absorption bandwidth. The proposed planar metamaterial absorber composes two slabs of print circuit board (PCB) bonded together. The upper one is a dielectric with copper film coated on both sides while the lower one is a single side grounded PCB substrate. The unit cell is composed of vertical metallic loop with serially loaded resistance element through conducting via holes. The optimal design demonstrated a broad microwave absorption with a nearly octave bandwidth from 8.45 GHz to 15.57 GHz for normal incidence in which the power absorption is over 90%. We have also fabricated prototype by PCB technique and characterized its performance through free space transmission measurement in an anechoic chamber. The measurements and simulations agree with each other quite well across the whole frequency range.