Absorption enhancement of fractal frequency selective surface absorbers by using microwave absorbing material based substrates

In this paper, the effect of microwave absorbing material-based (MAM) substrate on the absorption properties of fractal frequency selective surface (FSS) absorbers was investigated in detail. The fractal shapes were proposed to construct the schematic diagrams of the FSS unit cell. The absorption properties of the absorber samples containing different substrates, including FR-4dielectric substrate and MAM-based substrate, were exhibited via the Naval Research Laboratory (NRL)-arch method, respectively. Then the power loss density distributions of the absorbers were illustrated by the finite integration technology (FIT) method to obtain an insight of the physical picture into the absorption properties. The results indicate that with the increase of the substrate thicknesses, the FR-4-based FSS absorbers could achieve the strongest absorbing performance at a certain thickness. However, employing the MAM-based substrate to replace the FR-4 substrate with the same substrate thickness enhances the absorbing properties greatly, including the peak values and the bandwidths. As a result, the way of introducing the MAM-based substrates instead of the traditional dielectric substrates provides a potential practical application in device miniaturization.

► We study influencing factors of frequency selective surface's absorptions.
► The effects of substrate thicknesses and materials are investigated.
► Increase of FR-4 substrate thickness will make a strongest absorption at 4.5 mm.
► Absorptions enhance greatly after substrate using microwave absorbing material.