Flexible Dielectric Spacer with Tunable Dielectric Properties for Metamaterial Absorber Application

Abstract

Abstract The development of the flexible and robust metamaterial absorber is the great motivation for the new generation of microwave absorbers covering any conformal shape. The ceramic-polymer composites with variable dielectric constant within the microwave frequencies are proposed as a flexible middle dielectric spacer (MDS) layer to provide additional degree of design freedom for metamaterial absorber application. By varying the dielectric constant of MDS layer, the resonance band of metamaterial absorber can be tuned while retaining a low profile besides enhancing its EM performance for TM polarized wave. To formulate these composites, tetragonal structured Barium Titanate ( BaTiO3) powder is selected as an excellent candidate when mixed with elastomer Polydimethylsiloxane (PDMS) resulting in high mechanical strength substrates. Experimentally, samples with a range of dielectric permittivity from 2.81 to 5.67 were obtained for 0% to 20% volume fill fraction of BaTiO3 in PDMS. The obtained dielectric permittivities being consistent with Bruggeman effective medium theory. Utilizing an optimized composition (10% BaTiO3 ), resulting in εr = 4 substrate, an X-band flexible absorber is designed and fabricated to absorb more than 90% of incident EM waves within frequency band of 8.16-12.12 GHz.