Design of optically transparent broadband conformal absorber with enhanced shielding effectiveness via EHD-printed horseshoe grids

Abstract This paper presents the design of an optically transparent, flexible, and conformal microwave absorber with broadband absorption and high shielding effectiveness (SE). The absorber consists of a horseshoe-shaped metallic grid reflective backplane, a double horseshoe-ring top resonant layer, and a flexible polydimethylsiloxane (PDMS) dielectric layer. Leveraging the high ductility of the horseshoe structure under stretching and bending, the absorber enables long-term conformal applications. An equivalent circuit model (ECM) for the horseshoe grid shielding layer is established to elucidate the influence of its structural parameters on the SE; this model is then extended to the overall absorber design, with ECM calculation results showing good agreement with full-wave simulations. The absorber achieves an absorption rate greater than 90% within the 4–14 GHz frequency band, corresponding to a relative bandwidth of 111.1%. Even under 20% lateral tensile deformation, the absorption rate within this band remains above 80%. The optical transmittance of the absorber is 70.3%, and its SE exceeds 20 dB in the 1–18 GHz frequency range. When conformally applied to a foam cylinder with a radius of 100 mm, the absorber maintains an absorption rate greater than 80% in the X-band for electromagnetic waves with oblique incidence angles up to 30°. Sample testing results confirm its potential for application in electromagnetic stealth.