Analysis of Protective Coating for Optically Transparent Microwave Metamaterial Absorber

The Indium Tin Oxide (ITO) coated Polyethylene Terephthalate (PET) sheets are potentially used to fabricate the transparent microwave metamaterial absorbers (MMA). However, the fragile ITO coatings easily get scratched during vigorous handling which deteriorate their electrical conductivity. Consequently, electromagnetic performance of such MMA structures changes over time. This can be controlled by packaging the MMA using polymer protective coating. Simulations are performed to investigate the EM response of ITO-PET sheets within X-band, before and after a thin layer of protective coating (dielectric constant between 2 and 3). Microwave absorption of ITO with sheet resistance equal to 10
$\Omega/\square$
(ITO (10)) and 100
$\Omega/\square$
(ITO (100)) found to be 9.6% and 45.3% before as well as after the coating of thickness ranging between 10 to 30 µm, After these protective coating, the MMA employed with ITO (10) and ITO (100) also yield approximately similar microwave absorption within broad frequency range of 4–18 GHz and the angular response is also maintained. Hence, service life of MMA can be increased by using polymer protective coatings without any deterioration in their electromagnetic response.