Hole-Patterned Carbonyl Iron Powder/Epoxy Composite Low-Profile Electromagnetic Absorber Operating at Ka-Band

This research developed a mmWave electromagnetic (EM) absorber with a simply punched hole pattern, which was introduced on the flat CIP/epoxy composite to overcome the limitation of the magnetic materials. This absorber was designed on a carbonyl iron powder (CIP) and epoxy resin composite with Snoek's limit of about 26 GHz. First, the morphologies of the fabricated CIP/epoxy composite were characterized by scanning electron and atomic force microscopies. Subsequently, the constitutive parameters of the CIP/epoxy composite were measured in the frequency range of 26.5–50 GHz. These measured constitutive parameters of the CIP/epoxy composite material were iteratively revised by the curve-fitting technique to improve the measurement accuracy. An equivalent circuit model was utilized to determine the reflection coefficient of the hole-patterned CIP/epoxy composite mmWave EM absorber, taking into account its material parameters and dimensions. A comprehensive analysis was conducted to evaluate how the performance of the absorber is affected by the dimensions of its unit cell. This was achieved by utilizing both the equivalent circuit and full-wave FEM simulation. The absorption performance of the hole-patterned CIP/epoxy composite mmWave EM absorber is experimentally demonstrated at different angles and polarizations in 26.5–36.5 GHz.