• Carbonyl iron powder modification of the dielectric layer significantly enhances electromagnetic wave attenuation, achieving a broadband absorption (RL ≤ –10 dB) from 4.98 to 18 GHz covering C, X, and Ku bands.
• The modified dielectric layer contributes over 30% of total power loss in the 2–18 GHz range, nearly doubling the effective absorption bandwidth compared to unmodified dielectric layers.
• The absorber exhibits excellent angular stability, maintaining at least 80% absorption (RL ≤ –7 dB) up to 60° incidence across 7.0–18.0 GHz.
• This method offers a simple, thin-profile manufacturing process, providing a promising alternative for broadband absorber design.