Design of a Magnetic Composite–Based Ultrawideband Absorber Using a Reactance Compensation Strategy for Ku‐/Ka‐Band Applications

This paper proposes an ultrawideband electromagnetic (EM) absorber that overcomes the bandwidth limitations imposed by Snoek’s limit in conventional magnetic materials. Traditional absorbers suffer from poor absorption efficiency beyond the Ku‐band due to the limited permeability–bandwidth product. To address this, a custom‐fabricated CIP/epoxy‐based magnetic substrate is introduced, offering enhanced magnetic response. A thermoplastic polyurethane (TPU) layer and a resistor‐loaded frequency‐selective surface (FSS) are incorporated to implement admittance compensation, enabling broadband impedance matching. As a result, the proposed absorber achieves over 90% absorption from 12 to 49.8 GHz (122% fractional bandwidth) at a thickness of 1.8 mm (0.18 λ 0 ), maintaining stable performance under oblique TE and TM wave incidence. This design demonstrates near‐optimal absorption performance approaching the Rozanov limit and is well‐suited for millimeter‐wave applications.