Ultrathin and flexible broadband metamaterial absorber for Ka-band applications

This paper presents an ultrathin and flexible metamaterial absorber (MA) for Ka-band applications. The MA with a five-layer structure is composed of three copper layers separated by two FR4 dielectric layers. Due to the use of ultrathin but robust FR4, the thickness of the proposed MA is only 0.35 mm corresponding to 0.035 λ at the operating frequency range. The MA can achieve absorptivity of over 95% in the frequency band of 30-36 GHz. The investigation of electric field distribution is used to interpret the absorption mechanism. Additionally, the MA exhibits excellent polarization and angular stability. A prototype of the proposed MA was fabricated using PCB technology. The measured results of absorption performance agree well with the simulated ones, thereby demonstrating the validity of the design. More importantly, the absorption performance of the flexible MA in bent states is examined, proving the feasibility of the MA for conformal applications. This work provides a good candidate for electromagnetic (EM) shielding at Ka-band.