A transparent ultra-broadband microwave absorber based on flexible multilayer structure

In this work, a transparent ultra-broadband microwave absorber (MA) based on flexible multilayer structure was demonstrated. The designed resonant structure consists of a resistive film pattern of indium tin oxide (ITO) on a flexible substrate PET. By adjusting the size of the resonant layer ITO pattern and the array position arrangement, an ultra-broadband absorption of over 90% is achieved in the frequency range 8.6–75.8 GHz, with a relative absorption bandwidth of 159%. At the same time, the transparent flexible medium polydimethy-lsiloxane (PDMS) and PET substrate are used to obtain good optical transmittance. Due to the quadruple symmetry of the resistive film resonance pattern, MA shows high polarization insensitivity. For TE and TM polarised waves, the proposed MA can maintain an absorption rate greater than 80% as the angle of incidence is increased to 40°. The current distribution of each resonant layer at strong resonant frequency is simulated and analysed to determine the absorption mechanism of MA. A sample consisting of 11 × 11 cells was produced and the experimental measurements were in general consistent with the numerical simulation results. Due to its ultra-wideband absorption characteristics and wide incident angle stability, it has potential application value in the fields of radar stealth system and transparent electromagnetic shielding.