Reflective frequency selective absorber based on computational pixelated metasurface

A reflective frequency selective absorber (RFSA) using computational pixelated structure is proposed. The RFSA consists of a high-impedance ITO conductive film covered with a polyethylene terephthalate (PET) dielectric layer and a resonant cavity. The resonant cavity is a three-layer structure with a metal pattern and a fully reflective metal film on and at the back of a PET dielectric layer, respectively, which produces an in-phase total reflection. The metal pattern is formed by pixelated and binary square with a value of 1 or 0 to indicate whether it is metallized. Coherent perfect absorption (CPA) can thus be achieved by the in-phase total reflection from the resonant cavity combined with the high-impedance ITO film. A reflection coefficient lower than -10 dB from 11 to 13 GHz and greater than -1 dB from 14.6 to 16.3 GHz with a minimum insertion loss of -0.45 dB at 15.5 GHz is achieved based on computational pixelated metasurface and CPA. Moreover, based on the same thickness of the layered structure, tunability of the absorption bands and reflective notch is achieved by changing only the dimension and arrangement of the pixels based on simulated annealing algorithm and CST Microwave Studio for fully automated inverse topology optimization. The proposed method provides a flexible and convenient way to realize frequency selective absorbers which is of great significance in manipulation of electromagnetic radiation, microwave detection and shielding.