3-D absorptive frequency selective reflector based on slotlines

This paper presents an absorptive frequency selective reflector (AFSR), which exhibits a flat reflection characteristic with absorption at the both sides of the reflection band. This structure formed in planar slotline structures is mainly inclusive of one lossless resonator and two lossy resonators, which are responsible for one reflection band and two absorption bands respectively. In order to minimize the coupling of these three resonators, metallic plates are utilized to make these three resonators separated. In this paper, equivalent circuit model (ECM) based on transmission line theory is introduced to describe the design concept. Then, the realization of specified structure is provided, where a good agreement of reflection coefficient results between EM simulation and ECM is achieved. The proposed AFSR features stable performance under oblique incident angles up to 40°.