Frequency-Selective Rasorber with a Wide High-Transmission Passband Based on Multiple Coplanar Parallel Resonances

A dual-polarized frequency-selective rasorber (FSR) with a wide high-transmission passband and two absorption bands is proposed and investigated in this letter. The proposed FSR, is composed of a lossy and a lossless layer, is formed by introducing a broadband transmission window into a wider absorption band. Simple guidelines based on an impedance analysis are proposed, and the wide high-transmission passband is realized by connecting multiple coplanar parallel resonances (MCPRs) in a series, which introduces a large impedance in a wide band for the lossy layer. In this design, the lossy layer and lossless layer consist of a square ring absorber with multiple interdigital resonators and a multilayer broadband frequency selective surface, respectively. The simulation results indicate that the 1 dB transmission window can be obtained from 8.12 to 11 GHz with a 30.4% fractional bandwidth, and the bandwidth of reflection below –10 dB is up to 111% from 4 to 14 GHz. Finally, the proposed structure is fabricated and measured. Both the simulation and experimental results agree well, which suggests that the concept of connecting MCPRs in series can generate a broadband transmission window effectively.