A Generalized Approach for Frequency Selective Absorber with Controllable Center Frequency and Passband Bandwidth

In this paper, we propose the generalized approach for a dual absorption frequency selective absorber (FSA) with controllable center frequency and passband bandwidth. The designed dual absorption FSA consists of a lossy layer and a frequency selective surface (FSS) layer. Furthermore, the lossy layer is composed of a square ring loaded with four resistors, four circular patches, and four interconnected patches, while the lossless layer is composed of four circular grooves. As for the operating mechanism, the center frequency of the transmission characteristics is mainly determined by the radius of the circular patch (‘a’), while the bandwidth of the transmission characteristics is mainly influenced by the angle of interconnected patch (‘θ’). Then, the generalized approach for dual absorption FSA with controllable center frequency and passband bandwidth was proposed, which could provide effective guidance for the design of dual absorption FSA. To verify the presented concept and design method, the dual absorption FSA was fabricated and measured. Experimental measurements demonstrate a −3 dB transmission fractional bandwidth of approximately 10.74%. Moreover, the proposed structure achieves an absorption rate of over 80% across the 2.95–7.00 GHz band and more than 72% absorption over the 7.80–10.20 GHz band.