Absorptive Frequency-Selective Reflection/Transmission Structures: A Review and Future Perspectives

Absorptive frequency-selective reflection/transmission (AFSR/T) structures, which have been recently described in the literature, are different from traditional frequency-selective structures (FSS) due to their unique responses. The AFSR structure has a reflection band with one- or two-sided absorption bands, while the AFST structure has a transmission band within a wide absorption band. In this article, we present a comprehensive literature review, demonstrate new designs, and propose future perspectives. The review of AFSR structures is divided into several parts: structures with single and multiple reflection bands, structures that use lumped resistors and commercial absorbers, and structures integrated with an antenna to achieve an antenna system with a low out-of-band radar cross section (RCS). For AFST structures, the review is mainly concerned about their response through the use of one-sided upper/lower absorption bands, two-sided absorption bands, and a tunable design. In addition, the techniques used in the literature to bypass losses are mentioned. The limitations of the reported structures are listed, and future perspectives are provided at the end of this article.