A compact ultra-wideband frequency selective rasorber (CUWFSR) with hybrid two-dimensional (2-D) and 3-D structure is proposed in this letter. The wide absorption band is obtained by the multiple resonances excited by two dipole resonators and the hybrid structure. By inserting split-ring resonator into the short dipole to bypassing the losses in the passband, an FSR with an internal transmission window and ultrawideband absorption performance is finally realized. The proposed rasorber shows a fractional bandwidth of 140.8% with a transparent window from 14.2–15.8 GHz. Then an improved design which involves two approaches of bypassing the losses of the lossy layer is also provided. Finally, an FSR with a middle passband at 15 GHz and a fractional bandwidth of 137.3% for the absorption rate better than 90% is achieved. The prototype of the improved CUWFSR is fabricated and measured for validation.

中文翻译：

---

具有混合二维和三维结构的紧凑型超宽带频率选择吸收器

本文提出了一种具有混合二维 (2-D) 和 3-D 结构的紧凑型超宽带频率选择性吸收器 (CUWFSR)。宽吸收带是由两个偶极子谐振器和混合结构激发的多重谐振获得的。通过在短偶极子中插入裂环谐振器绕过通带损耗，最终实现了具有内部传输窗口和超宽带吸收性能的FSR。所提出的吸收器显示出 140.8% 的部分带宽，具有 14.2-15.8 GHz 的透明窗口。然后还提供了一种改进的设计，该设计涉及绕过有损层的损失的两种方法。最后，实现了具有 15 GHz 中通带和 137.3% 的部分带宽的 FSR，其吸收率优于 90%。