This paper presents the design of 2.5D frequency selective surface (FSS) for X and Ku band applications. Proposed FSS's unit cell is constructed with two independent slitted rings on both side of the FR4 substrate and is connected with metallic vias. The FSS offers a wide stop band performance from 6.26 to 18 GHz, with a fractional bandwidth of 96.7% measured at S21 < −10 dB and has a low insertion loss (IL) of 0.018 dB. The footprint of the FSS is only about 0.11 with the shielding effectiveness of 83.365 dB, and the transverse electric and transverse magnetic mode performances are stable up to 70 degrees. Prototype FSS is fabricated and measured for its performance validation. The performance validation is carried out using applied wave research and the equivalent circuit model tools.

中文翻译：

---

适用于 X 和 Ku 波段应用的小型化 2.5D 频率选择表面设计

本文介绍了适用于 X 和 Ku 频段应用的 2.5D 频率选择表面 (FSS) 的设计。所提出的 FSS 单元由 FR4 基板两侧的两个独立的开缝环构成，并通过金属通孔连接。 FSS 提供 6.26 至 18 GHz 的宽阻带性能，在 S 下测得的分数带宽为 96.7%21< −10 dB，插入损耗 (IL) 低至 0.018 dB。 FSS的占地面积仅为0.11左右，屏蔽效能为83.365 dB，横向电模和横向磁模性能在高达70度的范围内保持稳定。原型 FSS 的制造和测量是为了验证其性能。使用应用波研究和等效电路模型工具进行性能验证。