This paper presents a new compact ultra-thin triple-band absorber which shows near-unity absorption in C, X and Ku-bands. It consists of an inductive stub loaded circular ring resonator and a flower-shaped resonating patch on top of 0.8 mm thin FR-4 grounded dielectric substrate. A transmission line equivalent is proposed, and circuit simulation response is in good agreement with the full-wave analysis. The unit-cell architect's 4fold symmetry makes it polarisation-insensitive for different polarisation angles in the azimuthal plane (𝜃 = 0°) under normal incidence. Its good shows angular stability up to 45° under TE (75° under TM) incidences for all three frequencies. Surface current patterns are analysed at resonant frequencies to illustrate the mechanism behind the electromagnetic absorption. This design's novelty lies in the centre patch's dual-resonating behaviour, making this design compacted one. The absorber has low-profile nature with cell periodicity of 0.163λ_L and thickness 0.013λ_L, where λ_L is the lowest resonating peak wavelength. An X-band conventional MSA is fabricated on a thin FR-4 substrate. In-band RCS reduction (nearly 18 dBsm) of the antenna is verified after loading with the proposed absorber. The absorptivity peaks are optimised such that the same structure would be used in different applications like RF energy harvesting, RCS reduction and sensor applications.

中文翻译：

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用于射频能量收集、RCS 减少和传感器应用的紧凑型偏振不敏感宽角稳定三频吸收器

本文提出了一种新型紧凑型超薄三频吸收器，它在 C、X 和 Ku 波段显示出接近统一的吸收。它由一个电感短截线加载的圆环谐振器和一个位于 0.8 mm 薄 FR-4 接地介电基板顶部的花形谐振贴片组成。提出了传输线等效电路，电路仿真响应与全波分析非常吻合。晶胞结构的 4 重对称性使其在垂直入射下对方位平面 (𝜃 = 0°) 中的不同偏振角不敏感。对于所有三个频率，其良好的角度稳定性在 TE（在 TM 下为 75°）入射下高达 45°。在共振频率下分析表面电流模式以说明电磁吸收背后的机制。这个设计' 新颖之处在于中心贴片的双共振行为，使这种设计更加紧凑。吸收体具有低剖面特性，单元周期为 0.163λ _L和厚度 0.013 λ _L，其中λ _L是最低谐振峰值波长。X 波段常规 MSA 是在薄的 FR-4 基板上制造的。加载建议的吸收器后，验证了天线的带内 RCS 降低（近 18 dBsm）。吸收率峰值经过优化，因此相同的结构可用于不同的应用，如射频能量收集、RCS 减少和传感器应用。