A frequency selective surface absorber for electromagnetic shielding in enclosed cabins
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摘要: 为了解决封闭舱室内反射型电磁屏蔽结构引起的电磁场水平易于升高的问题,提出了一种斜入射电磁波相位补偿频率选择表面(FSS)吸波体设计方法,并基于该方法设计了一款超宽带、角度稳定的FSS吸波型电磁屏蔽结构。利用吸波结构中不同介质层对斜入射时高频和低频的电磁波相位分别进行补偿,实现了宽频带内良好的角度稳定性。在此基础上,采用宽度渐变条带,并结合开缝和顶端加载技术设计出了新型十字FSS单元结构,有效拓展了该单层单谐振FSS吸波体的工作带宽。仿真结果表明,该结构90%吸波频带为3.9~25.8 GHz(相对带宽147.5%);在4.7~22.1 GHz(129.9%)频带内,两种极化下满足90%吸波率的角度稳定性达30°;即使斜入射增加到50°时,吸波率仍高于80%。对所设计的吸波体进行加工和测试,实验结果与仿真结果吻合良好,验证了设计的有效性。Abstract: This article proposes a phase compensation method for oblique incident electromagnetic wave to improve the angular stability of frequency selective surface (FSS) absorber. By using this method, an ultra-wideband, incident angle-stable FSS absorber-based electromagnetic shield structure is designed to reduce the electromagnetic environment level in enclosed cabins. The proposed single-layer FSS absorber achieves excellent angular stability within an ultrawide band by intentionally using different dielectric layers to compensate for the electromagnetic wave phase at high and low frequency bands respectively, and by designing a novel FSS cross unit cell featuring with gradually width-varying, slotted and top-loaded metallic strips. Simulation results reveal that the proposed absorber achieve over 90% absorption in the frequency range of 3.9−25.8 GHz, with a fractional bandwidth of 147.5%. In the frequency range of 4.7−22.1 GHz (129.9%), the angular stability of two polarizations reaches 30° with 90% absorptivity, and the absorptivity retains over 80% even when the incident angle increases up to 50°. The good agreement between the measurement and simulation results has verified the effectiveness of the design.
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Key words:
- frequency selective surface /
- absorber /
- ultra-wideband /
- angular stability /
- enclosed cabins
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表 1 FSS吸波体结构参数
Table 1. Structure parameters of the proposed FSS absorber
p/mm h1/mm h2/mm h3/mm h4/mm l1/mm l2/mm l3/mm 7.5 4.6 0.508 1.1 1.0 2.5 2.4 1.1 w1/mm w2/mm w3/mm w4/mm s1/mm s2/mm R/Ω 0.5 0.5 1.6 0.5 0.5 0.3 120 表 2 与其他FSS吸波体的仿真性能对比
Table 2. Simulation performance comparison with other FSS absorbers
references absorption band
(A>90%)/(GHz)FBW/% thickness/
λLangular stability
(A> 80%)number of lumped resistors
in the unit cellNum/Com Ref.[11] 4.7–16.75 112.4 0.103 30° * 8 1/No Ref.[12] 6.7–20.58 101.7 0.067 TE30°、TM45° 8 1/No Ref.[13] 2.7–12.7 130.0 0.084 40° 8 1/No Ref.[14] 2.24–11.4 134.3 0.075 45° 16 2/No Ref.[15] 3.87–14.84 117.0 0.190 TE40°、TM50° 8 2/No Ref.[17] 2.11–3.89 59.3 0.09 50° * 8 3D Ref.[18] 5.8–22.2 117.1 0.155 TE40°、TM50° * 16 1/Yes Ref.[20] 1.08–5.9 138.1 0.113 45° * 8 1/Yes Ref.[25] 3.58–12.1 108.7 0.077 30° 4 1/No this work 3.9–25.8 147.8 0.094 50° 4 1/Yes FBW : fractional bandwidth, FBW = 2(fh−fl)/(fh+fl); A : absorptivity; * : A> 90%; Num: number of lossy FSSs; Com: compensation layer. -
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