Microwave absorption of λ∕4 wave absorbers using high permeability magnetic composites in quasimicrowave frequency band
Microwave absorption of λ∕4 wave absorbers using high permeability magnetic composites in quasimicrowave frequency band
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DOI：
10.1063/1.2830827
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发表时间：
2008-02
影响因子：
3.2
通讯作者：
Kyung-Sub Lee;Y. Yun;Sang Woo Kim;Sung Soo Kim
中科院分区：
文献类型：
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作者：
Kyung-Sub Lee;Y. Yun;Sang Woo Kim;Sung Soo Kim
针对准微波频段薄吸波材料的需求，提出了一种高导磁率的四分之一波长厚度（λ/4间隔层）的磁性复合材料薄片，其表面涂有377 Ω/sq的电阻膜（阻抗Transformer）。对于λ/4垫片，采用Fe？采用传统的磁性复合材料制备技术制备了Si9.5Al5.5片状颗粒在橡胶基体中的定向排列.由于复合材料的高磁导率和高介电常数，λ/4厚度可以在2 μ m内降低到0.5 μ m。磁性复合片的微波吸收率（在2 μ m处测定）在λ/4厚度为0.5 μ m时为-4.6 μ m（65%功率吸收）。通过在λ/4间隔物（厚度= 0.5 μ m）上涂覆导电膏（分散在聚合物树脂基体中的石墨和炭黑），微波吸收率大大提高。当涂膜的薄层电阻接近377 Ω/sq时，反射损耗降低到-11 Ω（90%功率吸收）。这是由于自由空间阻抗的电阻膜与λ/4厚的高导磁间隔层相结合所导致的波阻抗匹配。因此，提出了具有可控的电性能和厚度的电阻膜/磁性复合结构可以用作准微波频段的薄微波吸收体。
For the aim of thin electromagnetic wave absorbers used in quasi-microwave frequency band, this study proposes the high-permeability magnetic composite sheets of quarter wavelength thickness (λ/4 spacer) coated with resistive film of 377 Ω/sq (impedance transformer). For the λ/4 spacer, flexible magnetic composite sheets of Fe??Si 9.5 Al 5.5 flake particles aligned in rubber matrix are prepared by conventional magnetic composite fabrication technique. Due to high permeability and high permittivity of the composite sheets, λ/4 thickness can be reduced as low as 0.5 ㎜ in 2 ㎓. The microwave absorbance (determined at 2 ㎓) of the magnetic composite sheets are found to be -4.6 ㏈ (65% power absorption) at a λ/4 thickness of 0.5 ㎜. By coating the conductive paste (graphite and carbon black dispersed in polymer resin matrix) on the λ/4 spacer (thickness = 0.5㎜), the microwave absorbance is greatly improved. When the sheet resistance of coated films is close to 377 Ω/sq, the reflection loss is reduced to -11 ㏈ (90% power absorption). This is attributed to the wave impedance matching led by the resistive film of free-space impedance combined with a λ/4 thickness of high-permeability magnetic spacer. It is, therefore, proposed that the resistive film/magnetic composite structure with controlled electrical properties and thickness can be useful as thin microwave absorbers used in quasi-microwave frequency band.