An ultrathin and simple three-dimensional (3-D) frequency-selective rasorber with a passband located between two absorption bands is proposed. The absorption bands are obtained by employing commercial magnetic materials in the absorption channel and the passband is realized using epsilon-near-zero tunneling waveguides. The attractively ultrathin and simple feature is achieved by utilizing tunneling effect at the cutoff frequency of metallic waveguides with arbitrary length, permitting the overall thickness shrink into the same as that of the absorber. A prototype with a thickness of only 0.108 λc (λc is the free-space wavelength at the transmission frequency) is fabricated and measured, exhibiting a transmission band with −3 dB fractional bandwidth (FBW) of 35.7% and a minimum insertion loss of 1 dB, and an FBW of 135.6% for reflection coefficient less than −10 dB. The lumped-components-free and lithography-free features greatly facilitate the fabrication, which is promising in practical low-cost applications.

中文翻译：

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基于铁氧体并嵌入 Epsilon 近零波导的超薄简单 3D 吸收器


提出了一种超薄且简单的三维（3-D）频率选择吸收器，其通带位于两个吸收带之间。吸收带是通过在吸收通道中采用商业磁性材料获得的，通带是使用ε-近零隧道波导实现的。利用任意长度金属波导在截止频率下的隧道效应，使整体厚度缩小到与吸波体相同，从而实现了超薄且简单的吸引人的特性。制作并测量了厚度仅为 0.108 λc（λc 是传输频率下的自由空间波长）的原型，其传输频带的 −3 dB 分数带宽 (FBW) 为 35.7%，最小插入损耗为 1 dB，反射系数小于-10 dB 时，FBW 为 135.6%。无集总元件和免光刻的特点极大地方便了制造，这在实际的低成本应用中很有前景。