太赫兹科学与电子信息学报  2020, Vol. 18 Issue (6): 974-978     DOI: 10.11805/TKYDA2019307

Polarization-insensitive broadband metamaterial absorber based on electric dipole resonance
CHEN Chen, TIAN Lihua
Brainware Terahertz Information Technology Co., Ltd, The No. 38 Institute, CETC, Hefei Anhui 230088, China
Abstract: Based on electric dipole resonance, a polarization-insensitive broadband metamaterial absorber in W-band is designed. The broadband metamaterial with highly symmetric structure, is composed of the periodic arrays of copper with different sizes. Absorption performance of metamaterial in W band is simulated by Finite Difference Time Domain(FDTD) method, and the physical mechanism of resonance absorption is discussed through electric field and charge distribution. The metamaterial is implemented by Printed Circuit Board(PCB), and the experimental results of absorption are compared with simulation. Experimental results show that the average absorption rate of the metamaterial in W band reaches 84.7%, which is close to the simulation results.
Keywords: metamaterial    perfect absorption    polarization

1 设计与建模

 Fig.1 Unit cell of metamaterial absorber 图 1 吸波超材料的结构单元

 $A = 1 - R = 1 - {S_{11}}$ (1)

 $\Delta = \frac{{\mathop \smallint \nolimits_{110}^{75} A\left( f \right){\rm{d}}f}}{{\left( {{F_1} - {F_2}} \right) \times 1}} \times 100{\rm{\% }}$ (2)

F1=110 GHz，F2=75 GHz时，根据式(2)可计算出超材料在W波段的平均吸收率。

2 结果与讨论

 Fig.2 Reflectance and absorbance of periodic arrays based on unit cell with only single square copper plate 图 2 结构单元中只包含一种正方形铜箔的周期阵列的反射和吸收关系

 Fig.3 At 76.6 GHz, distribution of electric field and charge density, and distribution of magnetic field and surface current 图 3 在76.6 GHz下，单元上表面的电场分布和电荷密度分布，以及单元剖面的磁场分布和表面电流分布

 Fig.4 Absorbance of square copper periodic arrays with different lengths 图 4 不同边长的正方形铜箔周期阵列的吸收关系

 $\stackrel{\rightharpoonup }{{\boldsymbol{E}}_{\text{i}}}=\widehat{u}{E}_{\text{i}u}{\text{e}}^{\text{i}φ }+\widehat{v}{E}_{\text{i}v}{\text{e}}^{\text{i}{\rm{φ}}}$ (3)
 Fig.5 Vector component, and absorbance of periodic arrays including copper plates of four sizes 图 5 矢量分解及包含四种铜箔的周期阵列的吸收关系

 Fig.6 Distribution of surface electric field of unit cell at f1−f5 图 6 频率f1~f5下结构单元表面电场分布

 Fig.7 Absorbance under different polarization angles and different incident angles 图 7 不同极化角度和不同入射角度对应的吸收关系

 Fig.8 Sample, reflectance measurement, comparison of reflectance and absorbance between experiment and simulation 图 8 样品及局部细节(b)反射率测量示意仿真和实验关于(c)反射率及(d)吸收率的结果对比

3 结论