基于电阻膜与分形频率选择表面的超薄宽频带超材料吸波体的设计

Design of an ultrathin and wideband metamaterial absorber based on resistance film and fractal frequency selective surface

设计了一种基于一阶Minkowski分形双方环(Minkowski fractal double square loop,MFDSL)电谐振器结构与电阻膜复合的超薄、宽频带、极化不敏感和宽入射角的超材料吸波体.该吸波体的基本结构单元由MFDSL电谐振器结构、方块电阻膜、电介质基板和金属背板组成.采用时域有限差分算法对这种复合结构吸波体的电磁波吸收特性进行数值模拟分析.模拟得到的反射率和吸收率表明:该吸波体在7.5—42GHz之间对入射电磁波具有大于90%以上的强吸收特性.模拟得到的不同极化角和不同入射角下的吸收率表明:该吸波体具有极化不敏感和宽入射角特性.进一步的数值模拟结果表明,该复合结构吸波体对电磁波的吸收主要是基于电磁谐振和电路谐振机制,通过方块电阻的设计可以实现工作频率范围的调节.

An ultrathin, wideband, polarization-insensitive and wide-angle metamaterial absorber is presented, which is based on one order Minkowski fractal double square loop （MFDSL） electric resonator structure and resistance film. The unit cell of this absorber consists of MFDSL, square resistance film, dielectric substrate and metal ground plane. The simulations and analyses of electromagnetic absorbing properties of this composite structure absorber are performed by the finite-difference time-domain method. The simulated reflection and absorption indicate that the absorption of the composed structure absorber is greater than 90% in a frequency range of 7.5--42 GHz. The simulated absorptions under different polarization conditions and incident angles indicate that this composite structure absorber is polarization-insensitive and of wide-angle. The further numerical simulation results indicate that the absorption of this absorber originates mainly from the absorbing mechanism of electromagnetic resonance and circuit resonance, the operation frequency range can also be adjusted by the design of the square resistance.