折射率正负梯度交替表面的研究

利用不均匀材料提出了一种折射率正负梯度交替表面, 并利用几何光学法和电磁场数值仿真方法对其机理进行了研究与验证, 发现其可以操控电磁波的传播: 在一定的参数下, 其可以将空间中的入射电磁波一直束缚在介质中, 或在介质中传播一定距离后再实现电磁波的释放; 同时该结构具有宽带、极化无关等特性. 利用该结构可引导能流, 减小后向散射截面, 可用作隐身表面.     

Tri-band transparent cross-polarization converters using a chiral metasurface

A chiral metasurface is proposed to realize a tri-band polarization angle insensitive cross-polarization converter. The unit cell of the chiral metamaterial is composed by four twisted anisotropic structure pairs in four-fold rotation symmetry.The simulation results show that this device can work at 9.824 GHz, 11.39 GHz, and 13.37 GHz with low loss and a high polarization conversion ratio(PCR) of more than 99%. The proposed design can transmit the co-polarization wave at14.215 GHz, like a frequency selective surface. The study of the current and electric fields distributions indicates that the cross-polarization transmission is due to electric dipole coupling.     

基于宽边耦合螺旋结构的低频小型化极化不敏感超材料吸波体

设计、仿真并实验验证了基于宽边耦合螺旋结构的低频小型化超材料吸波体. 实验测试结果表明, 该超材料吸波体在1.39 GHz吸收率达到最大为98%, 其单元尺寸和总厚度均为6.8 mm, 约为1/32工作波长, 实现小型化窄带吸波. 由于吸波体中螺旋结构是旋转对称排列的, 因而其对垂直入射电磁波的极化方向是不敏感的. 此外, 该超材料吸波体对斜入射横电和横磁极化电磁波在60°时, 仍具有强吸收. 关键词： 超材料 吸波体 小型化     

Polarization-insensitive unidirectional spoof surface plasmon polaritons coupling by gradient metasurface

A polarization-insensitive unidirectional spoof surface plasmon polariton(SPP) coupler mediated by a gradient metasurface is proposed. The field distributions and average Poynting vector of the coupled spoof SPPs are analyzed. The simulated and experimental results support the theoretical analysis and indicate that the designed gradient metasurface can couple both the parallel-polarized and normally-polarized incident waves to the spoof SPPs propagating in the same direction at about 5 GHz.     

宽带透射吸收极化无关超材料吸波体

提出了一种新的基于磁性吸波体材料的具有低频透射和高频宽带吸收特性的超材料吸波体.该超材料吸波体在1 GHz的透射系数为-0.5 dB,具有较好的低频透射特性,可以实现对低频信号的相互通信;在频率大于8.4 GHz的频段,吸收率均大于80%,基本覆盖整个X波段和Ku波段,实现高频宽带吸收.此外,由于该超材料吸波体的单元金属周期结构具有较好的四重旋转对称性,因而是极化无关的.该透射吸收超材料吸波体设计简单,实用性强,具有较强的潜在应用价值.     

折射率梯度表面机理的研究

本文构建了一种折射率梯度表面,并利用几何光学法对其物理机理作了研究,发现这种折射率梯度表面可以实现入射波到正常反射波,异常反射波,以及介质波的转换.当入射点介质折射率大于某一阈值时,异常反射波束方向角正弦值与入射波束方向角正弦值存在线性关系,意味着平行入射的波经介质后将平行出射到空气;而当折射率梯度常数大于某一阈值时,任何方向入射的波在透射到介质后,将发生全反射,被束缚在介质中.总而言之,通过调节结构参数,可以实现对波束方向与强度的人工调控,从而提供了一种人工可控的全介质梯度表面的工程实现思路.     

Ultra-broadband and high-efficiency polarization conversion metasurface with multiple plasmon resonance modes

In this paper, we present a novel metasurface design that achieves a high-efficiency ultra-broadband cross polarization conversion. The metasurface is composed of an array of unit resonators, each of which combines an H-shaped structure and two rectangular metallic patches. Different plasmon resonance modes are excited in unit resonators and allow the polarization states to be manipulated. The bandwidth of the cross polarization converter is 82% of the central frequency,covering the range from 15.7 GHz to 37.5 GHz. The conversion efficiency of the innovative new design is higher than 90%.At 14.43 GHz and 40.95 GHz, the linearly polarized incident wave is converted into a circularly polarized wave.