Yi Jianjia, Campbell Sawyer D, Feng Rui, Burokur Shah Nawaz, Werner Douglas H
Opt Express. 2018 Jan 8;26(1):505-515. doi: 10.1364/OE.26.000505.
Complex electromagnetic structures can be designed by exploiting the concept of spatial coordinate transformations. In this paper, we define a coordinate transformation scheme that enables one to taper the electric field between two waveguides of different cross-sections. The electromagnetic field launched from the wide input waveguide is compressed in the proposed field tapering device and guided into the narrow output waveguide. In closed rectangular waveguide configurations, the taper can further play the role of a mode selector due to the output waveguide's cut-off frequency. Realizable permittivity and permeability values that can be achieved with common existing metamaterials are determined from the transformation equations and simplified by a proposed parameter reduction method. Both a 2D continuous design model and a potential 3D discretized realization model are presented at microwave frequencies and the performances of the tapering devices are verified by full-wave finite element numerical simulations. Finally, near-field distributions are shown to demonstrate the field tapering functionality.
通过利用空间坐标变换的概念,可以设计出复杂的电磁结构。在本文中,我们定义了一种坐标变换方案,该方案能够使人们在两个不同横截面的波导之间对电场进行渐变。从宽输入波导发射的电磁场在提出的场渐变装置中被压缩,并被引导到窄输出波导中。在封闭矩形波导配置中,由于输出波导的截止频率,渐变还可以进一步起到模式选择器的作用。根据变换方程确定了现有常见超材料可实现的介电常数和磁导率值,并通过提出的参数约简方法进行了简化。在微波频率下给出了二维连续设计模型和潜在的三维离散化实现模型,并通过全波有限元数值模拟验证了渐变装置的性能。最后,展示了近场分布以证明场渐变功能。