Elektromanyetik hüzme üretimi için sıfıra yakın indisli kabukların tasarımı, simülasyonu ve ölçümü

In this study, design and simulation of three-dimensional (3D) shell structures, which generate directional radiation patterns from isotropic sources, with near-zero-index (NZI) characteristics, as well as their realizations via low-cost 3D printing are presented. Throughout the design process of NZI beam generators, both homogenized structures, in which near-zero relative permittivity and/or permeability values are enforced, and actual models involving periodic arrangements of dielectric rods are examined. The solutions of electromagnetic problems are obtained by using rigorous implementations of novel surface-integral-equation (SIE) formulations in frequency domain. Iterative solutions of matrix equations derived from SIEs are accelerated by different forms of the multilevel fast multipole algorithm (MLFMA) and suitable preconditioners, when necessary. First, reflection and refraction properties of NZI media are extensively examined to obtain efficient structures in the intended frequency regimes. Then, alternative strategies are employed to obtain customized radiation patterns. In this context, various cavities with strong resonance behaviors are designed as source regions of the shells. At the same time, outer surfaces are modified to either enhance or suppress outgoing electromagnetic fields. In addition to comprehensive simulations and analyses of NZI beam generators, their effective capabilities are verified by measurements on different prototypes fabricated via 3D printing. In order to realize NZI properties efficiently via dielectric rods, various 3D printing materials are extensively investigated by an electromagnetic characterization setup. Measurements of diverse NZI shell structures are presented to demonstrate that NZI properties are successfully achieved by well-designed arrangements of dielectric rods with proper materials. The results demonstrate the feasibility of efficient, effective, low-cost, and reconfigurable NZI shells to generate alternative beam configurations that can be useful in a plethora of microwave applications.