Abstract
A design method for a broadband and wide-angle metamaterial absorber is proposed based on optimal tiling of rhombus carbon pixels on and implantation of metal cylinders inside an acrylic substrate for which the backside is blocked by the perfect conductor. First, an intermediate carbon metapattern is achieved via optimal tiling of rhombus carbon pixels based on the genetic algorithm (GA), which can minimize the reflectances of both of the transverse electric (TE) and transverse magnetic (TM) polarized electromagnetic (EM) waves for the incident angles 0∘ and 60∘ simultaneously. Then, copper cylinders are implanted inside the substrate to boost the absorptions of both of the TE and TM polarizations for the 60∘ oblique incidences. To extend the absorption bandwidth, the design is finalized by evolving the intermediate metapattern using the GA. Based on the finalized carbon metapattern, the 90% absorption bandwidth is confirmed in the frequency range 8.8 to 11.6 GHz, for which the fractional bandwidth is 27.5% for both of the two polarizations with the incident angles from 0∘ to 60∘. The proposed method could open a way to design a broadband and wide-angle EM metamaterial absorber that can be applied to the edges of three-dimensional structures such as a regular tetrahedron or square pyramid that have interior angles of 60∘ that cannot be covered by conventional square or rectangular metamaterial absorbers.
Highlights
Electromagnetic (EM) metamaterials are engineered artificial structures that can realize untapped ranges of constitutive parameters such as negative permittivity and/or permeability [1,2,3]
To improve the accuracy of the final design, the 3D version of Figure 2b, the carbon metapattern combined with the copper cylinders, is solved while the results shown in Figure 2c are based on the 2D version
A design for a broadband and wide-angle hexagonal metamaterial absorber was proposed based on the optimal tiling of rhombus carbon pixels using the genetic algorithm (GA) and implantation of copper cylinders inside the acrylic substrate
Summary
Electromagnetic (EM) metamaterials are engineered artificial structures that can realize untapped ranges of constitutive parameters such as negative permittivity and/or permeability [1,2,3]. Because it is impossible to tile the square or rectangular unit cells continuously near the edges of the structures, the periodic condition for the metamaterial absorber may not be satisfied, which is assumed in the design and necessary to realize the original performance of it. Even though hexagonal EM metamaterial [15,30] or frequency selective surface (FSS) [32] absorbers have been reported utilizing a dual-electric resonator [15], tiling of hexagonal carbon pixels [30], and resistively loaded quadruple hexagonal loops [32], there exist limitations that the absorption bandwidths of them are quite narrow especially for oblique incidences. A design method for a hexagonal metamaterial absorber is proposed that optimally tiles rhombus carbon pixels on an acrylic substrate of which the backside is blocked by the perfect conductor (PEC). Based on the full-wave simulation, the 90% absorption bandwidth is confirmed from 8.8 to 11.6 GHz, of which the fractional bandwidth is 27.5% for both of the TE and TM polarizations with the incident angles from 0◦ to 60◦
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