Design of Broadband and Wide-Angle Hexagonal Metamaterial Absorber Based on Optimal Tiling of Rhombus Carbon Pixels and Implantation of Copper Cylinders

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.

Miniaturized square fractal ring patch unit cell for active reflective metasurface in C‐ and X‐bands

“…To determine the dimensions of the proposed square fractal ring, GA is adopted, which is a stochastic optimizer mimicking the meiosis of the chromosome. [18][19][20] To this end, random bit arrays composed of 29 bits, that is, zero or one, are generated. The number of random bit arrays is the same as that of the array's bits.…”

“…The condition may guarantee sufficient diversity of the generated random bit arrays. 19,20 The 29 bits are composed of three bytes, including 8 bits each and a byte containing 5 bits. The former three bytes are matched with the geometric parameters of the square fractal ring l, h, and g, and the last one is matched with w. The bytes can be decoded into decimal numbers.…”

“…22 After selecting two-bit arrays, GA is applied to them, and new 29 bit arrays are produced to repeat the competitive process. First, the crossing operation of GA [18][19][20] is applied seven times, approximately a quarter of the number of bits included in an array. The process is repeated until 29 new bit arrays are produced.…”

“…The process is repeated until 29 new bit arrays are produced. Next, the mutating operation of GA [18][19][20] is applied twice on each bit array produced by the previous process. Then, a pair of the two-bit arrays is selected among 29-bit arrays via the same competitive process based on FOM.…”

“…Optimal dimensions of the square fractal ring are determined via the genetic algorithm (GA). [18][19][20] The proposed design provides ∘ 180 phase differences of the reflection coefficients between on and off states of the PIN diode at both C-and X-bands center frequencies. The accuracy of the proposed dualband reflective metasurface unit cell is verified by comparing simulations with measurements inside the C-and X-bands rectangular waveguides.…”