Design of an optimal multi-layered electromagnetic absorber through the central force optimization algorithm

Electromagnetic absorbers are elements designed to avoid (or at least reduce) reflection of electromagnetic energy in a given frequency band, which could otherwise be harmful to living beings, or simply cause interference with other electronic equipment. Thus, this article presents the results achieved by using a metaheuristic for optimizing their design in the frequency range of wireless communications, i.e., between 0.8 and 1.9 GHz. In this case, the algorithm proposed by Formato in 2007, i.e., Central Force Optimization (CFO), was used. Moreover, the approach laid out by Qubati and Dib in 2010, i.e., acceleration clipping, was also implemented. Results are compared between these two variants, and using different initial distributions (i.e., uniform, mixed, and random). Furthermore, a two-stage process was executed, striving to reduce the number of dimensions of the problem, thus allowing for further optimization. In the first stage of this procedure, all unknowns were considered (i.e., two variables for each layer, each one representing a given material and its thickness), and the algorithm was run 10 times. During the second stage, the materials of the best run were fixed, and the algorithm was also executed 10 times, just that in this case it only had to operate on half of the dimensions (i.e., one for each layer, which represents the fixed material thickness). It was found that, for a three layered electromagnetic absorber, better results than previously reported ones for Particle Swarm Optimization (PSO) and for interval analysis, were possible, though only for the modified CFO algorithm.