Bandwidth for the Equivalent Circuit Model in Square-Loop Frequency Selective Surfaces

• Published in: IEEE transactions on antennas and propagation 2017-11, Vol.65 (11), p.5932-5939
• Main Authors: Rodriguez Barrera, Mario A., Pereira Carpes, Walter
• Format: Article
• Language: English
• Subjects: Bandwidth; dielectric effective permittivity; Dielectrics; Electronic countermeasures; equivalent circuit model (ECM); Equivalent circuits; Frequency selective surfaces; frequency-selective surfaces (FSSs); matrix cascading technique (MCT); particle swarm optimization (PSO); Permittivity; Resonant frequency
• ISSN: 0018-926X; 1558-2221
• DOI: 10.1109/TAP.2017.2754418

This paper presents the results of a study, implemented for the equivalent circuit model (ECM), concerning the bandwidth in square-loop frequency-selective surfaces (FSSs). For the square-loop ECM, there is no formulation to quantify the effects of dielectric supporting layers, geometric features, and incident wave properties on the FSS bandwidth. Hence, it is not possible to control or evaluate the bandwidth of the FSS in the design from the knowledge of these parameters. In this paper, we addressed this issue using the ECM as an analysis method. In the first part of this study, we considered the square-loop FSS with thin dielectric supporting layers, where the bandwidth was expressed as a function of geometric parameters, incidence angle, and polarization of the incident wave as well as a factor that takes into account the effective permittivity of the dielectric support. Particle swarm optimization method was used to synthesize square-loop FSSs via the ECM with a specific resonant frequency and bandwidth requirements. In the second part, the behavior of bandwidth as a function of dielectric thickness was obtained by using a matrix cascading technique (MCT), implemented with ECM and a model for the dielectric effective permittivity. This approach takes into account the modifications on bandwidth due to multiple reflections on dielectric boundaries and allows calculating its value for any dielectric thickness and configuration. It is remarkable the low computational cost and acceptable accuracy obtained with the proposed approaches. All simulation results using ECM and MCT were compared with Ansys-HFSS commercial software simulations.