Analysis of Transmission Characteristics of EBG Structures by Subgridding Unconditionally Stable FETD Method

Abstract

Subgridding unconditionally-stable finite-element time-domain method based on spatial modes filtering (SSMF-FETD) is combined with the Floquet theorem and used to analyze the transmission characteristics of 2-D dielectric pillar-array electromagnetic bandgap (EBG) structures with cross-section shapes of square and H. The computational stress is effectively reduced by exploiting the periodicity of the EBG structure and subgridding technique. Through the spatial modes filtering (SMF) method, the subgridding FETD (S-FETD) method is developed into the SSMF-FETD with larger time steps and higher computational efficiency. The effect of geometric and electromagnetic parameters on transmission characteristics of EBG structures are analyzed and compared in detail, the conclusions are as follows: the optimal filling ratio of the dielectric square-pillar EBG structure is 0.5, the composite H-pillar EBG structure has multiple bandgaps and can effectively save metal materials while satisfying the design requirements. The effect of electromagnetic parameters can be uniformly analyzed from the perspective of the average relative permittivity; with its increase, the central frequency of the bandgap becomes lower. It should be noted that the bandgap distribution and variation of composite H-pillar EBG structure are related to how its dielectric parameters change and combine. The results can serve as a reference for similar structures design.