Numerical Analysis of Electromagnetic Bandgap Structures

摘要

Electromagnetic bandgap (EBG) structures and negative index of refraction (NIR) meta-materials are periodic dielectric or metallic material structures that allow greater control over electromagnetic waves than has previously been possible. Man-made versions of these materials block the propagation of electromagnetic waves within particular frequency bands and allow propagation only in certain spatial directions (Fig. 1). They are scalable and operate over a wide range of frequencies. These qualities are very desirable for a variety of applications such as radar, communication devices, and sensors. Traditionally, the analysis of the electromagnetic properties of EBG materials relied heavily on the mathematics of infinite periodic structures, similar to that used to describe crystal diffraction. However, for real applications, the finite dimensions, lattice defects, and boundaries have to be included in the analysis to account for their impact on the bandgap characteristics. To accomplish this requires a direct numerical simulation of the finite EBG structure. We have used a Finite-Difference Time-Domain (FDTD) numerical code to design and characterize EBG structures and to analyze the electromagnetic performance of finite EBG structures at microwave frequencies. This code allows us to directly view the time evolution of the fields in these materials. The FDTD approach is useful for optimization of EBG parameters and can facilitate the design in many emerging applications.