Wave Propagation in 1D EBGs: Periodic Multilayer Films Consisting of Two Different Materials [This Issue's Contribution

Abstract

This paper presents the fundamental concept of wave propagation in periodic multilayer films consisting of two different materials, so-called one-dimensional electromagnetic bandgap (EBG) materials. To this end, Floquet's theorem is first presented. Next, the transmission-line analogy is used to simplify the concept of wave propagation in one dimension. The Bloch impedance concept is then presented, and its usefulness is illustrated in the applications of truncated periodic structures. Through a few case studies, it is shown that the ripples usually appearing in the pass band of the EBGs are due to the mismatch of the transmission-line ports. When the EBG structures are terminated to appropriate Bloch impedances, the ripples disappear. The material can be used in undergraduate or graduate Microwave or Advanced Engineering Electromagnetics courses. The students need to know about the ABCD matrix in advance. The material helps students in better understanding of microwave filters, and shows the importance of matching the terminal ports and number of unit cells. Students can use software packages such as MATLAB to obtain the Bloch impedances, and such as Ansoft HFSS to reproduce the scattering parameters presented in this paper. The materials in this paper are consistent with those in [3, 7, 8, 9] and, in some cases, are summarized from these references to improve the clarity.