Design Method for Topological Waveguides by Using Two Types of Rhombic Composite Right/Left-Handed Transmission-Lines

The design method for topological waveguides is presented based on the transmission-line (TL) theory of metamaterials. Two types of rhombic composite right/left-handed (CRLH) TLs are proposed and the conditions for designing topological waveguides are stated. Circuit parameters are chosen according to the conditions and those frequency dispersion characteristics are calculated by using the theoretical formulas. The designed two rhombic CRLH TLs are arranged periodically at two areas, respectively, and a topological waveguide is constituted on the zigzag boundary between those. The operation is verified by circuit simulations and the validity of the design method is demonstrated from the results.