Analysis of Composite Right/Left-Handed Unit Cells Based on Even–Odd-Mode Excitation

Even-odd-mode analysis is applied to symmetric composite right/left-handed (CRLH) structures in order to decompose the network into the two impedances Z_e and Z_o. It is shown that these impedances are sufficient to completely describe the behavior of arbitrary symmetric CRLH structures. Consequently, the propagation constant, as well as the Bloch impedance, are derived based on Z_e and Z_o. Furthermore, the balancing condition, as well as the band limits, are formulated in terms of poles and zeros of Z_e and Z_o . This simplifies significantly the analysis and design process of unit cells, especially when the structure comprises transmission lines. The theoretical expectations are validated by circuit simulations and electromagnetic simulations, as well as measurements of fabricated prototypes.