Modal Analysis of Chiral Metamaterial Using Characteristic Mode Analysis and Eigenmode Expansion Method

A chiral metamaterial (MTM) is analyzed using two modal analysis methods: characteristic mode analysis (CMA) and Eigenmode expansion method (EEM). Chiral MTMs are commonly associated to antennas and other microwave devices due to their ability to interact with electromagnetic waves and alter their polarizations. Here, the interaction of a chiral helix with linearly polarized electromagnetic plane waves is studied and asymmetric transmission is demonstrated. The different metrics given by CMA and EEM are analyzed and compared. It is shown that the modal weighing coefficient is a good metric to analyze the chiral properties of the MTM, and these results are validated using a full-wave approach. It is also shown that if the two modal approaches propose very close results qualitatively, the maximum value of the modal current density obtained by EEM is closer to the one obtained by full-wave simulations. The modal approaches presented to analyze chiral MTM can be applied for the analysis of circularly polarized chiral MTM-inspired antennas.