On the Limitations of Equivalent Circuits for the Modeling of Periodic Structures

The use of equivalent circuits in the modeling of the scattering properties of frequency selective surfaces and other periodic structures provides a simplified and insightful approach to the involved original problem. Many of the equivalent circuits available in the literature are based on heuristic derivation of such circuits, which are valid over a given frequency range. However, some works are focused on the systematic derivation of the topology of the associated multi-modal equivalent network. In this work, the conditions under which these networks can be obtained are discussed in depth. The limits of validity of this approach are also considered.