Characteristic Mode-Based Resonance Model for Analyzing and Designing Reconfigurable Frequency-Selective Surfaces

A novel resonance model is formulated to evaluate the resonance properties of frequency-selective surfaces (FSSs) using characteristic modes (CMs). This CM-based resonance model, derived from the Poynting theorem, extends its application to accommodate reconfigurable frequency-selective surfaces (RFSSs) by integrating the equivalent circuit of diodes into the impedance matrix of the method of moments. The model not only provides a well-defined physical interpretation with the CMs but also enhances the analysis and design process of FSSs through insightful field perspectives. To illustrate the proposed CM-based resonance model, we exemplify band-stop and band-pass properties using two types of dipole structures, where the substructure impedance matrix transformation is used to account for the interelements coupling. The model is validated through comprehensive full-wave simulation results. Next, a single-layer triband RFSS is further designed with the aid of the formulated model. Prototypes are fabricated and subjected to measurements, revealing good agreement between simulations and experimental results. The confirmed usefulness in guiding the RFSS design of the proposed resonance model is expected to be of potential application in EMI shielding.