A Generalized and Efficient Equivalent Circuit Model for Frequency Selective Surfaces

Owing to their excellent intuitiveness and simplicity, equivalent circuit models (ECMs) are widely used to investigate and design frequency selective surfaces (FSSs). However, the generalization and accuracy of ECM has been a contentious issue, especially with regard to the requirement for analyzing diverse and numerous FSSs versus the restrictions applied to it. To address this problem, a generalized and efficient equivalent circuit model (GE-ECM), characterized by the feasibility of dealing with multiple sizes, broadband, and large oblique incidences, is proposed in this study to design FSSs and analyze their electromagnetic performance. In contrast to related works, gap and width factors are accounted for in the proposed GE-ECM to recalibrate the reactance and susceptance of the physical model, respectively. Additionally, normalized sizes of structure periods are introduced to further extend its generalization. Good agreement is achieved between the frequency responses of the GE-ECM and the electromagnetic software CST. Furthermore, excellent adaptation to multiple sizes and broadband is achieved from 0 GHz to 20 GHz, with the average relative error of the resonant frequency being only 1.19% for all sizes. Fabrication and measurements were conducted to verify the practicability of the proposed GE-ECM, with all results confirming its accuracy and universality in interpreting electromagnetic performance, thus establishing a reliable theoretical guideline for designing more complex FSSs.