Modeling and Analysis of Miniaturized Frequency-Selective Surface Based on 2.5-Dimensional Closed Loop With Additional Transmission Pole

The 2.5-dimensional closed loop is investigated to constitute a novel miniaturized frequency-selective surface (FSS) whose electric size of one unit cell is as small as 0.048 λ
₀
× 0.048 λ
₀
. For miniaturization, two pairs of orthogonal split square rings are connected in series by four vias array in the FSS unit cell. Thus, this FSS exhibits polarized insensitivity for different incident angles. An equivalent circuit model is implemented to give a physical insight of the working mechanism of the proposed miniaturized FSS. Moreover, the transmission zero and transmission pole are discussed by the full-wave simulations and equivalent circuit model. The additional transmission pole can be used to improve the sharp frequency-selective performance of the proposed miniaturized FSS. The results show a good consistency between the simulation, modeling, and measurement.