This article presents the design of a novel miniaturized 2.5D frequency selective surface (FSS) for radiofrequency and microwave shielding applications is proposed. The proposed FSS is configured to offer multiple band‐stop characteristics with a wide frequency ratio. The unit cell is developed using traces that run on the top and bottom layers of the substrate with traces connected using vias. This proposed unit cell structure provides distinct operating modes at high and low frequencies. The proposed FSS unit cell has a compact geometry with a foot‐print of 0.059λo × 0.059λo where λo is the freespace wavelength. The FSS unit cell is polarization insensitive and exhibits good angular stability up to 45°. A prototype FSS is fabricated to validate the simulation results. The miniaturized FSS can be used as a shield at terrestrial frequencies and satellite frequencies making it usable for both indoor and outdoor environments.

The design and characterization of a multiband THz metamaterial are reported in this article. The proposed metamaterial is constructed over the polyimide substrate embedded with a novel ring-shaped frequency-sensitive copper trace on the top providing the desired frequency response. The proposed metamaterial is developed from a unit cell with a base cross shape. The arms of the cross shape are deployed with three folded circular resonators providing the desired frequency-selective property. The proposed metamaterial offers band-stop characteristics at 0.83, 2.15, 2.91, 4.1, and 4.86 THz. The proposed unit cell metamaterial has the smallest foot-print of 0.089λ o  0.089λ o where λ o is the free-space wavelength. The electric field distribution and surface current contours are used to describe the operation of the proposed metamaterial. The proposed metamaterial has a symmetric configuration resulting in a polarizationindependent operation. The angular stability of the proposed metamaterial is investigated by subjecting the metamaterial to the various oblique incidence of THz radiation. The proposed THz metamaterial unit cell is suitable for THz imaging and spectroscopy applications.

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