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A simple and compact terahertz (THz) frequency selective surface (FSS) with high selectivity is presented for the cases of normal incidence. The guidelines for the design along with the operation mechanism are presented in detail from the view of equivalent circuit. The design is implemented by mapping the lumped components in a topology circuit of microwave filter with two transmission zeros to structures of FSS, while the mapping is realized by slotting cross-shaped aperture in the grid. An intensive study on equivalent circuit model predicts the existence of transmission zeros and poles. It can afford two transmission zeros and two transmission poles ranging from 350 GHz to 450 GHz with the band separation of 1.05 and 1.07, thereby exhibiting fast roll-off characteristics. The two transmission zeros can be controlled independently by simply changing structure parameters of the unit cell. The proposed FSS is superior in terms of roll-off rate as well as the balance between selectivity and overall thickness. The measured results of the prototype are consistent with the simulation results, which validates the robustness of the design.

An ultra‐wideband metamaterial absorber (MA) is proposed for 5G communication, which features a resistive frequency selective surface printed on a PET (polyethylene terephthalate) layer and a ground layer of resistive film. The proposed MA can provide over 90% absorptivity in the frequency range of 11.2–42.8 GHz. Moreover, it is insensitive to polarization and wide incident angles. The effective medium theory and multi‐reflection interference theory are used to interpret the broadband absorption mechanism. The surface current distribution at three absorption peaks is investigated to further study the physical mechanism behind the wideband absorption. The measured results of the fabricated prototype are in good agreement with the simulation ones, thus verifying the robustness of the design. The presented MA can probably be used in electromagnetic shielding of 5G signals.