Use of frequency-selective surfaces (FSSs) is proposed to shield rooms against electromagnetic fields in order to achieve secure indoor communications and reduce human exposure to external fields. The secure room is designed using two-layer FSSs with an FR4 substrate to cover 10–12 GHz frequency band. Different elements in each layer and shift in the position of elements are the reasons for more than 3 GHz bandwidths in X band. The performance of the structure is also stable versus the misaligned position of layers. An equivalent circuit model is proposed for the structure and results show −20 dB isolation between inside and outside of the room in the desired frequency band. Bio tissue is located inside the cubic structure with FSS walls and the results of the specific absorption rate are demonstrated and compared in two rooms with FSS cover on concrete walls and a room with concrete walls. The 17 × 17 cm2 two-layer FSS is fabricated for the measurement and the results are presented. The designed FSS can be used in the construction of wave-isolated room for any application.
