Ultra‐miniaturized and angularly stable symmetric polarization insensitive frequency selective surface for electromagnetic shielding

Summary This research work presents a miniaturized enhanced angular and polarization stability frequency selective surface (FSS) structure at 660 MHz for electromagnetic (EM) shielding of 4G LTE networks. The vias and spiral‐shaped subunit cells are combined to extend the electrical path length corresponding to the lower resonant frequency. The symmetric structure is considered to improve polarization and angular stability. Two symmetric metallic layers are etched on both sides of the FR4 substrate with thickness h=1.6mm and relative permittivity εr=4.4. Four steps are adopted to improve miniaturization and stability (angular and polarization). The dimension of the unit cell is 0.016λ02. The figure of merit is also improved to λ0P=59.49, where λ0 is the largest free space wavelength and P is the periodicity of the proposed structure. The proposed band‐stop FSS is more angularly stable as a figure of merit for various incidence angles under transverse electric (TE) and transverse magnetic (TM) polarizations. Simulation and measurement have been done to confirm the polarization insensitivity and maximum angular stability of 80°. The proposed design and transmission coefficient of all the unit cells under normal incidence in steps 1–4 is demonstrated in (a) and (b) in the given figure. From the results, it can be realized that the perimeter of each unit cell is gradually increasing corresponding to the left shift of resonant frequency. The operating frequency is left shifted from 4.56 to 0.66 GHz consequently increasing the path length from 29.6 to 327.2 mm. The designing steps corresponding to the response with applications are demonstrated in the given table.