An angular-stable miniaturized frequency selective surface with controllable frequency band ratio using lumped elements

A novel dual-band miniaturized-element frequency selective surface (MEFSS) using lumped elements is proposed to achieve angular-stable response and controllable frequency band ratio. The MEFSS consists of two metal layers of the same period for the unit cell. The operating principle and the synthesis procedure of the MEFSS are analyzed based on the equivalent circuit model. The prototype of the MEFSS is simulated, fabricated, and tested, and the simulation results have a good agreement with the measurement results. To further reduce the element size and achieve a controllable band ratio, inductors and capacitors are, respectively, loaded on the top layer and the bottom layer of interlayer substrate to decrease the resonant frequency. Choosing the values of loaded lumped components properly, the resonance frequencies and the band ratio can be controlled. The unit size of this modified MEFSS is consumedly miniaturized to 0.0015λ0×0.0015λ0$ 0.0015 \ \lambda_{0} \times 0.0015 \ \lambda_{0} $, where λ0$ \lambda_{0} $ represents the resonance wavelength in free space. Compared to the previous works, the proposed MEFSS has a better miniaturization performance. The results show that the modified dual-band MEFSS has a large band ratio and high stability in the scope of incidence angles of 80° for TE and TM polarization.