Design of a Miniaturized 2.5-D Frequency Selective Surface With Angular Incidence and Polarization Stability

In this article, a miniaturized 2.5-D frequency selective surface with the band-stop response at 900 MHz is presented. The proposed FSS unit cell comprises rectangular spiral elements printed on both sides of the dielectric substrate. These spirals are connected with plated through-hole vias to form a “2.5-D closed loop”. The large perimeter of the closed loop increases the effective inductance and causes a reduction in resonant frequency and size of the unit cell. The structure is designed to operate at 900 MHz for shielding the interference from other GSM sources. The size of the proposed unit cell is 0.021λ
₀
× 0.021λ
₀
which is very compact with a figure-of-merit λ
₀
/p = 47.6, where λ
₀
is the free-space wavelength of resonant frequency andp is the periodicity of unit cell. Further, the effect of substrate parameters on resonance performance has been studied. The proposed structure is polarization-independent and angularly stable for both TE and TM polarizations. A prototype of the FSS is fabricated and measured, where the measured responses show good agreement with the simulated responses.