A low-profile angle-insensitive bandpass frequency-selective surface based on vias

In this letter, a low-profile bandpass frequency-selective surface (FSS) that is independent of incident angle and polarization is proposed. This FSS is composed of two identical metallic convoluted cross slot layers with vertical metal vias. The whole structure is ultrathin with a thickness of 0.042λ, where X represents the resonant wavelength in free space. This FSS works as a spatial bandpass filter and exhibits great resonant stability with incident angle ranging from 0° (normal incident) to 75° for both transverse electric (TE) and transverse magnetic (TM) polarizations. At 75° oblique incidence, the resonant frequency deviation is about 0% and 2.02% for TE and TM polarizations, respectively. To verify the design, a prototype of the FSS was fabricated. The measured transmission responses agree reasonably with that of the simulated ones.