Design of Pattern-independent Ultra-Wideband Frequency Selective Surfaces with Single-layer Metal by Characteristic Mode Analysis

A pattern-independent ultra-wideband frequency-selective surface (FSS) with a dielectricmetal-dielectric sandwich structure is proposed. Characteristic mode analysis indicates that the bandwidth of the excited modes increases with thickness. Then, a single-layer ultra-wideband FSS with ≥ 80% fractional bandwidth (|S21| ≥ -3 dB) is designed, which is independent of metal patterns. The single-layer metal sandwich design can mitigate aperture field distortions, thus improving the boresight error and power transmission. Finally, miniaturized design is introduced to suppress harmonics at angles of incidence up to 60°. A prototype of the proposed miniaturized FSS is fabricated and the measurement agrees well with the simulation. The proposed design can be a desirable scheme for broadband antennas enclosed by stealth radomes.