Design and Performance of a Double-Layer Miniaturized-Element Frequency Selective Surface

In this letter, a novel bandpass frequency selective surface (FSS) is proposed. Unlike the traditional FSSs, our building block makes use of a periodic cell with much smaller size than the resonant wavelength. The proposed FSS is composed by two layers of metallic unit cells printed on the substrate. The coupling between parallel patches in different metallic layers can produce the significant distributed capacitance of the FSS; as a result, the size of the FSS unit cell can be decreased to λ/16. Our simulated result shows that the transmission characteristic of the miniaturized FSS is very stable since the relative change rate of resonant frequency is less than 2% with respect to different incident angles from 0^° to 45^° . The measured results show good agreements with the simulated ones. In addition, our result also implies that the structure has wide application space, based on analysis of three other variations on the periodic structure.