A Convoluted Structure for Miniaturized Frequency Selective Surface and Its Equivalent Circuit for Optimization Design

A convoluted frequency selective surface (FSS) is proposed to provide the unit cell dimension as small as 4.84% of the free space wavelength at resonant frequency. The FSS exhibits high resonant stability for various polarizations and incident angles. Its simple geometry is beneficial for not only easy design but also realizing the single and dual bandpass performances. By introducing an inductance in series connected with the traditional LC parallel resonant circuit, an improved equivalent circuit is established, which can describe the FSS frequency responses more accurately. Furthermore, a set of closed forms related to circuit and dimension parameters are developed. It can serve as the substitute of the full-wave solver to enhance the FSS design efficiency significantly. Finally, a dual bandpass FSS operating at 2.5 and 4.95 GHz was fabricated and measured. The measurement results exhibit satisfactory consistency with the full-wave simulation results.