A Wideband Low-Pass Frequency Selective Surface With Sharp Roll-Off and Extensive Deep Stopband

This paper presents a wideband lowpass frequency selective surface (FSS) with wide stopband of deep rejection and sharp roll-off for high selectivity. The proposed structure employs a triple-layer structural configuration separated by two supporting honeycomb layers, which facilitates the strategic distribution of three transmission poles and four transmission zeros, enabling high frequency selectivity and wide stopband performance. An equivalent circuit model is developed to elucidate the operational mechanism, showing excellent agreement with full-wave simulations. The FSS exhibits a low insertion loss of less than 1.67 dB within the lowpass band up to 12.26 GHz, while maintaining a transmission coefficient below -10 dB from 12.45 GHz to 21.11 GHz. A remarkably narrow transition band of only 160 MHz between -3 dB and -10 dB underscores its steep roll-off characteristic. A prototype is fabricated and measured, demonstrating good agreement with simulations and stable performance under both TE and TM polarizations for incident angles up to 45°.