A Hybrid 2-D–3-D Miniaturized Multiorder Wide Bandpass FSS

In this letter, a hybrid multiorder wide bandpass frequency selective surface (FSS) with high selectivity and low insertion loss is achieved by combining the two-dimensional (2-D) FSS structure and the 3-D vertical structure. The 3-D periodic vertical printed circuit board pieces (PVPCB) are used as the dielectric layer in the unit cell to achieve a proper band flatness without introducing great insertion loss. The multiorder response of the proposed FSS is achieved using a series of 3-D PVPCB instead of stacking the 2-D FSS layers. The proposed FSS unit cell is constructed by combining the full-wave and equivalent circuit simulations, since the physical structures have a good one-to-one correspondence with the circuit elements. The module design method is used to accelerate the design procedure, and the simulation result proves the effectiveness of this design method. Finally, the prototype is fabricated and measured to prove the effectiveness of the proposed FSS. The measured relative bandwidth and rectangle coefficient achieved is 130.4% and 0.76, respectively. The measured maximum insertion loss over the whole passband is 0.7 dB. Because of its strong capability of out-of-band rejection, the proposed FSS structure is a good candidate to enhance high-frequency electromagnetic pulse protection of wideband radar systems.