A Design of Wideband Bandpass Three-Dimensional Frequency Selective Surface

A wideband bandpass 3-D frequency selective surface (3-D FSS) which has Chebyshev frequency response and the equivalent transmission line (TL) model of 3-D FSS are presented in this paper. We use the synthetic method proposed by Bo Li and Lei Zhu to design a 3-D FSS in 5 GHz to 14 GHz. The in-band equal-ripple return loss (RL) and the fractional bandwidth (FBW) are selected as 15 dB and 100% and the parameters of the equivalent circuit can be calculated by synthetic design procedure. The unit cell of 3-D FSS is formed of three stepped impedance slotlines which are coupled by two short-ended parallel-coupled sections and two back-side copper strips. The physical parameters of slotlines can be obtained from calculated impedances by executing the extraction method. Printing unit cells in long printed circuit board (PCB) pieces periodically and stacking them with a certain distance, we can establish this 3-D FSS. The S-parameters of 3-D FSS are analyzed and compared with theoretical S-parameters. Besides, we simulated and analyzed the S-parameters under different incident angles.