W-Band Bandpass Filter Using Spoof Surface Plasmon Polaritons and Double-Grating Rectangular Waveguide

A hybrid circuit with spoof surface plasmon polaritons (SSPPs) and double-grating rectangular waveguide (DG-RWG) is proposed to design a bandpass filter (BPF) operating at ${W}$ -band. The proposed SSPPs consisting of corrugated metallic blocks are embedded into the RWG, which forms a hybrid SSPP-RWG. Both the dispersion curves of the SSPP-RWG and DG-RWG are analyzed. The lower cut-off frequency of DG-RWG and the upper cut-off frequency of SSPP-RWG can be controlled independently by changing their geometric parameters, thus the hybrid circuit composed of DG-RWG and SSPP-RWG is attractive to design a BPF with tunable bandwidth. For demonstration, a ${W}$ -band RWG BPF is designed and fabricated with measured bandwidth from 80.1 to 93.8 GHz, which agrees well with that in the dispersion curves. The BPF has a low insertion loss of about 0.57 dB at the center frequency.