A Compact and Narrow-Band Bandpass Filter Based on Spoof Surface Plasmon Polaritons

This paper presents a compact and narrow-band bandpass filter (BPF). The spoof surface plasmon polaritons (SSPP) waveguide structure based on 3-D silicon process can be folded in space, and its electrical size can be decreased significantly. The asymptotic frequency of the proposed structure is 71.8% lower than that of the traditional rectangular groove structure with the same geometry. A compact narrow-band BPF can be obtained by combining the proposed SSPP structure with half-mode substrate integrated waveguide (HMSIW). The filter operates in the frequency range of 5.43-6.8GHz with a center frequency of 6.115 GHz, and its electrical size is 0.206λg × 0.037λg.