A low-cost bandpass filter based on hybrid spoof plasmonic waveguides

We propose a hybrid guided structure consisting of a rectangular waveguide loaded with channel-shaped and its complementary wedge-shaped metallic pillars that supports spoof plasmonic guided modes. The complementary structure is used in order to gain better control over tuning of the asymptotic frequency in the spoof plasmonic waveguide. As a proof of concept, a tunable microwave bandpass filter based on the proposed spoof plasmonic waveguide is fabricated and tested. Measurement and simulation results of the filter response are in excellent agreement with 14% bandwidth at the center frequency of 11 GHz and a maximum 0.7-dB insertion loss. The channel-shaped structure results in a passband frequency response with minimum ripple and the double-sided complementary pillars cause smaller bandwidth and more tunability.