A broadband reconfigurable bandpass filter based on half-mode substrate integrated waveguide and spoof surface plasmon polarization structure

In this paper, a design method of reconfigurable broadband bandpass filter, with the advantage of adjustable bandwidth, is proposed by fabricating a hybrid sharing waveguide which is consist of half mode substrate integrated waveguide (HMSIW) and spoof surface plasmon polarization (SSPP). By adding a U-shaped resonant unit and a container structure to the bandpass filter, then through the movement of the slide on U-shaped groove and the alteration of the medium parameters in the container, the lower cut-off frequency of HMSIW and upper cut-off frequency of SSPP can be independently controlled by the fine tuning of the structures easily without changing the filter parameters. A prototype sample is fabricated to demonstrate and confirm the validity of the proposed method. The measured largest passband ranges from 11.5 to 14.5 GHz with the relative bandwidth of 23% which can be adjusted within a certain scope. The design of reconfigurable filter is realizing by the combination of HMSIW-SSPP structure and the concept of tunable filter. The proposed method can be used to develop different broadband bandpass filters.