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.