A novel and ultra-compact plasmonic filter with a fully controlled rejection band

In this article, we propose a novel approach to develop an ultra-compact spoof surface plasmon polariton (SSPP) band-rejection filter by loading T-shaped grooves on the SSPP transmission line (TL). This scheme is based on the interaction between two types of grooves, i.e. rectangular grooves of the SSPP TL and T-shaped grooves. This form of interaction has never been addressed before in order to achieve a highly efficient SSPP band-rejection filter. The working principle of this band-rejection filter is clearly revealed via investigation of the dispersion behavior of the SSPP TL in the presence and absence of T-shaped groove loading. Meanwhile, we simulate an SSPP TL loaded with T-shaped grooves. As proof of concept, we fabricate the filter in the microwave regime and perform an experiment which characterizes its functionality. The simulated and experimental results confirm the excellent filtering phenomena exhibited by our structure. The isolation of the filter can be less than -15 dB at rejection frequencies with excellent transmission efficiency in both passbands, before and after the rejection band. Furthermore, simulated near-electric-field results are also presented to demonstrate the authenticity of the filter. When the question of generating a highly efficient SSPP band-rejection filter arises, the proposed method facilitates us with T-shaped grooves, which are declared as an excellent alternative to metamaterial particles in this regard. The proposed band-rejection filter based on SSPPs demonstrates an outstanding capability to take part in the progress and the advancement of integrated plasmonic structures and systems at microwave frequencies.