Band rejection filter based on a composite spoof surface plasmon periodic structure

Abstract

Research has demonstrated how the interaction between electromagnetic fields and specially tailored sub wavelength metallic structures leads to unique properties such as strong confinement of electromagnetic fields and backward wave propagation. Various designs of surface plasmon (SP) propagation wave-guides in the microwave and terahertz frequency regime employing corrugated ultra-thin periodic metallic unit structures have been reported, however SP wave guides employing a combination of different unit cells have not been experimentally demonstrated to the best of our knowledge. In this paper, we propose a novel composite HO2-type ultrathin metallic structure to produce a band-stop spoof SP (SSP) based filter. The proposed structure's SSP wave guide is composed of periodic H and slot-type unit cell structures. The SSP structure is fed from a CPW transmission line through a transition matching structure composed of gradient corrugated grooves and Vivaldi curves to match both the wave number and impedance of the SSP wave guide. Simulation results show excellent band stop filtering performance of the proposed design. In addition, the dispersion analysis of the proposed composite wave guide revealed that the proposed SSP waveguide can support backward wave propagation of surface plasmons. With such unique properties the proposed composite SSP wave-guide has potential in new applications of plasmonic meta-material in integrated microwave circuits.