Generation of dual-band rejection filtering function in two frequency bands developed by spoof surface plasmon polaritons

Abstract

In this paper, we propose the generation of dual-band rejection filters based on the interaction between spoof surface plasmon polaritons transmission line and -type resonator cells. By selecting a suitable value of spacing inside them, the -type resonator cells generate excellent dual-band band rejection filter on combining with spoof SPP transmission line in lower frequency band. A simple parametric calculation based on varying the value of spacing inside -type resonator cells, has been performed for the conversion of dual-band band rejection filter from lower frequency band to higher frequency band. Greater value of spacing results in larger LC coupling which deteriorate filtering performance by leaving us with dual-band rejection filtering function in lower frequency band. By choosing smaller value of spacing converts it into dual-band rejection filtering function in upper frequency band because of significant reduction in LC coupling, and hence leading to much improved broadband filtering performance. In short, the formation of dual-band rejection filter in lower frequency band and its conversion into dual-band rejection filter in upper frequency band can be fully controlled by just adjusting the value of vertical width inside -type resonator cells. The simulation results demonstrate the outstanding performance of the proposed filters and can play a crucial role in developing integrated plasmonic circuits at microwave and terahertz frequencies.