Spoof Plasmonic-Based Band-Pass Filter With High Selectivity and Wide Rejection Bandwidth

In this letter, we report the design theory and analysis of an end-coupled broadband spoof plasmonic based band-pass filter (BPF) at sub-wavelength scale enabled by multi-mode grooved stepped impedance resonators (GSIRs) at THz frequency regime. The proposed GSIRs are end-coupled to each other and externally coupled to the source and load through spoof surface plasmon polaritons (SPP)-based transmission line. The designed filter has 3-dB bandwidth of 0.35 THz (from 0.17 THz to 0.52 THz) and fractional bandwidth (FBW) of 87.85%, respectively, with the shape factor of 1.35. The simulated transmission and reflection coefficients in the pass-band of proposed filter are better than ~6 dB and 15 dB respectively. Also, 60 dB spurious rejection bandwidth of the designed filter in the upper stop-band is 1.3 THz (0.62-1.92 THz). For the validation of the proposed approach, similar design is implemented at microwave frequency due to the geometrical dependence feature of spoof SPP and its S-parameters response is presented. Such broadband BPF will pave a path to design and development of advanced integrated plasmonic circuits and systems for high-speed and low-loss THz wireless communication applications.