Design of Multiband Filter Based on Spoof Surface Plasmon Polaritons

In this paper, a multiband filter with notch function based on spoof surface plasmon polaritons (SSPPs) is designed. First, a gradualy slot unit structure is introduced into the waveguide structure to obtain better dispersion characteristics, and a low-pass filter with a cut-off frequency of 7.1 GHz is built on this basis. Then, the multiband filter is formed though exciting the stuffing wave by loading an E-shaped resonator. When the odd and even resonance modes arc excited at the same time, two low-pass filters with insertion loss of 3 dB and cut-off frequency of 2.83 GHz and two band-pass filters with insertion loss of 3 dB and bandwidth of 2.94-4.37 GHz and 4.40-7.10 GHz arc formed. When the resonance degradation disappears in even mode, a low-pass filter with 3 dB insertion loss and 2.83 GHz cut-pass frequency, and a band-pass filter with insertion loss of 3 dB and bandwidth of 2.94-7.10 GHz arc formed. It is proved that the structure of multiband filter based on E-shaped resonator is of great significance to the development of SSPPs in microwave field in the microwave field.