A Novel Dual-Passband Spoof Surface Plasmon Polariton Filter with Wide Upper Out-of-Band Suppression

In this paper, a dual-passband filter with wide upper out-of-band suppression is designed by combining the double-sided parallel symmetric spoof surface plasmon polariton (SSPP) transmission line with a dual-band filtering structure. The dispersion and transmission characteristics of this structure are analyzed. Through the control of key parameters, the edge positions of the passbands can be independently adjusted. The results show that the lower passband ranges from 2.2 to 3.5 GHz with a relative bandwidth of 45.6%, and the upper passband ranges from 6.5 to 7.4 GHz with a relative bandwidth of 13%. The transmission coefficient is less than -40 dB in the frequency range of 9.7 - 30.2 GHz outside the upper passband. It has important reference value for the development of miniaturized, multifunctional and highly integrated radio frequency devices in modern communication systems.