A Tunable Cut-off Frequency Band-pass Filter Based on SSPPs

In this paper, a tunable band-pass filter based on SSPPs is designed. The band-pass filter is obtained by cascading a tunable low-pass filter and a high-pass filter. The tunable low-pass filter is obtained by loading varactor-controlled branches on the passive SSPPs filter, which shows different dispersion characteristics and cut-off frequency under different capacitances. By adjusting the reverse bias voltage of the varactor, the cut-off frequency of the low-pass filter can be adjusted. The tunable high-pass filter is a fifth-order high-pass filter with transmission zeros controlled by varactors. The high-pass cut-off frequency can be tuned by adjusting the transmission zeros. The simulated results show that the upper cut-off frequency of the BPF can be tuned from 5.57 GHz to 7.54 GHz, and the lower cut-off frequency can be tuned from 2.60GHz to 3.73GHz.