A Novel Design of 5G Band Multi-Mode Dielectric Filter with Symmetrical Zeros

A 5G band dielectric filter with symmetrical zero is designed in this paper. The metal cylinder is used to change the electric field distribution of the mode, then the mutual coupling between the modes is realized. The effect of two coupled degenerate modes is equivalent to two coupled resonators, so one dual-mode resonator can realize the filtering characteristics of two single-mode resonators. The 5G band dielectric filter of China Telecom is designed by using single cavity and dual-mode, and two transmission zeros are realized on both sides of the passband to improve the out-band suppression ability. The results show that in the pass-band (3.4 ~ 3.5 GHz), the return loss is larger than 16.8 dB, the insertion loss is less than 0.35 dB, the zero point on the left side of the pass-band is 3.182 GHz, the zero point on the right side of the pass-band is 3.842 GHz, and the standing wave ratio is less than 1.27. All results prove its excellent performance and can be applied to 5G systems well.