Design of Six-cavity Ceramic Waveguide Filter with Four Transmission Zeros

In this paper, a six-cavity double CQ structure is designed by sharing the second, fifth resonant cavities and the capacitive coupling structure between the two cavities. Then diagonal coupling is introduced into CQ coupling unit, and the positions of transmission zeros are adjusted by changing the diagonal coupling amount, so as to improve the out-of-band suppression characteristics of the filter. On this basis, a six-cavity ceramic waveguide filter with four transmission zeros is designed. In the optimization process of the filter, the influence of the length change of the through slots L1 and L2 on the positions of transmission zeros is discussed in detail, and the related change rules are given. After simulation and optimization, all the performances of the filter meet the performance requirements of the 5G base station filter, which has a good application prospect.