Fast design of cross-coupled filter substructures

Cross-coupled narrow bandpass filters with asymmetric transmission zeros can be realized in cascaded tri-section topology.(1,2,3) Each tri-section creates a single transmission zero below or above the passband. The realization of resonator tri-sections is relatively difficult due to the interaction between the couplings. This article shows ow three-dimensional electromagnetic (3D-EM) analysis, together with extraction of an equivalent circuit model, can speed up the realization process of cascaded tri-section bandpass filters.