Fast design of cross-coupled filter substructures

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