Miniaturized Dual-Band Waveguide Filter Using TM Dielectric-Loaded Dual-Mode Cavities

In this letter a class of very compact dual-band band-pass filters based on TM dual-mode cavities loaded with high permittivity dielectric is presented. Filters consist of cascaded doublets resulting in in-line structures with a high degree of design modularity where each doublet is designed separately. Each doublet provides two poles and two transmission zeros resulting in a filter with an equal number of poles and zeros. Zeros can be placed in both the lower and upper stop-bands as well as between the two pass-bands to increase their insulation. The feasibility of the proposed approach is demonstrated through the design and manufacturing of a 6th order dual-band filter with central frequencies at 4.25 and 4.55 GHz having six transmission zeros.