A Novel Compact Dual-Band Bandpass Waveguide Filter

A novel design of second-order dual-band H-plane bandpass waveguide filter is presented in this paper. Filter design is relatively simple and is based on the use of complementary split ring resonators, implemented as metal septa, with properly shaped slots, in the transverse planes of the standard (WR-90) rectangular waveguide. The positions of the resonators on the same septum are chosen in such a manner that there is no mutual coupling between them. This approach is used for the design of the waveguide resonator with two resonant frequencies (9 GHz and 11 GHz). Further, the second-order dual-band bandpass waveguide filter, with symmetrically positioned folded septa, is presented. The equivalent circuits of the considered resonators and filters are developed. The proposed dual-band bandpass filter design is verified by a good agreement of the filter responses obtained for three-dimensional electromagnetic models and equivalent microwave circuits. Finally, the method for filter miniaturization is introduced and applied to the second-order dual-band filter. The required filter response is preserved.