Dual-mode realisations for asymmetric filter characteristics

Techniques for using asymmetric filtering characteristics with dual mode cavities and irises in microwave communications systems are presented. Consideration is given to the axial inclination of the cylindrical cavities and irises relative to each other. A review of symmetric dual mode filter principles is outlined, and coupling matrices are defined for asymmetric characteristics. A single-slot offset-iris solution for 4th and 6th degree asymmetric characteristics is found and input/output waveguide alignment in each case is described. Results with a laboratory model 4th degree device, featuring a dual TE/III/-mode bandpass filter, a center frequency of 14125 MHz, and a bandwidth of 80 MHz, are reported. Only moderate increases in industrial production efforts are noted to be required for realization of the filters.