Compact Bandpass Waveguide Filters with Capacitive or Mixed Couplings with E-plane Symmetry and without E-plane Symmetry

Recently, more and more stringent requirements for frequency response, as well as for weight and size characteristics, are imposed for input filters. Based on this, the designs of bandpass filters with capacitive and mixed couplings on corrugated waveguides are considered. Possible implementations of such filters on structures with and without symmetry of the electric field are presented. It is shown that for such filters it is possible to increase the slope of the performance below the passband. For filters with mixed (capacitive and inductive) couplings, the slope of the characteristic can be increased both below the passband and above. It is also shown that the implementation of capacitive couplings on stubs of the same cross section significantly increase the steepness below the passband. The possibility of implementing an ultra-compact waveguide bandpass filter with mixed couplings is shown. The frequency responses of the filters are given.