ELLIPTIC CAVITY RESONATORS FOR DUAL-MODE NARROW-BAND-FILTERS

A novel cavity resonator with elliptical cross section is proposed in order to realize dual-mode narrow-band filters without tuning and coup ling elements, The absence of any discontinuity inside the cavities si gnificantly enhances the unloaded Q, the ability to operate with highe r power levels, and the ease of manufacturing. Proper choice of the el lipticity and of the inclination angle controls the desired coupling a nd tuning actions. Dual-mode coupling is generated by the step discont inuity between the input rectangular waveguide and an inclined ellipti cal waveguide, A rigorous full-wave electromagnetic model for this dis continuity. has been developed and validated using a specialized hardw are configuration, Experimental data compare very favorably with theor etical results, Representative prototypes of elliptical cavities exhib iting various degrees of coupling have been carefully measured proving the accuracy of the model and its applicability for narrow-band X- an d K u-band filter design. The full-wave analysis of a complete four-po le narrow-band elliptic filter at 12 GHz and the measured response of a corresponding prototype demonstrate the capability of achieving reli able results using the proposed approach.