A four-pole dual mode elliptic filter realized in circular cavity without screws

A 4-pole filter displaying an elliptic type response and implemented in circular cavity without tuning screws is presented. The cavity employs a novel arrangement, consisting of the insertion of a short length of inclined rectangular waveguide in the middle of the cavity body, in order to obtain the desired coupling and tuning actions. A full-wave model of the complete filter has been developed and specialized pretuning techniques are used. The measured response of a breadboard channel filter operating at Ku-Band shows good agreement with computed data and proves the proposed approach to be valid and viable.