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

A four-pole dual mode elliptic filter is realized in circular cavity without screws. The desired coupling and tuning actions are achieved by using a novel arrangement consisting in the insertion of a short section of inclined rectangular waveguide in the middle of the cavity body. In this way we realize dual-mode filters by using only junctions of waveguides with rectangular and circular cross sections, thus enabling a very efficient CAD of such filters. This arrangement also proves particularly convenient from the manufacturing viewpoint. Measured response of a breadboard channel filter operating at Ku-Band shows good agreement with theoretical simulations; a sensitivity analysis confirms the validity of the proposed design.