A new configuration of dual mode rectangular waveguide filters

A design technique for a new configuration of dual-mode waveguide filters based on a distributed parameter model is presented. The key point of the new configuration is that the coupling between the two diagonal modes in a square waveguide resonator is obtained by deforming the square cross-section into a rectangular shape with a/b ~ 1. Hence, no discontinuity is present inside the cavities. The input/output rectangular waveguide cross-sections are rotated of 45° with respect to those of the resonator and the various couplings are realized by means of rectangular apertures. The obvious advantages of this configuration are related to the fact that all the cross-sections are rectangular.