Rectangular waveguide dual-mode filters without discontinuities inside the resonators

A new configuration of rectangular waveguide dual-mode filters is presented where no discontinuity is present inside the cavities. It Is based on the idea that coupling between the two diagonal modes in a square waveguide resonator can be obtained by deforming the square cross-section into a rectangular shape. Hence, no discontinuity is needed to couple the two diagonal polarizations. As a consequence, the input/output rectangular waveguide cross-sections are rotated by 45° with respect to those of the resonator. The advantages of this configuration are related to the fact that all the cross-sections (as well as the coupling apertures) are rectangular and no tuning is needed