Scattering Matrix Approach for the Design of Dual-Mode Waveguide Filters Without Discontinuities Inside the Resonators

A synthesis procedure for a new configuration of dual-mode waveguide filters with distributed coupling is presented. In this configuration the dual-mode coupling is obtained by exploiting the well-known fact that the diagonal polarizations are coupled in an almost square waveguide. The obvious advantage of this type of structure is that the cross-section of all the discontinuities are rectangular. The knowledge in analytical form of the dual-mode coupling suggests the use of a scattering matrix formulation to obtain the filter synthesis scheme. Universal design chart, which yield directly the scattering parameters of the various junctions are presented.