A Systematic Design Procedure of Classical Dual-Mode Circular Waveguide Filters Using an Equivalent Distributed Model

In this paper, we propose a systematic procedure for the accurate design of classical dual-mode filters in circular waveguide technology. The design procedure is based on the previous synthesis of an intermediate distributed model, which links the standard lumped (or coupling matrix) elements circuit with the practical waveguide realization. We then show how the equivalent distributed model can be directly used to obtain the physical dimensions of these filter components (typically rectangular and cross-shaped irises, as well as tuning and coupling screws). The value of this paper lies in the fact that the proposed design strategy provides the final dimensions of these complex structures with unprecedented levels of accuracy and numerical efficiency, as it is shown through two dual-mode filter designs for narrowband applications, and measurements of a manufactured prototype.