Design procedure for interdigital waveguide bandpass filters based on flat metallic strips

In this work, we describe a new topology for interdigital bandpass filters implemented in waveguide technology. Compared to classical coaxial resonators, which are typically based on cylindrical metallic posts, the resonators that we propose are based on rectangular boxed cavities loaded with flat metallic strips of a finite thickness. The main advantages of the proposed topology are low-cost practical realization and manufacture simplicity. The design process, which is based on the classical circuit-based approach combined with an efficient segmentation of the component, uses the well-known Aggressive Space Mapping technique, with the aim of reducing the overall computation effort. In order to validate the new topology and the design procedure, interdigital bandpass filters of orders 3 and 5 operating at the S-band have been designed. For validation purposes, the results obtained are successfully compared to simulations provided by two different full-wave electromagnetic tools (i.e., Ansys HFSS and CST Studio Suite). Furthermore, a multipactor study has also been performed, with the aim of exploring the power handling capability of the proposed filters in view of possible space applications. Finally, the design of classical interdigital filters based on cylindrical posts is also discussed, with the aim of comparing both topologies regarding compactness, as well as in terms of their electrical and high-power performance.