Compact doublet structure for Quasi-elliptical filters using stereolitographic 3D printing

In this paper a doublet consisting of a pair of mushroom-shaped posts transversally positioned into an evanescent waveguide is presented. An ultra-compact second-order filter having a response with two transmission zeros has then been designed, manufactured and measured. Additive Manufacturing (AM) technology based on stereolithography (SLA) has been exploited for the filter manufacturing. The resulting structure shows excellent response thanks to the tight tolerances obtained in the AM process and to the very good surface conductivity obtained in the metallization process.