Computer-aided design and improved performance of tunable ferrite-loaded E-plane integrated circuit filters for millimeter-wave applications

The modal scattering matrix method is applied to the rigorous computer-aided design of low-insertion-loss magnetically tunable E-plane metal-insert filters with improved characteristic, where only the resonator sections are loaded with ferrite slabs, and large-gap finline filters on a ferrite substrate of moderate width. The design method is based on field expansion in suitably normalized eigenmodes, which yields directly the modal scattering matrix of key building block discontinuities, which in turn are appropriately combined for modeling the complete filter structure. The theory includes both the higher order mode interaction of all discontinuities involved and the finite thickness of the metal inserts, or metallization. Optimized data are given for magnetically tunable Ku-band (12-18 GHz), Ka-band (26-40 GHz), and V-band (50-75 GHz) metal-insert and finline filter examples. The theory is verified by measurements on the Ku-band metal insert and finlines filters, utilizing ferrite materials.<>