Miniature Triple-Mode Dielectric Resonator Filters

In this paper, a new class of triple-mode microwave filters is presented. These devices use the degenerate pair of the HE11δ mode and the single TM01δ mode in dielectric-loaded cavities with an unloaded Q-factor of 3000-5000 and reasonable spurious-free window. The proposed structure is obtainable in less than one-quarter of the physical volume of equivalent TEM filters. A finite-element method solver for electromagnetic structures (HFSS) is used to study the main properties of this resonator. Fundamental design rules for triple-mode bandpass filters with controllable finite transmission zeros are presented. Design examples of bandpass filters with finite transmission zeros on the high or low or both sides of the passband are demonstrated. Measured results demonstrate excellent performance.