Dual-Mode Dielectric-Loaded Resonator for Satellite High-Power Filters

A novel resonator based on higher order dual-mode dielectric-loaded cavity is presented in this paper for compact high-power bandpass filters. The proposed doublet consists of a ceramic high-permittivity dielectric cylinder placed in the center of a circular metal cavity. The presence of the dielectric inside the cavity allows an excellent thermal stability. The dielectric material is based on BMT (Barium Magnesium Tantalum oxide) and it has been selected for its excellent performance in terms of losses. The presence of the dielectric results in a noticeable resonator shrink. In order to guarantee thermal sink capabilities suitable for the high power requirements, the dielectric cylinder cannot be too small. For this reason a higher order resonant mode has been selected. A pair of shaped irises placed on top and bottom surfaces of the cavity allows the control of the coupling to the adjacent cavities. Each doublet can provide a transmission zero above or below the passband. Its position is controlled by the rotation angle of the irises. The feasibility of proposed solution has been demonstrated through the measurement of a preliminary second-order Ku-band filter prototype, which shows very promising results. This doublet can be used as building block for higher order filters.