Compact Ultra-Wideband Cavity Filter Based on Suspended Ceramic Resonators in Additive Manufacturing

The design and first experimental results of a 4th order quasi-elliptic C-band ultra-wideband filter working at 6.3 GHz with 1.55 GHz bandwidth (FBW=24.6%) are presented in this paper. The peculiarity of this filter is that this ultra-wide band response is obtained by using dielectric resonators, thus overcoming one of the major limitation of the dielectric filters: their narrow-band behavior. The proposed filter is based on TM01δ mode dielectric loaded resonators fabricated by additive manufacturing. These allow for better results in terms of volume occupation with respect to other dielectric resonators still maintaining high unloaded Q-factor values (>2000). In the proposed solution each dielectric resonator and its supporting elements are fully fabricated in a single piece using ceramic additive manufacturing process. This allows for improving the Q-factor since no additional, potentially lossy, materials and support mechanisms are needed. The feasibility of the proposed approach was experimentally demonstrated through the measurements of a preliminary manufactured prototype.