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
$(\text{FBW}=24.6\%)$
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 TM
01
$\delta$
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.