Bandpass Filter Based on 3-D-Printed Ceramic Resonators

A dielectric-loaded cavity filter working in the Ku-band with wide bandwidth and high selectivity is presented. The structure is composed of rectangular waveguide cavities loaded with 3-D-printed dielectric resonators. An example of a 4-pole filter is shown in this paper. The filter has three rectangular cavities loaded with three dielectric resonators made of alumina. The dielectrics have a hexagonal shape and have been designed as a single piece. They operate with the dielectric mode TE
01δ
and the cavity mode TE
101
. More specifically, the mode TE
01δ
was exploited for cavities 1 and 3, whereas modes TE
01δ
and TE
101
were exploited for the middle cavity. These combinations of modes were used in order to obtain transmission zeros (TZs) in the upper and lower stopband of the filter, and obtain as a result, a high-selective filtering response. For validation purposes, a 4-pole filter working in the Ku-band at 14.125 GHz, with 5.3% fractional bandwidth was fabricated and measured.