Single-mode Dielectric Resonator Bandpass Filter without Internal Coupling Iris

This research proposes a single-mode dielectric resonator bandpass filter. Designing a rectangular dielectric resonator involves drilling a hole at the center of the structure to shift the spurious frequency away from the initial frequency. This approach configures the external Qe of the resonator as an I/O coaxial probe. The internal coupling between two resonators is easily adjusted without irises between two resonators. The filter circuit was designed using the HFSS simulator as a secondorder circuit at a frequency of 1.95 GHz, with a 3-dB fractional bandwidth of 3.59% (70 MHz). The passband insertion loss is less than 0.04 dB, and the return loss is better than 22.46 dB in the passband.