Spurious stopband improvement of dual-mode dielectric resonator filters using T-shaped coupling probe

摘要

This work presents a new design technique for dual-mode dielectric-loaded resonator filter operating at 2.18 GHz by using T-shape coupling probe. A cylindrical dielectric puck is suspended in the middle of metallic cavity and short-circuited on the side walls. Four vertically etched-slots through the dielectric puck from the top to the base of the ceramic puck offer a high unloaded quality factor of 4300 at the fundamental${m T}{m E}_{11delta }$TE11δmode and allows the T-shape coupling to be located close to the centre of the dielectric puck. The size reduction ratio in this resonator was 11% compared with air-filled coaxial resonator. Fourth-poles Chebyshev bandpass filter with planar configuration was designed and implemented by employing two dielectric-loaded cavities. The experimental results show that the spurious-free window of ∼820 MHz from the fundamental frequency of 2.18 GHz and the operational bandwidth of 77 MHz were achieved.