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

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 TE 11 δmode 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.