Single- and Dual-Band Frequency-Agile Dielectric Resonator Filters

Single- and dual-band frequency-agile dielectric resonator (DR) filters are proposed in this article. A printed circuit board (PCB) with varactors is attached to the bottom of the DR. It has two functions: first, the boundary condition of the bottom side of DR is reconstructed as the electric wall and two resonant half-mode are obtained. Second, the tuning elements and bias circuit are easily embedded with the 3-D structure. After that, the two resonant modes can be controlled independently. Moreover, a cross feeding line is utilized to excite the two modes simultaneously. Based on the proposed tunable dual-half-mode DR, a single- and dual-band reconfigurable filters are designed. The measured results demonstrate that, only using two resonators, the two passbands of the DR filter can be tuned independently and the roll-off rate of the passband can be maintained sharp in the tuning range. Benefiting from the electrical tuning scheme, the tuning speed of the filter is high compared with the mechanical tuning.