A Novel 1.7-2.85-GHz Filtering Crossover with Independently Tuned Channel Passbands and Reconfigurable Filtering Power-Dividing Function

In this article, a novel filtering crossover with independently tuned channel passbands and reconfigurable filtering power divider (PD) function based on evanescent-mode cavity (EVA) is proposed for the first time. It consists of four substrate-integrated-waveguide (SIW) EVA resonators loaded with piezoelectric actuators for frequency tuning. Four sets of varactors are used between adjacent resonators for control of interstage coupling, whereas four sets of varactors are inserted between ports and resonators for input-output matching. By controlling resonant frequencies of the EVA resonators and coupling coefficients between adjacent resonators, the passbands of the two orthogonal channels in the filtering crossover can be independently tuned in either synchronous or asynchronous fashion within the frequency range of 1.7-2.81 GHz. Meanwhile, by detuning the resonant frequency of one resonator in the crossover, the proposed structure can be reconfigured to become a three-port filtering PD with continuous frequency tuning covering 1.7-2.85 GHz. Moreover, with the independently tuned feature, a filter with reconfigurable filtering PD and diplexer functions can be easily achieved by attaching the proposed crossover to an external matching junction. Several prototypes were given to demonstrate the proposed techniques. Good agreement is obtained between simulated and measured results.