High Performance Filtering Crossover Using Ring Resonator

A high performance filtering crossover using ring resonator is proposed in this paper. To introduce a pair of transmission zeros around the passband, four sets of coupled lines are loaded on the basis of the ring resonator. Meanwhile, coupling coefficient is enhanced due to the regular grounded conductor, which improves the even-mode impedance. To confirm the design approach, a filtering crossover operating at 2.2 GHz is fabricated with bandwidth of 27.5% from 1.945 GHz to 2.55 GHz.