High selectivity wideband filtering crossover using stub-loaded ring resonators

摘要

This paper proposes a high selectivity wideband filtering crossover using stub-loading ring resonators. Cascaded coupled lines are used to generate two transmission zeros near the crossover passbands. In addition, patterned grounded conductor in the grounded plane can enlarge the coupling coefficient for the coupled lines with increasing the even-mode characteristic impedance, and the isolated conductor placed inside the slot can decrease the odd-mode characteristic impedance. The filtering crossover operated at 2.2 GHz with bandwidth of 27.5% from 1.945 GHz to 2.55 GHz are designed and fabricated. It shows good return loss more than 20 dB and nice insertion loss less than 1.7 dB in passband.