Broadband Microwave Crossover Using Combination of Ring Resonator and Circular Microstrip Patch

The design of a novel wideband microwave crossover is presented. The proposed structure is fully compatible with microstrip circuits as it is printed on one side of a single-layer substrate. The structure is made up of a circular microstrip patch connected to a ring resonator. The operation of the presented design is explained by deriving the equivalent circuit model using the second-order even-odd mode excitations. The derived model is verified by full-wave electromagnetic simulations. A prototype is designed, developed, and tested. The results show a crossover with more than 18 dB of isolation, less than 0.5 dB insertion loss, and less than 0.25 ns deviation in the group delay across the band from 2.15 GHz to 3.35 GHz (44% fractional bandwidth).