Compact Filtering Crossover Using Stub-Loaded Ring Resonator

This letter presents a novel compact crossover with bandpass responses. It consists of a stub-loaded ring and coupling feeding structures. The equivalent circuit of each path between two diagonal ports is a filtering circuit. The stub-loaded ring acts as the resonator in both two paths and thus the size is miniaturized. Meandering feeding structures are utilized to realize transmission zeros to improve the selectivity. To verify the design concept, a compact filtering crossover working at 2 GHz is implemented and the simulated and measured results are presented.