Compact filtering crossover for crossing signals with different frequencies

This paper presents a novel planar crossover for crossing of two transmission paths carrying signals with different frequencies. Each transmission path between two diagonal ports is equivalent to a bandpass filter and filtering responses are obtained. The crossover is designed based on a stub-loaded ring resonator shared by two transmission paths and thus the size is miniaturized. Wide isolation frequency range between two paths is realized. To verify the design concept, a compact filtering crossover operating at 1.9 GHz and 2.35 GHz is implemented and the simulated and measured results are presented.