A Wideband Uniplanar Double-Ring Crossover With Balanced and Single-Ended Paths

For the first time, a planar crossover with balanced and single-ended (SE) paths composed of double rings is presented. The parameters' constraint is extracted, and rigorous derivations are provided. In addition, the relationships between the parameter values and the bandwidths are thoroughly analyzed. Finally, a prototype is designed and fabricated, which achieved 36.9% and 37.7% 1-dB insertion-loss bandwidths for the balanced and SE paths. Meanwhile, the 15-dB path-isolation bandwidth is 32.4%, and a 40.6% bandwidth of 15-dB common-mode suppressions is realized.