A Planar Microstrip Crossover With Lumped Inductors for Three Intersecting Channels

A planar microstrip crossover is proposed by using a stub-loaded ring structure with lumped inductors to realize good transmission and isolation performances for three intersecting channels. It can take the place of three conventional dual-channel crossovers. Since the component is with a sixfold rotational symmetric configuration, it can be analyzed by using its eigen-admittances and the even-/odd-mode theory. The analytical equations are derived to generate the design curves to determine the circuit parameters, operating bandwidth and transmission phase. The influence of the utilized lumped inductors on the crossover performance is also considered. A prototype is developed at 1.0 GHz with an occupied area of 0.308 × 0.294 λ_g², where λ_g is the guided wavelength of the central frequency. The performances of diagonal transmission, port matching, and isolation between different channels are achieved with a 6% operating bandwidth, which has been demonstrated by the theoretical, simulated, and measured results.