Design of the Planar Six-Port Crossover With Double Rings

The six-port crossover with the planar structure has been proposed. By utilizing double rings with quarter-wavelength branches, a wide passband can be obtained. With the proposed crossover, three intersecting channels with good performances of transmission and isolation can be generated. The even-odd mode and the six-fold rotational symmetry are adopted to derive the analytical equations. Moreover, the performances of diagonal transmission, port matching, and isolation between different channels are achieved with a fractional bandwidth of 13.5%, which has been demonstrated by the theoretical and measured results.