Abstract: A crossover for microwave electromagnetic radiation is constructed in a planar configuration for the transference of all of the power of a wave in a first transmission line to a wave in a second transmission line. The crossover is formed of two pairs of cross arms wherein, in each pair, the arms are spaced apart by an electrical length of ninety degrees along the first and the second transmission lines, and couple power of the waves between the first and second transmission lines with an introduction of a quarature phase relationship. The impedance presented to a wave of a cross arm is less than the corresponding impedance of the first and the second transmission lines by a factor of the square root of two to inhibit the generation of relections at junctions between a cross arm and the first or the second transmission line. Each junction provides for a diversion of one-half the power of the wave from the first or the second transmission line to a cross arm.