An apparatus includes a first differential transmission line and a second differential transmission line. The second differential transmission line is parallel to the first differential transmission line through an overlap region. The first differential transmission line includes a first line and a second line. The first differential transmission line includes N crossovers along the first differential transmission line through the overlap region at which the first line and the second line switch lanes with each other. N is equal to 1+INT {L/(λ/C)}, where L is a length of the overlap region, λ is a wavelength of a differential signal carried by the first or second differential transmission line, C is a constant, and INT {L/(λ/C)} is {L/(λ/C)} rounded down to the nearest integer.