Patent ID: 7429902

Claim:
A differential transmission line comprising: a substrate; a ground conductor layer disposed on a rear side of the substrate; and a first signal conductor and a second signal conductor disposed in parallel to each other on a front side of the substrate, the first signal conductor and the ground conductor layer composing a first transmission line, and the second signal conductor and the ground conductor layer composing a second transmission line, wherein, the differential transmission line includes two straight regions in which the first and second transmission lines extend linearly and a curved region interconnecting the two straight regions; the first signal conductor is disposed in a position relatively close to a center of curvature of the curved region, and the second signal conductor is disposed in a position relatively far from the center of curvature; in the curved region, a plurality of slots which are orthogonal to a local signal transmission direction are provided in the ground conductor layer; and the plurality of slots intersect the first signal conductor, the plurality of slots being connected to one another on an inner side of curvature of the curved region; wherein, a line width Wb 1 of the first signal conductor in at least a portion of the curved region is smaller than a line width Ws 1 of the first signal conductor in the straight regions; a line width Wb 2 of the second signal conductor in at least a portion of the curved region is smaller than a line width Ws 2 of the second signal conductor in the straight regions; a gap width Gb between the first signal conductor and the second signal conductor in at least a portion of the curved region is equal to or less than a gap width Gs between the first signal conductor and the second signal conductor in the straight regions; and a minimum value Rb 1 of radius of curvature of a line edge of the curved region of the first signal conductor that is closer to the center of curvature is greater than a perpendicular distance Rs 1 from the center of curvature to an extension of a line edge of each straight region of the first signal conductor that is closer to the center of curvature.