The
coaxial line comprises a coaxial inner conductor and a first
dielectric layer encompassing the coaxial inner conductor and which is surrounded by a coaxial outer conductor. The coplanar line comprises a second
dielectric layer with a coplanar inner conductor and a first and second coplanar outer conductor applied to the front side thereof and with a metallization layer followed by a substrate carrier layer on the rear side thereof. The first and second coplanar outer conductors are separated from the coplanar inner conductor by the second
dielectric layer and the coaxial inner conductor is connected to the coplanar inner conductor and the coaxial outer conductor is connected to the first and second coplanar outer conductors. When high
bit rate data signals are transmitted via the connecting point of the
coaxial line and the coplanar line, the capacitative power is increased and undesirable reflections occur. In order to avoid this, a recess is provided in the metallization layer, beginning at the point of connection between the
coaxial line and the coplanar line and extending in an approximately symmetrical manner with respect to the coplanar inner conductor, tapering in the direction of the coplanar inner conductor as the distance from the point of connection increases.