Abstract: An electrical interconnect having a multi-layer circuit board structure is designed to facilitate source and load impedance matching. The circuit board structure has a first transmission line extending along a surface of one of the layers, and a second transmission line extending along a surface of another of the layers. A signal line connects the first transmission line to the second transmission line in the vertical direction of the circuit board structure. A conductive ground spacer is interposed between respective layers of the circuit board structure and has a through-hole in which the signal line resides. A dielectric medium, such as air, occupies the through-hole and substantially circumferentially surrounds the signal line. Accordingly, the ground conductor, the signal line and the dielectric medium form a coaxial structure in the vertical direction, by which it is easy to provide a desired characteristic impedance.