Patent ID: 8198954

Claim:
A circuit board having opposite faces comprising: conductive signal via extending through the thickness of the circuit board, to which a central conductor of a high-frequency coaxial connector is connected; a plurality of conductive ground vias for reference electric potential extending through said circuit board thickness and arranged around a periphery of the signal, via for permitting a terminal for shield of the high-frequency coaxial connector to be connected thereto; a first ground layer formed by a conductor film disposed on one of the circuit board faces; a thin signal line, which is connected to said signal via and is as a microstrip line on the circuit board face; and, a second ground layer formed by a conductor film disposed on the other of said circuit board faces; wherein: the first ground layer has a first opening turned therein in which the conductive film is removed so as to define a first opening that encircles said via signal; and the second ground layer has a second opening formed in which the conductive film is removed so as to define a second opening that encircles the periphery of said signal via, the second opening including a convex portion configured to protrude toward said signal via at a region corresponding to the thin signal line in said second relief part opening.