Transition from a coaxial transmission line to a printed circuit transmission line

A transition piece for coupling a coaxial transmission line to a printed circuit (PC) transmission line. The transmission line terminates in a conductive pin projecting through a conductive coaxial ground plane. The transition piece consists of a conductive plate which is adapted to be fixed between the coaxial ground plane and a PC ground plane of the PC transmission line. The plate is in electrical contact with both the coaxial and PC ground planes while the conductive pin contacts a conductive strip of the PC transmission line. Furthermore, the plate has an opening which is shaped and aligned with the pin so that a transition-impedance of the transition piece is substantially equal to a line impedance of the coaxial and PC transmission lines.