Abstract: A controlled impedance interconnection assembly (50), for connecting an x-band coaxial connector (66) to a microstrip (60) on a circuit board (52), comprises a circuit board having a core (54) of dielectric material terminated by first and second surfaces (56, 58). An electrically conductive microstrip (60) and electrically conductive material (62) are adhered respectively to the first and second surfaces, and a hole (64), substantially at right angles to the surfaces, extends through the core and the conductive material on the second surface, and to the conductive microstrip on the first surface. The x-band coaxial connector, including an inner conductor (68) and a conductive shell (70) coaxially surrounding the inner conductor, is secured at right angles to the circuit board.