Abstract: An apparatus for coupling a waveguide structure to a printed circuit transmission line connected to a solid state device requiring a DC bias comprising: a hollow waveguide connector; a base mounted onto that connector and supporting the transmission line; a transition element, preferably a coupling ridge, for RF coupling the waveguide connector to the transmission line; a connecting means for feeding the DC bias voltage from an external bias network through the wall of the waveguide connector and the transition element to the transmission line. The connecting means, and the transition element are DC insulated from the other parts of the waveguide connector. The built-in DC bias eliminates the need for biasing networks, RF chokes, filters and DC blocks mounted on the printed circuit.