A novel technique for coupling microwave signals to a slot transmission line and for effecting a simultaneous impedance transformation. One lead of a microwave capacitor, connects to a source of microwave signals via a microstrip or coplanar transmission line. The other capacitor lead, located in the same plane as the slot line, crosses the slot line at a right angle and connects to the ground plane on the other side of the slot. A short-circuited segment of the slot line extends N.lambda./4 beyond the point of crossing where N is an odd integer.