Impedance matching along vertical path of microwave vias in multilayer packages

High frequency matching in a multilayer ceramic package is accomplished by a radial stub arrangement provided in one or more of the ground planes of a stack of layers forming the package. A signal via extends vertically upwardly between a ball grid array at a bottom surface of the stack and a coplanarwaveguide in the form of a signal trace on a top surface of the stack. Each radial stub arrangement surrounds the signal via and is formed by a central space in the ground plane which surrounds the via and a plurality of stub-forming spaces in the ground plane which extend radially outwardly from the central space. The stub-forming spaces form a plurality of radial stubs which extends inwardly from the ground plane to locations adjacentbut spaced apart from the signal via. The discontinuities provided by the spaces behave as a shunt inductance connected to a series capacitance. The radial stub arrangements provide high frequency matching in an arrangement which is confined to the vertical path of the signal via, thereby enabling higher interconnect density in multilayer packages.