Abstract: A TO-style plug-in package for MMICs and associated antenna structure is comprised of a microwave circuit component carrier having a generally cylindrically shaped conductive header upon which one or more MMICs are supported. An aperture through the header contains a conductor pin supported within a glass seal interface, so as to form a hermetically sealed matched impedance transmission line through the package. The conductor pin is connected to a bonding pad of a microwave circuit component on the header. A generally cylindrical conductive cover engages the header and encloses a cavity within which the microwave circuit components are supported. A microstrip antenna is supported on a dielectric layer overlying an outer surface of the conductive cover and is connected to a further conductor pin that extends through a glass-sealed aperture in the cover and forms a matched impedance transmission line from the antenna to the header.