Abstract: A surface-mountable mm-wave signal source is provided. The surface-mountable mm-wave signal source comprises: a conductive metal base; a mm-wave signal source disposed over an upper portion of the metal base; a first radio frequency transmission line carrying a quasi-TEM signal from the mm-wave signal source, which is disposed over an upper portion of the metal base and proximate the signal source; a first mode transformer at least partially integrated into the upper portion of the metal base to convert the quasi-TEM signal carried by the planar transmission line into a rectangular waveguide mode signal; a waveguide well having upper and lower ends disposed within the base for carrying the rectangular waveguide mode signal from an upper portion of the base to a lower portion of the base; and a second mode transformer at least partially integrated into the lower portion of the base to convert the rectangular waveguide mode signal to a quasi-TEM signal within a second radio frequency transmission line.