A waveguide assembly for propagating electromagnetic signals along a defined path includes a conductive waveguide and a dielectric waveguide. The conductive waveguide includes two side walls that extend parallel to each other between first and second ends of the conductive waveguide. A channel is defined between the two side walls. The dielectric waveguide includes a cladding formed of a first dielectric material. The cladding defines a core region therethrough that is filled with a second dielectric material different than the first dielectric material. A mating end of the dielectric waveguide is received in the channel at the first end of the conductive waveguide to electromagnetically connect the dielectric waveguide to the conductive waveguide. A remainder of the dielectric waveguide is exterior of the conductive waveguide and extends away from the conductive waveguide.