The present invention is directed to an interface for connecting a waveguide manifold of a transition to a stripline manifold of the transition. The interface may include a plurality of metamaterial layers, each including a metamaterial(s). The interface may further include a ground plane layer which may be connected to both the plurality of metamaterial layers and to the stripline manifold. Further, the interface may include a plurality of ground vias which may form channels through each of the layers of the interface and through the stripline manifold for providing a ground structure for the interface. The interface is further configured for forming a resonant structure which provides a low-loss, broadband conversion between a stripline mode and a waveguide mode for electromagnetic energy traversing through the interface between the waveguide manifold and the stripline manifold.