Design of Additive Manufacturing Oriented Top-/Narrow-Wall Couplers and 4x4 Butler Matrices

This paper presents the design of two hybrid couplers tailored to be 3D-printed. The topologies refer to the well-established narrow- and top-wall coupler architectures. These topologies were selected because of their structural and mechanical simplicity as well as their relatively compact footprint and broad bandwidth. The design techniques followed and presented in this paper enable the rigorous conception of such components with self-supporting structure aimed to be printed vertically (i.e., without inclining the model during the printing process). This later fact leads to high-quality manufacturing mainly because of symmetrical printing, which in turn minimizes the fabrication uncertainties and leads to microwave components with excellent RF performance. The combination of hybrid couplers allows also the conception of Butler matrices. A design example and the perspective of 3D-printed Butler matrices is also presented and discussed here. The proposed structures can be efficiently realized by fully-metallic additive manufacturing as already even more complex waveguide components have been addressed over the last years.