Design and Additive Manufacture of Multi-Tapered Coaxial Baluns

In this article, a new design method is introduced for wideband transitions from an unbalanced coaxial feed to a balanced two wire port. The device expands upon the traditional tapered coaxial balun by allowing for variations of both the inner and outer conductor radii in addition to the slot width. This multi-tapered approach provides additional design freedoms useful for realizing a wide range of impedance ratios, satisfying fixed geometrical constraints, and reducing transmission losses. A multimaterial additive manufacturing (AM) approach is described for fabricating the balun’s complex 3-D geometry. Experimental validation was conducted within the Ku -band for printed back-to-back baluns and an integrated antenna feed that combined a printed connector, a multi-tapered coaxial balun, and a spiral antenna. Simulated and measured results showed good performance over the frequency band of interest.