Compact 3D-Printed Folded Branch-Line Hybrid Coupler based on Helical-Microstrip Transmission Lines

The aim of this work is to fabricate and characterize a very compact branch-line coupler at the UHF band, where the wavelength is critical for miniaturization. In order to do this, the advantages of a 3D-printed electronics manufacturing process developed in former work demonstrated the usability of helical-microstrip transmission lines and allowed the materialization of a new folded topology for hybrid couplers. The design methodology and the manufacturing process have been described. A conventional hybrid coupler has been also designed, manufactured and characterized in order to compare dimensions and model simulation and prototype characterization results in terms of the scattering parameters.