An ultra-compact full-band waveguide quadrature hybrid coupler

This work proposes an easily scalable quadrature hybrid coupler (QHC) topology with two symmetric stepped apertures that originate a square coaxial-like mid-section. This new configuration enables an ultra-compact design, three times shorter than equivalent structures, having 40% of fractional bandwidth with 25 dB of matching/isolation and 1 dB of axial ratio (AR). The impedance transformers can be easily redesigned to meet other requirements related to electrical performance or even other desired coupling values. For verification purposes, a prototype at Ku -band was manufactured and measured showing good agreement with simulation results.This work was supported in part by the Spanish Ministry of Science, Innovation and Universities under Project TEC2017-83343-C4-1-R and in part by European Fund for Economic and Regional Development (FEDER)