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.