Twisted-Shaped Millimeter-Wave Hybrid Couplers in 150 nm GaN Technology for 5G Applications

This paper presents the first implementation of two innovative 90° hybrid couplers in Gallium Nitride (GaN) process designed for 5 G applications. In a very compact design, both couplers target low insertion loss (IL) and large fractional bandwidth <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\left(\text{FBW}_{1 ~\text{dB}}\right)$</tex> to replace conventional couplers. The first coupler exhibits minimum insertion loss of 0.44 dB at 22 GHz with a fractional bandwidth of 31%. The second coupler was optimized to reach a minimum insertion loss of 0.28 dB at 25.5 GHz with a fractional bandwidth of 29%, making it suitable for wideband applications. Both couplers perform with an output phase imbalance of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$93^{\circ} \pm 2^{\circ}$</tex>. Both circuits were designed using 150 nm GaN on SiC GH15 technology from United Monolithic Semiconductors (UMS).