Compact and Slow-Wave Tunable 28 nm CMOS-SOI Twisted Hybrid Couplers for 5G Applications

This article presents four twisted hybrid couplers exhibiting low insertion losses for 5G applications. Thanks to an accurate pre-sizing methodology and an electromagnetic model, three different twisted hybrid coupler architectures are presented and compared to offer different form factor trade-offs while maintaining state-of-the-art performances. A 26–44-GHz multi-band 90° twisted hybrid coupler exhibiting low insertion losses is then presented to improve its inherent bandwidth. Using a tunable 3-bit slow-wave architecture, the hybrid coupler offers eight operating modes allowing it to select the desired center frequency and covers a bandwidth of more than 51% while minimizing its losses. The hybrid coupler achieves insertion losses lower than 2.2 dB with a minimum of 1.45 dB at 26 GHz and a phase shift between the two output paths of 95° ± 5°. The coupler is highly robust to process variations, and offers a high power handling up to 35 dBm input. All of these circuits are implemented in a CMOS 28 nm FD-SOI process.