Integrated scalable and tunable RF CMOS SOI quadrature hybrid coupler

Abstract

Hybrid is a key component in RF and Microwave design, and particularly for balanced power amplifier (PA). This paper describes a pragmatic approach of the quadrature hybrid component design, aligned with measurements. It considers the cell as a combination of 2 simple elements rather than X/4 lines. The hybrid becomes scalable to reach a given frequency, and can be optimized by adding simple small twisted cells. The main advantages are to keep the two input (or output) blocks perfectly in parallel, and to consider the distance between the two blocks as a first dimension parameter. The component can also be tunable over frequency. The form factor is rectangular, using 2 metal layers at least and can be easily integrated in silicon technologies. The typical insertion loss is below 0.7dB in H9SOIFEM at 5.85GHz and 14GHz, while tunability can extend the frequency by more than 25% at 28GHz in 28FDSOI.