On-Chip GaN Planar Transformer Design for Highly Integrated RF Systems

Abstract

The work presented in this paper concerns the design of an on-chip GaN transformer. The integrated transformer is composed of two planar stacked coils with spiral octagonal geometry. A comparison is done on different analytical methods to calculate the inductance of the transformer spiral planar coils. Three transformers with different outer diameters are compared to illustrate the influence of the coil geometry. The estimated inductance and dc series resistance are evaluated. Using COMSOL Multiphysics 5.3 software, the thermal effect is illustrated in the integrated transformer operating at high frequencies. The different parasitic effects created by the planar stacked layers are validated by the equivalent electrical circuit, and the different electrical parameters are calculated.