mm-Wave GaN Varactors and E/W-Band Phase Shifter

In this paper, we characterize and compare novel anti-series GaN varactors of three different gate lengths for use at mm-wave frequencies beyond 50 GHz. We focus on insertion loss and phase steering capability versus bias range. The results show a capacitance ratio of up to 7.8 for the longest gates and a tradeoff between capacitance ratio and insertion loss. The devices were implemented in an established GaN MMIC technology, allowing co-design with other circuit features. Using the results of this study, we also develop a mm-wave phase shifter MMIC that operates in a wide frequency range from 50 to 110 GHz and enables phase offsets of up to 114 °.