Large-signal modeling of a scalable high-Q AlGaN/GaN high electron-mobility varactor

In this paper, a new large-signal model for gallium nitride high electron-mobility varactors is presented. Compared to former models, this model is scalable and describes the whole range of operation from breakdown to forward conduction. The model consists of a passive parasitic shell, an ideal intrinsic core, and takes dispersion into account. The main extraction is done on an eight-finger device with a tuning ratio of 4.3 and a minimum quality factor Q above 30 for frequencies below 2 GHz. The model is verified for a large range of bias points and frequencies. Load-pull measurements provide evidence even at high RF input power up to 23 dBm.