Improving small signal modeling of GaN HEMTs with vector fitting method

In the paper, an improved small-signal equivalent circuit model for GaN HEMTs is proposed for effectively capturing the high-frequency behavior of the device. In order to simulate the gain flatness of the device at high frequencies, the intrinsic capacitive coupling noise characteristic at high frequencies is considered in the proposed model. Also, in order to consider the phase delay phenomenon present in the device at high frequency conditions, additional current sources are added to the proposed model to simulate the phenomenon. In addition, the parameter values in the model are obtained by analyzing the rational function poles, residuals, and constants extracted by vector fitting (VF), which accurately models the Y-parameter characteristics of the device at high frequencies. The proposed model can accurately model the main physical properties of the device with good physical consistency and parameter interpretability. With the help of the VF, the model realizes high-precision matching of the Y-parameters of the device in a wide frequency band while significantly reducing the complexity of parameter extraction.