A large signal scaling model of high power GaN microwave device

Abstract

With the rapid development of wireless communications, GaN HEMTs, which have various advantages of high power density, high electron mobility, and high breakdown threshold, have attracted increasing attention. Microwave power amplifiers based on GaN HEMTs are widely used in many fields, such as communication, medical, and detection instruments. In the accurate design of GaN microwave power amplifiers, reliable RF large signal models are vitally important. In this paper, a scalable large-signal model based on EEHEMT model is proposed to describe the properties of multifinger AlGaN/GaN high electrom mobility transistors (HEMTs) accurately. A series of scaling rules are established for the intrinsic parameters of the device, including drain-source current Ids, input capacitance Cgs and Cgd, which take into account both the gate width of a single finger and the number of gate fingers. With the proposed scalable large-signal model, the performances of the L-band GaN high-efficiency power amplifier with the length of gate of 14.4mm is analyzed. This amplifier demonstrates outstanding performance with the output power up to 46.5dBm and the drain efficiency of over 70% covering the entire frequency range from 1120MHz to 1340MHz. Great agreement between the simulations and experiments is achieved, demonstrating the excellent accuracy of the proposed model. Moreover, the proposed model can further predict the performance of high-order harmonics, providing an effective tool for the design of advanced high-power and high-efficiency microwave power amplifiers. Certainly, the EEHEMT model lacks the ability to characterize the dynamical behavior induced by trap and self-heating effects. Thus, for further consideration, scaling models for the thermal resistance and heat capacity will be investigated to broaden the applicability of the proposed model in the case of continuous waves.