GaN HEMT Nonlinear Model And Microwave Power Amplifier Design

Compared with the former two generations material: Silicon (Si) and Gallium Arsenide (GaAs), the third generation of semiconductor Gallium Nitride (GaN) has many advantages,such as wider band-gap, high electron mobility, high saturation rate, good voltage-resistant and better thermostability. And these good characters give the AlGaN/GaN high electron mobility transistors (HEMTs) great advantages of high output power density, high voltage and high output impedance in optical-electronic, high-temperature high-power component, civil communication, military microwave communication and other applications.For GaN devices used in microwave and millimeter wave circuits, it needs higher requirement in device reliability and circuit design. At present, AlGaN/GaN HEMT components reliability and model theory research achievements less, and it can't well describe GaN device characteristics.In this paper, based on the model of classical Angelov and EEHEMT1, a new semi-empirical DC model is established. This model takes into account the effect of the gate-source voltage V_gs on the knee voltage V_knee and self-heating effect. During the study, the model parameters are extracted by MATLAB. Compared with the classical empirical models, the new model equations describe the AlGaN/GaN HEMT I-V characteristics well both in the linear region and saturation regions, and achieve good simulation results. Then, based on the Load-Pull test and the power sweep test results, combined with laboratory-made AlGaN/GaN HEMT devices, output power, gain and PAE is given respectively. Under V_ds=30V,V_gs=-4.0V, CW operating condition at 5.5GHz, the device with 100μm gate width gets the maximum output power 28.63dBm. The maximum power added efficiency is about 35% at the input power 14dBm. The linear gain is about 17dB. Under the same conditions, by size transformation, the device with 1mm gate width gets the maximum output power 37.79dBm. The maximum power added efficiency is about 40%. The linear gain is about 15dB. Finally, based on the established model, a X-band AlGaN/GaN HEMT power amplifier circuit at class AB is achieved. For enhancing the performance of circuit, we optimized the stable structure and matching net. We get the better simulated results. The maximum output power is 46.17dBm. The maximum power added efficiency is about 54%. The linear power gain is 17.3dB. In addition, using five order harmonic suppression topology structure and micro strip line, an E class switching power amplifier with GaN HEMT is also designed. The maximum output power is 40.5dBm. The maximum power added efficiency is about 68.2%. The linear power gain is 13.64dB. And, this circuit suppressed harmonic signal under five orders well.