Design Of X-band GaN MMIC Power Amplifier

GaN high electron mobility transistor(HEMT) has advantages of high power density, high breakdown voltage and high output power, which is widely regarded as a very promising candidate for the next generation of microwave power device application and has recently become the focus of research. Based on GaN HEMT the monolithic microwave power amplifier with great advantages of high output power, high operating voltage and wide frequency bandwidth has been widely used in microwave communication technology, phased-array radar and aerospace.In this thesis, many research works had been done on the development of Al GaN/GaN HEMT devices and GaN MMIC power amplifier circuits. The main research work and results are summarized as follows:1. Based on our self-developed Al GaN/GaN HEMT, the basic theory of GaN HEMTs are analyzed, the direct-current(DC) current-voltage(IV) characteristics and small signal S-parameters of GaN HEMT are also measured and analysed, an accurate small signal equivalent circuit model is established. To verify the model, S-parameters are obtained from the modeling and measurements. The good agreement between the measured and the simulated results indicate that this model is accurate, stable and comparatively clear in physical significance.2. The principal performance parameters and basic working principles of GaN MMIC power amplifier are researched. A new flow to design power amplifier is proposed, which utilizes the design technique of S-parameters combined with Load Pull measurement results, the GaN HEMTs microwave power amplifiers are realized without mature large signal transistor model, and this helps provide technical support for the circuit design.3. The design process and the topology of GaN MMIC power amplifier are summrized. And with the combined stabilization networks, a two stage broadband GaN MMIC power amplifier with flat gain performance is designed. Adoptting low-pass matching networks, the MMIC is designed to fully match a 50? input and output impedance.After optimized, the results of EM simulation show that MMIC demonstrates small signal gain S21 of23(?)0.5d B over the operating frequency range of 9.0-10.2GHz with input and output reflection coefficient less than-8d B and-6d B, respectively. And the simulated K factor shows that the amplifier is stable at the whole frequency range. Finally, the rational distribution of the microstrip lines is made and then the circuit layout is obtained by L-edit software. And recording to the level of our lab?s technology, the corresponding process of realizing MMIC power amplifier is proposed, and the key points of the process are analyzed.