Microwave Power Amplifier Design Based On GaN HEMT Modeling

Communication is closely related to our current life,from GPS navigation,radiosonde to weather radar,airborne radar,satellite communications,are all the result of the development of wireless communication systems.With the continuous development of wireless communication systems,a higher demand is raised for microwave power amplifiers that are indispensable to the system.As far as the current development is concerned,the development of the first generation of semiconductor materials represented by SiC has been very mature,and it is also difficult to make breakthroughs.The second generation of semiconductor materials represented by GaAs is also difficult to meet the requirements.The third generation semiconductor material represented by GaN is also called a wide bandgap semiconductor.It is an important choice for active components of microwave power amplifiers due to its high operating frequency,high power density,and high operating temperature.At present,the research on GaN devices at home and abroad is mainly focused on the process and structure.The modeling of the devices is not mature enough and accurate,but the device modeling is indispensable in the application process of GaN devices.The model that correctly reflects the device’s operating characteristics can speed up the circuit design process,improve efficiency,and save costs.The GaN device selected in this article is a commercial GaN HEMT from CREE.In the early stage,the device was tested every 25℃ in the ambient temperature range of 25℃ to 300℃.Then,based on this,combined with simulation software,the resulting discrete data is processed.The small-signal equivalent circuit model that can reflect the device’s operating characteristics in a wide range of bias is selected,the intrinsic parameters and parasitic parameters in the model are extracted,and a large-signal model of a GaN HEMT is established based on this.In the large-signal model,the parasitic parameters refer to the small-signal model.The main work is to establish the drain-source current model and the capacitance model.Based on the classical model,the drain-source current model is improved,and the Gaussian function is used creatively as a carrier for describing the capacitance model.Considering that GaN HEMT often need to operate in a high-temperature working environment,device characteristics will change significantly with changes in ambient temperature.Therefore,in this paper,temperature parameters are added to the improved large-signal model to make the model able to correctly describe the operating characteristics of the device following ambient temperature changes.Next,a model of GaN HEMT is established in simulation software,which can be applied to circuit simulation design.The other part of this article is based on the GaN HEMT model established in this paper.This chip is used as the active component of the microwave power amplifier.The load-pull method and source-pull method are used to design the operating frequency at 2.4 GHz-The 4.5GHz Class AB microwave power amplifier,which spans the S and L bands,can be used in aerospace communications,satellite communications,radar communications,and other applications with extremely high ambient temperatures.