Design And Research Of S-Band High Efficiency Power Amplifier Based On GaN HEMT

RF power amplifier is one of the most important components in wireless comunication system.In recent years,because of the rapid development of wireless communication system,the requirement for the efficiency of power amplifier gets higher.As the third generation semiconductor chips,GaN HEMT's superior performance has become the first choice for researchers in the design of high-efficiency power amplifiers.And the power amplifier with harmonic control network has become one of the research hotspots by virtue of the simple structure and excellent efficiency improvement ability.In this thesis,two high efficiency power amplifiers on the basis of the harmonic control circuit are designed and measured.First,this thesis introduces the relevant basic theory of RF power amplifiers,and analyzes the importance of GaN transistor models to the design of high efficiency power amplifiers.Then formulate the power amplifier design indicators,select the GaN transistor based on the indicators to design a class F power amplifier,consider the inherent parasitic parameters of the transistor package to design a parasitic compensation circuit,and use the second and third harmonic control network to control the drain current and voltage shaping.Then obtain the optimal matching impedance under harmonic control through load pull technology.The whole design is implement in the ADS and the layout is completed.The designed class F power amplifier is fabricated.The actual measurement results show that the peak power added efficiency at 2.4GHz is77.5%.When the input power is 26 d Bm,the corresponding Gain is 14.5d B,and the output power is 40.4d Bm.Then,based on the fundamental of filter,and the active bandpass filter is designed.According to the experience in the design of class F power amplifiers,the active bandpass filter is introduced on the basis of harmonic control.In order to simplify the structure and to reduce the size of the amplifier,output circuit only control the second harmonic,the harmonic control circuit of the second wave of short route on the bias of the ?/4 transmission line.The final measured results show that the maximum power added efficiency of the power amplifier based on active power filter at 2.4GHz is 74.5%,and the maximum output power is 41.5d Bm.When the input power is 26 d Bm,the Gain is 13.3d B.The PAE is 59.5-72.3% in the range of 2.3-2.6GHz bandwidth.Finally,through simulated and measured results,the feasibility of the two design methods in this thesis to improve the efficiency of power amplifiers based on GaN HEMT is demonstrated.And a linearization scheme that uses gain expansion to achieve back distortion in the output circuit is proposed to improve the linearity of GaN high efficiency power amplifiers,which makes it have good linearity while obtaining high efficiency.It also provides experience for the future design of linearity improved GaN high efficiency power amplifiers.