Research Of RF Power Amplifier Based On GaAs Process

Compared with the 4G LTE band,the most obvious feature of the 5G NR band is the increase of bandwidth.Larger bandwidth means higher transmission rate,lower communication delay and higher communication reliability.At the same time,the larger communication bandwidth also puts forward higher requirements for the RF system,especially for the power amplifier that plays the role of signal power amplification in the RF system,which puts forward the test of bandwidth,power,efficiency and linearity.In 5G communication,the power amplifier MMIC has two key performances that are more concerned,one is the linearity of the power amplifiers,and the other is the power backoff efficiency.With the in-depth study of semiconductor materials,a variety of substrate materials and transistor devices have been derived.GaAs HBT has become the mainstream process used in the design of base station and terminal power amplifier MMIC due to its excellent power density and linearity and other key advantages.The thesis starts with the two key indicators of power amplifier power backoff efficiency and linearity,and takes the mainstream GaAs HBT technology as the carrier to carry out the research on the design of base station power amplifier.Firstly,The thesis surveys the current research results at home and abroad,clarifies the background and significance of the research work,clarifies the key indicators of the challenges faced by the power amplifier,and clarifies the research direction of the thesis.Then the material and device characteristics of GaAs HBT process used in the design are analyzed,and its advantages and effects for power amplifier design are clarified.Then analyze the basic theory and circuit structure of power amplifier,including the classification of power amplifier,key indicators and relevant theory of Doherty power amplifier,and lay a theoretical foundation for subsequent power amplifier design.The first power amplifier designed is a broadband high-gain linear power amplifier based on InGaP/GaAs HBT process.The design frequency covers the 5G NR band of the three major domestic operators and is applied to the 5G multi-carrier base station transmission link.Through the innovative current adjustable adaptive bias circuit,the power amplifier can adjust the static current according to the requirements of the application scenario while improving the linearity.At the same time,the bias current is not sensitive to the fluctuation of the power supply voltage,and the reliability of the PA is improved.The test results show that the bandwidth of the power amplifier is 1.8-4.9GHz,the small signal gain in the band is 38dB,OP_1dB is 25dBm,and the closed-loop ACPR at 2.6GHz is-47.7dBc（@Pout=15dBm,NR 200MHz signal）,achieving a great linearity index.The second power amplifier designed is an asymmetric Doherty power amplifier chip based on InGaP/GaAs HBT process.The design frequency is 4G Band3 downlink band,and the application scenario is the end stage of 4G base station transmission link.The power amplifier adopts asymmetric Doherty structure,and the transmission line and power synthesis network are realized off-chip.The simulation results show that the bandwidth of the power amplifier is 1805-1880 MHz,and the saturation output power is35.3 dBm.At this power,the PAE is 32.4%.At the power back to 28 dBm,the PAE is22.6%,achieving a good power backoff efficiency.