Research And Design Of A Rf Broadband Driver Amplifier

With the update and iteration of wireless communication standards,more and more frequency bands are planned and more and more modulation methods are also applied.In a multi-frequency and multi-mode communication system,using a broadband RF driver amplifier to meet the need of amplifying multiple band signal has become an effective solution to improve system integration.This thesis introduces the basic theory of RF amplifiers,including design fundamentals,performance metrics and basic working classes.The challenging points in the design of wideband driver amplifier are discussed.The characteristics,advantages and limitations of several commonly used wideband amplifiers topologies and design methods of wideband matching networks are analyzed and demonstrated.Combined with the research of amplifier design theory and broadband design method,a broadband high-gain driver amplifier using GaAs HBT process is designed.It works in the frequency band of 2.5?5 GHz,with a relative bandwidth of 66.7%,covering the N77,N78,N79 bands of the Fifth-Generation Mobile Communication Technology(5G)and the N41frequency band re-cultivated from the Fourth-Generation Communication Technology(4G).For obtaining sufficient gain,a two-stage cascaded structure is used.Due to the high linearity requirements of the application system,the first stage of the driver amplifier works in class A,and the second stage works in class AB.A collector-base negative feedback network is added to the transistor to provide good gain flatness.Combined with theory,a two-level LC and equal Q matching network is designed to meet the working bandwidth.In order to be easily tuned,the output matching network is implemented on the substrate.In addition,the input,interstage matching network and the first and second stage amplifyinig structures are implemented on the GaAs substrate.After optimizing the Co-simulation of layout electromagnetic simulation model,output matching equivalent parameter model and the active devices until reaching the design target,the tapeout was made.The test results show that the drive amplifier is absolutely stable in all frequencies.The input return loss(S₁₁)in the working frequency band is less than-8 dB,the output return loss(S₂₂)is less than-10 dB,and the small signal gain reaches a high gain of 29dB.Full-band saturation output power is greater than 26 dBm.The output power of 1 dB compression point is greater than 24 dBm.Power added efficiency is greater than 32%,and the output power of third-order intercept point is greater than 30.5 dBm.The ACPR at 15 dBm output power under LTE modulation signal test is less than-37 dBc.At the same time,aiming at the gain fluctuation of traditional adaptive bias with the increase of output power,an improved new linearized bias circuit is proposed,and the feasibility is verified by simulation in ADS.