Research And Design Of Key Circuit Of Low Power And High Slew Rate Envelope Tracking Supply Modulator

Power amplifier(PA)is a high energy consumption module circuit in mobile devices such as mobile phones.The improvement of efficiency is of great significance to reduce the heat dissipation of the equipments and prolong the battery life.In order to improve the data transmission rate in the limited spectrum resources,the modern mobile communication technology adopts the non constant envelope modulation mode with large peak to average power ratio(PAPR),which makes PA work in the power fallback zone for a long time.When the constant voltage power supply is used,the PA efficiency is low.Envelope tracking(ET)technology uses envelope tracking supply modulator(ETSM)to dynamically tune the supply voltage of PA to track the envelope of Radio-Frequency signal,which can effectively improve the efficiency of PA.ETSM is the core of ET technology,in order to achieve higher efficiency of ET system,ETSM itself should have higher efficiency;in addition,in order to amplify and track the input broadband envelope signal without distortion,ETSM needs to have higher bandwidth than Radio-Frequency input signal envelope and achieve higher slew rate.In this thesis,the key circuit of low power and high slew-rate ETSM is studied and designed.The primary content of this thesis is as follows:1.Based on TSMC 0.18μm CMOS process,a hybrid envelope tracking supply modulator(HETSM)topology composed of linear amplifier and switching converter in parallel is used to design a HETSM(Conventional)for 5MHz envelope signal.The linear stage is composed of traditional current mirror operational transconductance amplifier(OTA)and class AB output stage.The simulation results show that: when the power supply voltage is 3.3V and the load is 4Ω||100p F,the gain,gain bandwidth product,average slew-rate and quiescent current of the linear stage are 59.65 d B,25.38 MHz,75V/μs and17 m A respectively;when the 5MHz sinusoidal signal is input,the average output power,average efficiency and average amplification error of HETSM(Conventional)are28.25 d Bm,68.3% and 99.5m V respectively;however,when the 10 MHz sinusoidal signal is input,average output power and average efficiency are decrease to 28.18 d Bm and 66.83%respectively,and average amplification error increases to 154.8m V.This is because as the input signal bandwidth increases,the gain,bandwidth and slew-rate of the linear stage are insufficient,which makes it impossible to accurately amplify and track the input signal.The final input HSUPA R6 5MHz envelope signal has average output power of 27 d Bm and average efficiency of 69.5%.2.Based on TSMC 0.18μm CMOS process,a HETSM(Enhanced)for 10 MHz envelope signal is designed.In order to solve the problem that it is difficult for traditional current mirror OTA to achieve high gain,wide bandwidth and large slew-rate at the same time under the condition of low power consumption,a high performance OTA based on complementary flipped voltage follower(FVF)is proposed,by increasing the equivalent transconductance and transient current output,the gain,bandwidth and slew-rate are improved.Furthermore,while keeping the structure and parameters of other parts of HETSM(Conventional)unchanged,the traditional OTA is replaced by the complementary FVF OTA,that is,the proposed HETSM(Enhanced).The simulation results show that the gain,gain bandwidth product and average slew-rate of the linear stage are increased to73 d B,53 MHz and 191.45V/μs,respectively,and the quiescent current is reduced to 12 m A.When the 10 MHz sinusoidal signal is input,the average output power,average efficiency and average amplification error of HETSM(Enhanced)are 28.35 d Bm,68.14% and 58.8m V,respectively.Compared with the experimental results of the HETSM(Conventional)with10MHz sinusoidal signal input,the average output power and average efficiency are increased by 0.17 d Bm(27.25 m W)and 1.31%,respectively,and the average amplification error is reduced by 96 m V.The average output power and average efficiency of the final input LTE QPSK 10 MHz envelope signal are 28.39 d Bm and 73.24% respectively.