Research On Switched-Capacitor Power Amplifier Based On AM-PM Distortion Self-Calibration Technique

With the increasing demand for higher data rate in wireless communication systems,it brings great challenges to radio frequency(RF)transmitter systems.Increasing modulation bandwidth and using higher-order modulation schemes can support higher data rate.While the spectrum is very crowded in RF band,high-order complex modulation schemes are more effective in increasing data rate.Meanwhile,the digital power amplifier(DPA)is benefited from the convenience of direct modulation architecture in supporting high-order modulation signals,which is attractive to researchers in the world.As a new type of power amplifier appeared in recent decades,DPA has the features of high integration,high efficiency,and low cost.It achieves direct modulation of the amplitude of the carrier frequency signal by controlling the number of amplifying units turned on.Each unit cell works in switching-mode,which has the advantage of high efficiency.However,changes in number of unit cells may lead to the variation in output impedance,resulting in non-linearity.Therefore,to deal with the non-linearity in DPA,this thesis proposes the on-chip self-calibration technique.By detecting the output phase distortion and generating complementary phase compensation in PM signals,the AM-PM distortion is decreased and the linearity is improved.At first,this thesis introduces the working theory of the proposed self-calibration technique and discusses the calibration process.Then,this thesis shows the principle of each component of self-calibration circuits and their schematic.Based on the proposed self-calibration circuits,a digital switched-capacitor power amplifier(SCPA)chip is designed.In this thesis,based on the proposed AM-PM distortion self-calibration technique,a digital SCPA is designed and fabricated in conventional 40 nm CMOS technology.In continuous wave test,this chip achieves peak output power of 28.9 d Bm,peak drain efficiency(DE)of 43.9%,peak power added efficiency(PAE)of 37.2%,and operation bandwidth of 1.4-2.8 GHz.At 1.8 GHz,the measured AM-PM distortion is only 4.4°,which can support complex modulation signals without pre-distortion.This chip supports64-/256-/1024-QAM modulation signals.In the test of 100 MHz 64-QAM and 10 MHz1024-QAM modulation signals,this chip achieves average output power of 22.6/21.3d Bm,average DE of 33.9%/32.1%,EVM of-26.3/-35.0 d B,and ACLR of-26.4/-33.7d Bc.