| The 4th generation and 5th generation mobile communication systems employ highly spectral-efficient modulation,allowing higher transmission rates and greater signal bandwidth.However,high peak-to-average power ratio causes the power amplifier to operate at the deep power back-off region with poor efficiency.For 4G/5G communication,envelope tracking scheme is one of the effective techniques to enhance the efficiency of the power amplifier,among which the wideband,high-efficiency envelope tracking CMOS supply modualtor remains one of the most challenging aspects of the system.This thesis reviews the topologies and principles of the supply modualtor and presents two wideband,high-efficiency supply modulators for 4G/5G application.A hybrid envelope tracking modulator with a 3-level hysteresis-controlled buck converter in parallel with a 200MHz rail-to-rail class-AB linear amplifier is presented.And capacitor current integration sensor is embedded in the hysteresis-control loop to solve the current sensor problem.The supply modulator delivers the maximum output power of 0.9W,achieving a peak efficiency of 92%for LTE-20MHz application.The second design presents an ac-coupling supply modulator supporting the100MHz uplink signal for the 5G scenario.The ac-coupling capacitor splits the power between the linear amplifier and the switching regulator.The architecture proposes a concurrent dc offset regulation of the ac-coupling capacitor,which provides a level shift between the class-AB supply voltage and the PA supply.As such,the lower class-AB supply can be supported to decrease the power comsumption of the linear stage.Moreover,a slew-rate enhanced circuit predicting the slewing of the linear amplifier based on the slope of the envelope signal is presented to improve the tracking for the wideband envelope.The simulated results show the tracking of the NR-100MHz envelope with a93.7%peak efficiency,1.09W maximum output power,1.4V maximum output voltage range. |
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