Design And Implementation Of Broadband High Efficiency Multilevel Supply Modulator

In recent years,the communications industry has developed rapidly,with 4G and 5G coming one after another.The transmitted signal bandwidth is wider and wider,and the peak-to-average power ratio of the signal is getting higher and higher.Due to the high value of the peak-to-average power ratio of the signal,the power amplifier works in the non-saturated state on the situation of output power back-off most of the time,which greatly reduces the efficiency of the power amplifier.The envelope tracking supply modulator system is a very effective means of solving the power amplifier's severe degradation in output power back-off.The main research of this thesis is a digital circuit-assisted envelope tracking supply modulator system.Firstly,its circuit structure and working principle are introduced.Then,two important components of the supply modulator and power amplifier are deeply studied and researched,and finally the entire system was tested and optimized.This thesis investigates and studies the types and principles of supply modulators,which is one of the two cores of ET system,and analyzes the advantages and disadvantages of different types of supply modulators.Subsequently,a discrete type of supply modulator is designed.The ripple phenomenon appearing in the supply modulator design process is analyzed and a solution is proposed.For different input signal types,an algorithm is designed to adjust the value of supply voltage to improve the efficiency of the overall supply modulator.In the finally test,the supply modulator can maintain an overall efficiency of up to 86.5%,at a switching rate of 20 MHz,the maximum output voltage is 32 V,the minimum output voltage is 8V,and the peak output power can reach 40 W,the average output power can reach 10 W.In addition,for the power amplifier which is another core of the ET system,this thesis deeply studies the process and method of designing the broadband high efficiency power amplifier,and analyzes the effects of the parasitic capacitance(non-linear capacitance)and the varying drain voltage in the design of the power amplifier.And the design were thus optimized during the process.In the end,Cree's CGH40010 F transistor is used to design a broadband high-efficiency continuous Class F power amplifier with a working frequency range of 3.2GHz-4.3GHz,a drain efficiency of about 70%,a gain of more than 10 dB,and an output power of 40 dBm or more.Finally,after studying the characteristic changes of the power amplifier under varying drain voltage,this thesis combines the supply modulator and the power amplifier,and optimizes the entire ET system.The entire ET system was verified under a simple test platform.The final test results showed that the ET system improved the efficiency of the power amplifier from 27.1% to31.5% under the input of 40 MHz LTE signal(PAPR value of 9.2),which verified ET can effectively improve the efficiency of the power amplifier with the broadband high PAPR value signal input.