| Linearity and efficiency are two important indicators for measuring RF power amplifiers(power amplifiers).The linearity of the RF power amplifier directly affects the communication quality of the wireless communication system.If the communication signal cannot be amplified linearly,it will lead to an increase in the communication error rate and affect the problems of adjacent channel communication.The efficiency of the RF power amplifier characterizes its DC conversion capability.If the conversion efficiency is low,the DC power consumption of the base station increases sharply and the heat is severe.At the same time,the base station needs more energy for the cooling of the equipment,which increases the energy consumption and greatly increases the operating cost of the operator.At the same time,in order to make full use of limited spectrum resources,various complex modulation methods such as QAM,QPSK,etc.are widely used in wireless communication systems,causing the signal PAPR(peak-to-average ratio)to rise sharply and the linearity to deteriorate severely.How to realize the design of a new transmitter structure that can take into account multiple performance indicators such as power amplifier efficiency and linearity is a difficult problem to be solved in green communication systems.Firstly this paper analyzes the basic working principles of traditional RF power amplifiers,high-efficiency switching power amplifiers,etc.,and summarizes the advantages and disadvantages of various power amplifiers in wireless communication systems.The advantages of digital power amplifier are suitable for future development trends of software radio such as high efficiency,high linearity,reconfigurable and miniaturization.Then this paper introduces the basic working principle of digital power amplifier and the research status of relevant fields at home and abroad in detail,and each circuit module of digital power amplifier circuit system including two-stage drive power amplifier circuit,last-stage switching power amplifier circuit,narrow-band bandpass filter,etc.was designed and optimizated..The joint modulation of the digital power amplifier circuit and the Sigma-delta digital modulator was achieved,and had a good joint modulation effect,which verifies the feasibility and excellent amplification effect of the digital power amplifier circuit.The joint modulation effect of Class-D and Class-E switching power amplifiers based on different semiconductor material transistor designs in digital power amplifier circuits is compared,which proves the advantages of Class-E switching power amplifiers designed based on third-generation semiconductor material transistors represented by GaN in design digital power amplifier circuits.Finally,for the problem of low coding efficiency of digital power amplifier circuits,based on existing technologies at home and abroad,the system coding efficiency has been improved by more than 6% by increasing the number of quantization levels of Sigma-delta modulators,compared with relevant research results at home and abroad have achieved good results. |
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